Maki Tateyama

Expression of tumor necrosis factor-α in muscles of polymyositis

Abstract We immunohistochemically examined biopsied muscles from nine untreated patients with polymyositis (PM) and five patients with other neuromuscular diseases (ONMD), using monoclonal antibodies to tumor necrosis factor-α (TNF-α) and lymphoid surface markers. In muscles of three patients with PM, we observed many TNF-α positive macrophages and lymphocytes in endomysium and around vessels in the muscles. By contrast, there were few, weakly TNF-α stained cells in muscles of three patients with ONMD. The ratio of TNF-α-positive cells to the muscle fibers and the ratio of TNF-α-positive cells to the mononuclear cells were significantly higher in PM compared with ONMD. In addition, we observed atrophic muscle fibers more frequently in TNF-α-positive muscles than TNF-α-negative ones. We conclude that, at least, in a part of PM patients, TNF-α produced locally may contribute to the pathogenesis of PM.

Exome sequencing identifies a novel TTN mutation in a family with hereditary myopathy with early respiratory failure

Myofibrillar myopathy (MFM) is a group of chronic muscular disorders that show the focal dissolution of myofibrils and accumulation of degradation products. The major genetic basis of MFMs is unknown. In 1993, our group reported a Japanese family with dominantly inherited cytoplasmic body myopathy, which is now included in MFM, characterized by late-onset chronic progressive distal muscle weakness and early respiratory failure. In this study, we performed linkage analysis and exome sequencing on these patients and identified a novel c.90263G>T mutation in the TTN gene (NM_001256850). During the course of our study, another groups reported three mutations in TTN in patients with hereditary myopathy with early respiratory failure (HMERF, MIM #603689), which is characterized by overlapping pathologic findings with MFMs. Our patients were clinically compatible with HMERF. The mutation identified in this study and the three mutations in patients with HMERF were located on the A-band domain of titin, suggesting a strong relationship between mutations in the A-band domain of titin and HMERF. Mutation screening of TTN has been rarely carried out because of its huge size, consisting of 363 exons. It is possible that focused analysis of TTN may detect more mutations in patients with MFMs, especially in those with early respiratory failure.

A novel mutation in PNPLA2 causes neutral lipid storage disease with myopathy and triglyceride deposit cardiomyovasculopathy: A case report and literature review

Mutations in PNPLA2 cause neutral lipid storage disease with myopathy (NLSDM) or triglyceride deposit cardiomyovasculopathy (TGCV). We report a 59-year-old patient with NLSDM/TGCV presenting marked asymmetric skeletal myopathy and cardiomyovasculopathy. Skeletal muscle and endomyocardial biopsies showed cytoplasmic vacuoles containing neutral lipid. Gene analysis revealed a novel homozygous mutation (c.576delC) in PNPLA2. We reviewed 37 genetically-proven NLSDM/TGCV cases; median age was 30 years; distribution of myopathy was proximal (69%) and distal predominant (16%); asymmetric myopathy (right>left) was reported in 41% of the patients. Frequently-affected muscles were posterior compartment of leg (75%), shoulder girdle to upper arm (50%), and paraspinal (33%). Skeletal muscle biopsies showed lipid accumulation in 100% and rimmed vacuoles in 22%. Frequent comorbidities were cardiomyopathy (44%), hyperlipidemia (23%), diabetes mellitus (24%), and pancreatitis (14%). PNPLA2 mutations concentrated in Exon 4-7 without apparent genotype-phenotype correlations. To know the characteristic features is essential for the early diagnosis of NLSDM/TGCV.

Clinical features and a mutation with late onset of limb girdle muscular dystrophy 2B

Objective and methods Dysferlin encoded by DYSF deficiency leads to two main phenotypes, limb girdle muscular dystrophy (LGMD) 2B and Miyoshi myopathy. To reveal in detail the mutational and clinical features of LGMD2B in Japan, we observed 40 Japanese patients in 36 families with LGMD2B in whom dysferlin mutations were confirmed. Results and conclusions Three mutations (c.1566C>G, c.2997G>T and c.4497delT) were relatively more prevalent. The c.2997G>T mutation was associated with late onset, proximal dominant forms of dysferlinopathy, a high probability that muscle weakness started in an upper limb and lower serum creatine kinase (CK) levels. The clinical features of LGMD2B are as follows: (1) onset in the late teens or early adulthood, except patients homozygous for the c.2997G>T mutation; (2) lower limb weakness at onset; (3) distal change of lower limbs on muscle CT at an early stage; (4) impairment of lumbar erector spinal muscles on muscle CT at an early stage; (5) predominant involvement of proximal upper limbs; (6) preservation of function of the hands at late stage; (7) preservation of strength in neck muscles at late stage; (8) lack of facial weakness or dysphagia; (9) avoidance of scoliosis; (10) hyper-Ckaemia; (11) preservation of cardiac function; and (12) a tendency for respiratory function to decline with disease duration. It is important that the late onset phenotype is found with prevalent mutations.

Expression of OX40 in muscles of polymyositis and granulomatous myopathy

OX40 is selectively expressed on activated autoreactive memory T cells and these OX40+ lymphocytes may play a crucial role in autoimmune diseases. To determine whether OX40+ lymphocytes are involved in the pathomechanism of human inflammatory muscle diseases, we immunohistochemically examined the distribution of OX40+ cells in muscles from patients with polymyositis and granulomatous myopathy, and compared with that of cells bearing other activation markers, such as IL-2 receptor (IL-2R) and HLA-DR. In polymyositis, OX40+ mononuclear cells were found predominantly in the perivascular sites and to a lesser degree in the endomysium. Scanty IL-2R+ mononuclear cells were located only in the endomysium and HLA-DR was expressed on half of the mononuclear cells distributed diffusely in the perivascular sites and in the endomysium. Mononuclear cell infiltration in the perivascular sites was greater in the muscles in which OX40+ cells were present in the perivascular sites than in those without OX40+ cells in the perivascular sites (p<0.05). In granulomatous myopathy, OX40+ cells were detected in the centers of the granulomas. In contrast, IL-2R+ cells were present at the periphery of the granulomas and HLA-DR was detected on mononuclear cells throughout the granulomas. OX40+ mononuclear cells with specific distributions in muscles may be involved in the pathomechanism of polymyositis and granulomatous myopathy, and can be a candidate molecule of selective immunotherapy in these diseases.

Clinical values of FDG PET in polymyositis and dermatomyositis syndromes: imaging of skeletal muscle inflammation

Objectives [18F] Fluorodeoxyglucose positron emission tomography (FDG PET), a standard tool for evaluating malignancies, can also detect inflammatory lesions. However, its usefulness in evaluating muscle lesions in polymyositis and dermatomyositis syndromes (PM/DM) has not been established. Methods 33 patients with PM/DM who had undergone FDG PET were retrospectively analysed. FDG uptake was visually evaluated (visually identified FDG uptake, vFDG) in 16 regions of the body using mediastinum blood vessels as a positivity criterion. We also calculated the maximum standardised uptake value (SUVmax) in all four limbs of the patients with PM/DM as well as in 22 patients with amyotrophic lateral sclerosis (ALS) with similar disabilities. In 24 patients with PM/DM, MRI and FDG PET findings were compared. Results vFDG was observed in multiple muscle lesions with varying distributions in two-thirds of the patients with PM/DM, with most lesions being symmetrical. The number of vFDG-positive regions strongly correlated with the mean SUVmax in all four limbs (p<0.0001). Histological grades of biopsied muscles correlated with both the mean SUVmax and number of vFDG-positive regions. Serum creatine kinase levels were higher in patients with more than two vFDG-positive regions than in those with two or less regions (p<0.05). While the inflamed muscles showed diffused, patchy or marginal signal abnormalities on MRI, FDG uptake was most prominent inside the muscles. Compared with ALS, the mean SUVmax was significantly higher in the patients with PM/DM (p<0.0001) and showed a striking correlation in the bilateral muscles, reflecting symmetrical muscle involvement in PM/DM. Conclusions The visual assessment of FDG uptake as well as calculation of SUV enabled us to comprehensively evaluate skeletal muscle. This method can improve clinical practices and provide insights into pathomechanisms of PM/DM.

CCR7+ myeloid dendritic cells together with CCR7+ T cells and CCR7+ macrophages invade CCL19+ nonnecrotic muscle fibers in inclusion body myositis

CCR7 and its ligands CCL19 and CCL21 are a key chemokine system in T cell priming in secondary lymphoid organs, and are rarely expressed in normal muscle tissue. We immunohistochemically investigated the expression of this chemokine system in the muscles of seven patients with inclusion body myositis (IBM). In all cases, CCR7+ mononuclear cells infiltrated in the endomysium, preferentially surrounded and invaded nonnecrotic muscle fibers. Double immunostaining revealed that such CCR7+ mononuclear cells included BDCA-1+ myeloid dendritic cells as well as CD8+ cells, CD4+ cells and CD68+ macrophages. On the other hand, CCL19 was widely expressed on muscle fibers including those invaded by mononuclear cells. CCL19 was also expressed diffusely on endomysial mononuclear cells and endothelium of vessels. Immunoreactivities of CCL21 were detected on some muscle fibers and mononuclear cells. By RT-PCR analyses, mRNA of CCR7 was detected in all the patients and that of CCL19 and CCL21 was detected in six. These findings showed that the CCL19, CCL21/CCR7 chemokine system is expressed in muscles of IBM. The chemokine mediated attraction in dendritic and other immune cells and muscle cells may be crucial in sustained antigen presentation, T cell activation and immune attack to muscles in the pathogenesis of IBM.

GNE myopathy associated with congenital thrombocytopenia: A report of two siblings

GNE myopathy is an autosomal recessive muscular disorder caused by mutations in the gene encoding the key enzyme in sialic acid biosynthesis, UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE/MNK). Here, we report two siblings with myopathy with rimmed vacuoles and congenital thrombocytopenia who harbored two compound heterozygous GNE mutations, p.V603L and p.G739S. Thrombocytopenia, which is characterized by shortened platelet lifetime rather than ineffective thrombopoiesis, has been observed since infancy. We performed exome sequencing and array CGH to identify the underlying genetic etiology of thrombocytopenia. No pathogenic variants were detected among the known causative genes of recessively inherited thrombocytopenia; yet, candidate variants in two genes that followed an autosomal recessive mode of inheritance, including previously identified GNE mutations, were detected. Alternatively, it is possible that the decreased activity of GNE/MNK itself, which would lead to decreased sialic content in platelets, is associated with thrombocytopenia in these patients. Further investigations are required to clarify the association between GNE myopathy and the pathogenesis of thrombocytopenia.

Expression of CCR7 and its ligands CCL19/CCL21 in muscles of polymyositis

Polymyositis is an autoimmune disorder in which autoaggressive CD8(+) T cells are important in the pathogenesis. However, the mechanisms underlying sustained recruitment of these cells in the muscle tissue are still unknown. CCR7 and its ligands CCL19 and CCL21 are a chemokine system related to mononuclear cell migration and antigen presentation, and are suggested to play a key role in several autoimmune disorders. We investigated the expression of CCR7, CCL19 and CCL21 in frozen muscles of polymyositis. In immunohistochemistry, CCR7 was expressed mainly on mononuclear cells that infiltrated in the endomysium of polymyositis. 34.8+/-9.4% of endomysial mononuclear cells expressed CCR7. By double immunostaining, about 60% of endomysial CD8(+) T cells that surrounded the nonnecrotic muscle fibers coexpressed CCR7. Because most endomysial CD8(+) T cells expressed CD45RO, these were regarded as CD45RO(+)CCR7(+)CD8(+) T cells. On the other hand, CCL19 was expressed mainly on muscle fibers in proximity to CCR7(+) mononuclear cells, on the endothelium of the vessels and some mononuclear cells. CCL21 immunoreactivities were found on small numbers of mononuclear cells. In some cases, CCL21 immunoreactivities were also found on muscle fibers and the endothelium of vessels. In RT-PCR analysis, transcripts of CCR7 and CCL21 were detected in all the polymyositis muscles examined and that of CCL19 was detected in five out of seven polymyositis muscles. The CCL19,CCL21/CCR7 chemokine system is expressed in inflamed muscles of polymyositis and may be involved in the pathomechanism of polymyositis.

Proteasome dysfunction induces muscle growth defects and protein aggregation.

ABSTRACT The ubiquitin–proteasome and autophagy–lysosome pathways are the two major routes of protein and organelle clearance. The role of the proteasome pathway in mammalian muscle has not been examined in vivo. In this study, we report that the muscle-specific deletion of a crucial proteasomal gene, Rpt3 (also known as Psmc4), resulted in profound muscle growth defects and a decrease in force production in mice. Specifically, developing muscles in conditional Rpt3-knockout animals showed dysregulated proteasomal activity. The autophagy pathway was upregulated, but the process of autophagosome formation was impaired. A microscopic analysis revealed the accumulation of basophilic inclusions and disorganization of the sarcomeres in young adult mice. Our results suggest that appropriate proteasomal activity is important for muscle growth and for maintaining myofiber integrity in collaboration with autophagy pathways. The deletion of a component of the proteasome complex contributed to myofiber degeneration and weakness in muscle disorders that are characterized by the accumulation of abnormal inclusions.