摘要
The number of follicles undergoing atresia in an ovary is very high, and isolation of cumulus–oocyte complexes (COCs) from such atretic follicles may impair subsequent embryo development in vitro. Our aim was to study if stringent selection by morphological assessment of COCs can improve embryo development, and to evaluate whether oocyte diameter is related with apoptotic ratio in oocytes and blastocysts. COCs from slaughtered cattle were recovered by follicle aspiration and classified depending on oocyte diameter: (A) <110 μm; (B) 110–120 μm; (C) >120 μm. COCs were matured, fertilized and cultured in vitro. Early and late stages of apoptosis were detected by Annexin-V and TUNEL staining, respectively, in denuded oocytes, COCs and blastocysts. Immature oocytes from Group A showed higher apoptotic ratio assessed by TUNEL assay, and the COCs corresponding to this group also showed a higher proportion of apoptotic cumulus cells. After maturation, no differences were present in the incidence of apoptosis among oocytes from different groups, but COCs corresponding to the largest diameter showed less apoptotic cumulus cells. In addition, the percentage of apoptotic oocytes decreased during in vitro maturation in all groups. Apoptotic cell ratio (ACR) in blastocysts was not related to oocyte diameter. In conclusion, oocyte selection and oocyte morphological evaluation prior to maturation was not sufficient to select non-atretic oocytes. When oocyte diameter was used as an additional selection the embryonic developmental potential increased together with oocyte diameter, but this improvement was not related to a lower incidence of apoptosis in the largest oocytes.
摘要译文
卵巢闭锁卵泡的数量非常高，从这种闭锁卵泡中分离卵丘 - 卵母细胞复合体（COCs）可能会影响后续胚胎发育。我们的目的是研究COCs的形态学评估是否能够改善胚胎发育，并评估卵母细胞直径与卵母细胞和囊胚中凋亡率的相关性。来自屠宰牛的COCs通过卵泡抽吸被回收并且根据卵母细胞直径分类：（A）110μm; （B）110-120μm; （C）120μm。 COCs成熟了，受精和体外培养。 Annexin-V和TUNEL染色分别在裸露的卵母细胞，COCs和囊胚中检测凋亡的早期和晚期阶段。A组未成熟卵母细胞经TUNEL法检测凋亡率较高，与其相对应的COCs也呈现较高比例的凋亡卵丘细胞。成熟后，各组卵母细胞凋亡发生率差异无统计学意义，但最大直径的COCs凋亡细胞数较少。此外，在所有组中，体外成熟过程中，凋亡卵母细胞的百分比均下降。囊胚凋亡细胞比率（ACR）与卵母细胞直径无关。结论是，成熟前的卵母细胞选择和卵母细胞形态评估不足以选择非闭锁卵母细胞。当使用卵母细胞直径作为附加选择时，胚胎发育潜力与卵母细胞直径一起增加，但这种改善与最大的卵母细胞凋亡发生率较低无关。
B.Anguita[a];L.Vandaele[b];B.Mateusen[b];D.Maes[b];A.Van Soom[b];. Developmental competence of bovine oocytes is not related to apoptosis incidence in oocytes, cumulus cells and blastocysts[J]. Theriogenology, 2007,67(3): 537-549