ABSTRACT
Development of the human placenta and its different trophoblasts subtypes plays an essential role in determining successful pregnancy outcome. These particular epithelial cells fulll diverse functions such as adaption of the implanted blastocyst to the uterine environment, remodeling of maternal spiral arteries, and nutrition of the developing fetus. Failures in placentation and function of trophoblasts during early stages of gestation are associated with numerous pregnancy diseases such as miscarriage, preeclampsia, and intrauterine growth restriction, eventually affecting health in later life through fetal programming. However, sequential events and regulatory mechanisms controlling human trophoblast development are poorly understood. Because of ethical considerations, our knowledge is based largely on the histological analyses of early placental specimens obtained from pregnant women who underwent hysterectomy. Moreover, analyses of placental tissues from legal pregnancy terminations between the 6th and 12th weeks of gestation provided rst insights into the putative role of regulatory signaling pathways controlling early trophoblast differentiation. In this chapter, we review our present knowledge about localization and the structure of different trophoblast subtypes arising during the rst weeks of gestation. In particular, development of the extravillous trophoblast (EVT) lineage and its invasive subtypes, interacting with different maternal uterine cells, will be discussed. Furthermore, we describe genes and key regulatory mechanisms that could regulate the intrinsic differentiation program of EVT in the placental anchoring villus.
