However, these studies are currently limited to nuclear and optical imaging methods in RA. Gd-DTPA-IgG disappeared after 80 minutes and 24 ENG hours, respectively. In addition, no significant enhancement was seen in the chronic destructive phase of CIA mice, even though they also showed inflammatory changes on T2-weighted MR images. ICAM-1 expression was demonstrated in the endothelium and proliferating synovium of the early inflammatory phase of CIA mice, but not in the chronic destructive phase. Conclusion Molecular MRI with Gd-DTPA-anti-ICAM-1 displays specific images targeted to ICAM-1 that is expressed in the inflamed synovium Ivabradine HCl (Procoralan) of CIA. This novel tool may be useful for the early diagnosis and differentiation of the various stages of rheumatoid arthritis. strong class=”kwd-title” Keywords: Intercellular adhesion molecules, Gadolinium, Magnetic resonance (MR), Rheumatoid arthritis Rheumatoid arthritis (RA) is a chronic inflammatory disease, and affected individuals experience significant morbidity, including loss of function, joint destruction, and permanent deformity, in addition to having a higher Ivabradine HCl (Procoralan) mortality than the general population (1). Molecular imaging techniques that use targeted agents binding specifically to inflamed synovium are increasingly allowing earlier diagnoses and assessment of a treatment response in RA (2-4). Several studies have shown that it is possible to target and visualize specific cellular processes in arthritic synovium using molecular imaging approaches (5-8). However, these studies are currently limited to nuclear and optical imaging methods in RA. In addition, magnetic resonance imaging (MRI) has not been used despite its particular advantage of simultaneously showing information at the anatomical and molecular levels. The vascular endothelium is an attractive target for imaging and therapy in RA due to its obvious accessibility through the systemic circulation (4-6, 9). The intercellular adhesion molecule (ICAM)-1 is primarily found on synovial endothelial cells and helps recruit lymphocytes, monocytes, and neutrophils to the joints in RA (10-12). ICAM-1 also plays a role in the interactions between activated lymphocytes, fibroblast-like synoviocytes, and macrophage-like synoviocytes in the synovial lining and sublining (12-14). In addition, the immunohistochemical ICAM-1 findings were different for various stages of RA (15), and the potential therapeutic roles of anti-ICAM-1 agents have also been studied in several animal models of inflammatory arthritis and patients with RA (16-18). Thus, ICAM-1 represents a promising molecular target in specific targeted molecular imaging, drug delivery, and tissue engineering for patients with RA. In a previous study, we produced ICAM-1 antibody-conjugated gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA-anti-ICAM-1) as an inflammatory cell-targeted MR contrast agent, which was prepared by bioconjugating Gd-DTPA and anti-ICAM-1. We confirmed that a molecular MRI using the Gd-DTPA-anti-ICAM-1 display targeted T1 MR images specific to ICAM-1 in the mouse abscess model (19). However, to date, no studies that utilize ICAM-1 as a candidate target for molecular MR imaging have been performed in the field of RA. Thus, the current study was designed to evaluate the utility of Gd-DTPA-anti-ICAM-1 as a targeted contrast agent for molecular MRI with a conventional 1.5 Tesla MR machine to diagnose and distinguish different stages of collagen-induced arthritis (CIA). MATERIALS AND METHODS Generation of Gd-DTPA-anti-ICAM-1 and Gd-DTPA-IgG Bioconjugation of both the anti-ICAM-1 antibody and rat IgG (Sigma, St. Louis, MO) to diethylenetriamine pentaacetic acid bisanhydride (DTPABA) and gadolinium chloride (GdCl) was performed according to a previously described procedure (19). Briefly, the anti-ICAM-1 antibody was purified from the culture supernatant of rat hybridoma Ivabradine HCl (Procoralan) using protein A/G-coupled affinity chromatography. The anti-ICAM-1 antibody and rat IgG (control) were conjugated to DTPABA in PBS (pH 8.5) for 1 hour at room temperature. GdCl was dissolved in deionized water and added to the DTPA-antibody conjugate solution. One part of the DTPA-antibody complex was then combined with 40 parts of GdCl in 0.5 M sodium acetate (pH 5.5). The molar ratio of Gd to antibody was about 1:20 in quantitative analysis using ICP-MS (Agilent 7500A, Palo Alto, CA). The Gd-conjugated antibodies did not show any cytotoxic effect on the cultured endothelial cells. The calculated plasma half-life of the Gd-DTPA-antibody conjugate was 3.6 0.16 hours, which is, in turn, ten times longer than that of Gd-DTPA (~20 min). The measured relaxivity (mmol-1sec-1) of the Gd-DTPA-anti-ICAM-1 (23.27 1.31) was higher than that of Gd-DTPA (6.55 0.58) as measured on a.