RANKL/OPG expression in OA, RA, and PPA. (a) Normalized average data of the mRNA RANKL/OPG ratio for OA, RA, and PPA. (b) Western blotting analysis of synovial fibroblast total cell lysates showed expression of RANKL and OPG protein. A human osteosarcoma cell line MG63 known to express RANKL and OPG was used as a positive control. (c) Densitometric analyses of bands for RANKL and OPG were obtained using ImageJ software, and results were normalized to basal level.