Growth and differentiation factor - 9 (GDF-9) increases the in vitro growth rates of isolated goat early antral follicles

This study aimed to investigate the effect of growth and differentiation factor 9 (GDF-9) during the in vitro culture of isolated caprine early antral follicles. The isolated and selected early antral follicles were individually cultured for 18 days, and the following treatments were tested: α-MEM ⁺ (control treatment) or α-MEM ⁺ supplemented with 200 ng/mL GDF-9. The following endpoints were evaluated: follicular growth and morphology, estradiol production, oocyte nuclear maturation, and relative expression of key genes related to steroidogenesis (CYP19A1, CYP17, and insulin receptor) and basement membrane remodeling (MMP-9 and TIMP-2). In both treatments, a decrease was observed in the percentage of morphologically intact follicles with a concomitant increase in the rates of extruded and degenerated follicles (P < 0.05). The GDF-9 treatment showed higher rates of extruded follicles only on day 6 of culture (P < 0.05). Follicle diameter increased progressively throughout the culture period (P < 0.05) with similar diameters between treatments at all culture times (P > 0.05). Growth and differentiation factor 9 increased the daily growth rate from the first to the second third of culture, with higher values (P < 0.05) than control in the second third. Oocyte maturation rate as well as estradiol levels and relative mRNA expression for CYP19A1, CYP17, MMP-9, TIMP-2, and insulin receptor genes were similar between treatments (P > 0.05). This study shows for the first time that GDF-9 added to a culture medium increased the follicle growth rate of goat early antral follicles cultured in vitro.