Coronavirus and stem cells
Russian biologists have discovered an ominous property of the coronavirus
Anatoly Glossev, Vesti
Russian scientists have found out that the SARS-CoV-2 coronavirus is capable of affecting stem cells. This makes the pathogen especially dangerous and distinguishes it from its "brethren", which cause only mild acute respiratory infections.
The details are described in a scientific article published in the prestigious journal Scientific Reports (Valyaeva et al., Expression of SARS-CoV-2 entry factors in lung epithelial stem cells and its potential implications for COVID-19).
SARS-CoV-2 is far from the only coronavirus capable of infecting humans. As reported in the press release of Lomonosov Moscow State University, about 15% of all cases of SARS are caused by certain coronaviruses. What is the difference between a pathogen that has killed more than a million people worldwide in less than a year?
"It is interesting and at the same time important to understand what distinguishes those coronaviruses that cause not mild colds, but severe illnesses," notes the head of the research group Evgeny Cheval from Moscow State University. "This may also have practical significance, not only in relation to the current pandemic, but also to those infections that may appear in the future".
To understand the causes of the malignity of SARS-CoV-2, it is important to identify all types of cells into which the pathogen can penetrate. However, this is a very large-scale task, because there are many very diverse cells in the human body.
The authors of the new article asked a more specific question: can the virus penetrate into the stem cells of the respiratory organs?
Let us explain that the trachea, bronchi and alveoli of the lungs are lined with a special tissue: epithelium. The epithelium is constantly being updated: old and damaged cells die off, and new ones take their place. For the "production" of these new cells in the respiratory organs, there are special populations of stem cells. Recall that stem cells are able to transform into cells of different types, including epithelial cells.
If the epithelium of the respiratory organs is damaged more than usual (for example, with pneumonia), "regular" stem cells cannot cope with its renewal. Then the body introduces an "emergency team" – special populations of stem cells that do not participate in the daily renewal of tissue, but can restore it with severe damage.
Stem cells provide renewal of the epithelium of the respiratory organs normally and after various injuries. But the SARS-CoV-2 coronavirus can infect stem cells, interfering with the restoration of the epithelium. Illustration by Evgeny Cheval/MSU.
It is known that the SARS-CoV-2 coronavirus is able to infect the epithelial cells of the respiratory tract and lungs (which leads to pneumonia). But does it also infect stem cells designed to repair damage? If so, then the pathogen inflicts a double blow on the body: it not only damages the epithelium, but also prevents it from being "repaired".
How to find out if stem cells are vulnerable to coronavirus? The easiest way is to check whether these cells produce proteins that the pathogen uses to enter the cell. This is exactly what the authors of the new article did.
Scientists analyzed the information accumulated in databases by different scientific groups. They were interested in whether the proteins ACE2, TMPRSS2 and FURIN are produced in stem cells. All these proteins are necessary for the virus to enter the cell.
Biologists have received alarming results. Stem cells, the body's natural regenerative reserve, are really vulnerable to a new infection.
"Stem cells in some cases may be even more sensitive to viral infection than the differentiated (i.e. non–stem - ed.) cells surrounding them. Infection of stem cells can lead to disorders of epithelial regeneration, which, as we suggest, may be one of the reasons for the high pathogenicity of SARS-CoV-2," summarizes the first author of the article Anna Valyaeva from Moscow State University.
We emphasize that the authors did not conduct experiments on the infection of human stem cells with coronavirus. Such experiments are a matter of the future. They will show whether SARS-CoV-2 is really capable of infecting cells of this important type for the body.
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