Growth stimulating activity from lysed cultured arterial smooth muscle cells and skin fibroblasts

Rabbit and bovine arterial smooth muscle cells (SMC) and human skin fibroblasts were lysed by freezing and thawing in the presence of protease inhibitors (PI). The supernatant was assayed for growth stimulating activity (GSA), and it stimulated the growth of SMC and fibroblasts, but not human and bovine endothelial cells. GSA was sensitive to heat and trypsin treatment, stimulated DNA synthesis after a lag time of 12-15 hours, and exhibited marked size and charge heterogeneity when subjected to gel chromatographies. GSA differed from many other known growth factors, mainly platelet derived growth factor (PDGF), through the behavior on ion exchange chromatography, the heat sensitivity and the lack of decline in activity in the presence of anti PDGF antibodies. The data suggests that several growth stimulating proteins can be obtained through the lysis of SMC or fibroblasts with possible implications for atherosclerosis and wound healing.