Figure 6

Mesenchymal stem cells increase monocyte migration and change the phenotype of macrophages in tissues. Production of CCL2 by MSC was measured in CM from resting MSC and pIC activated MSC (A). The effects of MSC CM on monocyte migration was assessed using Boyden chambers and monocytes isolated from the peritoneal cavity of thioglycollate-treated mice, as described in Methods. Cell migration data was quantitated using Cell Sens software, Olympus). MSC-CM significantly stimulated monocyte migration compared to medium alone, and CM from activated MSC triggered significantly more migration than CM from non-activated MSC (B). In mice treated with MSC in vivo, monocyte recruitment to infected wounds was assessed using CCR2-GFP reporter mice. Monocytes were present in relatively small numbers in tissues of untreated mice (D), whereas the numbers of infiltrating monocytes were significantly higher in mice treated with MSC and further increased in mice treated with activated MSC. These results were verified using tissue samples previously collected from non-GFP reporter mice at the same timepoint. In addition to altering monocyte migration, phenotype of tissue macrophages was also altered in the three groups of mice (control, MSC, aMSC). In tissues of untreated mice (Ctrl) the macrophages were mostly of the M1 phenotype (E) and fluoresced in the red channel.  Mice treated with resting MSC (MSC) had a combination of M1 and M2 (green) macrophages and activated MSC (aMSC) contained mainly M2 macrophages. Monocytes were stained with F4/80, anti-iNOS antibody, and anti arginase antibody. The cells were quantified using Cell Sens software, Olympus) Statistical analysis performed using ANOVA with Tukey multiple means comparison, *denotes p < 0.05.