Insulin-like growth factor binding proteins in ovarian follicles from women with polycystic ovarian disease: cellular source and levels in follicular fluid.

Abstract

The follicular fluid (FF) of human ovaries contains insulin-like growth factor binding proteins (IGFBPs) which may regulate the bioavailability of the IGFs. Previously we showed discrete changes in IGFBP concentrations in FF which correlated with the physiological state of the follicle. The purpose of the present study was to test the hypothesis that IGFBPs in FF may be increased in polycystic ovarian disease (PCO). FF was aspirated from PCO follicles and size matched healthy and atretic follicles from normal ovaries of naturally cycling women. The IGFBPs in FF samples were studied by ligand blot analysis with 125I-IGF-II and by immunoblot analysis using specific antisera to five human IGFBPs. Of six IGFBP bands in PCO FF, three were identified as IGFBP-2, IGFBP-3, and IGFBP-4. Bands (29K and 31K) were not identified by any of the five IGFBP antisera. The total IGF binding capacity was increased in PCO FF relative to normal healthy or atretic FF. IGFBP-3 was the predominant BP present in FF from PCO follicles as well as normal healthy and atretic follicles with no significant difference in any of the groups of follicles studied. IGFBP-2, IGFBP-4, and the 29K BP were present in smaller amounts, but there were significantly higher levels of each of these BPs in PCO follicles than in normal healthy follicles. Only IGFBP-4 was elevated in PCO follicles relative to normal atretic follicles indicating that the pattern of IGFBP expression in PCO FF was very similar to the pattern observed in atretic follicles. To determine the source of the IGFBPs in FF, granulosa or theca cells were cultured (up to 6 days) in serum-free medium. Ligand blot analysis of the conditioned medium revealed basal secretion of IGFBP-3 by both theca and granulosa cells. FSH inhibited granulosa cell IGFBP-3 production but increased the 29K BP in the medium. Transforming growth factor-beta stimulated basal IGFBP-3 secretion and reversed the FSH effects. Human CG (100 ng/mL) inhibited theca cell IGFBP-3 production but did not stimulate any other IGFBP. The results of our studies indicate that IGFBP-2, IGFBP-4, and the 29K BP are significantly increased in PCO FF and that gonadotropins and TGF-beta regulate the production of IGFBPs by human theca and granulosa cells.