129 EFFECT OF INSULIN-LIKE GROWTH FACTOR 1 AND FOLLICLE-STIMULATING HORMONE IN A DYNAMIC MEDIUM ON VIABILITY AND FOLLICULAR DEVELOPMENT OF CAPRINE EARLY PREANTRAL FOLLICLES

Abstract

The goal of this study was to investigate the effect of a dynamic medium supplemented with insulin-like growth factor 1 (IGF-1), FSH, or both on the viability, activation and secondary follicle rates and on the follicle and oocyte diameters of caprine preantral follicles submitted to a long-term (16 days of culture) in vitro culture system. Fragments from goat ovaries (n = 16) obtained from slaughterhouse were cultured in α-MEM containing or not containing IGF-1 (50 ng mL^–1), FSH (50 ng mL^–1), or both as a dynamic medium that was added in the first (Day 0 to 8) and second (Day 8 to 16) halves of culture, resulting in 6 treatments: α-MEM alone, IGF-1/IGF-1, FSH/FSH, IGF-1/FSH, FSH/IGF-1 and IGF-1 + FSH/IGF-1 + FSH. Noncultured (fresh control) and cultured fragments were processed for morphological and viability analyses. Follicles within ovarian fragments were mechanically isolated and early-stage follicles were classified as normal or abnormal and primordial, primary, or secondary. The viability of isolated follicles was determined by trypan blue dye and follicles were classified as live or dead. For this experiment, 6240 preantral follicles were analysed. Data for statistical analyses were transformed and submitted to ANOVA using the GLM procedure of SAS, followed by the Duncan test for comparison of means. At Day 8 of culture, more (P < 0.05) follicles in the treatments containing IGF-1 alone or associated with FSH were normal and viable than in the treatments cultured with FSH or α-MEM alone. At Day 16 of culture, the highest (P < 0.05) percentage of viability was observed in the IGF-1/IGF-1 (68%), IGF-1/FSH (68%) and IGF-1 + FSH/IGF-1 + FSH (72%) treatments. However, more (P < 0.05) normal follicles were observed on Day 16 in the IGF-1 + FSH/IGF-1 + FSH treatment (76%) than in all other treatments, except for the IGF-1/FSH treatment (72%). The percentage of follicular activation (primordial to primary) increased (P < 0.05) in all treatments from Day 0 to 8 (mean, 5 to 49%, respectively). The rate of follicular activation increased (P < 0.05) from Day 8 to 16 in all groups, except for the FSH/FSH and IGF-1 + FSH/IGF-1 + FSH treatments. Nevertheless, at Day 16, the IGF-1 + FSH/IGF-1 + FSH treatment had the highest (P < 0.05) percentage of secondary follicles (28%) when compared with the other groups (range, 6 to 17%). Furthermore, the IGF-1 + FSH/IGF-1 + FSH treatment had the largest (P < 0.05) mean follicular and oocyte diameters after 16 days of culture. In summary, follicular morphology and viability were maintained, follicle activation was promoted and secondary follicle formation was stimulated with the association of IGF-1 and FSH. Therefore, our results demonstrate the importance of IGF-1 associated with FSH during the entire long-term culture period on early folliculogenesis in goats.