Pig organ transplants much closer

The piglets were produced using nuclear transfer

By BBC News Online science editor Dr David Whitehouse

It is no surprise that the scientists who gave us Dolly, the first cloned mammal, have now given us a litter of cloned pigs.

The pigs join the sheep, cows, goats and mice that have already been copied.

Cloned and genetically-modified pigs will be important. A pig's heart is about the same size and has about the same power output as a human heart. What is more, scientists understand the few steps they need to take to genetically-modify pig tissue so that it will not be rejected by the human immune system after transplantation.

But there are still major problems and it will be years before we know if it will be possible to use pig organs this way. There is the fear that viruses that only affect pigs may jump into humans. However, some scientists say that if this was possible it would have happened by now as humans and pigs have lived in close proximity for millennia.

The first human tests, on patients with no other hope of survival, could begin within 18 months, although specially-bred pigs using the 'Dolly' technique would take a year or so longer to produce.

Technical problems

So the time when a human is kept alive by a pig's heart is not so far away.

Pigs are sometimes called "horizontal humans"

Similar things have been tried before. Years ago, baboon hearts were used in humans with little success. Back then, scientists just did not know the obstacles they were going to encounter.

Perhaps as significant as the cloned pigs is the research project to clone primates, mankind's nearest living relatives.

Already, a genetically-modified monkey has been cloned and more monkey clones will hit the headlines later this year.

There is no doubt that a human could be cloned this way but scientists recoil at the idea - for now - and say it is not necessary.

Cell technologies

But cloning at the level of individual cells offers great promise and could revolutionise medicine.

We will gain fundamental insights into how cells behave from the projects currently reading the genetic blueprint of animals, plants and humans.

This data will be combined with the power of cloning and our rapidly increasing knowledge of "stem-cells" - cells which transform into any other type of cell.

In 20 years' time, we may not be thinking of cloning animals at all, except to save endangered species. Instead, we will be cloning cells. If you need a new heart, liver, lung tissue or even brain tissue, it will be cloned from you own cells and grown up in the lab.

In the 20th Century, humankind exerted unprecedented control over their environment. In the 21st Century, we will extend that control to ourselves.