Figure 1

Expression of interleukin-34 (IL-34) in human rheumatoid arthritis (RA) synovium and synovial fluid (SF). (A) IL-34 and macrophage colony-stimulating factor (M-CSF) mRNA levels in synovia from patients with RA (n = 3) and osteoarthritis (OA) (n = 3) were determined by reverse transcriptase PCR (RT-PCR). Synovium were homogenized and lysed, and total RNA was extracted as described in Materials and Methods. Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) mRNA levels were detected as a control. (B) Representative immunohistochemical images of OA or RA synovia stained with antibodies against IL-34 or isotype controls. Images are shown at 200× (upper) and 400× (lower) magnification. Scale bars = 100 μm. (C) Synovial fluid (SF) from RA patients (n = 7) (RA SF) was collected and the concentrations of M-CSF and IL-34 were measured using an enzyme-linked immunosorbent assay (ELISA) assay. (D) Expression of IL-34 protein in fibroblast-like synovial cells (FLS) from RA patients (n = 6) was determined by immunoblotting against human IL-34. Whole-cell lysates of RA FLS cells were resolved by SDS-PAGE and followed by immunoblotting with anti-human IL-34 and anti-β-actin antibodies.