The aptly named Chimero is one of the world's first chimeric monkeys. | Jim Newman/OHSU
The world’s first chimeric monkeys were created in a laboratory last year, and they offer surprising new insights into embryonic stem cell therapy: One reason for often-poor treatment outcomes may be that we’re using embryos that are, strangely, just too old.
Researchers have long been able to create chimeras—offspring with more than two parents—in rodents like mice by combining embryos so tiny they consist of only eight cells in all. At this early stage of their development, embryos are made of pluripotent stem cells, each of which can give rise to many, though not all, tissue types.
Previous attempts to do the same in monkeys, however, have failed—a disappointment because monkeys are more similar than mice to humans, and thus likely a better harbinger of how stem cell treatments will fare in people.
“Stem cells ...
