Effects of preservation of mouse spermatozoa in electrolyte-free solution at 4°C on the outcome of mouse in vitro fertilization

Purpose: The aim was to assess the fertilizing capacity of spermatozoa cool-preserved in electrolyte-free (EF) solution. Methods: Mouse spermatozoa were cool-preserved in EF solution and the acrosomal status of the spermatozoa was compared before and after preservation using chlortetracycline stain. Mouse oocytes were inseminated by spermatozoa cool-preserved in EF solution for 2, 4, or 7 days and fertilization and blastocyst rates were evaluated. Results: Acrosomal status of spermatozoa cool-preserved in EF solution was not different from spermatozoa before preservation, but the capacitated and acrosome-reacted spermatozoa significantly increased after reinitiation. Cool-preservation in EF solution for up to 4 days did not affect fertilization rate. Blastocyst rate of embryos derived from spermatozoa cool-preserved for 4 or 7 days in EF solution was significantly lower than that of embryos derived from fresh spermatozoa. Conclusions: Mouse spermatozoa cool-preserved in EF solution possesses as much fertilizing capacity as fresh spermatozoa. However prolonged preservation affects the embryonic development.