Endocrine Abstracts

Little is known about the place of insulin-like growth factors (IGFs) in preantral follicle development, although there is considerable evidence that IGFs are important in antral folliculogenesis. In the rat, isolated large preantral follicles developed better when cultured in vitro in the presence of IGF-I than without (Zhao et al 2001). In the same study, reverse transcriptase polymerase chain reaction identified mRNA for IGF-I and the type I receptor in the granulosa/theca cells as well as the oocytes of these follicles. In rhesus monkeys in vivo, exogenous androgens caused an increase in the expression of IGF-I and type I IGF receptor mRNA within the oocyte of primordial follicles (Vendola et al 1999).

We investigated the localisation of type I IGF receptor and androgen receptor proteins in small preantral follicles and stroma of formalin-fixed, paraffin-blocked human cortical ovarian tissue using immunohistochemistry. Staining was performed using avidin-biotin peroxidase and diaminobenzidine chromogenic substrate.

IGF-I receptor protein was localised to the cytoplasm of pre-granulosa cells in primordial follicles and granulosa cells of primary follicles. Protein was not identified in either the oocytes of these small follicles or in the surrounding stroma.

In contrast, androgen receptor protein was located within the nuclei of stromal cells with staining in some areas of stroma being considerably stronger than in others. There was weak nuclear staining in pre-granulosa cells of primordial follicles and granulosa cells of primary follicles.

These results suggest a role for both IGFs and androgens in early folliculogenesis. Androgens are known to be produced by theca cells of antral follicles and possibly by stromal cells. IGF-II is the major IGF in the ovary and can interact with the type I IGF receptor. The location of IGF-I production within the ovary is less clear: follicles may be responding to IGF-I produced elsewhere.

This work was supported by the MRC and approved by the Research Ethics Committees of Imperial College London/Hammersmith, Queen Charlotte's & Chelsea and Acton Hospitals.