Morphometrical comparison of human spermatozoa obtained from semen and swim-up methodology

Because morphology is regularly established in semen smears, but not in swim-up spermatozoa, we were interested in comparing some morphological parameters of semen and swim-up spermatozoa to establish if the cells selected by the swim-up method were morphologically similar to those considered normal in semen. Normal human semen samples were divided into two aliquots. One of these aliquots was washed by centrifugation with B₂ medium and sperm smears were prepared with the resulting pellet as a control. The other aliquot was used to perform swim-up separation and the spermatozoa from the supernatant were used as experimental smears. Both groups were stained according to the triple stain technique and spontaneous acrosome reaction and viability were determined. Video microscopy and computer-assisted image processing of live and non-reacted sperm cells were used to establish morphometrical parameters of the sperm head in both populations. The following set of morphometrical parameters were considered: width, length, width/length ratio, acrosome area, head area, and acrosome area/head area ratio. An increase in head width, a decrease in head length and a subsequent increase of width/length ratio were found in swim-up cells compared with the control group. A slight increase in acrosome area/head area ratio was also observed in swim-up spermatozoa. Through the swim-up methodology we were able to select a subpopulation of oval shaped heads with spermatozoa having a bigger acrosome area in comparison to semen.