Human vascular endothelial cells in culture: Lack of response to serum growth factors

Abstract

DNA synthesis was studied in primary cultures of human umbilical cord vein endothelial cells using autoradiography. Sparse populations of endothelial cells synthesized DNA in vitro and divided until confluence was reached. Confluent endothelial cells stopped dividing and could not be stimulated to synthesize DNA by the addition of fresh serum. The inability of confluent endothelial cells to synthesize DNA was found using sera prepared from fetal calf, adult human, and human umbilical cord blood and with media containing serum concentrations ranging from 0 to 100%. These confluent endothelial cells were viable since they migrated into wounds made in a monolayer and subsequently synthesized DNA. The confluent cells also excluded trypan blue. In contrast, cultures of other cells such as human foreskin and BALB/C-3T3 mouse fibroblasts were readily stimulated to synthesize DNA at confluence by the addition of calf or human serum. The extent of the stimulation was dependent on the serum concentration. We conclude that human umbilical cord vein endothelial cells exhibit a stringent pattern of growth control in vitro since confluent cultures do not respond to serum growth factors. It is suggested that this unique property of endothelium may be necessary for the maintenance and function of blood vessels in vivo.