ABSTRACT
SARS-CoV-2, the pathogenic agent of COVID-19, employs angiotensin converting enzyme-2 (ACE2) as its cell entry receptor. Clinical data reveal that in severe COVID-19, SARS-CoV-2 infects the lung, leading to a frequently lethal triad of respiratory insufficiency, acute cardiovascular failure, and coagulopathy. Physiologically, ACE2 plays a role in the regulation of three systems that could potentially be involved in the pathogenesis of severe COVID-19: the kinin-kallikrein system, resulting in acute lung inflammatory edema; the renin-angiotensin system, promoting cardiovascular instability; and the coagulation system, leading to thromboembolism. Here we analyzed ~130,000 human lung single-cell transcriptomes and show that key elements of the kinin-kallikrein, renin-angiotensin and coagulation systems are co-expressed with ACE2 in alveolar cells, which could explain how changes in ACE2 promoted by SARS- CoV-2 cell entry result in the development of the three most severe clinical components of COVID-19.
