Figure 4

MSCs injected into the joint localise to the synovium. 500,000 CM-DiI-labelled red-fluorescent mouse MSC were injected intra-articularly into the knee joint spaces of mice with antigen-induced arthritis. (A) low magnification image of a mouse joint 2 days after MSC injection, the arrows indicate MSCs (red) localising to the synovium. (B) joint of control treated mouse 2 days after MSC injection, no red fluorescence, DAPI blue. (C) low magnification H&E stained image of a mouse joint 2 days after MSC injection (same joint as A), the arrows indicate regions of MSC localisation (corresponding to A). (D) higher magnification showing MSCs localising to the lining of synovium (C-cartilage; L-lining layer of the synovium; S-sublining layer of the synovium). DAPI stain cell nuclei. (E) sections were treated with rabbit anti- von-Willebrand factor antibodies followed by goat anti-rabbit Alexa 488 to identify endothelial cells (arrows) in MSC-injected joints. Absence of red fluorescence in F- contra-later joint, G- lungs, H-spleen and I-liver. Scale bar 500 μm in A, B, C; 50 μm in D and E; and 200 μm in F-I.