Characterization of subsets of human spermatozoa at different stages of maturation: implications in the diagnosis and treatment of male infertility

BACKGROUND: Reactive oxygen species (ROS)-induced damage of membrane phosph olipids and DNA in human spermatozoa has been implicated in the pathogenesi s of male infertility. In this study, variations in ROS production, DNA str ucture (as measured by the sperm chromatin structure assay) and lipid compo sition, were studied in human spermatozoa at different stages of maturation . METHODS: Sperm subsets were isolated by discontinuous density gradient ce ntrifugation of semen samples obtained from healthy donors and from inferti lity patients. RESULTS: DNA damage and ROS production were highest in immat ure spermatozoa with cytoplasmic retention and abnormal head morphology, an d lowest in mature spermatozoa. Docosahexaenoic acid and sterol content wer e highest in immature germ cells and immature spermatozoa, and lowest in ma ture spermatozoa. The relative proportion of ROS-producing immature spermat ozoa in the sample was directly correlated with DNA damage in mature sperma tozoa, and inversely correlated with the recovery of motile spermatozoa. Th ere was no correlation between DNA damage and sperm morphology in mature sp ermatozoa. CONCLUSIONS: The high levels of ROS production and DNA damage ob served in immature spermatozoa may be indicative of derangements in the reg ulation of spermiogenesis. DNA damage in mature spermatozoa may be the resu lt of oxidative damage by ROS-producing immature spermatozoa during sperm m igration from the seminiferous tubules to the epididymis.