Sperm cyropreservation and oxidative damage. What does it mean?

About 15% of couples that desire children are affected by infertility. Oxidative stress has been involved in unexplained subfertility with a male factor [1]. Although the excessive production of reactive oxygen species (ROS) is detrimental to human spermatozoa, there is a growing body of evidence that suggests that ROS are also involved in the physiological control of some sperm functions. Under physiological conditions, small amounts of ROS are produced by spermatozoids. These ROS are necessary for efficiency , acrosomal reaction, and finally fertilization [2], but its excessive levels can negatively affect sperm quality. There is a current presumption that the most prolific source of ROS in sperm suspensions is an NADPH oxidase located in leukocytes or in sper-matozoa that produces superoxide, which is further converted to peroxide by the action of superoxide dis-mutase (SOD). Since antioxidants suppress the action of ROS, these compounds have been used in the medical treatment of male infertility (they are beneficial in terms of improving sperm function and DNA integrity) or have been added to the culture medium during sperm separation techniques. Antioxidants have demonstrated their impact on sperm improvement in several studies, in particular in men with high levels of ROS in their sperm. However, in many cases, no beneficial effect was obtained after antioxidant sup-plementation. Negative effects could be observed in long–term treatment or with excessive doses. This medical therapy should not be used in patients with known genetic factors such as karyotype anomalies or Y chromosome deletion. Therefore, it is essential to perform a complete diagnostic workup of the man before deciding which men will respond to medical therapy and which will need to be referred to assisted reproduction. Treatment of oxidative stress should first involve strategies to reduce or eliminate stress–provoking conditions including smoking, varicocele (increases ROS levels in testes and semen), genital infection, gonadotoxins, and hyperthermia. In recent years, interest has increased in the role of antioxidants and B vitamins as modulators of fertility outcome. The antioxidants – alpha–tocopherol (vitamin E), ascor-bic acid (vitamin C), and the retinoids (vitamin A) – are potent scavengers of ROS. Deficient vitamin B concentrations cause elevated homocysteine concentrations and impair the remethylation cycle of phos-pholipids, proteins, DNA, and RNA. These processes are essential in spermatogenesis. Treatment with oral antioxidants has generally been associated with improvement in sperm DNA integrity and in some cases pregnancy rates after assisted reproduction. Actually, antioxidants are provided in diet …