Enhancing Cell-Based Regenerative Therapies with Peptide-Modified Thermo-responsive Citrate-Based Biomaterials for Treatment of Critical Limb Ischemia

Critical limb ischemia (CLI) poses a significant health challenge, marked by severe morbidity and limited treatment options leading to high mortality rates. Despite the promise of cell-based therapy, challenges such as poor cell survival and engraftment during and after cell delivery hinder its efficacy. This study explores the potential of peptide-modified thermo-responsive citrate-based biomaterials as carriers for endothelial cell delivery to promote vascular regeneration in CLI. Specifically, various pro-survival peptides were covalently tethered to poly(polyethylene glycol citrate-co-N-isopropylacrylamide) (PPCN) to investigate their effect on the delivery of vascular endothelial cells to skeletal muscle tissue. After screening with in vitro and in vivo experiments, laminin-derived peptide A5G81 and VEGF-derived peptide QK were identified to promote endothelial cell spreading, proliferation, and prolonged cell survival when tethered onto PPCN The viscoelastic properties of PPCN provided protection against shear stress induced cell death during injection, while the peptides regulated endothelial cell behavior via distinct molecular pathways. Importantly, intramuscular delivery of endothelial cells with PPCN-A5G81 and PPCN-QK in a murine hindlimb ischemia model resulted in significant improvements in limb perfusion, tissue preservation and functional outcomes. Furthermore, endothelial cell delivery with PPCN-A5G81 and PPCN-QK also promoted positive skeletal muscle remodeling following ischemic injury. These findings underscore the potential of bioactive materials as novel cell delivery carriers for CLI therapy, with implications for advancing regenerative therapeutics and revolutionizing CLI treatment strategies.