Muscle regeneration and cell-mediated cytotoxicity in the autologous muscle culture of dermatomyositis

Muscle culture from a dermatomyositis patient was performed to investigate the muscle regeneration and cell-mediated cytotoxicity. In the primary culture, spindle-shaped mononuclear myoblasts exponentially increased in number. In the secondary culture, the myotubes fused with the myoblasts and/or other myotubes into large thick syncytia. The cell morphology and growth pattern of the cultured muscle cells in dermatomyositis were identical to those of normal healthy controls. The autologous mononuclear cells added in the secondary culture of day 14 adhered to the surface membrane of the myotubes. Three days after this treatment, the myotubes underwent degenerative changes. On the other hand, in two series of sister cultures, each added with the autologous serum and control medium, no remarkable morphological changes were observed. The results of the present study suggest that dermatomyositis could be precipitated by the associated abnormal cell-mediated cytotoxicity, but not by abnormalities in muscle fibers per se.