Long-term preservation of mouse spermatozoa as frozen testicular sections

We previously demonstrated that testicular spermatozoa can be preserved as frozen testicular sections, allowing us to preserve male gametes in less space than conventional methods. However, it remains unclear whether the testicular spermatozoa can be preserved for a long period using this procedure. In this study, we examined the function of testicular spermatozoa preserved as frozen testicular sections for l year at -30 or -80 C. Testicular spermatozoa were successfully retrieved from frozen testicular sections preserved at either -30 or -80 C, and their function was assessed using intracytoplasmic sperm injection (ICSI). Over 90% of the oocytes injected with long-term preserved testicular spermatozoa formed pronuclei, which was a frequency similar to that obtained with spermatozoa preserved for a short term, indicating that the testicular spermatozoa retained oocyte activation factor(s). Approximately 70% of the fertilized oocytes developed to 2-cell stage embryos, and 9.3 to 12.8% of the embryos developed to term after transfer into pseudopregnant females, regardless of the preservation temperatures examined. These results indicate that the birthrates of progeny did not differ between the preservation temperatures examined. They also indicate that male gametes can be preserved in testicular frozen sections for at least 1 year without loss of function.