Mouse hepatic endothelial cells in culture secrete a growth inhibitor for hepatic lipocytes and Balb/c 3T3 fibroblasts.

Hepatic lipocytes are sinusoidal cells in close contact to endothelial cells. They proliferate, switch to a fibroblastic phenotype and synthetize collagen during hepatic fibrosis. Since it is known that vascular endothelial cells can influence the proliferation of neighboring cells such as smooth muscle cells, we investigated the role of hepatic endothelial cells on the growth of lipocytes and Balb/c 3T3 fibroblasts. Concentrated conditioned medium from endothelial cells inhibited both [3H]thymidine incorporation and actual growth of lipocytes and Balb/c 3T3 fibroblasts. The inhibition was lost when conditioned medium was treated with heat or trypsin, or when medium was conditioned in the presence of cycloheximide. We conclude that hepatic endothelial cells secrete a proteic growth inhibitor for lipocytes and hepatic Balb/c 3T3 fibroblasts. This inhibitor could be of importance in limiting lipocyte proliferation in the liver and possibly in preventing hepatic fibrosis.