Development of a Ligand Trap to Inhibit Follicle-Stimulating Hormone

Abstract

Follicle-stimulating hormone (FSH) is essential for ovarian folliculogenesis and female fertility. After menopause, pituitary-derived FSH rises and stays elevated, while estrogen levels decline. Although controversial, some studies claim that chronically elevated FSH drives menopausal co-morbidities, including increased adiposity and decreased bone mass. To investigate whether FSH acts in extragonadal tissues, this study aimed to develop a soluble receptor-based trap to bioneutralize FSH in circulation. The ligand trap is a homodimeric Fc-fusion construct containing two copies of the hormone-binding domain of the human FSH receptor (hFSHR-HBD) fused to the IgG Fc domain. The Fc domain confers solubility to the ligand trap in serum and dimerization, whereas the hormone-binding domain is designed to sequester FSH, thereby blocking or attenuating its actions. To generate an expression construct for recombinant protein production, the hFSHR-HBD was PCR amplified and ligated into an Fc expression vector. The recombinant hFSHR-HBD-Fc construct was transformed into bacteria for plasmid amplification and purified before transfection into mammalian cells. Protein expression in cells was confirmed by western blot. However, the protein was not secreted into the cell culture media for reasons we have not yet determined. Future efforts will focus on optimizing protein expression and secretion by modifying different elements of the vector. If successful, this ligand trap could effectively neutralize FSH, serving as a powerful tool to investigate the hormone’s systemic effects.