Abstract 019: Diabetic Endothelial Progenitor Cells in Combination with an RGDS Presenting Peptide Amphiphile Enhance Recovery from Critical Limb Ischemia in Diabetic Mice

Approximately two million people suffer from critical limb ischemia (CLI) with the prevalence of the disease expected to rise. Thus, there is a crucial need to develop new therapies to enhance angiogenesis and minimize the impact of the blocked vessel(s). Cell therapy using endothelial progenitor cells (EPCs) has shown some promise, however, the cells may not remain at the site of injury long enough to significantly impact the course of the disease. Further, the use of autologous cells may be problematic as the underlying disease, such as diabetes, which resulted in CLI also appears to negatively impact the function of EPCs. Thus, we propose to use a biomaterial in combination with the EPCs to enhance both the retention of cells at the site of injury and also enhance the function of the cells. A self-assembling peptide amphiphile (PA) was developed with an attached functional group consisting of the cell-attachment sequence of peptides identified in fibronectin: RGDS. We hypothesize that EPCs combined with RGDS PA will improve the angiogenic response in CLI. Indeed, in vitro we found that EPCs from diabetic mice (db/db) exhibited increased survival on an RGDS PA in comparison to a scrambled sequence (DGRS) PA as measured by calcein-AM and ethidium homodimer-1 staining. To test if this enhanced survival would improve critical limb ischemia in diabetic mice, uni-lateral ischemia was induced by ligation of the femoral artery. Three days post surgery ischemia was confirmed by laser Doppler and the following treatments were injected into the ischemic limb of the diabetic mice: (1) PBS (2) scrambled PA (3) RGDS (4) scrambled PA +100,000 diabetic EPCs (5) RGDS PA + 100,000 diabetic EPCs. At four weeks post-injection, blood flow (as measured by laser Doppler) was increased in the group receiving RGDS PA when compared to the other groups (n>6). Further, necrosis was decreased in the RGDS PA group and muscle regeneration, as measured by the number of central nuclei, was increased in the RGDS PA group. Taken together, these results suggest that RGDS PA in combination with db/db EPCs enhances recovery from CLI in diabetic mice.