Pituitary-derived Follicle stimulating hormone has greater follicle-stimulating bioactivity than recombinant Follicle stimulating hormone possibly due to glycoform variants

Follicle-stimulating hormone is the primary gonadotropin regulating ovarian follicular development and is widely utilized in assisted reproduction. Our previous research indicated that different glycoforms of the follicle-stimulating hormone Beta-subunit influence follicular development in vivo, but their specific roles across various folliculogenesis stages remained unclear. In this study, we compared two commercial follicle-stimulating hormone preparations: pituitary-derived follicle-stimulating hormone, which contains both fully and hypo- glycosylated Beta-subunit forms, and recombination follicle-stimulating hormone, predominantly consisting of fully glycosylated forms. Using an in vitro follicular culture model, we observed that pituitary-derived follicle-stimulating hormone was more effective than recombination follicle-stimulating hormone in stimulating follicular growth and promoting antrum formation in preantral follicles. Pituitary-derived follicle-stimulating hormone also rescued insufficient preantral follicle growth and antrum formation caused by recombination follicle-stimulating hormone. Besides, pituitary-derived follicle-stimulating hormone more efficiently drove small antral follicle growth than recombination follicle-stimulating hormone. Additionally, pituitary-derived follicle-stimulating hormone significantly increased the granulosa cells proliferation and effectively inhibited apoptosis, thereby protecting growing follicles from atresia. Pituitary-derived follicle-stimulating hormone also induced higher steroidogenesis than recombination follicle-stimulating hormone. Mechanistically, pituitary-derived follicle-stimulating hormone activated key downstream signaling including protein kinase A/cAMP-response element binding protein, mitogen-activated protein kinase/extracellular signal-regulated kinase, and phosphatidylinositol 3-kinase/AKT more efficiently than recombination follicle-stimulating hormone. Importantly, pre-treating antral follicles with pituitary-derived follicle-stimulating hormone significantly improved ovulation rate following human chorionic gonadotropin administration. This was linked to a rapid upregulation of luteinizing hormone/choriogonadotropin receptor expression and enhanced mitogen-activated protein kinase/extracellular signal-regulated kinase signaling activity. Collectively, our data support that pituitary-derived follicle-stimulating hormone, with its mixture of fully and hypo-glycosylated forms, has greater bioactivity in promoting preantral-antral transition, antral follicle growth, and ovulation compared to recombination follicle-stimulating hormone, which mainly consists of fully glycosylated follicle-stimulating hormone. Application of mixed glycoforms or hypo-glycosylated follicle-stimulating hormone may improve the outcomes in assisted reproduction.