Prolonging Endothelial Cell Survival with Thermoresponsive Peptide-Functionalized Hydrogels Improves Ischemic Limb Tissue Regeneration and Function

Critical limb ischemia (CLI) presents a significant clinical challenge, leading to tissue ischemia and potentially resulting in limb necrosis or amputation. Cell-based regenerative therapies offer promise for improving outcomes in CLI, but their effectiveness is often limited by poor cell survival and engraftment. This study hypothesized that a thermo-responsive polymer, poly(polyethylene glycol citrate-co-N-isopropylacrylamide) (PPCN), combined with pro-survival bioactive peptides, can create a protective microenvironment to improve endothelial cell survival and function after their delivery. Through in vitro and in vivo experiments, laminin-derived peptide A5G81 and vascular endothelial growth factor (VEGF)-derived peptide QK are identified as effective in promoting endothelial cell spreading, proliferation, and prolonged survival. PPCN's viscoelastic properties protected against shear stress during injection, while the peptides supported endothelial cell behavior through distinct molecular pathways. Importantly, 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 compared to controls. Additionally, this approach enhanced skeletal muscle remodeling following ischemic injury. This innovative biomaterial platform represents a versatile solution for addressing cell survival challenges and advancing regenerative therapies in CLI and other ischemic conditions.