Proteomic profiling of isolated mouse endometrial epithelial cells reveals coordinated redox and endoplasmic reticulum stress-associated pathways during uterine receptivity.

BACKGROUND AND AIM: Uterine receptivity is critical for successful embryo implantation, yet epithelial-specific proteomic changes during this transition remain incompletely characterized. This study aimed to profile changes in protein expression in isolated mouse endometrial epithelial cells between the pre-receptive (Day 1) and receptive (Day 4) phases of pregnancy to identify key pathways associated with uterine receptivity. MATERIALS AND METHODS: Endometrial epithelial cells were isolated from pregnant CD-1 mice on Days 1 and 4 of pregnancy. Protein extracts were analyzed using two-dimensional gel electrophoresis followed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry for identification. Differentially expressed proteins were functionally annotated using Gene Ontology. Key candidates, including Gstm2 and vimentin, were validated by immunofluorescence and quantitative real-time polymerase chain reaction. RESULTS: Approximately 674 protein spots were detected, of which 80 were differentially expressed (p < 0.05, ≥2-fold change) and 52 were successfully identified. These proteins were primarily associated with cellular metabolism, redox regulation, protein folding, and endoplasmic reticulum (ER) stress responses. Coordinated upregulation of antioxidant proteins (Gstm2, Gstm7, Prdx2, Cat) and ER stress-associated proteins (PDIA3, HSPA5) was observed on Day 4. Gstm2 showed consistent upregulation at both protein and transcript levels (p < 0.05) with enhanced epithelial localization, while vimentin expression remained stable, supporting cytoskeletal readiness. These changes indicate integrated redox homeostasis and stress adaptation during the acquisition of uterine receptivity. CONCLUSION: This epithelial-specific proteomic analysis reveals coordinated redox and ER stress-associated pathways during the transition to uterine receptivity in mice. The findings provide a focused proteome resource that highlights Gstm2 as a candidate regulator within antioxidant networks and establishes a foundation for understanding molecular mechanisms at the embryo-maternal interface.