Zhang Luyao, Wang Zichuan, Lu Tengfei, Meng Lin, Luo Yan, Fu Xiangwei, Hou Yunpeng
State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China.
Key Laboratory of Animal Genetics, Breeding and Reproduction, Ministry of Agriculture and National Engineering Laboratory for Animal Breeding, College of Animal Science and Technology, China Agricultural University, Beijing, China.
Front Cell Dev Biol. 2020 Dec 15;8:580876. doi: 10.3389/fcell.2020.580876. eCollection 2020.
Overweight or obese women seeking pregnancy is becoming increasingly common. Human maternal obesity gives rise to detrimental effects during reproduction. Emerging evidence has shown that these abnormities are likely attributed to oocyte quality. Oxidative stress induces poor oocyte conditions, but whether mitochondrial calcium homeostasis plays a key role in oocyte status remains unresolved. Here, we established a mitochondrial Ca overload model in mouse oocytes. Knockdown gatekeepers of the mitochondrial Ca uniporters Micu1 and Micu2 as well as the mitochondrial sodium calcium exchanger NCLX in oocytes both increased oocytes mitochondrial Ca concentration. The overload of mitochondria Ca in oocytes impaired mitochondrial function, leaded to oxidative stress, and changed protein kinase A (PKA) signaling associated gene expression as well as delayed meiotic resumption. Using this model, we aimed to determine the mechanism of delayed meiosis caused by mitochondrial Ca overload, and whether oocyte-specific inhibition of mitochondrial Ca influx could improve the reproductive abnormalities seen within obesity. Germinal vesicle breakdown stage (GVBD) and extrusion of first polar body (PB1) are two indicators of meiosis maturation. As expected, the percentage of oocytes that successfully progress to the germinal vesicle breakdown stage and extrude the first polar body during culture was increased significantly, and the expression of PKA signaling genes and mitochondrial function recovered after appropriate mitochondrial Ca regulation. Additionally, some indicators of mitochondrial performance-such as adenosine triphosphate (ATP) and reactive oxygen species (ROS) levels and mitochondrial membrane potential-recovered to normal. These results suggest that the regulation of mitochondrial Ca uptake in mouse oocytes has a significant role during oocyte maturation as well as PKA signaling and that proper mitochondrial Ca reductions in obese oocytes can recover mitochondrial performance and improve obesity-associated oocyte quality.
寻求怀孕的超重或肥胖女性越来越普遍。人类母体肥胖在生殖过程中会产生有害影响。新出现的证据表明，这些异常可能归因于卵母细胞质量。氧化应激会导致卵母细胞状态不佳，但线粒体钙稳态是否在卵母细胞状态中起关键作用仍未解决。在这里，我们在小鼠卵母细胞中建立了线粒体钙超载模型。敲低卵母细胞中线粒体钙单向转运体Micu1和Micu2以及线粒体钠钙交换体NCLX的守门蛋白，均增加了卵母细胞线粒体钙浓度。卵母细胞线粒体钙超载会损害线粒体功能，导致氧化应激，并改变蛋白激酶A（PKA）信号相关基因的表达以及减数分裂恢复延迟。利用这个模型，我们旨在确定线粒体钙超载导致减数分裂延迟的机制，以及卵母细胞特异性抑制线粒体钙内流是否可以改善肥胖中出现的生殖异常。生发泡破裂期（GVBD）和第一极体（PB1）的排出是减数分裂成熟的两个指标。正如预期的那样，在培养过程中成功进入生发泡破裂期并排出第一极体的卵母细胞百分比显著增加，并且在适当调节线粒体钙后，PKA信号基因的表达和线粒体功能得以恢复。此外，线粒体性能的一些指标，如三磷酸腺苷（ATP）和活性氧（ROS）水平以及线粒体膜电位，恢复到正常水平。这些结果表明，小鼠卵母细胞中线粒体钙摄取的调节在卵母细胞成熟以及PKA信号传导中具有重要作用，并且肥胖卵母细胞中适当降低线粒体钙可以恢复线粒体性能并改善与肥胖相关的卵母细胞质量。
