The base medium affects ultrastructure and survival of bovine preantral follicles cultured in vitro.

The aim of this study was to determine the effectiveness of minimum essential medium alpha modification (α-MEM), tissue culture medium 199 (TCM-199), and McCoy's medium (McCoy's) on IVC of preantral follicles included in the bovine ovarian cortex (in situ). Bovine ovarian fragments were cultured in α-MEM, TCM-199, or McCoy supplemented ((+)) with glutamine, insulin, transferrin, selenium, ascorbic acid, BSA, penicillin, streptomycin, and HEPES buffer in 24-well plates, at 37 °C and 5% CO2 for 1 or 7 days. The morphology of follicles, normal, primordial and development (primary and secondary), as well as viability and morphometric variables of follicles and oocytes were assessed. The morphology and morphometry of preantral follicles were analyzed by ANOVA followed by the Tukey and Dunnett tests, and viability variables were determined by the chi-square test. The results showed that TCM-199(+) reduced significantly (P < 0.05) the percentage of morphologically normal and viable follicles after 7 days of culture compared to the control. Similar results were observed in McCoy(+), in which the percentage of viable follicles after 7 days of culture was significantly lower (P < 0.05) than in the control. However, it was similar (P > 0.05) between α-MEM(+) and TCM-199(+). Moreover, follicular diameters in McCoy(+) and TCM-199(+) were significantly smaller (P < 0.05) than in control and α-MEM(+) after 7 days of culture. In addition, the ultrastructure of preantral follicles was similar between the control and α-MEM(+) after 7 days of culture. In conclusion, α-MEM(+) showed to be the most effective medium to preserve morphology, morphometry and ultrastructure of bovine preantral follicles, ensuring their viability and growth after in situ culture.