Efficacy and Safety of Umbilical Cord Blood Injection for Critical Limb Ischemia

Inclusion Criteria: * Atherosclerotic ischemic peripheral vascular disease or Thromboangiitis Obliterans with Critical Limb Ischemia (Fontaine stages III and IV) * Participant must match either a or b 1. Ankle brachial index (ABI) ≤ 0.7 2. Doppler waveforms at posterior tibial artery and dorsalis pedis artery are monophasic with toe pressure \< 30 mmHg. * A non-surgical candidate for revascularization e.g. prior vascular reconstruction, inability to locate a suitable vein for grafting, diffuse multi- segment disease, or extensive infra-popliteal disease not amenable to a vascular graft. * Age \> 18 years old. * The non-index leg may be treated only in the event and it full fills the same eligibility criteria and exclusion criteria used in this protocol for the treatment leg. * Patients must be on maximal tolerated medical therapy for PVD including A) Cessation of smoking B) Referral to endocrinologist for control of HgA1c to \< 7.0 mg/dl, control of hyperlipidemia with statins or other anti-hyperlipidemic drugs as indicated, control of hypertension as indicated C) Antiplatelet therapy with aspirin and / or cilostazol (unless medically contraindicated, e.g. bleeding or allergy) Exclusion Criteria: * Popliteal vascular entrapment syndrome * Lower extremity infection or infected ulcer * Hypercoagulable state * HIV positive * HBsAg positive * Uncontrolled arrhythmia, that is, persistence of an arrhythmia despite medical therapy * Unstable angina * Thrombocytopenia \< 50,000/ul * Leukemia or myelodysplasia * Allergy to E coli or its products * Patients with metal in their bodies cannot undergo MRIs (MRA). Therefore, patients with, cochlear implants, or aneurysm clips are not eligible. Coronary artery stents are not a contraindication. Patients with pacemakers are still candidates provided they have normal creatinine (\< 1.1 mg/dl) and can receive contrast dye (no allergy) for angiogram instead of MRA. MRI/MRA does not need to be repeated if a prior MRA or Angiogram Demonstrates inoperable disease. * Patients who are pregnant * Poorly controlled diabetes will not be a cause for exclusion but patient must see endocrinologist for better control * Current malignancy, except squamous cell or basal cell skin cancers thought to be easily controlled. * AST, ALT, or bilirubin more than twice the upper limit of normal. * WBC \< 2.5 / ul. * Any patient who is actively bleeding, including blood on urine dipstick or fecal occult blood. * Patient is on chemotherapy or other immuno-suppressive medications such as steroids, cellcept, cyclosporine, cytoxan, azathioprine, rituxan, humira or remicade. * Donor is HLA homozygous and shares that HLA haplotype with the recipient (a different donor will have to be found) * Patients diagnosed with Thromboangiitis Obliterans (Buerger's Disease) who are smokers and are unwilling or unable to quit smoking * A) Patients with a myocardial infarction within the last 30 days or left ventricular ejection fraction \< 35% B) Patients with a history of malignancy in the last 5 years (other than basal cell carcinoma or carcinoma in situ) C) Patients with a CVA within the last 6 months D) Patients with a HbA1c level \> 7.0%