Background: CD34+ cells have shown unprecedented promise for ischemic tissue repair in recent clinical trials; however, their recruitment, retention, and survival in the injured tissue remain one of the major barriers to the success of this novel therapeutic strategy.
Methods and Results: In this study, we have developed a self-assembling bioactive peptide amphiphile (PA) nanofiber that displays the integrin-recognized cell adhesion epitope RGDS and tested this novel scaffold material for therapeutic delivery, retention, and functional support of human CD34+ cells in a mouse model of critical hind-limb ischemia (CLI). In culture, PA nanofibers, but not non-bioactive nanostructures or nanostructures with scrambled DGRS epitope, significantly enhanced the adhesion and survival of human CD34+ cells under a number of cellular stresses. In CLI nude mice, intramuscular injection of human CD34+ cells contained in the RGDS nanostructures led to a significantly better blood perfusion, motor ability, limb salvage, and treadmill endurance when compared with those of CD34+ cells contained in DGRS nanostructures, cells alone or RGDS alone. Histology analyses revealed a better viability and retention of CD34+ cells in the limb tissue of the RGDS nanostructures/CD34+ cells group than in the RGDS nanostructures alone or cells alone group. In consistent with the improved functional recovery, the density of capillaries in the ischemic limb of RGDS nanostructures/CD34+ cells group was significantly greater than in other groups.
Conclusions: Our data demonstrate that integrin-specific binding epitope RGDS nanostructure enhances viability, adhesion, and angiogenic capability of human CD34+ cells. This pre-clinical study provides a rationale for further investigation of combining RGDS PAs with human CD34+ cells to enhance the effectiveness of cell therapy for ischemic limb disease.