Immunohistochemical localization of basic fibroblast growth factor (bFGF) during folliculogenesis in the human ovary

Basic fibroblast growth factor (bFGF) has been suggested to be one of the intraovarian regulators of ovarian folliculogenesis, but its localization in the human ovary remains to be determined. We examined the immunohistochemical reactivity for bFGF in the course of follicular development and corpora lutea formation in the human ovary. Pregranulosa cells in the primordial follicle were negative, but at the preantral stage both granulosa and theca cells showed weakly positive immunostaining for bFGF. In the antral follicles, both granulosa and theca interna cells showed stronger staining for bFGF with the increase in follicular diameter. In atretic follicles at various stages, granulosa cells were negative or weakly positive for bFGF, whereas luteinized theca cells showed strong immunoreactivity. In the corpora lutea during the early luteal phase, granulosa lutein cells were strongly positive for bFGF but in the late luteal phase became immunonegative. On the other hand, bFGF staining in theca lutein cells was strong throughout the course of corpora lutea formation and regression. These findings suggest that bFGF is localized not only in granulosa cells but also in theca cells, and in the latter, bFGF immunoreactivity is associated with luteinization.