Evaluation of Embryos Derived from in vitro Fertilized Oocytes Reconstructed by Meiosis-II Chromosome Transplantation from Aged Mice to Ooplasms of Young Mice

Background: To assess embryos derived by the transfer of meiosis-II chromosomes (M-II-t) from aged mice oocytes into ooplasms from younger mice to overcome the problem of age-related decline in female fertility. Materials and Methods: The developmental capacity, karyotype, and ultrastructure of reconstructed oocytes derived from meiosis-II chromosome transplantation from aged mice into the ooplasms of young mice by piezo-micromanipulation were assessed. Results: The survival rate of enucleated young oocytes was 54% and the percent of fertilized reconstructed oocytes was 23%. The rate of embryo development to the two-cell stage after cultivation was 40%. Since 82.4% of the analyzed embryos derived from reconstructed oocytes had condensed nuclei, it was not possible to analyze their chromosomal integrity. However, 17.6% of analyzable reconstructed old oocyte derived embryos (old-ODEs), had normal diploid sets of chromosomes. Major structural differences were not observed between young, old, and M-II-t derived two-cell embryos. Conclusion: Our findings suggested that ooplasms from younger mice may overcome age-associated problems in older mice.