TIE1 and ovarian hyperstimulation syndrome: Here, we report significantly increased Tie1 and vascular endothelial growth factor (VEGF) expression in cultured granulosa cells from OHSS patients, as well as ovaries from rats with experimentally established OHSS, compared to controls, with the levels of both proteins also increasing in granulosa and SVOG cells (a nontumorigenic human granulosa-lutein cell line) treated with an acute dose of human chorionic gonadotropin (hCG).