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.