A search for molecular mechanisms underlying male idiopathic infertility

Infertility affects approximately 15% of the couples wanting to conceive. In 30 − 40% of the cases the aetiology of male infertility remains unknown and is called idiopathic male infertility. When assisted reproductive technologies are used to obtain pregnancy, an adequate (epi)genetic diagnosis of male infertility is of major importance to evaluate if a genetic abnormality will be transmitted to the offspring. In addition, there is need for better diagnostic seminal biomarkers to assess the success rates of these assisted reproductive technologies. This review investigated the possible causes and molecular mechanisms underlying male idiopathic infertility by extensive literature searches of: (i) causal gene mutations; (ii) proteome studies of spermatozoa from idiopathic infertile men;(iii) the role of epigenetics; (iv) post-translational modifications; and (v) sperm DNA fragmentation in infertile men. In conclusion, male infertility is a complex, multi-factorial disorder and the underlying causes often remain unknown. Further research on the (epi)genetic and molecular defects in spermatogenesis and sperm function is necessary to improve the diagnosis and to develop more personalized treatments of men with idiopathic infertility.