A factor implicated in the myogenic conversion of nonmuscle cells derived from the mouse dermis

Using the mdx mouse model for human Duchenne muscular dystrophy we have sho wn that a cell population residing in the dermis of C57Bl/10ScSn mouse skin is capable of converting to a myogenic lineage when implanted into the mdx muscle environment. It was important to determine the characteristics of t he converting cell. A previous in vitro study indicated that 10% of cells u nderwent conversion but only when the cells were frown in medium previously harvested from a myogenic culture. In the present study we cloned cells de rived from the dermis to identify the converting cells. Clones grown in nor mal growth medium showed no conversion, but when grown in medium conditione d by muscle cells around 40% conversion was achieved in several individual clones. We investigated whether the protein beta-galactoside binding protei n (beta GBP), which is secreted by myoblasts and acts as a cell growth regu lator of fibroblasts, could be a candidate factor responsible for conversio n. Medium harvested from COS-1 cells infected with a construct containing b eta GBP has been used for this investigation. Growth of dermal fibroblasts in medium enriched with this factor showed a high rate of conversion to cel ls expressing muscle-specific factors.