The rate of trophoblast shedding/deportation alters with increasing gestational age: An in vitro model to quantify trophoblast deportation

ObjectiveTo quantify trophoblast deportation after developing an in vitro model of trophoblast deportation by culturing placental explants in Net-well inserts which allow passage of cells shed from the explants to the lower chamber from where we can harvest, characterize and quantify the shed trophoblasts.MethodsOur original model employed explants from placentae of 12 weeks gestation. Using that model, we estimated about 150 000 trophoblasts would shed daily from a placenta of 12-week gestation. In this study, we determined whether trophoblast shedding is consistent throughout pregnancy. Placental explants from second-trimester and term placentae were cultured in Net-well inserts for 72 hours. Shed cells were characterized by immunocytochemistry and quantified. Published mean placental weights were then used to extrapolate an estimate of the rates of trophoblast shedding in vivo.ResultsSyncytial nuclear aggregates and mononuclear trophoblasts were shed from the second-trimester and term placentae. We also noted the shedding of cytokeratin-positive anucleate “ghosts” which we presume to be derived from syncytial nuclear aggregates. Relative to the numbers of trophoblasts shed from first trimester placentae, the numbers shed from second trimester placentae declined but the number of trophoblasts shed increased again from third trimester placentae.ConclusionWe have shown that the rate of trophoblast shedding is inconsistent throughout gestation confirming the results of others who found variable levels of deported trophoblasts in maternal blood.