The effects of insulin, and insulin-like growth factors I and II on human ovarian follicles in long-term culture

The aim of this study was to investigate the effects of insulin and insulin -like growth factors I and II (IGF-I and IGF-II) on human ovarian follicles in vitro. Ovarian cortical tissue slices (0.1-0.3 cm) were cultured for 7 or 14 days on an artificial extracellular matrix and with FSH. The ovarian tissue cultures were stimulated by insulin (33 ng/ml), IGF-I (20 or 50 ng/m l) or IGF-II (20 ng/ml). Combined effects of IGF-I (20 ng/ml) or IGF-II (20 ng/ml) and insulin (33 ng/ml) were also studied. Proliferating cell nuclea r antigen (PCNA) was selected for immunohistochemical examination activatio n of the mitotic cell cycle in granulosa cells. After 1 week of culture the number of follicles had decreased in all cases. After 2 weeks of culture t he number of healthy follicles had decreased dramatically in control cultur es. However, the loss of follicles could be prevented with insulin and IGFs . The number of atretic follicles was significantly lower in insulin cultur es compared with control cultures after 2 weeks. The proportion of primary follicles was significantly increased in cultures treated with insulin, IGF -I (50 ng/ml) or IGF-II (20 ng/ml) compared with control cultures after 2 w eeks. A similar effect was seen after co-treatment with IGF-II and insulin. There were significantly more PCNA-positive follicles in IGF-I cultures th an in control cultures. These results suggest that insulin, IGF-I and IGF-I I may act as survival factors for early stage human follicles. IGFs may als o be involved in activation of the mitotic cell cycle of granulosa cells.