A micro-fragmented collagen gel as a cell-assembling platform for critical limb ischemia repair

Critical limb ischemia(CLI)is a devastating disease characterized by the progressive blockage of blood vessels.Although the paracrine effect of growth factors in stem cell therapy made it a promising angiogenic therapy for CLI,poor cell survival in the harsh ischemic microenvironment limited its efficacy.Thus,an imperative need exists for a stem-cell delivery method that enhances cell survival.Here,a collagen microgel(CMG)cell-delivery scaffold(40×20μm)was fabricated via micro-fragmentation from collagen-hyaluronic acid polyionic complex to improve transplantation efficiency.Culturing human adipose-derived stem cells(hASCs)with CMG enabled integrin receptors to interact with CMG to form injectable 3-dimensional constructs(CMG-hASCs)with a microporous microarchitecture and enhanced mass transfer.CMG-hASCs exhibited higher cell survival(p<0.0001)and angiogenic potential in tube formation and aortic ring angiogenesis assays than cell aggregates.Injection of CMG-hASCs intramuscularly into CLI mice increased blood perfusion and limb salvage ratios by 40%and 60%,respectively,compared to cell aggregate-treated mice.Further immunofluorescent analysis revealed that transplanted CMG-hASCs have greater muscle regenerative and angiogenic potential,with enhanced cell survival than cell aggregates(p<0.05).Collectively,we propose CMG as a cell-assembling platform and CMG-hASCs as promising therapeutics to treat CLI.