Purpose: This project was to determine whether oocytes isolated from virgin aged mice, up to 18 months old, are competent to undergo cytoplasmic maturation in vitro and undergo fertilization and embryonic development. If so, oocyte maturation in vitro could be used as a strategy to rescue valuable genetic resources.
Results: Although the number of oocytes recovered from mice was greatly reduced with increasing age, the percentage of oocytes that underwent fertilization, cleavage, and development to the blastocyst stage was essentially unchanged up to 18 months of age. The success of cleavage to the two-cell stage was greater after maturation in vitro (81%) than gonadotropin-induced maturation in vivo (55%). About 20% (20/106) of the embryos derived from oocytes isolated from 18-month-old mice developed to term after embryo transfer.
Conclusion: Oocytes from virgin aged mice undergo normal cytoplasmic maturation in vitro. Higher percentages of oocytes from aged mice cleave to the two-cell stage after spontaneous maturation in vitro than after gonadotropin-induced maturation in vivo. Therefore, in vitro maturation and fertilization of oocytes could be used to rescue valuable genetic resources that might otherwise be lost because of age-related infertility.