Effect of swim-up sperm washing and subsequent capacitation on acrosome status and functional membrane integrity of normal sperm.

OBJECTIVE Sperm preparation techniques select sperm population with improved sperm motion characteristics. We sought to determine whether the swim-up technique selects spermatozoa with the ability to undergo hypoosmotic swelling, and how swim-up and subsequent capacitation affect the acrosome reaction rate. METHODS Semen specimens from 15 normal donors were divided into unprocessed, swim-up, and capacitated groups, and sperm motion characteristics, ability to undergo hypoosmotic swelling, and acrosome reaction rate were measured. RESULTS Sperm motility, viability, and all motion characteristics (except linearity) were significantly increased in both swim-up and capacitated specimens. The ability to respond to hypoosmotic swelling was significantly higher in the spermatozoa isolated by swim-up. The percentage of acrosome-reacted spermatozoa remained unchanged in both unprocessed and swim-up groups, but was significantly higher in the capacitated group. CONCLUSIONS Swim-up isolates sperm with greater ability to undergo hypoosmotic swelling, but does not change the acrosome reaction rate. In vitro capacitation of spermatozoa selected by swim-up enhances the acrosome reaction rate.