Fig. 4.

Quantitative analysis showed that the expression levels of ACE2 and TMPRSS2 in oral mucosa tissues were different by age or gender. A, B Real-time quantitative polymerase chain reaction (qRT-PCR) analysis showed the relative mRNA levels of ACE2 and TMPRSS2 in oral mucosal tissues of the relatively younger and relatively elderly females. C, D qRT-PCR analysis showed the relative mRNA levels of ACE2 and TMPRSS2 in oral mucosal tissues of the relatively younger and relatively elderly males. E, F qRT-PCR analysis showed the relative mRNA levels of ACE2 and TMPRSS2 in oral mucosal tissues of females and males with similar age. (G-H) Western blot analysis showed the protein levels of ACE2 in people of different ages and genders. I–J Western blot analysis showed the protein levels of TMPRSS2 in people of different ages and genders. K–N showed the statistical analysis of G–J A–N, n ≥ 3. Data were analyzed using two-tailed Student’s t test and presented as the mean ± SD. P values were provided in case of multiple samples, and P values < 0.05 indicated statistical significance