Distribution and significance of angiotensin-converting enzyme 2, a key receptor of 2019-nCoV, in ocular tissues

Abstract

Corona virus disease-19 (COVID-19) outbroke in the end of 2019 in Wuhan and is spreading worldwide, and its pathogeny is 2019 novel corona virus (2019-nCoV). 2019-nCoV mainly causes human respiratory infection and pulmonary inflammation, however, some COVID-19 patients are found to present viral conjunctivitis. Bilateral viral conjunctivitis is an initial symptom in some other cases. It is vital for us to know whether the eye can be directly infected by the virus and the consequence of the viral infection in ocular tissue. 2019-nCoV invades human cells primarily through binding to the angiotensin-converting enzyme 2 (ACE2) receptors. ACE2 expresses not only in lung, kidney, and cardiovascular system, but also in human cornea, conjunctiva, aqueous humor and retina. Therefore, it is crucial to expand our understanding of the infection mechanism and pathogenesis of COVID-19 comprehensively by clarifying the distribution of ACE2 in the eye. ACE2 is not only the receptor of 2019-nCoV, but also a key enzyme in renin-angiotensin system (RAS). RAS, which appears relatively independent in the eye, plays a modulate role in the eye and is associated with many common eye diseases. This article reviews the distribution and clinical significance of ACE2 in ocular tissues. Key words: Angiotensin-converting enzyme 2; Eye; Novel corona virus; Infection; Renin-angiotensin system