Stem Cells Promise Liver Repair

Wednesday, 19 July, 2000, 18:04 GMT 19:04 UK
By BBC News Online science editor Dr David Whitehouse

UK scientists have shown how cells from transplanted bone marrow can turn into liver tissue.

The finding raises the prospect of regenerating diseased livers. It may also pave the way for new gene-therapy treatments. Researchers already knew that so-called stem cells in bone marrow were responsible for generating blood cells. The new discovery that stem cells can also turn into liver cells inside patients means that marrow stem cells could eventually be used to repair damaged livers as well.

Stem cells are special cells which have not yet become totally specialized to one role in the body. The techniques developed to isolate these cells are regarded as being among the most important scientific discoveries made in recent years.

Drug side effects

Professor Nick Wright, of the Imperial Cancer Research Fund (ICRF), said: “We may be able to stimulate liver regeneration using cells from the patient’s own bone marrow.”  And he added: “This would be particularly useful for patients whose livers have been damaged due to drug side effects, or through surgery to remove cancers that have spread to the liver, and where there is insufficient functioning liver remaining.”  Professor Wright’s team says that livers that are defective because of a faulty gene could one day be repaired using stem cells that have been given a working copy of the gene.

But it is the prospect of being able to generate new liver tissue using the patient’s own stem cells that really excites the scientists.

“We could avoid problems with current liver transplants where the patient’s body rejects the foreign organ,” said Professor Wright.

Patient’s blood

The scientists conducted a genetic analysis of liver cells from female patients who had received bone-marrow transplants from male donors. Liver cells from male patients who had been given whole livers from female donors were also examined. Using a DNA probe that identifies male cells, the scientists found male liver cells in the female patients, indicating that male bone-marrow stem cells had repopulated the liver. Male liver cells were also found in a female-donated liver, showing that the liver had accepted bone-marrow stem cells from the male recipient.

Dr Malcolm Alison, a research pathologist based at Imperial College School of Medicine, said: “We already knew from laboratory experiments that liver cells can be derived from bone-marrow stem cells, but we had to show this happened in humans as well.

“Adult stem cells offer great promise in medicine as they may generate the full spectrum of cell types needed to repair a damaged organ. Working with human blood-forming stem cells is particularly attractive as they can be harvested rapidly from a patient’s own blood.”

Ultimate flexibility

Using adult stem cells will also avoid the ethical problems associated with even earlier cell types.

Embryonic stem cells can, in theory, be made to develop into any cell type in the body – they would offer the ultimate flexibility. But their only source is from aborted tissue or discarded test-tube embryos, and several campaign groups have vowed to fight any law change that would permit the widespread harvesting of stem cells in these areas.

Professor Wright said: “If we can understand the mechanisms and identify the switches that trigger adult stem cells into regenerating specific tissues, the future could see a revolution in transplant medicine.”

Around 5,000 people in the UK are awaiting organ transplants, and for many an organ will almost certainly not be found in time. Patients will inevitably die waiting for a suitable donor.

“Eventually, adult stem cell technology may overcome this problem,” Professor Wright said. “Clearly there is still much work to be done but the potential for therapies is enormous.”

The work, reported in the journal Nature, was carried out in London by teams from the Imperial Cancer Research Fund, Imperial College School of Medicine, and the Royal Free Hospital.