Figure 1.

Human placenta development. Blastocyst implantation is mediated by the crosstalk between the blastocyst and the receiving endometrium. Early differentiated syncytiotrophoblast, displaying an invasive phenotype, allows the blastocyst to implant inside the endometrial stroma. Cytokines, growth factors, hormones, oxygen, extracellular matrix, and ROS all modulate trophoblast cell invasion of maternal decidua and myometrium and their capacity to transform spiral arteries. Many growth factors and cytokines, such as EGF, TGF-β, and TNF-α, secreted by the decidua and uNK cells act in a paracrine manner to regulate trophoblast function. These factors may also be secreted by the trophoblast cells and act in an autocrine manner to promote invasion.