Producción in vitro de embriones a partir de complejos cúmulos oocitos tipo II en bovinos Bos indicus

Abstract

The morphological selection of cumulus-oocyte complexes (COCs) is an important step for in vitro embryo production. It has been suggested that COC showing signs of atresia have the ability to generate embryos. The objective of this work was to evaluate the effect of COC morphology from Bos indicus animals with signs of early atresia versus no signs of atresia on in vitro embryo production. COC were classified in: Type I (TI): homogeneous ooplasm with ≥ 4 layers of compact cumulus cells (CC) and Type II (TII): granular ooplasm and ≥ 4 layers of CC slightly expanded. The COC were matured in vitro for 24 hours in TCM199 medium and subsequently fertilized in vitro for 18 h. The suspected zygotes were cultured in vitro for seven days in modified SOFaa medium. Embryonic quality was determined by blastomeric count following staining with Hoechst 33342. Student test was used to determine statistical differences for cleavage, blastocyst rate and blastomeric counts between types of COC. The cleavage rate for TI (n = 220) and TII (n = 161) was 88 ± 4 % and 89 ± 8 % respectively (p> 0.05); embryo development rate was 36 ± 7 % and 33 ± 8 % (p>0.05) respectively. The blastomeric count for both groups was 101 and 104 cells for TI and TII respectively (n = 10), (p>0.05). These results demonstrate that there is no difference in the quantity and quality of embryos produced in vitro using COC type I or type II, suggesting that both types could be used for bovine in vitro embryo production in Bos indicus cows. Resumen La selección morfológica de los complejos cúmulo-oocito (COC) es crucial para la producción de embriones in vitro. Se ha sugerido que COC que mues-tran signos de atresia poseen capacidad de generar embriones. El objetivo de este trabajo fue evaluar el efecto de la morfología de los COC provenien-tes de animales Bos indicus con signos de atresia temprana y sin signos de atresia sobre la producción de embriones in vitro. Se clasificaron COC obte-nidos de ovarios de faenado en dos grupos: Tipo I (TI): ooplasma homogéneo con ≥ 4 capas de células del cumulo (CC) compactas y Tipo II (TII): ooplasma