G-CSF/SCF reduces inducible arrhythmias in the infarcted heart potentially via increased connexin43 expression and arteriogenesis

Three-dimensional spatial quantitative analysis of cardiac lymphatics in the mouse heart

OBJECTIVE

Three-dimensional (3D) microscopy and image data analysis are necessary for studying the morphology of cardiac lymphatic vessels (LyVs) and their association with other cell types. We aimed to develop a methodology for 3D multiplexed lightsheet microscopy and highly sensitive and quantitative image analysis to identify pathological remodeling in the 3D morphology of LyVs in young adult mouse hearts with familial hypertrophic cardiomyopathy (HCM).

METHODS

We developed a 3D lightsheet microscopy workflow providing a quick turn-around (as few as 5-6 days), multiplex fluorescence detection, and preservation of LyV structure and epitope markers. Hearts from non-transgenic and transgenic (TG) HCM mice were arrested in diastole, retrograde perfused, immunolabeled, optically cleared, and imaged. We built an image-processing pipeline to quantify LyV morphological parameters at the chamber and branch levels.

RESULTS

Chamber-specific pathological alterations of LyVs were identified, and significant changes were seen in the right atrium (RA). TG hearts had a higher volume percent of ER-TR7+ fibroblasts and reticular fibers. In the RA, we found associations between ER-TR7+ volume percent and both LyV segment density and median diameter.

CONCLUSIONS

This workflow and study enabled multi-scale analysis of pathological changes in cardiac LyVs of young adult mice, inviting ideas for research on LyVs in cardiac disease.

Experimental heart failure models in small animals

Heart failure (HF) is one of the most critical health and economic burdens worldwide, and its prevalence is continuously increasing. HF is a disease that occurs due to a pathological change arising from the function or structure of the heart tissue and usually progresses. Numerous experimental HF models have been created to elucidate the pathophysiological mechanisms that cause HF. An understanding of the pathophysiology of HF is essential for the development of novel efficient therapies. During the past few decades, animal models have provided new insights into the complex pathogenesis of HF. Success in the pathophysiology and treatment of HF has been achieved by using animal models of HF. The development of new in vivo models is critical for evaluating treatments such as gene therapy, mechanical devices, and new surgical approaches. However, each animal model has advantages and limitations, and none of these models is suitable for studying all aspects of HF. Therefore, the researchers have to choose an appropriate experimental model that will fully reflect HF. Despite some limitations, these animal models provided a significant advance in the etiology and pathogenesis of HF. Also, experimental HF models have led to the development of new treatments. In this review, we discussed widely used experimental HF models that continue to provide critical information for HF patients and facilitate the development of new treatment strategies.

Three-dimensional spatial quantitative analysis of cardiac lymphatics in the mouse heart

Objective

3D microscopy and image data analysis are necessary for studying the morphology of cardiac lymphatic vessels (LyVs) and association with other cell types. We aimed to develop a methodology for 3D multiplexed lightsheet microscopy and highly sensitive and quantitative image analysis to identify pathological remodeling in the 3D morphology of LyVs in young adult mouse hearts with familial hypertrophic cardiomyopathy (HCM).

Methods

We developed a 3D lightsheet microscopy workflow providing a quick turn-around (as few as 5-6 days), multiplex fluorescence detection, and preservation of LyV structure and epitope markers. Hearts from non-transgenic (NTG) and transgenic (TG) HCM mice were arrested in diastole, retrograde perfused, immunolabeled, optically cleared, and imaged. We built an image processing pipeline to quantify LyV morphological parameters at the chamber and branch levels.

Results

Chamber-specific pathological alterations of LyVs were identified, but most significantly in the right atrium (RA). TG hearts had a higher volume fraction of ER-TR7 + fibroblasts and reticular fibers. In the RA, we found associations between ER-TR7 + volume fraction and both LyV segment density and median diameter.

Conclusions

This workflow and study enabled multi-scale analysis of pathological changes in cardiac LyVs of young adult mice, inviting ideas for research on LyVs in cardiac disease.

Transmembrane stem cell factor protein therapeutics enhance revascularization in ischemia without mast cell activation

Stem cell factor (SCF) is a cytokine that regulates hematopoiesis and other biological processes. While clinical treatments using SCF would be highly beneficial, these have been limited by toxicity related to mast cell activation. Transmembrane SCF (tmSCF) has differential activity from soluble SCF and has not been explored as a therapeutic agent. We created novel therapeutics using tmSCF embedded in proteoliposomes or lipid nanodiscs. Mouse models of anaphylaxis and ischemia revealed the tmSCF-based therapies did not activate mast cells and improved the revascularization in the ischemic hind limb. Proteoliposomal tmSCF preferentially acted on endothelial cells to induce angiogenesis while tmSCF nanodiscs had greater activity in inducing stem cell mobilization and recruitment to the site of injury. The type of lipid nanocarrier used altered the relative cellular uptake pathways and signaling in a cell type dependent manner. Overall, we found that tmSCF-based therapies can provide therapeutic benefits without off target effects.

Fibroblast-specific IKKβ deficiency ameliorates angiotensin II-induced adverse cardiac remodeling in mice

Cardiac inflammation and fibrosis contribute significantly to hypertension-related adverse cardiac remodeling. IκB kinase β (IKK-β), a central coordinator of inflammation through activation of NF-κB, has been demonstrated as a key molecular link between inflammation and cardiovascular disease. However, the cell-specific contribution of IKK-β signaling toward adverse cardiac remodeling remains elusive. Cardiac fibroblasts are one of the most populous nonmyocyte cell types in the heart that play a key role in mediating cardiac fibrosis and remodeling. To investigate the function of fibroblast IKK-β, we generated inducible fibroblast-specific IKK-β–deficient mice. Here, we report an important role of IKK-β in the regulation of fibroblast functions and cardiac remodeling. Fibroblast-specific IKK-β–deficient male mice were protected from angiotensin II–induced cardiac hypertrophy, fibrosis, and macrophage infiltration. Ablation of fibroblast IKK-β inhibited angiotensin II–stimulated fibroblast proinflammatory and profibrogenic responses, leading to ameliorated cardiac remodeling and improved cardiac function in IKK-β–deficient mice. Findings from this study establish fibroblast IKK-β as a key factor regulating cardiac fibrosis and function in hypertension-related cardiac remodeling.

Evaluation of the Cardioprotective Effect of Granulocyte Colony Stimulating Factor in Patients with Carbon Monoxide Poisoning

BACKGROUND

Carbon monoxide (CO), which is well known as silent killer, has many toxic effects on organs with high rate of metabolism such as heart and brain. CO-induced cardiotoxicity resulted in a wide range of disabilities including electrocardiogram (ECG) abnormalities, elevation in level of cardiac enzymes, arrhythmias, impairment of left ventricular and myocardial infarction (MI). Cardio-protective effects of Granulocyte colony-stimulating factor (G-CSF) on infarcted heart was proved previously in various reports.

OBJECTIVE

In this study, possible effect of G-CSF on cardiac function of patients with moderate to severe acute CO poisoning was investigated.

METHODS

Cardioprotective effects of G-CSF in CO-poisoned patients was evaluated through ECG, Holter monitoring, echocardiography, and biochemical studies. Continuous intravenous infusion of G-CSF (90 μg/kg) and normal saline were administered respectively to treatment and placebo groups.

RESULTS

The results demonstrated that in moderate to severe CO poisoning, myocardial injury is common. ECG changes (e.g., ST-segment and T-wave changes, QTC), cardiac arrhythmias (e.g., heart blocks and ventricular arrhythmias), serum level of Troponin I, left ventricular ejection fraction were determined after G-CSF administration. Frequencies of ST depression, inversion or flatting of T wave and QTC in ECG were significantly reduced after G-CSF treatment. In addition, incidence of cardiac arrhythmias due to CO poisoning were reduced after G-CSF treatment. However, G-CSF did not exert protective effects on TPI level and function of left ventricular in CO-poisoned patients.

CONCLUSION

GCSF could probably reduce CO-induced cardiac ischemia in patients with acute CO poisoning.

CLINICAL TRIAL REGISTRATION

The trial protocol was registered in the Iranian Registry of Clinical Trials (http://www.irct.ir) registry (Irct ID: IRCT201607232083N7).

Granulocyte colony-stimulating factor attenuates myocardial remodeling and ventricular arrhythmia susceptibility via the JAK2-STAT3 pathway in a rabbit model of coronary microembolization

Background

Coronary microembolization (CME) has a poor prognosis, with ventricular arrhythmia being the most serious consequence. Understanding the underlying mechanisms could improve its management. We investigated the effects of granulocyte colony-stimulating factor (G-CSF) on connexin-43 (Cx43) expression and ventricular arrhythmia susceptibility after CME.

Methods

Forty male rabbits were randomized into four groups (n = 10 each): Sham, CME, G-CSF, and AG490 (a JAK2 selective inhibitor). Rabbits in the CME, G-CSF, and AG490 groups underwent left anterior descending (LAD) artery catheterization and CME. Animals in the G-CSF and AG490 groups received intraperitoneal injection of G-CSF and G-CSF + AG490, respectively. The ventricular structure was assessed by echocardiography. Ventricular electrical properties were analyzed using cardiac electrophysiology. The myocardial interstitial collagen content and morphologic characteristics were evaluated using Masson and hematoxylin-eosin staining, respectively.

Results

Western blot and immunohistochemistry were employed to analyze the expressions of Cx43, G-CSF receptor (G-CSFR), JAK2, and STAT3. The ventricular effective refractory period (VERP), VERP dispersion, and inducibility and lethality of ventricular tachycardia/fibrillation were lower in the G-CSF than in the CME group (P < 0.01), indicating less severe myocardial damage and arrhythmias. The G-CSF group showed higher phosphorylated-Cx43 expression (P < 0.01 vs. CME). Those G-CSF-induced changes were reversed by A490, indicating the involvement of JAK2. G-CSFR, phosphorylated-JAK2, and phosphorylated-STAT3 protein levels were higher in the G-CSF group than in the AG490 (P < 0.01) and Sham (P < 0.05) groups.

Conclusion

G-CSF might attenuate myocardial remodeling via JAK2-STAT3 signaling and thereby reduce ventricular arrhythmia susceptibility after CME.

Targeting Endothelin Receptors in a Murine Model of Myocardial Infarction Using a Small Molecular Fluorescent Probe

The endothelin (ET) axis plays a pivotal role in cardiovascular diseases. Enhanced levels of circulating ET-1 have been correlated with an inferior clinical outcome after myocardial infarction (MI) in humans. Thus, the evaluation of endothelin-A receptor (ET_AR) expression over time in the course of myocardial injury and healing may offer valuable information toward the understanding of the ET axis involvement in MI. We developed an approach to track the expression of ET_AR with a customized molecular imaging probe in a murine model of MI. The small molecular probe based on the ET_AR-selective antagonist 3-(1,3-benzodioxol-5-yl)-5-hydroxy-5-(4-methoxyphenyl)-4-[(3,4,5-trimethoxyphenyl)methyl]-2(5H)-furanone (PD156707) was labeled with fluorescent dye, IRDye800cw. Mice undergoing permanent ligation of the left anterior descending artery (LAD) were investigated at day 1, 7, and 21 post surgery after receiving an intravenous injection of the ET_AR probe. Cryosections of explanted hearts were analyzed by cryotome-based CCD, and fluorescence reflectance imaging (FRI) and fluorescence signal intensities (SI) were extracted. Fluorescence-mediated tomography (FMT) imaging was performed to visualize probe distribution in the target region in vivo. An enhanced fluorescence signal intensity in the infarct area was detected in cryoCCD images as early as day 1 after surgery and intensified up to 21 days post MI. FRI was capable of detecting significantly enhanced SI in infarcted regions of hearts 7 days after surgery. In vivo imaging by FMT localized enhanced SI in the apex region of infarcted mouse hearts. We verified the localization of the probe and ET_AR within the infarct area by immunohistochemistry (IHC). In addition, neovascularized areas were found in the affected myocardium by CD31 staining. Our study demonstrates that the applied fluorescent probe is capable of delineating ET_AR expression over time in affected murine myocardium after MI in vivo and ex vivo.

G-CSF for Extensive STEMI

RATIONALE

In the exploratory Phase II STEM-AMI (Stem Cells Mobilization in Acute Myocardial Infarction) trial, we reported that early administration of G-CSF (granulocyte colony-stimulating factor), in patients with anterior ST-segment-elevation myocardial infarction and left ventricular (LV) dysfunction after successful percutaneous coronary intervention, had the potential to significantly attenuate LV adverse remodeling in the long-term.

OBJECTIVE

The STEM-AMI OUTCOME CMR (Stem Cells Mobilization in Acute Myocardial Infarction Outcome Cardiac Magnetic Resonance) Substudy was adequately powered to evaluate, in a population showing LV ejection fraction ≤45% after percutaneous coronary intervention for extensive ST-segment-elevation myocardial infarction, the effects of early administration of G-CSF in terms of LV remodeling and function, infarct size assessed by late gadolinium enhancement, and myocardial strain.

METHODS AND RESULTS

Within the Italian, multicenter, prospective, randomized, Phase III STEM-AMI OUTCOME trial, 161 ST-segment-elevation myocardial infarction patients were enrolled in the CMR Substudy and assigned to standard of care (SOC) plus G-CSF or SOC alone. In 119 patients (61 G-CSF and 58 SOC, respectively), CMR was available at baseline and 6-month follow-up. Paired imaging data were independently analyzed by 2 blinded experts in a core CMR lab. The 2 groups were similar for clinical characteristics, cardiovascular risk factors, and pharmacological treatment, except for a trend towards a larger infarct size and longer symptom-to-balloon time in G-CSF patients. ANCOVA showed that the improvement of LV ejection fraction from baseline to 6 months was 5.1% higher in G-CSF patients versus SOC (P=0.01); concurrently, there was a significant between-group difference of 6.7 mL/m² in the change of indexed LV end-systolic volume in favor of G-CSF group (P=0.02). Indexed late gadolinium enhancement significantly decreased in G-CSF group only (P=0.04). Moreover, over time improvement of global longitudinal strain was 2.4% higher in G-CSF patients versus SOC (P=0.04). Global circumferential strain significantly improved in G-CSF group only (P=0.006).

CONCLUSIONS

Early administration of G-CSF exerted a beneficial effect on top of SOC in patients with LV dysfunction after extensive ST-segment-elevation myocardial infarction in terms of global systolic function, adverse remodeling, scar size, and myocardial strain.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov. Unique identifier: NCT01969890.

Treatment with mononuclear cell populations improves post-infarction cardiac function but does not reduce arrhythmia susceptibility

Background

Clinical and experimental data give evidence that transplantation of stem and progenitor cells in myocardial infarction could be beneficial, although the underlying mechanism has remained elusive. Ventricular tachyarrhythmia is the most frequent and potentially lethal complication of myocardial infarction, but the impact of mono nuclear cells on the incidence of ventricular arrhythmia is still not clear.

Objective

We aimed to characterize the influence of splenic mononuclear cell populations on ventricular arrhythmia after myocardial infarction.

Methods

We assessed electrical vulnerability in vivo in mice with left ventricular cryoinfarction 14 days after injury and intramyocardial injection of specific subpopulations of mononuclear cells (MNCs) (CD11b-positive cells, Sca-1-positive cells, early endothelial progenitor cells (eEPCs)). As positive control group we used embryonic cardiomyocytes (eCMs). Epicardial mapping was performed for analysing conduction velocities in the border zone. Left ventricular function was quantified by echocardiography and left heart catheterization.

Results

In vivo pacing protocols induced ventricular tachycardia (VT) in 30% of non-infarcted mice. In contrast, monomorphic or polymorphic VT could be evoked in 94% of infarcted and vehicle-injected mice (p<0.01). Only transplantation of eCMs prevented post-infarction VT and improved conduction velocities in the border zone in accordance to increased expression of connexin 43. Cryoinfarction resulted in a broad aggravation of left ventricular function. All transplanted cell types augmented left ventricular function to a similar extent.

Conclusions

Transplantation of different MNC populations after myocardial infarction improves left ventricular function similar to effects of eCMs. Prevention of inducible ventricular arrhythmia is only seen after transplantation of eCMs.

Relevance of mouse models of cardiac fibrosis and hypertrophy in cardiac research

Heart disease causing cardiac cell death due to ischemia-reperfusion injury is a major cause of morbidity and mortality in the United States. Coronary heart disease and cardiomyopathies are the major cause for congestive heart failure, and thrombosis of the coronary arteries is the most common cause of myocardial infarction. Cardiac injury is followed by post-injury cardiac remodeling or fibrosis. Cardiac fibrosis is characterized by net accumulation of extracellular matrix proteins in the cardiac interstitium and results in both systolic and diastolic dysfunctions. It has been suggested by both experimental and clinical evidence that fibrotic changes in the heart are reversible. Hence, it is vital to understand the mechanism involved in the initiation, progression, and resolution of cardiac fibrosis to design anti-fibrotic treatment modalities. Animal models are of great importance for cardiovascular research studies. With the developing research field, the choice of selecting an animal model for the proposed research study is crucial for its outcome and translational purpose. Compared to large animal models for cardiac research, the mouse model is preferred by many investigators because of genetic manipulations and easier handling. This critical review is focused to provide insight to young researchers about the various mouse models, advantages and disadvantages, and their use in research pertaining to cardiac fibrosis and hypertrophy.

The Granulocyte-colony stimulating factor has a dual role in neuronal and vascular plasticity

Granulocyte-colony stimulating factor (G-CSF) is a growth factor that has originally been identified several decades ago as a hematopoietic factor required mainly for the generation of neutrophilic granulocytes, and is in clinical use for that. More recently, it has been discovered that G-CSF also plays a role in the brain as a growth factor for neurons and neural stem cells, and as a factor involved in the plasticity of the vasculature. We review and discuss these dual properties in view of the neuroregenerative potential of this growth factor.

First report on an inotropic peptide activating tetrodotoxin-sensitive, "neuronal" sodium currents in the heart

BACKGROUND

New therapeutic approaches to improve cardiac contractility without severe risk would improve the management of acute heart failure. Increasing systolic sodium influx can increase cardiac contractility, but most sodium channel activators have proarrhythmic effects that limit their clinical use. Here, we report the cardiac effects of a novel positive inotropic peptide isolated from the toxin of the Black Judean scorpion that activates neuronal tetrodotoxin-sensitive sodium channels.

METHODS AND RESULTS

All venoms and peptides were isolated from Black Judean Scorpions (Buthotus Hottentotta) caught in the Judean Desert. The full scorpion venom increased left ventricular function in sedated mice in vivo, prolonged ventricular repolarization, and provoked ventricular arrhythmias. An inotropic peptide (BjIP) isolated from the full venom by chromatography increased cardiac contractility but did neither provoke ventricular arrhythmias nor prolong cardiac repolarization. BjIP increased intracellular calcium in ventricular cardiomyocytes and prolonged inactivation of the cardiac sodium current. Low concentrations of tetrodotoxin (200 nmol/L) abolished the effect of BjIP on calcium transients and sodium current. BjIP did not alter the function of Nav1.5, but selectively activated the brain-type sodium channels Nav1.6 or Nav1.3 in cellular electrophysiological recordings obtained from rodent thalamic slices. Nav1.3 (SCN3A) mRNA was detected in human and mouse heart tissue.

CONCLUSIONS

Our pilot experiments suggest that selective activation of tetrodotoxin-sensitive neuronal sodium channels can safely increase cardiac contractility. As such, the peptide described here may become a lead compound for a new class of positive inotropic agents.

Hepatocyte growth factor modification enhances the anti-arrhythmic properties of human bone marrow-derived mesenchymal stem cells

Background/Aims

Chronic myocardial infarction (MI) results in the formation of arrhythmogenic substrates, causing lethal ventricular arrhythmia (VA). We aimed to determine whether mesenchymal stem cells (MSCs) carrying a hepatocyte growth factor (HGF) gene modification (HGF-MSCs) decrease the levels of arrhythmogenic substrates and reduce the susceptibility to developing VA compared with unmodified MSCs and PBS in a swine infarction model.

Methods

The left descending anterior artery was balloon-occluded to establish an MI model. Four weeks later, the randomly grouped pigs were administered MSCs, PBS or HGF-MSCs via thoracotomy. After an additional four weeks, dynamic electrocardiography was performed to assess heart rate variability, and programmed electrical stimulation was conducted to evaluate the risk for VA. Then, the pigs were euthanized for morphometric, immunofluorescence and western blot analyses. Results: The HGF-MSC group displayed the highest vessel density and Cx43 expression levels, and the lowest levels of apoptosis, and tyrosine hydroxylase (TH) and growth associated protein 43 (GAP43) expression. Moreover, the HGF-MSC group exhibited a decrease in the number of sympathetic nerve fibers, substantial decreases in the low frequency and the low-/high- frequency ratio and increases in the root mean square of successive differences (rMSSD) and the percentage of successive normal sinus R-R intervals longer than 50 ms (pNN50), compared with the other two groups. Finally, the HGF-MSC group displayed the lowest susceptibility to developing VA.

Conclusion

HGF-MSCs displayed potent antiarrhythmic effects, reducing the risk for VA.

Granulocyte colony-stimulating factor therapy for stem cell mobilization following anterior wall myocardial infarction: the CAPITAL STEM MI randomized trial

BACKGROUND

Small studies have yielded divergent results for administration of granulocyte colony-stimulating factor (G-CSF) after acute myocardial infarction. Adequately powered studies involving patients with at least moderate left ventricular dysfunction are lacking.

METHODS

Patients with left ventricular ejection fraction less than 45% after anterior-wall myocardial infarction were treated with G-CSF (10 μg/kg daily for 4 days) or placebo. After initial randomization of 86 patients, 41 in the placebo group and 39 in the G-CSF group completed 6-month follow-up and underwent measurement of left ventricular ejection fraction by radionuclide angiography.

RESULTS

Baseline and 6-week mean ejection fraction was similar for the G-CSF and placebo groups: 34.8% (95% confidence interval [CI] 32.6%-37.0%) v. 36.4% (95% CI 33.5%-39.2%) at baseline and 39.8% (95% CI 36.2%-43.4%) v. 43.1% (95% CI 39.2%-47.0%) at 6 weeks. However, G-CSF therapy was associated with a lower ejection fraction at 6 months relative to placebo (40.8% [95% CI 37.4%-44.2%] v. 46.0% [95% CI 42.7%-44.3%]). Both groups had improved left ventricular function, but change in left ventricular ejection fraction was lower in patients treated with G-CSF than in those who received placebo (5.7 [95% CI 3.4-8.1] percentage points v. 9.2 [95% CI 6.3-12.1] percentage points). One or more of a composite of several major adverse cardiac events occurred in 8 patients (19%) within each group, with similar rates of target-vessel revascularization.

INTERPRETATION

In patients with moderate left ventricular dysfunction following anterior-wall infarction, G-CSF therapy was associated with a lower 6-month left ventricular ejection fraction but no increased risk of major adverse cardiac events. Future studies of G-CSF in patients with left ventricular dysfunction should be monitored closely for safety.

TRIAL REGISTRATION

ClinicalTrials.gov, no. NCT00394498.

Rodent models of heart failure: an updated review

Heart failure (HF) is one of the major health and economic burdens worldwide, and its prevalence is continuously increasing. The study of HF requires reliable animal models to study the chronic changes and pharmacologic interventions in myocardial structure and function and to follow its progression toward HF. Indeed, during the past 40 years, basic and translational scientists have used small animal models to understand the pathophysiology of HF and find more efficient ways of preventing and managing patients suffering from congestive HF (CHF). Each species and each animal model has advantages and disadvantages, and the choice of one model over another should take them into account for a good experimental design. The aim of this review is to describe and highlight the advantages and drawbacks of some commonly used HF rodents models, including both non-genetically and genetically engineered models, with a specific subchapter concerning diastolic HF models.

Recovery of pulmonary structure and exercise capacity by treatment with granulocyte-colony stimulating factor (G-CSF) in a mouse model of emphysema

Emphysema is a chronic obstructive pulmonary disease characterized abnormal dilatation of alveolar spaces, which impairs alveolar gas exchange, compromising the physical capacity of a patient due to airflow limitations. Here we tested the effects of G-CSF administration in pulmonary tissue and exercise capacity in emphysematous mice. C57Bl/6 female mice were treated with elastase intratracheally to induce emphysema. Their exercise capacities were evaluated in a treadmill. Lung histological sections were prepared to evaluate mean linear intercept measurement. Emphysematous mice were treated with G-CSF (3 cycles of 200 μg/kg/day for 5 consecutive days, with 7-day intervals) or saline and submitted to a third evaluation 8 weeks after treatment. Values of run distance and linear intercept measurement were expressed as mean ± SD and compared applying a paired t-test. Effects of treatment on these parameters were analyzed applying a Repeated Measures ANOVA, followed by Tukey's post hoc analysis. p < 0.05 was considered statistically significant. Twenty eight days later, animals ran significantly less in a treadmill compared to normal mice (549.7 ± 181.2 m and 821.7 ± 131.3 m, respectively; p < 0.01). Treatment with G-CSF significantly increased the exercise capacity of emphysematous mice (719.6 ± 200.5 m), whereas saline treatment had no effect on distance run (595.8 ± 178.5 m). The PCR cytokines genes analysis did not detect difference between experimental groups. Morphometric analyses in the lung showed that saline-treated mice had a mean linear intercept significantly higher (p < 0.01) when compared to mice treated with G-CSF, which did not significantly differ from that of normal mice. Treatment with G-CSF promoted the recovery of exercise capacity and regeneration of alveolar structural alterations in emphysematous mice.

Early use of granulocyte colony stimulating factor improves survival in a rabbit model of chronic myocardial ischemia

BACKGROUND

Granulocyte colony stimulating factor (G-CSF) improves the survival of animals with myocardial infarction by inducing bone marrow stem cell mobilization and homing to infarcted areas. However, its precise mechanisms and direct effects on the ischemic myocardium remain unclear. In this study we investigated the direct effects and mechanisms of G-CSF in a rabbit model of chronic myocardial ischemia.

METHODS

Myocardial ischemia models were created by partial ligation of the left anterior descending coronary artery in Japanese white male rabbits. Rabbits were subcutaneously injected with 10 μg/kg of G-CSF (G-CSF group) or saline (control group) for 6 days after myocardial ischemia. Direct effects of G-CSF were analyzed by immunohistochemistry and terminal dUTP nick end-labeling (TUNEL).

RESULTS

Rabbits in the G-CSF group exhibited 75% survival compared to 40% in the control group (p<0.05). Immunohistochemistry of the ischemic myocardium showed increased homing of CD34+ cells on day 7 post-surgery and more vessels on day 28 post-surgery by anti-von Willebrand factor staining in the G-CSF group compared with the control group. Furthermore, an increased percentage of CD34+ cells were observed in peripheral blood and upregulation of vascular endothelial growth factor expression in ischemic tissue in the G-CSF group compared with the control group. TUNEL showed that the apoptotic index in the ischemic myocardium decreased in the G-CSF group compared with the control group on day 28 post-surgery.

CONCLUSIONS

In addition to increasing stem cell mobilization and homing to ischemic myocardium, G-CSF treatment after myocardial ischemia improves survival by accelerating neovascularization and reducing apoptosis.

Acute effects of granulocyte colony-stimulating factor on early ventricular arrhythmias after coronary occlusion in rats

Objectives:

To evaluate the acute effects of colony-stimulating factor (G-CSF) on ventricular arrhythmias after coronary occlusion in rats.

Materials and Methods:

Male Wistar rats (10 weeks) received G-CSF (100 μg.kg^-1) or vehicle. Thirty minutes later, animals were infarcted by coronary occlusion under artificial respiration. Electrocardiogram was monitored for 30 min to evaluate ventricular arrhythmias.

Results:

G-CSF treatment reduced the number of premature ventricular beats and the number and duration of ventricular tachycardia. The incidence of ventricular fibrillation was significantly reduced by G-CSF (MI-Cont: 11.2 ± 2.4 vs. MI-GCSF: 5.4 ± 1 events; P < 0.05). However, total duration of ventricular fibrillation was not altered (MI-Cont: 84 ± 16 vs. MI-GCSF: 76 ± 13 sec).

Conclusions:

Acute administration of G-CSF before coronary ligature in rats reduces the incidence of ventricular premature beats and ventricular tachycardia, suggesting a possible direct electrophysiological effect of this cytokine independently of its genomic effects. However, the data suggest that G-CSF treatment may affect the spontaneous recovery from ventricular fibrillation. Acute G-CSF administration acts directly on cardiac electrophysiology, different from chronic treatment.

Stem cell factor gene transfer promotes cardiac repair after myocardial infarction via in situ recruitment and expansion of c-kit+ cells

RATIONALE

There is growing evidence that the myocardium responds to injury by recruiting c-kit(+) cardiac progenitor cells to the damage tissue. Even though the ability of exogenously introducing c-kit(+) cells to injured myocardium has been established, the capability of recruiting these cells through modulation of local signaling pathways by gene transfer has not been tested.

OBJECTIVE

To determine whether stem cell factor gene transfer mediates cardiac regeneration in a rat myocardial infarction model, through survival and recruitment of c-kit(+) progenitors and cell-cycle activation in cardiomyocytes, and explore the mechanisms involved.

METHODS AND RESULTS

Infarct size, cardiac function, cardiac progenitor cells recruitment, fibrosis, and cardiomyocyte cell-cycle activation were measured at different time points in controls (n=10) and upon stem cell factor gene transfer (n=13) after myocardial infarction. We found a regenerative response because of stem cell factor overexpression characterized by an enhancement in cardiac hemodynamic function: an improvement in survival; a reduction in fibrosis, infarct size and apoptosis; an increase in cardiac c-kit(+) progenitor cells recruitment to the injured area; an increase in cardiomyocyte cell-cycle activation; and Wnt/β-catenin pathway induction.

CONCLUSIONS

Stem cell factor gene transfer induces c-kit(+) stem/progenitor cell expansion in situ and cardiomyocyte proliferation, which may represent a new therapeutic strategy to reverse adverse remodeling after myocardial infarction.

Ventricular HCN channels decrease the repolarization reserve in the hypertrophic heart

AIMS

Cardiac hypertrophy is accompanied by reprogramming of gene expression, where the altered expression of ion channels decreases electrical stability and increases the risk of life-threatening arrhythmias. However, the underlying mechanisms are not fully understood. Here, we analysed the role of the depolarizing current I(f) which has been hypothesized to contribute to arrhythmogenesis in the hypertrophied ventricle.

METHODS AND RESULTS

We used transverse aortic constriction in mice to induce ventricular hypertrophy. This resulted in an increased number of I(f) positive ventricular myocytes as well as a strongly enhanced and accelerated I(f) when compared with controls. Of the four HCN (hyperpolarization-activated cyclic nucleotide-gated channels) isoforms mediating I(f), HCN2 and HCN4 were the predominantly expressed subunits in healthy as well as hypertrophied hearts. Unexpectedly, only the HCN1 transcript was significantly upregulated in response to hypertrophy. However, the combined deletion of HCN2 and HCN4 disrupted ventricular I(f) completely. The lack of I(f) in hypertrophic double-knockouts resulted in a strong attenuation of pro-arrhythmogenic parameters characteristically observed in hypertrophic hearts. In particular, prolongation of the action potential was significantly decreased and lengthening of the QT interval was reduced.

CONCLUSIONS

We suggest that the strongly increased HCN channel activity in hypertrophied myocytes prolongs the repolarization of the ventricular action potential and thereby may increase the arrhythmogenic potential. Our results provide for the first time a direct link between an upregulation of ventricular I(f) and a diminished repolarization reserve in cardiac hypertrophy.

Popeye domain containing proteins are essential for stress-mediated modulation of cardiac pacemaking in mice

Cardiac pacemaker cells create rhythmic pulses that control heart rate; pacemaker dysfunction is a prevalent disorder in the elderly, but little is known about the underlying molecular causes. Popeye domain containing (Popdc) genes encode membrane proteins with high expression levels in cardiac myocytes and specifically in the cardiac pacemaking and conduction system. Here, we report the phenotypic analysis of mice deficient in Popdc1 or Popdc2. ECG analysis revealed severe sinus node dysfunction when freely roaming mutant animals were subjected to physical or mental stress. In both mutants, bradyarrhythmia developed in an age-dependent manner. Furthermore, we found that the conserved Popeye domain functioned as a high-affinity cAMP-binding site. Popdc proteins interacted with the potassium channel TREK-1, which led to increased cell surface expression and enhanced current density, both of which were negatively modulated by cAMP. These data indicate that Popdc proteins have an important regulatory function in heart rate dynamics that is mediated, at least in part, through cAMP binding. Mice with mutant Popdc1 and Popdc2 alleles are therefore useful models for the dissection of the mechanisms causing pacemaker dysfunction and could aid in the development of strategies for therapeutic intervention.

Proarrhythmia in a non-failing murine model of cardiac-specific Na+/Ca 2+ exchanger overexpression: whole heart and cellular mechanisms

The cardiac Na(+)/Ca(2+) exchanger (NCX) generates an inward electrical current during SR-Ca(2+) release, thus possibly promoting afterdepolarizations of the action potential (AP). We used transgenic mice 12.5 weeks or younger with cardiomyocyte-directed overexpression of NCX (NCX-Tg) to study the proarrhythmic potential and mechanisms of enhanced NCX activity. NCX-Tg exhibited normal echocardiographic left ventricular function and heart/body weight ratio, while the QT interval was prolonged in surface ECG recordings. Langendorff-perfused NCX-Tg, but not wild-type (WT) hearts, developed ventricular tachycardia. APs and ionic currents were measured in isolated cardiomyocytes. Cell capacitance was unaltered between groups. APs were prolonged in NCX-Tg versus WT myocytes along with voltage-activated K(+) currents (K(v)) not being reduced but even increased in amplitude. During abrupt changes in pacing cycle length, early afterdepolarizations (EADs) were frequently recorded in NCX-Tg but not in WT myocytes. Next to EADs, delayed afterdepolarizations (DAD) triggering spontaneous APs (sAPs) occurred in NCX-Tg but not in WT myocytes. To test whether sAPs were associated with spontaneous Ca(2+) release (sCR), Ca(2+) transients were recorded. Despite the absence of sAPs in WT, sCR was observed in myocytes of both genotypes suggesting a facilitated translation of sCR into DADs in NCX-Tg. Moreover, sCR was more frequent in NCX-Tg as compared to WT. Myocardial protein levels of Ca(2+)-handling proteins were not different between groups except the ryanodine receptor (RyR), which was increased in NCX-Tg versus WT. We conclude that NCX overexpression is proarrhythmic in a non-failing environment even in the absence of reduced K(V). The underlying mechanisms are: (1) occurrence of EADs due to delayed repolarization; (2) facilitated translation from sCR into DADs; (3) proneness to sCR possibly caused by altered Ca(2+) handling and/or increased RyR expression.

G-CSF therapy reduces myocardial repolarization reserve in the presence of increased arteriogenesis, angiogenesis and connexin 43 expression in an experimental model of pacing-induced heart failure

G-CSF (granulocyte colony-stimulating factor) treatment has been shown to cause beneficial effects including a reduction of inducible arrhythmias in rodent models of ischemic cardiomyopathy. The aim of the present study was to test whether these effects do also apply to pacing-induced non-ischemic heart failure. In 24 female rabbits, heart failure was induced by rapid ventricular pacing. 24 rabbits were sham operated. The paced rabbits developed a significant decrease of ejection fraction. 11 heart failure rabbits (CHF) and 11 sham-operated (S) rabbits served as controls, whereas 13 sham (S-G-CSF) and 13 heart failure rabbits (CHF-G-CSF) were treated with 10 μg/kg G-CSF s.c. over 17 ± 4 days. G-CSF treatment caused a ~25% increased arterial and capillary density and a ~60% increased connexin 43 expression in failing hearts. In isolated, Langendorff-perfused rabbit hearts eight monophasic action potential recordings showed prolongation of repolarization in CHF as compared with controls in the presence of the QT prolonging agent erythromycin (+33 ± 12 ms; p < 0.01). Moreover, a significant increase in dispersion of repolarization contributed to a significantly higher rate of ventricular tachyarrhythmias in CHF. G-CSF-pre-treated hearts showed a further increase in prolongation of repolarization as compared with S and CHF. The further increase in dispersion of repolarization [S-G-CSF: +23 ± 9 ms (spatial), +13 ± 7 ms (temporal); CHF-G-CSF: +38 ± 14 ms (spatial), +10 ± 4 ms (temporal); p < 0.05 as compared with S and CHF], increased the incidence of ventricular tachyarrhythmias. In summary, chronic G-CSF treatment has moderate beneficial effects on parameters potentially related to hemodynamic function in the non-ischemic rabbit CHF model. However, a significant reduction of repolarization reserve might seriously challenge its suitability as a therapeutic agent for chronic CHF therapy.

Acute inhibition of the Na(+)/Ca(2+) exchanger reduces proarrhythmia in an experimental model of chronic heart failure

BACKGROUND

Molecular remodeling in heart failure includes slowing of repolarization, leading to proarrhythmia.

OBJECTIVE

To evaluate the effects of Na(+)/Ca(2+) exchanger (NCX) inhibition on repolarization as a novel antiarrhythmic concept in chronic heart failure (CHF).

METHODS AND RESULTS

CHF was induced by rapid ventricular pacing in rabbits. Left ventricular function was assessed by echocardiography. Monophasic action potentials (MAPs) showed a prolongation of repolarization in CHF after atrioventricular block and stimulation at different cycle lengths. Sotalol (100 μM, n = 13) or veratridine (0.5 μM; n = 15) resulted in a further significant increase in the MAP duration. CHF was associated with an increased dispersion of repolarization, as compared with sotalol-treated (+22 ± 7 ms; P < .05) and veratridine-treated (+20 ± 6 ms; P < .05) sham hearts. In the presence of a low potassium concentration, sotalol and veratridine reproducibly induced early afterdepolarizations (EADs) and polymorphic ventricular tachyarrhythmias (VTs). SEA0400 (1 μM), a pharmacological inhibitor of NCX, significantly shortened the MAP duration (P < .01) and reduced dispersion (P < .05). It suppressed EAD in 6 of 13 sotalol-treated failing hearts and in 9 of 10 veratridine-treated failing hearts, leading to a reduction in VT (60% in sotalol-treated failing hearts and 83% in veratridine-treated failing hearts). Simulations using a mathematical model showed a reduction in the action potential duration and the number of EADs by the NCX block in all subgroups.

CONCLUSIONS

In an experimental model of CHF, the acute inhibition of NCX (1) reduces the MAP duration, (2) decreases dispersion of repolarization, and (3) suppresses EAD and VT. Our observations indicate for the first time that pharmacological NCX inhibition increases repolarization reserve and protects against VTs in heart failure.

Load-reducing therapy prevents development of arrhythmogenic right ventricular cardiomyopathy in plakoglobin-deficient mice

OBJECTIVES

We used a murine model of arrhythmogenic right ventricular cardiomyopathy (ARVC) to test whether reducing ventricular load prevents or slows development of this cardiomyopathy.

BACKGROUND

At present, no therapy exists to slow progression of ARVC. Genetically conferred dysfunction of the mechanical cell-cell connections, often associated with reduced expression of plakoglobin, is thought to cause ARVC.

METHODS

Littermate pairs of heterozygous plakoglobin-deficient mice (plako(+/-)) and wild-type (WT) littermates underwent 7 weeks of endurance training (daily swimming). Mice were randomized to blinded load-reducing therapy (furosemide and nitrates) or placebo.

RESULTS

Therapy prevented training-induced right ventricular (RV) enlargement in plako(+/-) mice (RV volume: untreated plako(+/-) 136 ± 5 μl; treated plako(+/-) 78 ± 5 μl; WT 81 ± 5 μl; p < 0.01 for untreated vs. WT and untreated vs. treated; mean ± SEM). In isolated, Langendorff-perfused hearts, ventricular tachycardias (VTs) were more often induced in untreated plako(+/-) hearts (15 of 25), than in treated plako(+/-) hearts (5 of 19) or in WT hearts (6 of 21, both p < 0.05). Epicardial mapping of the RV identified macro-re-entry as the mechanism of ventricular tachycardia. The RV longitudinal conduction velocity was reduced in untreated but not in treated plako(+/-) mice (p < 0.01 for untreated vs. WT and untreated vs. treated). Myocardial concentration of phosphorylated connexin43 was lower in plako(+/-) hearts with VTs compared with hearts without VTs and was reduced in untreated plako(+/-) compared with WT (both p < 0.05). Plako(+/-) hearts showed reduced myocardial plakoglobin concentration, whereas β-catenin and N-cadherin concentration was not changed.

CONCLUSIONS

Load-reducing therapy prevents training-induced development of ARVC in plako(+/-) mice.

Hematopoietic cytokines for cardiac repair: mobilization of bone marrow cells and beyond

Hematopoietic cytokines, traditionally known to influence cellular proliferation, differentiation, maturation, and lineage commitment in the bone marrow, include granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor, stem cell factor, Flt-3 ligand, and erythropoietin among others. Emerging evidence suggests that these cytokines also exert multifarious biological effects on diverse nonhematopoietic organs and tissues. Although the precise mechanisms remain unclear, numerous studies in animal models of myocardial infarction (MI) and heart failure indicate that hematopoietic cytokines confer potent cardiovascular benefits, possibly through mobilization and subsequent homing of bone marrow-derived cells into the infarcted heart with consequent induction of myocardial repair involving multifarious mechanisms. In addition, these cytokines are also known to exert direct cytoprotective effects. However, results from small-scale clinical trials of G-CSF therapy as a single agent after acute MI have been discordant and largely disappointing. It is likely that cardiac repair following cytokine therapy depends on a number of known and unknown variables, and further experimental and clinical studies are certainly warranted to accurately determine the true therapeutic potential of such therapy. In this review, we discuss the biological features of several key hematopoietic cytokines and present the basic and clinical evidence pertaining to cardiac repair with hematopoietic cytokine therapy.

Granulocyte colony-stimulating factor stabilizes cardiac electrophysiology and decreases infarct size during cardiac ischaemic/reperfusion in swine

AIM

Effects of granulocyte colony-stimulating factor (G-CSF) on cardiac electrophysiology during ischaemic/reperfusion (I/R) period are unclear. We hypothesized that G-CSF stabilizes cardiac electrophysiology during I/R injury by prolonging the effective refractory period (ERP), increasing the ventricular fibrillation threshold (VFT) and decreasing the defibrillation threshold (DFT), and that the cardioprotection of G-CSF is via preventing cardiac mitochondrial dysfunction.

METHODS

In intact-heart protocol, pigs were infused with either G-CSF or vehicle (n = 7 each group) without I/R induction. In I/R protocol, pigs were infused with G-CSF (0.33 μg kg(-1 ) min(-1) ) or vehicle (n = 8 each group) for 30 min prior to a 45-min left anterior descending artery occlusion and at reperfusion. Diastolic pacing threshold (DPT), ERP, VFT and DFT were determined in all pigs before and during I/R period. Rat's isolated cardiac mitochondria were used to test the protective effect of G-CSF (100 nm) in H(2) O(2) -induced mitochondrial oxidative damage.

RESULTS

Neither G-CSF nor vehicle altered any parameter in intact-heart pigs. During ischaemic period, G-CSF significantly increased the DPT, ERP and VFT without altering the DFT. During reperfusion, G-CSF continued to increase the DPT without altering other parameters. The infarct size was significantly decreased in the G-CSF group, compared to the vehicle. G-CSF could also prevent cardiac mitochondrial swelling, decrease ROS production, and prevent mitochondrial membrane depolarization.

CONCLUSION

G-CSF increases the DPT, ERP and VFT and reduces the infarct size, thus stabilizing the myocardial electrophysiology, and preventing fatal arrhythmia during I/R. The protective mechanism could be via its effect in preventing cardiac mitochondrial dysfunction.

Growth factor-induced mobilization of cardiac progenitor cells reduces the risk of arrhythmias, in a rat model of chronic myocardial infarction

Heart repair by stem cell treatment may involve life-threatening arrhythmias. Cardiac progenitor cells (CPCs) appear best suited for reconstituting lost myocardium without posing arrhythmic risks, being commissioned towards cardiac phenotype. In this study we tested the hypothesis that mobilization of CPCs through locally delivered Hepatocyte Growth Factor and Insulin-Like Growth Factor-1 to heal chronic myocardial infarction (MI), lowers the proneness to arrhythmias. We used 133 adult male Wistar rats either with one-month old MI and treated with growth factors (GFs, n = 60) or vehicle (V, n = 55), or sham operated (n = 18). In selected groups of animals, prior to and two weeks after GF/V delivery, we evaluated stress-induced ventricular arrhythmias by telemetry-ECG, cardiac mechanics by echocardiography, and ventricular excitability, conduction velocity and refractoriness by epicardial multiple-lead recording. Invasive hemodynamic measurements were performed before sacrifice and eventually the hearts were subjected to anatomical, morphometric, immunohistochemical, and molecular biology analyses. When compared with untreated MI, GFs decreased stress-induced arrhythmias and concurrently prolonged the effective refractory period (ERP) without affecting neither the duration of ventricular repolarization, as suggested by measurements of QTc interval and mRNA levels for K-channel α-subunits Kv4.2 and Kv4.3, nor the dispersion of refractoriness. Further, markers of cardiomyocyte reactive hypertrophy, including mRNA levels for K-channel α-subunit Kv1.4 and β-subunit KChIP2, interstitial fibrosis and negative structural remodeling were significantly reduced in peri-infarcted/remote ventricular myocardium. Finally, analyses of BrdU incorporation and distribution of connexin43 and N-cadherin indicated that cytokines generated new vessels and electromechanically-connected myocytes and abolished the correlation of infarct size with deterioration of mechanical function. In conclusion, local injection of GFs ameliorates electromechanical competence in chronic MI. Reduced arrhythmogenesis is attributable to prolongation of ERP resulting from improved intercellular coupling via increased expression of connexin43, and attenuation of unfavorable remodeling.

Control of autocrine and paracrine myocardial signals: an emerging therapeutic strategy in heart failure

A growing body of evidence supports the hypothesis that autocrine and paracrine mechanisms, mediated by factors released by the resident cardiac cells, could play an essential role in the reparative process of the failing heart. Such signals may influence the function of cardiac stem cells via several mechanisms, among which the most extensively studied are cardiomyocyte survival and angiogenesis. Moreover, besides promoting cytoprotection and angiogenesis, paracrine factors released by resident cardiac cells may alter cardiac metabolism and extracellular matrix turnover, resulting in more favorable post-injury remodeling. It is reasonable to believe that critical intracellular signals are activated and modulated in a temporal and spatial manner exerting different effects, overall depending on the microenvironment changes present in the failing myocardium. The recent demonstration that chemically, mechanically or genetically activated cardiac cells may release peptides to protect tissue against ischemic injury provides a potential route to achieve the delivery of specific proteins produced by these cells for innovative pharmacological regenerative therapy of the heart. It is important to keep in mind that therapies currently used to treat heart failure (HF) and leading to improvement of cardiac function fail to induce tissue repair/regeneration. As a matter of facts, if specific autocrine/paracrine cell-derived factors that improve cardiac function will be identified, pharmacological-based therapy might be more easily translated into clinical benefits than cell-based therapy. This review will focus on the recent development of potential pharmacologic targets to promote and drive at molecular level the cardiac repair/regeneration in HF.

Rebuilding the damaged heart: the potential of cytokines and growth factors in the treatment of ischemic heart disease

Cytokine therapy promises to provide a noninvasive treatment option for ischemic heart disease. Cytokines are thought to influence angiogenesis directly via effects on endothelial cells or indirectly through progenitor cell-based mechanisms or by activating the expression of other angiogenic agents. Several cytokines mobilize progenitor cells from the bone marrow or are involved in the homing of mobilized cells to ischemic tissue. The recruited cells contribute to myocardial regeneration both as a structural component of the regenerating tissue and by secreting angiogenic or antiapoptotic factors, including cytokines. To date, randomized, controlled clinical trials have not reproduced the efficacy observed in pre-clinical and small-scale clinical investigations. Nevertheless, the list of promising cytokines continues to grow, and combinations of cytokines, with or without concurrent progenitor cell therapy, warrant further investigation.

Most purported antibodies to the human granulocyte colony-stimulating factor receptor are not specific

OBJECTIVE

Antibodies to human granulocyte colony-stimulating factor receptor (HuG-CSFR) are widely available and have been used in numerous studies to evaluate the expression of this protein on normal and malignant cells of hematopoietic and nonhematopoietic origin. Spurred by recent studies that demonstrated that two commonly used antibodies against the erythropoietin and thrombopoietin receptors can in fact bind to completely unrelated and more broadly expressed proteins, we screened 27 commercially available monoclonal and polyclonal antibodies with claimed specificity to HuG-CSFR to determine if they are specific to this receptor.

MATERIALS AND METHODS

Antibodies were evaluated by Western blotting, flow cytometry, and immunohistochemistry using 293T cells engineered to overexpress HuG-CSFR protein, immortalized human hematopoietic cell lines expressing endogenous G-CSFR, and purified human neutrophils.

RESULTS

Only two monoclonal antibodies and one polyclonal antibody could be employed using defined Western blotting or flow cytometry protocols to detect G-CSFR protein in cell lysates or on the surface of cells that express G-CSFR messenger RNA with no binding to cells that did not express the gene. None of the antibodies were suitable for immunohistochemistry. Competitive inhibition with soluble G-CSFR extracellular domain and small inhibitory RNA-mediated knock-down of G-CSFR messenger RNA further demonstrated the limited specificity of these antibodies for HuG-CSFR expressed on the cell surface.

CONCLUSIONS

Most commercially available anti-HuG-CSFR antibodies do not bind specifically to this protein. These studies highlight the need for investigators to validate antibodies in their own systems to avoid the inadvertent use of nonspecifically binding antibodies that could lead, as exemplified in this case with a hematopoietic growth factor receptor, to erroneous conclusions about protein expression.

Mesenchymal stem cell injection ameliorates the inducibility of ventricular arrhythmias after myocardial infarction in rats

BACKGROUND

Mesenchymal stem cell transplantation is a promising new therapy to improve cardiac function after myocardial infarction (MI). The electrophysiological consequences of MSC implantation has not been systematically studied.

METHODS

We investigated the electrophysiological and arrhythmogenic effects of mesenchymal stem cells (MSCs) therapy in experimental infarction model. Rats were subjected to MI operation by LAD ligation and randomly allocated to receive intramyocardially injection PBS (MI-PBS) or 5 × 10(5) EGFP labeled MSCs (MI-MSCs). Electrophysiological study, histological examination, and western blotting were performed 2 weeks after cell transplantation.

RESULTS

Programmed electrical stimulation (PES) showed a significant reduced inducible ventricular tachycardias (VTs), raised ventricular fibrillation threshold (VFT) and prolonged ventricular effective refractory period (VERP) in MSC-treated rats compared to PBS-treated animals. MSC implantation led to markedly longer action potential duration (APD) and shorter activation time (AT) in infarcted border zone (IBZ) of left ventricular epicardium compared with PBS-treated hearts. Histological study revealed that fibrotic area and collagen deposition in infarcted region were significantly lower in MI-MSC group than in MI-PBS group. Abnormal alterations of Connexin 43 including reduction and lateralization were significantly attenuated by MSC treatment.

CONCLUSIONS

This study provide strong evidence that MSC implantation ameliorates interstitial fibrosis and the remodeling of gap junction, attenuates focal heterogeneity of reporlarization and conduction and reduces vulnerability to VTs. The results suggest that MSC transplantation might emerge as a new preventive strategy against VAs besides improving cardiac performance in ischemic heart disease.

Effect of pravastatin on ventricular arrhythmias in infarcted rats: role of connexin43

Epidemiologic studies showed that men treated with statins appear to have a lower incidence of sudden death than men without statins. However, the specific factor for this remained disappointingly elusive. We assessed whether pravastatin enhanced connexin43 expression after myocardial infarction through attenuation of endothelin-1. Twenty-four hours after ligation of the anterior descending artery, male Wistar rats were randomized to vehicle, pravastatin, mevalonate, bosentan, or a combination of pravastatin and mevalonate or pravastatin and bosentan for 4 wk. Myocardial endothelin-1 levels were significantly elevated in vehicle-treated rats at the border zone compared with sham-operated rats. Myocardial connexin43 expression at the border zone was significantly decreased in vehicle-treated infarcted rats compared with sham-operated rats. Attenuated connexin43 expression was blunted after administration of pravastatin, as assessed by immunofluorescence analysis, Western blotting, and real-time quantitative RT-PCR of connexin43. Bosentan enhanced connexin43 amount in infarcted rats and did not have additional beneficial effects on pravastatin-treated rats. Arrhythmic scores during programmed stimulation in vehicle-treated rats were significantly higher than scores in those treated with pravastatin. In contrast, the beneficial effects of pravastatin-induced connexin43 were abolished by the addition of mevalonate and a protein kinase C inducer. In addition, the amount of connexin43 showed significant increase after addition of bisindolylmaleimide, implicating that protein kinase C is a relevant target in endothelin-1-mediated connexin43 expression. Thus chronic use of pravastatin after infarction, resulting in enhanced connexin43 amount by attenuation of mevalonate-dependent endothelin-1 through a protein kinase C-dependent pathway, may attenuate the arrhythmogenic response to programmed electrical stimulation.

Stem cell therapy to reduce radiation-induced normal tissue damage

Normal tissue damage after radiotherapy is still a major problem in cancer treatment. Stem cell therapy may provide a means to reduce radiation-induced side effects and improve the quality of life of patients. This review discusses the current status in stem cell research with respect to their potential to reduce radiation toxicity. A number of different types of stem cells are being investigated for their potential to treat a variety of disorders. Their current status, localization, characterization, isolation, and potential in stem cell-based therapies are addressed. Although clinical adult stem cell research is still at an early stage, preclinical experiments show the potential these therapies may have. Based on the major advances made in this field, stem cell-based therapy has great potential to allow prevention or treatment of normal tissue damage after radiotherapy.

Adenovirus-mediated stromal cell-derived factor-1 alpha gene transfer improves cardiac structure and function after experimental myocardial infarction through angiogenic and antifibrotic actions

Stromal cell-derived factor 1α (SDF-1) is not only a major chemotactic factor, but also an inducer of angiogenesis. The effects of SDF-1α on the left ventricular remodeling in a rat myocardial infarction (MI) model were analyzed. Myocardial infarction was induced by ligation of the left coronary artery in rats. 0.5 × 10¹⁰ pfu/ml AdV-SDF-1 or 0.5 × 10¹⁰ pfu/ml Adv-LacZ were immediately injected into the infarcted myocardium, 120 μl cell-free PBS were injected into the infarcted region or the myocardial wall in control, and sham group, respectively. We found that AdV-SDF-1 group had higher LVSP and ±dP/dt_max, lower LVEDP compared to control or Adv-LacZ group. The number of c-Kit⁺ stem cells, and gene expression of SDF-1, VEGF and bFGF were obviously increased, which was associated with reduced infarct size, thicker left ventricle wall, greater vascular density and cardiocytes density in infarcted hearts of AdV-SDF-1 group. Furthermore, the expression of collagen type I and type III mRNA, and collagen accumulation in the infarcted area was lower, which was associated with decreased TGF-β1, TIMP-1 and TIMP-2 expression in AdV-SDF-1 group. Conclusion: SDF-1α could improve cardiac structure and function after Myocardial infarction through angiogenic and anti-fibrotic actions.