It has been reported that angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2) are the main cell entry proteins for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and play a critical role in causing coronavirus disease 2019 (COVID-19). To investigate the expression level of these SARS-CoV-2 host cell entry genes in the lung airway, we used public gene expression datasets. We have found a differential expression of ACE2 and TMPRSS2 in nasal and bronchial airways relative to age and diseases status. Children were found to have significantly lower expression of COVID-19 receptors in the upper and lower airways (nasal and bronchial). Moreover, the lung airway expression of both ACE2 and TMPRSS2 was found to be significantly upregulated in smokers compared with non-smokers, and in patients with chronic obstructive pulmonary disease (COPD) compared with healthy subjects. No difference was observed in the blood expression levels of ACE2 and TMPRSS2 between children and adults, or in COPD or diabetic patients. However, a significant increase in blood expression levels of these genes was observed in patients with essential hypertension, whereas only ACE2 was upregulated in the blood of asthmatics. These results suggest that the observed difference in COVID-19 severity between children and adults could, in part, be attributed to the difference in ACE2 and TMPRSS2 airways tissue expression levels.

据报道，血管紧张素转换酶2（ACE2）和跨膜丝氨酸蛋白酶2（TMPRSS2）是严重急性呼吸综合征冠状病毒2（SARS-CoV-2）的主要细胞进入蛋白，在引起冠状病毒疾病中起关键作用2019（COVID-19）。为了研究这些SARS-CoV-2宿主细胞进入基因在肺气道中的表达水平，我们使用了公共基因表达数据集。我们已经发现，相对于年龄和疾病状况，ACE2和TMPRSS2在鼻和支气管气道中的差异表达。发现儿童在上呼吸道和下呼吸道（鼻和支气管）中的COVID-19受体表达明显降低。此外，与不吸烟者相比，吸烟者中ACE2和TMPRSS2的肺气道表达均显着上调，并将慢性阻塞性肺疾病（COPD）患者与健康受试者进行比较。在儿童和成人之间或COPD或糖尿病患者中，ACE2和TMPRSS2的血液表达水平没有差异。然而，在原发性高血压患者中观察到这些基因的血液表达水平显着增加，而哮喘患者的血液中只有ACE2上调。这些结果表明，儿童和成人之间观察到的COVID-19严重程度差异可能部分归因于ACE2和TMPRSS2气道组织表达水平的差异。在原发性高血压患者中观察到这些基因的血液表达水平显着增加，而哮喘患者的血液中只有ACE2上调。这些结果表明，儿童和成人之间观察到的COVID-19严重程度差异可能部分归因于ACE2和TMPRSS2气道组织表达水平的差异。在原发性高血压患者中观察到这些基因的血液表达水平显着增加，而哮喘患者的血液中只有ACE2上调。这些结果表明，儿童和成人之间观察到的COVID-19严重性差异可能部分归因于ACE2和TMPRSS2气道组织表达水平的差异。