Figure 2: Two-photon imaging of fluorescently labeled MSCs in the bone marrow of a LysM+/GFP mouse. Real-time imaging of Cell Tracker Orange (CTO) labeled hMSCs in the bone marrow of a LysM+/GFP mouse 1 day after I.V. administration allows for the determination of intact MSCs (red arrows) versus MSCs phagocytosed by GFP+ granulocytes (yellow arrows). The paths of individual cells are tracked (white line). A. Combined GFP and CTO channels with representative pictures over a 10-min period. B. GFP-only channel. C. CTO only channel. D. CTO channel after subtraction of phagocytosed CTO signal. Note: Scale bars=20 μm.