Transforming growth factor-1 (TGF-β1) reportedly activated Smad3, which triggered CFTR downregulation via augmenting miR-145 expression.17–20 More importantly, microarray data showed that miR-145 was one of the five highly expressed miRNAs and small nucleolar RNA in patients with severe COVID-19.21 Given that numerous Smad-interacting proteins have been implicated in Smad signaling,22 we postulated that N protein might interact with Smad3 to induce the downregulation of CFTR via miR-145. This evidence concerns the gene SMAD3 and COVID-19.