Specific populations of cells inside the nose probably act as the portals for the invasion of the organism by Sars-CoV-2, the coronavirus that causes Covid-19. This conclusion comes from a molecular analysis of cells from different human tissues, recently published in the specialized magazine Nature Medicine (available for reading here, in English).
The method employed by the research, coordinated by Waradon Sungnak, from the Wellcome Sanger Institute in the United Kingdom, is quite ingenious. We already know that, to invade human cells, the new coronavirus is a protein on its surface, protein S ("spike" or spike) to connect to a "lock" on the cell membrane, the receptor known as ECA2.
Based on this information, they tracked different types of cells based on what is called the ECA2 gene expression – roughly speaking, how active the gene containing the recipe for producing this receptor is in the cells. That is, this is a measure of the amount of receptors of this type present in the cell membrane and, therefore, of how many "open doors" the virus would have for its invasion.
With the techniques used in the study, it was possible to do this cell by cell, and what was clear is that the cells inside the nose are the ones that most “express” (that is, produce) ECA2 and other related molecules, if compared practically compared with any other cell, including those in the throat. The champions in this regard are secretory cells (associated with mucus production) and hair cells.
The discovery may indicate, for example, that intranasal medications may be a good choice against Sars-CoV-2.