Sperm DNA damage in male infertility: etiologies, assays, and outcomes

Male factor infertility is the sole cause of infertility in approximately 20% of infertile couples, with an additional 30% to 40% secondary to both male and female factors. Current means of evaluation of male factor infertility remains routine semen analysis including seminal volume, pH, sperm concentration, motility, and morphology. However, approximately 15% of patients with male factor infertility have a normal semen analysis and a definitive diagnosis of male infertility often cannot be made as a result of routine semen analysis. Attention has focused on the role of sperm nuclear DNA integrity in male factor infertility. Here we review the structure of human sperm chromatin, the etiology and mechanisms of sperm DNA damage, current tests available to assess sperm DNA integrity, and effect of sperm DNA integrity on reproductive outcomes.