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 shown that a cell population residing in the dermis of C57B1/10ScSn 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 the converting cell. A previous in vitro study indicated that 10% of cells underwent conversion but only when the cells were grown in medium previously harvested from a myogenic culture. In the present study we cloned cells derived from the dermis to identify the converting cells. Clones grown in normal growth medium showed no conversion, but when grown in medium conditioned by muscle cells around 40% conversion was achieved in several individual clones. We investigated whether the protein β-galactoside binding protein (βGBP), which is secreted by myoblasts and acts as a cell growth regulator of fibroblasts, could be a candidate factor responsible for conversion. Medium harvested from COS-1 cells infected with a construct containing βGBP has been used for this investigation. Growth of dermal fibroblasts in medium enriched with this factor showed a high rate of conversion to cells expressing muscle-specific factors.