Abstract
Heart and neural crest derivatives-expressed transcript 2 (HAND2) is a key transcription factor in progestin-induced decidualization of human endometrial stromal cells (ESCs). In the mouse, HAND2 plays an important role in uterine receptivity by suppressing several fibroblast growth factors (FGFs). However, the regulation of FGF family members by progestin-induced HAND2 and the role of FGF in vascular regeneration in the endometrium remains poorly understood. To investigate these molecular mechanisms, primary human ESCs were cultured with estradiol (E2), medroxyprogesterone acetate (MPA), progesterone receptor (PR) antagonist RU486, HAND2-specific small interfering RNA (siRNA), and recombinant FGF. The expression levels of FGF family members, HAND2, angiopoietin (ANGPT), and vascular endothelial growth factor (VEGF) were assessed by real-time PCR and ELISA. Out of six FGF genes known to be expressed in the human endometrium, only one, FGF9, was significantly downregulated in human ESCs after 3 days of progestin treatment. E2 + MPA attenuated the mRNA and protein levels of FGF9 during decidualization of ESCs, and this effect was blocked by RU486. Silencing of HAND2 significantly increased FGF9 expression in ESCs treated with E2 + MPA. Moreover, FGF9 activated FGF receptor in human ESCs, triggering ANGPT2 production, which resulted in enhancement of the ANGPT2/ANGPT1 protein ratio. Taken together, progestin-PR signaling and its target HAND2 play an essential role in FGF9 suppression in the human endometrium. In addition, progestin-induced HAND2 inhibits ANGPT2 production by suppressing FGF9 in ESCs. These results suggest that HAND2 may contribute to endometrial vascular maturation by regulating FGF9 during decidualization.