Characteristics of responders to autologous bone marrow cell therapy for no-option critical limb ischemia.

Background: The present study investigated factors associated with therapeutic benefits after autologous bone marrow cell (BMC) therapy in patients with "no-option" critical limb ischemia (CLI). Methods and results: Sixty-two patients with advanced CLI (Rutherford category 5 or 6) not eligible for revascularization were randomized to treatment with 40 ml of autologous BMCs (SmartPreP2) by local intramuscular (n = 32) or intra-arterial (n = 30) application. The primary endpoint was limb salvage and wound healing at 12 months. Seven patients (11 %) died during the follow-up from reasons unrelated to stem cell therapy. The BMC product of patients with limb salvage and wound healing (33/55) was characterized by a higher CD34⁺ cell count (p = 0.001), as well as a higher number of total bone marrow mononuclear cells (BM-MNCs) (p = 0.032), than that of nonresponders (22/55). Patients with limb salvage and wound healing were younger (p = 0.028), had lower C-reactive protein levels (p = 0.038), and had higher transcutaneous oxygen pressure (tcpO₂) (p = 0.003) before cell application than nonresponders. All patients with major tissue loss at baseline (Rutherford 6 stage of CLI, n = 5) showed progression of limb ischemia and required major limb amputation. In the multiple binary logistic regression model, the number of applied CD34+ cells (p = 0.046) and baseline tcpO2 (p = 0.031) were independent predictors of limb salvage and wound healing. The number of administrated BM-MNCs strongly correlated with decreased peripheral leukocyte count after 6 months in surviving patients with limb salvage (p = 0.0008). Conclusion: Patients who benefited from autologous BMC therapy for "no-option" CLI were treated with high doses of CD34⁺ cells. The absolute number of applied BM-MNCs correlated with the improvement of inflammation. We hypothesize that the therapeutic benefit of cell therapy for peripheral artery disease is the result of synergistic effects mediated by a mixture of active cells with regenerative potential. Patients at the most advanced stage of CLI do not appear to be suitable candidates for cell therapy. Trial registration: The study was approved and registered by the ISRCTN registry. Trial registration: ISRCTN16096154. Registered: 26 July 2016. [ABSTRACT FROM AUTHOR]