GAG compounds, including the heparin (H), heparan sulfate (HS), dextran sulfate (DS) and chondroitin sulfate (CS), were obtained from Sigma-Aldrich. The MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay kit was obtained from Sigma-Aldrich. FITC-conjugated BSI-B4 isolectin (Sigma-Aldrich) was used as a marker for basal cells from the tracheal epithelium [12] . Commercial culture media for human and rat airway epithelial cells were obtained from CELLnTEC advanced cell system (Postfach, Bern, Switzerland) and CELL Applications Inc. (San Diego, CA, USA), respectively.