YWHAZ loss is associated with endometrial dysfunction in proliferative-phase endometriosis.

Endometriosis is an estrogen-dependent inflammatory disorder frequently associated with infertility and characterized by progesterone resistance and impaired endometrial receptivity. While ectopic lesions define the disease, accumulating evidence indicates that molecular abnormalities within the eutopic endometrium substantially contribute to infertility. In this study, we performed transcriptomic analysis of proliferative-phase eutopic endometrium from women with and without endometriosis and identified 44 dysregulated genes, including 13 upregulated and 31 downregulated genes, in women with endometriosis compared with controls. Among the significantly altered genes, YWHAZ (14-3-3 zeta) emerged as a prominently downregulated gene. Reduced YWHAZ expression was further validated at the protein level in both epithelial and stromal compartments of the endometrium from women with endometriosis. To investigate its physiological regulation, we examined YWHAZ expression during early pregnancy in mice and observed a dynamic, stage-specific pattern during the peri-implantation period, with strong expression at gestational days 3.5 and 4.5 and robust expression at the primary decidual zone at gestational day 5.5. Notably, YWHAZ expression was nearly abolished in uteri from progesterone receptor knockout and uterine signal transducer and activator of transcription 3 conditional knockout (Pgrcre/+Stat3f/f) mice, indicating that YWHAZ is dependent on intact progesterone receptor and STAT3 signaling. Together, these findings identify YWHAZ as a hormonally and transcriptionally regulated endometrial factor that is disrupted in endometriosis and tightly linked to implantation and decidual progression. This study highlights YWHAZ as a potential molecular node connecting progesterone resistance and STAT3 dysregulation to defective endometrial function and infertility in endometriosis.