Dr. Gloria De Carlo Massaro and Dr. Donald Massaro of the Georgetown University School of Medicine showed that in rats given elastase to produce emphysema-like changes in their lungs, treatment with retinoic acid returned the lung alveoli to normal size and number. The alveoli are the small air spaces in the lungs where the exchange of oxygen and carbon dioxide between the lungs and the bloodstream takes place.
Elastase is a protein that breaks down the elastin that helps maintain the alveolar walls.
The Massaro study appears in the June issue of Nature Medicine.
"This is the first time that anyone has identified a means of reversing emphysema," said NHLBI Director Dr. Claude Lenfant. "It represents the first step in improving our understanding of the role of retinoic acid and similar agents in forming alveoli. It could lead to the development of an agent for treating lung diseases like emphysema and bronchopulmonary dysplasia in which the patient has insufficient alveoli to breathe efficiently.
"Nonetheless," he added, "a great deal more basic research is needed before we can even begin to think about applying this to humans. Until then, we caution that there is absolutely no evidence that Vitamin A supplementation is useful in treating lung disorders."
Emphysema is a lung disease that currently affects approximately 2 million Americans, most of them longtime smokers over the age of 45. It accounts for approximately 17,000 deaths in the U.S. each year and more than $2.5 billion in annual health care costs.
In early 1996, the Massaros showed that treating normal newborn rats with retinoic acid increased the number of alveoli in their lungs. In the new study, the Massaros tested whether retinoic acid could produce the same results in adult rats with emphysema.
The Massaros first instilled elastase into the lungs of laboratory rats and confirmed that it causes changes in the alveoli characteristic of human emphysema.
They then treated rats, which had received elastase, with retinoic acid and showed that these rats grew new alveoli and developed lung structure essentially the same as that of control rats that had not received either elastase or retinoic acid.
In emphysema, the alveoli are gradually destroyed. Destruction of the alveoli leads to shortness of breath, disability, and eventually death. Currently, the only treatment for emphysema is a lung transplant.
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For more information, contact Dr. Gloria Massaro through the Georgetown University Press Office, 202-687-5100, or the NHLBI Communications Office, 301-496-4236.
