Comparison between open and closed systems for vitrification of individual sperm: assessing morphometric measurements and chromatin integrity

Classic vitrification methods are not appropriate when there are minimal numbers of viable sperm, and the new methods emphasize the low semen volumes in these cases. The aim was to assess the efficacy of the cryotech as a device for freezing low sperm volume, through the two methods of open (OVS) and closed (CVS) vitrification systems. Testicular biopsy samples from 30 men with obstructive azoospermia (OA) were assigned to three groups fresh control (FC), OVS, and CVS. Testicular sperms were selected using an ICSI injection pipette and vitrified on the cryotech straws, containing one droplet of freezing medium. After warming, sperm head morphometric characterizations were evaluated with the MSOME technique. Sperm motility, membrane integrity, chromatin quality assessment including DNA fragmentation, Chromomycine A3 staining (CMA3), and Aniline Blue (AB) were assessed. Fluorescein isothiocyanate-conjugated Pisum sativum agglutinin (FITC-PSA) was done to examine sperm acrosome integrity. The mean sperm motility, viability, and sperm with intact acrosome reduced after vitrification, in both methods of CVS, and OVS, but the results were more promising in the closed method (p < 0.05). However, the variations were not significant between the two methods of cryopreservation, the OVS undergoes significant head dimensions changes compared to the control group (p < 0.05). The results also showed higher membrane, and chromatin abnormality after OVS (p < 0.05). The overall post-thaw recovery of human testicular sperm proposes that CVS is more efficient for single sperm cryopreservation, while higher sperm viability, and lower alterations in chromatin, acrosome, and sperm head morphometry were seen compared to OVS.