Figure 3

Migration of labeled MSC to infected wound sites following i.v. administration. In (A–C) representative wound tissues from animals receiving no MSC (A), resting MSC (B) and activated MSC (C). MSC were labeled with the fluorescent membrane dye DiD and detected via fluorescent microscopy (DiD⁺ cells light blue in these images). Animals were injected with labeled MSC 24 hours after implantation of infected mesh and received a second injection 3 days later. Animals were sacrificed 2 days after the second injection and tissues were evaluated histologically. Quantitative counts of DiD⁺ cells revealed significantly more cells present in tissues from animals receiving activated MSC (D). All animals in this study received antibiotics. Counts were compared using ANOVA with *depicting p < 0.05. In (E,F), wound tissues from a control animal and an animal injected i.v. with activated GFP-transgenic MSC to allow detection in wound tissues. Cells were administered 2 separate injections 3 days apart, and 48 h later, the wound tissues were collected and evaluated by fluorescence microscopy for detection of GFP + cells (F). In other studies, MSC (activated or non-activated) were labeled with the fluorescent dye DiR, and live mice were imaged using an IVIS imager (G–I). In the first 24 h after injection, DiR + cells were detected in the lung and spleen. By 48 h post-injection, DiR + cells were apparent in the region of the infected wound. The cells accumulated at the wound sites and images were taken 3 days after the third MSC injection (H,I). There were also more activated DiR + cells localized in the region of the wound than in mice injected with non-activated cells. Similar results were obtained in one additional animal study.