The pleiotropic function of PPARγ in the placenta

At different stages of placental development the cytotrophoblasts differentiate into specialized cells that are vital for specific placental tasks. These types include the invasive trophoblasts, which are responsible for invasion of the placenta into the uterine wall, and syncytiotrophoblasts, which form a barrier between the maternal and fetal circulations, govern trans-placental transport of gas, nutrient and waste, and produce placental hormones. Recent research illuminated the role of the nuclear receptor peroxisome proliferator-activated receptor-γ (PPARγ) in the areas of adipocyte and macrophage biology, insulin action, bioenergetics and inflammation. It was somewhat surprising that PPARγ was also found to play a pivotal role in placental biology. In this review we summarize recent data, which show that PPARγ is expressed in the placenta, particularly in trophoblasts, and is essential for placental development, trophoblast invasion, differentiation of cytotrophoblasts into syncytium, and regulation of fat accumulation in trophoblasts. PPARγ may also play a role in modulating fetal membrane signals toward parturition. The data presented here underscore the need for a focused investigation of the unique aspects of PPARγ function in trophoblasts, which may have direct implications for the use of PPARγ ligands during pregnancy.