Respiratory airway secretory cells, or RASCs, are a new type of cell that resides deep within human lungs and may play a key role in human lung diseases. A group of researchers reported their findings in a recent issue of the journal Nature, analysing human lung tissue to identify the new cells.
The cells line tiny airway branches, deep in the lungs, near the alveoli structures where oxygen is exchanged for carbon dioxide. The scientists showed that RASCs have stem-cell-like properties enabling them to regenerate other cells that are essential for the normal functioning of alveoli. They also found evidence that cigarette smoking and the common smoking-related ailment called chronic obstructive pulmonary disease (COPD) can disrupt the regenerative functions of RASCs. Thus, correcting this disruption could be an effective way to treat COPD.
COPD involves progressive damage to and loss of alveoli, exacerbated by chronic inflammation. It is estimated to cause about 3 million deaths every year around the world. Patients often are prescribed steroid anti-inflammatory drugs and/or oxygen therapy, but these treatments can only slow the disease process rather than stop or reverse it.
RASCs, which don't exist in mouse lungs, are "secretory" cells that reside near alveoli and produce proteins needed for the fluid lining of the airway.
Observations of gene-activity similarities between RASCs and an important progenitor cell in alveoli called AT2 cells led the researchers to another discovery: RASCs, in addition to their secretory function, serve as predecessors for AT2 cells -- regenerating them to maintain the AT2 population and keep alveoli healthy. AT2 cells are known to become abnormal in COPD and other lung diseases, and the researchers found evidence that defects in RASCs might be an upstream cause of those abnormalities.
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