Caution on stem cell therapy( SALT LAKE CITY A single organ may ...)

SALT LAKE CITY A single organ may contain more than one type of adult stem cell a discovery that complicates prospects for using the versatile cells to replace damaged tissue as a treatment for disease, according to a new study from the laboratory of geneticist Mario Capecchi, the University of Utah's Nobel Laureate.

In the June 8 online issue of the journal Nature Genetics, Capecchi and geneticist Eugenio Sangiorgi report 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 12 inches long if stretched from end to end.

Adult stem cells are "undifferentiated" cells that can become any type of cell in the organ in which they are found. Medical researchers hope to transplant adult stem cells to treat various diseases. Examples include placing adult stem cells in the pancreas to replace damaged insulin-producing cells, in the heart to replace cardiac muscle cells killed by heart attack, and in the brain to replace dopamine-producing cells damaged in Parkinson's disease patients.

The new discovery "is important because people are talking about stem cell therapy; they want to stick in stem cells to treat disease," says Capecchi, a winner of the 2007 Nobel Prize in Physiology or Medicine.

"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 recognize this complexity," adds Capecchi, co-chair and distinguished professor of human genetics at the University of Utah and an investigator with the Howard Hughes Medical Institute.