We have examined the expression and function of the angiogenic factor, vascular endothelial growth factor (VEGF) during the evolution of type II collagen-induced arthritis (CIA). Biologically active VEGF was expressed along a time course that paralleled the expression of two specific VEGF receptors, Flk-1 and Flt-1, and the progression of joint disease. Moreover, levels of VEGF expression correlated with the degree of neovascularization, as defined by vWF levels, and arthritis severity. Macrophage- and fibroblast-like cells, which infiltrated inflamed sites and were then activated by other inflammatory mediators, are probably important sources of VEGF and may thus regulate angiogenesis during the development of CIA. Administration of anti-VEGF antiserum to CIA mice before the onset of arthritis delayed the onset, reduced the severity, and diminished the vWF content of arthritic joints. By contrast, administration of anti-VEGF antiserum after the onset of the disease had no effect on the progression or ultimate severity of the arthritis. These data suggest that VEGF plays a crucial role during an early stage of arthritis development, affecting both neovascularization and the progression of experimentally induced synovitis.
Most of the leucocytes infiltrating rheumatoid synovial fluid (SF) are neutrophils capable of producing a variety of inflammatory mediators known to contribute significantly to the disease process during active RA. In the present study, we investigated the contribution made by SF neutrophils to the elevated levels of vascular endothelial growth factor (VEGF) seen in rheumatoid SF. Rheumatoid SF neutrophils were found to contain significantly larger amounts of both VEGF protein and its mRNA than peripheral blood neutrophils from either RA patients or healthy controls. Levels of cell‐associated VEGF were well correlated with free VEGF in SF, which was significantly higher than in SF from osteoarthritis patients. Levels of SF neutrophil‐associated VEGF also correlated with RA disease activity and cell surface integrin expression. Thus, SF neutrophil‐associated VEGF may be considered an indicator of both local and systemic inflammation of RA, contributing to the neovascularization seen during RA synovitis.
(Print ISSN 1478-6354; Online ISSN 1478-6362). This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any non-commercial purpose, provided this notice is preserved along with the article's original URL. AbstractChemokines play an essential role in the progression of rheumatoid arthritis (RA). In the present study we examined the expression and regulatory mechanisms of IFN-γ inducible protein (IP)-10 in RA synovitis. RA synovial fluid contained greater amounts of IP-10 than did synovial fluid from patients with osteoarthritis. Immunolocalization analysis indicated that IP-10 was associated mainly with infiltrating macrophage-like cells, and fibroblast-like cells in the RA synovium. The interaction of activated leukocytes with fibroblast-like synoviocytes resulted in marked increases in IP-10 expression and secretion. Moreover, induction of IP-10 was mediated via specific adhesion molecules, as indicated by the finding that both anti-integrin (CD11b and CD18) and intercellular adhesion molecule-1 antibodies significantly inhibited IP-10 induction. These results suggest that IP-10 expression within inflamed joints appears to be regulated not only by inflammatory cytokines but also by the physical interaction of activated leukocytes with fibroblast-like synoviocytes, and that IP-10 may contribute to the recruitment of specific subpopulations of T cells (Th1 type) from the bloodstream into the synovial joints.
Objective To examine the expression and regulation of the angiogenic factor, vascular endothelial growth factor (VEGF), by fibroblast‐like synoviocytes (FLS), monocytes, and polymorphonuclear neutrophils (PMNs) isolated from the synovial fluid (SF) of rheumatoid arthritis (RA) patients. Methods Monocytes or PMNs obtained from RA SF were cocultured with unstimulated, semiconfluent RA FLS. Culture supernatants were assayed for the proliferation and in vitro tube formation of endothelial cells, and for the production of VEGF, by enzyme‐linked immunosorbent assay. The expression of VEGF messenger RNA and protein was also determined by reverse transcription–polymerase chain reaction and immunohistochemistry, respectively. Results We found that the interaction of inflammatory, activated leukocytes with FLS resulted in synergistic increases in VEGF expression and secretion, which contributed to the proliferation of endothelial cells and to in vitro endothelial tube formation. The induction of VEGF was mediated via specific adhesion molecules, as indicated by the finding that anti‐integrin antibodies significantly inhibited VEGF. Furthermore, the levels of VEGF secretion correlated with the expression of cell surface integrin (CD11b and CD18) on both monocytes and PMNs in the SF. Conclusion VEGF expression within inflamed joints thus appears to be regulated not only by inflammatory cytokines, but also by the physical interaction of activated leukocytes and FLS. Once expressed, VEGF likely plays a crucial role in the neovascularization of the pannus and the progressive joint destruction associated with the synovial inflammation of RA.
We evaluated the occurrence of cytomegalovirus (CMV) infection and the background characteristics in twenty-three hospitalized patients with inflammatory connective tissue diseases including systemic lupus erythematosus, polymyositis/dermatomyositis, rheumatoid vasculitis, microscopic polyangitis, and Takayasu's arteritis. Cytomegalovirus antigenemia was demonstrated in 10 of 23 evaluable patients. Five of ten patients with CMV antigenemia developed symptomatic CMV disease (all cases of fever, two cases of liver involvement, two cases of interstitial pneumonia, and one case of unknown organ involvement), whereas the remaining five patients were asymptomatic. Most of CMV antigenemia-positive patients had been administered intravenous steroid pulse, or in combination with immunosuppressive agents intravenously or orally because of refractory disease activity. Particularly, in patients who received intravenous methylprednisolone pulse in combination with additional intravenous cyclophosphamide pulse, the incidence of CMV antigenemia was markedly higher (four out of four). Four of ten CMV antigenemia-positive patients simultaneously showed detection of Pneumocystis jiroveci in induced sputum by PCR, increase in level of serum beta-D-glucan and the finding of geographical ground-glass opacities on chest computed tomography. These findings suggested that patients with connective tissue diseases under intensive immunosuppressive therapies (intravenous steroid pulse in combination with additional intravenous cyclophosphamide pulse in particular) are highly susceptible to CMV infection and disease, and that patients complicated by CMV antigenemia are susceptible to combined opportunistic infection such as Pneumocystis pneumonia.
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