Fig. 1

Correlation between adiponectin (AD) and osteopontin (OPN) expression in serum and synovial tissue of patients with rheumatoid arthritis (RA). a Serum AD levels were determined in patients with RA (n = 38) and in healthy controls (HC) (n = 20) by ELISA. b Serum OPN levels were measured in patients with RA (n = 38) and HC (n = 20) by ELISA. c The positive relationship between serum AD and OPN levels in patients with RA. d Serum AD levels were examined in patients with osteoarthritis (OA) (n = 40) and in HC (n = 20) by ELISA. e Serum OPN levels were tested in patients with OA (n = 40) and in HC (n = 20) by ELISA. f No relationship is observed between serum AD and OPN levels in patients with OA. g Double immunofluorescence analysis of AD and OPN expression in RA and OA synovial tissue (n = 3). Each section was merged with 4’,6-diamidino-2-phenylindole (DAPI) (magnifications: ×20). Bars show the mean ± SD. The degree of linearity between the two variables was compared using Spearman’s correlation test (two-tailed). **p < 0.01 versus control (a, b and e)