Epithelial mesenchymal transition (EMT) in patients with chronic obstructive disease (COPD)

Background We published data showing that the reticular basement membrane (Rbm) in smokers and especially COPD is highly fragmented with “clefts” containing cells staining for the proteolytic enzyme matrix-metalloproteinase-9 (MMP-9) and fibroblast protein, S100A41. These cells are also present in the basal epithelium (BE). Such changes are the phenotypic markers of EMT. The aim of this study was to confirm EMT, the epithelial origin of these Rbm cells and importantly, to exclude potential confounding by infiltrating inflammatory cells. Methods Slides chosen from endobronchial biopsies from 10 COPD current smokers which showed typical examples of Rbm splitting / cellularity were stained for neutrophil elastase (neutrophil marker), CD68 (macrophage and mature fibroblast marker), CD4+/CD8+ T lymphocytes, CD19 (B-cell marker) and CD11c (dendritic cells), S100 (Langerhans cells); and cytokeratin(s) (epithelial marker). The number of cells in the Rbm and epithelium staining for these “inflammatory” cell markers were compared to the numbers of cells staining for the S100A4, as a representative marker of EMT. Results In the BE there were significantly more cells stained for S100A4 than the sum of infiltrating macrophages, fibroblasts or immune cells: median, (range), 26 (21.3 – 37.3) versus 0 (0 – 9.6) per mm, p<0.003. Markedly more S100A4 staining cells were also observed in the Rbm compared to the sum of infiltrating macrophages, neutrophils, fibroblasts or immune cells or any sub-type: median, (range), 58 (37.3 – 92.6) versus 0 (0 – 4.8) cells/mm Rbm, p<0.003. We confirmed double staining for both cytokeratin and S100A4 in cells both in the BE and Rbm. Conclusions These data confirm EMT in COPD patients in vivo.