Magnetic resonance imaging of synovial macrophages in rat collagen-induced arthritis / 中华风湿病学杂志

ABSTRACT

Objective To prospectively evaluate the ability of 7.0 T magnetic resonance (MR) imaging enhanced with ultrasmall superparamagnetic iron oxide (USPIO) particles in detecting synovial macrophages in a rat model of collagen-induced arthritis (CIA).Methods CIA was induced by subcutaneous injection of chicken type Ⅱ collagen.Arthritis rats were randomly divided into early,middle and late model group.Other rats served as controls.Knees of rats were imaged by a 7.0 T MR imager before and 24 hours after USPIO intravenous administration (200 μ.mol Fe/kg) on Day 14,28,42,respectively.The MR imaging protocol included T1-weighted (T1W) spin-echo (SE) sequences,T2-weighted (T2W) SE sequences,T2 * W gradientecho (GRE) sequences.After the completion of MR imaging,rats were sacrificed to obtain histopathologic samples of synovial membrane and staining.LSD-t test and one-way ANOVA were used for statistical analysis.Results Knees of arthritis rats in early,middle and late model groups developed synovial thickening and joint effusion on images from all sequences,whereas not developed in the control group.On USPIO-enhanced images,synovial tissue of arthritis knees showed slight to distinct signal intensity loss on post contrast T2WI and T2WI.However,no signal intensity enhancement of inflamed synovium was observed on postcontrast T1WI.Meanwhile,no control knees developed any visually detectable changes between pre-and postcontrast images.The quantitative analyses were coincident with the visual differences in signal changes between preand postcontrast images.Histologic examination confirmed uptake of iron in the macrophages of arthritic knees.Conclusion USPIO enhanced 7.0 T MR imaging can detect synovial macrophages in different period of CIA,which may be an additional tool for early and accurate diagnosis of RA.