( Circulating stem cells play a minor rol...)Circulating stem cells play small role in lung repair

Reporting in today's edition of the journal Transplantation, lead author Dani Zander, M.D., of The University of Texas Medical School at Houston, and colleagues at the University of Florida College of Medicine found that less than 1 percent of a certain type of reparative lung stem cell originated in the bone marrow of the transplant recipient.

"It's possible in the future that circulating stem cells could be augmented to play a greater role in lung repair ?and people are looking at ways to do that. We found that the bulk of stem cell contribution to the repair process belongs to those stem cells normally found in the lungs rather than to circulating stem cells," said Zander, who is professor and vice chair of pathology and laboratory medicine.

Stem cells are produced during adulthood in the bone marrow, where some remain while others circulate in the blood stream. Their main function is to produce all of the elements of blood. Some studies show that circulating stem cells are capable of diffentiating into other types of tissue, including lung tissue, Zander said, and this study provides evidence of differentiation.

Researchers examined lung biopsy specimens from seven male transplant recipients who had received lungs from female donors. They analyzed the origins of type II pneumocytes, a stem cell involved in the complex processes of lung repair, found in the lung tissue. Donor lungs come with their own type II pneumocytes, which in this case have two X chromosomes. Cells produced by the recipient's bone marrow have an X and a Y (male) chromosome.

Lung transplant recipients are vulnerable to pulmonary injury from infections, rejection of the transplanted lung, ischemia, and other factors that damage the alveoli ?tiny holl
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Source:University of Texas Health Science Center at Houston