Stromal Cell-Derived Factor-1 (cid:1) Activation of Tissue-Engineered Endothelial Progenitor Cell Matrix Enhances Ventricular Function After Myocardial Infarction by Inducing Neovasculogenesis

Background —Myocardial ischemia causes cardiomyocyte death, adverse ventricular remodeling, and ventricular dysfunc-tion. Endothelial progenitor cells (EPCs) have been shown to ameliorate this process, particularly when activated with stromal cell-derived factor-1 (cid:1) (SDF), known to be the most potent EPC chemokine. We hypothesized that implantation of a tissue-engineered extracellular matrix (ECM) scaffold seeded with EPCs primed with SDF could induce borderzone neovasculogenesis, prevent adverse geometric remodeling, and preserve ventricular function after myocardial infarction. Methods and Results —Lewis rats (n (cid:1) 82) underwent left anterior descending artery ligation to induce myocardial infarction. EPCs were isolated, characterized, and cultured on a vitronectin/collagen scaffold and primed with SDF to generate the activated EPC matrix (EPCM). EPCM was sutured to the anterolateral left ventricular wall, which included the region of ischemia. Control animals received sutures but no EPCM. Additional groups underwent application of the ECM alone, ECM primed with SDF (ECM (cid:2) SDF), and ECM seeded with EPCs but not primed with SDF (ECM (cid:2) SDF). At 4 weeks, borderzone myocardial tissue demonstrated increased levels of vascular endothelial growth factor in the EPCM group. When compared to controls, Vessel 0.001), microvascular perfusion 0.005) total section 0.002) all of isothiocyanate-conjugated Alexa mouse and Atto CXCR4 (Abcam) at (BD Biosciences). Fluorescence for each Cells were analyzed by a FACSCanto cytometer, and data were analyzed using FloJo Software EPCs were defined as following in the , , , , CXCR4 . Fluorescence-activated cell sorter analysis was performed in triplicate. To assess upregulation of angiogenic growth factors, hearts from a subset of animals (control, n (cid:1) 4; ECM (cid:2) EPC, n (cid:1) 4; EPCM, n (cid:1) 5) were explanted 4 weeks following LAD ligation, and myocardial tissue biopsies were taken from the ischemic borderzone. Samples were homogenized in T-Per Tissue Extraction Reagent (Thermo- Fischer), normalized for total protein content via Quick Start Bradford Protein Assay (Bio-Rad Laboratories), and tested for presence of rat VEGF. Immunoblotting was performed using a mouse monoclonal antibody directed against rat VEGF (1:300; Abcam) and horseradish peroxidase-conjugated sheep anti-mouse IgG ECL secondary antibody (1:100 000; GE Healthcare). Chemi- luminescent SuperSignal West Dura Extended Duration Substrate (Thermo Scientific) was used, and images were captured using a ChemiDoc XRS (cid:2) system (Bio Rad). Assays were performed in triplicate. closed-chest approach via the right carotid artery. Measurements were obtained before and during inferior vena cava occlusion to produce static and dynamic P-V loops under varying load conditions. Data were recorded and analyzed with LabChart version 6 software (AD Instru-ments) and ARIA Pressure Volume Analysis software (Millar Instru- ments, Inc). In addition to P-V conductance catheter analysis, invasive cardiac output measurements were made by placing a Doppler flow probe (Transonics) around the ascending aorta after median sternotomy (control, n (cid:1) 20; EPCM, (cid:1)