A SUBPOPULATION OF SMOOTH-MUSCLE CELLS IN INJURED RAT ARTERIES EXPRESSES PLATELET-DERIVED GROWTH FACTOR-B CHAIN MESSENGER-RNA

Proliferation of smooth muscle cells (SMCs) and formation of a neointi ma are characteristics of the response of rat carotid arteries to ball oon injury. Rat platelet-derived growth factor (PDGF)-B was cloned, th us allowing us to use species-specific probes to carry out in situ hyb ridization on the surface of injured arteries. A distinct population o f luminal SMCs (7% to 10%) in the developing neointima expressed PDGF- B mRNA, but very few luminal SMCs still expressed PDGF-B (0.5%) when t he lesion had stopped growing. Primary SMC cultures revealed expressio n of PDGF-B mRNA in 1.6% of SMCs derived from normal tunica media and in 11% of SMCs derived from the neointima. These data demonstrate that SMCs in the injured vessel wall are heterogeneous with regard to PDGF -B expression and that subculturing of these cells may give rise to cu ltures that are either positive or negative for PDGF-B expression. Fur thermore, with abundant expression of the PDGF receptor beta-subunit e xpressed by intimal SMCs, our findings provide evidence that PDGF-B sy nthesized by these cells may be involved in intimal lesion formation v ia a paracrine or autocrine mechanism.