In particular, the lung tissues of COPD patients display stronger expression levels of BMP and activin membrane-bound inhibitor (BAMBI)26, which is a 260-amino acid transmembrane protein that acts as a competitive receptor antagonist for TGF-β type-I receptors (TGF-β RI) and the subsequent Smad signaling pathways27, 28. This evidence concerns the gene BAMBI and chronic obstructive pulmonary disease.