Endoplasmic reticulum stress in mouse decidua during early pregnancy

• Ire-Xbp1 pathway of unfolded protein response (UPR) is activated in decidual cells.
• Decidualization is compromised by ER stress inhibitor.
• ER stress induces DNA damage and polyploidization in stromal cells.

Unfolded or misfolded protein accumulation in the endoplasmic reticulum lumen leads to endoplasmic reticulum stress (ER stress). Although it is known that ER stress is crucial for mammalian reproduction, little is known about its physiological significance and underlying mechanism during decidualization. Here we show that Ire-Xbp1 signal transduction pathway of unfolded protein response (UPR) is activated in decidual cells. The process of decidualization is compromised by ER stress inhibitor tauroursodeoxycholic acid sodium (TUDCA) and Ire specific inhibitor STF-083010 both in vivo and in vitro. A high concentration of ER stress inducer tunicamycin (TM) suppresses stromal cells proliferation and decidualization, while a lower concentration is beneficial. We further show that ER stress induces DNA damage and polyploidization in stromal cells. In conclusion, our data suggest that the GRP78/Ire1/Xbp1 signaling pathway of ER stress-UPR is activated and involved in mouse decidualization.