Dynamic assessment of human sperm DNA damage I: the effect of seminal plasma-sperm co-incubation after ejaculation.

AIM: The purpose of the study was to evaluate the impact of seminal plasma in human ejaculates on the sperm DNA quality and DNA longevity.

METHODS: Semen samples for this study were obtained from 20 donors with a normal spermiogram. Following centrifugation, the sperm pellet was resuspended either in the seminal plasma proceeding from its respective donor, or in an equal amount of PBS, adjusting the concentration to 50 × 106 /ml. Each set of samples was incubated at 37 °C for 24 h and the sperm DNA damage was assessed using the chromatin-dispersion test following 0, 2, 6, and 24 h of incubation.

RESULTS: Sperm DNA fragmentation (SDF) did not differ between the two experimental conditions at T0; however, Kaplan-Meier estimates to test for survival showed an statistical significant increase of SDF in the seminal plasma group when compared to the PBS group following all timeframes (p 0.000). With respect to sperm DNA longevity, the most dramatic loss of sperm DNA quality occurred during the first 2 h of incubation, with the rate of SDF (rSDF) in the seminal plasma being 2.1 more intense than in PBS. Interestingly, the rSDF was found to vary significantly between individuals, which was confirmed with significant correlations in all rSDF timeframes (rSDF T0-2, p 0.049; rSDF T2-6, p 0.000; rSDF T6-24: p 0.000).

CONCLUSIONS: Co-incubation of semen samples in seminal plasma after ejaculation increases iatrogenic sperm damage. This effect is statistically significant after 2 h of co-incubation. Subsequently, for ART purposes seminal plasma must be quickly removed after ejaculation-liquefaction, to avoid a higher susceptibility of sperm DNA towards fragmentation.