At present, scientists have found a new type of human cells hidden in the fragile branch channels of the lungs, and confirmed that these newly discovered cells play an important role in maintaining the normal operation of the respiratory system, and may even inspire new treatments to reverse the effects of some smoking related diseases. These new types of cells are named "respiratory secretory cells (RAS)", which exist in the bronchioles. There are alveoli at the top of the bronchioles. The tiny alveoli are airbags for blood to exchange oxygen and carbon dioxide.
At the same time, RAS cells are similar to stem cells - "blank canvas cells". They can differentiate into any other type of cells in the body, repair damaged alveolar cells and transform them into new cells.
In previous experiments using mouse lungs as an alternative model of human respiratory system, researchers found that RAS cells showed reduced functionality due to the limitations of the experimental model. However, due to some gaps between the two, scientists have been trying to fill some knowledge gaps about human lungs. In order to better understand these differences at the cellular level, researchers extracted lung tissue samples from healthy human donors, The genes in a single cell were analyzed, and the previously unknown Ras cells were found.
On the left is a "slowly deforming" Ras cell; The picture on the right shows the transformation of Ras cells into at2 cells in the culture dish.
Professor Edward morrisey, a respiratory expert at the Perelman School of medicine at the University of Pennsylvania and the author of the study, said: "it has long been known that the airway of human lungs is different from that of mice. Due to the long-term use of mice as experimental objects in the laboratory, there are deviations and misunderstandings in research and analysis. It is not until recent emerging technologies that we can sample and identify unique cell types."
Morisi pointed out that at the same time, the research team also found Ras cells in ferrets. Ferrets' respiratory system is closer to human than that of mice. Therefore, the researchers suspect that RAS cells may exist in the lungs of most mammals close to or larger.
Ras cells have two main functions in the lung: one is that they secrete molecular particles to maintain the fluid in the bronchioles, help prevent small airway collapse and maximize lung efficiency; Second, it can be used as the progenitor of alveolar type 2 (AT2) cells. Progenitor cells are cells that have the ability to differentiate into another type of cells, similar to the way stem cells differentiate into other cells.
"Ras cells are what we call facultative progenitor cells, which means that they are both progenitor cells and play an important role in maintaining airway health. At the same time, RAS cells also play a vital role in maintaining lung health," Morris said
The researchers believe that RAS cells may play a key role in smoking related diseases, such as chronic obstructive pulmonary disease (COPD). According to the Mayo Clinic, chronic obstructive pulmonary disease is caused by pulmonary airway inflammation, which is closely related to smoking and occasionally caused by air pollution. Respiratory inflammation will make it difficult for the lungs to absorb enough oxygen properly. Therefore, the symptoms of chronic obstructive pulmonary disease are similar to asthma. It may also lead to emphysema, permanent destruction of alveoli and chronic bronchitis. It is reported that chronic bronchitis is a long-term strong cough symptom, usually accompanied by more sputum. According to the statistics of the World Health Organization, more than 3 million people die of chronic obstructive pulmonary disease (COPD) every year.
Theoretically, RAS cells should prevent or at least mitigate the effects of COPD by repairing damaged alveoli. However, researchers speculate that smoking can damage or even completely destroy Ras cells, leading to the onset of diseases such as COPD.
Patients with COPD usually take anti-inflammatory drugs or oxygen therapy to alleviate symptoms. However, this is only a temporary solution and has no effect on reversing lung injury. If researchers can make normal use of the regenerative properties of Ras cells, RAS cells may be used to improve treatment and even cure chronic obstructive pulmonary disease.
"We really don't know whether this finding will help promote the potential treatment of COPD. However, since COPD is a disease we know less about, any new research perspective will help develop new treatments to achieve better treatment results," morisi said At present, the latest research report is published in the journal Nature on March 30.