APOPTOSIS AND FAS EXPRESSION IN HUMAN FETAL MEMBRANES

Apoptosis (i.e. programmed cell death) plays a key role in maintaining reproductive function in the ovary, mammary and prostate glands, uter us, and testis. The purpose of the present report was to determine, ba sed on biochemical and morphological parameters, whether cells in huma n fetal membranes undergo apoptosis and express Fas (CD95), a cell sur face receptor that mediates apoptosis. Using the terminal deoxynucleot idyl transferase deoxy-UTP-nick end labeling immunohistochemical techn ique, apoptotic nuclei were identified in amnion epithelial, chorionic trophoblast, and decidua parietalis cell layers of human fetal membra nes at term. Electron microscopy of fetal membranes revealed ultrastru ctural characteristics in amnion epithelium and chorion trophoblast ce ll layers consistent with apoptosis, including condensation of chromat in along the periphery of the nucleus and nuclear shrinkage. The apopt otic index (percentage of terminal deoxynucleotidyl transferase deoxy- UTP-nick end labeling-positive nuclei of the total nuclei) ranged from 8-29% in amnion epithelial, chorionic trophoblast, and decidual cell layers from women at 23-30, 31-36, and 37-42 weeks gestation. The apop totic index was statistically greater in the 37-42 week group than in the 23-30 week group in chorionic trophoblast (P < 0.05) and decidual cell (P < 0.01) layers. In contrast, the apoptotic index in the amnion epithelial cell layer was statistically greater (P < 0.05) in the 23- 30 week group than in the 31-36 week group, suggesting that apoptosis may be independently regulated in amnion epithelial, chorionic trophob last, and decidual cell types. Based on the importance of Fas in media ting apoptosis, we investigated whether Fas was expressed by human fet al membrane cells. Immunohistochemical staining of fetal membranes wit h anti-Fas antibody localized Fas in amnion epithelial, chorionic trop hoblast, and decidua parietalis cell layers. A 266-bp band correspondi ng to the cytoplasmic domain of Fas was detected in samples of amnion, chorion, decidua, and placenta by RT-PCR. Northern blotting revealed a molecular weight of approximately 1.9 kilobases for Fas messenger ri bonucleic acid in amniotic tissue. These data suggest that apoptosis a nd Fas signaling may play a role in remodeling of fetal membrane archi tecture across gestation.