Stem cell research doubts

The potential of stem cell therapy is hotly debated

By BBC News Online's Ania Lichtarowicz

The use of adult stem cells to develop new transplant therapies might be seriously flawed, a group of scientists said on Wednesday.

The UK and US researchers claimed to have found abnormalities in the way the cells behaved when studied closely in the lab.

Our study indicates that calls for a halt to embryonic stem cell research are not scientifically justified

Prof Austin Smith

The scientists from Edinburgh and Gainesville said it was essential that work continued on embryonic sources of the special cells to see if they had better potential.

The medical world is hopeful that stem cells, the "master" cells in the body that can develop into other cell types, could form the basis of novel treatments for degenerative conditions such as Parkinson's and heart disease.

But the field is a controversial one because some scientists believe the best source of the cells will come from embryos that have been cloned from patients' own tissues.

Fluorescent markers

Recent studies have shown that adult stem cells from one tissue, such as blood, can give rise to other cell types, such as nerve and muscle.

The adult cells are thought to revert to a state similar to that of embryonic stem cells, which are even less specialised, before becoming the new cell types.

Scientists at Edinburgh University took adult stem cells from mouse brains and marked them with a fluorescent tag. The researchers then mixed them with embryonic stem cells in a petri dish.

And on first examination, it appeared that the adult brain cells had indeed reverted to the less specialized state of the cells placed alongside them. However, on closer examination, the new cells proliferating in the petri dish contained the florescent marker from the brain cells and the DNA from the embryonic stem cells.

In other words, the adult cells had simply fused with the embryonic ones - the new cells had twice the number of chromosomes ("packets" of genetic material).

If used in humans, these hybrid cells could have unknown effects on the body.

Similar results were seen by scientists at the University of Florida in Gainesville.

No restrictions on stem cell work

Professor Austin Smith, who was behind the British work, said if the study results were confirmed then it would put a big question mark against the use of adult stem cells.

"If nothing else, our study indicates that calls for a halt to embryonic stem cell research are not scientifically justified and confirms the far-sightedness of the UK legislature in approving embryonic stem cell derivation and research."

Stem cells have the potential to grow into nearly all the different kinds of tissue in the body, including nerves, bone, skin, muscle and organs.

Allied with cloning technology, they could prove revolutionary in organ regeneration - organ transplants can fail because the body's immune system rejects the new "foreign" tissue.

Using stem cells taken from a patient's embryo clone to create replacement cells could completely bypass the problem of tissue rejection.

Not applicable

But Professor Nick Wright, from Cancer Research UK, said that nothing shown in this research cast doubt in his mind on the results of adult stem cell research in animals.

"These are extremely preliminary results and are not applicable to adult stem cells," he told BBC News Online.

Professor Wright himself published research showing how damaged livers can be repaired using adult stem cells taken from bone marrow.

He said this new research had only been carried out in the test tube and not in living animals and so could only be applied to this one particular situation.

He added that polyploidy - having more than one set of chromosomes in a cell - occurred naturally in the liver anyway.

The Edinburgh/Gainesville work is published in the journal Nature.