L26/P-541 Glutamine deficiency impairs embryo emplantation by upregulating QRICH2 to suppress GYS1 in endometrial organoids

Abstract Study question Is impaired glutamine metabolism the cause of recurrent implantation failure? Summary answer Glutamine deficiency upregulates the sensor QRICH2 in RIF endometrium, which suppresses the glycogen synthase GYS1, impairing glycogen accumulation and compromising embryo adhesion capacity. What is known already Glucose and glutamine are essential energy substrates for embryo implantation. Insufficient glucose or glutamine disrupts endometrial proliferation and differentiation, thereby compromising endometrial function and consequently leading to implantation failure.Endometrial receptivity defects characterize recurrent implantation failure (RIF), and altered endometrial metabolism is believed to contribute to impaired receptivity. Nevertheless, it is still not understood precisely how key nutrient-sensing regulators control the pathways leading to receptivity. Study design, size, duration Using a laboratory-based approach, we established endometrial organoids from 6 RIF patients (defined by ≥ 3 implantation failures) and 6 controls without known endometrial pathology. Samples from donors with endometriosis or endometritis were excluded. The study combined proteomic profiling, ¹³C metabolic flux analysis, and molecular/functional assays in organoid and cell line models. Participants/materials, setting, methods We established endometrial organoids from clinical samples and performed proteomic analysis to compare RIF and control groups. The function of glutamine and QRICH2 was validated in Ishikawa cells subjected to glutamine deficiency. GYS1 expression was measured via qPCR and Western blot. Additionally, we employed an in vitro implantation assay to assess the adhesion of human trophoblast stem cell–derived blastoids to an endometrial epithelial layer. Main results and the role of chance Proteomic analysis identified QRICH2 as one of the most significantly upregulated proteins in RIF patients. Its expression was elevated in secretory-phase endometrial organoids from RIF patients, as well as in Ishikawa cells under glutamine deficiency. Consistent with this, ¹³C metabolic flux analysis revealed a dysregulated TCA cycle (arrested at the isocitrate node) and inhibited glutamine metabolism in RIF organoids. Furthermore, both QRICH2 overexpression and glutamine deprivation significantly suppressed GYS1 expression. Correspondingly, RIF organoids exhibited lower GYS1 levels and impaired glycogen synthesis. Finally, blastoid adhesion was markedly compromised under glutamine-deficient conditions. Collectively, these results indicate that QRICH2 upregulation in the endometrium of RIF patients may disrupt glutamine metabolism, downregulate GYS1, and thereby impair glycogen synthesis, ultimately leading to embryo implantation failure. Limitations, reasons for caution The primary findings are based on in vitro organoid and cell line models, which may not fully recapitulate the complex in vivo endometrial microenvironment. The sample size for organoid derivation was limited. The precise molecular mechanism by which QRICH2 suppresses GYS1 requires further investigation. Wider implications of the findings This study identifies a novel nutrient-sensing pathway (glutamine-QRICH2-GYS1) critical for human endometrial receptivity. It provides a mechanistic link between metabolic alterations and implantation failure in RIF, highlighting QRICH2 and endometrial glycogen metabolism as potential diagnostic markers or therapeutic targets to improve implantation outcomes. Trial registration number No