Cloned pigs offer medicine a future source of organs and cells for human transplant

 

Scientists have successfully cloned five pigs, adding to the growing list of species that have been duplicated in this way. The group used technology similar to that used to produce Dolly the cloned sheep.

The five piglets were born on March 5th at Blacksburg, Virginia after scientists from PPL Therapeutics implanted cloned eggs in a sow. All the piglets are healthy and were created using cells taken from an adult pig.

The five females were named Millie, Christa, Alexis, Carrel and Dotcom, and are part of the firm's programme to produce pigs whose organs and cells could in the future be transplanted into human beings. Organ transfer across the species barrier is known as xeno-transplantation, and PPL has stated its intention to pursue this goal.

The company has the international rights to commercialise the cloning technology, first developed by the Roslin Institute in Edinburgh for the creation of Dolly. The piglets were tested to make sure they were genuine clones and DNA tests had confirmed that their genetic make-up was identical to that of the adult pig donor cell, according to the company.

The purpose behind the research is to produce animal organs that could be used in human transplant recipients. Cloning is central to this.

The object would be to genetically modify a pig to make its organs less likely to be rejected by a human recipient. The engineered pig would then be cloned so that its genetic changes would be carried forward from one generation to the next.

This would potentially provide an unlimited supply of organs, including hearts, kidneys, livers and cells from the pancreas whose absence causes diabetes in humans.

"An end to the chronic organ shortage is now in sight," PPL's managing director, Mr Ron James, said yesterday, adding that "all the known technical hurdles have now been overcome".

A company spokesman added that successfully cloning the pigs "is a major step in achieving PPL's xeno-graft objectives". He added that clinical trials were at least four years away.

No such procedures could be attempted, however, without clearance from the UK government's UK Xeno-transplantation Interim Regulatory Authority. This body is assessing the safety and necessity for animal-to-human transplants.

There were "currently no applications to UKXIRA for xeno-transplantation" according to a spokesman for the authority. "There are a large number of issues which UKXIRA still needs to consider before xeno-transplantation, such as the risks of cross-species infection."

The procedure raised serious issues of both safety and ethics, according to the head of the ethics, science and health policy group with the British Medical Association, Dr Vivienne Nathanson. The potential benefit to people who required transplants needed to be balanced against the possible risk for the population at large if viruses were released unwittingly, she said.

The previous minister for health, Mr Cowen, confirmed in a Dail question last November that he had no plans to introduce guidelines on xeno-transplantation. Nor, he said, were there any proposals before the Department to use the technology here.

Xeno-transplantation is not specifically mentioned in the latest ethical guidelines produced by the Medical Council, which regulates medical practice here. The guidelines were updated in 1998.

There is vigorous opposition to the use of xeno-transplantation on both safety and ethical grounds. The UK-based Doctors and Lawyers for Responsible Medicine (DLRM) has campaigned against the technology for some years, describing it as a transplant surgeon's dream but a virologist's nightmare, because of fears that a "silent virus" undetected in the pig could become dangerously active if introduced into humans.

"We are completely opposed to xeno-transplantation. There is a potential for viral transfer," according to Ms Joy Palmer of DLRM. "We are calling for a judicial review into animal experimentation in medical research," she said. "We consider it dangerous because of unknown viruses. Because they are unknown we can't be prepared."

The Irish Anti-Vivisection Society here is also against the use of the technology. "The society believes that it is totally unethical. It is just another form of vivisection," said Ms Yvonne Smalley for the Society.

Her objections were echoed by Ms Mary-Anne Bartlett of Compassion in World Farming. "It is unethical in relation to the animals but it is also dangerous in relation to humans," she said yesterday.