Adipose Tissue/cytology; Intermittent Claudication/surgery; Ischemia/surgery; Leg Ulcer/surgery; Lower Extremity/blood supply; Mesenchymal Stem Cell Transplantation; Adult; Aged; Amputation, Surgical; Angiography, Digital Subtraction; Cells, Cultured; Collateral Circulation; Critical Illness; Diabetic Foot/surgery; Exercise Tolerance; Humans; Injections, Intramuscular; Intermittent Claudication/diagnostic imaging; Intermittent Claudication/physiopathology; Ischemia/diagnostic imaging; Ischemia/physiopathology; Leg Ulcer/diagnostic imaging; Leg Ulcer/physiopathology; Limb Salvage; Male; Mesenchymal Stem Cell Transplantation/adverse effects; Middle Aged; Neovascularization, Physiologic; Pilot Projects; Recovery of Function; Regional Blood Flow; Reoperation; Republic of Korea; Time Factors; Treatment Outcome; Walking; Wound Healing; Young Adult