Abstract
The coronavirus pandemic raging worldwide since December 2019 is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which invades human cells via the angiotensin-converting enzyme 2 (ACE2) receptor. Although it has already been identified in many organs, ACE2 expression remains largely unknown in the head and neck (HN) sphere. Thus, this study aims to investigate its protein expression in several sites of the upper aerodigestive tract in order to highlight potential routes of infection. We compared ACE2 immunohistochemical expression between 70 paraffin-embedded specimens with two different antibodies and reported the quantified expression in each histological location. Surprisingly, we obtained different results depending on the antibody, an absence of labeling having been observed with a monoclonal antibody raised against the extracellular domain, whereas the polyclonal, against the cytoplasmic part of the protein, revealed enriched ACE2 expression, particularly in sinuses, vocal cords, salivary glands and oral cavity epithelial cells. The interpretation of these discordant results has brought several exciting lines of reflection. In conclusion, this study provides possible routes of entry for the SARS-CoV-2 in HN region and, above all, has led us to encourage caution when studying the ACE2 expression which is currently at the center of all attention.
Highlights
In December 2019, the cradle of an unprecedented new respiratory syndrome outbreak took its origin in Wuhan, China and was quickly attributed to a new β-coronavirus identified as SARS-CoV-2 by the International Committee on Taxonomy of Viruses, giving rise to what is more commonly known as coronavirus disease 2019 (COVID-19) [1,2]
To better understand the pathogenesis and the potential routes of infection in head and neck regions, we explored the immunolocalization of angiotensin-converting enzyme 2 (ACE2) protein in seven different tissue types and identified cell types expressing ACE2
To confirm and provide further information at the protein level, we performed immunohistochemistry with two antibodies, a polyclonal and a monoclonal, raised against, respectively, the intracellular and extracellular part of the protein, to visualize ACE2 protein localization in different anatomical sites of the upper aerodigestive tract. This approach provides additional spatial information, which is important for understanding the possible ACE2 cellular interaction sites for COVID-19
Summary
In December 2019, the cradle of an unprecedented new respiratory syndrome outbreak took its origin in Wuhan, China and was quickly attributed to a new β-coronavirus identified as SARS-CoV-2 by the International Committee on Taxonomy of Viruses, giving rise to what is more commonly known as coronavirus disease 2019 (COVID-19) [1,2]. To date, this highly contagious disease has infected. Since the results recently published by many teams, there is no longer any doubt that
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