Response to platelet-derived growth factor by phenotypically different cultured human aortic smooth muscle cells.

We investigated the effects of PDGF on DNA synthesis and mitogen-activated protein (MAP) kinase activity, and demonstrated that the adult intimal SMC was concentration-dependently stimulated by all PDGF isoforms in terms of both [3H]thymidine incorporation and MAP kinase activation, with PDGF-BB and -AB being more potent than PDGF-AA. The intimal SMCs and the neonatal SMCs showed a similar response with regard to MAP kinase activation. On the other hand, the intimal SMCs expressed many more PDGF receptors than the adult medial SMCs, which expressed a greater amount of PDGF-A chain mRNA and showed a lesser response to PDGFs. These results suggest that the intimal SMCs have a relatively high potential to react to exogenous PDGFs, whereas the adult medial SMCs depend on endogenous or autocrine secretion of PDGF-AA.