Angiotensin-converting enzyme 2, a SARS-CoV-2 receptor, is upregulated by interleukin-6 via STAT3 signaling in rheumatoid synovium

Detected in December 2019, the coronavirus disease 2019 (COVID-19) has since spread all over the world, resulting in a global pandemic. The disease is caused by severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2), and its symptoms usually include cough, fever, and gastrointestinal problems. Although the prevalence of rheumatoid arthritis (RA) is about 1 % of the global population and RA patients naturally have a chance of acquiring COVID-19 in this pandemic, no studies have considered the expression of angiotensin-converting enzyme 2 (ACE2) (a receptor for SARS-CoV-2) in synovial tissues. Our presenting data revealed that ACE2 expression was elevated in active rheumatoid synovium, and siRNA against STAT3 was able to downregulate ACE2 expression, which was in turn induced by IL-6 signaling.