Two separate studies published in Nature journal on the same day this week reported the discovery of a key new type of lung cells. The cells, found in the human airway, may be responsible for cystic fibrosis, a painful genetic disorder affecting more than 70,000 people worldwide.
Extremely rare new cells
The disease still has no known cure despite years of study and progress in treatment options. The discovery of these new extremely rare lung cells- they make up only around 1% of airway cells- may offer revived hope for a potential cure.
According to both research teams, the cells, although sparse, show signs of being the primary source of activity of the CFTR gene mutations responsible for cystic fibrosis. CFTR, short for cystic fibrosis transmembrane conductance regulator, handles the protein that transports chloride ions across cell membranes.
Mutated CFTRs result in the buildup of thick mucus in the lung, pancreas and other organs that causes the respiratory infections and other health issues that plague cystic fibrosis patients. “As researchers work toward cures for cystic fibrosis, knowing you are looking at 1 percent of the cell population seems essential for any type of troubleshooting to improve a therapy or develop new therapies,” said Allon Klein, co-corresponding author of the first study and assistant professor of systems biology at Harvard Medical School (HMS).
The discovered cells have been named “pulmonary ionocytes” due to their intriguing similarities with the ionocytes cells found in the gills of freshwater fish. The studies also uncovered other kinds of rare cell types that may contribute to new effective therapeutic strategies.
A new cellular narrative of lung disease
“Cystic fibrosis is an amazingly well-studied disease, and we’re still discovering completely new biology that may alter the way we approach it,” said Jayaraj Rajagopal, co-corresponding author of the second study and HMS professor of medicine at Mass General. “We have the framework now for a new cellular narrative of lung disease.”
Despite the additional cell discoveries, the research, however, indicates the majority of CFTR expression takes place in pulmonary ionocytes. In addition, a correlation was found between the activity of CFTR and the number of pulmonary ionocytes in the tissue.
The discovery was made when Rajagopal's team experimented with disrupting a key molecular process in pulmonary ionocytes in mice. The interference resulted in a formation of dense mucus in the subjects.
The research may point to new treatments for the genetic disease such as increasing the number of pulmonary ionocytes to increase CFTR activity. In addition, the studies may be used to explore new methods for genetically correcting CFTR mutations.
Last but not least, the teams’ synchronized work revealed crucial information regarding the newly discovered cells' subtypes as well as the cells' changes in response to injury and during development. The team used an HMS-developed single-cell sequencing technology to track how the cells' states evolved in time after experiencing damage.