Expression of growth factor receptors on arterial smooth muscle cells. Dependency on cell phenotype and serum factors Original Research Article

The effects of modulation of rabbit aortic smooth muscle cells (SMCs) from the ‘contractile’ phenotype on surface membrane receptors binding epidermal growth factor (EGF), basic fibroblast growth factor (bFGF) and platelet-derived growth factor-BB (PDGF-BB), as well as their responsiveness to these growth factors was investigated in cell culture. Cells predominantly of the ‘contractile’ phenotype expressed low numbers of high affinity EGF and bFGF receptors (EGFr: 1.09 ± 0.18 fmol/106 cells; bFGFr: 0.32 ± 0.07 fmol/106 cells). Upon modulation from the ‘contractile’ phenotype, the expression of these cell surface receptors increased greatly: 8- and 11-fold with respect to EGF and bFGF receptors. Cell surface receptors binding [125I]-PDGF-BB were largely unaltered. The elevated bFGF receptor number appeared dependent on SMC modulation from the ‘contractile’ phenotype and serum; the latter factor did not influence EGF receptor numbers. In both instances the increase in receptor numbers was independent of the proliferative status of the cells. Cells expressing high levels of the growth factor receptors also rapidly entered the cell cycle, proliferated, and exhibited growth factor-specific changes in shape in the presence of these growth factors. Because the effects on growth factor receptor numbers were observed in confluent cells, such alterations are likely to play a significant role in vessel remodelling following balloon catheter angioplasty, in atherosclerotic vessels and the vascular hypertrophy associated with hypertension.