Allogenic endothelial progenitor cells(Allife Medicine)

Main study objectives: To evaluate the safety and tolerability of allogeneic endothelial progenitor cells (EPCs) injection in the treatment of severe lower limb ischemia, and to recommend doses for subsequent clinical studies. Secondary study objectives: 1. To observe the preliminary effectiveness of allogeneic endothelial progenitor cells (EPCs) injection in the treatment of severe lower limb ischemia; 2. To explore the relationship between the dose and clinical efficacy of allogeneic endothelial progenitor cells (EPCs) injection in the treatment of severe lower limb ischemia; 3. To evaluate the pharmacokinetic characteristics of allogeneic endothelial progenitor cells (EPCs) injection in the treatment of severe lower limb ischemia; 4. To evaluate the immunological characteristics of allogeneic endothelial progenitor cells (EPCs) injection in the treatment of severe lower limb ischemia; 5. To explore the pharmacodynamic characteristics of allogeneic endothelial progenitor cells (EPCs) injection in the treatment of severe lower limb ischemia.