Role of the basement membrane in the regeneration of skeletal muscle.

In many experimental models of skeletal muscle damage and in human muscle disease, empty basement membrane tubes remain following the destruction of muscle fibres. In the present study we test the hypothesis that the empty basement membrane tubes play an essential role in the orientation of regenerating muscle fibres. Two groups of 15 Wistar rats were used. In one group, aqueous barium chloride (BaCl2) solution was injected into the right quadriceps muscle; in the other group, freshly prepared 2% trypsin solution was similarly injected. The different stages of muscle cell necrosis and regeneration were observed by histology, by immunofluorescence using an anti-basement membrane antibody, and by transmission (TEM) and scanning electron microscopy (SEM) in animals killed 1-77 days following injection. Although there was muscle fibre necrosis at sites of BaCl2 injection, empty basement membrane tubes were well preserved. Myoblasts grew along the empty basement membrane tubes and by 77 days, the regenerated muscle fibres at the site of the injection were well oriented. Trypsin not only destroyed muscle fibres but also destroyed the basement membrane tubes; in the early stages of regeneration the myoblasts were disorientated but by 77 days, regeneration was comparable to that seen in the barium chloride injected muscle. The results of this study suggest that preservation of empty basement membrane tubes is not essential for the orientation of regenerating myoblasts in skeletal muscle.