Characterisation of FLS and AGE uptake. (a) Immunohistochemical staining of fibroblast-like synovial cells (FLS) cultured from osteoarthritic synovial tissues. FLS were stimulated with control-BSA (Co-BSA) or advanced glycation end products-modified (AGE)-BSA (5 mg/ml) for 24 hours. FLS stained positive for the fibroblast marker CD90 and AGE-BSA incubation had no influence on CD90+ expression. The intensive intracellular staining for Nε-carboxymethyllysine (CML) and imidazolone in AGE-BSA treated cells in comparison with Co-BSA suggests active uptake of AGE. (b) Western blot for CML. FLS treated with AGE-BSA expressed more CML protein than cells incubated with Co-BSA.