Magnetic separation by annexin V columns or magnetic-activated cell sorting (MACS) is a method to reduce the proportion of apoptotic spermatozoa before any assisted reproductive treatment. The apoptosis process is a mechanism of cell death. It is characterized by morphological and biochemical changes including the exposure of phosphatidylserine, nuclear condensation, and DNA fragmentation, among others.
The use of annexin V columns is indicated when the values of sperm DNA fragmentation, measured by the TUNEL technique, exceed 20% of the total sperm in the analyzed sample.
Cell selection by magnetic activation using annexin V columns is a novel and proven effective technique to separate non-apoptotic sperm from those that have already initiated the apoptosis process by externalizing phosphatidylserine residues.
An increase in pregnancy rates and embryonic division has been reported in oligoasthenozoospermic patients using microinjection of non-apoptotic human sperm selected by MACS.