Effects of long-acting recombinant human follicle-stimulating hormone analogs containing N-linked glycosylation on murine folliculogenesis

Abstract

To evaluate the efficacy of two novel long-acting rhFSH analogs, rhFSH-N2 and rhFSH-N4, in stimulating murine folliculogenesis. Experimental study. Academic research environment. Immature female mice. Recombinant hFSH-N2 and -N4 were administered via single IP injection to 3-week-old female mice (n = 10) who were killed 48 hours later for dissection and histologic examination of reproductive organs and serum inhibin A. Results were compared with other groups of mice who received either single or q 12 hour injections for 48 hours of commercial rhFSH, or a single injection of pregnant mare serum gonadotropin (PMSG). A subgroup of the mice receiving rhFSH-N4 was supplemented with daily injections of small doses of hCG to simulate LH add-back. Serum inhibin A levels, ovarian and uterine weights, and ovarian antral follicle counts. Recombinant human FSH-N2 and -N4 administration induced a statistically significant increase in ovarian weights, uterine weights, and inhibin A levels compared with single and twice-daily injection of rhFSH. PMSG induced the greatest increases in all three measured parameters. There was no statistical difference between rhFSH-N2 and rhFSH-N4 for any parameter analyzed. A single injection of rhFSH-N2 or -N4 induced a greater number of antral follicles than did either single or q 12 hour injections of rhFSH. The addition of small doses of hCG to rhFSH-N4 increased inhibin A levels and antral follicle number to reach statistical equivalence to PMSG treatment. Addition of a synthetic polypeptide containing two or four N-linked glycosylation sites to rhFSH increases in vivo bioactivity of the hormone compared to commercial rhFSH. After a single injection, both rhFSH-N2 and rhFSH-N4 effectively induced a greater follicular response in the mouse than did rhFSH.