Marc S. Penn

Effect of stromal-cell-derived factor 1 on stem-cell homing and tissue regeneration in ischaemic cardiomyopathy

BACKGROUND Myocardial regeneration via stem-cell mobilisation at the time of myocardial infarction is known to occur, although the mechanism for stem-cell homing to infarcted tissue subsequently and whether this approach can be used for treatment of ischaemic cardiomyopathy are unknown. We investigated these issues in a Lewis rat model (ligation of the left anterior descending artery) of ischaemic cardiomyopathy. METHODS We studied the effects of stem-cell mobilisation by use of granulocyte colony-stimulating factor (filgrastim) with or without transplantation of syngeneic cells. Shortening fraction and myocardial strain by tissue doppler imaging were quantified by echocardiography. FINDINGS Stem-cell mobilisation with filgrastim alone did not lead to engraftment of bone-marrow-derived cells. Stromal-cell-derived factor 1 (SDF-1), required for stem-cell homing to bone marrow, was upregulated immediately after myocardial infarction and downregulated within 7 days. 8 weeks after myocardial infarction, transplantation into the peri-infarct zone of syngeneic cardiac fibroblasts stably transfected to express SDF-1 induced homing of CD117-positive stem cells to injured myocardium after filgrastim administration (control vs SDF-1-expressing cardiac fibroblasts mean 7.2 [SD 3.4] vs 33.2 [6.0] cells/mm2, n=4 per group, p<0.02) resulting in greater left-ventricular mass (1.24 [0.29] vs 1.57 [0.27] g) and better cardiac function (shortening fraction 9.2 [4.9] vs 17.2 [4.2]%, n=8 per group, p<0.05). INTERPRETATION These findings show that SDF-1 is sufficient to induce therapeutic stem-cell homing to injured myocardium and suggest a strategy for directed stem-cell engraftment into injured tissues. Our findings also indicate that therapeutic strategies focused on stem-cell mobilisation for regeneration of myocardial tissue must be initiated within days of myocardial infarction unless signalling for stem-cell homing is re-established.

Use of antioxidant vitamins for the prevention of cardiovascular disease: meta-analysis of randomised trials

INTRODUCTION Oxidised LDL is thought to play an important part in the pathogenesis of atherosclerosis. Observational studies have associated alpha tocopherol (vitamin E), beta carotene, or both, with reductions in cardiovascular events, but not clinical trials. We did a meta-analysis to assess the effect of these compounds on long-term cardiovascular mortality and morbidity. METHODS We analysed seven randomised trials of vitamin E treatment and, separately, eight of beta carotene treatment; all trials included 1000 or more patients. The dose range for vitamin E was 50-800 IU, and for beta carotene was 15-50 mg. Follow-up ranged from 1.4 to 12.0 years. FINDINGS The vitamin E trials involved a total of 81788 patients and the beta carotene trials 138113 in the all-cause mortality analyses. Vitamin E did not provide benefit in mortality compared with control treatment (11.3 vs 11.1%, odds ratio 1.02 [95% CI 0.98-1.06] p=0.42) or significantly decrease risk of cardiovascular death (6.0 vs 6.0%, p=0.86) or cerebrovascular accident (3.6 vs 3.5%, p=0.31). Beta carotene led to a small but significant increase in all-cause mortality (7.4 vs 7.0%, 1.07 [1.02-1.11] p=0.003) and with a slight increase in cardiovascular death (3.4 vs 3.1%, 1.1 [1.03-1.17] p=0.003). No significant heterogeneity was noted for any analysis. INTERPRETATION The lack of a salutary effect was seen consistently for various doses of vitamins in diverse populations. Our results, combined with the lack of mechanistic data for efficacy of vitamin E, do not support the routine use of vitamin E.

SDF-1 expression by mesenchymal stem cells results in trophic support of cardiac myocytes after myocardial infarction

Stem cell transplantation at the time of acute myocardial infarction (AMI) improves cardiac function. Whether the improved cardiac function results from regeneration of cardiac myocytes, modulation of remodeling, or preservation of injured tissue through paracrine mechanisms is actively debated. Because no specific stem cell population has been shown to be optimal, we investigated whether the benefit of stem cell transplantation could be attributed to a trophic effect on injured myocardium. Mesenchymal stem cells secrete SDF‐1 and the interaction of SDF‐1 with its receptor, CXCR4, increases survival of progenitor cells. Therefore, we compared the effects of MSC and MSC engineered to overexpress SDF‐1 on cardiac function after AMI. Tail vein infusion of syngeneic MSC and MSC:SDF‐1 1 day after AMI in the Lewis rat led to improved cardiac function by echocardiography by 70.7% and 238.8%, respectively, compared with saline controls 5 wk later. The beneficial effects of MSC and MSC:SDF‐1 transplantation were mediated primarily through preservation, not regeneration of cardiac myocytes within the infarct zone. The direct effect of SDF‐1 on cardiac myocytes was due to the observation that’ between 24 and 48 h after AMI, SDF‐1‐expressing MSC increased cardiac myocyte surviva, vascular density (18.2±4.0 vs. 7.6±2.3 vessels/mm2, P<0.01; SDF‐1:MSC vs. MSC), and cardiac myosin‐positive area (MSC: 49.5%;mSC:SDF‐1: 162.1%) within the infarct zone. There was no evidence of cardiac regeneration by the infused MSC or endogenous cardiac stem cells based on lack of evidence for cardiac myocytes being derived from replicating cells. These results indicate that stem cell transplantation may have significant beneficial effects on injured organ function independent of tissue regeneration and identify SDF‐1:CXCR4 binding as a novel target for myocardial preservation.—Zhang, M., Mal, N., Kiedrowski, M., Chacko, M., Askari, A. T., Popovic, Z. B., Koc, O. N., Penn, M. S. SDF‐1 expression by mesenchymal stem cells results in trophic support of cardiac myocytes after myocardial infarction. FASEB J. 21, 3197–3207 (2007)

Statins Promote Potent Systemic Antioxidant Effects Through Specific Inflammatory Pathways

Background—The pleiotropic actions of hydroxymethylglutaryl CoA reductase inhibitors (statins) include antiinflammatory and antioxidant actions. We recently reported that statins induce reductions in plasma protein levels of nitrotyrosine (NO2Tyr), a modification generated by nitric oxide–derived oxidants. Whether alternative oxidative pathways are suppressed in vivo after statin administration has not yet been reported. Methods and Results—As an extension of our prior study, hypercholesterolemic subjects with no known coronary artery disease were evaluated at baseline and after 12 weeks of atorvastatin therapy (10 mg/d). Plasma levels of protein-bound chlorotyrosine, NO2Tyr, dityrosine, and orthotyrosine, specific molecular fingerprints for distinct oxidative pathways upregulated in atheroma, were determined by mass spectrometry. In parallel, alterations in lipoproteins and C-reactive protein were determined. Statin therapy caused significant reductions in chlorotyrosine, NO2Tyr, and dityrosine (30%, 25%, and 32%, respectively; P <0.02 each) that were similar in magnitude to reductions in total cholesterol and apolipoprotein B-100 (25% and 29%, P <0.001 each). Nonsignificant decreases in orthotyrosine and C-reactive protein levels were observed (9% and 11%, respectively; P >0.10 each). Statin-induced reductions in oxidation markers were independent of decreases in lipids and lipoproteins. Conclusions—Statins promote potent systemic antioxidant effects through suppression of distinct oxidation pathways. The major pathways inhibited include formation of myeloperoxidase-derived and nitric oxide–derived oxidants, species implicated in atherogenesis. The present results suggest potential mechanisms that may contribute to the beneficial actions of statins. They also have important implications for monitoring the antiinflammatory and antioxidant actions of these agents.

Effect of transendocardial delivery of autologous bone marrow mononuclear cells on functional capacity, left ventricular function, and perfusion in chronic heart failure: the FOCUS-CCTRN trial.

CONTEXT Previous studies using autologous bone marrow mononuclear cells (BMCs) in patients with ischemic cardiomyopathy have demonstrated safety and suggested efficacy. OBJECTIVE To determine if administration of BMCs through transendocardial injections improves myocardial perfusion, reduces left ventricular end-systolic volume (LVESV), or enhances maximal oxygen consumption in patients with coronary artery disease or LV dysfunction, and limiting heart failure or angina. DESIGN, SETTING, AND PATIENTS A phase 2 randomized double-blind, placebo-controlled trial of symptomatic patients (New York Heart Association classification II-III or Canadian Cardiovascular Society classification II-IV) with a left ventricular ejection fraction of 45% or less, a perfusion defect by single-photon emission tomography (SPECT), and coronary artery disease not amenable to revascularization who were receiving maximal medical therapy at 5 National Heart, Lung, and Blood Institute-sponsored Cardiovascular Cell Therapy Research Network (CCTRN) sites between April 29, 2009, and April 18, 2011. INTERVENTION Bone marrow aspiration (isolation of BMCs using a standardized automated system performed locally) and transendocardial injection of 100 million BMCs or placebo (ratio of 2 for BMC group to 1 for placebo group). MAIN OUTCOME MEASURES Co-primary end points assessed at 6 months: changes in LVESV assessed by echocardiography, maximal oxygen consumption, and reversibility on SPECT. Phenotypic and functional analyses of the cell product were performed by the CCTRN biorepository core laboratory. RESULTS Of 153 patients who provided consent, a total of 92 (82 men; average age: 63 years) were randomized (n = 61 in BMC group and n = 31 in placebo group). Changes in LVESV index (-0.9 mL/m(2) [95% CI, -6.1 to 4.3]; P = .73), maximal oxygen consumption (1.0 [95% CI, -0.42 to 2.34]; P = .17), and reversible defect (-1.2 [95% CI, -12.50 to 10.12]; P = .84) were not statistically significant. There were no differences found in any of the secondary outcomes, including percent myocardial defect, total defect size, fixed defect size, regional wall motion, and clinical improvement. CONCLUSION Among patients with chronic ischemic heart failure, transendocardial injection of autologous BMCs compared with placebo did not improve LVESV, maximal oxygen consumption, or reversibility on SPECT. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00824005.

Monocyte Chemotactic Protein‐3 Is a Myocardial Mesenchymal Stem Cell Homing Factor

MSCs have received attention for their therapeutic potential in a number of disease states, including bone formation, diabetes, stem cell engraftment after marrow transplantation, graft‐versus‐host disease, and heart failure. Despite this diverse interest, the molecular signals regulating MSC trafficking to sites of injury are unclear. MSCs are known to transiently home to the freshly infarcted myocardium. To identify MSC homing factors, we determined chemokine expression pattern as a function of time after myocardial infarction (MI). We merged these profiles with chemokine receptors expressed on MSCs but not cardiac fibroblasts, which do not home after MI. This analysis identified monocyte chemotactic protein‐3 (MCP‐3) as a potential MSC homing factor. Overexpression of MCP‐3 1 month after MI restored MSC homing to the heart. After serial infusions of MSCs, cardiac function improved in MCP‐3‐expressing hearts (88.7%, p < .001) but not in control hearts (8.6%, p = .47). MSC engraftment was not associated with differentiation into cardiac myocytes. Rather, MSC engraftment appeared to result in recruitment of myofibroblasts and remodeling of the collagen matrix. These data indicate that MCP‐3 is an MSC homing factor; local overexpression of MCP‐3 recruits MSCs to sites of injured tissue and improves cardiac remodeling independent of cardiac myocyte regeneration.

Chronobiological Patterns of Acute Aortic Dissection

Background—Chronobiological rhythms have been shown to influence the occurrence of a variety of cardiovascular disorders. However, the effects of the time of the day, the day of the week, or monthly/seasonal changes on acute aortic dissection (AAD) have not been well studied. Methods and Results—Accordingly, we evaluated 957 patients enrolled in the International Registry of Acute Aortic Dissection (IRAD) between 1996 and 2000 (mean age 62±14 years, type A 61%). A &khgr;2 test for goodness of fit and partial Fourier analysis were used to evaluate nonuniformity and rhythmicity of AAD during circadian, weekly, and monthly periods. A significantly higher frequency of AAD occurred from 6:00 am to 12:00 noon compared with other time periods (12:00 noon to 6:00 pm, 6:00 pm to 12:00 midnight, and 12:00 midnight to 6:00 am;P <0.001 by &khgr;2 test). Fourier analysis showed a highly significant circadian variation (P <0.001) with a peak between 8:00 am and 9:00 am. Although no significant variation was found for the day of the week, the frequency of AAD was significantly higher during winter (P =0.008 versus other seasons by &khgr;2 test). Fourier analysis confirmed this monthly variation with a peak in January (P <0.001). Subgroup analysis identified a significant association for all subgroups with circadian rhythmicity. However, seasonal/monthly variations were observed only among patients aged <70 years, those with type B AAD, and those without hypertension or diabetes. Conclusions—Similar to other cardiovascular conditions, AAD exhibits significant circadian and seasonal/monthly variations. Our findings may have important implications for the prevention of AAD by tailoring treatment strategies to ensure maximal benefits during the vulnerable periods.

Myeloperoxidase and Plasminogen Activator Inhibitor 1 Play a Central Role in Ventricular Remodeling after Myocardial Infarction

Left ventricular (LV) remodeling after myocardial infarction (MI) results in LV dilation, a major cause of congestive heart failure and sudden cardiac death. Ischemic injury and the ensuing inflammatory response participate in LV remodeling, leading to myocardial rupture and LV dilation. Myeloperoxidase (MPO), which accumulates in the infarct zone, is released from neutrophils and monocytes leading to the formation of reactive chlorinating species capable of oxidizing proteins and altering biological function. We studied acute myocardial infarction (AMI) in a chronic coronary artery ligation model in MPO null mice (MPO−/−). MPO−/− demonstrated decreased leukocyte infiltration, significant reduction in LV dilation, and marked preservation of LV function. The mechanism appears to be due to decreased oxidative inactivation of plasminogen activator inhibitor 1 (PAI-1) in the MPO−/−, leading to decreased tissue plasmin activity. MPO and PAI-1 are shown to have a critical role in the LV response immediately after MI, as demonstrated by markedly delayed myocardial rupture in the MPO−/− and accelerated rupture in the PAI-1−/−. These data offer a mechanistic link between inflammation and LV remodeling by demonstrating a heretofore unrecognized role for MPO and PAI-1 in orchestrating the myocardial response to AMI.

Receptor for AGE (RAGE) Mediates Neointimal Formation in Response to Arterial Injury

Background—Receptor for advanced-glycation end products (RAGE) and its ligands AGEs and S100/calgranulins have been implicated in a range of disorders. However, the role of RAGE/ligand interaction in neointimal hyperplasia after vascular injury remains unclear. Methods and Results—We examined the expression of RAGE and its ligands after balloon injury of the carotid artery in both Zucker diabetic and nondiabetic rats. Using a soluble portion of the extracellular domain of RAGE, we determined the effects of suppressing RAGE/ligand interaction on vascular smooth muscle cell (VSMC) proliferation and neointimal formation after arterial injury. We demonstrate a significantly increased accumulation of AGE and immunoreactivities of RAGE and S100/calgranulins in response to balloon injury in diabetic compared with nondiabetic rats. Blockade of RAGE/ligand interaction significantly decreased S100-stimulated VSMC proliferation in vitro and bromodeoxyuridine (BrdU)–labeled proliferating VSMC in vivo, and suppressed neointimal formation and increased luminal area in both Zucker diabetic and nondiabetic rats. Conclusions—These findings indicate that RAGE/ligand interaction plays a key role in neointimal formation after vascular injury irrespective of diabetes status and suggest a novel target to minimize neointimal hyperplasia.

Genetic Enhancement of Stem Cell Engraftment, Survival, and Efficacy

Cell-based therapies for the prevention and treatment of cardiac dysfunction offer the potential to significantly modulate cardiac function and improve outcomes in patients with cardiovascular disease. To date several clinical studies have suggested the potential efficacy of several different stem cell types; however, the benefits seen in clinical trials have been inconsistent and modest. In parallel, preclinical studies have identified key events in the process of cell-based myocardial repair, including stem cell homing, engraftment, survival, paracrine factor release, and differentiation that need to be optimized to maximize cardiac repair and function. The inconsistent and modest benefits seen in clinical trials combined with the preclinical identification of mediators responsible for key events in cell-based cardiac repair offers the potential for cell-based therapy to advance to cell-based gene therapy in an attempt to optimize these key events in the hope of maximizing clinical benefit. Below we discuss potential key events in cardiac repair and the mediators of these events that could be of potential interest for genetic enhancement of stem cell-based cardiac repair.