PECAM1 and COVID-19: To validate the observed reduction of T-cadherin expression in the lungs during COVID-19, we conducted double immunohistochemical (IHC) and double immunofluorescent staining on lung tissues using antibodies against T-cadherin and CD31 (vessels), E-cadherin (bronchioles), and the stromal marker α-SMA (Supplementary Figure S1 for double IHC; Supplementary Figure S2 for double immunofluorescent staining).