The Mechanisms Of Inhibiting Angiogenesis Of Recombinant Human Endostatin On Rats With Adjuvant Arthritis

AIMTo investigate the effects of recombinant human endostatin (RHE) on rats with adjuvant arthritis and its mechanisms of inhibiting angiogenesis.METHODSThe model of rat AA was induced by injection of intradermal complete Freund's adjuvant (CFA). The secondary inflammation of AA rats appeared on the 10th day. The therapeutic administration of endostatin (0.1, 0.5, 2.5 mg-kg-1 d-1,sc, 7d) was given at that time(dlO). The rats in normal group and model group were administrated with sterile injection liquid.Interleukin (IL)-1 , tumor necrosis factor- (TNF-a) produced by synoviocytes was estimated with radioimmunoassay. Synovial cells from rat knees were dispersed with sequential incubation of collagenase type II and trypsin. Fibroblast-like synoviocytes were derived from explant culture of tissue fragment of AA rats. Morphological changes of synovial cells were observed by scanning electron microscope. The number of new blood vessel's in knee joint synovium was counted under microscope by hematoxylin and eosin (HE) staining. The changes of vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF), TNF-a, VIII factor of the cultured synoviocytes and synovial tissue were estimated with immunohistochemistry assay.RESULTS1. Effect of endostatin on cytokinesThe cytokines of AA rats were determined on d28 after immunization. Synoviocytes increased in AA rats compared with that in the normal group, and so did TNF-a derived from synoviocytes. The administration of endostatin (0.5, 2.5 mg-kg-1-d-1, sc) for 7 days significantly decreased the production of IL-1 by synoviocytes. This effect of endostatin was also seen on TNF-a level at all the doses that were used in this experiment.2. The number of new blood vessels of synovial liningAngiogenesis means the formation of new blood vessels from preexisting vessels. There are a few new blood vessels in the synovial lining of normal rats. The number of new blood vessels in hyperplasia synovium of AA rat increased significantly observed under microscope by HE staining. However, the new blood vessels are less in the thin synovial tissue of rats treated with endostatin (0.5, 2.5 mg-kg-1) than that in AA control on d28 after immunization.3. Expression of VEGF, FGF, TNF- and VIII factor of the synoviocytes and synovial tissueThe expressions of VEGF, FGF, TNF-a and VI factor of normal rats are less than model rats. The therapeutic administration of endostatin (0.1, 0.5, 2.5 mg kg-1) has significantly inhibitory action on expression of VEGF, FGF, TNF-a and VIII factor.CONCLUSIONThe RHE had an inhibitory effect on rat AA, which was related to its antiangiogenesis and inhibition of proinflammatory factors.