Amelioration of Inflammation, Angiogenesis and CTGF Expression in an Arthritis Model by a TSP1-Derived Peptide Treatment.

Abstract

Objective. To evaluate the effect of a thrombospondin 1 (TSP1)-derived peptide on inflammation and angiogenesis in an animal model of erosive arthritis and to assess the relationship between TSP1 and connective tissue growth factor (CTGF) in the pathophysiology of rheumatoid arthritis.Methods. Erosive arthritis in Lewis rats was induced by peptidoglycan-polysaccharide (PG-APS). Animals were divided into four groups:negative control and groups receivingno treatment,treatment with a TSP1-derived peptide andtreatment with a scrambled peptide.Samples obtained from ankle joint, spleen and liver were studied using histology, histomorphometry, immunohistochemistry and RT-PCR.Results. Histological data indicated that TSP1-derived peptide treatment decreased neovascularization, leukocyte infiltration and thickening of the synovial lining of the joint, and reduced granuloma formation in spleen and liver when compared to control groups. Higher concentrations of CTGF and TSP1 proteins were observed in the affected areas of animals which did not receive TSP1-derived peptide treatment. Also, immunohistochemical and RT-PCR analyses showed an increase of the CTGF protein expression and regulation, respectively, in the tissues of untreated animals when compared to TSP1-derived peptide treated animals. By immunohistochemistry, TSP1 expression was decreased in the TSP1-derived peptide treated animals. Moreover, macrophage/monocyte-specific staining revealed a decrease in cell infiltration in the articular tissue of the TSP1-derived peptide treated animals.Conclusion. Both inflammation and angiogenesis were decreased after TSP1-derived peptide treatment indicating a potential pathway by which TSP1 interaction with neutrophils induces CTGF in RA affected tissues.Vasculature measurements at the perisynovial tissue of the TSP1-derived peptide treated (DT) and scramble peptide treated (DS) animals after day 16 PG-APS-induced erosive arthritis.Vascular MeasurementsDisease TSP1-derived peptide treated (DT)Disease scrambled peptide treated (DS)P ValueVascular area mean±SEM (μm2)77.41 ± 7.96 μm2336 ± 49.21 μm2p=0.0008Vessel wall thickness (μm)3.53 ± 0.21μm8.92 ± 0.48;μmp<0.0001Vascular index (VI) ± SEM (VI=total number of vessels/mm2)5.6x10−3 ± 0.37x10−3 vessels/mm217.9x10−3 ± 1.33x10−3 vessels/mm2p=0.006