TGF-β1 inhibits human trophoblast cell invasion by upregulating kisspeptin expression through ERK1/2 but not SMAD signaling pathway

Background: Tightly regulation of extravillous cytotrophoblast (EVT) cell invasion is critical for the placentation and establishment of a successful pregnancy. Insufficient EVT cell invasion leads to the development of preeclampsia (PE) which is a leading cause of maternal and perinatal mortality and morbidity. Transforming growth factor-betal (TGF-beta 1) and kisspeptin are expressed in the human placenta and have been shown to inhibit EVT cell invasion. Kisspeptin is a downstream target ofTGF-beta 1 in human breast cancer cells. However, whether kisspeptin is regulated by TGF-beta 1 and mediates TGF-beta 1-suppressed human EVT cell invasion remains unclear. Methods: The effect of TGF-beta 1 on kisspeptin expression and the underlying mechanisms were explored by a series of in vitro experiments in a human EVT cell line, HTR-8/SVneo, and primary cultures of human EVT cells. Serum levels of TGF-beta 1 and kisspeptin in patients with or without PE were measured by ELISA. Results: TGF-beta 1 upregulates kisspeptin expression in HTR-8/SVneo cells and primary cultures of human EVT cells. Using pharmacological inhibitor and siRNA, we demonstrate that the stimulatory effect ofTGF-beta 1 on kisspeptin expression is mediated via the ALK5 receptor. Treatment with TGF-beta 1 activates SMAD2/3 canonical pathways as well as ERK1/2 and PI3K/AKT non-canonical pathways. However, only inhibition of ERK1/2 activation attenuates the stimulatory effect of TGF-beta 1 on kisspeptin expression. In addition, siRNA-mediated knockdown of kisspeptin attenuated TGF-beta 1-suppressed EVT cell invasion. Moreover, we report that serum levels of TGF-beta 1 and kisspeptin are significantly upregulated in patients with PE. Conclusions: By illustrating the potential physiological role of TGF-beta 1 in the regulation of kisspeptin expression, our results may serve to improve current strategies used to treat placental diseases.