Figure 9.

Exosomes effect apoptosis of osteosarcoma cells. Murine K7M2 osteosarcoma cells were exposed to 30 ng/cm² (1X) of unlabeled human mesenchymal stromal cell derived exosomes (Naive Exo) or 3000 ng/cm² (100X) or 30,000 ng/cm² (1000X) gadolinium-labeled exosomes (Exo-GdL) suspended in Dulbecco's modified eagle medium (DMEM) supplemented with 10% pooled human platelet lysate depleted of exosomes (dpHPL). K7M2 cells were incubated for 24 h and observed under confocal microscopy (the calibration bar is 20 μm). DMEM with 10% dpHPL media was used as negative control and DMEM with 10% dpHPL with 500 µM of H₂O₂ was the positive control. K7M2 cells were stained with Annexin-V FITC (green) and propidium iodide (PI, red). Double-negative (no staining) were healthy cells, Annexin V-positive stained cells were in early apoptosis (green), cells Annexin V-positive and PI-positive were dead or necrotic cells (green/red). Note that in the Naive Exo panels, one cell in the lower right part of the panel is undergoing cytokinesis and is staining with Annexin V and PI.