In particular, soluble frizzled-related protein-1, encoded by SFRP1, was demonstrated in the adult lung, leading to the destruction of lung tissue [40], and functioned as antagonizing the Wnt signaling which has a great impact in lung development and the progression of lung diseases including COPD, IPF and emphysema [41,42]. This evidence concerns the gene SFRP1 and pulmonary emphysema.