Fig. 1

Osteogenic differentiation of rheumatoid arthritis (RA)-fibroblast-like synovial cells (FLS) cultured in osteogenic induction medium. a Representative images of alkaline phosphatase (ALP) staining (right) and Alizarin Red staining (left). RA-FLS (n = 6) were cultured in osteogenic induction medium or control medium. After 21 days, cells were stained with ALP and Alizarin Red. b Representative image of the morphology of RA-FLS with ALP staining. Right: RA-FLS were cultured in control medium. Left: RA-FLS were cultured in osteogenic induction medium (magnification × 200). c Visualization of calcified nodules by Alizarin Red staining. RA-FLS were cultured in osteogenic induction medium (magnification × 400). d RA-FLS (n = 5) were cultured in osteogenic induction medium or control medium for 21 days. Expression of ALP, runt related transcription factor 2 (RUNX2) was determined by quantitative real-time PCR. Values are presented as means ± SEM: *p < 0.05 versus control, as determined by Student’s paired t test or Wilcoxon matched-pairs signed rank test