Background Myocardial ischemia causes cardiomyocyte death, adverse ventricular remodeling, and ventricular dysfunction. Endothelial progenitor cells (EPC) have been shown to ameliorate this process, particularly when activated with stromal cell-derived factor-1α (SDF). We hypothesized that implantation of a tissue engineered extracellular matrix scaffold seeded with EPCs primed with SDF could induce neovasculogenesis, prevent adverse remodeling, and preserve ventricular function after myocardial infarction (MI). Methods and Results Lewis rats (n=82) underwent left anterior descending artery ligation to induce MI. EPCs were 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 (LV) wall including the region of ischemia.. At four weeks, when compared to controls, borderzone myocardial tissue demonstrated increased levels of VEGF in the EPCM group. Vessel density as assessed by immunohistochemical microscopy was significantly increased in the EPCM group (4.1 vs 6.2 vessels/high-powered field, p<0.001), and microvascular perfusion measured by lectin microangiography was enhanced four-fold (0.7 vs. 2.7% vessel volume/section volume, p=0.04). Ventricular geometry and scar fraction assessed by analysis of sectioned hearts exhibited significantly preserved LV internal diameter (9.7mm vs. 8.6mm, p=0.005) and decreased infarct scar expressed as percent of total section area (16% vs. 7%, p=0.002) when compared to all other groups. In addition, EPCM animals showed a significant preservation of function as measured by echocardiography, pressure volume-conductance, and Doppler flow. Conclusions Extracellular matrix seeded with EPCs primed with SDF induces borderzone neovasculogenesis, attenuates adverse ventricular remodeling, and preserves ventricular function after MI.

BACKGROUND After ischemic injury, cardiac secretion of the potent endothelial progenitor stem cell (EPC) chemokine SDF stimulates endogenous neovascularization and myocardial repair, a process insufficiently robust to repair major infarcts. Experimentally, exogenous administration of recombinant SDF enhances neovasculogenesis and cardiac function after MI. However, SDF has a short half-life, is bulky, and very expensive. Smaller analogs of SDF may provide translational advantages including enhanced stability and function, ease of synthesis, lower cost, and potential modulated delivery via engineered biomaterials. In this study, computational protein design was used to create a more efficient evolution of the native SDF protein. METHODS and RESULTS Protein structure model was used to engineer an SDF polypeptide analog (ESA) that splices the N-terminus (activation and binding) and C-terminus (extracellular stabilization) with a diproline segment designed to limit the conformational flexibility of the peptide backbone and retain the relative orientation of these segments observed in the native structure of SDF. EPCs in ESA gradient, assayed by Boyden chamber, showed significantly increased migration compared to both SDF and control gradients (ESA 567±74 cells/HPF vs SDF 438±46 p=0.037; vs Control 156±45 p=0.001). EPC receptor activation was evaluated by quantifying phosphorylated AKT. ESA had significantly greater pAKT levels than SDF and control (1.64±0.24 vs 1.26±0.187, p=0.01; vs. 0.95±0.08, p<0.001). Angiogenic growth factor assays revealed a distinct increase in Angiopoietin-1 expression in the ESA and SDF treated hearts. Also, CD-1 mice (n=30) underwent LAD ligation and peri-infarct intramyocardial injection of ESA, SDF-1α, or saline. At 2 weeks, echocardiography demonstrated a significant gain in EF, CO, SV, and Fractional Area Change (FAC) in mice treated with ESA when compared to controls and significant improvement in FAC when compared to SDF treated mice. CONCLUSION When compared to native SDF, a novel engineered SDF polypeptide analog (ESA) more efficiently induces EPC migration and improves post-MI cardiac function, and thus offers a more clinically translatable neovasculogenic therapy.

BACKGROUND Ventricular remodeling after myocardial infarction begins with massive extracellular matrix deposition and resultant fibrosis. This loss of functional tissue and the stiffening of myocardial elastic and contractile elements starts the vicious cycle of mechanical inefficiency, adverse remodeling, and eventual heart failure. We hypothesize that SDF-1α therapy to microrevascularize ischemic myocardium will rescue salvageable peri-infarct tissue and subsequently improve myocardial elasticity. METHODS Immediately following LAD ligation, mice were randomized to receive peri-infarct injection of either saline or SDF. After six weeks, the animals were sacrificed and samples were taken from the peri-infarct borderzone, the infarct scar, and the left ventricle of non-infarcted control mice. Determination of the tissues’ elastic moduli was carried out by mechanical testing in an atomic force microscope. RESULTS SDF treated peri-infarct tissue most closely approximated the elasticity of normal ventricle and was significantly more elastic than saline treated myocardium (109 + 22.9 kPa vs. 295 + 42.3 kPa, p < 0.0001). The myocardial scar, the strength of which depends on matrix deposition from vasculature at the peri-infarct edge, was stiffer in SDF treated animals when compared to controls (804 + 102.2 kPa vs. 144 + 27.5 kPa, p < 0.0001). CONCLUSIONS This study, through direct quantification of myocardial elastic properties, has demonstrated the ability of SDF to re-engineer the evolving myocardial infarct and peri-infarct tissue. By increasing the elasticity of the ischemic and dysfunctional peri-infarct borderzone and bolstering the weak aneurysm prone scar, SDF therapy may confer a mechanical advantage to resist adverse remodeling following infarction.

Objectives Stromal cell-derived factor (SDF)-1α is a potent endogenous endothelial progenitor cell (EPC) chemokine and key angiogenic precursor. Recombinant SDF-1α has been demonstrated to improve neovasculogenesis and cardiac function after myocardial infarction (MI) but SDF-1α is a bulky protein with a short half-life. Small peptide analogs might provide translational advantages, including ease of synthesis, low manufacturing costs, and the potential to control delivery within tissues using engineered biomaterials. We hypothesized that a minimized peptide analog of SDF-1α, designed by splicing the N-terminus (activation and binding) and C-terminus (extracellular stabilization) with a truncated amino acid linker, would induce EPC migration and preserve ventricular function after MI. Methods EPC migration was first determined in vitro using a Boyden chamber assay. For in vivo analysis, male rats (n=48) underwent left anterior descending coronary artery ligation. At infarction, the rats were randomized into 4 groups and received peri-infarct intramyocardial injections of saline, 3 μg/kg of SDF-1α, 3 μg/kg of spliced SDF analog, or 6 μg/kg spliced SDF analog. After 4 weeks, the rats underwent closed chest pressure volume conductance catheter analysis. Results EPCs showed significantly increased migration when placed in both a recombinant SDF-1α and spliced SDF analog gradient. The rats treated with spliced SDF analog at MI demonstrated a significant dose-dependent improvement in end-diastolic pressure, stroke volume, ejection fraction, cardiac output, and stroke work compared with the control rats. Conclusions A spliced peptide analog of SDF-1α containing both the N- and C- termini of the native protein induced EPC migration, improved ventricular function after acute MI, and provided translational advantages compared with recombinant human SDF-1α.

Objective Microvascular malperfusion after myocardial infarction leads to infarct expansion, adverse remodeling, and functional impairment. Native reparative mechanisms exist but are inadequate to vascularize ischemic myocardium. We hypothesized that a 3-dimensional human fibroblast culture (3DFC) functions as a sustained source of angiogenic cytokines, thereby augmenting native angiogenesis and limiting adverse effects of myocardial ischemia. Methods Lewis rats underwent ligation of the left anterior descending coronary artery to induce heart failure; experimental animals received a 3DFC scaffold to the ischemic region. Border-zone tissue was analyzed for the presence of human fibroblast surface protein, vascular endothelial growth factor, and hepatocyte growth factor. Cardiac function was assessed with echocardiography and pressure–volume conductance. Hearts underwent immunohistochemical analysis of angiogenesis by co-localization of platelet endothelial cell adhesion molecule and alpha smooth muscle actin and by digital analysis of ventricular geometry. Microvascular angiography was performed with fluorescein-labeled lectin to assess perfusion. Results Immunoblotting confirmed the presence of human fibroblast surface protein in rats receiving 3DFC, indicating survival of transplanted cells. Increased expression of vascular endothelial growth factor and hepatocyte growth factor in experimental rats confirmed elution by the 3DFC. Microvasculature expressing platelet endothelial cell adhesion molecule/alpha smooth muscle actin was increased in infarct and border-zone regions of rats receiving 3DFC. Microvascular perfusion was also improved in infarct and border-zone regions in these rats. Rats receiving 3DFC had increased wall thickness, smaller infarct area, and smaller infarct fraction. Echocardiography and pressure–volume measurements showed that cardiac function was preserved in these rats. Conclusions Application of a bioengineered 3DFC augments native angiogenesis through delivery of angiogenic cytokines to ischemic myocardium. This yields improved microvascular perfusion, limits infarct progression and adverse remodeling, and improves ventricular function.

Objective: Vancomycin loading doses are recommended; however, the risk of nephrotoxicity with these doses is unknown. The primary objective of this study was to compare nephrotoxicity in emergency department (ED) sepsis patients who received vancomycin at high doses (>20 mg/kg) versus lower doses (≤20 mg/kg).Methods: A retrospective cohort study was performed in three academic EDs. Inclusion criteria were age ≥ 18 years, intravenous vancomycin order, and hospital admission. Exclusion criteria were no documented weight, hemodialysis-dependent, and inadequate serum creatinine (SCr) values for the measured outcome. Analyses compared the incidence of nephrotoxicity for patients who received vancomycin at high dose (>20 mg/kg) versus low dose (≤20 mg/kg).Results: A total of 2,131 consecutive patients prescribed vancomycin over 6 months were identified. Of these, 1,330 patients had three SCr values assessed for the primary outcome. High-dose initial vancomycin was associated with a significantly lower rate of nephrotoxicity (5.8% vs. 11.1%). After age, sex, and initial SCr were adjusted for, the risk of high-dose vancomycin compared to low-dose was decreased for the development of nephrotoxicity (relative risk = 0.60; 95% confidence interval = 0.44 to 0.82).Conclusion: Initial dosing of vancomycin > 20 mg/kg was not associated with an increased rate of nephrotoxicity compared with lower doses. Findings from this study support compliance with initial weight-based vancomycin loading doses.ACADEMIC EMERGENCY MEDICINE 2016;23:744-746

This study evaluates a therapy for infarct modulation and acute myocardial rescue and utilizes a novel technique to measure local myocardial oxygenation in vivo. Bone marrow-derived endothelial progenitor cells (EPCs) were targeted to the heart with peri-infarct intramyocardial injection of the potent EPC chemokine stromal cell-derived factor 1α (SDF). Myocardial oxygen pressure was assessed using a noninvasive, real-time optical technique for measuring oxygen pressures within microvasculature based on the oxygen-dependent quenching of the phosphorescence of Oxyphor G3. Myocardial infarction was induced in male Wistar rats (n = 15) through left anterior descending coronary artery ligation. At the time of infarction, animals were randomized into two groups: saline control (n = 8) and treatment with SDF (n = 7). After 48 h, the animals underwent repeat thoracotomy and 20 μl of the phosphor Oxyphor G3 was injected into three areas (peri-infarct myocardium, myocardial scar, and remote left hindlimb muscle). Measurements of the oxygen distribution within the tissue were then made in vivo by applying the end of a light guide to the beating heart. Compared with controls, animals in the SDF group exhibited a significantly decreased percentage of hypoxic (defined as oxygen pressure ≤ 15.0 Torr) peri-infarct myocardium (9.7 ± 6.7% vs. 21.8 ± 11.9%, P = 0.017). The peak oxygen pressures in the peri-infarct region of the animals in the SDF group were significantly higher than the saline controls (39.5 ± 36.7 vs. 9.2 ± 8.6 Torr, P = 0.02). This strategy for targeting EPCs to vulnerable peri-infarct myocardium via the potent chemokine SDF-1α significantly decreased the degree of hypoxia in peri-infarct myocardium as measured in vivo by phosphorescence quenching. This effect could potentially mitigate the vicious cycle of myocyte death, myocardial fibrosis, progressive ventricular dilatation, and eventual heart failure seen after acute myocardial infarction.

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