Heparin-binding Growth Factor Type One and Platelet-derived Growth Factor Are Required for the Optimal Expression of Cell Surface Low Density Lipoprotein Receptor Binding Activity in Human Adult Arterial Smooth Muscle Cells

Purified heparin-binding growth factor-1 (HBGF-1) stimulated low density lipoprotein binding, internalization, and degradation in isolated human adult arterial smooth muscle cells. Exposure of quiescent cells to HBGF-1 in serum-free, defined medium increased both low density lipoprotein (LDL) receptor activity and de novo cholesterol biosynthesis. Both events preceded the onset of DNA synthesis by 6 to 9 h. HBGF-1 acted additively with platelet-derived growth factor (PDGF) to maximally stimulate cell surface LDL receptor binding activity and DNA synthesis in the smooth muscle cells. The presence of LDL was required for maximal mitogenic activity of HBGF-1 and PDGF. In the presence of LDL, growth factor-stimulated, proliferating human smooth muscle cells accumulated cholesterol ester and triglycerides. The results suggest that HBGF-1, PDGF, and LDL act together to promote the maximal proliferation of smooth muscle cells in culture. Chronic exposure to the three growth promoters may contribute to the smooth muscle cell hyperplasia and lipid accumulation observed in atherosclerotic lesions.