Comparative study on the in vitro development of caprine and bovine preantral follicles

The present study aimed to evaluate the effect of the addition of IGF-1 to the in vitro culture (IVC) medium on the development of caprine and bovine preantral follicles ≥150 μm in diameter. Caprine and bovine preantral follicles were cultured for 18 days in the absence or presence of 50 ng/mL IGF-1. Follicles were classified according to morphological characteristics, and those showing morphological signs of degeneration such as darkness of oocytes and surrounding cumulus cells or those with misshapen oocytes were classified as degenerated. Oocyte and follicular diameter were measured only in healthy follicles and antral cavity formation was defined as a visible translucent cavity within the granulosa cell layers. Regarding follicular growth, the daily increase in follicular diameter was calculated, and oocyte extrusion was determined by calculating the rates of ruptured basement membrane with the release of cumulus oocyte complexes (COCs). After IVC, oocytes were submitted to in vitro maturation (IVM) and morphological analysis using fluorescent markers. IGF-1 did not affect follicular morphology and antrum formation in both species. However, follicular extrusion and in vitro matured oocytes were obtained only in caprine. It can thus be said that although bovine and caprine preantral follicles react differently at same culture conditions, this study showed the successful in vitro development of caprine preantral follicles. We also suggest the enrichment of the IVC media and increase in the IVC period for bovine preantral follicles.