Fibroblast growth factor receptor (FGFR)-4, but not FGFR-3 is expressed in the pregnant ovary

Abstract

The intraovarian mechanisms for follicle recruitment, growth, maturation, and ovulation are not well understood. The data suggest that fibroblast growth factor (FGF)-2 is expressed in granulosa and theca cells of growing and mature follicles and in luteal cells during pregnancy. Exogenous FGF-2 modulates steroidogenesis, stimulates tissue plasminogen activator (tPA), and induces germinal vesicle breakdown (GVBD) in cultured follicles. Previously, we have reported that another FGF ligand, FGF-4, is expressed in ovulated mouse oocytes. Two studies have examined the expression of receptors (FGFR) for FGF ligands in the ovary. These prior reports have been limited to FGFR-1, one of the four isoforms that are variably expressed in adult mammalian tissues. This study evaluates FGFR-4 and FGFR-3 mRNA expression in the ovary. Granulosa cells from several follicular stages express the receptor for FGFR-4 mRNA as assayed by in situ hybridization. FGFR-4 mRNA is not expressed in theca cells or the oocyte. FGFR-3 mRNA is not detected in the ovary by in situ hybridization. These results suggest that FGFR-4 may play a role in mediating the effects of FGF ligands in follicular development in the ovary.