The Effect of Cryopreservation on the Spontaneous Acrosome Reaction of Human Spermatozoa

Objectives: Cryopreserved spermatozoa are widely used in assisted reproduction programs. While processing and incubation increase the rate of spontaneous acrosome reaction in human spermatozoa, little is known about the effect of cryopreservation. This study was conducted to assess the effect of cryopreservation on the spontaneous acrosome reaction of human spermatozoa. To the best of our knowledge, this is the first study to include a period of incubation before assessing the rate of acrosome reaction. Design: A prospective comparative study of thirty normal human ejaculates according to WHO guidelines. Materials and Methods: Each ejaculate was divided into two equal portions. The fresh portion was processed using tissue culture media and incubated for three to five hours. The second portion was cryopreserved for seven days, after which it was thawed, processed in the same manner and incubated for the same period of time. The hypo-osmotic swelling test was then applied to both portions for identification of living spermatozoa. Evaluation of the spontaneous acrosome reaction was done after staining with pisum sativum aglutinin (FITC-PSA), using the fluorescent microscope. Results: The percentage of living spermatozoa with spontaneously reacted acrosome in the fresh and cryo-thawed samples were 21.7 ± 3.9% and 28.8 ± 3.2% respectively (mean ± standard deviation). This difference was found to be statistically significant (p<0.001). Conclusion: Cryopreservation increases the incidence of spontaneous acrosome reaction in ejaculated sperm after a period of incubation.