Effects of IGF‐1 on In Vitro Culture of Bovine Preantral Follicles are Dose‐Dependent

Abstract

This study aimed at assessing the effect of different concentrations of the growth factor similar to insulin 1 (IGF-1) in the development, survival and ultrastructure of the bovine preantral follicles cultured insitu. Fragments of bovine ovarian cortical tissue were cultured during 1 and 7days in 1ml of α-MEM(+) , supplemented with different concentrations of human recombinant IGF-1 (0, 30, 70 and 100ng/ml), in an incubator at 37°C and 5% of CO2 in 24-well plates with total replacement of the medium every 2days. Non-cultured ovarian fragments (control) and ovarian fragments cultured during 1 and 7days were processed for classic histology, mechanical isolation and electron transmission microscopy (ETM). Parameters such as normality, viability, activation, development, diameter and ultrastructure were evaluated. All statistical analyses were carried out using sas Version 9.2. The results showed that the percentage of follicles morphologically normal in the IGF-1 30ng/ml treatment was similar to the fresh control (p>0.05) both on the day 1 and on the day 7 of invitro culture. In the viability analysis, the cultured treatments maintained the percentage of viable follicles during the entire culture period (p>0.05). After 7days of culture, the IGF-1 30ng/ml treatment showed higher percentages of developing follicles (48.33%) than those of the fresh control (22.22%) and the cultured treatments (p<0.05). Also, after 7days of culture, IGF-1 30ng/ml presented a higher follicular diameter when compared to the control and other concentrations of IGF-1 tested. Ultrastructurally, the non-cultured control and IGF-1 30ng/ml, after 7days of culture, showed conserved oocytes, nuclei and organelles. Hence, it is concluded that IGF-1 30ng/ml was the most efficient concentration for the development of bovine preantral follicles cultured invitro.