Dynamic Imaging of Marrow-Resident Granulocytes Interacting with Human Mesenchymal Stem Cells upon Systemic Lipopolysaccharide Challenge

Figure 4

Cellular fragmentation of a dying hMSC followed by phagocytosis of migrating LysM⁺ GFP⁺ granulocyte engulfing hMSC debris. (a) Intravital TPM images of a different area of the calvarium bone marrow from Figures 2 and 3, demonstrating the dramatic fragmentation of the CTO-labeled (red) hMSC cell body (white arrow) into at least 4 pieces over a period of 40 minutes (𝑡=0^′ corresponds to 20 minutes prior to LPS injection). Scale bar = 20 μm. (b) A LysM⁺ GFP^dim cell containing phagocytosed CTO-labeled hMSC debris is shown to demonstrate colocalization of GFP (green) and CTO (red) signals (inset: zoomed view at 𝑡=80^′ with (left; “merged”) and without (right; “GFP only”) CTO signal). (c) A LysM⁺ GFP⁺ CTO⁺ cell exhibited a highly motile behavior over a long distance in the bone marrow (white tracks) over a 60-minute imaging period. Scale bar outset = 50 μm; inset scale bar = 10 μm.

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