ALD-301 for Critical Limb Ischemia, Randomized Trial

Inclusion Criteria: * Patients 18 years of age or greater with atherosclerotic vascular disease that is viewed as not readily amenable to reconstructive surgery and Rutherford Category 4 ischemia (ischemic rest pain) and Rutherford Category 5 ischemia (ulceration or tissue necrosis) and by the judgment of their referring physician are not reasonable candidates for revascularization options of either percutaneous balloon angioplasty or a surgical revascularization. * Objective evidence of severe peripheral arterial disease will include an ankle brachial index (ABI) of less than 0.5, or, in the case of patients who have vessels calcified and thereby "non-compressible" vessels metatarsal pulse volume recording (PVR) that is flat or barely pulsatile in the diseased limb on two consecutive examinations performed at least one week apart. * Patients competent to give informed consent. * No active malignant disease that could involve the bone marrow, or history of treatment of malignant disease that could have damaged the bone marrow. * Before being accepted for the study the patient must be screened for human immunodeficiency virus, hepatitis B virus, hepatitis C virus, human transmissible spongiform encephalopathy, including Creutzfeldt-Jacob Disease, Treponema pallidum, and have a negative standard infectious disease panel including a CMV PCR test. * Patients who are hemodynamically stable. Exclusion Criteria: * Patients with poorly controlled diabetes mellitus (HbA1C \> 8%) * Patients with renal insufficiency (creatinine \> 2.5). * Patients with evidence of infectious disease as determined by e. above or other medical findings. * Pregnant women (women capable of childbearing must have a negative pregnancy test). * Patients with cognitive impairments. * Other comorbid disease that would be expected to result in less than one year life expectancy * Past malignancy or history of chemotherapy or radiation affecting the bone marrow. * History of inflammatory or progressively fibrotic conditions: .e.g., rheumatoid arthritis, systemic lupus erythematosis, vasculitic disorders, idiopathic pulmonary fibrosis, retroperitoneal fibrosis * Infection as evidenced by WBC count of \>15,000 and/or temperature \>38 degrees C. Large area of cellulitis in the afflicted limb that in the opinion of the investigators would require the institution of antibiotics OR evidence of osteomyelitis corroborated by radiographic or scintigraphic examination * Cardiovascular conditions: * Exercise limiting angina ( Canadian Cardiovascular Society Class 3 (Appendix 7); * Congestive heart failure (New York Heart Association class 3 (Appendix 5); * Unstable angina; * Acute ST elevation myocardial infarction (MI) within 1month; * Transient ischemic attack or stroke within 1 month; * Severe valvular disease * Patients with any history of organ transplants;