The processes by which alveoli recover from damage are complex and incompletely understood, Zander said. Previous research showed that type II pneumocytes in the lungs are known to play a central role, but the role of the bone marrow-derived version of the cells is less clear.
"The lung has received relatively little investigation in this area," Zander said. "It's a challenging organ to study because the air-tissue interfaces make it difficult to separate different cell types."
Applying advanced research techniques that previously had been used to analyze liver and bone marrow transplant recipients, the team found that nine of 25 lung tissue specimens from five recipients contained small numbers of the male gender version of the type II pneumocytes. The proportion of Y chromosome-containing pneumocytes was less than 1 percent.
They also found a statistically significant relationship between the number of Y chromosome-containing pneumocytes and the incidence of acute cellular rejection in the tissue, suggesting that stem cell repopulation might be stimulated by greater degrees of injury to the lung.
The possibility that the presence of male gender pneumocytes in female lungs might result from an earlier pregnancy with a male fetus cannot be ruled out, Zander said. However, the association between the number of those cells found in the lung tissue with damage from rejection makes that unlikely.
There was no sign of fusion between the bone marrow-derived cells and the donor pneumocytes, said Zander, who holds the Harvey S. Rosenberg, M.D., Chair in Pathology and Laboratory Medicine at the medical school and serves on the Council of the American Society of Investigative Pathology, a prestigious organization focused upon investigating mechanisms of disease. She also was awarded the Young Clinical Scientist Award this year by the Associati