Vascular Regenerative Cell Exhaustion in Adults with Peripheral Artery Disease (PAD-VRCE)

Inclusion Criteria: 1. Adults ≥18 and ≤80 years of age who meet either of the following criteria: 1. Clinically significant/symptomatic PAD (defined as symptomatic claudication with and an ankle brachial index of less than 0.85). 2. No history of PAD. 2. Willing and able to provide written informed consent and comply with study procedures. Exclusion Criteria: 1. Unable or unwilling to provide written informed consent or to provide a peripheral blood sample. 2. Any life-threatening disease expected to result in death within two years. 3. Any malignancy not considered cured (except basal cell carcinoma of the skin). An individual is considered cured if there has been no evidence of cancer recurrence for the five years prior to screening. 4. Uncontrolled hypertension. 5. New York Heart Association Class IV heart failure. 6. Active liver disease or liver dysfunction. 7. Active kidney disease or kidney dysfunction. 8. History of hemorrhagic stroke or other major bleeding disorder. 9. White blood cell count of ≥15x10\^9/L. 10. Active infectious disease requiring systemic antibiotic or anti-viral agents. 11. Known acquired immunodeficiency syndrome, such as Human Immunodeficiency Virus. 12. On oral steroid therapy (e.g. prednisone or other corticosteroids) or other immunosuppressive agents (e.g. methotrexate). 13. Treated autoimmune disorders