Safety and Preliminary Efficacy of Allogeneic Endothelial Progenitor Cells (EPCs) in Patients With Critical Limb Ischemia

Inclusion Criteria: * CLI patients fulfilling all the following criteria are considered suitable for inclusion in the study. 1. Age is between 18 and 80. 2. Diagnosis of critical limb ischemia, no surgery or interventional therapy, or poor results one month after interventional therapy (no relief of symptoms), Rutherford grade 3, grade 4 or grade 5, while meeting one of the following criteria: 1) severe intermittent claudication; 2) resting pain; 3) ABI≤ 0.60; 3. Within the last month, Digital Subtraction Angiography (DSA), Computed Tomography Arteriography (CTA), Magnetic Resonance Angiography (MRA)，or vascular ultrasound has confirmed that one or more of the arteries (superficial femoral artery, i.e., the femoral artery below the deep femoral artery branch, the popliteal artery, and its following arteries) have a stenosis of ≥70% or occlusion; 4. The degree of skin ulcer is determined according to Wagner, grade less than or equal to 4; 5. Resting pain lasted for more than 2 weeks when signing the informed consent form 6. Eligible patients of childbearing potential (both men and women) if sexually active must agree to use a reliable method of contraception with their partners 7. The subject or agent can understand the basic requirements of the study, provide written informed consent, and follow up according to the trial requirements. Exclusion Criteria: * Any one of the following exclusion criteria is sufficient to disqualify a patient from the study. 1. Subjects who have received other cell therapies previously 2. Subjects who have received or are attending any other unlisted clinical study drug or treatment within 4 weeks prior to the first dose; 3. Stenosis of ≥75% in the main-iliac artery; 4. Subjects whose Feet or lower limb infections are uncontrollable, or other uncontrolled active infections; 5. Patients with diabetic proliferating retinopathy (diabetic retinopathy grade 4 according to the International Clinical Classification Standard for diabetic retinopathy) 6. Acute ischemic disease of the lower limb(s) occurred within the past 2 weeks; 7. presence of uncontrolled hypertension; 8. Any one with cerebral infarction, cerebral hemorrhage, heart failure, unstable angina pectoris, acute myocardial infarction, or severe arrhythmia before enrollment; 9. abnormal Laboratory tests including severe liver, kidney and coagulation disorders, severe anemia etc. 10. Patients with severe respiratory disease and other active lung infections requiring intervention that were not eligible for participation in the study 11. Hepatitis B surface antigen positive, hepatitis C virus antibody positive, syphilis serum antibody positive or HIV antibody positive 12. Patients with malignancy within the 5 years prior to screening (except for cured basal cell skin carcinoma, cervical carcinoma in situ, papillary thyroid carcinoma) 13. Patients with mental illness, cognitive impairment, except those cured of depression; estimated survival of less than 12 months 14. Congenital or acquired immunodeficiency; 15. Subjects with Pregnant or lactating subjects 16. Subjects with known allergy to more than 2 drugs 17. Current or recent history of alcohol or drug abuse 18. Patients not eligible for enrollment as comprehensively assessed by the investigator