Growing organs from single cells is step nearer

Scientists are a step closer to growing organs in the laboratory from single cells after a study showed that individual brain cells can be made to develop into the tissue of the heart, muscles or intestines.

Scientists are a step closer to growing organs in the laboratory from single cells after a study showed that individual brain cells can be made to develop into the tissue of the heart, muscles or intestines.

The finding will give fresh impetus to research into the body's stem cells, which can develop into any one of the many dozens of specialised tissues. Stem cells are viewed as the key element in attempts to grow organs and tissues for future transplant operations.

Scientists at the Karolinska Institute in Stockholm have shown it is technically possible for the stem cells found in the adult brain to develop intoalmost any of the many specialised cells of the body.

Until recently, it was thought that only embryonic stem cells - found in the developing foetus - possessed this ability to develop into any tissue of any organ.

The study, published in the journal Science, showed that when the brain cells of adult mice are placed alongside embryonic cells, they can be reprogrammed to develop into quite different cell types.

It is thought the embryo could be sending out chemical signals that take control of the adult stem cells, although the scientist have not been able to isolate these signals.

"The short answer is that we have no clue," said Jonas Frisen, the leader of the Karolinska research team.

"We can speculate that the crucial elements are extracellular signals, or secretions from the embryonic cells. There is probably a cocktail of various factors involved, but we have no solid data yet about what these molecules are," he said.

By marking the brain cells the scientists were able to show that they had become fully integrated into other tissue types. "This demonstrates that an adult neural stem cell has a very broad developmental capacity and may potentially be used to generate a variety of cell types for transplantion in different diseases," the study said.

If scientists can isolate the signalling factors from the embryo that control stem cell development it may be possible to use adult stem cells for growing organs or tissues outside the body rather than using embryonic tissue, which is vigorously opposed by anti-abortion groups.

Liam Donaldson, the Government's chief medical officer, is preparing a report for the Department of Health into whether the cloning of human embryos should be permitted to harvest their stem cells for research.