Bone erosions are augmented in the IL-10KO joints following antigen-induced arthritis (AIA). (A) Mankin's score (indicating severity of cartilage damage) (left) and percentage of cartilage degradation of mouse joints (right) at day 28 and 35 post arthritis induction (mean ± SEM, n = 6-7 mice/time point from a single experiment; P <0.05 between WT (closed circles) and IL-10KO (open circles) groups). (B) Representative Haematoxylin and `safranin-O Green-stained parasagittal joint sections (left) taken on day 35 are shown for WT and IL-10KO mice. The star indicates cartilage degradation and diamond shows bone erosion (scale bar: 100 μm). Representative F4/80 staining (right) adjacent to bone erosions in joint sections (scale bar: 500 μm) from IL-10KO mice three days post AIA (right). (C) Radiographic scoring (left) and representative radiographic images (right) of the joints of WT and IL-10KO mice 28 days post arthritis induction. Representative images are presented from a single experiment using six to eight mice per mouse strain. (D) WT and IL-10KO joints were stained for TRAP positivity (left) on day 28 post AIA (scale bar: 200 μm) and quantified by computer analysis (top middle) (n = 3-5 mice), and expression in the joints of osteoclast marker; Acp6 was determined by qPCR and made relative to the values for 18S ribosomal RNA (n = 9 mice) (top right). Serum DKK1 (bottom) was detected using commercial ELISA in samples obtained from challenged WT and IL-10KO mice (n = 6-7 mice/mouse strain, *P <0.05). DKK1, dickkopf-1; ELISA, enzyme-linked immunosorbent assay; IL-10KO, interleukin-10-deficient; qPCR, quantitative real-time PCR; TRAP, tartrate-resistant alkaline phosphatase; WT, wild-type.