Improving native human sperm freezing protection by using a modified vitrification method
Dai Zhou1,2, Xing-Ming Wang1, Rui-Xue Li1, Yi-Ze Wang1, Yuan-Chi Chao1, Zhi-Zhong Liu1,3, Zeng-Hui Huang1,2, Hong-Chuan Nie1,2, Wen-Bing Zhu1,2, Yue-Qiu Tan1,2, Li-Qing Fan1,2
1 Institute of Reproduction and Stem Cell Engineering, School of Basic Medicine Science, Central South University, Changsha 410000, China
2 Reproductive and Genetic Hospital of CITIC-Xiangya, Changsha 410000, China
3 Department of Urology, Hunan Cancer Hospital, Changsha 410000, China
Institute of Reproduction and Stem Cell Engineering, School of Basic Medicine Science, Central South University; Reproductive and Genetic Hospital of CITIC-Xiangya, Changsha 410000
Source of Support: None, Conflict of Interest: None
Slow freezing is the most commonly used technique for the cryopreservation of spermatozoa in clinical practice. However, it has been shown to have a negative impact on sperm function and structure. Vitrification as a successful alternative method has been proved to have better protective effects on human embryos, but vitrification of spermatozoa is still subject to low recovery rates. In this study, a modified vitrification method for native spermatozoa was developed. A total of 28 semen samples were included; each sample was divided into three equal parts and assigned to fresh, slow freezing, and vitrification groups. Sperm vitality, motility, morphology, DNA integrity, and acrosome reaction were assessed for each of the groups. The results showed that vitrification achieves better results for several sperm protection parameters than slow freezing; vitrification achieves a higher recovery rate (P < 0.05), motility (P <0.05), morphology (P <0.05), and curve line velocity (P <0.05) than slow freezing. Furthermore, DNA fragmentation was decreased (P <0.05) and better acrosome protection (P <0.05) was exhibited in the spermatozoa after vitrification. Principal component analysis of all sperm parameters revealed that the vitrification cluster was closer to the fresh cluster, indicating that spermatozoa are better preserved through vitrification. In conclusion, while both slow freezing and vitrification have negative effects on sperm function and structure, the vitrification protocol described here had a relatively better recovery rate (65.8%) and showed improved preservation of several sperm quality parameters compared with slow freezing.