Abstract 214: Tracking of CD16 Monocytes Following Delivery Into the Ischemic Limb - a Bench to Bedside Study

Introduction: The poor retention of cells delivered into ischemic tissue is a hurdle that needs to be addressed for cell therapy to be effective. We have previously shown that CD16+ monocytes expressing upregulated cell adhesion markers are mobilized in critical limb ischemia (CLI) and salvage limbs in pre-clinical studies of hindlimb ischemia (HLI). We hypothesized that these cells are well retained following delivery into ischemic muscle. Methods and Results: CD16+ and CD16- monocytes were isolated from CLI patients, fluorescently labeled with QuantumDots and injected into the adductor muscle of nude athymic mice following HLI (n=15/group). Flow cytometric analysis of cell suspensions from injected muscle showed higher 3 and 7 day retention of CD16+ compared with CD16- monocytes (P7 ) were radiolabeled with Indium 111 and injected into ischemic legs. Cells were tracked at 30mins, 2, 24 and 72 hours using whole-body γ-camera imaging: radiodecay-corrected retention percentages were 60.0, 37.4, 29.9 and 22.0% respectively with evidence of “washout” into the liver. Analysis of muscle biopsies showed >85% viability of the cells at 10 days and areas of increased arteriogenesis compared with remote, non-injected muscle. Conclusion: CD16+ Mo are preferentially retained within ischemic muscle in experimental HLI. This first in man study shows these cells remain viable in ischemic tissue. Isolation of sufficient numbers of these cells for delivery directly into poorly perfused muscle may provide a more effective cell therapy for CLI patients.