Study Reiterates Efficacy of Long-term Liquid Nitrogen Storage for Preserving Sperm Motility

Sperm banking has been recognized as an effective strategy to circumvent iatrogenic infertility and also retain the reproductive potential of adolescent and young adult males undergoing cancer therapy. However, the effect of long-term cryopreservation on the fertilization potential of sperm has been contentious. Now, a study performed by a group of Israeli researchers rules out any negative influence of prolonged storage in liquid nitrogen on the progressive motility concentration (PMC) of sperm. The results are published in the online issue of the journal Human Reproduction.

Leah Yogev and colleagues from the Sackler Faculty of Medicine, Tel Aviv Sourasky Medical Center, Israel, investigated the effects of long-term liquid nitrogen cryostorage of sperm samples on PMC. The researchers evaluated 2,525 thawed semen samples obtained from 72 sperm donors for IUI, and noted the PMC prior to and after storing the specimens for a period of 0.5 to 14.4 years. The key findings were as follows:
• The mean PMC (±SD) value observed after freezing/thawing and prior to long-term storage was10.8 ± 3.3 x 106/mL
• The value noted after cryostorage and prior to using the sample for IUI was12.3 ± 2.9 x 106/mL (P<0.0001)
• Analysis of the specimens stored for different time periods showed that the duration of storage do not influence the PMC of the samples significantly (r=–0.03; P=0.08)
• Period of storage did not cause substantial variation in the PMC of both raw and washed sperm samples

The researchers also speculate that the high PMC values noted after the storage, when compared to the pre-storage values, could be an artifact due to the small amount of pre-storage specimens.

Earlier, Clarke et al (Fertility and Sterility, 2006) concluded liquid nitrogen storage as an efficient cryopreservation protocol that preserves the sperms’ fertilization potential for a prolonged period of time. The researchers evaluated the motility and the ability of the sperm to bind with oocyte zona pellucida after cryopreserving the specimens in liquid nitrogen for 28 years. The samples stored for prolonged duration demonstrated good post-thaw motility and zona pellucida binding potential. Additionally, evaluation of four out of five specimens showed normal zona-induced acrosome reaction.

Although sperm cryopreservation has been widely accepted as a simple and efficient method for preserving fertility of patients undergoing anticancer treatment, the number of patients being referred to a sperm bank by oncologists is comparatively low. A postal survey conducted by Schover et al (Journal of Clinical Oncology, 2002) investigated the oncologist’s attitudes, knowledge, and practice of referring patients for banking sperms prior to cancer treatment. The survey findings revealed that 91% of the physicians support sperm cryopreservation in cancer patients facing the risk of iatrogenic infertility prior to the initiation of the treatment. However, 48% of them agree that they either discuss this option to less than a quarter of eligible candidates ≥14 years of age, or not even mention the strategy to some patients.

The recent study, suggesting the recovery of sperm fertilization capacity even after long-term storage, further underscore the importance of following recommendations for sperm banking put forth by the Royal College of Obstetricians and Gynaecologists.
• All the male cancer patients confronting the enhanced risk for long-term gonadal toxicity should be referred to sperm banking
• Facilities for long-term sperm banking should be fully funded and available universally to all candidates who are at an enhanced risk for future infertility.

References

1. Yogev L, Kleiman SE, Shabtai E, et al. Long-term cryostorage of sperm in a human sperm bank does not damage progressive motility concentration. Hum Reprod. 2010 Feb 22. [Epub ahead of print]

2. Clarke GN, Liu de Y, Baker HW. Recovery of human sperm motility and ability to interact with the human zona pellucida after more than 28 years of storage in liquid nitrogen. Fertil Steril. 2006 Sep;86(3):721-2.

3. Schover LR, Brey K, Lichtin A, Lipshultz LI, Jeha S. Oncologists’ attitudes and practices regarding banking sperm before cancer treatment. J Clin Oncol. 2002 Apr 1;20(7):1890-7.

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