Buried in the depths of healthy lung tissue, tiny groups of cells called alveoli stretch open to accommodate oxygen with each breath and then remove carbon dioxide during exhalation. Each alveolus is lined with a layer of epithelial cells that serve as a critical barrier -- keeping certain substances in and certain substances out -- so that the gas balance inside is appropriately maintained.
In contrast, inflammation due to injury or infection can make the border of epithelial cells become more porous than it should be. The increased permeability allows an often-deadly mix of substances, such as fluid and cells, to seep into and accumulate in the alveoli.
Despite extensive research on acute lung injury and acute respiratory distress syndrome, the mortality rate for patients remains high -- at about 40 percent, Lee said, and pharmacological therapies that reduce the severity of lung injury in experimental studies have not yet translated into effective clinical treatment options.
"Current treatments are primarily supportive care, and, therefore, innovative therapies are needed," explained co-author Arne P. Neyrinck.
The team decided to re-create the unhealthy lung conditions in the lab -- by culturing human alveolar cells and then chemically causing inflammation -- and to observe how the presence of bone marrow stem cells would change things.
"We then introduced mesenchymal stem cells without direct cell contact, and they churned out a lot of protein, called angiopoietin-1, which prevented the increase in lung epithelial permeability after the inflammatory injury," said Xiaohui Fang, the first author of the manuscript.
The authors say the findings are the first to demonstrate how mesenchymal stem cells revive the
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American Society for Biochemistry and Molecular Biology