Aberrations in stromal signaling, muscle contractility and epithelial architecture underlie poor embryo-implantation outcomes after murine ovarian stimulation

Ovarian stimulation is widely used in assisted reproductive technologies, yet its effects on uterine architecture and embryo implantation remain poorly understood. Using a mouse model, we show that ovarian stimulation or superovulation disrupts pre-implantation luminal epithelial folding and induces aberrant smooth muscle structure and contractile function. These structural defects result in embryo trapping within aberrant longitudinal folds, impaired implantation chamber formation, misalignment of the embryo-uterine axis, and subsequent embryo loss. These ovarian stimulation effects were reversible after rest and restoration of normal estrus cycling. Transcriptomic analysis suggests widespread disruption in the stroma and immune compartments of the stimulated uteri. Pathway analysis revealed significant disruption of stromal extracellular matrix and enhanced probability of stroma-immune communication via collagen signaling. Platelet derived growth factor receptor A (PDGFRA) expression was elevated in both the stroma and smooth muscle of the stimulated uteri. Short-term pharmacological inhibition of PDGFRA in the stimulated uteri prior to implantation fully restored epithelial fold transition and implantation chamber formation and partially restored smooth muscle architecture and contractility. Importantly, PDGFRA protein was also elevated in endometrial biopsies from women undergoing ovarian stimulation when compared to natural cycle biopsies. Together, this study establishes muscle contractions and stromal and smooth muscle PDGFRA signaling as novel non-cell autonomous regulators of uterine epithelial architecture critical for embryo implantation.