Harvesting of Mouse Embryos at 0.5 Dpc as a Tool to Reduce Animal Use: Data from C57BL/6J, B6*129 and FVB/NJ Strains

Abstract
Superovulation is used to stimulate the production and release of large amounts of oocytes in mice by using two hormones that mimic FSH (PMSG) and LH (hCG) effects. Since superovulation can have a negative impact on oocyte and embryo development, this investigation aimed to compare two alternatives for 2-cells embryo collection in order to reduce the number of females and to benefit from the superovulation process. Data from mouse embryo collection from our facility was analyzed to compare the number of 2-cells embryos collected at 1.5 dpc and the number of 2-cells embryos obtained after overnight incubation of 1-cell embryos, collected at 0.5 dpc. Genetically modified mouse strains with a similar background (C57BL/6J, B6*129 and FVB/NJ) were analyzed and for strains at a C57BL/6J and B6*129 background, the number of 2-cells embryos obtained after incubation was significantly higher when compared to the number of 2-cells embryos collected at 1.5 dpc (1.4-fold and 1.7-fold, respectively). C57BL/6J wild type mice had similar results with a higher number of 2-cells embryos when collection was performed at 0.5 dpc followed by incubation (1.4-fold). These results can help the planning of 2-cells embryo harvesting by reducing the number of females needed for this procedure.