Understanding olfactory dysfunction in COVID-19: Expression of ACE2, TMPRSS2 and Furin in the nose and olfactory bulb in human and mice
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Abstract
Background
Anosmia is a frequent symptom in coronavirus disease 2019 (COVID-19) patients that generally resolves within weeks. In contrast, the anosmia caused by other upper respiratory infections affects a small proportion of patients and may take months to resolve or never resolve. The mechanisms behind COVID-19-induced olfactory dysfunction remain unknown. Here, we address the unique pathophysiology of COVID-19-associated olfactory dysfunction.
Methods
The expression of ACE2 (virus binding receptor) and TMPRSS2 and Furin (host cell proteases facilitating virus entry) was examined in the nasal mucosa, composed of respiratory mucosa (RM), olfactory mucosa (OM), and olfactory bulb (OB) of mouse and human tissues using immunohistochemistry and gene analyses.
Results
Co-expression of ACE2, TMPRSS2, and Furin was observed in the RM and in the OM, especially in the supporting cells of the olfactory epithelium and the Bowman’s glands. Notably, the olfactory receptor neurons (ORNs) in the OM were positive for ACE2 but almost negative for TMPRSS2 and Furin. Cells in the OB expressed ACE2 strongly and Furin weakly, and did not express TMPRSS2. All three gene expressions were confirmed in the nasal mucosa and OB.
Conclusions
ACE2 was widely expressed in all tissues, whereas TMPRSS2 and Furin were expressed only in certain types of cells and were absent in the ORNs. These findings, together with clinical reports, suggest that COVID-19-related anosmia occurs mainly through sensorineural and central dysfunction and, to some extent, conductive olfactory dysfunction. The expression of ACE2, but not TMPRSS2 or Furin, in ORNs may explain the early recovery from anosmia.
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SciScore for 10.1101/2020.05.15.097352: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Institutional Review Board Statement All experiments were conducted in accordance with institutional guidelines and with the approval of the Animal Care and Use Committee of the University of Tokyo (No. P14-051, P15-115) and of the Research Ethics Committee of the Graduate School of Medicine and Faculty of Medicine, the University of Tokyo, Japan (12009, 2019073NI). Randomization not detected. Blinding not detected. Power Analysis not detected. Sex as a biological variable The samples from 6 eight-week-old male C57BL/6 mice (23) and an eight-week-old- male Sprague Dawley rat (28) were used, and the following paraffin- embedded tissues were collected; the RM area and OM area of the nose, the OB … SciScore for 10.1101/2020.05.15.097352: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Institutional Review Board Statement All experiments were conducted in accordance with institutional guidelines and with the approval of the Animal Care and Use Committee of the University of Tokyo (No. P14-051, P15-115) and of the Research Ethics Committee of the Graduate School of Medicine and Faculty of Medicine, the University of Tokyo, Japan (12009, 2019073NI). Randomization not detected. Blinding not detected. Power Analysis not detected. Sex as a biological variable The samples from 6 eight-week-old male C57BL/6 mice (23) and an eight-week-old- male Sprague Dawley rat (28) were used, and the following paraffin- embedded tissues were collected; the RM area and OM area of the nose, the OB area, and the kidney and prostate for positive controls of immunostaining (Figure 1A). Table 2: Resources
Antibodies Sentences Resources After antigen activation, primary antibodies against ACE2 (1:300 dilution; rabbit monoclonal, Abcam, ab108252; Cambridge, UK), TMPRSS2 (1:1000 dilution; rabbit monoclonal, Abcam, ab92323; Cambridge, UK), Furin (1:100 dilution; rabbit monoclonal, Abcam, ab183495; Cambridge, UK) , and PGP9.5 for a neuronal marker (1:500 dilution; guinea pig polyclonal, Abcam, ab10410; Cambridge, UK) were detected with peroxidase conjugated appropriate secondary antibodies and a diaminobenzidine substrate. ACE2suggested: (Abcam Cat# ab108252, AB_10864415)<div style="margin-bottom:8px"> <div><b>TMPRSS2</b></div> <div>suggested: (Abcam Cat# ab92323, <a href="https://scicrunch.org/resources/Any/search?q=AB_10585592">AB_10585592</a>)</div> </div> <div style="margin-bottom:8px"> <div><b>Furin</b></div> <div>suggested: (Abcam Cat# ab66679, <a href="https://scicrunch.org/resources/Any/search?q=AB_2105083">AB_2105083</a>)</div> </div> </td></tr><tr><td style="min-width:100px;vertical-align:top;border-bottom:1px solid lightgray">In human nasal mucosa, the PGP9.5 antibody clearly visualized the OE containing olfactory neurons.</td><td style="min-width:100px;border-bottom:1px solid lightgray"> <div style="margin-bottom:8px"> <div><b>PGP9.5</b></div> <div>suggested: None</div> </div> </td></tr><tr><td style="min-width:100px;text-align:center; padding-top:4px;" colspan="2"><b>Software and Algorithms</b></td></tr><tr><td style="min-width:100px;text=align:center"><i>Sentences</i></td><td style="min-width:100px;text-align:center"><i>Resources</i></td></tr><tr><td style="min-width:100px;vertical-align:top;border-bottom:1px solid lightgray">Gene expression analyses Our previous DNA microarray data from the nasal mucosa and OB (NCBI Gene Expression Omnibus database under the series number GSE 103191, 150694) was used to examine the expressions of ACE2, TMPRSS2, and Furin.</td><td style="min-width:100px;border-bottom:1px solid lightgray"> <div style="margin-bottom:8px"> <div><b>Gene Expression Omnibus</b></div> <div>suggested: (Gene Expression Omnibus (GEO), <a href="https://scicrunch.org/resources/Any/search?q=SCR_005012">SCR_005012</a>)</div> </div> </td></tr></table>Results from Barzooka: We found bar graphs of continuous data. We recommend replacing bar graphs with more informative graphics, as many different datasets can lead to the same bar graph. The actual data may suggest different conclusions from the summary statistics. For more information, please see Weissgerber et al (2015).
Results from OddPub: We did not find a statement about open data. We also did not find a statement about open code. Researchers are encouraged to share open data when possible (see Nature blog).
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