Feasibility of Multiple Cycles of Thaw-Refreeze Human Spermatozoa by Standard Vapor Freezing Method

Abstract

ObjectiveTo evaluate the feasibility of repetead cycles of thaw-refreeze human spermatozoa by using the standard liquid nitrogen vapor freezing method.DesignSemen specimens frozen by standard vapor freezing were thawed at room temperature for 5 minutes and at 37°C for 20 minutes. An aliquot was removed for sperm analysis and the remaining specimen was refrozen by standard vapor freezing without removing the cryomedia (TEST-yolk buffer with glycerol, Irvine, USA). The specimens were stored in liquid nitrogen for 24h and thawed by the same technique. Repeated freeze-thaw cycles were performed until no motile sperm were seen.Materials and methodsSixteen frozen semen samples were obtained from twelve subjects (normozoospermic, n=5; and oligozoospermic, n=7) who required disposal of their samples stored in our sperm bank. Each sample was evaluated for percent total and progressive motility, as well as vitality if no motile sperm was seen, after each cryopreservation cycle. Wilcoxon signed-rank test was used to test for statistical differences.ResultsTabled 1ConclusionsMotile spermatozoa can be obtained after repetead cycles of cryopreservation using the standard vapor freezing method. The sperm ability to resist injury due to the freeze-thawing process is related to the initial semen quality. However, motile sperm obtained after repeated freezing will be only suitable for intracytoplasmic sperm injection. Re-freezing leftover frozen-thawed specimens may be recommended for patients who were not able to freeze multiple specimens, such as cancer patients. Though our results are promising, others studies are required in order to assess the fertility potential of refrozen human semen in cycles of assisted reproduction. ObjectiveTo evaluate the feasibility of repetead cycles of thaw-refreeze human spermatozoa by using the standard liquid nitrogen vapor freezing method. To evaluate the feasibility of repetead cycles of thaw-refreeze human spermatozoa by using the standard liquid nitrogen vapor freezing method. DesignSemen specimens frozen by standard vapor freezing were thawed at room temperature for 5 minutes and at 37°C for 20 minutes. An aliquot was removed for sperm analysis and the remaining specimen was refrozen by standard vapor freezing without removing the cryomedia (TEST-yolk buffer with glycerol, Irvine, USA). The specimens were stored in liquid nitrogen for 24h and thawed by the same technique. Repeated freeze-thaw cycles were performed until no motile sperm were seen. Semen specimens frozen by standard vapor freezing were thawed at room temperature for 5 minutes and at 37°C for 20 minutes. An aliquot was removed for sperm analysis and the remaining specimen was refrozen by standard vapor freezing without removing the cryomedia (TEST-yolk buffer with glycerol, Irvine, USA). The specimens were stored in liquid nitrogen for 24h and thawed by the same technique. Repeated freeze-thaw cycles were performed until no motile sperm were seen. Materials and methodsSixteen frozen semen samples were obtained from twelve subjects (normozoospermic, n=5; and oligozoospermic, n=7) who required disposal of their samples stored in our sperm bank. Each sample was evaluated for percent total and progressive motility, as well as vitality if no motile sperm was seen, after each cryopreservation cycle. Wilcoxon signed-rank test was used to test for statistical differences. Sixteen frozen semen samples were obtained from twelve subjects (normozoospermic, n=5; and oligozoospermic, n=7) who required disposal of their samples stored in our sperm bank. Each sample was evaluated for percent total and progressive motility, as well as vitality if no motile sperm was seen, after each cryopreservation cycle. Wilcoxon signed-rank test was used to test for statistical differences. ResultsTabled 1 ConclusionsMotile spermatozoa can be obtained after repetead cycles of cryopreservation using the standard vapor freezing method. The sperm ability to resist injury due to the freeze-thawing process is related to the initial semen quality. However, motile sperm obtained after repeated freezing will be only suitable for intracytoplasmic sperm injection. Re-freezing leftover frozen-thawed specimens may be recommended for patients who were not able to freeze multiple specimens, such as cancer patients. Though our results are promising, others studies are required in order to assess the fertility potential of refrozen human semen in cycles of assisted reproduction. Motile spermatozoa can be obtained after repetead cycles of cryopreservation using the standard vapor freezing method. The sperm ability to resist injury due to the freeze-thawing process is related to the initial semen quality. However, motile sperm obtained after repeated freezing will be only suitable for intracytoplasmic sperm injection. Re-freezing leftover frozen-thawed specimens may be recommended for patients who were not able to freeze multiple specimens, such as cancer patients. Though our results are promising, others studies are required in order to assess the fertility potential of refrozen human semen in cycles of assisted reproduction.