Sperm Mitochondria: Quantitative Regulation and Its Impact on Sperm Quality

Although spermatozoa produce the energy necessary for their proper functions through glycolysis and oxidative phosphorylation to maintain the energy, the sperm mitochondria are thought to be active in producing energy to deliver the ejected paternal gametes in the female reproductive tract to the site of fertilization and then into the maternal gamete, oocyte, since they are degraded by the oocyte after its spermatozoon penetrated. Mitochondrial content in spermatozoa is varied among males, due to various factors through the process of spermatogenesis, consequently making to affect sperm penetrability. Therefore, the content may be a potential sperm biomarker for the quality. Since mitochondrial DNA copy number/mitochondria content in spermatozoa is determined mainly through spermatogenesis, especially from the secondary spermatocyte to fully differentiated spermatozoa, some abnormalities and oxidative stress during spermatogenesis may be the main factors associated with the quantitative change of mitochondrial contents in spermatozoa, affecting their reproductive efficiency. Here, insight into the mechanisms of how sperm mitochondrial contents interact with these factors to make the quantitative alterations will be reviewed.