NEWS: New cryoprotectant-free, permeable capillary technique to help standardize sperm vitrification

A team of researchers has developed a new technology for cryoprotectant-free, sperm vitrification, using capillaries that have standard cylindrical shape and fixed diameter. The promising technique will help to standardize the vitrification procedure with precise, quantifiable volumes of spermatozoa.

Vladimir Isachenko from the Department of Obstetrics and Gynecology, University of Cologne, Germany, and coworkers, conducted the study using 68 ejaculates from 68 men who had oligoasthenoteratozoospermia. Each sample was aliquoted and divided into the following three groups after subjecting the spermatozoa to a swim-up protocol:
• Group 1 (control): noncryopreserved, fresh, swim-up sperms
• Group 2: 10 μL sperms cryopreserved with conventional slow freezing in a medium containing glycerol
• Group 3: 10 μL sperms vitrified in 50 μL plastic capillaries (custom-made, using hydrophobic material, to cool the suspension of sperms) containing 0.25 M sucrose culture medium

The findings of the study, published in the Journal of Andrology, have been listed in Table 1.

Table 1: Sperm Parameters following Conventional Slow Freezing and Capillary Vitrification

Parameters evaluated

Fresh spermatozoa

Conventional slow freezing

Capillary vitrification

Sperm motility after 1 hour (%)




Sperm motility after 24 hours (%)




Sperm motility after 48 hours (%)




Plasma membrane integrity (%)




Sperms with intact acrosome (%)




Cryo-capacitation like changes (%)




Based on the study findings, the researchers concluded that capillary vitrification, in comparison to conventional freezing, preserves sperm motility and plasma membrane integrity, and is associated with lesser damage to acrosomes. However, the vitrification technique did not possess preventive ability against cryo-capacitation when compared to conventional freezing.

Similar findings with respect to the effectiveness of cryoprotectant-free vitrification were reported by Jin et al (Zhonghua Nan Ke Xue, 2010). The researchers found vitrification using micro-drop method to be safe and effective for the cryopreservation of a low count of epididymal spermatozoa, obtained by percutaneous epididymal sperm aspiration.

The current technique of a swim-up protocol followed by aseptic capillary vitrification, results in spermatozoa free from seminal plasma and permeable cryoprotective agents, thus protecting the sperms from cryo-injuries. Additionally, it was noted that the sperms are immediately available for use after warming as they do not require any further treatment. However, the exposure of sperms to low temperatures can influence crucial signaling mechanisms Hence, to substantiate the use of capillaries for vitrification, further research is required to better understand the changes brought about by vitrification in its complexity, such as the targeting of specific pathways and membrane processes.


1. Isachenko V, Maettner R, Petrunkina AM, et al. Vitrification of Human ICSI/IVF Spermatozoa Without Cryoprotectants: New Capillary Technology. J Androl. 2011 Jun 30. [Epub ahead of print].

2. Jin L, Zheng JF, Liu Q, Ren XL, Hu J, Wei YL. Microdrop-vitrification for epididymal spermatozoa without cryoprotectants [in Chinese]. Zhonghua Nan Ke Xue. 2010 Dec;16(12):1089-94.

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