ACE2 and infection: Expression of ACE2 in endothelial cells (52) and lung alveolar cells is relatively low (SI Appendix, Figs. S1 and S2), but VIM as an attachment factor produced by mesenchymal cells (e.g., endothelial and fibroblasts) (53), could enhance the SARS-CoV-2 entry in respiratory cells via both cis- and trans-infection (44).