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. 2021 Sep 28;2(10):100421. doi: 10.1016/j.xcrm.2021.100421

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© 2021.

This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

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Comparative analysis of ACE2 and TMPRSS2 protein expression in normal human head and neck tissues

(A) Representative immunofluorescence staining of ACE2, the epithelial marker pan-cytokeratin (panKRT), and the cilium marker ACTUB on normal human nasal cavity tissue (top row) and bronchus tissue (bottom row). Note co-localization of ACE2 and panKRT/ACTUB staining in the epithelia/cilia, respectively. Nuclei were stained using Hoechst (blue) as a counterstain.

(B) Quantification of ACE2 in the epithelia of normal human mucosal tissues of the head and neck. ACE2 protein expression was statistically significantly higher in the trachea/bronchus (0.93 ± 0.07, n = 21) compared with the nasopharynx (0.82 ± 0.03, n = 7), oro/hypopharynx (0.83 ± 0.07, n = 14), and conjunctiva (0.78 ± 0.04, n = 4). (Kruskal-Wallis test p < 0.0001; Dunn’s multiple comparison post hoc test, †adjusted p = 0.0130, ††adjusted p = 0.0015, and ††adjusted p = 0.0025, respectively).

(C) Quantification of ACE2 within the cilia of normal human mucosal tissues of the head and neck. No significant differences in ACE2 expression were detected between cilia of the nose (n = 11), nasopharynx (n = 7), and trachea/bronchus (n = 21). (Kruskal-Wallis test, p = 0.0624). The larynx tissue used in Figure 3B did not contain cilia.

(D) Representative immunofluorescence staining of TMPRSS2, panKRT, and ACTUB in normal human nasal (top row) and bronchial tissues (bottom row). Nuclei were stained using Hoechst (blue) as a counterstain. Similar to ACE2, note co-localization of TMPRSS2 and panKRT/ACTUB staining in the epithelia/cilia, respectively.

(E) Quantification of TMPRSS2 in the epithelia of normal human mucosal tissues. TMPRSS2 protein expression was statistically significantly higher in the nose (1.05 ± 0.07, n = 11) compared with the tongue (0.85 ± 0.08, n = 16), oro/hypopharynx (0.80 ± 0.10, n = 13), esophagus (0.70 ± 0.06, n = 5), and conjunctiva (0.82 ± 0.04, n = 4) (Dunn’s multiple comparison post hoc test, ∗∗∗adjusted p = 0.0007, ∗∗∗∗adjusted p < 0.0001, ∗∗∗∗adjusted p < 0.0001, and ∗adjusted p = 0.0167, respectively). TMPRSS2 in the trachea/bronchus (0.98 ± 0.08, n = 21) was statistically significantly higher compared with the tongue, oro/hypopharynx, and esophagus (Kruskal-Wallis test p < 0.0001; Dunn’s multiple comparison post hoc test, †adjusted p = 0.0149, †††adjusted p = 0.0006, and †††adjusted p = 0.0004, respectively).

(F) Quantification of TMPRSS2 in the cilia of normal human mucosal tissues. TMPRSS2 protein expression was statistically significantly higher in nasal tissues (1.39 ± 0.30, n = 11) compared with the nasopharynx (1.02 ± 0.15, n = 7) and bronchus/trachea (1.09 ± 0.08, n = 20) (Kruskal-Wallis test p = 0.0008; Dunn’s multiple comparison post hoc test, ∗∗adjusted p = 0.0048 and ∗∗adjusted p = 0.0020, respectively).

Values in parentheses are presented as mean ± SD. The bands within the boxplot show the median value. The bottom and top of the boxplots represent the 25th and 75th percentiles, respectively. The whiskers extending from both ends of the boxes are minimum and maximum values. Each dot represents one individual. Scale bars, 50 μm and 20 μm (insets). See also Figures S2 and S3.