Cryopreservation of human spermatozoa : Comparison of two cryoprotectants and two freezing methods

A prospective experimental study was performed to compare sperm cryosurvival rate between two kinds of cyroprotective media: citrate-egg yolk-glycerol (CEG) and TEST-citrate-egg yolk-glycerol (TEST-EYG), and between two freezing methods: noncontrolled rate (NCR) freezing and computer controlled rate (CR) freezing. One hundred semen samples were included in the study. Each sample was divided into two parts, which were prepared as two CEG and two TEST-EYG mixture straws, then one straw from each mixture was frozen by the NCR-freezing method and the complementary straw was frozen by the CR-freezing method. After one week of cryostorage, the straws were thawed and the post-thaw sperm survival was assessed. As the results, the post-thaw sperm survival rate of the CEG media group was slightly higher than the TEST-EYG group in both the NCR-freezing method (51.2% vs 47.0%, p < 0.05) and the CR-freezing method (48.2% vs 43.4%, p < 0.05); and similarly; the NCR-freezing group yielded a slightly higher post-thaw sperm survival rate than the CR-freezing group in both the CEG media used (51.2% vs 48.2%, p < 0.05) and the TEST-EYG media used (47.0% vs 43.4%, p < 0.05). However, these did not have clinical significance because the differences were too small. In conclusion, the use of either CEG or TEST-EYG media, and either the NCR or CR-freezing method did not have clinical differences on the post-thaw sperm survival.