冷冻保存精子对其功能的影响-DNA稳定性
Semen cryopreservation has been reported to induce DNA damage, but the exact mechanism by which this damage occurs is not known. One theory is that it increases levels of oxidative stress in the semen. Some reports have proposed that it stimulates caspases, but the addition of caspase inhibitors to the medium has been shown to have no significant effect on post-thaw motility. Other reports have suggested that cryopreservation induces apoptosis.
据报道，精液冷冻保存会导致 DNA 损伤，但这种损伤发生的确切机制尚不清楚。 一种理论是冷冻保存会增加精液中的氧化应激水平。一些报告指出冷冻会释放半胱天冬酶，但有数据表明，向培养基中添加半胱天冬酶抑制剂对精子解冻后的活性没有显著影响。其他报告表明冷冻保存会诱导细胞凋亡。
Cryopreservation can cause and exacerbate DNA fragmentation in spermatozoa.1 Some studies indicate that cryopreservation can increase inappropriate chromatin condensation inhuman sperm.2 DNA integrity can be determined by several methods, including the TUNEL assay, (direct measure of DNA damage) , and the Comet assay, (electrophoresis assay evaluating packaging of DNA within the nucleus).2,3 The sperm chromatic structure assay (SCSA) measures the extent of DNA denaturation.4 This method can determine whether the DNA within a sperm cell is normal, native chromatin that is structurally intact or if it is abnormal chromatin.
冷冻保存会导致和加剧精子中的DNA片段化。1一些研究表明，冷冻保存会增加人类精液染色质的非正常浓缩。2 DNA完整性可以通过多种方法确定，包括 TUNEL试验(直接测量 DNA 损伤)和彗星试验(电泳试验评估DNA在细胞核内的排列)。2，3 精子染色结构分析 (SCSA) 可以测量 DNA变性的程度。4 这种方法可以确定精子细胞内的 DNA 是正常的、结构完整的原生染色质还是异常染色质。
Oxidative damage caused by increased levels of reactive oxygen species may play a role in cryo-injury of sperm DNA.Antioxidants such as genistein (a plant-derived phyto-estrogen)and those found in native semen protect sperm from oxidative stress and lipid peroxidation and thereby reduce DNA fragmentation.1 An increase in the activation of the intrinsic apoptotic cascade might result from insults to structural integrity of sperm that occurs during cryopreservation, but this is most likely not responsible for DNA damage in sperm.
活性氧水平升高引起的氧化损伤可能对冷冻精子造成的DNA损伤负一定责任。抗氧化剂如染料木黄酮(一种植物来源的植物雌激素)和精液原浆中发现的抗氧化剂可保护精子免受氧化应激和脂质过氧化，从而减少 DNA 片段化。1内在细胞凋亡的大量增加可能是由于冷冻保存期间精子结构完整性发生了损害，但这很可能不是精子中 DNA 损伤的原因。
References数据来源：
1. Thomson LK, Fleming SD, Aitken RJ,De Iuliis GN,ZieschangJA, Clark AM. Cryopreservation-induced human sperm DNAdamage is predominantly mediated by oxidative stress ratherthan apoptosis. Hum Reprod 2009; 24 (9) : 2061-70.
2. Yildiz C, Ottaviani P, Law N, Ayearst R, Liu L, McKerlie C. Effectsof cryopreservation on sperm quality, nuclear DNA integrity,in vitro fertilization, and in vitro embryo development in themouse. Reproduction 2007; 133 (3) : 585-95.
3. Bakos HW, Thompson JG, Feil D, Lane M. Sperm DNA damageis associated with assisted reproductive technology pregnancy.Int J Androl 2008; 31 (5) : 518-26.
4. Kobayashi H, Larson K, Sharma RK, Nelson DR, Evenson DP,Toma H,et al. DNA damage in patients with untreated cancer asmeasured by the sperm chromatin structure assay. Fertil Steril2001; 75 (3) : 469-75.
