Magnetic-activated cell sorting before cryopreservation preserves mitochondrial integrity in human spermatozoa

Superparamagnetic annexin-V conjugated microbeads are able to eliminate spermatozoa with externalized phosphatidylserine, a membrane feature of apoptotic cells as well as spermatozoa with deteriorated plasma membrane. Our objective was to evaluate the effects of annexin-V Magnetic-Activated Cell Sorting (MACS) in cryopreservation-thawing protocols and on integrity of sperm mitochondrial transmembrane potential and mitochondrial integrity survival rate (MSR). Mature spermatozoa of 10 healthy donors were prepared by density gradient centrifugation and divided into 2 aliquots afterwards. The first one was subjected to annexin-V MACS followed by cryopreservation and thawing, while the second was cryopreserved-thawed without MACS to serve as control. Annexin-negative sperm separated by MACS showed significantly higher levels of intact mitochondria following cryopreservation-thawing (45.4+/-8.6%) compared to sperm that were not separated (15.8+/-4.6%, p<0.01). Separating a distinctive population of non-apoptotic spermatozoa with intact membranes may optimize cryopreservation-thawing outcome. MACS using annexin-V microbeads enhances the percentage of spermatozoa with intact transmembrane mitochondrial potential and mitochondrial integrity survival rates following cryopreservation.