The placenta is a transient, highly organised tissue that facilitates nutrient and waste exchange for the developing fetus. Defective placentas are life-threatening for both mother and baby. Due to ethical restrictions, research on human placental development must be conducted using animal models. However, animal models do not recapitulate all the relevant features of human placental biology, limiting the value of these studies. Currently, the only other method to model human placenta is in vitro tissue explants of term placentae or cultured cells derived from choriocarcinomas. As a direct consequence of the limited ways available to model human placental development, we know very little about early placental development in humans.
Human embryonic stem cells (hESC) can be induced to form placenta-like cells including cytotrophoblast and syncytiotrophoblast (1-3). To take the next step toward placental development in vitro, we have begun to grow hESC-differentiated trophoblast-like cells in a 3D structure that resembles human placental villi. Using 3D-printing technology, we have created polydimethylsiloxane (PDMS) “villi moulds”. Using a combination of published differentiation methods (1-3) we have established a reproducible differentiation method to generate trophoblast-like cells from hESC. These trophoblast-like cells appear to have a nuclear morphology similar to in vivo retrieved cytotrophoblast and syncytiotrophoblast and additionally express human placental markers. We have found that trophoblast-like cells grow together in subpopulations, suggesting that hESC-derived human trophoblast cells can self-organise into 3D structures in vitro. We will present results from our ongoing research which focuses on optimising the culture of trophoblast-like cells generated from hESC as 3D “villi” and discuss the potential applications of this technique in studying villi formation, trophoblast differentiation and the formation of syncytial “knots” in vitro.