S100A4 and cystic fibrosis: Additionally, some markers, such as discoidin domain-containing receptor 2 (DDR2), fibroblast-specific protein 1 (FSP1), stem-cell antigen 1 (Sca1), and vimentin, were initially used to identify CFs; however, these were not unique markers of fibroblasts and were also not expressed by the whole CF population [6,7,8,9].