The prospect of organ transplants from pigs to humans is said to have moved a step closer with a new success in animal cloning.
The people who brought us Dolly the cloned sheep have been at it again and have broadened the range of mammals that can be replicated using new technology.
Five little pigs, Millie, Christa, Alexis, Carrel and Dotcom, were delivered on March 5th at a research centre at Blacksburg, Virginia. They would be too cute for words but for the fact that this latest variety of clone has a potentially important but ethically fraught future, as a source of replacement organs for humans.
"An end to the chronic organ shortage is now in sight," said Mr Ron James, managing director of PPL Therapeutics, the company that holds the rights for cloning technology developed at the Roslin Institute in Edinburgh and which produced Dolly.
"It opens the door to making modified pigs whose organs and cells can be successfully transplanted into humans, the only near-solution to solving the worldwide organ shortage crisis," a PPL spokesman added.
Donation that crosses the species barrier is known as xeno-transplantation, and cloning is central to the development of pigs that could provide organs for humans. Human immune systems would reject these tissues, but researchers believe they can genetically engineer the pigs in order to trick the body into accepting animal organs.
The PPL spokesman said that some pig genes would be "knocked out" and several human genes would be inserted to lessen the degree of attack by the body's immune system. These engineered pigs would in turn be cloned so that duplicates could be produced, offering an endless supply of donor organs for human patients.
There are considerable safety issues to be addressed, however, and ethical questions on the use of animal tissues in humans. Opponents of xeno-transplantation believe that pigs could harbour "silent viruses" which, if transferred into a human host, could become active.
The five female piglets are all reported to be healthy and were created using cells from an adult pig, the company said. After the birth all were tested to make certain that they were genuine clones. DNA tests showed that they were genetically identical to the adult cell used to produce them.
Future source of organ transplants: page 9
