Stem cells that are able to regenerate damaged lung tissue have been discovered by scientists. The brochioalveolar stem cells (BASCs), naturally present in the lungs of rodents and humans, are capable of rebuilding alveoli - the small air sacs in lungs.
Professor Frank McKeon, from the Genome Institute in Singapore and Harvard Medical School, hopes that the discovery of the stem cells will lead to new treatments for people with damaged lungs. 'We have found that the lungs do in fact have a robust potential for regeneration, and we've identified the specific stem cells responsible', he said.
The stem cells were isolated after researchers infected mice with a form of the H1N1 influenza virus - similar to the virus that caused the 1918 flu pandemic - to observe lung damage and regeneration. The virus initially damaged more than half of the lung alveolar tissue, but the alveoli had regenerated by three months after infection. There was no sign of lung fibrosis, a chronic scarring condition commonly seen after other forms of lung damage.
'We saw essentially pristine lungs at three months after a loss of 50 percent of lung tissue', said Professor McKeon, who led the team.
The cells multiply rapidly, migrate towards areas of damage in the lungs and assemble into 'pods' that go on to form new alveoli. Similar stem cells with the ability to multiply and form pod-like structures were also isolated in human lung tissue.
Researchers are now working to identify the signalling molecules and growth factors that promote lung regeneration at repair sites. Such work could result in improved therapies for acute and chronic lung damage caused by conditions such as asthma, chronic obstructive pulmonary disease and pulmonary fibrosis.
'These findings suggest new cell- and factor-based strategies for enhancing lung regeneration following acute damage from infection, and even in chronic conditions such as pulmonary fibrosis', said Professor McKeon. 'It's too early to say common lung diseases will be treatable, but it's a start, and there's a lot of potential'.
In another study, also published in the journal Cell, researchers at the Howard Hughes Medical Institute and Weill Cornell Medical College identified a key signalling molecule involved in regenerating alveoli and lung tissue.
The molecule - matrix metalloproteinase 14 (MMP14) - is required for the growth of new alveoli. When one lung is removed, new alveoli are known to grow in the other intact lung. But when the researchers blocked the activity of MMP14, the lung's regenerative capacity was impaired. Reintroducing MMP14 restored regeneration. The researchers found that cells in the blood vessels of the lungs produced MMP14.'The key is that the blood vessels turn on the pathways for regeneration', said Dr Shahin Rafii, who led the research; 'the therapeutic potential is tremendous'.