Density gradient centrifugation and glass wool filtration of semen remove spermatozoa with damaged chromatin structure

The ability of double-layered density gradient centrifugation (DGC) or glass wool filtration (GWF) of semen to remove spermatozoa with damaged chromatin structure was assessed by the flow cytometric sperm chromatin structure assay (SCSA), which measures the susceptibility to sperm nuclear denaturation in situ. Ejaculates from 26 men attending a university-affiliated assisted reproduction laboratory were processed by DGC and GWF. Unprocessed, DGC- and GWF-processed specimens were assessed by the SCSA and by conventional semen parameters. Changes in chromatin structure were compared with conventional semen parameters. Both sperm preparation techniques yielded sperm suspensions with improved sperm chromatin structure as well as motility (%), forward progression (1–4) and viability (%). DGC was superior to GWF in the efficiency of recovering motile, morphologically normal, mature sperm suspensions. However, GWF produced improved chromatin integrity (SDαt) and viability. Moderate correlations between SCSA and conventional sperm parameters were observed. Nevertheless, the SCSA provides additional information about the biochemical integrity of sperm DNA and may be used in future studies to provide insight into assisted reproduction technology outcomes not explained by conventional sperm parameters.