Effects of Vitrification Temperatures and Concentration of Cryoprotective Agents on the Cytoskeleton in Bovine Immature Oocytes

Abstract

The objective of the research was to evaluate the effect of vitrification temperatures (VTs) and concentration of cryoprotective agents (CPAs) on the cytoskeleton of bovine immature oocytes (BIOs). Bovine cumulus oocyte complexes (COCs) were collected and divided randomly into five groups: (a) fresh control group, (b) oocytes vitrified in liquid helium (LHe; −269◦C with 5.6 M CPAs, (c) oocytes vitrified in LHe (−269◦C with 6.6 M CPAs, (d) oocytes vitrified in liquid nitrogen (LN; −196 ◦C with 5.6 M CPAs, (e) oocytes vitrified in LN (−196◦C with 6.6 M CPAs. The results showed that the developmental level of BIOs in the LHe 5.6 M group was the highest among the four vitrification groups, and the maturation rate and cleavage rate were significantly higher than the other three vitrification groups (P < 0.05). With further experiments, the normal rate of microfilament and spindle in the LHe 5.6 M group was the highest compared with the other three vitrification groups. It was concluded that lower VT (−269◦C and lower CPAs (5.6 M) could significantly reduce damage to the cytoskeleton, which had a positive effect on the development of oocytes after vitrification.