Optical Quantification of Disease Activity using Hydrophobically Modified Glycol Chitosan labeled with Near-Infrared Fluorescence in Experimental Arthritis Model (42.25)

Abstract

Abstract Objective. To investigate the quantitative analysis of disease activity using the optical imaging system with hydrophobically modified glycol chitosan labeled with Cy5.5 (HGC-Cy5.5) in animal arthritis model. Methods. Fluorescence reflectance images were captured two hours after intravenous injection of HGC-Cy5.5 nanoprobe from the paws of collagen-induced arthritis mice. Immunofluorescence staining for F4/80 and Mac-1 molecules were performed to identify the cell types phagocytosing HGC nonoprobe, both in vivo and in vitro. Results. In raw reflectance images, paws of the active arthritis group showed stronger fluorescence intensity than those of nonarthritis group. According to the progression of arthritis, total photon counts (TPC) increased until 5 weeks after the booster injection in parallel with the clinical arthritis index. The quantitative analysis of fluorescence intensity showed that the TPC had significant differences in methotrexate treated groups compared with an untreated group. Fluorescence microscopy demonstrated considerable accumulation of HGC-Cy5.5 within the synovial tissues, with the localization of the probe within the interstitial and a portion of cells expressing Mac-1 molecule. Macrophages differentiated with the stimulation of GM-CSF revealed conspicuous intracellular NIRF signal after two hours of incubation with the HGC-Cy5.5, with up-regulated expression of Mac-1 on the surface. Conclusion. The present results indicate that the quantitative analysis of joint inflammation using HGC-Cy5.5 nanoprobe can provide an objective measurement of disease activity in RA.