In Spain and La Jolla, California, a group of scientists at the Salk Institute successfully grew human cells inside a pig embryo. The goal of the research is to eventually grow entire human organs, which will be used for transplants, inside other animals. Scientists at Salk have already grown several rat organs inside mouse embryos. But this research has raised some ethical questions.
In 2015, the US stopped funding interspecies chimera research with taxpayer dollars. In genetics, a chimera is a naturally occurring phenomenon where a single organism has two or more different sets of DNA.
But an interspecies chimera contains DNA from two or more species. This has raised concerns over whether the pigs or other animals implanted with human cells will develop human brain functions.
Juan Carlos Izpisua Belmonte and his team have stated that they aim “to test ways to focus human cells on making specific tissues while avoiding any contribution to the brain, sperm, or eggs.”