Phenotype of the endothelium in the human term placenta

The placental endothelium contributes to regulating transplacental exchange and maintaining the immunological maternofetal barrier. We characterized the endothelial phenotype in human normal term placentae with a panel of antibodies to endothelial antigens using a standardized immunofluorescence method. Placental endothelium strongly expressed vWF, PAL-E, II-antigen, thrombomodulin, PECAM-1, CD34, CD36, ICAM-1, CD44, thy-1, A10/33-1, VE-cadherin, caveolin-1 and HLA-G, increased occludin, claudin-1, eNOS, angiotensin converting enzyme (ACE), ICAM-2, endoglin and integrin-alpha0 beta (3), were weakly expressed. PGI(2) synthase, tissue factor, E-selectin and VCAM-1 were not detected. Some antigens were heterogenously expressed along the vascular tree or within individual villi. Expression of ACE, eNOS, vWF, P-selectin, E-selectin, integrin alpha (v)beta (3) and endoglin was stronger in the maternal decidual vessels, while PECAM-1, CD44, thy-1 and caveolin-1 espression n as stronger in fetal vessels. Some endothelial markers were present in trophoblasts: and stroma. Endothelial proliferation was apparent in mature intermediate and terminal villi. There n as limited inflammatory response to TNF alpha in explants, characterized by upregulation of vWF, beta -selectin, PECAM-1 and CD44, downregulation of thrombomodulin, but no increase in ICAM-1 espression, nor induction of E-selectin, VCAM-1 or tissue factor. These patterns of heterogencity, proliferative activity and inflammatory activation may underlie the specific physiological roles of the placental endothelium. (C), 2001 Harcourt Publishers Ltd.