Fig. 2: Involvement of FGFR3 and RSK2 in RA in humans.

a Representative double immunohistochemical analysis of human RA synovial tissues (×100, n = 3). The tissues were hybridized with a combination of phospho-RSK2 (Thr577) antibody (shown in brown), CD68 (a macrophage marker, shown in red), CD3 (a T-cell marker, shown in red), and CD20 (a B-cell marker, shown in red), as indicated. Boxed area was magnified (×400). The area marked by the blue dotted line indicates the hyperplastic lining layer, and the area marked by the green dotted line indicates the sublining layer in synovium. b, c The knockdown effects of RSK2 on cell proliferation (b) and cell migration (c) in human RA FLSs. Cell proliferation was measured by MTS assay (b), and the migrated area (graph) was quantified by measuring the uncovered area of the wound using Image J (Ver. 1.6). Scale bars, 100 μm (c). Data were obtained from three independent experiments, and values are represented as means ± SEM. *p < 0.001 by Student’s t-test. d Representative photographs (×40) of triple immunohistofluorescence analysis of tissues obtained from OA (n = 5) and RA (n = 5) patients. p-RSK2 and p-FGFR3 were co-stained with CD4- (a T-cell marker; upper panels) or CD68- (a macrophage marker; bottom panels) specific antibodies as indicated and analyzed by confocal microscopy. Yellow color in the merged photographs indicates the coexistence of CD4⁺ T-cells or CD68⁺ macrophages in the synovial tissues of OA and RA patients, respectively. Scale bars, 40 μm