Sperm DNA fragmentation and its relevance to men with spinal cord injury

This chapter explores the phenomenon of sperm DNA fragmentation (SDF) in the ejaculates of men with spinal cord Injury (SCI). SDF occurs when the DNA molecule of the sperm cell is broken or fragmented because of the concurrence of single-or double-stranded DNA breakages. SDF may arise in the testis during spermiogenesis, during sperm maturation, and storage within the epididymis, iatrogenically during processing of the ejaculate for assisted fertilization, or within the female reproductive tract. If not corrected by the oocyte following syngamy, SDF has been shown to result in arrested fertility, embryonic failure, and a reduced pregnancy rate. Men with SCI have ejaculates that typically contain extremely high levels of SDF, up to 5 × higher than those of fertile men without SCI and 2 × higher than men without SDF but with evidence of male factor infertility. Previous reviews have identified etiologies in men with SCI that are thought to be associated with poor semen quality and which include alternations in the hormonal milieu of the testis, scrotal hyperthermia, anejaculation, differences in molecular biology of the testis, leukocytospermia, oxidative damage, abnormal seminal vesicular secretions, and abnormal seminal plasma chemistry. The majority of studies on the ejaculate of men with SCI have focused on classical sperm parameters (sperm motility and necrozoospermia) with little attention given to SDF. Consequently, we explore the possible interaction with the different etiologies that may produce SDF highlighting the different effectors that may produce an increase in the levels of SDF. Additionally, and taking into account the multi-factorial inputs that might potentially lead to elevated SDF in men with SCI, we propose a synergistic approach for sperm selection, taking into account pre- and postejaculatory strategies, to overcoming infertility that ideally requires the use of single spermatozoon free of DNA damage.