GPI promotes the proliferation of FLS isolated from RA or OA patients. A, FLS were transfected with expression plasmids and siRNAs. After 72 hours, the expression of GPI and GP78 was evaluated by Western blot analysis. B, The growth curve of FLS after GPI overexpression and knockdown (top). The growth curve of FLS after GP78 overexpression and knockdown (bottom). Cell proliferation capacity was determined by MTT assay every 24 hours. A(a) NC-vector versus GPI/gp78-vector, A: P <0.01, a: P <0.05; B(b) si-NC versus si-GPI/gp78, B: P <0.01, b: P <0.05. P values were determined by Wilcoxon signed-rank test. C, The proliferation of FLS after treatment with GPI (1, 10 μg/ml) for 48 hours. D, The proliferation of FLS after treatment with anti-GPI Ab (1, 10 μg/ml) for 48 hours. Friedman’s M test and SNK-q test were used for statistics. (N = number of individuals, R = number of replicates; GPI, glucose 6-phosphate isomerase; gp78, glycoprotein 78;RA, rheumatoid arthritis; OA, osteoarthritis; FLS, fibroblast-like synoviocytes; NC, negative control; OD, optical density).