The role of stem cell growth factor in rheumatoid arthritis

Abstract

Stem cell growth factor (SCGF) is discovered as a growth factor of hematopoietic precursor cells in the bone marrow. The role of SCGF in inflammation has not been previously investigated. Rheumatoid arthritis (RA) is characterized by the presence of chronic inflammatory cell infiltrates in synovial tissues. Chemotaxis, angiogenesis, and immune cell proliferation are all important pathways in RA that maintain chronic inflammation. Various growth factors have been shown to be involved in RA pathogenesis by promoting the survival of inflammatory cells. Therefore, the role of SCGF in inflammation was evaluated using samples derived from RA patients. SCGF levels in RA synovial fluid were significantly elevated compared to SCGF levels in osteoarthritis synovial fluid. Immunohistochemical analyses demonstrated that SCGF is highly expressed in the endothelium of synovial tissues derived from RA patients. Various endothelial cells, such as HUVECs and EA.hy926 cells, express SCGF; proinflammatory signals induce SCGF expression in endothelial cells. SCGF promotes differentiation and increases TNF production in macrophages. SCGF expression is also increased in bone marrow cells derived from arthritic mice. Taken together, SCGF produced by endothelial cells in synovial tissues during inflammation plays an important role in RA by promoting macrophage differentiation.