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Inclusion Body Myositis Research - what's new? 2006

A sample of MAJOR, selected articles from the medical literature for 2006.

Greek Letters Used: alpha: a, beta: b, gamma: g, delta: d


Dec
Neuromuscul Disord. 2006 Dec;16(12):839-44. Epub 2006 Oct 23.
AbPP-overexpression and proteasome inhibition increase aB-crystallin in cultured human muscle: relevance to inclusion-body myositis.
Wojcik S, Engel WK, McFerrin J, Paciello O, Askanas V.
USC Neuromuscular Center, Department of Neurology, University of Southern California Keck School of Medicine, Good Samaritan Hospital, Los Angeles, CA 90017-1912, USA.
Amyloid-b precursor protein (AbPP) and its fragment amyloid-b (Ab) are increased in s-IBM muscle fibers and appear to play an important role in the pathogenic cascade. aB-Crystallin (aBC) was shown immunohistochemically to be accumulated in s-IBM muscle fibers, but the stressor(s) influencing aBC accumulation was not identified. We now demonstrate, using our experimental IBM model based on genetic overexpression of AbPP into cultured normal human muscle fibers, that: (1) AbPP overexpression increased aBC 3.7-fold (p=0.025); (2) additional inhibition of proteasome with epoxomicin increased aBC 7-fold (p=0.002); and (3) aBC physically associated with AbPP and Ab oligomers. We also show that in biopsied s-IBM muscle fibers, aBC was similarly increased 3-fold (p=0.025) and physically associated with AbPP and Ab oligomers. We propose that increased AbPP is a stressor increasing aBC expression in s-IBM muscle fibers. Determining the consequences of aBC association with Ab oligomers could have clinical therapeutic relevance.


Dec
Exp Neurol. 2006 Dec 23; [Epub ahead of print]
Endoplasmic reticulum stress induces myostatin precursor protein and NF-kappaB in cultured human muscle fibers: Relevance to inclusion body myositis.
Nogalska A, Wojcik S, King Engel W, McFerrin J, Askanas V.
Department of Neurology, USC Neuromuscular Center, University of Southern California Keck School of Medicine, Good Samaritan Hospital, 637 S. Lucas Avenue, Los Angeles, CA 90017, USA.
Sporadic-inclusion body myositis (s-IBM) is the most common progressive muscle disease of older persons. It leads to pronounced muscle fiber atrophy and weakness, and there is no successful treatment. We have previously shown that myostatin precursor protein (MstnPP) and myostatin (Mstn) dimer are increased in biopsied s-IBM muscle fibers, and proposed that MstnPP/Mstn increase may contribute to muscle fiber atrophy and weakness in s-IBM patients. Mstn is known to be a negative regulator of muscle fiber mass. It is synthesized as MstnPP, which undergoes posttranslational processing in the muscle fiber to produce mature, active Mstn. To explore possible mechanisms involved in Mstn abnormalities in s-IBM, in the present study we utilized primary cultures of normal human muscle fibers and experimentally modified the intracellular micro-environment to induce endoplasmic-reticulum (ER)-stress, thereby mimicking an important aspect of the s-IBM muscle fiber milieu. ER stress was induced by treating well-differentiated cultured muscle fibers with either tunicamycin or thapsigargin, both well-established ER stress inducers. Our results indicate for the first time that the ER stress significantly increased MstnPP mRNA and protein. The results also suggest that in our system ER stress activates NF-kappaB, and we suggest that MstnPP increase occurred through the ER-stress-activated NF-kappaB. We therefore propose a novel mechanism leading to the Mstn increase in s-IBM. Accordingly, interfering with pathways inducing ER stress, NF-kappaB activation or its action on the MstnPP gene promoter might prevent Mstn increase and provide a new therapeutic approach for s-IBM and, possibly, for muscle atrophy in other neuromuscular diseases.


Dec
Muscle Nerve. 2006 Dec 1; [Epub ahead of print]
Myopathy associated with gluten sensitivity.
Hadjivassiliou M, Chattopadhyay AK, Grunewald RA, Jarratt JA, Kandler RH, Rao DG, Sanders DS, Wharton SB, Davies-Jones GA.
Department of Neurology, The Royal Hallamshire Hospital, Glossop Road, Sheffield S10 2JF, UK.
Ataxia and peripheral neuropathy are the most common neurological manifestations of gluten sensitivity. Myopathy is a less common and poorly characterized additional neurological manifestation of gluten sensitivity. We present our experience with 13 patients who presented with symptoms and signs suggestive of a myopathy and in whom investigation led to the diagnosis of gluten sensitivity. Three of these patients had a neuropathy with or without ataxia in addition to the myopathy. The mean age at onset of the myopathic symptoms was 54 years. Ten patients had neurophysiological evidence of myopathy. Inflammatory myopathy was the most common finding on neuropathological examination. One patient had basophilic rimmed vacuoles suggestive of inclusion-body myositis. Six patients received immunosuppressive treatment in addition to starting on a gluten-free diet; five improved and one remained unchanged. Among seven patients not on immunosuppressive treatment, four showed clinical improvement of the myopathy with a gluten-free diet. The improvement was also associated with reduction or normalization of serum creatine kinase level. The myopathy progressed in one patient who refused the gluten-free diet. Myopathy may be another manifestation of gluten sensitivity and is likely to have an immune-mediated pathogenesis. A gluten-free diet may be a useful therapeutic intervention. Muscle Nerve, 2006.


Dec
Joint Bone Spine. 2006 Dec;73(6):646-54. Epub 2006 Oct 10.
Contribution of autoantibodies to the diagnosis and nosology of inflammatory muscle disease.
Sordet C, Goetz J, Sibilia J.
Rheumatology Department and Immunology Laboratory, Strasbourg Teaching Hospital, Louis Pasteur University, EA 3432 Strasbourg, France.
The myositides are systemic autoimmune conditions of which the most important are polymyositis, dermatomyositis, and inclusion body myositis. In addition to the classic clinical diagnostic criteria, myositis-specific autoantibodies were identified about 15 years ago. Among the dozen or so myositis-specific autoantibodies reported to date, the most characteristic are directed against cytoplasmic antigens, such as tRNA synthetase (Jo-1 or PL-1, PL-7, PL-12, EJ, OJ, JS, and KS), signal-recognition particle (SRP), Mas, KJ, Fer (eEF1), and Wa. Antibodies to nuclear antigens include anti-Mi-2, anti-PMS (PMS1, and PMS2), and related antibodies (MLH1, DNA protein kinase catalytic subunit (DNA PKCS)...), and anti-56 kDa. Myositis-associated antibodies are not specific but may be found in patients with myositis. They are directed to nuclear or nucleolar antigens such as PM-Scl, Ku, RNP (U1-RNP and U2-RNP, U4/U6-RNP, and U5-RNP), Ro 52 kDa and, more rarely, Ro 60 kDa and La. Myositis-specific antibodies have proved useful on two fronts. They have improved the diagnosis of myositis by leading to the identification of characteristic clinical patterns, such as anti-synthetase syndrome. The place of autoantibodies alongside classic clinical and laboratory criteria remains to be determined, however. First, standardized assays will have to be developed to replace current detection methods, which use widely variable techniques and antigen preparations. Myositis-specific antibodies have also shed light on the pathogenesis of myositis. For instance, the development of antibodies to tRNA synthetases constitutes an original autoimmunity model that shows how muscle damage, probably of a nonspecific nature, can lead to the production of autoantibodies that perpetuate and aggravate the muscle lesions.


Dec
Arthritis Rheum. 2006 Dec 28;56(1):372-383 [Epub ahead of print]
Restricted T cell receptor BV gene usage in the lungs and muscles of patients with idiopathic inflammatory myopathies.
Englund P, Wahlstrom J, Fathi M, Rasmussen E, Grunewald J, Tornling G, Lundberg IE. Karolinska
University Hospital at Solna, and Karolinska Institutet, Stockholm, Sweden.
OBJECTIVE: To investigate T cell receptor (TCR) expression in 3 different compartments that could be involved in patients with myositis: muscle, lung, and peripheral blood. METHODS: Nine patients with polymyositis (PM), dermatomyositis, or inclusion body myositis underwent bronchoscopy and bronchoalveolar lavage (BAL) as well as muscle biopsy and blood sampling. A panel of 19 monoclonal antibodies specific for TCR V(beta) (BV) and V(alpha) (AV) were used to characterize the TCR profile in CD4+ and CD8+ T cell populations in BAL fluid and peripheral blood by flow cytometry. Muscle biopsy tissues were analyzed by immunohistochemistry. Patients were also typed for HLA-DRB1 and DRB3 alleles. RESULTS: A total of 17 T cell expansions were detected in BAL fluid, 6 in the CD4+ T cell population and 11 in the CD8+ T cell population. Four T cell expansions were detected in peripheral blood. A selective TCR V usage was found in muscle. Two PM patients, both of whom had BAL fluid BV3+ T cell expansions in the CD4 population and in whom BV3 was also a prominent TCR V segment in muscle tissue, shared the HLA-DRB1*03 allele. These 2 patients were the only ones who were positive for anti-Jo-1 antibody. CONCLUSION: We found a restricted accumulation of T lymphocytes expressing selected TCR V-gene segments in the target organ compartments (i.e., lung and muscle). The occurrence of shared TCR gene segment usage in muscle and lungs could suggest common target antigens in these organs.


Dec
Muscle Nerve 34: 775-778, 2006.
TEERIN LIEWLUCK, et al,
MUTATION ANALYSIS OF THE GNE GENE IN DISTAL MYOPATHY WITH RIMMED VACUOLES (DMRV) PATIENTS IN THAILAND
ABSTRACT: Distal myopathy with rimmed vacuoles (DMRV) is an early adult-onset, distal myopathy caused by a mutation of the UDP-N-acetylglucosamine 2 epimerase/N-acetylmannosamine kinase (GNE) gene. We herein report four Thai patients with DMRV who carried compound heterozygous mutations of the GNE gene including three novel (p.G89R, p.P511T, and p.I656N) and two known mutations (p.A524V and p.V696M). All patients shared p.V696M in one allele. Our study demonstrates the mutation spectrum of the GNE gene in Thai patients with DMRV.

DMRV is known to be the same disease as hereditary inclusion-body myopathy (HIBM), which was originally reported as quadriceps-sparing myopathy. DMRV/HIBM is caused by mutations in the GNE gene encoding UDP-N-acetylglucosamine 2 epimerase/ N-acetylmannosamine kinase, a bifunctional enzyme in the sialic acid synthetic pathway. Genetically confirmed cases of DMRV/HIBM have been found in Iranian Jews, Japanese, Koreans, Chinese, Americans, and Europeans. However, no case has been reported from Southeastern Asian countries, so far as we are aware. Herein, we report four unrelated Thai patients with DMRV confirmed both clinicopathologically and genetically.


Nov
Drug News Perspect. 2006 Nov;19(9):549-57.
Potential therapeutic targets for idiopathic inflammatory myopathies.
De Bleecker JL, Creus KK, De Paepe B.
Department of Neurology, Ghent University Hospital, Ghent, Belgium. jan.debleecker@Ugent.be.
The inflammatory myopathies essentially comprise three diseases with different immunopathologic features. Dermatomyositis (DM) is a complement-mediated microangiopathy. The immune response in polymyositis (PM) and sporadic inclusion body myositis (IBM) is a CD8+ T-cell-mediated cellular reaction against an unknown muscle fiber antigen. The multiple immune factors that guide inflammatory cell diapedesis and trafficking have been elucidated over the past two decades. Many of these molecules can now be targeted by monoclonal antibodies and other pharmacologic approaches. Randomized controlled trials are being started on a number of new agents to find out whether more specific immune interventions than the currently used glucocorticosteroids can treat DM and PM patients with fewer side effects, and may represent a first treatment modality for IBM, an entity unresponsive to all currently available pharmacological treatments.


Nov
Neuromuscul Disord. 2006 Nov;16(11):754-8. Epub 2006 Aug 28.
Familial inclusion body myositis in a mother and son with different ancestral MHC haplotypes.
Mastaglia F, Price P, Walters S, Fabian V, Miller J, Zilko P.
Centre for Neuromuscular and Neurological Disorders, University of Western Australia, 4th Floor, A Block, Queen Elizabeth II Medical Centre, Nedlands WA 6009, Australia.
Abstract: An Ashkenazi Jewish family in which the mother and a son both have inclusion body myositis (IBM) is reported. The condition developed at an earlier age and was more rapidly progressive and less responsive to treatment in the son than in the mother or other IBM patients in our clinic. Genetic analysis showed that the mother carried alleles of the 8.1 MHC ancestral haplotype (AH; HLA-B8, DRB1(*)0301), which is found in 85% of IBM patients in Western Australia. The son did not inherit this haplotype, but carried alleles characteristic of the 52.1AH (HLA-B5, DRB1(*)1502) of paternal origin. The findings indicate that in this family either the 8.1AH or 52.1AH may carry susceptibility for IBM and that the 52.1AH is associated with a more severe and treatment-resistant form of the disease.

Excerpts. Although inclusion body myositis is generally sporadic, it is rarely familial and has been reported in twins [1] and in a small number of families with an autosomal recessive pattern of inheritance [2]. A dominant pattern of transmission has also been reported in a three-generation family from Colorado [3], and also occurs in some forms of non-inflammatory hereditary inclusion body myopathy [4].

There is increasing evidence for the involvement of genetic susceptibility factors in sporadic IBM [5,6]. We demonstrated a strong association with the Class II HLA antigen DR3 [7] which was confirmed by other workers [2,8,9]. We subsequently showed that in Caucasians, alleles characteristic of either the 8.1 MHC ancestral haplotype (AH) (HLA-A1, B8, DRB1*0301) or the 35.2AH (HLA-A11, B35, DRB1*0101) may confer susceptibility independently [10]. When HLA-DR3-positive controls and sIBM patients were compared, carriage of HLA-DR3 without other components of the 8.1AH was less common in patients, suggesting HLA-DR3 per se is not the direct cause of disease. This is supported by the lack of any association between sIBM and the 18.2AH that also includes DRB1*0301 (HLA-A30, B18, DRB1*0301). We showed that the critical segment of the 35.2AH was marked by HLA-DR1 and the central MHC allele BTLII*2. The pattern was markedly different amongst Japanese sIBM patients, where there was a strong association with DRB1*1502 and the 52.1AH [11].

We report here the occurrence of familial inclusion body myositis in a mother and son of Ashkenazi Jewish origin with two different HLA ancestral haplotypes, the mother having the 8.1AH and the son the 52.1AH.

Discussion. The diagnosis of IBM was based on the pattern of muscle involvement clinically and on MRI [13], and was confirmed by the muscle biopsy findings in both cases. However there were differences in the clinical phenotype and severity of the pathological changes in the two patients. The rate of progression was more rapid in the son, and he showed less response to immunotherapy than his mother and has become more severely disabled. He has more severe involvement of the anterior tibial muscle groups resulting in bilateral footdrop, whereas the mother has more severe involvement of the neck flexors as well as mild facial weakness which is unusual in sIBM. These features of the son's disease are unusual amongst patients with sIBM in Western Australia in our experience, as is the high serum CK level. The biopsies from both cases showed widespread upregulation of MHC Class I and II antigens, invasion of muscle fibres by auto-aggressive T-cells and increased numbers of COX-negative fibres. Rimmed vacuoles and cytoplasmic eosinophilic inclusions were also present in both cases but were more numerous in the biopsy from the son.

We considered the possibility that the son may incidentally have another form of inclusion body myopathy, such as that associated with mutations in the GNE gene, as inflammatory changes have been reported in some cases of that condition [14]. However, we feel that this is unlikely as the clinical phenotype is not typical of that condition in which the quadriceps muscles are usually spared. Moreover, the overall combination of pathological changes in this case is more in keeping with inclusion body myositis, as is the response to IVIg administration which has been reported previously in some cases of sporadic IBM [15].

The occurrence of an inflammatory inclusion body myopathy phenotypically similar to sporadic IBM in two generations of the present family is open to a number of possible interpretations. The first is that the disease is due to a dominant mutation in an as yet unidentified gene. However, the possibility of a dominant mechanism of transmission cannot be proven given that there are only two affected individuals in two successive generations. An alternative explanation is that this is a pseudo-dominant pattern related to a shared genetic predisposition to develop sporadic IBM [6]. This conclusion is supported by our immunogenetic studies if one assumes that MHC haplotypes represent a necessary but not sufficient factor in the development of IBM (since the majority of carriers of the 8.1AH and 52.1AH do not develop IBM). It would then follow that the mother and son also share a second susceptibility factor on a different chromosome, not linked with the MHC. The possibility of an underlying genetic susceptibility to autoimmune disease also needs to be considered in view of the family history of myasthenia gravis and primary biliary cirrhosis.

The 8.1AH has been associated with various autoimmune diseases including sporadic IBM. Here the son lacked the maternal 8.1AH and inherited the 52.1AH from his father. The 52.1AH was not associated with sporadic IBM in a largely Anglo-Celtic cohort of West Australian cases [10], but has now been associated with sporadic IBM in a Japanese cohort [11]. Because inflammatory sporadic IBM is rare in Jewish populations (Argov, personal communication), it is not known which HLA haplotypes predispose to the condition in this ethnic group. Both HLA-DRB1*03 and HLA-DRB1*15 are known to be present in Ashkenazi populations but have a low frequency [16]. Indeed A1-B52-DRB1*15/16 has been described as a characteristic Jewish haplotype [17].

The immunogenetic findings in the present cases extend our previous observations [10] and confirm that susceptibility to IBM can be carried by three different MHC haplotypes: the 8.1AH, 35.2AH or 52.1AH. The findings also suggest that the phenotypic differences between the mother and son may reflect the effects of different underlying HLA susceptibility haplotypes, the 8.1AH being associated with a more benign and more treatment-responsive form of IBM than the 52.1AH. However we cannot exclude the possibility that these differences could also be due to the differential effects in the mother and son of some other disease-modifying gene. Further observations in larger cohorts of patients with sporadic IBM are required to confirm these conclusions and to determine whether the HLA haplotype influences the response to treatment in IBM.


October
FASEB J. 2006 Oct;20(12):2165-7. Epub 2006 Aug 29.
Transgenic expression of b-APP in fast-twitch skeletal muscle leads to calcium dyshomeostasis and IBM-like pathology.
Moussa CE, Fu Q, Kumar P, Shtifman A, Lopez JR, Allen PD, LaFerla F, Weinberg D, Magrane J, Aprahamian T, Walsh K, Rosen KM, Querfurth HW.
Department of Neurology, Caritas St. Elizabeth's Medical Center of Boston, Tufts University School of Medicine, 736 Cambridge St., Boston, MA, USA.
Intracellular deposition of the b-amyloid (Ab) peptide is an increasingly recognized pathological hallmark associated with neurodegeneration and muscle wasting in Alzheimer's disease (AD) and inclusion body myositis (IBM), respectively. Previous reports have implicated dysregulation of ba-amyloid precursor protein (betaAPP) expression in IBM. Accumulation of full-length bAPP, its various proteolytic derivatives including Ab, and phospho-tau into vacuolated inclusions is an early pathogenic event. We previously reported on a statistical tendency favoring fast twitch fiber involvement in IBM, reminiscent of the tissue specific patterns of misfolded protein deposition seen in neurodegenerative diseases. To test this principle, we generated an animal model in which human wild-type (WT) bAPP expression was limited to postnatal type II skeletal muscle. Hemizygous transgenic mice harboring increased levels of holo bAPP751 and Abeta in skeletal muscle fibers became significantly weaker with age compared with nontransgenic littermates and exhibited typical myopathic features. A subpopulation of dissociated muscle fibers from transgenic mice exhibited a 2-fold increase in resting calcium and membrane depolarization compared with nontransgenic littermates. Taken together, these data indicate that overexpression of human bAPP in fast twitch skeletal muscle of transgenic mice is sufficient for the development of some features characteristic of IBM, including abnormal tau histochemistry. The increase in resting calcium and depolarization are novel findings, suggesting both a mechanism for the weakness and an avenue for therapeutic intervention in IBM.


Sept
J Neurol (2006) 253 [Suppl 5]: V/64 V/65 DOI 10.1007/s00415-006-5010-2
Dieter Pongratz
Therapeutic options in autoimmune inflammatory myopathies (dermatomyositis, polymyositis, inclusion body myositis).
Abstract: Polymyositis, dermatomyositis, and inclusion body myositis are idiopathic inflammatory myopathies of unknown etiology with autoimmune pathogenesis. For choosing an individual and efficient therapy, diagnostic assignment is an important factor. Therapeutic options in dermatomyositis and polymyositis include corticosteroids and immunosuppressives. Intravenous immunoglobulins are only needed in special cases. In inclusion body myositis, corticosteroids and immunosuppressives are not successful. At the moment intravenous immunoglobulins are the only therapeutic possibility.
Excerpts: To study the hypothesis that bAPP gene expression, when confined to a specific muscle fiber type, can reproduce both the disease phenotype and defect in calcium homeostasis in vivo, we generated a transgenic mouse in which bAPP production is restricted to fasttwitch fibers through control by a myosin light chain (MLC) 1/3 promoter/enhancer. These mice develop myopathological and clinical features resembling those associated with IBM, including colocalization of immunoreactivities to bAPP and Ab-sequence-containing peptides, and ultrastructural and histopathological changes that indicate myodegeneration and skeletal muscle weakness. In addition, an alteration in muscle membrane potential and dysregulation of calcium homeostasis was discovered.


Sept
J Neurol. 2006 Sep;253(Supplement 5):v2-v8.
Epidemiology of neuroimmunological diseases.
Flachenecker P.
Neurological Rehabilitation Center "Quellenhof", Kuranlagenallee 2, 75323, Bad Wildbad, Germany, flachenecker@quellenhof.de.
This review gives an overview of various neuroimmunological diseases in terms of incidence and prevalence rates, age and sex distribution, and the frequency of subtypes, if applicable. The disorders selected for review are inflammatory muscle disorders (polymyositis, dermatomyositis and inclusion body myositis), myasthenia gravis, immune-mediated polyneuropathies (Guillain-Barre syndrome, chronic polyneuritis and vasculitic neuropathies), and multiple sclerosis.
Excerpt: The incidence of PM, DM and IBM is approximately 1:100,000 patients per year, with IBM being the most common form. In PM and DM, females are more commonly affected than males [2:1], whereas IBM occurs more often in males than in females [3:1]. The onset of the disease is age 18 or older in PM, has two peaks (5-15 and 45-65 years) in DM, and is 50 years or older in IBM. The prevalence of IBM has been estimated to be 4.9 per million population in the Netherlands, and 9.3 per million in western Australia which indicates that the prevalence of IBM is substantially higher than previously thought.


Published online before print October 31, 2006
Proc. Natl. Acad. Sci. USA, 10.1073/pnas.0603386103
PNAS | November 7, 2006 | vol. 103 | no. 45 | 16995-17000
MyoD expression restores defective myogenic differentiation of human mesoangioblasts from inclusion-body myositis muscle
Roberta Morosetti *, Massimiliano Mirabella *, Carla Gliubizzi *, Aldobrando Broccolini *, Luciana De Angelis ¶, Enrico Tagliafico ||, Maurilio Sampaolesi **, Teresa Gidaro *, Manuela Papacci *, Enrica Roncaglia ||, Sergio Rutella , Stefano Ferrari ||, Pietro Attilio Tonali *, Enzo Ricci *, and Giulio Cossu **
*Department of Neurosciences and Interdisciplinary Laboratory for Stem Cell Research and Cellular Therapy, Catholic University, Largo A. Gemelli 8, 00168 Rome, Italy; Fondazione Don Carlo Gnocchi, 00194 Rome, Italy; Institute of Cell Biology and Tissue Engineering, San Raffaele Biomedical Science Park, 00128 Rome, Italy; ¶Department of Histology and Embriology, University "La Sapienza," 00161 Rome, Italy; ||Department of Biomedical Sciences, University of Modena and Reggio Emilia, 41100 Modena, Italy; **Stem Cell Research Institute, San Raffaele Hospital, 20132 Milan, Italy; Institute of Hematology, Catholic University, 00168 Rome, Italy; and Department of Biology, University of Milan, 20133 Milan, Italy
Edited by Tullio Pozzan, University of Padua, Padua, Italy, and approved September 19, 2006 (received for review April 28, 2006)

The material in italics is a highly selective layman's translation and synopsis. See glossary below. Please refer to the original article for confirmation of the information presented here.

Point Summary
- The cause of IBM has not been discovered although much is already known about the changes that take place in the IBM muscle.
- IBM has two major aspects, one having to do with the immune system attacking and killing muscle cells, the other, a deterioration of the muscle cells' proteins.
- Efforts to use drugs to help reduce the immune system reaction have failed to improve IBM patients.
- Mesoangioblasts, vessel-associated stem cells, are able to differentiate into a variety of tissues including skeletal, cardiac and smooth muscle. Previous research has shown that when delivered into an artery, mesoangioblasts restore, to a significant extent, muscle structure and function in a mouse model of muscular dystrophy.
- This study describes the isolation and functional characterization of mesoangioblast cells obtained from the muscle biopsies of IM patients and shows that in IBM, mesoangioblasts fail to develop into skeletal muscle (myotubes).
- The growth and repair of muscle is normally controlled by a complicated series of steps involving a master gene called MyoD.
- A number of smaller genes control MyoD function and turn it on and off as required by the muscle, for example, as muscle is damaged, MyoD is turned on to replenish it.
- These researchers have discovered that MyoD is not functioning in the skeletal muscle (in the arms and legs) of IBM patients, thus muscle replenishment can not take place.
- Researchers discovered a small gene (BHLHB3) that turns off MyoD is overactive in IBM muscle and that once it becomes overactive it keeps turning itself on, perpetuating the inhibition of the MyoD and thus blocking mesoangioblasts from developing into skeletal muscle.
- The problem of reduced MyoD function in IBM can be addressed in two ways:
- First, through cell transplantation. The researchers obtained human muscle biopsy-derived IM mesoangioblasts (from DM and IBM) and treated them in the laboratory with a virus (an adenoviral vector) carrying with it the full-length mouse version of MyoD. In other words, the researchers took the genetic code for MyoD from mice and used the virus to put it into these IM mesoangioblast cells. Three types of cells were then transplanted into the muscles of special research mice, two using DM mesoangioblasts, two using untreated (wild) IBM mesoangioblasts and two using the treated (adenoMyoD-transduced) IBM mesoangioblasts. The IBM mesoangioblasts treated with the adeno-MyoD resulted in a significant improvement of muscle function when this group was compared with the group of muscles injected with wild-type (untreated) IBM cells. Thus, the introduction of MyoD overcomes the BHLHB3 inhibition. It also activates the MyoD that is already present in the cells, irreversibly making the cells generate new muscle. Ideally, future treatments will use mesoangioblast cells obtained from a patient, treated in the laboratory and injected back into the patient, restoring muscle production and thus avoiding any immune reactions to the injected cells.
- Second, the researchers examined the effect of using a genetic method to block the function of the BHLHB3 gene. The researchers used small interfering RNA (siRNA) created specifically to block the action of BHLHB3 mRNA in mesoangioblasts obtained from three IBM patients that were subsequently grown in the laboratory for seven days. The siRNA treated cells were able to differentiate into new muscle.
-Either knocking out this little inhibitory gene, or adding MyoD, would not "cure" the IBM, but it would partly compensate for IBM's effects by allowing the generation of new muscle fibers and thus improving muscle function.
- Until they can discover the root causes of IBM and address them directly, the goal is to either silence the overactive BHLHB3 gene or use this cell-based therapy to increase MyoD and thereby improve muscle function. In addition, this approach can be combined with future drugs aimed at addressing the faulty immune response that attacks muscle cells in the first place.

- Also, ultimately and ideally, taking mesoangioblasts and manipulating them in the laboratory with different mixtures of growth factors and biomolecules may greatly increase differentiation and increase their therapeutic efficacy, without requiring the added complexity of using genetic manipulation or viral infection.

Synopsis overview:
Inflammatory myopathies (IM) are acquired diseases of skeletal muscle comprising dermatomyositis (DM), polymyositis (PM), and inclusion-body myositis (IBM).

This research reports the isolation and characterization of mesoangioblasts, [ME - so - angie - OH - blasts] vessel-associated stem cells, obtained from the diagnostic muscle biopsies of patients with inflammatory myopathies (IM). Mesoangioblasts represent a distinct type of mesoderm progenitor cells that eventually develop (differentiate) into a variety of mesoderm tissues including skeletal, cardiac and smooth muscle. The number of mesoangioblast cells isolated, their rate of growth and lifespan, their marker expression, and their ability to differentiate into smooth muscle do not differ between mesoangioblasts from normal patients and IM mesoangioblasts. IBM mesoangioblasts show the same ability to divide that is observed in normal muscle suggesting that the disease has not reduced their proliferation potency. Nevertheless, although IBM mesoangioblasts can normally differentiate into smooth muscle cells (SMCs), their differentiation into skeletal muscle seems markedly impaired, because no skeletal myotubes are seen arising from IBM mesoangioblasts after labratory stimulation. Thus, mesoangioblasts isolated from IBM, fail to differentiate into skeletal myotubes (developing skeletal muscle fibers characterized by their tubular appearance).

IBM mesoangioblasts were found to express high levels of genes known to inhibit the generation of new muscle (myogenesis) such as TGFbeta-1, SFRP-2 (secreted frizzled-related protein 2), and BHLHB3 (basic helix-loop-helix domain containing class B3 transcription factor).

In IBM mesoangioblasts, BHLHB3, is highly over active and this in turn inhibits MyoD function, thus preventing the creation of new muscle (myogenesis). IBM mesoangioblasts did not give rise to differentiated myotubes and did not display any MyoD genetic activity (no MyoD mRNA), and MyoD could not be induced by the researcher's laboratory techniques.

The problem of reduced MyoD function in IBM can be addressed in two ways. First, through cell transplantation. Using a mouse model, the researchers treated [human] IBM mesoangioblasts in the laboratory with a virus (an adenoviral vector) carrying with it the full-length mouse MyoD. So, the researchers took the genetic code for MyoD from mice and used the virsus to put it into these IBM mesoangioblast cells. These treated cells were then transplanted into the muscle of special research mice, significantly restoring normal muscle function. This introduction of MyoD overcomes the BHLHB3 inhibition. It also activates the MyoD that is already present in the cells, irreversibly making the cells generate new muscle.

Second, the researchers examined the effect of using a genetic method to block out the function of the BHLHB3 gene. The IBM mesoangioblasts display increased levels of BHLHB3 messenger RNA (mRNA), the inhibitor of MyoD. Therefore, the researchers used small interfering RNA (siRNA) created specifically to block the action of BHLHB3 in mesoangioblasts from three IBM patients. The siRNA treated cells were able to differentiate into muscle, giving rise to muscle myotubes after 7 days.

Therefore, either by silencing the overactive BHLHB3 gene or by transplanting modified cells in order to over express MyoD, we should be able to restore muscle genesis in the IBM mesoangioblasts, opening the way for new cell-based therapeutic strategies to treat IBM.

Synopsis of Other Excerpts:

In IBM muscle, the presence of degenerative features, such as muscle fibers displaying vacuoles containing amyloid and amyloid-related proteins, reflects a complex breakdown involving misfolded and unfolded proteins and increased oxidative stress in the context of an "aged" cellular environment, also acting in concert with chronic inflammation.

Regeneration and repair of muscle fibers are fundamental processes accounting for rebuilding muscle structure and gradual recovery of muscle strength following injury or disease.

Satellite cell dependent regeneration also occurs in IBM muscle wherein the multiple metabolic pathways normally involved in muscle development are activated. However, in IBM, despite the activation of potentially repairing mechanisms, regeneration is inefficient.

Mesoangioblasts are vessel-associated stem cells, able to differentiate into a variety of tissues including skeletal, cardiac and smooth muscle. When delivered into an artery, mesoangioblasts restore, to a significant extent, muscle structure and function in a mouse model of muscular dystrophy. Because mesoangioblasts express numerous receptors for inflammatory cytokines, we assumed that the human counterpart of mouse mesoangioblasts should also be stimulated in high numbers during muscle inflammation.

Here, we describe the isolation and functional characterization of mesoangioblast cells obtained from the muscle biopsies of IM patients and show that IBM mesoangioblasts fail to differentiate into skeletal muscle. This blockage of differentiation can be corrected in the laboratory by the temporary expression of MyoD, making these cells potentially attractive candidates for cellular therapy of IBM.

IBM mesoangioblasts show the same ability to divide observed in normal muscle suggesting that the disease has not reduced their proliferation potency. Nevertheless, although they normally differentiate into smooth muscle cells (SMCs) their differentiation into skeletal muscle seems markedly impaired, because no myotubes were observed in IBM under the same labratory conditions that normally promote massive skeletal muscle differentiation of mesoangioblasts in cases of DM, PM and in controls.

Interestingly, cultures of satellite cell-derived progenitors (MyoD-positive) obtained from the same IBM biopsies show normal myogenic differentiation. These data agree with previous studies showing that in the laboratory, IBM muscle cells proliferate and differentiate normally and can be properly linked to the nerves, although there is a possibility that satellite cell activation could be defective in patients (in vivo).

This research shows that an ancestor cell, found in a small areas around the vessels (perivascular niche) of IBM muscle, is defective in the process leading to the generation of new muscle (myogenic determination and differentiation).

IBM displays an inadequate long-term regeneration of muscle despite a normal number of muscle satellite cells present and a failure of mesoangioblast cells to differentiate into muscle in the labratory. This defect can be corrected by temporary activation of MyoD expression (cell transplantation), a strategy that, independent from the underlying molecular mechanisms involved in [causing] the IBM disease, immediately offers a therapeutic opportunity to treat IBM affected muscle.

The creation of skeletal muscle is a complex, multi-step process mainly regulated by bHLH myogenic factors, that depends upon a finely controlled equilibrium between activators and inhibitors of bHLH.

IBM mesoangioblasts highly express the bHLH domain containing class B3 transcription factor (BHLHB3), which inhibits MyoD function.

BHLHB3 gene activity (expression) is regulated by multiple stimuli coming from outside of the cell, including cytokines and growth factors. It is likely that cytokines or other factors present in the IBM muscle environment induce BHLHB3 expression.

Our data demonstrate that reestablishing a correct balance between positive and negative bHLH factors, either by increasing MyoD through cell transplantation or by the siRNA inhibition of BHLHB3 expression, restores a normal muscle generation (myogenesis) in IBM mesoangioblasts.

BHLHB3 probably creates a self perpetuating loop - it transactivates its own promoter - thus maintaining its inhibitory effect on myogenesis, away from the microenvironment that initially induced its expression.

Whereas several genes may control muscle differentiation of mesoangioblasts, researchers identified BHLHB3 as one of the important mediators preventing new muscle growth in IBM. How much this defect is related to the cause of IBM remains to be investigated - one intriguing point is that the muscle satellite cells are not directly affected and yet IBM muscle fails to regenerate.

. . . .

Using mesoangioblast cells presents a distinct advantage over using satellite cells, making them an ideal candidate for muscle regeneration via cell transplantation. Their safety as a therapeutic tool is demonstrated by their limited lifespan, absence of chromosomal abnormalities and the absence of the creation of tumors in mice. Moreover, mesoangioblasts can be easily isolated with high efficiency even from frozen muscle material (stored biopsies) and expanded in the laboratory to the number of cells suitable for a potential treatment in patients. The use of frozen material is particularly relevant in IBM, because it makes it possible to go back to stored muscle to obtain mesoangioblasts.

An intrinsic myogenic defect of IBM mesoangioblasts can be corrected with viral transduction of MyoD in the laboratory that, by cell transplantation, overcomes BHLHB3 inhibition and, by activating MyoD in the patient, irreversibly commits cells to myogenesis.

Thus, laboratory manipulation of these cells taken from the patient (autologous cells) induced to effectively differentiate into skeletal muscle could be particularly valuable to promote muscle repair and regeneration in a disease such as IBM where relentless muscle involvement occurs very selectively. The characteristic early and severe atrophy of quadriceps, responsible for sudden falls and disabling gait impairment, could be treated by infusing mesoangioblasts with selective catheter delivery into the iliac arteries in the leg. The use of autologous cells eliminates the need of immune suppression. Eventually, more selective drugs may be combined with regenerative cell therapy, to address immune system irregularities, given the inflammatory background of IBM muscle.

End of the synopsis.

Abstract quoted from article:
Inflammatory myopathies (IM) are acquired diseases of skeletal muscle comprising dermatomyositis (DM), polymyositis (PM), and inclusion-body myositis (IBM). Immunosuppressive therapies, usually beneficial for DM and PM, are poorly effective in IBM. We report the isolation and characterization of mesoangioblasts, vessel-associated stem cells, from diagnostic muscle biopsies of IM. The number of cells isolated, proliferation rate and lifespan, markers expression, and ability to differentiate into smooth muscle do not differ among normal and IM mesoangioblasts. At variance with normal, DM and PM mesoangioblasts, cells isolated from IBM, fail to differentiate into skeletal myotubes. These data correlate with lack in connective tissue of IBM muscle of alkaline phosphatase (ALP)-positive cells, conversely dramatically increased in PM and DM. A myogenic inhibitory basic helix-loop-helix factor B3 is highly expressed in IBM mesoangioblasts. Indeed, silencing this gene or overexpressing MyoD rescues the myogenic defect of IBM mesoangioblasts, opening novel cell-based therapeutic strategies for this crippling disorder.

Excerpts quoted from article: The idiopathic inflammatory myopathies (IM), characterized by mononuclear cells infiltration of skeletal muscle, are the largest group of acquired muscle diseases and encompass three major forms: dermatomyositis (DM), polymyositis (PM), and inclusionbody myositis (IBM) (1). Causes of DM, PM, and IBM are unknown, but an autoimmune pathogenesis is supported by marked up-regulation of cytokines and adhesion molecules, evidence of a T cell-mediated myocytotoxicity in PM and IBM and of a complement- mediated microangiopathy in DM (2). Current immunotherapies are usually effective in DM and PM patients, whereas IBM, the most frequent myopathy in elderly patients, responds poorly or not at all to immunosuppressive therapies and its course steadily progresses to severe disability. In IBM muscle, the presence of degenerative features, such as vacuolated fibers containing amyloid and amyloid-related proteins (3), reflects a complex pathogenesis involving misfolded and unfolded proteins and increased oxidative stress in the context of a cellular -aged- milieu acting in concert with chronic inflammation (4). Regeneration and repair of muscle fibers are fundamental processes accounting for rebuilding muscle integrity and gradual recovery of muscle strength in IM after suppression of mononuclear cells infiltration. Satellite cell dependent regeneration occurs also in IBM muscle wherein multiple metabolic pathways normally involved in muscle development are activated (5, 6). However, in IBM, despite the activation of potentially repairing mechanisms, regeneration is inefficient. Mesoangioblasts are vessel-associated stem cells, firstly isolated from dorsal aorta of mouse embryos (7), able to differentiate into a variety of mesoderm tissues including skeletal, cardiac and smooth muscle (8, 9). When delivered intraarterially, mesoangioblasts restore to a significant extent muscle morphology and function in a mouse model of muscular dystrophy (10). Because mesoangioblasts express numerous receptors for inflammatory cytokines, we assumed that the human counterpart of murine mesoangioblasts should be recruited in high numbers during muscle inflammation. Here, we describe the isolation and functional characterization of pericyte-derived adult mesoangioblasts (herein simply called mesoangioblasts) from diagnostic muscle biopsies of IM patients and show that IBM mesoangioblasts fail to differentiate into skeletal muscle. This differentiation block can be corrected in vitro by transient expression of MyoD, making these cells potential attractive candidates for cellular therapy of this disabling disease.

Discussion quoted from article:
Our study demonstrates that human adult mesoangioblasts can be efficiently isolated from diagnostic muscle biopsies of patients with IM. Antigenic and molecular characterization of these cells indicated that mesoangioblasts represent a distinct type of mesoderm progenitor cells, different from mesenchymal stem cells (E.T., and S.F., unpublished observations). In all IM patients, these cells retain the same proliferation ability of cells isolated from normal muscle, and can be grown and expanded for as many as 25-30 passages, although not indefinitely. Here we have shown that exposure of DM and PM mesoangioblasts to normal SDMC-conditioned medium is greatly effective in inducing skeletal muscle differentiation, outlining the importance of muscle-secreted factors for myogenic maturation of these stem cells. IBM mesoangioblasts show the same proliferation ability observed in normal muscle suggesting that the disease has not reduced their proliferation potency. Nevertheless, although they normally differentiate into smooth muscle cells (SMCs), their differentiation into skeletal muscle seems markedly impaired, because no myotubes were observed under the same conditions that promote massive skeletal muscle differentiation of DM, PM and control mesoangioblasts. Interestingly, cultures of satellite cell-derived progenitors (MyoD-positive) obtained from the same IBM biopsies show normal myogenic differentiation. These data agree with previous studies showing that cultured IBM muscle cells proliferate and differentiate normally and can be properly innervated (23), although the possibility exists that satellite cells activation in vivo could be defective. However, we show here that a progenitor cell, resident in a perivascular niche of IBM muscle, is defective in myogenic determination and differentiation. No significant differences of age exist between our IBM and DM/PM patients, excluding a consequence of muscle aging and strongly suggesting a causal correlation with the specific pathophysiology of IBM. In fact, IBM presents an inadequate long-term regeneration despite a normal number of satellite cells, a complete lack in muscle connective tissue of ALP-positive cells, likely activated pericytes representing the cells from which mesoangioblasts are established in vitro, and a failure of mesoangioblasts to differentiate in vitro. This defect can be rescued by transient MyoD expression, a strategy that, independently from the underlying molecular mechanism, immediately offers a therapeutic opportunity. Skeletal myogenesis, a complex multistep process mainly regulated by bHLH myogenic factors, depends upon a finely controlled equilibrium with repressors bHLH such as Id (24). IBM mesoangioblasts highly express BHLHB3, which inhibits MyoD function (17). Our data demonstrate that reestablishing a correct balance between positive and negative bHLH factors, by MyoD transient transduction or siRNA inhibition of BHLHB3 expression, restores a normal myogenesis in IBM mesoangioblasts. As BHLHB3 gene expression is regulated in a cell-type specific manner by multiple extracellular stimuli including cytokines and growth factors, it is likely that cytokines or other factors present in the IBM muscle -milieu- but not in other IM muscle induce BHLHB3 expression. Like most bHLH, BHLHB3 probably transactivates its own promoter, thus maintaining its inhibitory effect on myogenesis also in vitro, away from the microenvironment that initially induced its expression. Whereas several genes may control muscle differentiation of mesoangioblasts, we identified BHLHB3 as one of the important mediators of myogenic block in IBM. How much this defect impacts on the pathogenesis of IBM remains to be investigated; it is however intriguing that satellite cells are not directly affected and yet IBM muscle fails to regenerate. . . . . Mesoangioblasts present a distinct advantage over satellite cells, i.e., the ability to cross the vessel wall which, together with easy isolation and good myogenic potential, make them an ideal candidate for muscle reconstitution therapy by means of cell transplantation. Their safety as therapeutic tool is demonstrated by limited lifespan, absence of kariotype abnormalities or tumorigenesis in nude mice (A. Dellavalle, M.S., R. Tonlorenzi, E.T., B. Sacchetti, L. Perani, B. G. Galvez, G. Messina, R.M., S. Li, G. Peretti, J. S. Chamberlain, W. E. Wright, Y. Torrente, S.F., P. Bianco, and G.C., unpublished data). Moreover mesoangioblasts can be easily isolated with high efficiency even from frozen material and expanded in vitro to number of cells suitable for a potential in vivo treatment. The use of frozen material is particularly relevant in IBM, often misdiagnosed as PM and suspected only after unsuccessful immunesuppressive therapy, because it makes possible to go back to stored muscle to expand mesoangioblasts. An intrinsic myogenic defect of IBM mesoangioblasts can be corrected with viral transduction of exogenous MyoD that overcomes BHLHB3 inhibition and, by activating endogenous MyoD, irreversibly commit cells to myogenesis. Thus, in vitro manipulation of these autologous cells induced to effectively differentiate into skeletal muscle (without a stable viral transduction as necessary in muscular dystrophies) could be particularly valuable to promote muscle repair and regeneration in a disease such as IBM where relentless muscle involvement occurs very selectively. The characteristic early and severe atrophy of quadriceps, responsible for sudden falls and disabling gait impairment, could be treated by infusing mesoangioblasts with selective catheter-mediated delivery into the iliac arteries. The use of autologous cells eliminates the obligatory need of immune suppression, although more selective anti-dysimmune drugs may eventually be combined with regenerative cell therapy, given the inflammatory background of IBM muscle. Also rare cases of unresponsive PM and DM would be potentially treatable as well by targeting muscle groups essentials for motor and respiratory functions. Complete article here.

Glossary:
= adenoviral vector: using an adeno virus to carry genetic material into cells.
= antigenic: relating to antigens.
= autoimmune pathogenesis: something that causes a malfunction (genesis of pathology) of the immune system.
= autologous cells: cells taken from the patient. The use of autologous cells eliminates the need of immune suppression as there are no rejection issues.
= basic helix-loop-helix domain containing class B3 transcription factor (BHLHB3): a gene discovered to inhibit the generation of new muscle (myogenesis).
= bHLH myogenic factors: factors that regulate the creation of skeletal muscle via a finely controlled equilibrium between activators and inhibitors of bHLH.
= cultures: growing cells in a laboratory using a nutritional medium.
= cytokines: proteins secreted by cells of the immune system that serve to regulate the immune system
= dermatomyositis (DM): A myositis characterized by weakness of limb and neck muscles and muscle pain and selling accompanied by skin rash affecting cheeks and eyelids and neck and chest and limbs; progression and severity vary among individuals. Problems with the capillaries are implicated.
= differentiate: the ability of cells to divide into other types of cells, for example, myoblast cells differentiate into muscle cells.
= endogenous: existing within an organism, from within.
= exogenous: existing outside of an organism, from outside.
= ex vivo: Refers to a medical procedure in which an organ, cells, or tissue are taken from a living body for a treatment or procedure, and then returned to the living body.
= expressed: active, activated.
= extracellular: outside of the cell.
= immunosuppressive therapies; treatments designed to suppress the immune system and its normal reactions, for example to reduce the effects of inflammation. Used in transplantation of organs and to treat autoimmune disorders.
= in vitro: in the laboratory.
= in vivo: in the living organism.
= inflammatory cytokines: proteins associated with inflammation.
= inflammatory myopathies (IM): include dermatomyositis, polymyositis and inclusion body myositis.
= innervated: serviced by a nerve.
= intrarterially: into an artery.
= kariotype [karyotype] abnormalities: abnormalities of the chromosomal makeup of a somatic cell in an individual or species (including the number and arrangement and size and structure of the chromosomes).
= mesoangioblasts: [ME - so - angie - OH - blasts] vessel-associated stem cells. Mesoangioblasts represent a distinct type of mesoderm progenitor cells that are able to develop (differentiate) into a variety of mesoderm tissues including skeletal, cardiac and smooth muscle.
= mesoderm: the layer of early (embryonic) cells that eventually develops into muscle, bone, cartilage, blood and connective tissues.
= mesoderm progenitor cells: cells that eventually differentiate into mesoderm derived tissues, for example, into muscle, bone, cartilage, blood and connective tissues
= messenger RNA (mRNA), the intermediate step between the DNA genetic code and the protein product.
= murine: mouse.
= muscle morphology: muscle structure.
= myocytotoxicity: anything that is toxic to muscle cells (myo=muscle, cyto=cells)
= MyoD: stands for myogenic determination. MyoD is one of the master regulatory genes involved in the formation of muscle cells. It is normally only active in myoblasts and skeletal muscle cells. The MyoD gene creates (codes for) the MyoD protein which then switches on the activity of many muscle specific genes.
= myogenesis: the creation of new muscle.
= myogenic block: something blocking the development of new muscle.
= myogenic differentiation: the differentiation of cells into muscle tissue.
= nude mice: Strains of mice which are largely hairless and lack all or most of the T-cell population. They show no rejection of genetic material transplanted from either other mice or from other species.
= pericyte: cells associated with the walls of small blood vessels.
= perivascular niche: small areas around the blood vessels.
= progenitor cells: early ancestors of cells that eventually go on to differentiate (develop) into other types of cells.
= proliferation: the ability to divide and proliferate.
= satellite cells: one of the early muscle progenitor cells that lead to muscle generation.
= SDMC: satellite derived myogenic cells -- cells that contribute to the generation of muscle that are derived from muscle satellite cells.
= silence: to block out.
= skeletal myotubes: developing skeletal muscle fibers characterized by their tubular appearance.
= small interfering RNA (siRNA): short pieces of RNA that correspond to the gene code you want to silence (block out) and that are introduced into the organism.
= smooth muscle cells (SMCs).
= transactivates its own promoter: turns on its own promoter leading to its ongoing creation.
= transduced / transduction: moving genetic material from one cell to another.
= tumorigenesis: the creation of tumors.
= vector: a vehicle used to transfer something, a virus is a common vector used to transport genetic material into the cell.
= viral transduction: using a virus to transfer genetic material from one cell to another.

picture

Since the discovery of genes, scientists have been interested in turning them off to understand their function or to treat genetic defects and sicknesses. A new procedure which uses short interfering RNAs will soon be able to perform this on any gene. The new method is a very effective way of studying the functions of human genes. This is of great interest because although the totality of genes is known from the sequencing of the human genome, the function of the genes remains largely uninvestigated. The method may also eliminate specific genetic defects on a long-term basis and may also prove to be extremely interesting for therapeutic purposes. From: http://www.garching-innovation.de/en/firmenprofil/techno/home_sirna.html (defunct)


October
Neuromuscul Disord. 2006 Oct 20; [Epub ahead of print]
AbPP-overexpression and proteasome inhibition increase aB-crystallin in cultured human muscle: Relevance to inclusion-body myositis.
Wojcik S, Engel WK, McFerrin J, Paciello O, Askanas V.
USC Neuromuscular Center, Department of Neurology, University of Southern California Keck School of Medicine, Good Samaritan Hospital, Los Angeles, CA 90017-1912, USA.
Amyloid-b precursor protein (AbPP) and its fragment amyloid-b(Ab) are increased in s-IBM muscle fibers and appear to play an important role in the pathogenic cascade. aB-Crystallin (aBC) was shown immunohistochemically to be accumulated in s-IBM muscle fibers, but the stressor(s) influencing aBC accumulation was not identified. We now demonstrate, using our experimental IBM model based on genetic overexpression of AbPP into cultured normal human muscle fibers, that: (1) AbPP overexpression increased aBC 3.7-fold (p=0.025); (2) additional inhibition of proteasome with epoxomicin increased aBC 7-fold (p=0.002); and (3) aBC physically associated with AbPP and Ab oligomers. We also show that in biopsied s-IBM muscle fibers, aBC was similarly increased 3-fold (p=0.025) and physically associated with AbPP and Ab oligomers. We propose that increased AbPP is a stressor increasing aBC expression in s-IBM muscle fibers. Determining the consequences of aBC association with Ab oligomers could have clinical therapeutic relevance.


September
J Neurol. 2006 Sep;253(Supplement 5):v2-v8. Links
Epidemiology of neuroimmunological diseases.
Flachenecker P.
Excerpt: The idiopathic inflammatory myopathies comprise three major subsets: polymyositis (PM), dermatomyositis (DM), and inclusion body myositis (IBM) [8]. The hallmark of these disorders is a progressive muscle weakness, with retained reflexes and without sensory disturbances.Muscle pain occurs in approximately 50% of patients and is more common in DM than in PM or IBM. Weakness of the diaphragm resulting in respiratory dysfunction is probably an underestimated manifestation of inflammatory myopathies [50].Both PM and DM are characterized by proximal muscle weakness. Whereas DM is easily recognized due to the skin rashes that are DM specific and occur early in the course of the disease (heliotropic erythema, Gottron's sign and Keinig's sign), the diagnosis of PM remains a challenge. Most of the patients erroneously diagnosed as PM were eventually found to suffer from IBM,dystrophic, toxic or metabolic myopathies [8]. Moreover, among 165 patients with inflammatory myopathies, nine had been diagnosed with PM, 65 with unspecified myositis, and 32 with possible myositis; after a follow-up period of 6.5 years, five out of the nine patients initially diagnosed as PM were given a final diagnosis of IBM [52] indicating that PM is uncommon and that the newly described diagnostic criteria need to be adopted. In IBM, weakness and wasting are most profound in knee extensors, hip flexors, and long finger flexors [38]. Swallowing difficulties are present in about 50% of patients, and subacute respiratory failure requiring mechanical ventilation was recently reported in one patient with IBM [56]. The incidence of PM, DM and IBM is approximately 1:100,000 patients per year, with IBM being the most common form [9]. In PM and DM, females are more commonly affected than males [2:1], whereas IBM occurs more often in males than in females [3:1]. The onset of the disease is age 18 or older in PM, has two peaks (5-15 and 45-65 years) in DM, and is 50 years or older in IBM.The prevalence of IBM has been estimated to be 4.9 per million population in the Netherlands [3], and 9.3 per million in western Australia which indicates that the prevalence of IBM is substantially higher than previously thought[41]. This disorder has attracted much interest not only because it is the most common acquired muscle disease in adults, but also because it combines features of inflammation and vacuolar degeneration with accumulation of pathological proteins similar to those changes seen in Alzheimer's disease, although the etiology remains unclear [38].


September
J Neurol. 2006 Sep;253(Supplement 5):v64-v65.
Therapeutic options in autoimmune inflammatory myopathies (dermatomyositis, polymyositis, inclusion body myositis).
Pongratz D.
Friedrich-Baur-Institut, Medizinischen Fakultat, Neurologischen Klinik und Poliklinik, Ludwig Maximilians Universitat Munchen, Ziemssenstrasse 1, 80336, Munchen, Germany.
Polymyositis, dermatomyositis, and inclusion body myositis are idiopathic inflammatory myopathies of unknown etiology with autoimmune pathogenesis. For choosing an individual and efficient therapy, diagnostic assignment is an important factor. Therapeutic options in dermatomyositis and polymyositis include corticosteroids and immunosuppressives. Intravenous immunoglobulins are only needed in special cases. In inclusion body myositis, corticosteroids and immunosuppressives are not successful. At the moment intravenous immunoglobulins are the only therapeutic possibility.


September
Muscle Nerve. 2006 Sep 12;
Myeloid dendritic cells in inclusion-body myositis and polymyositis.
Greenberg SA, Pinkus GS, Amato AA, Pinkus JL.
Department of Neurology, Division of Neuromuscular Disease, Brigham and Women's Hospital, 75 Francis Street, and Harvard Medical School, Boston, Massachusetts 02115, USA.
Dendritic cells (DCs), immune system cells central to the development of immunity, have not previously been reported in muscle in inclusion-body myositis (IBM). We performed immunohistochemical studies on muscle biopsy specimens from 50 patients using monoclonal antibodies that distinguish two classes of DCs, myeloid DC and plasmacytoid DC. In 17 of 20 IBM and 9 of 10 polymyositis (PM) specimens, myeloid DCs were present in substantial numbers, frequently surrounded and sometimes invading otherwise intact myofibers, and were part of dense collections of cells that included T cells. Dermatomyositis muscle had more plasmacytoid DCs than myeloid DCs, whereas IBM and PM had greater numbers of myeloid DCs. The stellate morphology of myeloid DCs in dense collections of cells that included T cells suggests local intramuscular antigen presentation in IBM and PM.


September

Natural Protective Mechanism Against Neuronal Death In Alzheimer's Found Researchers have uncovered what appears to be a natural protective mechanism against a central cause of neuronal death in Alzheimer's and similar neurodegenerative diseases. They theorize that it may be possible to use drugs to enhance that mechanism, to alleviate Alzheimer's pathology.

George Jackson, Daniel Geschwind, and their colleagues described their findings in the September 7, 2006, issue of the journal Neuron, published by Cell Press. Basically, in studies with mice, flies, and brain tissue from human patients, they discovered that the enzyme puromycin-sensitive aminopeptidase (PSA) snips apart the abnormal tangles of protein called tau that are associated with cognitive decline and neurodegeneration in Alzheimer's and similar "tauopathy" diseases. Significantly, they found higher levels of PSA gene expression in the cerebellum than in the cortex of patients with such diseases. The former region is known to be more resistant to neurodegeneration in such diseases than the latter. Tau causes neurodegeneration when a mutant form of the protein forms "neurofibrillary tangles" in brain cells, ultimately killing them. In their experiments, Jackson, Geschwind, and their colleagues first used DNA microarrays--so-called "gene chips"--to find genes that were more activated in certain brain regions than others, in mice engineered to have a mutant form of human tau that causes neurodegeneration. Such microarrays enable researchers to determine the activity of thousands of genes at once. The gene for PSA was among those they identified as more active in the resistant cerebellum. In studies with the fruit fly Drosophila, they found that higher activity of the PSA gene--and loss of its function--enhanced neurodegeneration. And in test tube studies, they found that PSA does directly act on tau to snip it apart for degradation by the cell. They next compared levels of PSA gene expression in samples of brain tissue from the cortex and cerebellum of both normal humans and those with fibrillary tangle disorders. In both types of samples, they found a 5-fold elevation of PSA in the cerebellum as compared to the cortex. The researchers concluded that their work not only reveals a significant protective factor in fibrillary tangle disorders, but points the way for further searches of other such factors. They wrote that "This work provides a clear proof of principle for validation of genetic screens using model systems and allows us to more firmly establish a functional role for one of the identified genes, Psa. Although Psa was known to be highly brain enriched, to our knowledge, its role vis-a-vis tau degradation or modification of tau-induced neurodegeneration has not been characterized previously. "Data derived from in vivo studies with animal models and a cell-free system suggest that PSA may play a pivotal role in protection from tau-induced neurodegeneration, most likely by direct cleavage of tau," they wrote. The researchers cited studies from other laboratories showing that turning off the mutant, pathological form of tau in mice after the mice showed neuronal pathology can reverse neurodegeneration. "Thus, it is tempting to speculate that factors that act to modulate tau levels or splicing, such as PSA, are candidates for playing a causal or contributory role in disease and may represent potential targets for development of therapeutics," concluded Jackson, Geschwind, and their colleagues.
The researchers include Stanislav L. Karsten, Tzu-Kang Sang, Lauren T. Gehman, Shreyasi Chatterjee, Jiankai Liu, George M. Lawless, Justine Pomakian, Martina Wiedau-Pazos, Harry V. Vinters, Daniel H. Geschwind, and George R. Jackson of the David Geffen School of Medicine at UCLA in Los Angeles, CA; Soma Sengupta, Robert W. Berry, and Lester I. Binder of the Feinberg School of Medicine at Northwestern University in Chicago, IL; Hyun S. Oh of Kyungwon University in Sungnam, South Korea; Cordula Schulz of Cold Spring Harbor Laboratories in Cold Spring Harbor, NY; Koon-Sea Hui of New York University School of Medicine in New York, NY. This work was supported by NS046489 (G.R.J.) and AG016570 (G.R.J., J.P., and H.V.V.), AG026938 (D.H.G.), and AG14453 (L.I.B.). M.W.-P. and S.L.K. were supported by the French Foundation for Alzheimer's Disease Research.


August
FASEB J. 2006 Aug 29; [Epub ahead of print]
Transgenic expression of {b}-APP in fast-twitch skeletal muscle leads to calcium dyshomeostasis and IBM-like pathology.
Moussa CE, Fu Q, Kumar P, Shtifman A, Lopez JR, Allen PD, Laferla F, Weinberg D, Magrane J, Aprahamian T, Walsh K, Rosen KM, Querfurth HW.
*Department of Neurology, Caritas St. Elizabeth's Medical Center, Tufts University School of Medicine, Boston, Massachusetts, USA;Department of Neurobiology and Behaviour, University of California, Irvine, California, USA;Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, Massachusetts, USA; andDepartment of Anaesthesia, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA.
Intracellular deposition of the b-amyloid (Ab) peptide is an increasingly recognized pathological hallmark associated with neurodegeneration and muscle wasting in Alzheimer's disease (AD) and inclusion body myositis (IBM), respectively. Previous reports have implicated dysregulation of b-amyloid precursor protein (bAPP) expression in IBM. Accumulation of full-length bAPP, its various proteolytic derivatives including Ab, and phospho-tau into vacuolated inclusions is an early pathogenic event. We previously reported on a statistical tendency favoring fast twitch fiber involvement in IBM, reminiscent of the tissue specific patterns of misfolded protein deposition seen in neurodegenerative diseases. To test this principle, we generated an animal model in which human wild-type (WT) bAPP expression was limited to postnatal type II skeletal muscle. Hemizygous transgenic mice harboring increased levels of holobAPP751 and Ab in skeletal muscle fibers became significantly weaker with age compared with nontransgenic littermates and exhibited typical myopathic features. A subpopulation of dissociated muscle fibers from transgenic mice exhibited a 2-fold increase in resting calcium and membrane depolarization compared with nontransgenic littermates. Taken together, these data indicate that overexpression of human bAPP in fast twitch skeletal muscle of transgenic mice is sufficient for the development of some features characteristic of IBM, including abnormal tau histochemistry. The increase in resting calcium and depolarization are novel findings, suggesting both a mechanism for the weakness and an avenue for therapeutic intervention in IBM.


August
Neuromuscul Disord. 2006 Aug 24; [Epub ahead of print]
Familial inclusion body myositis in a mother and son with different ancestral MHC haplotypes.
Mastaglia F, Price P, Walters S, Fabian V, Miller J, Zilko P.
Centre for Neuromuscular and Neurological Disorders, University of Western Australia, 4th Floor, A Block, Queen Elizabeth II Medical Centre, Nedlands WA 6009, Australia.
An Ashkenazi Jewish family in which the mother and a son both have inclusion body myositis (IBM) is reported. The condition developed at an earlier age and was more rapidly progressive and less responsive to treatment in the son than in the mother or other IBM patients in our clinic. Genetic analysis showed that the mother carried alleles of the 8.1 MHC ancestral haplotype (AH; HLA-B8, DRB1(*)0301), which is found in 85% of IBM patients in Western Australia. The son did not inherit this haplotype, but carried alleles characteristic of the 52.1AH (HLA-B5, DRB1(*)1502) of paternal origin. The findings indicate that in this family either the 8.1AH or 52.1AH may carry susceptibility for IBM and that the 52.1AH is associated with a more severe and treatment-resistant form of the disease.


August
J Neuropathol Exp Neurol. 2006 Aug;65(8):826-33.
Proteomic analysis of inclusion body myositis.
Li J, Yin C, Okamoto H, Jaffe H, Oldfield EH, Zhuang Z, Vortmeyer AO, Rushing EJ.
Surgical Neurology Branch, National Institutes of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, Maryland, USA.
Sporadic inclusion body myositis (IBM) is the most frequently acquired inflammatory myopathy of late adult life, yet its diagnostic criteria and pathogenesis remain poorly defined. Because effective treatment is lacking, research efforts have intensified to identify specific markers for this debilitating disorder. In this study, proteomic analysis of 4 cases of sporadic IBM was compared with 5 cases of inflammatory myopathy without clinicopathologic features of IBM to distinguish the IBM-specific proteome. Proteins were separated by 2-dimensional polyacrylamide gel electrophoresis and profiled by mass spectrometric sequencing. Expression of most proteins remained unchanged; however, 16 proteins were upregulated and 6 proteins were downregulated in IBM compared with cases of non-IBM inflammatory myopathy. These IBM-specific proteins included apolipoprotein A-I, amyloid b precursor protein, and transthyretin, which have been associated with amyloidosis; superoxide dismutase, enolase, and various molecular chaperones indicate perturbations in detoxification, energy metabolism, and protein folding, respectively. The IBM-downregulated proteins mainly serve as carriers for muscle contraction and other normal muscle functions. We further applied Western blot and immunohistochemistry to verify the proteomic findings. This study validates proteomics as a powerful tool in the study of muscle disease and indicates a unique pattern of protein expression in IBM.


August
Neuromuscul Disord. 2006 Aug 18; [Epub ahead of print]
Raised troponin T in inclusion body myositis is common and serum levels are persistent over time.
Lindberg C, Klintberg L, Oldfors A.
Neuromuscular Centre, Department of Neurology, Sahlgrenska University Hospital, Sweden.
Cardiac Troponin T (cTnT), creatine kinase (CK) and creatine kinase isoenzyme MB (CKMB) were measured in 42 consecutive patients with sporadic inclusion body myositis (s-IBM). 26 patients (62%) had a cTnT level >0.05mug/L, the cut off used in the diagnosis of myocardial infarction. The cTnT levels correlated somewhat more closely to CKMB (rho=0.83, p<0.0001) than to CK (rho=0.60, p<0.0001). Patients on immunosuppressive treatment had lower cTnT levels than untreated, while there were no significant differences according to age, disease duration or gender. Repeated samples in 26 patients showed that the cTnT levels were essentially unchanged over time up to 17 months. None of the patients had signs of myocardial damage or renal failure at time of sampling. It may be of value to analyse cTnT at some occasion(s) in s-IBM patients.


August
NATURE CLINICAL PRACTICE NEUROLOGY AUGUST 2006 VOL 2 NO 8 437-447.
Sporadic inclusion body myositis diagnosis, pathogenesis and therapeutic strategies
Marinos C Dalakas
Summary: Sporadic inclusion body myositis (sIBM) presents with a characteristic clinical phenotype of slow-onset weakness and atrophy, affecting proximal and distal limb muscles and facial and pharyngeal muscles. Histologically, sIBM is characterized by chronic myopathic features, lymphocytic infiltrates invading non-vacuolated fibers, vacuolar degeneration, and accumulation of amyloid-related proteins. The cause of sIBM is unclear, but two processes one autoimmune and the other degenerative appear to occur in parallel. In contrast to dystrophies, in sIBM the autoinvasive CD8+ T cells are cytotoxic and antigen-driven, invading muscle fibers expressing major histocompatibility complex class I antigen and costimulatory molecules. The concurrent degenerative features include vacuolization, filamentous inclusions and intracellular accumulations of amyloid-b-related molecules. Although viruses have not been amplified from the muscle fibers, at least 12 cases of sIBM have been seen in association with retroviral infections, indicating that a chronic persistent viral infection might be a potential triggering factor. Emerging data imply that continuous upregulation of cytokines and major histocompatibility complex class I on the muscle fibers causes an endoplasmic reticulum stress response, resulting in intracellular accumulation of misfolded glycoproteins and activation of the transcription factor NFkB, leading to further cytokine activation. In spite of the brisk, antigen-driven T-cell infiltrates, sIBM does not respond to immunotherapies. New therapies using monoclonal antibodies against lymphocyte signaling pathways might prove helpful in arresting disease progression.
PDF of this important new review article.


August
J Rheumatol. 2006 Aug;33(8):1623-1630.
Platelet-Endothelial Cell Adhesion Molecule-1 and CD146: Soluble Levels and in Situ Expression of Cellular Adhesion Molecules Implicated in the Cohesion of Endothelial Cells in Idiopathic Inflammatory Myopathies.
Figarella-Branger D, Schleinitz N, Boutiere-Albanese B, Camoin L, Bardin N, Guis S, Pouget J, Cognet C, Pellissier JF, Dignat-George F.
From the Laboratoire de Biopathologie de l'Adhesion et de la Signalisation-EA 3281, Faculte de Medecine Timone, Universite de la Mediterranee, Service d'Anatomie Pathologique et de Neuropathologie, Hopital de la Timone; Service de Medecine Interne, Hopital de la Conception; Laboratoire d'Hematologie et d'Immunologie, INSERM EMI 0019, Faculte de Pharmacie Timone, Universite de la Mediterranee; Service de Rhumatologie, Hopital de la Conception; and Service des Maladies Neuromusculaires, Hopital de la Timone, Marseille, France.
OBJECTIVE: Idiopathic inflammatory myopathies (IIM) are a heterogeneous group of diseases characterized by chronic inflammation of muscles. We investigated the role of cellular adhesion molecules implicated in the cohesion of endothelial cells in IIM. METHODS: In 22 patients with IIM we investigated plasma concentrations of soluble junctional adhesion molecules [platelet-endothelial cell adhesion molecule (sPECAM-1) and sCD146] and cellular adhesion molecules [sP-selectin, sE-selectin, intercellular adhesion molecule (sICAM-1), and vascular cell adhesion molecule (sVCAM-1)] implicated in leukocyte/endothelial cell interactions. Results were compared to a control group. Muscle biopsy samples from 8 out of 22 IIM patients were studied by immunohistochemistry for tissue expression of these molecules and compared to normal muscle samples. PECAM-1 and CD146 expression was also studied using immunoblots from muscle biopsies from 5 patients and 2 controls. RESULTS: We observed distinct patterns of soluble levels and in situ expression between dermatomyositis (DM), polymyositis (PM), and sporadic inclusion body myositis (s-IBM). PM samples showed significantly increased levels of sCD146, sPECAM-1, and s-ICAM1 and increased expression of CD146, CD31, and ICAM-1 in endothelial cells, whereas CD146 and ICAM-1 were also recorded in some muscle fibers. In DM, sE-selectin, sP-selectin, and sPECAM-1 were significantly increased, with abnormal expression of ICAM-1 in endothelial cells and perifascicular muscle fibers. In the small group of s-IBM samples, results were similar to PM, but the only significant increase was the level of sPECAM-1. Immunoblots confirmed increased expression of PECAM-1 and CD146 in all IIM muscles in comparison to controls, with the highest expression in PM and IBM samples. CONCLUSION: We observed abnormal increases of soluble levels of adhesion molecules implicated in endothelial cell junctions in PM (sCD146, sPECAM-1) and to a lesser extent in DM and s-IBM (sPECAM-1). We conclude that the distinctly different profiles between PM/s-IBM and DM reflect differences in the pathophysiological background of these diseases.


August
Acta Neuropathol (Berl). 2006 Aug;112(2):185-93. Epub 2006 Jun 21.
Rimmed vacuoles with b-amyloid and tau protein deposits in the muscle of children with hereditary myopathy.
Fidzianska A, Glinka Z.
Neuromuscular Unit MRC, Polish Academy of Science, Pawinskiego 5, 02-106, Warsaw, Poland, neurmyol@cmdik.pan.pl.
We investigated whether b-amyloid and tau protein are involved in the formation of inclusion body myositis (IBM)-like inclusions found in children with rimmed vacuoles and congenitally affected muscles. We immunostained muscle biopsy specimens from four children and one 18-year-old boy with congenital myopathy containing rimmed vacuoles and IBM-like inclusions with antibodies against b-amyloid, tau protein and ubiquitin. Focal accumulations of both b-amyloid and phosphorylated tau coexisted with tubulofilamentous structures in all cases. Our studies demonstrate for the first time that the full morphological phenotype of IBM including b-amyloid and tau protein deposits may also develop in children, and that congenital, probably genetic, muscle defects may lead to abnormal protein aggregation in IBM-like inclusions.


August
Published online before print August 1, 2006
Proc. Natl. Acad. Sci. USA, 10.1073/pnas.0604247103
Reconstitution of paired T cell receptor a- and b-chains from microdissected single cells of human inflammatory tissues
Sabine Seitz , Christian K. Schneider , Joachim Malotka , Xiao Nong , Andrew G. Engel, Hartmut Wekerle , Reinhard Hohlfeld , and Klaus Dornmair
We describe a strategy to "revive" putatively pathogenic T cells from frozen specimens of human inflammatory target organs. To distinguish pathogenic from irrelevant bystander T cells, we focused on cells that were (i) clonally expanded and (ii) in direct morphological contact with a target cell. Using CDR3 spectratyping, we identified clonally expanded T cell receptor (TCR) a-chains in muscle sections of patients with inflammatory muscle diseases. By immunohistochemistry, we identified those Vb-positive T cells that fulfilled the morphological criteria of myocytotoxicity and isolated them by laser microdissection. Next, we identified coexpressed pairs of TCR a- and a-chains by a multiplex PCR protocol, which allows the concomitant amplification of both chains from single cells. This concomitant amplification had not been achieved previously in histological sections, mainly because of the paucity of available anti-a-chain antibodies and the great heterogeneity of the a-chain genes. From muscle tissue of a patient with polymyositis, we isolated 64 T cells that expressed an expanded Vb1 chain. In 23 of these cells, we identified the corresponding a-chain. Twenty of these 23 a-chains were identical, suggesting antigen-driven selection. After functional reconstitution of the ab-pairs, their antigen-recognition properties could be studied. Our results open avenues for combined analysis of the full TCR a- and b-chain repertoire in human inflammatory tissues.


July
Muscle Nerve. 2006 Jul 5; [Epub ahead of print]
Nuclear membrane proteins are present within rimmed vacuoles in inclusion-body myositis.
Greenberg SA, Pinkus JL, Amato AA.
Department of Neurology, Division of Neuromuscular Disease, Brigham and Women's Hospital, 75 Francis St., Boston, Massachusetts 02115, USA.
The rimmed vacuoles within muscle in inclusion-body myositis (IBM) are structures of uncertain origin. Two hypotheses have been proposed for their formation: that they develop as a consequence of abnormal lysosomal function or in association with the breakdown of myonuclei. We tested the latter hypothesis by studying muscle samples from 14 patients with IBM and 18 controls using immunohistochemistry for nuclear membrane proteins, examining semithin sections, and performing electron microscopy. We found that in IBM muscle vacuoles were immunoreactive for the inner nuclear membrane proteins emerin and lamin A/C. Myonuclei with fragmented or focally absent nuclear membranes were present in immunohistochemical and electron microscopy studies. The association of nuclear membrane proteins with rimmed vacuoles confirms the hypotheses that rimmed vacuoles in IBM form in association with myonuclear pathology and that IBM differs from other inflammatory myopathies in that abnormalities of myonuclei are more prominent.


July
Muscle Nerve. 2006 Jul 5; [Epub ahead of print]
Nuclear membrane proteins are present within rimmed vacuoles in inclusion-body myositis.
Greenberg SA, Pinkus JL, Amato AA.
Department of Neurology, Division of Neuromuscular Disease, Brigham and Women's Hospital, 75 Francis St., Boston, Massachusetts 02115, USA.
The rimmed vacuoles within muscle in inclusion-body myositis (IBM) are structures of uncertain origin. Two hypotheses have been proposed for their formation: that they develop as a consequence of abnormal lysosomal function or in association with the breakdown of myonuclei. We tested the latter hypothesis by studying muscle samples from 14 patients with IBM and 18 controls using immunohistochemistry for nuclear membrane proteins, examining semithin sections, and performing electron microscopy. We found that in IBM muscle vacuoles were immunoreactive for the inner nuclear membrane proteins emerin and lamin A/C. Myonuclei with fragmented or focally absent nuclear membranes were present in immunohistochemical and electron microscopy studies. The association of nuclear membrane proteins with rimmed vacuoles confirms the hypotheses that rimmed vacuoles in IBM form in association with myonuclear pathology and that IBM differs from other inflammatory myopathies in that abnormalities of myonuclei are more prominent. Muscle Nerve, 2006.


June
Acta Neuropathol (Berl). 2006Aug;112(2):185-93. Jun 21; [Epub ahead of print]
Rimmed vacuoles with b-amyloid and tau protein deposits in the muscle of children with hereditary myopathy.
Fidzianska A, Glinka Z.
Neuromuscular Unit MRC, Polish Academy of Science, Pawinskiego 5, 02-106, Warsaw, Poland, neurmyol@cmdik.pan.pl.
We investigated whether b-amyloid and tau protein are involved in the formation of inclusion body myositis (IBM)-like inclusions found in children with rimmed vacuoles and congenitally affected muscles. We immunostained muscle biopsy specimens from four children and one 18-year-old boy with congenital myopathy containing rimmed vacuoles and IBM-like inclusions with antibodies against b-amyloid, tau protein and ubiquitin. Focal accumulations of both b-amyloid and phosphorylated tau coexisted with tubulofilamentous structures in all cases. Our studies demonstrate for the first time that the full morphological phenotype of IBM including b-amyloid and tau protein deposits may also develop in children, and that congenital, probably genetic, muscle defects may lead to abnormal protein aggregation in IBM-like inclusions.


June
J Neuropathol Exp Neurol. 2006 Jun;65(6):571-581.
Novel Ubiquitin Neuropathology in Frontotemporal Dementia With Valosin-Containing Protein Gene Mutations.
Forman MS, Mackenzie IR, Cairns NJ, Swanson E, Boyer PJ, Drachman DA, Jhaveri BS, Karlawish JH, Pestronk A, Smith TW, Tu PH, Watts GD, Markesbery WR, Smith CD, Kimonis VE.
Frontotemporal dementia (FTD) with inclusion body myopathy and Paget disease of bone (IBMPFD) is a rare, autosomal-dominant disorder caused by mutations in the valosin-containing protein (VCP) gene, a member of the AAA-ATPase gene superfamily. The neuropathology associated with sporadic FTD is heterogeneous and includes tauopathies and frontotemporal lobar degeneration with ubiquitin-positive inclusions (FTLD-U). However, there is limited information on the neuropathology in IBMPFD. We performed a detailed, systematic analysis of the neuropathologic changes in 8 patients with VCP mutations. A novel pattern of ubiquitin pathology was identified in IBMPFD that was distinct from sporadic and familial FTLD-U without VCP gene mutations. This was characterized by ubiquitin-positive neuronal intranuclear inclusions and dystrophic neurites. In contrast to FTLD-U, only rare intracytoplasmic inclusions were identified. The ubiquitin pathology was abundant in the neocortex, less robust in limbic and subcortical nuclei, and absent in the dentate gyrus. Only rare inclusions were detected with antibodies to VCP and there was no biochemical alteration in the VCP protein. VCP is associated with a variety of cellular activities, including regulation of the ubiquitin-proteasome system. Our findings are consistent with the hypothesis that the pathology associated with VCP gene mutations is the result of impairment of ubiquitin-based degradation pathways.


June
Am J Pathol. 2006 Jun;168(6):1986-97.
Genetically augmenting Ab42 levels in skeletal muscle exacerbates inclusion body myositis-like pathology and motor deficits in transgenic mice.
Kitazawa M, Green KN, Caccamo A, LaFerla FM.
Department of Neurobiology and Behavior, 1109 Gillespie Neuroscience Facility, University of California, Irvine, Irvine, CA 92697-4545, USA.
The pathogenic basis of inclusion body myositis (IBM), the leading muscle degenerative disease afflicting the elderly, is unknown, although the histopathological features are remarkably similar to those observed in Alzheimer's disease. One leading hypothesis is that the buildup of amyloid-b (Ab) peptide within selective skeletal muscle fibers contributes to the degenerative phenotype. Ab is a small peptide derived via endoproteolysis of the amyloid precursor protein (APP). To determine the pathogenic effect of augmenting Ab42 levels in skeletal muscle, we used a genetic approach to replace the endogenous wild-type presenilin-1 (PS1) allele with the PS1(M146V) allele in MCK-APP mice. Although APP transgene expression was unaltered, Ab levels, particularly Ab42, were elevated in skeletal muscle of the double transgenic (MCK-APP/PS1) mice compared to the parental MCK-APP line. Elevated phospho-tau accumulation was found in the MCK-APP/PS1 mice, and the greater activation of GSK-3b and cdk5 were observed. Other IBM-like pathological features, such as inclusion bodies and inflammatory infiltrates, were more severe and prominent in the MCK-APP/PS1 mice. Motor coordination and balance were more adversely affected and manifested at an earlier age in the MCK-APP/PS1 mice. The data presented here provide experimental evidence that Ab42 plays a proximal and critical role in the muscle degenerative process.


June
Eur Neurol. 2006 Jun 13;55(4):183-188 [Epub ahead of print]
Needle Electromyographic Findings in 98 Patients with Myositis.
Blijham PJ, Hengstman GJ, Hama-Amin AD, van Engelen BG, Zwarts MJ.
Department of Clinical Neurophysiology, Institute of Neurology, aRadboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
Background/Aims: Little is known about the distribution of electromyographic (EMG) abnormalities in myositis even though this is relevant in daily practice. Methods: A retrospective semiquantitative analysis of needle EMG findings was performed in a group of 98 patients with myositis. The frequency, type, and distribution of abnormalities were studied. The influence of the use of corticosteroids and the stage of the disease were evaluated. Results: In most patients, a myopathic pattern with spontaneous activity was found, although several clinically relevant exceptions were noted. Long-duration motor unit potentials were found in all three diagnostic groups and were not associated with disease duration. In the lower extremity a distal to proximal gradient was present, adding to the diagnostic confusion with neurogenic diseases, and spontaneous activity was absent in a relatively large group although none of the patients in the acute stage of the disease had a normal EMG. The use of corticosteroids reduced the number of abnormal findings in dermatomyositis and polymyositis, but not in inclusion body myositis. Conclusion: A myopathic pattern with spontaneous activity was most frequently found, although several clinically relevant exceptions were noted. These results illustrate the spectrum of EMG findings in myositis, and may aid the clinician in the interpretation of the EMG in these patients. Copyright (c) 2006 S. Karger AG, Basel.


June
Curr Rheumatol Rep. 2006 Jun;8(3):178-87.
Differential diagnosis of idiopathic inflammatory myopathies.
Baer AN.
Department of Medicine, Division of Allergy, Immunology, and Rheumatology, School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Erie County Medical Center, 462 Grider Street, Buffalo, NY 14215, USA. alanbaer@buffalo.edu
Symmetric proximal muscle weakness has many potential etiologies. An onset over weeks to months and elevated serum levels of muscle enzymes point to the diagnosis of an idiopathic inflammatory myopathy, including dermatomyositis, polymyositis, and inclusion body myositis. However, there is a broad differential diagnosis, including certain muscular dystrophies, metabolic myopathies, drug- or toxin-induced myotoxicity, neuropathies, and infectious myositides. The differentiation is critical for defining appropriate treatment. In addition, an alternative diagnosis may explain the lack of response to immunosuppressive treatment for some patients with polymyositis. Careful clinical evaluation and choice of available diagnostic tests are required to establish the correct diagnosis.


May
Autoimmunity. 2006 May;39(3):161-70.
Update on idiopathic inflammatory myopathies.
Briani C, Doria A, Sarzi-Puttini P, Dalakas MC.
University of Padova, Department of Neurosciences, Padova, Italy.
The inflammatory myopathies are a group of acquired diseases, characterized by an inflammatory infiltrate of the skeletal muscle. On the basis of clinical, immuno-pathological and demographic features, three major diseases can be identified: dermatomyositis (DM); polymyositis (PM); and inclusion body myositis (IBM). New diagnostic criteria have recently been introduced, which are crucial for discriminating between the three different subsets of inflammatory myopathies and for excluding other disorders. DM is a complement-mediated microangiopathy affecting skin and muscle. PM and IBM are T cell-mediated disorders, where CD8-positive cytotoxic T cells invade muscle fibres expressing MHC class I antigens, thus leading to fibre necrosis. In IBM, vacuolar formation with amyloid deposits are also present. This article summarizes the main clinical, laboratory, electrophysiological, immunological and histologic features as well as the therapeutic options of the inflammatory myopathies.


May
J Biol Chem. 2006 May 5;281(18):12809-16. Epub 2006 Mar 3.
Parkin protects against mitochondrial toxins and b-amyloid accumulation in skeletal muscle cells.
Rosen KM, Veereshwarayya V, Moussa CE, Fu Q, Goldberg MS, Schlossmacher MG, Shen J, Querfurth HW.
Department of Neurology, Caritas St. Elizabeth's Medical Center, Tufts University School of Medicine, Boston, Massachusetts 02135, USA. kenneth_rosen@cchcs.org
Mutations in the ubiquitin ligase-encoding Parkin gene have been implicated in the pathogenesis of autosomal recessive Parkinson disease. Outside of the central nervous system, Parkin is prominently expressed in skeletal muscle. We have found accumulations of Parkin protein in skeletal muscle biopsies taken from patients with inclusion body myositis, a degenerative disorder in which intramyofiber accumulations of the b-amyloid peptide are pathognomonic. In comparing primary cultures of skeletal muscle derived from parkin knock-out and wild-type mice, we have found the absence of parkin to result in greater sensitivity to mitochondrial stressors rotenone and carbonyl cyanide 3-chlorophenylhydrazone, without any alteration in sensitivity to calcium ionophore or hydrogen peroxide. Utilizing viral expression constructs coding for the Alzheimer disease and inclusion body myositis-linked b-amyloid precursor protein and for its metabolic byproducts A b42 and C100, we found that parkin knock-out muscle cells are also more sensitive to the toxic effects of intracellular A b. We also constructed a lentiviral system to overexpress wild-type Parkin and have shown that boosting the levels of parkin expression in normal skeletal muscle cultures provides substantial protection against both mitochondrial toxins and overexpressed b-amyloid. Correspondingly, exogenous Parkin significantly lowered A b levels. These data support the hypothesis that in myocytes parkin has dual properties in the maintenance of skeletal muscle mitochondrial homeostasis and in the regulation of A b levels.


May
Neuromuscul Disord. 2006 May;16(5):311-5. Epub 2006 Mar 24.
Sporadic inclusion body myositis in Japanese is associated with the MHC ancestral haplotype 52.1
Scott AP, Allcock RJ, Mastaglia F, Nishino I, Nonaka I, Laing N.
School of Surgery and Pathology, M504, UWA, Stirling Highway, Nedlands, WA 6009, Perth WA, Australia.
In Caucasians, sporadic inclusion body myositis has been associated with the MHC ancestral haplotypes; HLA-A1, B8, DR3 (8.1AH) and HLA-B35, DR1 (35.2AH). It is not known whether these haplotypes carry susceptibility for the disease in other ethnic groups. We report here the results of HLA-B and -DRB1 typing using a high-resolution sequence-based technique in a cohort of 31 Japanese patients with definite sIBM. Patient allele frequencies were 40.3% for HLA-B*5201 (10.7% in controls: p<0.001) and 37.1% for HLA-DRB1*1502 (10% in controls: p<0.001). Both alleles were found together as part of a conserved haplotype (52.1AH) at a frequency of 37.1% in patients (8.4% in controls: p<0.001). This is the first description of a haplotypic MHC association with sporadic inclusion body myositis in Japanese patients. These findings indicate that different MHC ancestral haplotypes are associated with sIBM in different ethnic groups and further emphasize the importance of genetic factors in this condition.
quote: Three separate HLA haplotypes have now been shown to be associated with sIBM in different ethnic groups the 8.1AH and 35.2AH in Caucasians and now the 52.1AH in Japanese. This finding represents a major step towards isolating a possible universal susceptibility factor for predisposition to sIBM. The linkage disequilibrium prevailing in the MHC region has consistently hampered efforts
to study MHC-related diseases. With three currently known haplotypes from two different ethnic groups, it may now be possible to explore the genetic factors influencing sIBM in a level of detail that was not previously feasible. . . . The fact that 8.1, 35.2 and 52.1AHs do not share any common HLA alleles suggests that the genes responsible for disease aetiology are not HLA genes and reside elsewhere in the MHC. It is possible that the disease causing gene may not be involved in antigen presentation. Previous research by Price et al. isolated sIBM susceptibility in the Caucasian population to a region between HOX12 and HLA-DRB1.


May
Curr Opin Rheumatol 18:236-241.
Advances in the therapy of idiopathic inflammatory myopathies
Alan N. Baer
Purpose of review
To review progress in areas pertinent to the development of better therapies for the idiopathic inflammatory myopathies.
Recent findings
New classification criteria for the idiopathic inflammatory myopathies have been proposed in an effort to define disease subsets with more uniform prognoses andresponses to therapy. Diseases that may mimic the idiopathic inflammatory myopathies can be differentiated more accurately with molecular testing and biochemical and immunohistochemical analysis of muscle tissue. Advances in our understanding of the pathogenesis of the idiopathic inflammatory myopathies have served to identify potential new therapeutic targets. International collaborative study groups have reached consensus on outcome measures and on the optimal design of clinical trials in the idiopathic inflammatory myopathies. Tumor necrosis factor-a antagonists, rituximab, and the calcineurin inhibitors are being used to treat the idiopathic inflammatory myopathies, but their efficacy has not yet been tested in randomized clinical trials.
Summary
Future advances in the development of therapies for the idiopathic inflammatory myopathies have been enabled by recent progress in myositis classification, differential diagnosis, basic science, and clinical trial design. Preliminary studies suggest that calcineurin inhibitors, tumor necrosis factor antagonists, and rituximab may be effective treatments.


April
Brain. 2006 Apr;129(Pt 4):986-95. Epub 2006 Feb 2.
Shared blood and muscle CD8+ T-cell expansions in inclusion body myositis.
Dimitri D, Benveniste O, Dubourg O, Maisonobe T, Eymard B, Amoura Z, Jean L, Tiev K, Piette JC, Klatzmann D, Herson S, Boyer O.
Service de medecine interne 1, Hopital Pitie-Salpetriere, Paris, France.
Inclusion body myositis (IBM) is the most frequent inflammatory myopathy over the age of fifty. Pathological findings suggest that two processes may contribute to IBM pathogenesis: a primary degenerative process affecting muscle fibre and/or an autoimmune process mediated by major histocompatibility complex (MHC) class-I-restricted cytotoxic CD8+ T cells. Previous studies have demonstrated that muscle-infiltrating CD8+ T cells in IBM display restricted expression of T-cell receptor (TCR)-BV families or evidenced oligoclonal T-cell expansions. This study was performed to investigate whether blood T cells similarly exhibit clonal expansions due to the recirculation of muscle-infiltrating T cells in the periphery. For this, we studied the T-cell repertoire of 17 IBM patients by complementarity-determining-region (CDR) 3 length distribution (immunoscope) analysis of TCR-B transcripts. Mean age was 68 years (range 53-88) and mean duration of the disease was 6.5 years (2-20). Oligoclonal T-cell expansions were observed in the blood of IBM patients. The quantitative average perturbation D index was significantly increased in IBM patients [D = 13.7% +/- 1.2%, mean +/- standard error of measurement (SEM)] as compared with 17 age-matched controls suffering from connective tissue diseases not associated with T-cell repertoire perturbation, that is, dermatomyositis (DM) and systemic sclerosis (9.3 +/- 0.6%, P < 0.005). Nevertheless, there was no correlation between the level of blood perturbation and muscle inflammation. Sorting experiments showed that these perturbations were due to oligoclonal expansions of CD8+ T cells. In the three IBM patients analysed, we could relate the blood expansions to T-cell clones also found in muscle. The clonally expanded blood T cells dramatically responded to interleukin-2 (IL-2) in vitro, suggesting that they had been primed in vivo, presumably in response to yet unknown muscle auto-antigens. Together, our results indicate that clonally expanded muscle-infiltrating CD8+ T cells re-circulate in the blood and support the concept of a CD8+ T-cell-mediated autoimmune component in IBM, similarly to what is observed in polymyositis (PM).


April
Nat Clin Pract Rheumatol. 2006 Apr;2(4):219-27.
Mechanisms of disease: signaling pathways and immunobiology of inflammatory myopathies.
Dalakas MC.
Neuromuscular Diseases Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892-1382, USA. dalakasm@ninds.nih.gov
The signaling pathways involved in the immunobiology of polymyositis, dermatomyositis, and inclusion-body myositis are outlined in this Review, which is based on research performed during the past 10 years. In dermatomyositis, the complement cascade is activated and the expression of cytokines and chemokines is upregulated. In polymyositis and inclusion-body myositis, autoinvasive CD8+ T cells are clonally expanded. This T-cell subset possesses conserved amino-acid sequences in complementarity-determining region 3 of the T-cell receptor and, via the perforin pathway, exerts a myotoxic effect on muscle fibers that express major histocompatibility complex (MHC) class I molecules. In all inflammatory myopathies, molecules associated with T-cell transmigration and cytokine signaling, as well as chemokines and their receptors, are strongly expressed by endothelial and inflammatory cells. Early in the pathogenesis of polymyositis and inclusion-body myositis, expression of MHC class I molecules on muscle fibers is upregulated, even in the absence of autoinvasive CD8+ T cells. Emerging data indicate that such continuous upregulation of the expression of MHC class I molecules on muscle fibers leads to an endoplasmic reticulum stress response, intracellular accumulation of misfolded glycoproteins, and activation of nuclear factor kb pathways, which can further stimulate formation of MHC class I-CD8 complexes, resulting in a self-sustaining inflammatory response. Advances in our understanding of the signaling pathways involved in the pathogenesis of these inflammatory myopathies are expected to result in the identification of novel therapeutic targets for these diseases.


April
Neuromuscular Disorders 16 (2006) 223-236 (Review)
Therapeutic targets in patients with inflammatory myopathies: Present approaches and a look to the future
Marinos C. Dalakas

7. Treatment of inclusion body myositis

In spite of immunopathological features identical to PM, IBM patients are difficult to treat. Although a number of patients may transiently respond to steroids, the majority do not. Methotrexate in a controlled study, was not better than placebo. Cyclosporin, Azathioprine or Total lymphoid irradiation are ineffective. IVIg may provide some benefit to a small number of patients for a period of time, especially in dysphagia, as demonstrated with a controlled study [92] and documented on subsequent open-label trials [94]. Since dysphagia is life threatening, IVIg should be considered in patients with significant swallowing difficulties and choking episodes. Collectively, my personal approach in the management of patients with IBM is sequentially as follows: (a) Inform the patient that there is no proven effective therapy. In such patients, I prescribe Co-enzyme Q10 and Vitamin E even though there is no demonstrable benefit. I also advocate a systematic non-fatiguing exercise program which has been shown to be of benefit [95]; (b) Administer low-dose, every other day, prednisone combined with mycophenolate in some patients hoping for disease stability with a clear explanation that the benefit from this regimen is anecdotal and not based on controlled studies; and (c) a trial with IVIg if there is significant worsening of muscle strength or life-threatening dysphagia.

10. Practical therapeutic considerations
In the light of the information presented earlier regarding the efficacy of these therapies, the following observations and practical tips may be useful [82,91]:

(a) Most patients with bona fide PM and DM respond to prednisone to a certain degree and for some period of time.

(b) A patient with presumed PM, who has not responded to any form of immunotherapy, most likely has IBM or another disease. In these cases, a repeat muscle biopsy and a more vigorous search for the 'other disease' are recommended.

(c) Calcinosis, a manifestation of DM, does not resolve with immunotherapies. New calcium deposits, however, may be prevented if the primary disease responds to the available therapies. Diphosphonates, aluminum hydroxide, probenecid, colchicines, low doses of warfarin, and surgical excision have all been tried without success.

(d) If prednisone or the other immunosuppressive therapies have not helped or have become ineffective in improving the patients' strength, they should be discontinued to avoid severe, irreversible adverse effects because, contrary to common belief, there is no evidence that their continuation maintains stability or prevents further disease progression.

(e) Patients with interstitial lung disease may have a high mortality rate, and require aggressive treatment with Cyclophosphamide, Cyclosporin, or Tacrolimus.

(f) In patients with cancer-associated myositis, the treatment of cancer is a priority. If the symptoms of myositis continue, treatment should be initiated as in the patients without cancer.

(g) Physical therapy to preserve existing muscle function, avoid disuse atrophy of the weak muscles, and prevent joint contractures should start early in the disease.

(h) When treatment of PM is unsuccessful, the patient should be reevaluated and the muscle biopsy reexamined. A new biopsy might be considered to make sure that the diagnosis is correct and that the diagnosis of IBM has not been overlooked. It should be kept in mind that PM is not a common disease. The disorders most commonly mistaken for PM are: IBM, sporadic limb-girdle dystrophy with endomysial inflammation resembling polymyositis, metabolic myopathy (such as phosphorylase deficiency), endocrinopathy, druginduced myopathies with some secondary inflammatory features, and neurogenic muscular atrophies.

(i) The major pitfalls leading to failure of steroid or immunosuppressive treatment include: (1) inadequate initial dose of prednisone or cytotoxic drugs; (2) short duration of therapy or quick tapering; (3) early discontinuation of prednisone without keeping a 'maintenance' low-dose therapy; (4) early development of preventable side effects necessitating early discontinuation of prednisone; and (5) wrong diagnosis.

. . . For the future, it is to be hoped that new techniques will continue to advance our understanding of the immunopathogenesis of PM, DM, IBM, and that these advances in knowledge can be rapidly translated into therapeutic applications. These agents should be cautiously selected considering their cost and safety profile. If promising in small pilot trials, they should be always tested in controlled studies. For IBM, strategies to inhibit myofiber cell-stress response by targeting the molecules implicated in MHCactivation and protein misfolding may be rewarding.


March
NEUROLOGY 2006;66:755'758
NCAM is hyposialylated in hereditary inclusion body myopathy due to GNE mutations
E. Ricci, MD*; A. Broccolini, MD, PhD*; T. Gidaro, MD; R. Morosetti, MD; C. Gliubizzi, MSc; R. Frusciante, MD; G.M. Di Lella, MD; P.A. Tonali, MD; and M. Mirabella, MD, PhD
Abstract The authors found that the neural cell adhesion molecule (NCAM) is hyposialylated in hereditary inclusion body myopathy (HIBM) muscle, as suggested by its decreased molecular weight by Western blot. This abnormality represented the only pathologic feature differentiating HIBM due to GNE mutations from other myopathies with similar clinical and pathologic characteristics. If further confirmed in larger series of patients, this may be a useful diagnostic marker of GNE-related HIBM.

Autosomal recessive hereditary inclusion body myopathy (HIBM, MIM# 600737) is associated with mutations in the UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase gene(GNE) that codes for a bifunctional enzyme with a critical role in sialic acid biosynthesis.1 Whether GNE mutations always result in abnormal sialylation of glycoproteins in HIBM muscle has not been fully elucidated.2-4

. . . An abnormal expression of NCAM has been previously demonstrated in vacuolated fibers of HIBM muscle.9 Whether a hyposialylated NCAM has a pathogenic role in HIBM remains to be determined. PSA-NCAM has been shown to have a role in NMJphysiology, as mice lacking NCAM show structuraland functional abnormalities of the NMJ.6 In vitro it has been shown that cultured HIBM myotubes cannot be properly innervated by neurites of rat spinal cord explants and a mechanism of 'myogenous dysreception to innervation' has been proposed.10 Therefore, it is possible that in HIBM muscle fibers,the underlying metabolic defect results in impairment of NMJ stabilization, as these fibers are initially properly innervated but later probably loose their contact with the nerve terminal. Indeed, HIBM muscle biopsies are often characterizedby a variable amount of panesterase-positive angulated atrophic fibers, thus suggesting an ongoing process of denervation.7 Further studies are necessary to clarify whether the hyposialylation of NCAM, as demonstrated in our study, plays a role in such abnormalities.


March
Biochemistry. 2006 Mar 7;45(9):2968-77.
Influence of UDP-GlcNAc 2-epimerase/ManNAc kinase mutant proteins on hereditary inclusion body myopathy.
Penner J, Mantey LR, Elgavish S, Ghaderi D, Cirak S, Berger M, Krause S, Lucka L, Voit T, Mitrani-Rosenbaum S, Hinderlich S.
Charite-Universitatsmedizin Berlin, Campus Benjamin Franklin, Institut fur Biochemie und Molekularbiologie, Arnimallee 22, 14195 Berlin-Dahlem, Germany.
Hereditary inclusion body myopathy (HIBM), a neuromuscular disorder, is caused by mutations in UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE), the key enzyme of sialic acid biosynthesis. To date, more than 40 different mutations in the GNE gene have been reported to cause the disease. Ten of them, representing mutations in both functional domains of GNE, were recombinantly expressed in insect cells (Sf9). Each of the mutants that was analyzed displayed a reduction in the two known GNE activities, thus revealing that mutations may also influence the function of the domain not harboring them. The extent of reduction strongly differs among the point mutants, ranging from only 20% reduction found for A631T and A631V to almost 80% reduction of at least one activity in D378Y and N519S mutants and more than 80% reduction of both activities of G576E, underlined by structural changes of N519S and G576E, as observed in CD spectroscopy and gel filtration analysis, respectively. We therefore generated models of the three-dimensional structures of the epimerase and the kinase domains of GNE, based on Escherichia coli UDP-N-acetylglucosamine 2-epimerase and glucokinase, respectively, and determined the localization of the HIBM mutations within these proteins. Whereas in the kinase domain most of the mutations are localized inside the enzyme, mutations in the epimerase domain are mostly located at the protein surface. Otherwise, the different mutations result in different enzymatic activities but not in different disease phenotypes and, therefore, do not suggest a direct role of the enzymatic function of GNE in the disease mechanism.


March
J Neurochem. 2006 Mar;96(5):1491-9. Epub 2006 Jan 25.
Homocysteine-induced endoplasmic reticulum protein (Herp) is up-regulated in sporadic inclusion-body myositis and in endoplasmic reticulum stress-induced cultured human muscle fibers.
Nogalska A, Engel WK, McFerrin J, Kokame K, Komano H, Askanas V.
USC Neuromuscular Center, Department of Neurology, University of Southern California Keck School of Medicine, Good Samaritan Hospital, Los Angeles, California, USA.
Herp is a stress-response protein localized in the endoplasmic reticulum (ER) membrane. Herp was proposed to improve ER-folding, decrease ER protein load, and participate in ER-associated degradation (ERAD). Intra-muscle-fiber ubiquitinated multiprotein-aggregates containing, among other proteins, either amyloid-b (Ab) or phosphorylated tau are characteristic of sporadic inclusion-body myositis (s-IBM). ER stress and proteasome inhibition appear to play a role in s-IBM pathogenesis. We have now studied Herp in s-IBM muscle fibers and in ER-stress-induced or proteasome-inhibited cultured human muscle fibers. In s-IBM muscle fibers: (i) Herp was strongly immunoreactive in the form of aggregates, which co-localized with Ab, GRP78, and b2 proteasome subunit; (ii) Herp mRNA and protein were increased. In ER-stress-induced cultured human muscle fibers: (i) Herp immunoreactivity was diffusely increased; (ii) Herp mRNA and protein were increased. In proteasome-inhibited cultured human muscle fibers: (i) Herp immunoreactivity was in the form of aggregates; (ii) Herp protein was increased, but its mRNA was not. Accordingly, in s-IBM muscle fibers: (i) increase of Herp might be due to both ER-stress and proteasome inhibition; (ii) co-localization of Herp with Ab, proteasome, and ER-chaperone GRP78 could reflect its possible role in processing and degradation of cytotoxic proteins in ER.


March
J Biol Chem. 2006 Mar 3; [Epub ahead of print]
Parkin protects against mitochondrial toxins and b -amyloid accumulation in skeletal muscle cells.
Rosen KM, Veereshwarayya V, Moussa CE, Fu Q, Goldberg MS, Schlossmacher MG, Shen J, Querfurth HW.
Neurology Dept., Caritas St. Elizabeth's Medical Center, Boston, MA 02135.
Mutations in the ubiquitin ligase-encoding Parkin gene have been implicated in the pathogenesis of autosomal recessive Parkinson disease. Outside of the central nervous system, Parkin is prominently expressed in skeletal muscle. We have found accumulations of Parkin protein in skeletal muscle biopsies taken from patients with Inclusion Body Myositis (IBM), a degenerative disorder in which intramyofiber accumulations of the b-amyloid peptide are pathognomonic. In comparing primary cultures of skeletal muscle derived from parkin knockout and wild-type mice, we have found the absence of parkin to result in greater sensitivity to mitochondrial stressors rotenone and carbonyl cyanide 3-chlorophenylhydrazone, without any alteration in sensitivity to calcium ionophore or hydrogen peroxide. Utilizing viral expression constructs coding for the Alzheimer's disease and IBM-linked b-amyloid precursor protein (bAPP) and for its metabolic byproducts Ab42 and C100, we find that parkin knockout muscle cells are also more sensitive to the toxic effects of intracellular Ab. We also constructed a lentiviral system to overexpress wild-type Parkin, and show that boosting the levels of parkin expression in normal skeletal muscle cultures provides substantial protection against both mitochondrial toxins and overexpressed b-amyloid. Correspondingly, exogenous Parkin significantly lowered Ab levels. These data support the hypothesis that in myocytes parkin has dual properties in the maintenance of skeletal muscle mitochondrial homeostasis and in the regulation of Ab levels.


February
Autoimmun Rev. 2006 Feb;5(2):93-100. Epub 2005 Jun 17.
Difference in adhesion molecule expression (ICAM-1 and VCAM-1) in juvenile and adult dermatomyositis, polymyositis and inclusion body myositis.
Sallum AM, Kiss MH, Silva CA, Wakamatsu A, Vianna MA, Sachetti S, Marie SK.
Department of Pediatrics--University of Sao Paulo Medical School, Brazil. adrianasallum@ig.com.br
To assess the differential expression of adhesion molecules ICAM-1 and VCAM-1 in vessels and muscle fibers in acquired inflammatory myopathy, a series comprising thirty-seven muscle biopsy specimens from patients with JDM, fifteen with DM, fifteen with PM and seven with IBM was studied. Histochemical and immunohistochemical tests (StreptABCcomplex/HRP) for ICAM-1 and VCAM-1 (Dakopatts) were performed in serial frozen sections. ICAM-1 expression in vessels was significantly (p<0.0001) more present in JDM than PM, DM or IBM. However, in muscle fibers, ICAM-1 expression was absent in both JDM and IBM, but present in 33.4% and 40% in PM and DM respectively (p<0.0001). VCAM-1 expression in vessels was significantly more present in PM and DM than JDM and IBM (p<0.0001) while VCAM-1 expression in muscle fibers was almost absent in the four groups (p=0.2632). These findings emphasize the importance of adhesion molecules in the pathophysiology of the inflammatory myopathies, mainly the marked ICAM-1 expression in vessels in JDM, corroborating the microvascular involvement in this disease. In contrast, VCAM-1 seems not to play a major role in JDM, as previously described in PM, DM and IBM. Adhesion molecule expression in JDM presents a differential characteristic when compared to PM, DM and IBM.


February
Brain. 2006 Feb 2; [Epub ahead of print]
Shared blood and muscle CD8+ T-cell expansions in inclusion body myositis
Dimitri D, Benveniste O, Dubourg O, Maisonobe T, Eymard B, Amoura Z, Jean L, Tiev K, Piette JC, Klatzmann D, Herson S, Boyer O.
Service de medecine interne 1, Paris.
Inclusion body myositis (IBM) is the most frequent inflammatory myopathy over the age of fifty. Pathological findings suggest that two processes may contribute to IBM pathogenesis: a primary degenerative process affecting muscle fibre and/or an autoimmune process mediated by major histocompatibility complex (MHC) class-I-restricted cytotoxic CD8(+) T cells. Previous studies have demonstrated that muscle-infiltrating CD8(+) T cells in IBM display restricted expression of T-cell receptor (TCR)-BV families or evidenced oligoclonal T-cell expansions. This study was performed to investigate whether blood T cells similarly exhibit clonal expansions due to the recirculation of muscle-infiltrating T cells in the periphery. For this, we studied the T-cell repertoire of 17 IBM patients by complementarity-determining-region (CDR) 3 length distribution (immunoscope) analysis of TCR-B transcripts. Mean age was 68 years (range 53-88) and mean duration of the disease was 6.5 years (2-20). Oligoclonal T-cell expansions were observed in the blood of IBM patients. The quantitative average perturbation D index was significantly increased in IBM patients [D = 13.7% +/- 1.2%, mean +/- standard error of measurement (SEM)] as compared with 17 age-matched controls suffering from connective tissue diseases not associated with T-cell repertoire perturbation, that is, dermatomyositis (DM) and systemic sclerosis (9.3 +/- 0.6%, P < 0.005). Nevertheless, there was no correlation between the level of blood perturbation and muscle inflammation. Sorting experiments showed that these perturbations were due to oligoclonal expansions of CD8(+) T cells. In the three IBM patients analysed, we could relate the blood expansions to T-cell clones also found in muscle. The clonally expanded blood T cells dramatically responded to interleukin-2 (IL-2) in vitro, suggesting that they had been primed in vivo, presumably in response to yet unknown muscle auto-antigens. Together, our results indicate that clonally expanded muscle-infiltrating CD8(+) T cells re-circulate in the blood and support the concept of a CD8(+) T-cell-mediated autoimmune component in IBM, similarly to what is observed in polymyositis (PM).


January 2006
Neurology. 2006 Jan 24;66(2 Suppl 1):S123-4.
Pilot trial of etanercept in the treatment of inclusion-body myositis.
Barohn RJ, Herbelin L, Kissel JT, King W, McVey AL, Saperstein DS, Mendell JR.
Department of Neurology, University of Kansas Medical Center, Kansas City, KS
66160, USA. rbarohn@kumc.edu Inclusion-body myositis (IBM) is an inflammatory muscle disease that has proven resistant to treatment. Tumor necrosis factor molecules have been detected in muscle biopsies from patients with IBM. Etanercept is a TNFalpha receptor fusion protein that binds and inactivates tumor necrosis factor. Nine patients were treated with etanercept at a dose of 25 mg, two times a week for an average of 17 +/- 6.1 months. Each patient was evaluated using quantitative strength testing. Their data were compared to two different control groups. The first control group consisted of patients who participated in trials of beta-interferon-1A and had received placebo. There was no significant difference. The second control group was a natural history cohort of IBM patients. There was no statistically significant difference between the treated group and the natural history group at 6 and 12 months when looking at elbow flexors, or 6 months when looking at hand grip. In the treated patients there was a small but significant improvement (p = 0.002) in handgrip at 12 months.


January 2006
Journal of Neurochemistry, 2006, 96, 777-789
Neprilysin participates in skeletal muscle regeneration and is accumulated in abnormal muscle fibres of inclusion body myositis.
Broccolini A, Gidaro T, Morosetti R, Gliubizzi C, Servidei T, Pescatori M, Tonali PA, Ricci E, Mirabella M.
Department of Neuroscience, Catholic University, Rome, Italy.
Neprilysin (NEP, EP24.11), a metallopeptidase originally shown to modulate signalling events by degrading small regulatory peptides, is also an amyloid-b- (Ab) degrading enzyme. We investigated a possible role of NEP in inclusion body myositis (IBM) and other acquired and hereditary muscle disorders and found that in all myopathies NEP expression was directly associated with the degree of muscle fibre regeneration. In IBM muscle, NEP protein was also strongly accumulated in Ab-bearing abnormal fibres. In vitro, during the experimental differentiation of myoblasts, NEP protein expression was regulated at the post-transcriptional level with a rapid increase in the early stage of myoblast differentiation followed by a gradual reduction thereafter, coincident with the progression of the myogenic programme. Treatment of differentiating muscle cells with the NEP inhibitor dl-3-mercapto-2-benzylpropanoylglycine resulted in impaired differentiation that was mainly associated with an abnormal regulation of Akt activation. Therefore, NEP may play an important role during muscle cell differentiation, possibly through the regulation, either directly or indirectly, of the insulin-like growth factor I-driven myogenic programme. In IBM muscle increased NEP may be instrumental in (i) reducing the Ab accumulation in vulnerable fibres and (ii) promoting a repair/regenerative attempt of muscle fibres possibly through the modulation of insulin-like growth factor I-dependent pathways.
From the Discussion
Interestingly, to date numerous proteins including Ab precursor protein, IGF-I, apoE and prion protein, shown to be increased in the course of muscle fibre regeneration, have also been found aberrantly accumulated in non-regenerating abnormal fibres of IBM muscle (Sarkozi et al. 1994a, 1994b; Mirabella et al. 1996b; Broccolini et al. 2000; Askanas and Engel 2002). It is not known whether this aspect represents a general dysregulation in the expression of different genes, specifically connected with the peculiar pathogenic mechanism of IBM, or reflects a genuine attempt to repair/regenerate vulnerable fibres. Our finding of increased NEP in abnormal IBM muscle fibres further strengthens the evidence of activation of multiple metabolic pathways normally involved in muscle development. However, the reason why in IBM, despite the activation of potentially repairing mechanisms, muscle degeneration steadily progresses is not known. Therefore, a better elucidation of the function of molecules possibly involved in muscle development, such as NEP, may be relevant in understanding the defective regenerative properties of IBM muscle. This will probably give clues in the attempt to define new and more effective therapeutic strategies for IBM as well as for other neuromuscular disorders.


January 2006
Twenty two articles resulted from a conference held on inclusion body myositis (s-IBM) - Inclusion-body myositis: Clinical and pathologic aspects, and basic research potentially relevant to treatment. January 26-28, 2005 in Santa Monica. The TMA funded the Conference and the Muscular Dystrophy Association assisted by funding the printing and distribution of the Conference report. The 22 articles were published in electronic format as an Expedited E-Pub at www.neurology.org on December 16, 2005. They appear in print in Neurology Volume 66(2) Supplement 1 January 24, 2006. See this special section.


January 2006
Nat Genet. 2006 Jan;38(1):11-2.
Amyloid double trouble.
Hardy J.
John Hardy is at the Laboratory of Neurogenetics, National Institute on Aging, Porter Neuroscience Building, 35 Convent Drive, Bethesda, Maryland 20892, USA. hardyj@mail.nih.gov.
A new study [by Rovelet-Lecrux] shows that some cases of early-onset Alzheimer disease result from duplications of the APP locus, which encodes the amyloid b precursor protein. This finding fulfills a 20-year-old prediction that genetic variability in APP expression could lead to disease and provides further, perhaps definitive, evidence for the amyloid hypothesis of the disorder.
Reference: Nat Genet. 2006 Jan;38(1):24-6. APP locus duplication causes autosomal dominant early-onset Alzheimer disease with cerebral amyloid angiopathy. Rovelet-Lecrux A, Hannequin D, Raux G, Meur NL, Laquerriere A, Vital A, Dumanchin C, Feuillette S, Brice A, Vercelletto M, Dubas F, Frebourg T, Campion D.
Abstract: We report duplication of the APP locus on chromosome 21 in five families with autosomal dominant early-onset Alzheimer disease (ADEOAD) and cerebral amyloid angiopathy (CAA). Among these families, the duplicated segments had a minimal size ranging from 0.58 to 6.37 Mb. Brains from individuals with APP duplication showed abundant parenchymal and vascular deposits of amyloid-b peptides. Duplication of the APP locus, resulting in accumulation of amyloid-b peptides, causes ADEOAD with CAA.


January 2006
Age Ageing. 2006 Jan;35(1):91-4.
Inclusion body myositis: an underdiagnosed myopathy of older people.
Munshi SK, Thanvi B, Jonnalagadda SJ, Da Forno P, Patel A, Sharma S.
Department of Medicine for the Elderly, Leicester Royal Infirmary, Infirmary Square, Leicester LE1 5WW, UK.
Inclusion body myositis (IBM), a condition characterised by progressive muscle weakness and inclusion bodies visible on muscle biopsy, is the most common type of myopathy in patients over 50 years of age. However, it is not only under diagnosed but frequently misdiagnosed as polymyositis and hence wrongly treated with steroids. In the evaluation of progressive weakness in older Caucasian males, IBM should be an important diagnostic consideration. Treatment-resistant 'polymyositis' in patients over 50 years of age is often IBM. If there is no histological confirmation, the diagnostic criteria allow for a category of 'possible IBM'. Sometimes, the diagnosis is missed because of the slow progression of the disease and a lack of suspicion on the part of physicians. The following case report and literature review will explore many of these issues.