Ontogeny of follicle-stimulating hormone receptor gene expression in isolated human ovarian follicles.

FSH stimulates antral follicles to grow, but its role in earlier stages, if any, is obscure. Our aim was to determine the follicle stage at which the FSH receptor (FSHr) gene is first expressed. We used a PCR-based strategy to analyze single follicles ranging from primordial to multilaminar stages after isolation from human ovaries. Ovarian tissue was obtained from 11 women (age range, 25-33 yr) undergoing elective cesarean section. Tissue was partially disaggregated in medium containing 1% collagenase, and follicles were manually dissected free of stroma. Follicle stages were confirmed microscopically as primordial (nongrowing), primary (1 layer of cuboidal granulosa cells), or having 2 or more layers of granulosa cells. Rectus muscle and stromal tissue were used as negative controls. Messenger ribonucleic acid (mRNA) from each follicle was reverse transcribed, and the resulting cDNA was amplified by nested PCR using primers for FSHr and actin. None of the 9 primordial follicles expressed FSHr mRNA. Thirty-three percent of the primary and 2-layer follicles were positive for FSHr mRNA (4 of 12 and 3 of 9, respectively), as were 100% (n = 4) of the multilaminar follicles. The difference in FSH expression between the growing and primordial follicles was significant. This study shows for the first time that transcription of the FSHr gene begins at the earliest stages of follicular growth and indicates that FSH may have a hitherto unsuspected physiological role in preantral follicle development. In addition, this study demonstrates the practical feasibility of investigating the expression of other genes during human folliculogenesis.