ROLE OF EGF-LIKE DOMAIN 7 (EGFL7) IN PLACENTAL DEVELOPMENT AND IMPLANTATION.

Objectives: Implantation and placental development are essential for the patterning of the embryo, for its growth and survival upon implantation, as well as for preserving the health of the fetus and mother. Inadequate invasion of trophoblast cells into the maternal decidua and the deficient growth of fetal blood vessels are actually recognized as possible pathogenetic factors of preeclampsia (PE). To examine molecular mechanisms that control these events, we are focusing in our studies on the endothelial gene Egfl7. Our preliminary studies show that Egfl7 has a critical role in molecular processes that control human vascular development and proper placental implantation: in particular, Egfl7 is expressed in the trophectoderm and in the fetal placental vasculature. To assess the involvement of Egfl7 in the development of PE, we investigate the EGFL7 expression patterns between PE and control placentas. Materials and Methods: Two study groups are considered: (1) a first of women with pregnancies complicated by early onset PE ; (2) a second study group of healthy women. The placental biopsies were obtained immediately after caesarean section from both groups, the PE patients and the normal controls. Real-time PCR and immunofluorescence analysis of EGFL7 expression in normal and preeclamptic human placental tissue were performed. Results: Real-time PCR analysis revealed that EGFL7 is strongly down regulated in the villi of PE placentas when compared to normal samples. In agreement with published data, VEGF expression was also decreased in PE placentas, although to a lesser extent compared to EGFL7. At variance, expression of the pan-endothelial marker CD31 was not significantly altered in PE as compared to normal placentas. These results were confirmed by immunofluorescence analysis. Conclusion: Our results suggest a role for Egfl7 in the pathogenesis of PE. We hypothesize that in PE placental villi the total number of endothelial cells is not significantly decreased (as indicated by the unchanged expression of CD31), but that their spatial distribution and function is severely affected, possibly due to the decrease in EGFL7 and VEGF protein. These preliminary results implicate a role for Egfl7 in PE human placentas: our preliminary studies also show that it interacts with the Notch pathway. The Notch signaling pathway appears to be crucial for both placental implantation and development and targeted mutations on several pathway genes result in defective growth of vascular vessels. To test our hypothesis, further studies are necessary in order to assess the importance of Egfl7 in human placental development and preeclampsia and to examine if Egfl7 function in human placenta is mediated through its interactions with Notch.