DNA integrity in human spermatozoa: Relationships with semen quality

The literature contains conflicting evidence regarding the existence of DNA damage in spermatozoa from infertile male patients. To examine this phenom enon, we have studied ejaculated spermatozoa from normozoospermic semen don ors and from a group of the unselected male partners of couples attending a n infertility clinic for initial investigation. Classical semen analysis ac cording to World Health Organization (WHO) guidelines was undertaken with c omputer-assisted sperm analysis (CASA). Spermatozoa were prepared by sequen tial washing and centrifugation and were analyzed for DNA fragmentation usi ng three assays: 1) a single-cell gel electrophoresis (comet) assay, 2) in situ nick translation with prior chemical decondensation (ISNT-decondensed) , and 3) in situ nick translation without prior chemical decondensation (IS NT-condensed). In addition, reactive oxygen species (ROS) generation by spe rmatozoa was measured, and seminal plasma was analyzed for its total reacti ve antioxidant potential (TRAP). When the donor and patient groups were com pared, the latter had lower levels of semen quality and higher levels of DN A damage, which was particularly apparent using the comet assay. Highly sig nificant negative correlations were observed between DNA fragmentation, det ected by all three assays, and semen quality, particularly sperm concentrat ion. In addition, multiple regression analysis indicated that other attribu tes of semen quality, such as sperm movement and ROS generation, were also related to DNA damage. We conclude that a significant proportion of inferti le men have elevated levels of DNA damage in their ejaculated spermatozoa.