Expression of immunoreactive major histocompatibility complex products in human skeletal muscles

Dystrophin expression in muscles of mdx mice after adenovirus-mediated in vivo gene transfer

We have generated high-titer adenoviral recombinants (AVR) expressing a 6.3-kb partial dystrophin cDNA insert under the control of either the Rous sarcoma virus (RSV) or cytomegalovirus (CMV) promoter. These AVR preparations were free of both E1-containing AVR and AVR with a nonfunctional dystrophin expression cassette. With these optimal AVR preparations, we have obtained a high degree of short-term (10 days) expression of a truncated (approximately 200 kD) dystrophin in dystrophin-deficient mdx muscles injected in the neonatal period; a lesser degree of expression of dystrophin was found in muscles injected in the young adult age and in old animals. Microscopic indices of muscle damage revealed that the truncated dystrophin provided a significant protection of the transduced muscle fibers. However, by 60 days post-injection, a substantial reduction of the number of dystrophin-positive fibers was noted, even in the neonatally injected muscles, and near-total elimination of dystrophin-positive fibers occurred in muscles injected in the adult age. These effects appeared to be brought about by the activity of CD8+ cytotoxic lymphocytes directed against the transduced cells, leading to their eventual elimination. In severe combined immunodeficiency (SCID) mice, lacking both humoral and cellular immune competence, muscles transduced (either in the neonatal or adult age) by AVR containing a CMV-LacZ expression cassette maintained the early (10 day) transduction level up to 30 days post-injection. Systemic administration of AVR (i.e., into the left ventricle of the heart) led in 5 days to a high number of dystrophin-positive fibers in heart, diaphragm, and intercostal muscles but not in limb muscles.

Antigen processing and presentation by a murine myoblast cell line

The ability of non-professional antigen-presenting cells (APC) to process and present antigen to the immune system has been the subject of debate in autoimmunity and tumour immunology. The role of muscle cells in the processing and presentation of antigen to T cells via class I and class II MHC pathways is of increasing interest. Muscle cells are the targets of autoimmune attack in the inflammatory muscle diseases, and direct intramuscular injection of antigen-expressing DNA constructs is under scrutiny as a means of vaccination. Furthermore, the immunological properties of muscle cells are of relevance in attempts to transfer myoblasts as replacement cells in dystrophic diseases or as depot cells for the secretion of certain molecules in deficiency states. Using class I and class II MHC transfectant clones of the C2C12 myoblast cell line, myoblasts have been shown to be capable of presenting antigen to, and stimulating secretion of IL-2 by, T cell hybridomas via both of these pathways. The epitopes which are dominantly presented by professional APC after processing of native antigens were also presented by the myoblast cell line after processing of either ovalbumin (class I) or hen egg lysozyme (class II). Further, antigen processing and presentation via the class II pathway were enhanced by pretreatment of the myoblasts with interferon-gamma (IFN-gamma). Up-regulation of invariant chain expression by this treatment may have contributed to this enhanced presentation, but an effect of IFN-gamma on the expression of other molecules such as H-2 DM may have also played a role. The demonstration of the antigen-presenting properties of these myoblasts is of relevance to all three areas mentioned above. In each situation myoblasts comprise a significant population within muscle. In the case of inflammatory muscle diseases the process of muscle degeneration and regeneration is on-going, while in the vaccination procedure some muscle damage occurs, and vaccination is more effective when muscle damage has preceded inoculation.

Update on the use of intravenous immune globulin in the treatment of patients with inflammatory muscle disease

The inflammatory myopathies consist of three distinct groups: dermatomyositis, polymyositis, and inclusion body myositis. Dermatomyositis is distinguished by its characteristic rash, while polymyositis is a diagnosis of exclusion. Inclusion body myositis is characterized by early involvement of distal muscle groups and the quadriceps. Definitive diagnosis is made by muscle biopsy, which demonstrates histological features characteristic for each disorder. Immune mechanisms play a role in the pathogenesis of the inflammatory myopathies. A complement-mediated microangiopathy is seen in dermatomyositis, while there is evidence for a T cell-mediated process in polymyositis and inclusion body myositis. Treatment with prednisone is helpful to a majority of patients for a period of time. Immunosuppressive drugs have met with limited success. We describe a group of patients with dermatomyositis, resistant to available therapies, whose muscle strength, skin changes, and muscle biopsies improved significantly during treatment with intravenous immune globulin. The treatment of polymyositis and inclusion body myositis with intravenous immune globulin is currently under study.

Inflammatory myopathies

New information regarding myositis specific autoantibodies, histopathologic analysis of muscle biopsy specimens, and immunogenetic features of the different serologic subsets of disease has greatly increased our understanding of the pathogenesis of the inflammatory myopathies. The clinical descriptions of inclusion body myositis and 'amyopathic dermatomyositis' (Euwer and Sontheimer, 1993) are examples of our expanded descriptive capabilities in the evaluation of patients with myopathy. Finally, newer techniques such as cytokine analysis and magnetic resonance imaging may help in the ongoing assessment of disease activity in patients with myositis. The combination of these recently described clinical and laboratory parameters are enough to force a reconsideration of the previously described classification and diagnostic criteria in the inflammatory myopathies.

Detection of HTLV-I provirus by in situ polymerase chain reaction in mononuclear inflammatory cells in skeletal muscle of viral carriers with polymyositis

We tested for HTLV-I proviral DNA in skeletal muscle from patients with polymyositis infected with HTLV-I using the in situ polymerase chain reaction. We found the HTLV-I provirus in some of the CD4-positive cells in HTLV-I-positive polymyositis cases but not in HTLV-I-negative polymyositis ones. We could not detect HTLV-I within the muscle fibers. We suggest that HTLV-I-associated polymyositis is not due to direct, persistent infection of the muscle fiber by the virus, but to a T-cell-mediated immunological process triggered by the HTLV-I-infected cells.

Focal myositis: a clinicopathological study

Focal myositis is a rare, benign inflammatory condition that may clinically simulate a soft tissue sarcoma. It was first described in 1977 and around 30 cases have been reported to date. We report two further cases on which we have performed immunocytochemistry and electron microscopy. Histology of both lesions was identical, showing a destructive inflammatory myopathy with evidence of regeneration. Stains for micro-organisms were negative and no viral particles were seen on electron microscopy. The immunocytochemical profile of our two cases differed from that of polymyositis: with a panel of T- and B-cell markers the cellular infiltrate was found to be composed of T-lymphocytes and variable numbers of macrophages: sub-typing in one case revealed the T-cells to be predominantly CD4+ cells. Use of antibodies to MHC class 1 and 2 antigens showed occasional positive inflammatory cells only. Clinicopathological correlations and the differential diagnosis are discussed.

Common variable immunodeficiency and inclusion body myositis: a distinct myopathy mediated by natural killer cells

Inclusion body myositis developed in two men, 36 and 48 years old with long-standing common variable immunodeficiency. Immunophenotypic analysis of the endomysial cells showed an increased number of natural killer (NK) cells (defined as CD57+, CD56+, CD3-, CD8-, CD68-) accounting for 8.5 to 9.5% of the total cells, compared with a mean of 1% in sporadic inclusion body myositis. The remaining cells were CD8+, macrophages, and CD4+ T cells. NK cells were positive for intercellular cell adhesion molecule-1 and invaded muscle fibers negative for major histocompatibility complex (MHC) class I. In contrast to ubiquitous endomysial expression of MHC class I antigen in sporadic inclusion body myositis, the MHC class I in common variable immunodeficiency and inclusion body myositis was absent or weakly expressed in only some of the muscle fibers surrounded by CD8+ cells. Enteroviral or retroviral RNA sequences were not amplified. Treatment with intravenous immunoglobulin improved strength in 1 patient whose repeated muscle biopsy specimen showed normal NK cells. We conclude that inclusion body myositis can develop in patients with common variable immunodeficiency. Common variable immunodeficiency with inclusion body myositis is an immune myopathy mediated by NK cells in a non-MHC class I-restricted cytotoxicity, and by CD8+ cells in an MHC class I-restricted process. This is the first description of an inflammatory myopathy in which NK cells participate in the myocytotoxic process.

X-linked vacuolated myopathy: complement membrane attack complex on surface membrane of injured muscle fibers

We describe a probable recessive X-linked myopathy characterized by the presence of vacuolated muscle fibers. Four males and their shared maternal grandfather were affected. Clinical characteristics include juvenile onset, very slow progression, and predominant proximal muscle involvement. The clinical picture and the morphological findings are compared with those previously described in a family. By immunofluorescence, all histologically abnormal muscle fibers, in particular those vacuolated, showed a strong deposition of the complement C5b-9 membrane attack complex over the whole muscle fiber surface. Weak immunostaining for membrane attack complex was also found in endomysial capillaries and perimysial vessel walls. Muscle fibers showed sarcolemmal immunolabeling with anti-major histocompatibility complex I, which was also present on the margins of many vacuoles. All vacuoles were stained by antidystrophin antibody, which colocalized in most of them with antilaminin immunostaining. Taken together, these results suggest that the deposition of membrane attack complex on the damaged cell surface membrane could be important in the pathogenesis of this muscle disorder, and that the membrane-bounded vacuoles could be a consequence of sarcolemmal invagination.

Local T-cell proliferation and differentiation in inflammatory myopathies

Our objective was to investigate the patterns of proliferation and differentiation of infiltrating cells in inflammatory myopathies. Immunohistochemical staining was performed on muscle biopsy specimens from 18 patients with inclusion body myositis, polymyositis and dermatomyositis using monoclonal and polyclonal antibodies. An abundance of cells were TNF-alpha+ (4-8%), ICAM-1+ (7-65%), IFN-gamma+ (3-6%), and Ki-67+ (4-8%). It was shown that 70% of the Ki-67+ cells were Ki-67+CD3+ cells. Very few mononuclear cells were IL-2R+. MHC-I expression was found on nearly all muscle fibres in all cases, while MHC-II expression was found on occasional muscle fibres in 1/3 of cases. Analysis of repeated biopsies from four IBM patients after prednisolone treatment showed no change in the proportions of TNF-alpha, ICAM-1, IFN-gamma or Ki-67 positive cells. In inflammatory myopathies there is an intense proliferation and differentiation of inflammatory cells in situ, indicating a local stimulation of the inflammatory process.

Immunopathogenesis of inflammatory myopathies

Immune-mediated mechanisms appear to play a primary role in the pathogenesis of polymyositis (PM) and dermatomyositis (DM). The serum of patients with active DM has high levels of circulating complement fragments C3b, C4b, and C5b-9 membranolytic attack complex (MAC) and demonstrates a very high C3 uptake in an vitro assay system. The MAC and the immune complex-specific C3bNEO fragment are deposited on the endomysial capillaries early in the disease and lead sequentially to loss of capillaries, muscle ischemia, muscle fiber necrosis, and perifascicular atrophy. In contrast, in PM the muscle fiber injury is initiated by sensitized CD8+ cytotoxic T cells that recognize heretofore unknown and probably endogenous muscle antigens in the context of major histocompatibility complex (MHC) class I expression. A restricted (oligoclonal) pattern of T-cell receptor with prominence of Va1, Vb6, and Vb15 genes is noted within the endomysial infiltrates suggesting that the T-cell response is antigen driven. In both PM and DM, intercellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1 are upregulated in the endomysial endothelial cells and function as ligands for the leukocyte integrins leukocyte function-associated antigen (LFA)-1 and very late activating antigen (VLA)-4, allowing activated lymphocytes to adhere to the endothelial cells and migrate to the muscle fibers. Among viruses, only the retroviruses human immunodeficiency virus (HIV) and human T-cell lymphotropic virus (HTLV)-1 have been convincingly shown to trigger PM, which is mediated by nonviral-specific, cytotoxic CD8+ cells. The treatment of inflammatory myopathies remains empirical. Many patients respond to steroids to some degree and for some period of time. Azathioprine, methotrexate, cyclosporine, cyclophosphamide, and plasmapheresis can be of mild to moderate benefit. High-dose intravenous immunoglobulin (IVIg) is a promising therapeutic modality for some patients resistant to therapies. In a controlled study, IVIg was effective in DM not only in improving the clinical symptoms but also in reversing the underlying immunopathology. The role of IVIg in PM and IBM is under study in control trials.

Functional effects of myoblast implantation into histoincompatible mice with or without immunosuppression

1. The goals of this study were to evaluate the immunogenicity of myogenic cells (MCs) (1) immediately after implantation into regenerating muscles, and (2) following their maturation under initial immunosuppression. Implanted mouse soleus muscles were evaluated by isometric tension recordings in vitro followed by histological investigations on frozen sections. 2. Implantation of non-histocompatible myoblasts into cryodamaged soleus muscles of CBA/J mice induced immune rejection which caused large and permanent deficits in muscle force: 4-42 weeks postimplantation maximal tetanic tension was 50-60% that of intact or regenerated cryodamaged control muscles without tendency for recovery or histological signs of muscle regeneration. Specific tension (force per unit muscle weight) was also significantly reduced. 3. On frozen sections, only 62 +/- 12% of the total area was desmin-positive, that is, occupied by muscle fibres, versus 90 +/- 4% in regenerated and 92 +/- 3% in intact muscles. Also, the total number of muscle fibre profiles was significantly reduced. 4. Under immune suppression with cyclosporin A (CsA), large muscles developed within 4 weeks. Following CsA withdrawal, muscle weight and force, in addition to desmin-positive areas on cross-sections, gradually declined over several months despite continual regeneration, indicating retarded immune rejection. 5. Initial application of CsA for 8 weeks after implantation, instead of 4 weeks, did not result in better survival of the implants, nor did a higher initial dose of CsA (100 instead of 50 mg kg-1 day-1). Prolonged continuous application of a reduced dose (25 mg kg-1 day-1) did not prevent muscle wasting but caused an additional delay. 6. It is concluded that histoincompatible myoblasts are highly immunogenic and that immune rejection causes large and permanent muscle deficits indicating elimination of host muscle tissue. Initial transient immunosuppression protects the incompatible cells, but after withdrawal, prolonged immune rejection and retarded muscle wasting occur.

Cellular and molecular reactions in mouse muscles after myoblast implantation

Implantation of skeletal muscle precursor cells is a potential means of cell-mediated gene therapy. One unresolved question is the degree of immunogenicity of such myoblasts. We designed the extreme situation of implanting cells of a non-histocompatible myoblast cell line into cryodamaged, but regeneration-capable, muscles of adult mice. Without immunosuppression donor cells are rejected within the first weeks. Immunosuppression with Cyclosporin A prevented invasion of T-lymphocytes and allowed differentiation of implanted myoblasts into myofibres as well as down-regulation of MHC expression. Still, withdrawal of Cyclosporin A after 4 weeks triggered lymphocyte invasion and cytotoxic cell reactions with rejection of donor tissue. Although the vast majority of muscle fibres was MHC-negative 1-4 days after Cyclosporin A withdrawal, single small desmin-positive profiles were weakly positive for donor MHC. Parallel with the increase in the number of lymphocytes, larger numbers of small and large muscle fibres expressed high levels of either donor, host or both, class I--but not class II--molecules. Surprisingly, immune reactions continued over several months, causing gradual loss of muscle tissue. Donor class I molecules persisted for more than 6 months after Cyclosporin A withdrawal, clearly indicating survival of donor muscle fibres despite ongoing rejection. Indirect evidence on the other hand suggests additional loss of host fibres, possibly caused by cytokine release from the immune cells (bystander damage). We conclude that transient treatment with Cyclosporin A induced a kind of tolerance related to the maturation and down-regulation of class I antigens in donor muscle fibres. It is suggested that the start of immune reaction following Cyclosporin A withdrawal is initiated by remaining small amounts of donor MHC molecules, possibly related to the continuous proliferation of the cell-lined-derived donor myoblasts.

Transient immunosuppressive treatment leads to long-term retention of allogeneic myoblasts in hybrid myofibers

Normal and genetically engineered skeletal muscle cells (myoblasts) show promise as drug delivery vehicles and as therapeutic agents for treating muscle degeneration in muscular dystrophies. A limitation is the immune response of the host to the transplanted cells. Allogeneic myoblasts are rapidly rejected unless immunosuppressants are administered. However, continuous immunosuppression is associated with significant toxic side effects. Here we test whether immunosuppressive treatment, administered only transiently after allogeneic myoblast transplantation, allows the long-term survival of the transplanted cells in mice. Two immunosuppressive treatments with different modes of action were used: (a) cyclosporine A (CSA); and (b) monoclonal antibodies to intracellular adhesion molecule-1 and leukocyte function-associated molecule-1. The use of myoblasts genetically engineered to express beta-galactosidase allowed quantitation of the survival of allogeneic myoblasts at different times after cessation of the immunosuppressive treatments. Without host immunosuppression, allogeneic myoblasts were rejected from all host strains tested, although the relative time course differed as expected for low and high responder strains. The allogeneic myoblasts initially fused with host myofibers, but these hybrid cells were later destroyed by the massive immunological response of the host. However, transient immunosuppressive treatment prevented the hybrid myofiber destruction and led to their long-term retention. Even four months after the cessation of treatment, the hybrid myofibers persisted and no inflammatory infiltrate was present in the tissue. Such long-term survival indicates that transient immunosuppression may greatly increase the utility of myoblast transplantation as a therapeutic approach to the treatment of muscle and nonmuscle disease.

Polymyositis in patients infected with human T-cell leukemia virus type I: the role of the virus in the cause of the disease

To investigate the mechanism of polymyositis in human T-cell leukemia virus type I (HTLV-I) infection, we studied 6 HTLV-I-positive patients, 3 with polymyositis and 3 with adult T-cell leukemia but without clinical signs of muscle disease, by (a) quantitative single or double immunocytochemistry on serial 4-microns-thick muscle biopsy sections using antibodies to lymphocyte subsets, major histocompatibility complex (MHC) antigens, and HTLV-I proteins; (b) polymerase chain reaction using HTLV-I primers in the RNA and DNA extracted from 50 micrograms of muscle tissue or from serial 5-microns-thick fresh-frozen tissue sections; and (c) cocultures of the patients' HTLV-I-positive peripheral blood lymphocytes with their homologous muscles searching for replication of HTLV-I within the myotubes. In the muscle of patients with HTLV-I-associated myopathy, the predominant endomysial cells surrounding healthy muscle fibers were CD8+ cells followed by CD4+ cells and macrophages. MHC-I antigens were ubiquitous in the muscles of all 6 patients, even in those without endomysial inflammation. HTLV-I sequences were amplified from the whole muscle biopsy specimens but the cells harboring viral antigens were rare endomysial macrophages and not muscle fibers. Although HTLV-I sequences were amplified from all the patients' peripheral blood lymphocytes, these cells did not exert myotoxicity or resulted in viral replication in cocultures with their homologous myotubes.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunization with plasmid DNA using a pneumatic gun

We characterize a method by which the Med-E-Jet pneumatic vaccination gun can be used to propel intact, supercoiled plasmid DNA through skin and into skeletal muscles of mice. Intramuscular injection of plasmids containing the firefly luciferase gene linked to the human cytomegalovirus promoter resulted in the expression of several hundred picograms of luciferase enzyme in quadriceps muscles. Intramuscular injections of a plasmid containing the influenza A nuclear protein gene regulated by the same promoter resulted in the generation of potent and specific anti-nuclear protein humoral and cellular immune responses. This convenient and rapid injection method would be well-suited for genetic immunization of humans.

Primary mouse myoblast purification, characterization, and transplantation for cell-mediated gene therapy

The transplantation of cultured myoblasts into mature skeletal muscle is the basis for a new therapeutic approach to muscle and non-muscle diseases: myoblast-mediated gene therapy. The success of myoblast transplantation for correction of intrinsic muscle defects depends on the fusion of implanted cells with host myofibers. Previous studies in mice have been problematic because they have involved transplantation of established myogenic cell lines or primary muscle cultures. Both of these cell populations have disadvantages: myogenic cell lines are tumorigenic, and primary cultures contain a substantial percentage of non-myogenic cells which will not fuse to host fibers. Furthermore, for both cell populations, immune suppression of the host has been necessary for long-term retention of transplanted cells. To overcome these difficulties, we developed novel culture conditions that permit the purification of mouse myoblasts from primary cultures. Both enriched and clonal populations of primary myoblasts were characterized in assays of cell proliferation and differentiation. Primary myoblasts were dependent on added bFGF for growth and retained the ability to differentiate even after 30 population doublings. The fate of the pure myoblast populations after transplantation was monitored by labeling the cells with the marker enzyme beta-galactosidase (beta-gal) using retroviral mediated gene transfer. Within five days of transplantation into muscle of mature mice, primary myoblasts had fused with host muscle cells to form hybrid myofibers. To examine the immunobiology of primary myoblasts, we compared transplanted cells in syngeneic and allogeneic hosts. Even without immune suppression, the hybrid fibers persisted with continued beta-gal expression up to six months after myoblast transplantation in syngeneic hosts. In allogeneic hosts, the implanted cells were completely eliminated within three weeks. To assess tumorigenicity, primary myoblasts and myoblasts from the C2 myogenic cell line were transplanted into immunodeficient mice. Only C2 myoblasts formed tumors. The ease of isolation, growth, and transfection of primary mouse myoblasts under the conditions described here expand the opportunities to study muscle cell growth and differentiation using myoblasts from normal as well as mutant strains of mice. The properties of these cells after transplantation--the stability of resulting hybrid myofibers without immune suppression, the persistence of transgene expression, and the lack of tumorigenicity--suggest that studies of cell-mediated gene therapy using primary myoblasts can now be broadly applied to mouse models of human muscle and non-muscle diseases.

The immunobiology of muscle

Skeletal muscle can be both the site and target of immune reactions. Here, Reinhard Hohlfeld and Andrew Engel consider the role of muscle as an immunological microenvironment and discuss the immunological properties of human muscle cells. Furthermore, they provide a brief overview of autoimmune diseases of muscle and of other conditions in which intramuscular immune reactions play a role. Finally, they discuss the immunological problems of novel gene therapies that rely on muscle cells as vehicles for gene transfer.

Cell transplantation for myocardial repair: an experimental approach

Myocardium lacks the ability to regenerate following injury. This is in contrast to skeletal muscle (SKM), in which capacity for tissue repair is attributed to the presence of satellite cells. It was hypothesized that SKM satellite cells multiplied in vitro could be used to repair injured heart muscle. Fourteen dogs underwent explantation of the anterior tibialis muscle. Satellite cells were multiplied in vitro and their nuclei were labeled with tritiated thymidine 24 h prior to implantation. The same dogs were then subjected successfully to a myocardial injury by the application of a cryoprobe. The cells were suspended in serum-free growth medium and autotransplanted within the damaged muscle. Medium without cells was injected into an adjacent site to serve as a control. Endpoints comprised histology using standard stains as well as Masson trichrome (specific for connective tissue), and radioautography. In five dogs, satellite cell isolation, culture, and implantation were technically satisfactory. In three implanted dogs, specimens were taken within 6-8 wk. There were persistence of the implantation channels in the experimental sites when compared to the controls. Macroscopically, muscle tissue completely surrounded by scar tissue could be seen. Masson trichrome staining showed homogeneous scar in the control site, but not in the test site where a patch of muscle fibres containing intercalated discs (characteristic of myocardial tissue) was observed. In two other dogs, specimens were taken at 14 wk postimplantation. Muscle tissue could not be found. These preliminary results could be consistent with the hypothesis that SKM satellite cells can form neo-myocardium within an appropriate environment. Our specimens failed to demonstrate the presence of myocyte nuclei.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunohistochemical analysis of perforin and granzyme A in inflammatory myopathies

Perforin (PF) and granzyme A (GA) are candidates suspected of being cytolytic proteins of the granules of cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells. We analysed PF and GA in muscles from patients with inflammatory myopathies. Five cases of polymyositis (PM), two cases of inclusion body myositis (IBM), and five cases of dermatomyositis (DM) were studied immunohistochemically using anti-PF and GA antibodies raised against each synthetic peptide of human PF and mouse GA, together with a panel of monoclonal antibodies reactive for lymphocyte subsets. In PM and IBM, PF positive cells were colocalized with GA positive cells and occasionally invaded into the non-necrotic muscle fibres. The percentage of PF positive cells among the endomysial CD8 positive cell population was 9.9% (PM) and 12.5% (IBM), and the majority of the endomysial CD8 positive cells were alpha/beta T cells. In contrast, in DM, both PF and GA positive cells were very few in all cases. Only few inflammatory cells were CD16+ or CD57+ NK cells among these diseases. Our results suggest that PF and GA are secreted mainly from alpha/beta T cells, and may play a key role in muscle fibre damage in at least some PM and IBM, but not in DM.

High efficiency of muscle regeneration after human myoblast clone transplantation in SCID mice

SCID mouse tibialis anterior muscles were first irradiated to prevent regeneration by host myoblasts and injected with notexin to damage the muscle fibers and trigger regeneration. The muscles were then injected with roughly 5 million human myoblasts. 1 mo later, 16-33% of the normal number of muscle fibers were present in the injected muscle, because of incomplete regeneration. However, > 90% of these muscle fibers contained human dystrophin. Some newly formed muscle fibers had an accumulation of human dystrophin and desmin on a part of their membrane. Such accumulations have been demonstrated at neuromuscular junctions before suggesting that the new muscle fibers are innervated and functional. The same pool of clones of human myoblasts produced only < or = 4% of muscle fibers containing human dystrophin when injected in nude mice muscles. Several of the human myoblasts did not fuse and remained in interstitial space or tightly associated with muscle fibers suggesting that some of them have formed satellite cells. Moreover, cultures of 98% pure human myoblasts were obtained from transplanted SCID muscles. In some mice where the muscle regeneration was not complete, the muscle fibers containing human dystrophin also expressed uniformly HLA class 1, confirming that the fibers are of human origin. The presence of hybrid muscle fibers containing human dystrophin and mouse MHC was also demonstrated following transplantation. These results establish that in absence of an immune reaction, transplanted human myoblasts participate to the muscle regeneration with a high degree of efficacy even if the animals were killed only 1 mo after the transplantation.

Cell and gene therapy in Duchenne muscular dystrophy

Experiments in mice have supported the idea of treating Duchenne muscular dystrophy (DMD) by implanting normal muscle precursor cells into dystrophin-deficient muscles. However, similar experiments on DMD patients have had little success. Gene therapy for DMD, by introducing dystrophin constructs via retroviral or adenoviral vectors, has been shown to be possible in the mouse, but the efficiency and safety aspects of this technique will have to be carefully examined before similar experiments can be attempted in man. Direct injection of dystrophin cDNA constructs into mdx muscles has given rise to very low levels of dystrophin and this may be a possibility for the treatment of heart muscle.

MHC class I, MHC class II and intercellular adhesion molecule-1 (ICAM-1) expression in inflammatory myopathies

We investigated the relationship between the MHC-I, MHC-II and intercellular adhesion molecule-1 (ICAM-1) expression on myofibres and the presence of inflammatory cells in muscle specimens of 18 patients with inflammatory myopathies (nine polymyositis, seven dermatomyositis, two inclusion body myositis). We observed MHC-I expression in muscle fibres, infiltrating mononuclear cells and endothelial cells in every specimen. In seven patients, some muscle fibres were MHC-II-positive for the DR antigen, while the DP and DQ antigens were absent. ICAM-1 expression, detected in seven patients, was found in clusters of myofibres, associated with a marked MHC-I positivity and a widespread mononuclear infiltration. Most of the ICAM-1-positive fibres were regenerating fibres. Furthermore, some fibres expressed both ICAM-1 and DR antigens near infiltrating cells. This finding could support the hypothesis that myofibres may themselves be the site of autosensitization.

Immunomodulation during treatment of polymyositis with plasmapheresis and immunosuppressive drugs

Immunologic studies were carried out in a patient with polymyositis (PM), who showed increasing muscle strength and decreasing serum creatine phosphokinase levels during 20 weeks of treatment with plasmapheresis in conjunction with prednisone and cyclophosphamide. After an initial rise, serum IgG declined with treatment. Natural killer (NK) lymphocytes were reduced by 74%, B cells by 95%, and T cells by 38%. Spontaneous proliferation of peripheral blood mononuclear cells increased dramatically. Within the CD4+ T cell subset there was increasing maturation as shown by a rise in percent mature (CD29+) cells and reciprocal decline of immature (CD45RA+) cells. At the same time CD4+ T cells became increasingly activated as shown by HLA-DR expression. The percentage of CD8+ T cells increased strongly with treatment, and they showed increased activation and expression of the cytotoxic CD29+ and CD11b- phenotypes. CD8+ T cells exhibiting CD45RA or CD11b+ suppressor phenotypes were overall unchanged; however, on follow-up a proportion of CD8+ cells expressed the activated suppressor effector (CD11b-CD28-) phenotype. In addition to control of PM by the possible deletion of activated autoreactive B and T lymphocyte clones with cyclophosphamide, the activation and maturation of CD4+ T cells during treatment may have downregulated the autoreactive disease process, either through direct antiidiotypic suppression or by induction of the observed increase in cytotoxic and suppressor CD8+ T cells.

Myositis in Lyme borreliosis: an immunohistochemical study of seven patients

Myositis is a rare complication of Lyme disease. In order to get information about the pathogenesis of this disorder, muscle specimens of 7 patients suffering from myositis as a manifestation of Lyme borreliosis were examined by immunohistology. Lyme spirochetes could be found in muscle biopsies of 6 patients. Infiltrates consisted mainly of macrophages and T helper/inducer cells. The T4/T8 ratio was 1.7 in the endomysium and 2.1 in the perimysium. Increased expression of MHC-I molecules by several muscle fibers was observed in 2 subjects only. No MHC-II molecules were expressed by muscle fibers. Lymphocytes expressing the interleukin-2 receptor were detected in 2 patients. Leu-15+ and Leu-11+ cells were found only to a slight extent in 2 patients. In conclusion the immunohistochemical findings in myositis due to Lyme borreliosis are different from other manifestations of this disease, and also from other forms of myositis.

Inflammatory Myopathy and Walker-Warburg Syndrome: Etiologic Implications

Walker-Warburg syndrome is a well delineated clinical entity with characteristic brain and eye anomalies. Recent diagnostic surveys have revealed that muscular dystrophy is an obligatory feature of this syndome. We report a patient with an inflammatory myopathy that preceded dystrophic changes. While reports of parental consanguinity and multiple affected sibships strongly suggest an autosomal recessive genetic basis for this syndrome, previous pathological analyses of the CNS have suggested an inflammatory process. Our case supports both the notion of an aberrant inflammatory process that is likely under genetic control or etiologic heterogeneity (phenocopies) underlying this syndrome.

Myoblast transfer in Duchenne muscular dystrophy

One biceps muscle of 8 patients with Duchenne muscular dystrophy was injected at 55 sites with a total of 55 million viable, purified, and contamination-free normal myoblasts (myoblast transfer). The other biceps of each patient was injected with a placebo to serve as a control. The procedure was blinded to the patients, parents, and investigators. Myoblasts derived from a biopsy specimen of the fathers were cultured and purified under strict conditions and carefully screened for microbial contamination. All patients received cyclophosphamide for immunosuppression for 6 or 12 months. No serious complications were observed after myoblast transfer, indicating that the procedure is safe. The overall therapeutic efficiency of myoblast transfer was poor as judged by the results in maximal voluntary force generation, dystrophin content of the muscle, magnetic resonance imaging of the muscle, and the lack of donor-derived DNA and dystrophin messenger RNA in the injected muscle. An improved efficiency of the take of myoblasts might be achieved by using younger cells and injecting the myoblasts with a myonecrotic agent (to increase the prevalence of regeneration) and a basal laminal fenestrating agent.

Analysis of T cell receptor repertoire of muscle-infiltrating T lymphocytes in polymyositis. Restricted V alpha/beta rearrangements may indicate antigen-driven selection

Polymyositis is an inflammatory myopathy characterized by mononuclear cell infiltration of muscle tissue. Myocytotoxic T lymphocytes have been recognized in the infiltrates, but the muscle antigen, target of the immune attack, has not been identified. Molecular characterization of the variable regions of T cell receptors (TCRs) on the infiltrating lymphocytes can be expected to provide insights into the pathogenic process. The V alpha/beta TCR repertoire was investigated by RNA-PCR in muscle biopsies from 15 polymyositis patients and 16 controls (6 Duchenne muscular dystrophy and 10 with no inflammatory or dystrophic myopathy). A variety of rearranged variable TCR genes was found in polymyositis, V alpha 1, V alpha 5, V beta 1, and V beta 15 being the most common (present in 60-100% of patients). In Duchenne muscular dystrophy patients TCR V alpha or beta rearrangements were found although no restriction was observed; no rearrangements were found in muscles from the other controls. Sequence analysis revealed the presence of the J beta 2.1 region in 90% of the V beta 15 clones studied, no random N additions in the diversity region, and a common motif within the CDR3 region. These results suggest that selection of muscle-infiltrating T lymphocytes is antigen driven in polymyositis.

Inclusion body myositis: clinical and histopathological features of 36 patients

Thirty-six patients (15 females, 21 males) with inclusion body myositis (IBM) were studied. The diagnosis was established according to clinical and histopathological criteria. Clinical features were insidious onset of slowly progressive muscle weakness and wasting with depressed or absent tendon reflexes especially in the lower limbs. The pattern of muscle weakness was variable. The majority of patients (58%) showed proximal and symmetrical weakness usually most prominent in the legs. Isolated distal (6%) and asymmetrical weakness (19%) was less frequently observed. Myalgia occurred in 42% of the patients. The age at onset of symptoms ranged from 20 to 73 years (mean 47 years). Serum creatine kinase levels were normal (11%) or mildly elevated (89%). Needle electromyography revealed myopathic features in about 80% of the patients, and results of nerve conduction studies were normal in most of the cases. The predominant histopathological findings were numerous muscle fibers with rimmed vacuoles (100% of the patients), groups of atrophic fibers (92%), and inflammatory infiltrates (89%). The inflammatory infiltrates were located predominantly at endomysial sites and were composed mainly of T8 cells. Electron microscopy showed characteristic intracytoplasmic filamentous inclusions in all 36 cases. Immunosuppressive treatment in 16 patients failed to prevent disease progression in all but one patient with an associated Sjögren's syndrome. It is concluded that the consistent combination of typical histopathological findings and characteristic clinical features offers a firm basis for the diagnosis of IBM. IBM should be suspected in any adult patient presenting with clinical signs of a chronic polymyositis unresponsive to immunosuppressive therapy. The etiology and pathogenesis of IBM remain to be established.

Immunohistochemical characteristics of polymyositis in patients with HTLV-I-associated myelopathy and HTLV-I carriers

The immunohistochemical characteristics of polymyositis in patients with HTLV-I-associated myelopathy (HAM) and HTLV-I carriers were studied. Infiltrating cells were predominantly T cells and were not different from in the control group. All specimens contained positively staining muscle fibers for MHC class I antigens, but class II antigens were also expressed in some muscle fibers in 1 patient with HTLV-I-negative polymyositis, 3 patients with HTLV-I-positive polymyositis, and all 5 HAM patients with polymyositis. Expression of the neural cell adhesion molecule was lowest in the HAM patients. These findings may suggest a different immune environment in polymyositis with HAM.

Gene transfer therapy for heritable disease: cell and expression targeting

Gene therapy is defined as the delivery of a functional gene for expression in somatic tissues with the intent to cure a disease. Different gene transfer strategies may be required to target different tissues. Adenosine deaminase (ADA) deficiency is a good gene therapy model for targeting a rare population of pluripotent hematopoietic stem cells capable of self-renewal. We present evidence for the highly efficient gene transfer and sustained expression of human ADA in human primitive hematopoietic progenitors using retroviral supernatant with a supportive stromal layer. A stem cell-enriched (CD34+) fraction was also successfully transduced. Duchenne muscular dystrophy (DMD) is also a good model for somatic gene therapy. Two of the challenges presented by this model are the large size of the gene and the large number of target cells. Germline gene transfer and correction of the phenotype has been demonstrated in transgenic mdx mice using both a full-length and a truncated form of the dystrophin cDNA. We present here a deletion mutagenesis strategy to truncate the dystrophin cDNA such that it can be accommodated by retroviral and adenoviral vectors useful for somatic gene therapy.

Multifactorial study of inflammatory myopathies. Report of 29 cases

We made a comparative clinical, immunopathological and therapeutic evaluation in 17 patients with polymyositis (PM) and 12 patients with dermatomyositis (DM), followed up at our Neuromuscular Center. DM can be distinguished by its clinical appearance and pathological changes. Current evidence suggests that it results from vasculopathy. For studying these inflammatory myopathies we used multifactorial diagnostic criteria, evaluating the therapeutic response by means of a composite clinical and functional score in a longitudinal study. In muscle biopsy specimens we characterized with monoclonal antibodies T lymphocyte subpopulations (CD4, CD8), macrophages, IgG, IgM, C1q, C3, C4 complement fractions, MHC-I, MHC-II. In PM the cell-mediated immunity was more pronounced and in some cases both MHC-I and MHC-II molecules were found on the surface or within muscle fibers. Our patients were treated with steroids; in resistant cases azathioprine, cyclophosphamide, plasmapheresis, high-dose intravenous immunoglobulins (ivIgG) and total body irradiation were added to the therapeutic schedule.

Expression of 65-kd heat shock proteins in the inflammatory myopathies

In normal muscle, 65-kd heat shock proteins (hsp) were detected on capillary endothelial cells, the mural elements of larger vessels, and some intracellular organelles, probably mitochondria. In the inflammatory myopathies, the 65-kd hsp were detected on inflammatory cells, degenerating and regenerating fibers, and on many but not all nonnecrotic muscle fibers invaded by T cells. The expression of the 65-kd hsp may be an immune-nonspecific response to cellular "stress," but hsp determinants could possibly also serve as autoantigen(s) recognized by autoreactive T cells.

Loss and renewal of thick myofilaments in glucocorticoid-treated rat soleus after denervation and reinnervation

Denervation of rat soleus muscle and simultaneous administration of high doses of corticosteroids for 7 days caused marked muscle fiber atrophy and selective loss of thick myofilaments from many muscle fibers by light and electron microscopy. Myosin heavy chain/actin ratios were greatly reduced on polyacrylamide gel electrophoresis. Nerve crush instead of cut permitted reinnervation after 2 weeks and demonstrated the reversibility of the muscle changes within a week after reinnervation. There was formation of new thick filaments and their reintegration into myofibrils without further breakdown, although large areas of Z-disc streaming appeared. The mechanism of A-band breakdown remains obscure, but it presumably starts with limited proteolysis and continues with disaggregation of myosin molecules. This is consistent with our observation that the muscle fibers retain a relatively good reactivity to antibodies against myosin heavy chain 1 week after denervation and corticosteroid administration. A syndrome recalling these experiments is seen in severely asthmatic patients receiving corticosteroids and pharmacologically paralyzed for mechanical respiration.

Flavivirus induces MHC antigen on human myoblasts: a model of autoimmune myositis?

Infection of human embryonic myoblasts by West Nile virus (WNV), a flavivirus, caused significant upregulation of class I and II MHC expression as determined by flow cytometry. After 48 hours at a multiplicity of infection of 5 pfu/cell, a sixfold increase in MHC class I expression was induced from initially low levels of expression. In contrast, MHC class II was induced de novo to five times the control fluorescence level. At least 70% of the cells were infected as determined using fluorescence microscopy and anti-WNV antibody labeling. Myoblasts were > 90% pure as shown by anti--Leu-19 labeling. MHC class I (but not class II) was increased threefold after exposure to virus-inactivated supernatant from 48-hour--infected cells, indicating the presence of factor(s) contributing to the MHC class I increase. These findings may be important in establishing a link between viral infection of human cells and induction of inflammatory autoimmune disease. We discuss the possibility of using WNV as an in vivo model.

Quantitative morphometric study of muscle in inclusion body myositis

Clinical and electromyographic findings do not clearly distinguish inclusion body myositis (IBM) from chronic polymyositis (PM). The rimmed vacuoles and filamentous nuclear and cytoplasmic inclusions that characterize IBM are often sparse and may be overlooked; conversely, these features may occasionally be seen in other diseases. Preliminary studies suggested that muscle fiber hypertrophy occurred more frequently in IBM than in PM. To investigate whether fiber hypertrophy can be used to improve the ability to separate IBM from PM, we report a morphometric analysis of 28 IBM cases, 22 PM and 22 dermatomyositis (DM) cases. The analysis, using a computer automated system, included proportion of hypertrophied fibers and also fiber type proportions, average fiber diameter, proportion of atrophic and angulated fibers, and the co-dispersion index (CDI). The proportion of hypertrophied fibers was greater in IBM than the other two conditions (IBM (mean +/- SEM) 31.0 +/- 4.7% and 12.2 +/- 2.4% for type 1 and type 2 fibers, respectively, compared to 9.8 +/- 3.0% and 3.3 +/- 1.7% in PM, and 7.7 +/- 2.7% and 3.9 +/- 1.9% in DM). These differences were statistically significant (P < 0.05) in both sexes for type 1 fibers and in women for type 2 fibers. Also, the average fiber size and hypertrophy factors for type 1 and type 2 fibers were increased in IBM compared to PM and DM. This study confirms that the presence of muscle fiber hypertrophy in biopsies from IBM patients may help differentiate them from other clinically similar inflammatory myopathies.

Skeletal muscle toxoplasmosis in patients with acquired immunodeficiency syndrome: a clinical and pathological study

The present article describes the clinical and pathological findings in 5 human immunodeficiency virus (HIV)-infected patients with muscle toxoplasmosis. The patients had marked lymphopenia (5/5), with less than five CD4+ cells/mm3 (3/3), when they developed fever (5/5), and multiorgan failure (5/5), including diffuse encephalitis, pneumonia, pancytopenia, and myopathy. Muscle involvement included weakness and wasting (4/5), myalgias (3/5), and high serum creatine kinase levels (3/3). Serology for toxoplasmosis showed high IgG titers in 3 patients (3/4). Anti-Toxoplasma therapy resulted in complete recovery in 2 patients. Muscle toxoplasmosis was detected by biopsy (3/5) or postmortem evaluation (2/5), and was identified using immunocytochemistry and electron microscopy. Toxoplasma cysts were detected in 0.5 to 4% of muscle fibers close to or remote from necrotic fibers and inflammatory infiltrates. Muscle fibers strongly expressed the major histocompatibility complex class I antigen (2/2) as in polymyositis. We suggest that Toxoplasma gondii should be sought by muscle biopsy in patients who have acquired immunodeficiency syndrome with fever, encephalitis, multiorgan dysfunction, and elevated serum creatine kinase levels of obscure origin.

Challenges: Cell transplantation and gene therapy in muscular dystrophy

Duchenne's muscular dystrophy (DMD), which affects 1/3500 live male births, involves a progressive degeneration of skeletal and cardiac muscle, leading to early death. The protein dystrophin is lacking in DMD and present, but defective, in the allelic, less severe, Becker muscular dystrophy and is also missing in the mdx mouse. Experiments on the mdx mouse have suggested two possible therapies for these myopathies. Implantation of normal muscle precursor cells (mpc) into mdx skeletal muscle leads to the conversion of dystrophin-negative fibres to -positive, with consequent improvement in muscle histology. Direct injection of dystrophin cDNA into skeletal or cardiac muscle also gives rise to dystrophin-positive fibres. Although both appear promising, there are a number of questions to be answered and refinements to be made before either technique could be considered possible as treatments for myopathies in man.

Class II MHC antigens in normal human skeletal muscle

Class II MHC antigen expression has been investigated in muscle tissue and cultured cells from normal human skeletal muscle by light and electron immunocytochemistry. In muscle tissue, these antigens were detected in satellite cells, interstitial cells, and blood vessels. In cultures, muscle cells were stained with a pan-reactive anti-HLA class II antibody and with isotypes specific for DP, DQ, and DR. The staining was present on mononucleated cells and persisted on myotubes; it was stronger for DR and DQ isotypes than for DP. At the subcellular level, staining was located not only at the cell surface, but also next to the endoplasmic reticulum and in the cytosol. Thus, myosatellite cells and aneurally cultured cells from human normal skeletal muscle express class II MHC antigens. Moreover, the myotube staining and the presence of gold particles inside the cells suggested synthesis of these antigens after myoblast fusion.

Vacuolar myositis with expression of both MHC class I and class II antigens on skeletal muscle fibers

We describe here a 10-year-old patient with high levels of serum IgE and inflammatory myopathy whose muscle fibers exhibit excessive autophagy. Previous studies have demonstrated surface expression of class I MHC antigens on muscle fibers from patients with inflammatory myopathy. The muscle fibers of this patients showed marked expression of both class I and class II MHC antigens. The reaction products were demonstrated not only on sarcolemma but also in and around some vacuoles. Both CD4-positive and CD8-positive T-lymphocytes were noted in inflammatory exudates surrounding these fibers but B-lymphocytes were rare. We hypothesize that myocyte expression of both class I and class II antigens may play a role in the pathogenesis of this new type of inflammatory myopathy.

Immunocytochemical and virological characteristics of HIV-associated inflammatory myopathies: similarities with seronegative polymyositis

We performed an immunoperoxidase study on muscle biopsy specimens from 19 patients with polymyositis who were seropositive for human immunodeficiency virus (HIV) (21 specimens) and 5 HIV-seronegative patients with polymyositis and compared the findings. A quantitative analysis of T cells and T-cell subsets, B cells, natural killer cells, interleukin-2 receptor-positive cells, and macrophages was performed on serial sections from all the specimens. Localization of major histocompatibility complex (MHC)-I and -II antigens, alpha and gamma interferon, and HIV antigens (p24, gp120, and gp41) was performed using specific antisera. In specimens from HIV-positive and seronegative patients, the predominant cell population was CD8+ cells and macrophages invading or surrounding healthy muscle fibers that expressed MHC-I antigen on their surface. The endomysial infiltrates in specimens from HIV-positive patients differed from those seen in specimens from the seronegative patients only by a significant reduction of the CD4+ cells (12.6 +/- 3.2% versus 21.1 +/- 4.2%). HIV antigens were seen in occasional interstitial mononuclear cells (but not in muscle fibers) in 6 of the 21 specimens from HIV-positive patients. Interferon was not localized. We conclude that the development of HIV-associated polymyositis does not appear to be related to direct infection of the muscle fibers by HIV but rather is due to a T-cell-mediated and MHC-I-restricted cytotoxic process, perhaps triggered by HIV. Because this immunopathological mechanism is common in both HIV-associated polymyositis and polymyositis alone, it is suggested that viruses may also be responsible in triggering polymyositis.

Invited review: myoblast transfer: a possible therapy for inherited myopathies?

A potential therapeutic strategy for genetic diseases is to alter the genetic constitution of the affected tissues by means of grafts of normal precursor or stem cells. Over several years, evidence has accumulated to suggest that primary diseases of skeletal muscle, such as Duchenne muscular dystrophy, may be susceptible to this approach. This review makes a critical examination of such background evidence, and also of more recent data directly addressing the concept of therapy by means of grafts of normal myogenic cells. It is concluded that the data establish the principle that such grafts effect an alteration of the genetic constitution and phenotype of skeletal muscle and, therefore, might be used to alleviate recessively inherited myopathies. Several obstacles to the therapeutic application of this method to human disease are also identified; these seem to be problems of a technical nature rather than of basic principle, and none appears insuperable.

Allografts of muscle precursor cells persist in the non-tolerized host

Implantation of normal muscle precursor cells into myopathic fibres to alleviate recessively inherited diseases of skeletal muscle has received much attention since the discovery of a defective or deficient gene coding for the protein dystrophin in the Duchenne and Becker forms of muscular dystrophy. Therapeutic allografting of cells would require some means of preventing their immune rejection. Here we have allografted muscle into the non-tolerant and non-immunosuppressed murine host. Precursor cells introduced in the form of a single cell suspension survive for prolonged periods post-implantation. Allografts of minced muscle often failed to survive, even though host and donor were compatible at the major histocompatibility locus. Differences at minor loci may well have contributed to such rejection. Where allografted tissue was rejected, there was a decrease in the amount of surviving host muscle at the graft site, an important observation in terms of the therapeutic implantation of cells.