Nobel winner finds complication for stem cell therapy

A single organ may contain more than one type of adult stem cell — a discovery that complicates prospects for using stem cells to replace damaged tissue as a treatment for disease, according to a study by Nobel Laureate Prof Mario Capecchi.

In the 8 June online issue of the journal Nature Genetics, Capecchi and geneticist Eugenio Sangiorgi reported that when they used a gene named Bmi1 to mark the presence of adult stem cells in the intestines of mice, they were surprised to find the specific cells mostly in the upper third of the mouse intestine.

That indicates at least one or two other types of adult stem cells must exist to maintain and repair the middle and lower thirds of the mouse's guts. The small intestine in a mouse is almost 30 centimetres long if stretched from end to end.

The new discovery "is important because people are talking about stem cell therapy; they want to stick in stem cells to treat disease", said Capecchi, a winner of the 2007 Nobel Prize in Physiology or Medicine and co-chair of human genetics at the University of Utah, US.

"People always thought about a uniform stem cell population in each organ, but now we are saying there are multiple stem cell populations in a given organ. So if you're going to do therapy, you have to recognise this complexity," he said.

"There are probably different stem cells in the small intestine doing different things," said fellow author Sangiorgi, a postdoctoral fellow in human genetics.

Capecchi said that if more than one kind of adult stem cell is required to generate the intestinal lining, it is probably true for other organs as well.

Adult stem cells are seen as an alternative to the controversial embryonic stem cells, which are able to become any kind of cell in the body — not just in a given organ — but raise concerns amongst anti-abortion groups.

Capecchi won the Nobel — with Sir Martin Evans and Oliver Smithies — for developing gene targeting, a method of using embryonic stem cells to ‘knock out’ genes in mice, then observing any changes to determine the gene's normal function.

For more information, visit the University of Utah website.