In a world-first, scientists in China created pig-primate chimeras. The two piglets looked like normal baby pigs but had primate cells, and they died within a week.
The point of the research is to ultimately grow human organs in animals for transplantation. This type of biology sparks controversial debates, and this most recent experiment shows that there is still a long way to go before this method of growing organs is achieved.
The first monkey-pig hybrids
"This is the first report of full-term pig-monkey chimeras," said Tang Hai at the State Key Laboratory of Stem Cell and Reproductive Biology in Beijing.
This development brings up ethical concerns but could prove useful for organ transplantation in the future.
Monkey-pigs!!!— Dr Darren Saunders (@whereisdaz) December 9, 2019
There’s a reasonable motivation for investigating pig/primate chimeras... but it’s always going to be reported with Frankenstein framing. https://t.co/wdlSOC3r3L
Hai and his team of scientists modified cynomolgus monkey cells and injected them into pig embryos five days after fertilization.
Over 4,000 embryos were implanted. From these thousands of embryos, 10 piglets were born, two of which were chimeras. All died within a week of being born. In the two chimeras, a number of tissues partly consisted of monkey cells.
For instance, the piglets' heart, liver, spleen, lung, and skin all showed a proportion, albeit low, of monkey cells.
Hai stated that the reason behind the piglets' death remains a mystery. However, given all 10 piglets died — chimeric and non-chimeric — he believes the reason may be because of IVF, and not the chimerism.
The team is now looking to create more piglets with a higher proportion of monkey cells.
This type of research is controversial, for instance, stem cell biologist Paul Knoepfler at the University of California, Davis said "Given the extremely low chimeric efficiency and the deaths of all the animals, I actually see this as fairly discouraging."
Knoepfler is one of many who doesn't believe this method of growing organs for transplantation within animals is a viable option.
The study was published in Protein & Cell in November.