Scientists grow human organs inside pigs

Scientists are attempting to grow human organs inside pigs.

In an attempt to solve the shortage for transplants, US researchers have injected human stem cells into pig embryos to produce human-pig embryos known as chimeras.

The chimeric embryos will look like a normal pig's embryo, but one of their organs - the pancreas - will be made completely from human cells, according to the team from the University of California.

They will be allowed to develop in the sows for 28 days before the pregnancies are terminated and the tissue removed for analysis.

"Our hope is that this pig embryo will develop normally but the pancreas will be made almost exclusively out of human cells and could be compatible with a patient for transplantation," Pablo Ross, a reproductive biologist who is leading the research, told the BBC.

But the plans are highly controversial and last year the main US medical research agency, the National Institutes of Health, banned funding for such experiments.

Peter Stevenson from Compassion in World Farming told the BBC that he was concerned it would lead to "a new source of animal suffering".

Critics also say it could lead to the development of organ farms.

Other concerns relate to the possibility that the implanted human cells might migrate to the developing pig's brain and make it more human.