Correction to: Cyr61 synthesis is induced by interleukin-6 and promotes migration and invasion of fibroblast-like synoviocytes in rheumatoid arthritis

Correction to: Arthritis Res Ther 22, 275 (2020)

https://doi.org/10.1186/s13075-020-02369-8

Following publication of the original article [1], a typesetting error occurred in the spacing of text in Figs. 1a, d, f, Fig. 3f, Fig. 4a–c, e, f, Fig. 5a and f.

Fig. 1

Expression of IL-6 and Cyr61 in fibroblast-like synoviocytes (FLSs). a, b FLSs from osteoarthritis (OA; n = 4) or rheumatoid arthritis (RA, n = 4) patients. *p < 0.05 vs OA. c Synovial tissues from OA or RA patients. Original magnification × 400. d, e RA FLSs stimulated by IL-6/sIL-6R for 2 h. f, g FLSs stimulated by IL-6/s IL-6R (20 ng/mL) for the indicated periods. d–g FLSs were incubated overnight in 1% FBS-containing medium before treatment with IL-6/sIL-6R. a, b, d, f Protein levels were determined by western blotting. e, g The mRNA levels of Cyr61 were determined through real time polymerase chain reaction. Values are means (± standard deviation) of at least three independent experiments. *p < 0.05, **p < 0.01 vs untreated cells. IL-6, interleukin-6; sIL-6R, soluble IL-6 receptor; FBS, foetal bovine serum

Fig. 3

Signalling pathways involved in IL-6-regulated protein synthesis of Cyr61 in rheumatoid arthritis-fibroblast-like synoviocytes (RA-FLSs). a, c, e Cells were pretreated with inhibitors for 2 h before IL-6 (20 ng/mL) stimulation for 2 h. LY294002 (10 μM): PI3K/AKT inhibitor, AG490 (50 μM): JAK2/STAT3 inhibitor, SB203580 (10 μM): p38 MAPK inhibitor, PD98059 (1 μM): ERK inhibitor. d, f RA-FLSs transfected with either small interfering RNA (c-Jun or EGR3) or siNC (control) (20 pmol/L) stimulated by IL-6 (20 ng/mL) for 2 h. Data are representative of at least three independent experiments. a–f Protein levels were determined by western blotting. FLSs were incubated overnight in 1% FBS-containing medium before treatment with IL-6/sIL-6R

Fig. 4

Cyr61 secretion induced by IL-6. a, b Extracellular protein levels of Cyr61 in culture supernatants of IL-6-treated RA-FLSs measured by western blotting. b IL-6 (20 ng/mL). c, d FLSs stimulated by extracellular Cyr61 (100 ng/mL) for indicated time periods. c Protein levels were determined by western blotting. d The mRNA levels of Cyr61 were determined through real time polymerase chain reaction. e–h The mRNA levels of Cyr61, MMP1, 2, and GAPDH induced by IL-6 (20 ng/mL) and extracellular Cyr61 protein (100 ng/mL) for 2 h. e, f The mRNA levels were determined by reverse-transcription polymerase chain reaction. g, h The mRNA levels were determined through real time polymerase chain reaction. Data are representative of at least three independent experiments. *p < 0.05, **p < 0.01, ***p < 0.001

Fig. 5

Migration and invasion of rheumatoid arthritis-fibroblast-like synoviocytes (RA-FLSs) promoted by IL-6 and Cyr61 secretion. a, d, e, g Wound-closure over 17 h. b ECIS proliferation analysis over 72 h. c, f Western blotting for Cyr61 protein detection. h, i Cyr61-stimulated invasion of RA-FLSs in transwells over 24 h ± antiCyr61 ab. f, g transfection with 20 pmol/L of small-interfering Cyr61 RNA (siCyr61) or siNC (negative control). IL-6 for 17 h (a, d, g: 200 ng/mL); IL-6 for 2 h (c, f: 20 ng/mL); IL-6 and Cyr61 protein for 72 h (b: IL-6: 200 ng/mL, Cyr61 protein: 100 ng/mL) Cyr61 protein (a, e: 100 ng/mL; I: 800 ng/mL); antiCyr61 antibody (ab) for 2 h (d: 100 ng/mL; e: 50 ng/mL, i: 50, 100, 200 ng/mL) before IL-6 and Cyr61 protein treatment. h Original magnification × 10. Values are means (± standard deviation) of at least three independent experiments. *p < 0.05, **p < 0.01, ***p < 0.001

The corrected figures are given in this correction article. The original article [1] has been corrected.