During early pregnancy, cytotrophoblast cells differentiate into extravillous trophoblast (EVT) cells and invade the uterine spiral arteries. This physiological process is essential for the development of maternal-fetal circulation. Since EVT cells are exposed to a low-oxygen environment during this process, we investigated the role of hypoxia in the mechanism that regulates the invasive behavior of EVT cells.

Real-time PCR and immunofluorescent analysis were performed to investigate how hypoxia influences the expression of E-cadherin in villous explants cultures and in trophoblast-derived BeWo cells. We determined that hypoxia induced E-cadherin down-regulation through Snail up-regulation in villous explant cultures. The influence of E-cadherin loss was examined by analyzing the expression of ₅-integrin and phosphorylated FAK by Western Blot and by evaluating trophoblast invasion using a Matrigel Invasion Assay. E-cadherin loss induced the up-regulation of ₅-integrin, which leads to the tyrosine phosphorylation of FAK, resulting in an increase in the invasive activity of EVT cells. An ₅-integrin neutralizing antibody inhibited the invasion of EVT cells by attenuating FAK tyrosine phosphorylation. Immunohistochemical analysis using clinical placental bed biopsies revealed that ₅-integrin was up-regulated and FAK tyrosine-phosphorylated (Try⁸⁶¹) as EVT cells invade the uterine myometrium, whereas E-cadherin expression was down-regulated.

These results suggest that ₅-integrin up-regulation induced by E-cadherin loss under hypoxia has a crucial role in regulating the migration of EVT cells. This finding should help us reach a better understanding of the pathogenesis of critical gestational diseases, such as preeclampsia.