Advanced glycation end products induce cell cycle arrest and proinflammatory changes in osteoarthritic fibroblast-like synovial cells

Introduction Advanced glycation end products (AGEs) have been introduced to be involved in the pathogenesis of osteoarthritis (OA). The influence of AGEs on osteoarthritic fibroblast-like synovial cells (FLS) has been incompletely understood as yet. The present study investigates a potential influence of AGE-modified bovine serum albumin (AGE-BSA) on cell growth, and on the expression of proinflammatory and osteoclastogenic markers in cultured FLS. Methods FLS were established from OA joints and stimulated with AGE-BSA. The mRNA expression of p27(Kip1), RAGE (receptor for AGEs), nuclear factor kappa B subunit p65 (NF kappa B p65), tumor necrosis factor alpha (TNF-alpha, interleukin-6 (IL-6), receptor activator of NF kappa B ligand (RANKL) and osteoprotegerin was measured by real-time PCR. The respective protein expression was evaluated by western blot analysis or ELISA. NF kappa B activation was investigated by luciferase assay and electrophoretic mobility shift assay (EMSA). Cell cycle analysis, cell proliferation and markers of necrosis and early apoptosis were assessed. The specificity of the response was tested in the presence of an anti-RAGE antibody. Results AGE-BSA was actively taken up into the cells as determined by immunohistochemistry and western blots. AGE-induced p27(Kip1) mRNA and protein expression was associated with cell cycle arrest and an increase in necrotic, but not apoptotic cells. NF kappa B activation was confirmed by EMSAs including supershift experiments. Anti-RAGE antibodies attenuated all AGE-BSA induced responses. The increased expression of RAGE, IL-6 and TNF-alpha together with NF kappa B activation indicates AGE-mediated inflammation. The decreased expression of RANKL and osteoprotegerin may reflect a diminished osteoclastogenic potential. Conclusions The present study demonstrates that AGEs modulate growth and expression of genes involved in the pathophysiological process of OA. This may lead to functional and structural impairment of the joints.