ONTOGENY OF FOLLICLE-STIMULATING-HORMONE RECEPTOR GENE-EXPRESSION IN ISOLATED HUMAN OVARIAN FOLLICLES

FSH stimulates antral follicles to grow, but its role in earlier stage s, 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-b ased strategy to analyze single follicles ranging from primordial to m ultilaminar stages after isolation from human ovaries. Ovarian tissue was obtained from 11 women (age range, 25-33 yr) undergoing elective c esarean section. Tissue was partially disaggregated in medium containi ng 1% collagenase, and follicles were manually dissected free of strom a. Follicle stages were confirmed microscopically as primordial (nongr owing), 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 amplifie d by nested PCR using primers for FSHr and actin. None of the 9 primor dial follicles expressed FSHr mRNA. Thirty-three percent of the primar y 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 fo llicles was significant. This study shows for the first time that tran scription of the FSHr gene begins at the earliest stages of follicular growth and indicates that FSH may have a hitherto unsuspected physiol ogical role in preantral follicle development. In addition, this study demonstrates the practical feasibility of investigating the expressio n of other genes during human folliculogenesis.