Factors Associated With The Expression Of Ace2 In Human Lung Tissue: Pathological Evidence From Patients With Normal Fev1 And Fev1/Fvc

Background: Whether COVID-19 comorbidities and risk factors such as old age, male gender, smoking, obesity, eosinophils and blood types have direct contact with expression of ACE2 and pro-inflammation cytokines in human lung tissues were still unclear.Patients and Methods: Sixty-four patients with normal FEV1 and FEV1/FVC underwent thoracotomy for pulmonary nodules were included. Blinded histological assessments were performed by two pathologists. Clinical features and results of the immunohistochemical staining of ACE2 were collected and analyzed.Results: ACE2 expressed in alveolar macrophages (most obvious), alveolar epithelia and vascular endothelia, but not in small-airway epithelia. ACE2 expressions are positively related to age (r = 0.26, P = 0.040), weight (r = 0.43, P<0.001), as well as BMI (r = 0.38, P = 0.002), and male patients show higher expressions of ACE2 in lungs (P <0.05). ACE2 expressions are negatively related to peripheral eosinophils (r = -0.30, P = 0.017). There was no correlation between ABO blood types and ACE2 expression in normal lung tissues (P > 0.05). IL-13 and IL-6R expression in lung tissue increased with age (r = 0.26, P <0.05, for both).Conclusion: Our pathological evidences showed that the alveolar epithelia, vascular endothelia, and alveolar macrophages are susceptible in human lungs for SARS-CoV-2 infection. The risk factors such as high body weight/BMI, old age, male gender, and eosinopenia may be related to ACE2 expression in human lungs, and associated with more chance to develop the severe cases. IL-6R expression in lung tissue also increased with age. Therefore, weight control and smoking cessation are essential to reduce the susceptibility of SARS-CoV-2 infection, especially in obesity, old or male patients. Peripheral eosinophils monitor is also quite necessary to detect severe tendency in COVID-19 patients.