Balance of insulin and FSH concentrations improves the in vitro development of isolated goat preantral follicles in medium containing GH

The aim of this study was to evaluate the effect of different combinations of insulin and FSH concentrations in culture media containing GH on the in vitro follicle morphology, antrum formation, growth rates, estradiol (E2) production, oocyte viability and maturation as well as gene expression for FSHR, GHR, INSR, CYP19A1, CYP17, 3ßHSD. Secondary follicles were individually cultured for 18 days in a basic medium containing 50 ng/mL GH supplemented with low insulin concentration (INS-LW: 10 ng/mL) or high insulin concentration (INS-HG: 10 μg/mL) alone or with a fixed FSH concentration (FSH100: 100 ng/mL) or with increasing FSH concentrations (FSH-SEQ: 100 ng/mL, days 0–6; 500 ng/mL, days 6–12; 1000 ng/mL days 12–18). In the INS-LW treatment was observed a higher (P < 0.05) incidence of normal follicles at day 18 of culture. However, overall higher (P < 0.05) follicular growth, oocyte diameter and meiotic resumption rates were obtained using INS-HG + FSH 100. The INS-HG and INS-HG + FSH100 treatments showed higher E2 production and mRNA levels for CYP19A1, CYP17, 3βHSD when compared to INS-LW and INS-LW + FSH100. However, the addition of increasing FSH concentration, regardless of insulin concentration, did not improve the follicular growth, meotic resumption, E2 production or gene expression of steroidogenic enzymes when compared with INS-HG + FSH100. In conclusion, in presence of GH, a basic medium supplemented with 10 μg/mL insulin and 100 μg/mL FSH throughout the culture period, improves follicular and oocyte growth, oocyte meiotic resumption and E2 production from isolated preantral caprine follicles cultured in vitro.