Scientists at Duke University Medical Center have demonstrated they can grow human stem cells in the laboratory by blocking an enzyme that naturally triggers stem cells to mature and differentiate into specialized cells.

The discovery may enable scientists to rapidly grow stem cells and transplant them into patients with blood disorders, immune defects, and select genetic diseases, said the researchers.

Stem cells are the most flexible cells in the body, continually dividing into new stem cells or into specialized cells that carry out specific roles in the body. But little is known about how stem cells choose their fate. The Duke team focused on hematopoietic stem cells.

In their study, published on line and in the upcoming August 1, 2006, issue of the PNAS, the investigators discovered that an enzyme, aldehyde dehydrogenase (ALDH), stimulates hematopoietic stem cells to differentiate into blood or immune cells. They inhibited this enzyme in stem cell cultures and successfully increased the number of stem cells by 3.4 fold. Moreover, they demonstrated the new stem cells were capable of fully rebuilding the blood-forming and immune systems of immune-deficient mice.

“Our ability to treat human diseases is limited by our knowledge of how human stem cells determine their fate—that is, whether they maintain their ability to self-renew or whether they go on to become specialized cells,” said John Chute, M.D., associate professor of medicine in the Duke adult bone marrow and stem cell transplant program and the lead author of the study. “Unraveling the pathways that regulate self-renewal or differentiation in human stem cells can facilitate our ability to expand the growth of human stem cells for therapeutic uses.”