The long term objective of this project is knowledge of the mechanisms of regulation of smooth muscle cell differentiation. Modulation of the smooth muscle cell phenotype, in vivo is associated with wound repair, trauma, and cardiovascular diseases. We propose to use a cell culture system to study gene expression, in smooth muscle cells, as they undergo phenotype modulation. We propose to test the hypothesis that modulation is mediated by extracellular factors that are synthesized and secreted by smooth muscle cells. The factors act in an autocrine manner initiate gene activation. Particular emphasis is on the glycoprotein fibronectin, a secreted glycoprotein (38k Da protein), and an activity (nodule stimulating activity) that may have relevance to this problem. Analysis of the genes coding for those proteins to understand the regulation of the modulation process.