The effect of placental syncytiotrophoblast microvillous membranes from normal and pre‐eclamptic women on the growth of endothelial cells in vitro

Objectives To determine if placental syncytiotrophoblast microvillous (STBM) membranes contain factors which could cause the maternal endothelial cell disturbance thought to be central to the pathophysiology of the maternal syndrome of pre‐eclampsia. Design STMB membranes isolated from pre‐eclamptic or normal placentae were added to cultures of endothelial cells and their effect on the proliferation (measured by ³H‐thymidine incorporation), viability (measured by ⁵¹Cr release) and growth as a monolayer of these cells was determined. Membranes prepared from red blood cells, and nonendothelial adherent and nonadherent cell lines were used as specificity controls. Subjects STBM membranes were isolated from the placentae of primigravid women, 10 having caesarean sections for breech presentations and 10 for pre‐eclampsia. Results STBM membranes from the placentae of normal and pre‐eclamptic women suppressed endothelial cell proliferation to a similar extent and disrupted the cell monolayer to form a honeycomb‐like pattern. This change in morphology was seen before significant endothelial cell death occurred. Red blood cell membranes had no effect on either endothelial cell proliferation, viability or monolayer integrity. Endothelial cells from human umbilical arteries and bovine adrenal capillaries were similarly suppressed, but comparable concentrations of STBM membranes had no effect on nonendothelial cell lines. Conclusions Syncytiotrophoblast microvillous membranes specifically interfered with endothelial cell growth in vitro. Our results demonstrate that there are trophoblast products which could cause the maternal syndrome of pre‐eclampsia through endothelial cell damage.