Development of a method of vitrification, thawing, and transfer of mammalian blastocysts using a single closed cryo-straw.

Background: There are different methods for cryopreservation of mammalian embryos with variable degrees of success. These methods require specific vessels for embryo vitrification, thawing, and transfer.

Objective: Here, we report a simple and inexpensive way to vitrify, thaw and transfer mammalian blastocysts in one straw.

Methods: This in-straw vitrification solution with microdrop (ISVDM) was compared with EM grid and normal 0.25 mL straw methods.

Results: There were no differences in the rates of re-expanded and hatching-to-hatched murine and bovine blastocysts exposed to 1, 0.5, and 0.3 M of sucrose in the diluent that was loaded into the straw. Low re-expanded and hatching-to-hatched rates of murine and bovine blastocysts were observed with PBS only. The pregnancy rates of control murine blastocysts (57.1%) and blastocysts exposed to 0.3 M sucrose in diluent and ISVDM (71.4%) were significantly higher (p < 0.05) than those exposed to 1, 0.5, and 0 M sucrose and those loaded into 0.25 mL straws. The rate of offspring delivery was highest in the control group. There was no significant difference (p < 0.05) in the rate of offspring delivery among ISVDM, 0.25 mL straw, and EM grid groups.

Conclusion: Our results indicate that vitrified embryos can be warmed and diluted in a single straw and that this one-step method enables farm animal embryo transfer without a microscope or other laboratory equipment.