Cloned Piglets Bring Animal-Human Transplants Closer

July 7, 2008 - 8:02 PM

London ( - The wholesale provision of animal organs for human transplant has moved a step closer with the birth in the United States of the world's first cloned piglets.

The Scottish company that created the first successfully cloned mammal, Dolly the sheep, Tuesday announced the birth of Millie, Christa, Alexis, Carrel and Dotcom.

The five female pigs were born on March 5, the result of new procedures developed by the Blacksburg, VA.-based staff of the Edinburgh-based company PPL Therapeutics.

Independent blood tests from the five showed their DNA to be identical to that of the cells used to produce them, although different from the DNA of the surrogate mother.

If approved for human transplants, said PPL, it hopes such animals will help meet the anticipated demand for pig organs. Analysts predict the market could be worth more than $6 billion.

But there are ethical concerns about using pig's organs in humans.

"Even in the cause of medical research, there are lines to be drawn," Dr. Donald Bruce, director of the Church of Scotland's Society Religion & Technology Project told

"Xenotransplantation would be justified only if the efficacy in quality and length of life was so great that it justified what would otherwise be an unacceptable intervention in one of God's creatures with whom we share the planet."

Bruce said, "xenotransplantation represents a completely different way of using animals from anything humans have done before ... not everything we can do to animals technically, should be done ethically."

Fears of health risks arising from the possible transmission of dangerous "retroviruses" from pigs to humans have also been raised by the British Medical Association (BMA).

"What we are talking about is a technique that carries risks for the population at large, as well as the potential to save lives," said the BMA's Dr. Vivienne Nathanson.

PPL said in a statement the cloning breakthrough "opens the door to making modified pigs whose organs and cells can be successfully transplanted into humans - the only near-term solution to solving the worldwide organ shortage crisis."

In the United States alone, some 50,000 patients are awaiting transplants from less than 5,000 annual donors, and more than 3,000 people die each year because no donor can be found.

Tissue from pigs is already used in heart valve operations, but whole organ transplants pose problems because of donor rejection.

The genes of cloned animals, however, can reportedly be manipulated to minimize this risk.

PPL believes clinical trials into the use of animal organs for human transplant, known as xenotransplantation, could begin in about four years.

Not everyone is happy with the idea, however. Six weeks ago, European Union lawmakers called for a moratorium on xenotransplantation until the new technology was evaluated and guidelines were established and agreed upon.

The Council of Europe's parliament called for a worldwide ban, saying that despite the possible benefits, there could be a serious risk of disease transfer.

Virulent viral diseases such as Ebola and Marburg have been known to transmit from monkeys to humans. It has recently been argued that a link exists between "mad cow" The British body regulating xenotransplantation disease and the human disorder called Creuzfeldt Jakob.

The UK Xenotransplantation Interim Regulatory Authority (UKXIRA) announced recently that strict guidelines would be needed to ensure dangerous viruses could not be passed on to humans.

Among other regulations under consideration was one requiring the recipients of animal organs to sign a pledge committing themselves not to have children for life, nor ever to donate blood.

Their sexual partners may also have to be registered and monitored by health authorities.

The British government responded cautiously to the news Tuesday.

"Clinical trials involving humans will only be allowed to take place if the government, advised by the UKXIRA, is fully satisfied that the evidence put forward is sufficient to justify the particular xenotransplantation procedure proposed," Health Department spokesperson Emma Ward told

"There are a large number of issues which UKXIRA still needs to consider before xenotransplantation, such as the risks of cross-species infection," she said.

"This is an interesting development. The company itself says they are four years away from clinical trials and if they do so in this country, they will need the permission of UKXIRA."

PPL said the work was partly funded by a U.S. Government grant awarded to produce what is known as a "knock-out" pig - one in which specific genes are inactivated to help prevent the human immune system from rejecting an implanted pig organ.

But because only individual cells, and not whole animals, can have these genes "knocked out," scientists need to use the altered cells to create clones, in order to obtain entire organs suitable for human transplant.

"An end to the chronic organ shortage is now in sight," PPL managing director Ron James said. "The next step for PPL is to repeat the pig cloning experiment to produce knock-out pigs."

A recent report by Duke University Medical Center in North Carolina described how and why the human body usually rejects an animal organ.

"Within minutes, an animal organ is recognized and targeted by protein sentries that circulate in the blood. These sentries flag the animal tissue and set in motion a cascade of events, involving the complement system, that cut off the blood supply to the organ and basically starve it to death."

PPL said the names of the piglets were chosen by its scientists in Virginia. Millie, the first to be born, was named after the millennium. Christa, Alexa and Carrel were named after Christian Barnard, the South African heart transplant pioneer, and the 1912 Nobel prizewinner Alexis Carrel.

The fifth piglet came as something of a surprise - she may have been hidden behind her sisters during an ultrasound - and was duly named Dotcom, or Dotty for short.

Quipped James: "Any association with dotcoms right now seems to have a very positive influence on a company's valuation."