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Q&A: Therapeutic human cloning

Cloning could produce perfect-match tissue

The law on human cloning in the UK is to be relaxed to allow scientists to take cells from early-stage embryos and use them to grow skin and other tissue.

Final approval of so-called therapeutic cloning will have to pass a free vote in Parliament first, but ministers believe this very promising, but highly controversial, technology should be pursued.

BBC News Online's science editor Dr David Whitehouse answers questions on the subject.

Q. What is therapeutic cloning?

A. Scientists would like to create human embryos in the lab and mine them for special cells that can be used in revolutionary medical treatments. One often hears the term embryo cloning in relation to this work, but this is a misuse of the term and gives a wrong impression of what actually takes place. Scientists are not copying embryos. What they do is take the genetic material from a cell in an adult's body and fuse it with an empty egg cell. With the right trigger, this new cell can then be persuaded to develop into an embryo. It is the same basic technology that gave us Dolly the sheep.

Q. Why do researchers want to do it?

A. To extract so-called embryonic stem cells. These are the master cells that have the potential to develop into any other type of cell in the body. For example, they could develop into nerve tissue, blood, heart muscle and even brain cells. Scientists have been trying to isolate and culture these special cells in the lab for many years. When they finally achieved it in 1998, it was hailed as one of the great breakthroughs in modern research.

Researchers believe stem cells can provide us with a ready supply of replacement tissue. Initially, individual cells would be implanted into our bodies to repair the damage caused by degenerative illnesses like heart disease. Ultimately, however, it may be possible to persuade stem cells to grow into complete organs. But if this is possible, it is many years away.

Q. Why is cloning such an important part of this?

A. It is important because it would allow the creation of perfect-match tissue. At the moment, if you have a transplant your body will try to reject the donated cells because it sees them as foreign. Doctors dampen this immune response by prescribing powerful anti-rejection drugs that patients must take for life. But the cells created through therapeutic cloning would not have this problem. They would be derived from the patient him/herself and the immune system would recognise the cells as the body's own.

This approach could end, for example, a leukaemia patient's desperate search for the right bone marrow donor. With therapeutic cloning, doctors would create perfectly matched bone marrow using perhaps the patient's own skin cells.

Q. What other diseases could be tackled this way?

A. Certainly any degenerative disease where one cell type has gone wrong. Scientists are very confident new nerve cells can be transplanted into sufferers of Parkinson's and Alzheimer's disease. New heart muscle could repair damaged hearts.

Q. Can stem cells be obtained any other way?

A. Embryonic stem cells can only be obtained from embryos, but it is possible to get so-called adult stem cells from adults. It is not clear whether these have the complete flexibility of the embryonic cells. Although research has shown for example that adult bone marrow cells can become liver cells, we may need embryonic stem cells to get the full range of body cell types.

Q. What do the opponents say?

A. The breakthrough research on embryonic stem cells was done on aborted foetuses and unwanted embryos from IVF treatment. Some groups argue that a human embryo, even the very small clump of cells being talked about here, is a human life and as such is sacrosanct. They see it as outrageous that scientists should be allowed to create something which has life merely to discard it after they have "harvested" some important cells.

Q. Is there a solution here?

A. Possibly. With more research, we may find that adult stem cells are just as useful and flexible and this would negate the need for embryos. Also, the scientists who created Dolly the sheep and the researchers who first isolated the embryonic stem cells are combing their knowledge. They think it might be possible to "reprogram" an adult cell - even one as specialised as a skin cell, for example - to become any other cell type in the body. This sort of technology is far from being realised and would also require, in the short term, work on embryos to learn some of the secrets of how early cells are controlled.