Abstract 3701: CXCR4 Antagonist AMD3100 Preserves Cardiac Function After Ischemia-Reperfusion Injury via eNOS Dependent Mobilization of Bone Marrow Derived Progenitor Cells
Background: The SDF-1α/CXCR4 axis has a pivotal role in stem/progenitor retention in the bone marrow (BM), and the CXCR4 antagonist AMD3100 rapidly mobilizes stem/progenitor cells from the BM. We hypothesized that AMD could enhance cardiac recovery after ischemia-reperfusion (IR) injury via mobilization of BM derived progenitors.
Methods and Results: Wild type (WT) mice were treated with single subcutaneous injections of AMD (5 mg/kg) or saline immediately after IR injury (60 min-LAD occlusion followed by reperfusion). 3 days after IR, histological analyses exhibited reduced the ratio of infarct area/area at risk (AAR) (15.8±2.2% vs. 31.9±9.4, p<0.05). 4 weeks after IR, echocardiography demonstrated better LV function in AMD-treated mice (Day28, LVFS: 38.3±6.1 vs. 28.0±5.0%, p<0.05), and histological analysis showed increased capillary density (188.7±52.5 vs. 113.5±13.4 cells/HPF, p<0.05) and decreased fibrosis (27.6±10.9% vs. 43.3±17.0, p<0.05) in AMD-treated mice. In peripheral blood, circulating EPC levels were increased continuously for 7 days in AMD-treated mice (Day7: 76.0±23.9 vs. 34.6±6.1 cells/uL of PB, p<0.05), but returned to baseline 1 day after IR in saline-treated mice. In BM, AMD upregulated eNOS (Day3: 382±58 vs. 264±37 eNOS+ cells/HPF, p<0.01) and its downstream targets MMP-9 (Day3: 88.6±12.7 vs. 53.9±24.5 ug/mL, p<0.05) and soluble Kit ligand (Day3: 20.4±3.3 vs. 13.0±4.1 pg/mL, p<0.05). To determine whether upregulation of eNOS in BM is essential for the cardioprotective effects of AMD, we induced IR injury in WT mice transplanted with BM from eNOS-KO mice (WT/KOBM) and in eNOS-KO mice transplanted with WT BM (KO/WTBM). The cardioprotective effects of AMD were retained in KO/WTBM mice, but not in WT/KOBM mice. Furthermore, eNOS deficiency in BM did not affect AMD-induced mobilization of CXCR4+ cells into PB, but EPC mobilization was abolished (EPC Day3: KO/WTBM, 65.2±6.7 vs. 39.9±17.4, p<0.05; WT/KOBM, 24.5±8.3 vs. 21.6±15.2 cells/uL of PB, p=NS).
Conclusions: This study provides novel mechanistic insights into the cardioprotective effects of AMD3100 by identifying an unexpected influence of AMD3100 on eNOS expression.