Motility, progressive motility score and DNA integrity of spermatozoa from cold-preserved mouse cauda epididymis

This study attempted to investigate and validate whether epididymis cold storage could be a suitable alternative for short-term preservation of spermatozoa. Mouse cauda epididymides and spermatozoa were preserved at 4-8°C from 1 day to 6 weeks. From days 1 to 10, motility and fertility were daily examined when motility loss occurred. From week 1, spermatozoa were used for intracytoplasmic sperm injection (ICSI) at weekly intervals to test their fertility, and spermatozoa DNA integrity was determined by comet assay. We found that motility and progressive motility scores gradually decreased with storage time. In nearly all spermatozoa, DNA integrity was maintained from days 1 to 10, but the percentage of spermatozoa with damaged DNA significantly increased from week 2 to week 6. Spermatozoa retained fertility until day 6, although fertility gradually decreased after day 3. From week 1 to week 5, fertilization rates by ICSI were more than 82.69% but decreased gradually after week 3. We found that spermatozoa preserved in the epididymis at 4-8°C had progressively lower motility, fertility and proportion of undamaged DNA, but could still fertilize oocytes. However, all the parameters of cold-preserved spermatozoa were completely inferior to that from cold-preserved cauda epididymides. The results imply that cold storage of cauda epididymides could be conducive to short-term preservation of spermatozoa, and the cold-stored spermatozoa can resist DNA denaturation, which is necessary for maintaining reproductive ability.