Identification and purification of an intrinsic human muscle myogenic factor that enhances muscle repair and regeneration

The limited ability of damaged muscle to regenerate after gross injuries is a major clinical problem. To date, there is no effective therapeutic treat ment for muscle injuries. In the present study, we have examined the abilit y of crude and fractionated human skeletal muscle extracts to promote myoge nic cell proliferation and differentiation. It was found that the crude mus cle extract could significantly stimulate BrdU incorporation in C2C12 myoge nic cell line. In addition, the extract also promoted myogenic cell alignme nt and fusion. Using electrophoresis techniques, in conjunction with in vit ro refolding technique, a protein with molecular weight of approximately 40 kDa was identified that could produce the same effects as the crude muscle exdtract. We also tested the ability of semipurified (30-50 kDa) muscle ex tract to promote muscle repair in adult rats. Surgical intervention was use d to induce muscle damage in the tibialis anterior. The semipurified muscle extract (fraction H) was injected subcutaneously over the tibialis anterio r for a period of 5 days. It was found that the damaged muscle fibers were replaced by newly regenerated muscle fibers. These newly regenerated fibers originated from the fusion of differentiated satellite cells as revealed b y BrdU-labeling analysis. In contrast, the injury site of muscles treated w ith BSA control protein contained mainly fibroblasts. (C) 2000 Academic Pre ss.