A new type of cell has been discovered in the human airway, and it may have a central role in cystic fibrosis. There are currently 70,000 people across the world living with cystic fibrosis for which there is currently no cure, and the disease is a major cause of poor health and a shortened life span.
What is cystic fibrosis?
A genetic disorder that mostly affects the lungs, but can also affect other organs including the pancreas, liver and kidneys. The gene affected by cystic fibrosis controls the movement of salt and water in and out of cells in the body, so sufferers experience a build-up of thick mucus in the lungs and other organs. You can only be born with cystic fibrosis as it is caused by a faulty gene from the parents, around 1 in 25 of us is a carrier of this gene. At present there is no known cure for cystic fibrosis, and the lung infections caused by the illness are only treated with antibiotics.
The gene responsible is known as Cystic Fibrosis Transmembrane Conductance Regulator, or CFTR, and it is the mutation of this gene that causes cystic fibrosis. CFTR handles the protein that transports chloride ions across cell membrane and plays a key role in managing hydration and pH balance, two main problems for cystic fibrosis patients. Scientists already know that mucus proteins do not form properly in cystic fibrosis patients which causes salt-water imbalances and dehydration. The mutated CFTRs result in a build-up of thick mucus in the lungs, pancreas, and other organs that cause breathing problems, infections, and other health issues that plague sufferers of cystic fibrosis.
The researchers, from the Broad Institute of Harvard and MIT and Massachusetts General Hospital, initially carried out a study in healthy and CFTR mutated mice. They analysed thousands of lung cells in the mice and mapped the location of these cells to create an ‘atlas’. When they sorted these cells, they found that there were seven types, not the six that had previously been counted. The cellular-tagging techniques and computer algorithms used have only been technologically feasible in the last few years, which may explain why the new cell has been missed in previous research.
What is most exciting about this new cell is that it shows signs of being the primary source of activity for the CFTR gene. The gene can be expressed by many lung cells, but it is mainly expressed by pulmonary ionocytes, and the newly discovered cell was found to contain an abundance of these. Once the researchers had discovered this new cell in mice, they then confirmed the presence of pulmonary ionoytes in healthy human lungs. The researchers hope that their discovery could lead to the development of more targeted therapy for cystic fibrosis as knowing that pulmonary ionocytes is the main source of CFTR gene expression could help scientists create therapies that can be delivered by these specific cells.
At the moment, scientists have only identified that human lungs have pulmonary ionocytes, and they have not yet looked for the cells in cystic fibrosis patients, or in the other organs that the disease can affect. The findings also need to be explored by other researchers specialising in cystic fibrosis, so the new discovery will not rapidly change current therapy. There are some treatments already in use with cystic fibrosis patients, which help improve the function of the mutated gene associated with CFTR production so that mucus will be thinner and less viscous. Hopefully this new development will contribute immensely to the ongoing gene therapy and stem cell research that might one day cure the disease.