Growth differentiation factor-11 upregulates matrix metalloproteinase 2 expression by inducing Snail in human extravillous trophoblast cells.

The human extravillous trophoblast (EVT) cell invasion is an important process during placentation. Although the placenta is normal tissue, the EVT cells exhibit some features common to cancer cells, including high migratory and invasive properties. Snail and Slug are transcription factors that mediate the epithelial-mesenchymal transition (EMT), a crucial event for cancer cell migration and invasion. It has been shown that GDF-11-induced matrix metalloproteinase 2 (MMP2) expression is required for EVT cell invasion. Whether GDF-11 can regulate Snail and Slug expression in human EVT cells remains unknown. If it does, the involvement of Snail and Slug in GDF-11-induced MMP2 expression and EVT cell invasion must also be defined. In the present study, using the immortalized human EVT cell line, HTR-8/SVneo, and primary cultures of human EVT cells as experimental models, our results show that GDF-11 upregulates Snail and Slug expression. ALK4 and ALK5 mediate the stimulatory effects of GDF-11 on Snail and Slug expression. In addition, we demonstrate that SMAD2 and SMAD3 are required for the GDF-11-upregulated Snail expression, while only SMAD3 is involved in GDF-11-induced Slug expression. Moreover, our results reveal that Snail mediates GDF-11-induced MMP2 expression and cell invasion but not Slug. This study increases our understanding of the biological function of GDF-11 in human EVT cells and provides a novel mechanism for regulating MMP2 and EVT cell invasion.

Bone morphogenetic protein-9 downregulates StAR expression by inducing snail expression via SMAD1/5/8 signaling in human granulosa-lutein cells.

Ovarian steroidogenesis mediated by granulosa cells is pivotal in maintaining normal female reproductive function. The steroidogenic acute regulatory protein (StAR) regulates the rate-limiting step in steroidogenesis. Bone morphogenetic protein-9 (BMP-9), also known as growth differentiation factor-2 (GDF-2), is a member of the transforming growth factor-beta (TGF-ß) superfamily. BMP-9 induces epithelial-mesenchymal transition (EMT) that contributes to cancer progression. However, the function of BMP-9 in the female reproductive system remains largely unknown. It has been recently shown that BMP-9 is expressed in human follicular fluid and can downregulate StAR expression in human ovarian granulosa cells. However, the underlying molecular mechanisms warrant investigation. Our results show that treatment of primary granulosa-lutein (hGL) cells with BMP-9 downregulates StAR expression. In addition, two EMT-related transcription factors, Snail and Slug, are upregulated by the treatment of BMP-9. Using pharmacological inhibitors and a siRNA-mediated knockdown approach, we show that BMP-9 upregulates Snail and Slug expression by activating SMAD1/5/8 signaling. We also examine the effects of BMP-9 on SMAD-independent signaling pathways, including ERK1/2, p38, JNK, AKT, and CREB. However, none of them is affected by the BMP-9. Moreover, we use gain- and loss-of-function approaches to reveal that only Snail, not Slug, is required for the BMP-9-induced downregulation of StAR expression in hGL cells. This study increases the understanding of the physiology function of BMP-9 in hGL cells and provides important insights into the regulation of StAR expression.

Activation of G protein-coupled estrogen receptor stimulates placental human chorionic gonadotropin expression through PKA-CREB signaling.

The placenta-secreted human chorionic gonadotropin (hCG) is a hormone that plays a critical role in inducing ovarian progesterone production, which is required for maintaining normal pregnancy. The bioavailability of hCG depends on the expression of the beta-subunit of hCG (hCG-ß) which is encoded by the chorionic gonadotropin beta (CGB) gene. G protein-coupled estrogen receptor (GPER) is a membrane estrogen receptor involved in non-genomic estrogen signaling. Estradiol (E2) has been shown to stimulate hCG production. However, the role of the GPER in regulating CGB expression remains unknown. In the present study, our results revealed that treatment with G1 upregulated CGB expression in two human choriocarcinoma cell lines, BeWo and JEG-3, and primary human cytotrophoblast cells. In addition, G1 treatment activated the cAMP-response element binding protein (CREB). Using a pharmacological inhibitor and siRNA-mediated knockdown approach, we showed that the stimulatory effect of G1 on CGB expression is mediated by the protein kinase A (PKA)-CREB signaling pathway. This study increases the understanding of the role of GPER in the human placenta. In addition, our results provide important insights into the molecular mechanisms that mediate hCG expression, which may lead to the development of alternative therapeutic approaches for treating placental diseases.