Stem cell and progenitor cell therapy in peripheral artery disease. A critical appraisal.

Atherosclerotic peripheral artery disease (PAD) is a common manifestation of atherosclerosis. The occlusion of large limb arteries leads to ischaemia with claudication which can progress to critical limb ischaemia (CLI) with pain at rest, and to tissue loss. At present, common therapy for CLI is either surgical or endovascular revascularisation aimed at improving blood flow to the affected extremity. However, major amputation and death are still frequent complications. Exploring new strategies for revascularisation of ischaemic limbs is thus of major importance. Bone marrow (BM)-derived stem and progenitor cells have been identified as a potential new therapeutic option to induce therapeutic angiogenesis. Encouraging results of preclinical studies have rapidly led to several small clinical trials, in which BM-derived mononuclear cells were administered to patients with limb ischaemia. Clinical benefits were reported from these trials including improvement of ankle-brachial index (ABI), transcutaneous partial pressure of oxygen (TcPO2), reduction of pain, and decreased need for amputation. Nonetheless, large randomised, placebo-controlled, double-blind studies are necessary and currently ongoing (BONMOT-CLI, JUVENTUS and NCT00498069). Further research relates to the optimal cell type and dosage, the isolation method, the role of colony-stimulating factors, administration route, and the supportive stimulation of cells with reduced functioning due to advanced PAD. Autologous stem cell therapy for ischaemic peripheral disease seems to be a promising new tool for the treatment of severe limb ischaemia. Preliminary evidence has established its safety, feasibility and effectiveness on several important endpoints. Several large endpoints studies are underway to further consolidate this evidence.