Discipline of Biological Sciences and Priority Research Centre in Reproductive Science, Faculty of Science and IT, University of Newcastle, University Drive, Callaghan, NSW 2308, Australia.
Mol Hum Reprod. 2013 Aug;19(8):475-85. doi: 10.1093/molehr/gat025. Epub 2013 Apr 1.
This article considers the origins of DNA damage in human spermatozoa, the methods that are available to monitor this aspect of semen quality and the clinical significance of such measurements. DNA damage in spermatozoa appears to be largely oxidative in nature, inversely correlated with levels of nuclear protamination and frequently associated with the activation of a truncated apoptotic pathway. DNA base adducts formed as a result of oxidative attack are released from the spermatozoa into the extracellular space through the action of a glycosylase, OGG1. This creates an abasic site, which is not resolved until fertilization because spermatozoa do not possess the molecular machinery needed to continue the base excision repair pathway. The abasic sites so generated in human spermatozoa are readily detected by SCSA or the Comet assay; however, no signal is detectable with TUNEL. This is because spermatozoa lack the enzyme (APE1) needed to create the free 3' hydroxyl groups required by this detection system. Nevertheless, spermatozoa do eventually become TUNEL positive as they enter the perimortem. The American Society of Reproductive Medicine Practice Committee has suggested that DNA damage in spermatozoa should not be assessed because the correlation with pregnancy is inconsistent across independent studies. However, this is a straw man argument. The reason why such assays should be undertaken is not just that they reflect the underlying quality of spermatogenesis but, more importantly, that the DNA damage they reveal may have detrimental effects on the developmental normality of the embryo and the health of possible future children.
本文探讨了人类精子 DNA 损伤的起源、监测精液质量这一方面的现有方法，以及此类检测的临床意义。精子中的 DNA 损伤主要是氧化性质的，与核组蛋白水平呈负相关，并且经常与截断的凋亡途径的激活有关。由于氧化攻击而形成的 DNA 碱基加合物通过糖苷酶 OGG1 从精子释放到细胞外空间。这会产生一个无碱基位点，直到受精才会得到解决，因为精子不具备继续碱基切除修复途径所需的分子机制。通过 SCSA 或彗星试验可以很容易地检测到人类精子中产生的这种无碱基位点；然而，TUNEL 检测不到信号。这是因为精子缺乏（APE1）酶，而该检测系统需要该酶来产生所需的游离 3' 羟基基团。然而，随着精子进入濒死期，它们最终会成为 TUNEL 阳性。美国生殖医学学会实践委员会建议不要评估精子中的 DNA 损伤，因为其与妊娠的相关性在独立研究中不一致。然而，这是一个稻草人论点。进行此类检测的原因不仅在于它们反映了精子发生的潜在质量，更重要的是，它们所揭示的 DNA 损伤可能对胚胎的发育正常性和未来孩子的健康产生不利影响。
