Dynamic assessment of human sperm DNA damage II: the effect of sperm concentration adjustment during processing

PurposeTo evaluate the effect of sperm concentration adjustment in human ejaculates on the sperm DNA quality and longevity.MethodsSemen samples were obtained from 30 donors with a normal spermiogram. Following centrifugation, the sperm pellet was resuspended in PBS, and the sperm concentration adjusted to 200, 100, 50, 25, 12, and 6x10(6)/mL. Each set of samples was incubated at 37 degrees C for 24h, and the sperm DNA damage was assessed using the chromatin-dispersion test following 0h, 2h, 6h, and 24h of incubation.ResultsSperm DNA fragmentation (SDF) did not differ between the selected experimental conditions at T0; however, Kaplan-Meier estimates for survival showed significant differences with respect to the dilution and time (all P values were smaller than .001). DNA fragmentation in semen samples adjusted to 200x10(6)/mL was approximately 3.3 times higher when compared to samples containing 25x10(6)/mL and 3.9 higher in comparison with samples adjusted to 12x10(6)/mL following 2h of in vitro incubation. Although there was evidence of individual variation in SDF during the incubation period, the general finding was that lower sperm concentrations resulted in a slower rate of DNA fragmentation.ConclusionsIncubation of spermatozoa for ART purposes should be done following a concentration adjustment below 25x10(6)/mL in order to avoid a higher susceptibility of the sperm DNA molecule towards fragmentation.