快速冷凍比慢速冷凍更容易對精蟲DNA產生受損傷害
反覆冷凍解凍更會增加DNA受損機率

Cryobiology. 2016 Apr 25. pii: S0011-2240(16)30042-6. doi: 10.1016/j.cryobiol.2016.04.004. [Epub ahead of print]

The effect of two cryopreservation methods on human sperm DNA damage.

Liu T1, Gao J1, Zhou N2, Mo M2, Wang X2, Zhang X2, Yang H2, Chen Q2, Ao L2, Liu J2, Cui Z3, Cao J4.

Author information

Abstract

Several methods are currently available for selection when conducting sperm cryopreservation, however, these methods might cause different degrees of damage on sperm DNA. The aim of the this study is to compare the effects of storage at -80 °C (in ultra-low temperature refrigerator) and at -196 °C (in liquid nitrogen) on sperm DNA damage, thus to provide a reference for choosing the right method according to different aims. We randomly collected 28 semen samples from college students of Chongqing city. The samples stored at -80 °C were neat semen samples and the samples stored at -196 °C were mixed with additional cryoprotectants. Each sample was subjected to two freezing-thawing cycles, and the sperm DNA damage levels of fresh and thawed samples were measured by single cell gel electrophoresis (SCGE) and sperm chromatin structure assay (SCSA). Both SCGE and SCSA assays showed cryopreservation induced significant damage to sperm DNA. However, storage at -196 °C lead to more severe damage to sperm DNA than storage at -80 °C measured by SCSA. Sperm DNA damage increased simultaneously with the higher frequency of freezing-thawing cycles. We concluded that storage of neat semen samples at -80 °C had milder damage to sperm DNA than storage at -196 °C mixed with cryoprotectants. To avoid additional sperm DNA damage, repeated freezing and thawing should be prevented.