Expression of apoptosis related proteins in normal and diseased muscle: a possible role for Bcl-2 in protection of striated muscle.

The unique absence of major histocompatibility complex class I antigen (MHC-I) expression in normal muscle is one possible mechanism protecting striated muscle. In order to define their possible involvement in protection of normal muscle, we investigated the expression of molecules involved in muscle fibre death and survival mechanisms (Bcl-2, Fas, Fas-ligand and TRAIL), focusing on disorders with possible involvement of cytotoxic T cells. We studied muscle biopsies from 20 healthy volunteers, from 10 patients affected by polymyositis and 10 by Duchenne muscular dystrophy. By using immunohistochemistry, Western blot and real-time PCR we detected a constitutional expression of Bcl-2 in healthy muscle, whereas the expression was weaker in disease processes. Fas-L and TRAIL were not detected in muscle fibres, and Fas only in muscle affected by disease. Our findings indicate that the major apoptotic protein Bcl-2 might have a hitherto unrecognized role in the protection of normal muscle.