Effect of liquid helium vitrification on cytoskeleton of immature cattle oocytes

The developmental potential and the changes in cytoskeleton structures in immature oocytes of cattle resulting from liquid helium (LHe) vitrification was evaluated in this study. Immature oocytes were randomly divided into three groups: fresh oocytes (negative control), oocytes vitrified in liquid nitrogen (LN group, positive control), and oocytes vitrified in LHe (LHe group). In Experiment 1, the proportions for normal morphology, maturation, cleavage, and blastocyst were greater in the LHe group than in the LN group (88.3% compared with 79.1%, 51.7% compared with 43.3%, 42.6% compared with 33.0%, and 11.0% compared with 4.7%, respectively; P<0.05), and the rates of oocyte development were greater in the control group (100%, 72.8%, 64.3%, and 40.3%) than in the vitrified groups (P<0.05). In Experiment 2, the effect of vitrification by LHe and LN on cytoskeleton of cattle oocytes was examined. The cytoskeleton had varying degrees of damage, and the negative influence of LHe vitrification on the cytoskeleton was less than that of LN vitrification (P<0.05), and the vitrified group had greater cytoskeleton degeneration than the control group (P<0.05). In conclusion, LHe vitrification reduced the negative effect of cryoinjury on cytoskeleton structure and improved the viability of immature oocytes of cattle compared with LN vitrification.