Résumé :
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Dysferlin is a membrane-anchored protein implicated in plasma membrane repair process. In mammalians, dysferlin deficiency induces persistent sarcolemma disruptions leading to myofiber necrosis and chronic myopathy. Dysferlin myopathy is characterized by non-immune local complement activation with formation of membranolytic attack complex (MAC)/C5b-9 at the surface of non-necrotic myofibers, which could amplify myofiber necrosis process. Aims of study were: (i) to evaluate the sensitivity of dysf-/- myofibers towards complement attack; (ii) to quantify in parallel complement regulators expression in muscle tissues; (iii) to test the protective effects of polyvalent immunoglobulins (IGb) towards complement attack; and (iv) to evaluate the overall effects of sublytic complement and IGb on myogenic cells proliferation and differentiation. Isolated muscle fibers from dysf-/- AJ and Bla/j, and control C57 mice were subjected to in vitro lytic complement attack assay (10%, 4h). Muscle expression of complement regulators CD55, CD46, CD59 and Cr1 was evaluated by qPCR in AJ, Bla/j and C57 mice. Murine myogenic C2C12 cells were exposed to sublytic complement (1 and 2.5%), with or without IGb (0.2 mg/ml). Differentiation was evaluated by qPCR quantification of Myf-5, myogenin and embryonic myosin heavy chain (eMyHC) expression. Dysf-/- mature myofibers displayed increased sensitivity towards complement, which was not related to a decreased muscle expression of membrane-bound complement regulators. When sublytic, C5b-9 markedly impaired myogenic differentiation and proliferation. Polyvalent immunoglobulins (IGb) fully prevented complement-induced myogenic cell necrosis, but may also notably influence myogenic differentiation and proliferation. In conclusion, dysferlin-deficiency makes myofiber more sensitive to complement attack. Since complement impairs myogenesis, its activation may contribute muscle injuries perpetuation in dysferlin myopathy.
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