This study is designed to test the use of G-CSF in peripheral vascular disease. The investigators hypothesize that mobilization of angiogenic cells into the blood by granulocyte colony stimulating factor (G-CSF) may stimulate the formation of new blood vessels and result in a sustained improvement in blood flow in patients with severe peripheral arterial disease.

One fourth of patients with peripheral artery disease (PAD) of the lower extremities have severe symptomatic disease and 1-2% have critical limb ischemia (CLI). In patients with CLI, the risk of limb amputation at 1 year is 50%. In addition, patients with CLI often have rest pain, non-healing ulcers and severe limitations of ambulation. Revascularization procedures, including bypass surgery, percutaneous transluminal angioplasty and angioplasty with stenting, are currently the only treatment options. However, many patients are not eligible for a revascularization procedure due to small vessel disease or coexisting medical problems. Moreover, restenosis rates are high.

There is currently no effective non-invasive treatment for critical limb ischemia. We hypothesize that mobilization of angiogenic cells into the blood by granulocyte colony stimulating factor (G-CSF) may stimulate angiogenesis in areas of ischemia and result in a sustained improvement in blood flow in patients with severe PAD.

Inclusion Criteria:

• Patients must have critical limb ischemia secondary to PAD, as defined by the presence of a non-healing ulcer, rest pain, or dry gangrene.
• Patients must have a toe pressure ≤ 30 mm Hg.
• Patients must be ≥18 years old.
• Patient must be able to self-administer a daily subcutaneous injection or have a caregiver who is able to administer a daily subcutaneous injection.
• Patients must be taking or have no absolute contraindication to taking aspirin and clopidogrel. If they are not currently taking aspirin, they must be willing to take aspirin (81 mg daily) and clopidogrel (75 mg daily) for 14 days starting on the first day of G-CSF treatment.
• After being informed of the treatment involved, patients must give written consent. The patient should not have any serious medical or psychiatric illness that would prevent either the giving of informed consent or the receipt of treatment. A built-in period of one week from discussion of the trial and initiation of the trial will be mandatory for enrollment.

Exclusion Criteria:

• Patients with transmetatarsal or higher amputations in the affected limb are excluded.
• Patients who are candidates for a revascularization procedure.