Main Effects of In Vitro Manipulation of Human Spermatozoa

The development of in vitro reproduction techniques offered to infertile couples the possibility to have a child, although, on average, the success rate of these techniques remains below 30%. Many reasons can account for such a low success rate, including the fact that in vitro conditions used to manipulate gametes and embryos are quite far from the natural ones. In case of the male gamete, in vitro manipulations include techniques to select motile spermatozoa for oocyte insemination, cryopreservation required for some categories of patients, and other incubation conditions, during which spermatozoa may be exposed to oxidative stress and other insults from the environment or contaminants present in the buffers used for such preparations that may damage their functions and DNA. Here, we review the main studies reporting damages produced in spermatozoa during sperm selection for ARTs, in vitro incubation during IVF/ICSI procedures, and cryopreservation, with particular focus on sperm DNA fragmentation.