The single sperm curling test, a modified hypo-osmotic swelling test, as a potential technique for the selection of viable sperm for intracytoplasmic sperm injection

Abstract

Objective: To develop a technique for the selection of viable sperm for intracytoplasmic sperm injection (ICSI), based on the phenomenon of sperm tail curling in a hypo-osmotic environment, through modification of the hypo-osmotic swelling test. Design: Individual sperm were exposed to single sperm curling (SSC) medium and then injected into hamster oocytes to study the effect of SSC medium on fertilization. Setting: All materials were collected from the National University Hospital in Singapore. Patient(s): Semen of proven donors and hamster oocytes with intact zonae were used. Intervention(s): ICSI and the SSC test. Main outcome measure(s): Sperm head decondensation and male pronucleus formation. Result(s): Sperm head decondensation and male pronucleus formation were present in 59.4% and 42.4%, respectively, of the oocytes injected with sperm that had been exposed to SSC medium. These rates were 70% and 48.8%, respectively, when the sperm were washed thoroughly after exposure to SSC medium. In the control group (sperm that were not exposed to SSC medium), these rates were 68.8% and 46.2%, respectively. Conclusion(s): The SSC test is useful for the selection of viable sperm for ICSI. It allows the behavioral study of a single sperm in hypo-osmotic conditions. Thorough washing of the exposed sperm is important. This procedure would be of benefit especially in testicular biopsies or very severe cases of low sperm count in which only a few sperm are found among many other cells and artifact.