Background-After myocardial infarction (MI), bone marrow-derived cells (BMDCs) are found within the myocardium.The mechanisms determining BMDC recruitment to the heart remain unclear. We investigated the role of stromal cell-derived factor-1␣ (SDF-1) in this process. Methods and Results-MI produced in mice by coronary ligation induced SDF-1 mRNA and protein expression in the infarct and border zone and decreased serum SDF-1 levels. By quantitative polymerase chain reaction, 48 hours after intravenous infusion of donor-lineage BMDCs, there were 80.5Ϯ15.6% more BDMCs in infarcted hearts compared with sham-operated controls (PϽ0.01). Administration of AMD3100, which specifically blocks binding of SDF-1 to its endogenous receptor CXCR4, diminished BMDC recruitment after MI by 64.2Ϯ5.5% (PϽ0.05), strongly suggesting a requirement for SDF-1 in BMDC recruitment to the infarcted heart. Forced expression of SDF-1 in the heart by adenoviral gene delivery 48 hours after MI doubled BMDC recruitment over MI alone (PϽ0.001) but did not enhance recruitment in the absence of MI, suggesting that SDF-1 can augment, but is not singularly sufficient for, BDMC recruitment to the heart. Gene expression analysis after MI revealed increased levels of several genes in addition to SDF-1, including those for vascular endothelial growth factor, matrix metalloproteinase-9, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1, which might act in concert with SDF-1 to recruit BMDCs to the injured heart. Conclusion-SDF-1/CXCR4 interactions play a crucial role in the recruitment of BMDCs to the heart after MI and can further increase homing in the presence, but not in the absence,

Selective inhibition of disease-related proteins underpins the majority of successful drug–target interactions. However, development of effective antagonists is often hampered by targets that are not druggable using conventional approaches. Here, we apply engineered zinc-finger protein transcription factors (ZFP TFs) to the endogenous phospholamban (PLN) gene, which encodes a well validated but recalcitrant drug target in heart failure. We show that potent repression of PLN expression can be achieved with specificity that approaches single-gene regulation. Moreover, ZFP-driven repression of PLN increases calcium reuptake kinetics and improves contractile function of cardiac muscle both in vitro and in an animal model of heart failure. These results support the development of the PLN repressor as therapy for heart failure, and provide evidence that delivery of engineered ZFP TFs to native organs can drive therapeutically relevant levels of gene repression in vivo. Given the adaptability of designed ZFPs for binding diverse DNA sequences and the ubiquity of potential targets (promoter proximal DNA), our findings suggest that engineered ZFP repressors represent a powerful tool for the therapeutic inhibition of disease-related genes, therefore, offering the potential for therapeutic intervention in heart failure and other poorly treated human diseases.