Oocyte-specific Ahr deletion disrupts folliculogenesis and female fertility in mice

The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that regulates various biological processes, including xenobiotic metabolism, immune response, and reproduction. Although previous studies have shown that AHR plays a role in ovarian follicle development, the precise role of oocyte-expressed AHR in female reproduction remains unclear. In this study, oocyte-specific Ahr knockout (cKO) mice generated by crossing the Ahr ^flox/flox (Ahr ^fl/fl) and Gdf9-cre transgenic mouse strains were used to answer this open question. The cKO female mice exhibited a disrupted estrous cyclicity and subfertility. Histological analyses demonstrated that oocyte AHR loss reduces the number of primary follicles while increasing the number of secondary follicles and corpus lutea in mouse ovary. Hormonal analysis revealed decreased serum estradiol and follicle-stimulating hormone, indicating a disruption of the hypothalamic-pituitary-gonadal axis in cKO mice. TUNEL and Western blotting results demonstrate that deletion of oocyte AHR also results in increased apoptosis in ovarian granulosa cells (GCs), downregulated expression of Gdf9 and Bmp15 in oocytes, and disrupted bidirectional oocyte-GC communication. In conclusion, our findings reveal that the aryl hydrocarbon receptor plays a role beyond sensing environmental chemicals and endogenous compounds and underscore a critical role of oocyte-expressed Ahr in maintain follicle development, ovarian function, and female reproductive health.