REDUCED VIABILITY OF HUMAN VASCULAR ENDOTHELIAL-CELLS CULTURED ON MATRIGEL(TM)

Optimal vascular homeostasis requires efficient control of both prolif eration and elimination of vascular endothelial cells. Programmed cell death, or apoptosis, is the main mechanism controlling cell eliminati on, and it is an essential component of vascular formation. Human vasc ular endothelial cells die in vitro, if prevented from obligatory surv ival factors like growth factors or attachment and cell spreading, but very little is known about the mechanisms control ling endothelial ce ll elimination. Signaling from the extracellular matrix affects the be havior and functions of human umbilical vein endothelial cells (HUVECs ), and we have recently demonstrated the beneficial effects of plating on the reconstituted extracellular matrix Matrigel(TM), on the induci ble nitric oxide production of freshly isolated HUVECs. In this work w e observed that cultured HUVECs formed typical capillary-like structur es on Matrigel, but unexpectedly, after 24-48 hours their viability wa s gradually lost. Viability was measured with an assay based on mitoch ondrial reduction of reagent XTT. No decrease in viability was seen in freshly isolated HUVECs or in cultured fibroblasts during this time. It is known that cells often turn into apoptosis if they receive confl icting information from their surroundings, and apparently signaling f rom Matrigel to HUVECs, while at their in vitro proliferating phenotyp e, resulted in launching of the apoptotic machinery. Thus, proliferati ng and differentiated phenotypes of endothelial cells seemed to have d ifferent sensitivity to signals that induce apoptosis. (C) 1998 Wiley- Liss, Inc.