Figure 1

The evolution of superparamagnetic iron oxide nanoparticles (SPION)-labeled macrophages signal on magnetic resonance (MR) images in the presence and absence of dexamethasone (Dexa). (A) T1-weighted images (negative contrast) of SPION-labeled macrophages in the synovium during AIA. SPIONs were administered intravenously on day 5 post-AIA induction. Panel (i-iii) shows representative MR images from a control (untreated) animal with AIA and panel (iv-vi) shows MR images of a Dexa-treated animal on days 6, 10 and 13 post-AIA induction respectively. (B) T1-weighted images of SPION-labeled macrophages post-Gd administration of the same two animals shown in A. SPION signal is seen as a negative contrast, and Gd signal is seen as a positive contrast and depicts synovial edema. Panel (i-iii) shows representative MR images from a control (untreated) animal with AIA and panel (iv-vi) shows MR images of a Dexa-treated animal on days 6, 10 and 13 post-AIA induction respectively. White arrows, SPION signal (dark); red arrows, quadriceps tendon to patella (dark u-shaped line); yellow arrows: femur and tibia; broken yellow arrow, inflamed synovium (bright signal); broken orange line, edema pocket anterior to the femur. Similar results were seen in 13 untreated controls and 15 Dexa-treated animals. AIA, antigen-induced arthritis; Gd, gadolinium chelate.