Effects of growth-factor combinations on vascular endothelial cell growth in vitro.

Abnormal elevation of growth factors in ocular fluid and serum has been claimed to be a major positive regulator of diabetic retinopathy. In this study, we aimed to explore the individual and collective actions of insulin, insulinlike growth factor I (IGF-I), vascular endothelial growth factor (VEGF), and transforming growth factor-beta (TGF-beta) on the proliferation of vascular endothelial cells. Thus, primary human umbilical vein (HUVECs) endothelial cells (ECs) were used to examine their effects by direct viable cell counting and cell-proliferation assay. Insulin, IGF-I, and VEGF individually increased both cell number and proliferation status in a dose-dependent fashion. TGF-beta significantly potentiated the stimulatory effects of insulin and VEGF on EC proliferation, but revealed no synergism with double and triple growth-factor combinations. Our findings emphasize the complexity of the role of TGF-beta in the regulation of EC proliferation. TGF-beta plays an important role in the EC proliferation and the pathogenesis of diabetic retinopathy.