Erratum to: Novel hyaluronic acid–methotrexate conjugate suppresses joint inflammation in the rat knee: efficacy and safety evaluation in two rat arthritis models

After publication of this article [1] it was noticed that Figs. 2 and 4 (seen below) contained incorrect characters. The corrected figures can be seen below and the original article has also been updated to reflect this.

Fig. 2

Effect of DK226 on proliferation of human synovial fibroblast-like cells (HFLS) and of human synovial sarcoma cell line SW982. a Inhibition of tumor necrosis alpha (TNF-α)-induced proliferation of HFLS by hyaluronic acid (HA) or DK226 at increasing, equivalent HA concentrations. b Effect of exogenously added HA on the anti-proliferative effect of DK226 in HFLS. c Inhibition of proliferation of SW982 by methotrexate (MTX) or DK226 at increasing, equivalent MTX concentrations. d Effect of exogenously added anti-CD44 antibody (BU75) and anti-IgG2a (control antibody) on the anti-proliferative effect of DK226 in SW982. Values are means and standard error of the mean (SEM) (n = 4)

Fig. 4

Effect of DK226 on collagen-induced arthritis (CIA) in rat knee joints. a Effect of intra-articular hyaluronic acid (HA) (0.5 mg) or DK226 (0.5 mg HA-equiv, 26 nmol MTX-equiv) on knee swelling of the right knee (treated) shown on the left panel, and the effect in the left knee (untreated) shown on the right panel. b Histopathology of the right knee joints after treatment with intra-articular HA or DK226. Sections were stained with safranin O/fast green. T tibia, Mmeniscus, F femur. Scale bars indicate 100 μm. c and d Histologic analysis of synovial tissue (c) and lateral condyle of the femur (d). Values are means and standard error of the mean (SEM) (n = 3–10 in a, c and d: n = 3, Normal + vehicle; n = 9–10, CIA + vehicle, HA or DKA226). ^# P < 0.05: significantly different from Normal + vehicle group (Wilcoxon rank sum test). *P < 0.05: significantly different from HA group (Wilcoxon rank sum test)