Lung Health News, Spring / Summer 2008
(Research Matters, Lung Health News, Spring/Summer 2008)
The lungs are complex organs that extract oxygen from the air we breathe. They are internal organs, yet they are continually exposed to the outside world. With every breath, foreign substances enter our bodies, such as pollen, dust, smoke, air pollutants, viruses and bacteria. These assaults on our lungs can take their toll.
“The misdirected repair following lung injury is a huge problem,” says Joseph Lin, MD, who is studying the role of alveolar stem cells in lung repair. “The most common examples of this misdirected repair are emphysema and pulmonary fibrosis.”
Dr. Lin was one of 12 researchers funded by the American Lung Association of California’s research program in fiscal year 2006-2007. He is trying to determine how the alveolar stem cells repair lung tissue and why some lungs do a good job of repairing themselves while others don’t.
Dr. Lin believes these stem cells are produced by the lung during development and set aside in a “reservoir” to be used for needed repairs if the alveoli are injured.
The alveoli are the tiny air sacs at the end of the small bronchial tubes in the lungs where the exchange of oxygen occurs. Oxygen passes through the alveoli’s thin walls into blood running through small blood vessels. At the same time, carbon dioxide passes from the blood into the alveoli, where it can be expelled from the body through the airways.
“The alveoli cover more than 90 percent of the surface of the lung,” Dr. Lin says. “They are the most fragile part and the most difficult to repair.”
Lung Disease, Cancer Treatments Can Damage Air Sacs
The alveoli can be damaged by the inflammation that results from diseases like emphysema and pneumonia. Dr. Lin has also treated many lung cancer patients whose lungs were injured by chemotherapy and radiation treatments, which is why he decided to study lung repair.
“This damage literally leaves the lungs with holes in them,” he says. “They look like Swiss cheese.”
The alveoli provide structural support for the lungs, so when there are too many holes, the airways collapse. The lungs lose their ability to exchange gas and keep the airways open.
“Right now, we can’t do enough to help these patients,” says Dr. Lin. “We can slow the progression, but we can’t make them better. All we can do is help them manage their symptoms.”
He is hoping his research will lead to treatments that can actually help the lung repair itself.
“If we can figure out how lung stem cells work, then maybe we can figure out how to get them to ramp up when we know they will be needed for repair,” Dr. Lin says. “We are a long way off, but I think it’s worth getting there.”
Joseph Lin, MD, is associate director of Stem Cell Biology at StemCells, Inc. in Palo Alto. He continues to treat patients at Stanford University Medical Center, where he completed his post-graduate training in Internal Medicine and Pulmonary and Critical Care Medicine.
