The molecular determinates of endometrial physiology in reproductive failure

Abstract

Successful pregnancy is critically dependent on the remodelling of the EnSCs into specialized decidual EnSCs and the establishment of endometrial receptivity. Disruptions in these processes are associated with complications such as RPL and unexplained infertility. While DJ-1 is implicated in neurodegeneration, its role in pregnancy remains unknown. Ca²⁺ signaling and the endometrial expression of infertility factor LEFTY2 also play key roles in embryo implantation, with LEFTY2 negatively regulating receptivity. However, the molecular mechanisms linking these pathways remain to be elucidated. In the first study, we used systems biology, functional studies, and bioinformatics to investigate the role of DJ-1 during early pregnancy. DJ-1 expression in both human and murine endometrium was examined during the window of implantation, and its functional role was further analyzed through knockdown and overexpression experiments. The results revealed that DJ-1 expression increased during early pregnancy, with its loss associated with pregnancy failure. Furthermore, DJ-1 knockdown led to increased ROS production, increased Palladin expression, and enhanced cell stiffness and cell motility, with these effects being reversed upon DJ-1 overexpression. In the second study, human embryo conditioned medium was used to assess trypsin levels and their association with infertility. The effect of LEFTY2 on trypsin-induced Ca²⁺ entry was investigated in human endometrial epithelial cells through qRT-PCR, immunofluorescence, and Fura2 fluorescence for quantifying intracellular Ca²⁺ ([Ca²⁺]ᵢ) levels. The results demonstrated that trypsin released by the blastocyst facilitated successful pregnancy by promoting [Ca²⁺]ᵢ entry through L-type Ca²⁺ channels in endometrial cells. Furthermore, LEFTY2 inhibited trypsin-induced Ca²⁺ entry by blocking the expression of nifedipine-sensitive L-type Ca²⁺ channel. These findings highlight the indispensable roles of DJ-1 in maintaining decidual cytoskeletal integrity and LEFTY2’s interference with trypsin-induced Ca²⁺ signaling in modulating endometrial functions. These results provide insight into recurrent pregnancy loss and unexplained infertility, offering potential therapeutic targets to improve pregnancy outcomes and IVF success rates.