PDGFB regulates the development of the labyrinthine layer of the mouse fetal placenta

PDGFB is a growth factor which is vital for the completion of normal prenat al development. In this study, we report the phenotypic analysis of placent as from mouse conceptuses that lack a functional PDGFB or PDGER beta gene. Placentas of both types of mutant exhibit changes in the labyrinthine layer , including dilated embryonic blood vessels and reduced numbers of both per icytes and trophoblasts. These changes are seen from embryonic day (E) 13.5 , which coincides with the upregulation of PDGFB mRNA levels in normal plac entas. By E17, modifications in shape, size, and number of the fetal blood vessels in the mutant placentas cause an abnormal ratio of the surface area s between the fetal and the maternal blood vessels in the labyrinthine laye r. Our data suggest that PDGFB acts locally to contribute to the developmen t of the labyrinthine layer of the fetal placenta and the formation of a pr oper nutrient-waste exchange system during fetal development. We point out that the roles of PDGFB/R beta signaling in the placenta may be analogous t o those in the developing kidney, by controlling pericytes in the labyrinth ine layer and mesangial cells in the kidney.