Expression of FoxJ1, a marker for ciliated cells, was almost absent in the epithelium on both normal and COPD scaffolds after 7 days of differentiation (supplementary Fig. S1A) but the percentage of FoxJ1 positive (+) cells increased markedly over time (Fig. 4A,B and supplementary Fig. S1A). This evidence concerns the gene FOXJ1 and chronic obstructive pulmonary disease.