Gel-Loading Tip As Container for Vitrification of In Vitro-Produced Bovine Embryos.

Abstract

Recently, new vitrification methods for bovine embryos characterized by ultra-rapid cooling have been reported. The present study was undertaken to determine the availability of gel-loading tips as containers for vitrification of in vitro-produced bovine embryos at various developmental stages. Bovine embryos at Days-1, -2, -3, -4, -5, and -7 (the day of insemination was defined as Day-0) were placed in 0.6~0.7 μl of vitrification solution (20% ethylene glycol, 20% DMSO and 0.6 M sucrose) in a commercially available gel-loading tip, and cooled by immersing in liquid nitrogen. Survival of the vitrified embryos was evaluated by in vitro development into the blastocyst stage. There was no significant difference (P ≥0.05) between the survival rates for fresh and vitrified embryos at Day-1 (70.5 and 58.0%, respectively), Day-2 (75.9 and 68.3%, respectively), Day-3 (75.9 and 57.9%, respectively), Day-4 (80.0 and 67.6%, respectively), Day-5 (82.1 and 60.0%, respectively) and Day-7 (100 and 97.8%, respectively). And no significant differences were found between the total numbers of cells or the proportion of inner cell mass cells of blastocysts developed from fresh versus vitrified embryos. These results demonstrate that the gel-loading tip is applicable as a container for vitrification of in vitro-produced bovine embryos at the 2-cell to blastocyst stages.