MITOGENS FOR ADULT-RAT AORTIC VASCULAR SMOOTH-MUSCLE CELLS IN SERUM-FREE PRIMARY CULTURE

Objective: When vascular smooth muscle cells are dispersed into cultur e in the presence of serum they modulate their phenotype. The aim of t his study was to determine the range of growth factors likely to stimu late replication of medial vascular smooth muscle cells in vivo by exa mining their responses when cultured in the absence of serum. Methods: Freshly dispersed vascular smooth muscle cells from the healthy aorti c media of adult rats were prepared and plated out in cell culture in the absence of fetal calf serum. DNA synthesis by these cells when pla ted onto fibronectin in response to various growth factors and vasocon strictors was analysed by [H-3]-thymidine incorporation. Results: Less than 5% of cells plated on culture plastic spread, but 15-25% of cell s plated onto fibronectin spread and survived for at least 8 d in cult ure. These cells responded to platelet derived growth factor BB homodi mer (PDGF-BB), basic fibroblast growth factor, and epidermal growth fa ctor by stimulating DNA synthesis at least 10-fold compared with cells in the absence of growth factors. Maximum rate of DNA synthesis occur red 36-42 h after addition of 10% fetal calf serum, whereas maximum ra te of DNA synthesis occurred 80-88 h after stimulation with PDGF-BB or basic fibroblast growth factor. By contrast, PDGF-AA homodimer, trans forming growth factor type beta, insulin-like growth factor I, angiote nsin II, and endothelin I did not stimulate DNA synthesis by more than threefold. Conclusions: Freshly dispersed vascular smooth muscle cell s plated onto fibronectin in the absence of serum proliferate in respo nse to PDGF-BB, basic fibroblast growth factor, and epidermal growth f actor by stimulating DNA synthesis. The range of mitogens and the time course of entry into DNA synthesis under these culture conditions sug gest that serum-free culture provides a good model for the responses o f medial vascular smooth muscle cells in vivo.