Could cryopreserved human semen samples be stored at -80°C?

OBJECTIVE: To evaluate storage time effects in cryopreserved human semen samples, kept in the freezer at a controlled temperature of -80°C, on sperm viability after thawing. METHODS: We used 20 semen samples. Each sample was cryopreserved in 10 fingers, which were divided into five groups: one group was kept in cryogenic canisters throughout the experiment(control), and four groups were kept in a VIP Ultra Low MDF-U76V- PE freezer, with the temperature set at -80°C, for 24, 48, 72 and 96 hours, respectively. After the exposure time, the samples were stored in cryogenic canisters after being thawed. The analyzed parameters were: motility, vitality and mitochondrial activity. RESULTS: After thawing, we noticed decreased sperm motility, vitality and mitochondrial activity, when comparing the tested groups with the control group, as well as a progressive reduction in the analyzed parameters between the times evaluated. CONCLUSIONS: Cryopreservation of semen samples at -80°C is potentially harmful to sperm viability, causing damage when submitted to longer exposure times.

The effects of storing and transporting cryopreserved semen samples on dry ice.

OBJECTIVE: This study aimed to test the effects on sperm viability of transporting cryopreserved semen samples on dry ice. METHODS: Twenty normozoospermic semen samples were cryopreserved and divided into five groups. The samples in Group 1 were immersed in liquid nitrogen throughout the experiment in cryogenic storage tanks; the cryopreserved straws in Group 2 were placed in a Styrofoam box containing dry ice and kept under these conditions for 48 hours; the samples in Group 3 were kept for 48 hours on dry ice under the same conditions as the Group 2 samples, and were then moved to a storage tank filled with liquid nitrogen; Group 4 samples were also kept for 48 hours in dry ice storage, and the Styrofoam box containing the samples was shipped by plane to assess the effects of shipping; the samples in Group 5 were shipped together with the Group 4 samples and were placed in a storage tank with liquid nitrogen after spending 48 hours stored on dry ice. After thawing, sperm parameters were analyzed for viability, vitality, and motility; spermatozoa were also tested for mitochondrial activity. RESULTS: Significant decreases in motility recovery rates (P=0.01) and vitality (P=0.001) were observed in all groups when compared to the control group. Mitochondrial activity was significantly decreased only in Group 5 (P=0.04), as evidenced by greater numbers of sperm cells not stained by reagent 3,3'-diaminobenzidine. CONCLUSIONS: Transportation did not affect the quality of cryopreserved semen samples, but dry ice as a means to preserve the samples during transportation had detrimental effects upon the sperm parameters assessed in this study.