Spatula Montevideo Device for the Vitrification of Mammalian Embryos

This study describes an efficient and cost-effective vitrification method for mouse and sheep embryo cryopreservation known as the Spatula Montevideo (MVD). This protocol utilizes a homemade spatula as the carrier device, which is prepared with a gel-loader tip. Embryos are rapidly equilibrated in two homemade cryoprotectant solutions of increasing concentration, loaded into the spatula, and then directly immersed in liquid nitrogen. Approximately 30-40 pre-implantation stage mouse embryos can be loaded on the spatula, which is subsequently sealed with a 0.5 mL straw. The use of spatulas instead of cryotubes, which are frequently used to store vitrified embryos, optimizes space in the liquid nitrogen dewars. Additionally, the warming process requires only a homemade sucrose solution of decreasing concentration to rehydrate the embryos and restore their morphology. Our laboratory has successfully used the Spatula Montevideo for mouse and sheep pre-implantation embryos for over 10 years. The Spatula Montevideo has demonstrated an average recovery rate (recovered/vitrified embryos) of 84% and a survival rate (viable/recovered embryos) of 97% in mouse embryos. Vitrification of murine embryos has yielded better results than slow freezing, although no differences in reproductive outcomes (pregnancy, delivery, and birth rates) have been observed. In sheep embryos, similar survival and embryo development rates have been achieved with Spatula Montevideo compared to a commercial device. Although the pregnancy rate was higher for the commercial device, the lamb survival rate was not significantly different among the devices. The Spatula Montevideo vitrification method is a straightforward cryopreservation technique that can be used to store surplus embryos, back up genetically modified mouse lines and sheep models, and facilitate their exchange among researchers worldwide.