New lung cell type discovered.

Cystic fibrosis is a genetic-based disorder which primarily affects the lungs.  The gene affected by cystic fibrosis is CFTR (cystic fibrosis transmembrane conductance regulator), which controls the movement of salt and water in and out of cells. People with cystic fibrosis experience a build-up of thick sticky mucus in the lungs, digestive system and other organs, affecting the entire body.  Treatments are available to help reduce the problems caused by the condition, however, life expectancy is shortened. Now, a study led by researchers at Harvard Medical School identifies a new, rare type of cell in the human airway, which appear to be the primary source of activity of the CFTR gene, mutations to which cause cystic fibrosis, a multi-organ disease that affects more than 70,000 people worldwide.  The  team named the cells ‘pulmonary ionocytes’ and suggest that the majority of CFTR expression occurs in these cells, which make up only around 1% of airway cells.  The study is published in the journal Nature.

Previous studies show that CFTR is a protein which regulates the balance between salt and water on epithelial surfaces, such as in the lung or pancreas. Mutations to CFTR can lead to the buildup of thick mucus in the lung, pancreas and other organs, which in turn leads to cystic fibrosis.  Despite decades of study on CFTR and progress in treating cystic fibrosis, there is still no cure.  The current study shows that CFTR activity is concentrated in a small, previously unknown population of cells, which serve as promising targets for cystic fibrosis.

The current study utilises single-cell sequencing technology to analyze gene expression in tens of thousands of individual cells isolated from human and mouse airways–one cell at a time.  Comparing patterns of gene expression and using previously described cells as references, the team created comprehensive catalogues of different cell types and states, as well as their abundance and distribution.  Results show that pulmonary ionocytes expressed higher levels of CFTR than any other cell.

Data findings suggest that the majority of CFTR expression occurs in pulmonary ionocytes. Results show that the activity of CFTR, not just its expression, relates to the number of pulmonary ionocytes in the tissue.  When the lab disrupted a critical molecular process in pulmonary ionocytes in mice, they observed the onset of key features associated with cystic fibrosis, notably the formation of dense mucus. The group conclude this finding underscores how important these cells are to airway-surface regulation.

The team surmise that they have identified a rare cell type, the pulmonary ionocyte which they have shown to be a primary source of activity of the CFTR gene, mutations in which cause cystic fibrosis.  For the future, the researchers state their findings point to new strategies for treating cystic fibrosis, such as increasing the amount of pulmonary ionocytes to increase the amount of CFTR activity.

Source: Harvard Medical School


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