Expression of receptors for insulin-like growth factor-I and transforming growth factor-beta in human follicles

The in-vitro growth of immature oocytes in early follicles from cryopreserv ed human ovarian tissues is a new concept in in-vitro fertilization program mes for the treatment of infertile and cancer patients. To better understan d the regulatory mechanism of follicular development, immunohistochemistry was used to study the expression of insulin-like growth factor (IGF) type I receptor (IGF-IR) and transforming growth factor-beta (TGF beta) type I (T beta R-I) and type II (T beta R-II) receptors in fresh and frozen ovarian tissues from 14 women. Immunoreactivities for IGF-IR and T beta R-I were pr esent simultaneously in the oocytes of primordial, pre-antral and antral fo llicles. Staining for both IGF-IR and T beta R-I was also observed in granu losa cells of primordial, pre-antral and antral follicles. IGF-IR and T bet a R-I also stained in thecal cells of pre-antral and antral follicles. Stro mal cells in surrounding ovarian tissue expressed IGF-IR and T beta R-I at various follicular stages. Unlike T beta R-I, T beta R-II was expressed onl y in the oocytes of primordial and primary follicles, and with weak stainin g intensity in thecal cells. No significant staining for T beta R-II was fo und in oocytes and granulosa cells of antral follicles. There was no differ ence in staining patterns far IGF-IR, T beta R-I and T beta R-II between fr esh and frozen ovarian tissues, indicating that cryopreservation might not significantly alter the immunoreactivities of these receptors in frozen ova rian tissue. The results suggest that IGF-I and TGF beta may participate in the regulation of follicular growth by binding to their receptors through an autocrine or paracrine mechanism. IGF-I and TGF beta may be useful in re gulating the in-vitro or in-vivo maturation of oocytes not only in later fo llicles but also very early follicles, from cryopreserved ovarian tissues f or clinical use in the future.