Extraembryonic Mesenchymal Stem Cells (ChV)

Extraembryonic mesenchymal stem cells originate in the extraembryonic mesenchyme layer (stroma) of the chorionic bilayer. The migrating extraembryonic mesenchymal cells migrate to the primary villi and transform them into secondary villi as the mesenchyme expands to the villous tips. These cells give rise to the villous stromal cells and Hofbauer macrophage-like cells of the placenta. In addition, these cells are the source of de-novo placental hemangioblast differentiation, forming both the first fetal capillaries at around 20 dpc and hematopoietic stem cells, which reside in the primitive capillaries. Later, the allantoic vasculature reaches the chorionic plate and fuses to form the more mature fetal vasculature.