REPRODUCTION AND SPERM DNA FRAGMENTATION

Abstract

The aim of this work was to search and analyze literature data about sperm DNA fragmentation and its role in reproduction. There are reports that men of couples with infertility have more sperm with DNA damage. If the number of sperm DNA damage exceeds 25-30% the probability of in vivo fertilization and intrauterine insemination is estimated to be close to zero. After the IVF, in the case of 20% of sperm with DNA fragmentation, the rate of spontaneous abortion increases. At the same time, there are studies whose authors did not find a significant relationship between DNA fragmentation and the results of fertilization or embryo quality after in vitro fertilization. Thus, the fact of the decrease of fertility, the efficiency of the methods of IVF and the increased risk of birth defects can be explained by the increase in the level of sperm DNA fragmentation. Since the appearance of breaks in the structure of DNA during replication is an inevitable process during spermatogenesis, there are normally mechanisms of biological repair of the male genome. There is evidence that the egg is to some extent capable of repairing the damage of sperm DNA that has fertilized it. It has been suggested that attempts at inefficient egg reparation of sperm DNA may have a mutagenic effect, leading to birth defects. Thus, there are currently no clinically relevant standards for the evaluation of chromatin damage (DNA fragmentation) and sperm repair. It is believed that apoptosis, which is a sign of DNA fragmentation, is the end result of various pathological conditions and the degradation system, which normally controls spermatogenesis. However, some researchers believe that such a parameter of spermogram, as the “quality” of sperm is not always associated with the amount of DNA fragmentation. And sperm, morphologically rated as “normal”, may have damaged DNA. The motility and viability of sperm are thought to be related to their DNA fragmentation index. It is also believed that DNA fragmentation of morphologically normal spermatozoa determines a particularly negative impact on the quality of embryos and the results of IVF cycles. Thus, it is not completely clear whether such indicators of a standard spermogram are related to, and how related to, the concentration, motility, morphology of spermatozoa and anomalies of their chromatin. However, the main cause of the negative impact of reactive oxygen species (ROS) on sperm DNA is the direct action of active radicals on protons-protected areas of DNA and, after cell damage, mediated by endonucleasemediated induction of apoptosis. Among the factors that lead to DNA damage as a result of oxidative stress include: testicular torsion, lifestyle (excess body weight, smoking, high physical activity), lack of natural antioxidants, infectious-inflammatory processes of the reproductive tract and etc. Conclusion. The role of disorders of the chromatin structure – sperm DNA fragmentation in reproduction needs further detailed study.

Keywords

• fertility
• dna fragmentation
• sperm.