摘要
Aim of our study was to clarify if the occurrence of apoptosis in oocytes and cumulus cells is correlated to bovine oocyte developmental competence. The cumulus–oocyte complexes (COCs) were selected according to cumulus status: G1 with more than five layers of compact cumulus cells, G2 with one to five layers of compact cumulus cells and G3 with expanded cumulus cells. The degree of apoptosis in cumulus cells and oocytes measured by caspase staining and TUNEL assay before and after maturation, and 24 h post-insemination was compared to the cleavage, blastocyst formation and hatching rates of each group. Highest cleavage, blastocyst and hatching rates were found in cumulus–oocyte complexes with more than five layers of compact cumulus cells, but no apoptosis was detected in immature or in vitro matured oocytes, regardless of the cumulus status. Many cumulus cells contained active caspases before maturation, but caspase activity declined dramatically after maturation. TUNEL positive cells were rarely observed in each cumulus–oocyte complex upon oocyte recovery, but a huge increase of them was seen after in vitro maturation. Significantly more TUNEL and caspase positive cells were found in G2 cumulus–oocyte complexes. Our results suggest that: (i) oocyte apoptosis does not account for the inferior oocyte quality of G2 and G3; (ii) apoptosis occurs in cumulus cells regardless of the number and compactness of cumulus cells; and (iii) the degree of apoptosis in the compact cumulus–oocyte complexes (G1 and G2) is negatively correlated to the developmental competence of oocyte.
摘要译文
本研究的目的是阐明卵母细胞和卵丘细胞凋亡的发生是否与牛卵母细胞发育能力相关。根据积云状况选择卵丘 - 卵母细胞复合体（COCs）：G1具有五层以上的致密堆积细胞，G2具有一至五层紧凑的卵丘细胞，G3具有扩大的卵丘细胞。通过半胱氨酸天冬氨酸蛋白酶染色和TUNEL测定测定成熟前后和授精后24小时的卵丘细胞和卵母细胞的凋亡程度与卵裂，囊胚形成和孵化率的各组。在具有五层以上致密堆积细胞的卵丘 - 卵母细胞复合体中发现最高的卵裂，囊胚和孵化率，但是在未成熟或体外成熟的卵母细胞中没有检测到凋亡，而不管积云状态如何。许多卵丘细胞在成熟之前含有活性半胱天冬酶，但成熟后caspase活性急剧下降。在卵母细胞恢复时，在每个卵丘 - 卵母细胞复合体中很少观察到TUNEL阳性细胞，但是在体外成熟后发现它们的增加很大。在G2卵丘 - 卵母细胞复合物中发现显着更多的TUNEL和胱天蛋白酶阳性细胞。我们的研究结果表明：（i）卵母细胞凋亡不能解释G2和G3卵母细胞质量下降;（ii）无论卵丘细胞的数量和紧密性如何，卵丘细胞都发生细胞凋亡;和（iii）致密的卵丘 - 卵母细胞复合物（G1和G2）的凋亡程度与卵母细胞的发育能力负相关。
Y.Q.Yuan[a][b];A.Van Soom[a];J.L.M.R.Leroy[a];J.Dewulf[a];A.Van Zeveren[b];A.de Kruif[a];L.J.Peelman[b];. Apoptosis in cumulus cells, but not in oocytes, may influence bovine embryonic developmental competence[J]. Theriogenology, 2005,63(8): 2147-2163