Liquid nitrogen vapor is comparable to liquid nitrogen for storage of cryopreserved human sperm Evidence from the characteristics of post thaw human sperm

Liquid nitrogen (LN2) vapor was comparable to LN2 with respect to post-thaw sperm characteristics, and LN2 vapor may substitute for LN2 for the long-term storage of human sperm.

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Jingmei Hu, M.D., Shidou Zhao, Ph.D., Chengyan Xu, Ph.D., Lin Zhang, M.D., Shaoming Lu, Ph.D., Linlin Cui, Ph.D., Jinlong Ma, Ph.D., Zi-Jiang Chen, Ph.D.

Volume 104, Issue 5, Pages 1253-1257



To compare the differences in the characteristics of post-thaw human sperm after storage in either liquid nitrogen (LN2; −196°C) or LN2 vapor (−167°C).


Experimental study.


University hospital.


Thirty healthy volunteers who agreed to donate their normal semen samples for infertility or research were included in the study.


Semen samples (n = 30) were divided into eight aliquots and frozen. Four aliquots of each human semen sample were stored in LN2 (−196°C), and the other four aliquots were stored in LN2 vapor (−167°C). After 1, 3, 6, or 12 months, samples were thawed and analyzed.

Main Outcome Measure(s):

The motility was evaluated by the manual counting method. The viability was estimated by eosin staining. The morphology was analyzed by Diff-Quik staining. The sperm DNA integrity was determined with acridine orange fluorescent staining, and acrosin activity was assayed by the modified Kennedy method.


The characteristics of post-thaw human sperm, including motility, viability, morphology, DNA integrity, and acrosin activity, showed no significant difference between LN2 and LN2 vapor storage for the different time periods.


LN2 vapor was comparable to LN2 in post-thaw sperm characteristics, suggesting that LN2 vapor may be substituted for LN2 for the long-term storage of human sperm.

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Fertility and Sterility

Editorial Office, American Society for Reproductive Medicine

Fertility and Sterility® is an international journal for obstetricians, gynecologists, reproductive endocrinologists, urologists, basic scientists and others who treat and investigate problems of infertility and human reproductive disorders.