Hypoglycosylated hFSH has greater bioactivity than fully glycosylated recombinant hFSH in human granulosa cells

Abstract

Context: Previous studies suggest that aging in women is associated with a reduction in hypoglycosylated forms of FSH. Objective: Experiments were performed to determine whether glycosylation of the FSH beta subunit modulates the biological activity of FSH in human granulosa cells. Design and Setting: Recombinant human FSH (hFSH) derived from GH(3) pituitary cells was purified into fractions containing hypoglycosylated hFSH(21/18) and fully glycosylated hFSH(24). The response to FSH glycoforms was evaluated using the well-characterized, FSH-responsive human granulosa cell line, KGN at an academic medical center. Interventions: Granulosa cells were treated with increasing concentrations of fully-or hypoglycosylated FSH glycoforms for periods up to 48 hours. Main Outcome Measure(s): The main outcomes were indices of cAMP-dependent cell signaling and estrogen and progesterone synthesis. Results: We observed that hypoglycosylated FSH21/18 was significantly more effective than fully glycosylated FSH24 at stimulating cAMP accumulation, protein kinase A (PKA) activity, and cAMP response element binding protein (CREB) (S133) phosphorylation. FSH21/18 was also much more effective than hFSH(24) on the stimulation CREB-response element-mediated transcription, expression of aromatase and STAR proteins, and synthesis of estrogen and progesterone. Adenoviral-mediated expression of the endogenous inhibitor of PKA, inhibited FSH21/18- and FSH24-stimulated CREB phosphorylation, and steroidogenesis. Conclusions: Hypoglycosylated FSH21/18 has greater bioactivity than fully glycosylated hFSH24, suggesting that age-dependent decreases in hypoglycosylated hFSH contribute to reduced ovarian responsiveness. Hypoglycosylated FSH may be useful in follicle stimulation protocols for older patients using assisted reproduction technologies.