In vivo rolling of surface engineered MSCs. (A) In vivo confocal video images of sLe^x-MSCs with velocity 250 μm/s (green) were taken at 30 frames/s within the inflamed ear vessel (blue) after injection of MSCs. (B) In vivo confocal video images of unmodified MSCs with velocity 1100 μm/s (red) were taken at 30 frames/s within the inflamed ear vessel (blue) after injection of MSCs. (A-B) The vessel diameter is approximately 60 μm, and the critical velocity is 571 μm/s. (C) Representative image of sLe^x-MSCs interacting with inflamed endothelium in approximately 60 μm vessel resulting in velocity of 100 μm/s (103 frames stacked with 30 fps; ie, sLe^x-MSC remains in the field of view for > 3.3 seconds). (D) Representative image of unmodified MSCs interacting with inflamed endothelium in approximately 60 μm vessel resulting in velocity of 750 μm/s (27 frames stacked with 30 fps; ie, unmodified MSC remains in the field of view for < 0.9 seconds). Bar represents 50 μm.