When fast-aging elderly mice with a usual lifespan of 21 days were injected with stem cells from younger mice at the Institute for Regenerative Medicine in Pittsburgh, the results were staggering. Given the injection approximately four days before they were expected to die, not only did the elderly mice live — they lived threefold their normal lifespan, sticking around for 71 days. In human terms, that would be the equivalent of an 80-year-old living to be 200.
While all the donor cells were from rhesus monkeys, the researchers combined up to six distinct embryos into three baby monkeys. According to Dr. Mitalipov, “The cells never fuse, but they stay together and work together to form tissues and organs.” Chimera species are used in order to understand the role specific genes play in embryonic development and may lead to a better understanding of genetic mutation in humans.