Fibroblast products adsorb to the culture substrate and stimulate growth of human umbilical vein endothelial cells.

Human umbilical vein endothelial cells grew with a doubling time of approximately 20 hr in medium conditioned by human diploid fibroblasts and supplemented with 10% fetal bovine serum, whereas the cells did not grow substantially in the non-conditioned serum supplemented medium. Production of the fibroblast-derived activity required the presence of insulin, EGF, or PDGF. The fibroblast derived-factor adsorbed to native culture dishes or dishes coated with gelatin and collagen. The adsorbed activity was resistant to treatment with 1% Triton X-100, and was abolished by treatment with serine proteases. Further, the extracellular matrix produced by the fibroblasts also showed growth-stimulating activity. Fibroblast-derived factors may play a role in vascularization processes during wound healing, inflammation and normal development.