The National Institutes of Health has taken steps to lift its moratorium on funding research that involves mixing human and animal cells. Such cross-species mixtures are called chimeras, after the creature from Greek mythology that was part lion, part goat, and part serpent.
As I explained earlier it is entirely ethical to grow human organs inside of pigs and sheep. Now the NIH agrees with me. Despite the NIH funding ban, some researchers have been conducting experiments to see if they can grow human organs in animals. For example, University of California, Davis developmental biologist Pablo Ross and his colleauges have experimented by injecting human stem cells into early-stage pig and sheep embryos in which genes for developing a pancreas have been disabled. The experiment seeks to find out if the human stem cells will occupy the vacant pancreas niche and generate a wholly human organ. The eventual goal of the work is to use induced pluripotent stem cells derived from the skin cells of patients to grow immunologically-matched replacement organs—hearts, livers, pancreases—in animals.
Some opponents of this type of research are concerned that human cells could migrate to animal brains and give them more human-like neural characteristics. Others worry that animals in which human cells have been transformed into gametes might mate and create human embryos. Proponents counter that there are techniques that could easily prevent such outcomes.
I argue the ethics of this research with long time anti-biotech activist Stuart Newman at KPCC's Airtalk program. Go here for the link to the audio.