Experimental myositis: the in-vivo and in-vitro activity of lymph-node cells

Effect of butylphthalide intervention on experimental autoimmune myositis in guinea pigs

Idiopathic inflammatory myopathies are a group of rare muscular diseases that are characterized by acute, subacute or chronic proximal and symmetric muscle weakness, muscle fiber necrosis and infiltration of inflammatory cells, particularly activated CD8⁺ cytotoxic T cells and phagocytes. 3-n-butylphthalide (NBP) protects mitochondria and reduces the inflammatory response in multiple disease models. In myositis, it has remained elusive whether NBP can protect muscle cells from muscle fiber injury. Experimental autoimmune myositis (EAM) was induced in a total of 40 guinea pigs by myosin immunization. After 4 weeks, low- or high-dose NBP solution was intraperitoneally injected. Saline solution was used as a negative control. After 10 days, the clinical manifestations were assessed by determining rodent grasping power, histopathological changes, Ca²⁺-adenosinetriphosphatase (ATPase) activity by an ATPase kit, and mRNA expression of interferon (IFN)-γ, retinoic acid receptor-related orphan nuclear receptor (ROR)γt and forkhead box (Fox) p3 in muscle tissue by reverse-transcription quantitative polymerase chain reaction analysis. It was demonstrated that NBP improved the myodynamia of guinea pigs with EAM and reduced the pathological inflammatory cell infiltration in a dose-dependent manner. NBP improved the Ca²⁺-ATPase activity of the muscle mitochondrial membrane and muscle plasma membrane in animals with EAM. It also reduced the mRNA expression of IFN-γ and RORγt, and significantly increased the mRNA expression of Foxp3 in muscle tissue. These results provided a basis for the consideration of NBP as a novel agent for the treatment of myositis and other muscular diseases associated with autoimmunity and inflammation.

Laminin-induced autoimmune myositis in rats

The present study aimed to examine if immunization with laminin causes myositis in rats and whether the pathologic findings mirror human polymyositis and dermatomyositis. Rats were immunized with an emulsion of laminin and complete Freund's adjuvant. As a result, muscle fiber necrosis with infiltrating macrophages was frequently observed and mononuclear cells were observed in the endomysium. These mononuclear cells were composed of CD4+ cells, CD8+ T cells, and macrophages. CD4+ cells and CD8+ T cells were mainly located in the endomysium, whereas a large number of macrophages were located in the endomysium and infiltrating muscle fibers. A small number of B cells, detected by immunohistochemical staining, were mainly located in the perimysium. The nonnecrotic muscle fiber to which CD4+ T cells, CD8+ T cells, and perforin+ cells adhered was negative for antimerosin and antidystrophin antibodies. Muscle fiber necrosis in rats immunized with laminin may occur after denaturation of basement membrane proteins. In conclusion, the immunization with laminin induces moderate to severe myositis. We suggest that laminin may be an important antigen for connective tissue diseases such as polymyositis and dermatomyositis.

Animal models of myositis

Current animal models of human myositis include spontaneous, induced, and transgenic models. Although it is clear that none of these models possesses all the features of the human diseases, they may provide insight into the pathophysiologic mechanisms, and possibly the therapy, of inflammatory muscle disease. Because the human IIMs are phenotypically heterogeneous, but may be divided into more homogeneous subgroups based upon clinical or serologic features, it is possible that different pathogeneses are involved in different subgroups. It is unlikely that any single model would reproduce all features of the human disease. It may be possible, however, to gain insight into some subgroups of the human disease if certain animal models faithfully reproduce one or more subtypes or aspects of the IIMs. Because immunogenetic risk factors, and exposure to certain environmental agents important in triggering myositis in genetically susceptible persons, may be necessary components for human disease induction, transgenic approaches to humanizing murine immune systems and a better understanding of environmental risk factors will be productive avenues for future research. Additional investigations into the molecular basis of the human myositis syndromes and the pathogenesis of the spontaneous, induced, and transgenic animal models should ultimately allow for better understanding and therapy of these diseases.

Do immune cells promote the pathology of dystrophin-deficient myopathies?

Many features of dystrophin-deficient muscle pathology are not clearly related to the loss of mechanical support of the muscle membrane by dystrophin. In the present review, evidence that supports a role for the immune system in promoting the pathology of dystrophinopathy is presented. The findings summarized here indicate that specific, cellular immune responses by cytotoxic T-lymphocytes and helper T-lymphocytes contribute to muscle pathology in dystrophin-deficient muscle, and that removal of specific lymphoid cell populations can reduce muscle pathology. In addition, innate immune responses may also promote dystrophinopathies by the tremendous infiltration of myeloid cell populations into the dystrophic muscle. Loss of normal redox homeostasis by dystrophin-deficient muscle may increase its sensitivity to free radical-mediated damage by myeloid cells. Collectively, the observations presented here suggest that the contribution of the immune system to dystrophinopathies may be significant, and that therapeutic approaches based upon immune interventions may ameliorate the pathological progression of dystrophin deficiency.

Experimental autoimmune myositis in SJL/J mice produced by immunization with syngeneic myosin B fraction. Transfer by both immunoglobulin G and T cells

An experimental autoimmune myositis (EAM) was produced by immunizing SJL/J mice with the myosin B (MB) fraction of the syngeneic muscle. Immunoblot analysis of the IgG of the EAM mice demonstrated antibodies against a variety of muscle proteins. The condition was then transferred to normal mice by both injecting immunoglobulin G or T cells from the EAM mice. This is the first model of transferrable EAM caused by syngeneic muscle fraction, and it has an unique resemblance to human inflammatory myopathies involving both humoral and cellular immune mechanisms.

Experimental allergic myositis: ultrastructural, histochemical, immunological and immunohistochemical studies

The quadriceps femoris muscles of experimental allergic myositis, in strain 13 guinea pigs immunised with rabbit myosin B fraction, were subjected to histochemical, immunohistochemical and electron microscopic studies. They demonstrated a variety of degenerative changes of muscle fibres, infiltration of lymphocytes and macrophages along with deposition of immunoglobulin G (IgG) and complement factor 3 on the surface of the muscle fibres. One third of the infiltrating cells were macrophages with acid phosphatase activity in the cytoplasm. The serum IgG of the model had an affinity for the surface of normal guinea pig muscle fibres and for thick filaments and other organelles. Its affinity for the heavy and light chains of myosin, actin, troponin T and for other proteins was shown by the immunoblotting method combined with one- and two-dimensional electrophoreses.

Inflammatory myopathy: a review of etiologic and pathogenetic factors

Human idiopathic inflammatory myopathy is an acquired disorder with an annual incidence of two to five cases per million. A genetic influence on host susceptibility may also play a role. With the marked heterogeneity of the disease one of the major challenges is to identify subsets that might share a more uniform pathogenesis and manifest a less diverse profile of clinical findings, histopathological abnormalities, and natural history. Dermatomyositis can be distinguished by clinical appearance and pathological changes, but the recognition of additional disease subsets remains very inexact. Current evidence suggests that dermatomyositis occurs as a result of a vasculopathy, but immune mechanisms involved in other categories of idiopathic inflammatory myopathy may also involve cell-mediated immunity and possibly multiple mechanisms. Even though viral-induced muscle inflammation occurs in humans, there is no convincing evidence for a viral cause of idiopathic inflammatory myopathy. Experimental allergic myositis may be produced by the injection of animals with skeletal muscle homogenates and complete Freund's adjuvant, but the myositogenic factor is unknown and the parallels between experimental allergic myositis and human idiopathic inflammatory myopathy are limited.

Cerebral aneurysm presenting with epilepsy

Two patients with cerebral aneurysm are reported. Both presented with temporal lobe epileptic attacks. In one of the patients there was a family history of aneurysm and cerebral haemorrhage. One aneurysm was recognized by calcification on a plain radiograph but could not be demonstrated by angiography during life. The aneurysms were large and originated from the middle cerebral artery. Previous reports are reviewed. Difficulties of diagnosis and prognosis are discussed.

Serum IgG levels in the Storrs strain of hereditary muscular dystrophic chickens

IgG levels in sera of Storrs hereditary muscular dystrophic chickens were investigated. IgG levels in age-matched Storrs muscular dystrophic chickens varied, depending on the geographical location where the chickens were reared. IgG levels from muscular dystrophic chickens at varying ages of development were approximately 30% less than age-matched control values. Genetic analyses of F1 hybrid, F2 progeny, and testcross progeny showed the reduced IgG levels in the Storrs strain of muscular dystrophic chickens not to be correlated with the autosomal recessive muscular dystrophic trait, the degree of muscle destruction, nor with an autosomal recessive T cell defect. The studies reported here suggest (1) that the reduced IgG levels in the Storrs strains of muscular dystrophic chickens are due to strain differences and (2) that the mode of inheritance of serum IgG levels in the Storrs strain of muscular dystrophic chickens is polygenic.

Ultrastructural studies in human polymyositis

Biopsy of muscle from 13 cases of human polymyositis permitted an ultrastructural study in which attention was directed to the cellular population of the inflammatory reaction. The constant feature was the presence of small and large lymphocytes, and cells of the latter type were frequently in intimate contact with the surface of the muscle fibres. Macrophages were seen both within and outside degenerating muscle fibres. Plasma cells were seen in 2 cases. Filaments bearing some resemblance to virus inclusions were seen in one case. The implications of the cellular reaction in human polymyositis are discussed and the literature of ultrastructural observations on the muscle in this disease is briefly reviewed.

Polymyositis and myasthenia gravis: immunodeficiency disorders involving skeletal muscle

Human polymyositis and aspects of myasthenia gravis may be consequences of subtle immunodeficiency states. Autoimmune processes leading to inflammatory muscle disease and the presence of associated tumours may reflect the partial loss of antibody-mediated homoeostatic mechanisms.