Center for Reproductive Medicine, Shandong University, Jinan, China.
National Research Center for Assisted Reproductive Technology and Reproductive Genetics, Jinan, China.
J Pineal Res. 2019 Oct;67(3):e12601. doi: 10.1111/jpi.12601. Epub 2019 Aug 22.
Embryo development potential and reproductive clinical outcomes are all deeply rooted in oocyte maturation. Melatonin has been reported to promote oocyte maturation as an antioxidant in nonprimate species. Its antioxidative functions also help reduce plasma membrane rigidity, which facilitates clathrin-mediated endocytosis (CME). Whether melatonin has effects on human oocyte maturation by regulating CME is worthy of exploration. In this study, we found that the optimal melatonin concentration for human oocyte maturation was 10 M, and the maturation rate of this group was 71.9% (P = .03). The metaphase II (MII) stage oocytes obtained by in vitro maturation with 10 M melatonin had a significantly higher fertilization rate (81.4% vs 61.4%, respectively, P = .017) and blastocyst rate (32.2% vs 15.8%, respectively, P = .039) compared to controls. During maturation, antioxidative melatonin greatly enhanced CME and decreased intra-oocyte cAMP level. The former was evidenced by the increasing numbers of coated pits and vesicles, and the upregulated expression of two major CME markers-clathrin and adaptor protein-2 (AP2). CME inhibitor dynasore increased intra-oocyte cAMP level and blocked oocyte maturation, and melatonin could partly rescue oocyte maturation and significantly elevate the expression of clathrin and AP2 in the presence of dynasore. Therefore, we conclude that melatonin could promote human oocyte maturation and early embryo development through enhancing CME.
胚胎发育潜能和生殖临床结局都深深植根于卵母细胞成熟。褪黑素已被报道作为非灵长类物种中的抗氧化剂促进卵母细胞成熟。其抗氧化功能还有助于降低质膜刚性，从而促进网格蛋白介导的内吞作用（CME）。褪黑素是否通过调节 CME 对人卵母细胞成熟有影响值得探索。在这项研究中，我们发现褪黑素促进人卵母细胞成熟的最佳浓度为 10μM，该组的成熟率为 71.9%（P=0.03）。用 10μM 褪黑素进行体外成熟获得的中期 II（MII）期卵母细胞的受精率（分别为 81.4%和 61.4%，P=0.017）和囊胚率（分别为 32.2%和 15.8%，P=0.039）显著高于对照组。在成熟过程中，抗氧化剂褪黑素大大增强了 CME 并降低了卵内 cAMP 水平。这可以通过增加有被小窝和小泡的数量以及上调两个主要 CME 标志物——网格蛋白和衔接蛋白-2（AP2）的表达来证明。CME 抑制剂 dynasore 增加了卵内 cAMP 水平并阻断了卵母细胞成熟，而在 dynasore 存在的情况下，褪黑素可以部分挽救卵母细胞成熟并显著提高网格蛋白和 AP2 的表达。因此，我们得出结论，褪黑素可以通过增强 CME 来促进人卵母细胞成熟和早期胚胎发育。
