Abstract 305: Cytokine Response to Concentrated Bone Marrow Aspirate Injections in Patients With Critical Limb Ischemia

Objective: No medical intervention is approved for patients who suffer from critical limb ischemia (CLI) without a surgical revascularization option. Concentrated bone marrow aspirate (cBMA) injections have demonstrated safety and efficacy in increasing 1-year amputation-free survival (AFS) in the phase III multicenter, double blind, randomized controlled MOBILE trial. The response to cBMA injection is described herein. Methods: A murine (IL-2Rγ -/- ) hind-limb ischemia model was employed to assay blood and tissue levels of angiogenic markers after MarrowStim TM derived cBMA injection. Responders to therapy were selected by cutaneous laser Doppler. Animals were sacrificed at various time points post-injection during which blood and distal limb tissue was harvested. 10 patients were enrolled into the MOBILE Continuing Access trial from May to December 2016 and received cBMA injections into the ischemic limb. Blood was collected at days 1, 3, 7, 14, 45, 60, and 90. Endothelial progenitor cells (EPCs) and protein markers of tissue ischemia were assayed by FACS and ELISA respectively. Results: In mice, cBMA produced a marked increase in gross tissue survival, capillary density, and perfusion compared to the control limb despite low engraftment of human cells. There was no inflammatory infiltration at any of the injection sites. Subanalysis of groups that had differing responses demonstrated crucial increases in FGF-2, VEGF, angiopoietin-2, IL-1β, and TNF-α. 7 subjects donated adequate of blood samples for FACS analysis; of this cohort, 5 patients had demonstrable increases in their EPC to non-EPC ratios immediately post-treatment. No statistically significant changes in FGF, VEGF, ANG1/2, PDGF, and GM-CSF was observed in the systemic circulation. Conclusions: cBMA has demonstrated efficacy in increasing 1-year AFS in CLI patients without surgical revascularization options. However, the response to treatment is variable and further studies are required to predict those who would benefit the most from cBMA.