Sperm DNA fragmentation and apoptosis levels: A comparison of the swim up and the density gradient centrifugation methods for sperm preparation

This study investigated the efficiency of two sperm preparation methods, namely, density gradient centrifugation and the swim-up method, in selecting spermatozoa based on the DNA fragmentation index and the apoptosis levels. Fifteen semen samples from infertile couples underwent sperm preparation in this study. The Makler® counting chamber and Eosin Y staining were used to analyse the sperm concentration, motility and viability. The sperm chromatin dispersion assay was used to determine the sperm DNA fragmentation index, while western blotting was used to determine the apoptosis levels. This study showed that Swim Up (SU) and Density Gradient Centrifugation (DGC) methods were able to select sperm with lower DFIs compared to sperm from whole semen. The SU method selected for sperm in both the “moderate” and “severe” DFI categories that have low DFIs better than the DGC method. Western blotting for the expression of caspase 3 in sperm showed a band of ~35 kDa and this band’s intensity was lower in post-SU sperm compared to post-DGC sperm. Both methods selected for sperm with low caspase 3 expression, although the SU method selected for sperm with low activity of caspase 3 better than the DGC method. In addition to selecting for sperm with better progressive motility and viability, the SU and DGC methods also selected for sperm with low sperm DFIs and apoptosis levels.