Individual organs, however, may be built from more than one type of adult stem cell, according to new research from the University of Utah, a development that introduces a complicating factor in the race to translate stem-cell research into actual treatments.

The study's co-author, Nobel Prize-winning geneticist Mario Capecchi, nonetheless argues that adult stem cells will remain a vital component in the quest for treatments for such costly ailments as diabetes, heart disease and Parkinson's disease.

"To me [the research findings] say that making the organ is more complicated than we thought," said Capecchi, distinguished professor in the U.'s department of human genetics. "If you are going to develop therapies, you're going to have to take into consideration the possibility of different stem cells. That information doesn't make things more complicated, but more realistic. The more you know, the more likely you'll develop a new therapy."

Capecchi and co-author Eugenio Sangiorgi, a post-doctoral fellow in human genetics, published their findings in Nature Genetics.

Adult stem cells are committed to specific organs, whereas embryonic stem cells differentiate into almost any kind of organ.

While less flexible, adult stem cells are not loaded with the ethical baggage that comes with embryonic cells because experimenting with them does not require the destruction of what some believe is human life.

To learn more about the nature of adult stem cells, the U. researchers focused on mouse intestines, which offer a number of research advantages. This organ quickly renews itself because of the harsh digestive environment needed to break down food and extract nutrients.

"The intestine lining is completely under assault," Capecchi said. "That tissue turns over very rapidly, every two to five days, so it has a very active stem-cell population."

They inserted a marker gene Bmi1, found in E. coli bacteria, into intestinal stem cells and observed their development in mice. Contrary to expectations, the marker gene, which "expresses" itself by turning the white lining blue, did not appear uniformly down the 12-inch length of the small intestine.

Instead the blue cells concentrated in the upper third while the lower third appeared free of blue marker.

"There are probably different stem cells in the small intestine doing different things," Sangiorgi said.

Capecchi contends these findings should not devalue the medical usefulness of adult stem cells, which hold inherent advantages that have nothing to do with the politics that vex embryonic stem-cell research.

"You should always be working with both systems. One may prove to be better in some situations and the other better in other situations," he said.

"The nice thing about embryonic stem cells is they are very general; they can participate in making any type of organ. But you have to teach embryonic stem cells to become intestinal cells while adult stem cells already know how to do it. With adult cells, you are taking advantage of what biology has already acquired."

bmaffly@sltrib.com