Basic fibroblast growth factor induces primordial follicle development andinitiates folliculogenesis

The recruitment of primordial follicles to initiate folliculogenesis determ ines the population of developing follicles available for ovulation and dir ectly regulates female reproductive efficiency. In the current study, a flo ating organ culture system was used to examine the progression of primordia l (stage 0) follicles to developing (stages 1-4) follicles in 4-day-old pre -pubertal rat ovaries. Basic fibroblast growth factor (bFGF) was found to i nduce primordial follicle development similar to what has been demonstrated for kit ligand/stem cell factor (KL). The bFGF-treated ovaries contained 8 5% developing follicles compared with 50% developing follicles for control untreated organ cultures. Correspondingly, the number of primordial follicl es in bFGF-treated ovaries decreased to 15% of the total compared with 45% for controls. A bFGF neutralizing antibody was found to decrease the small amount of spontaneous follicle development that occurs during the organ cul ture. Basic FGF was localized to primordial and early developing follicles by immunocytochemistry and was primarily observed in the oocytes. Treatment of bovine ovarian theca cells and stroma cells with bFGF was found to prom ote cell growth. Basic FGF produced by the oocyte in early stage follicles appears to act on adjacent somatic cells to promote cell growth and develop ment. Basic FGF, like KL, appears to be a primordial follicle-inducing fact or. In summary, bFGF can regulate primordial follicle development that dire ctly influences female reproductive efficiency. (C) 2001 Elsevier Science I reland Ltd. All rights reserved.