Coronary arterial dimension-to-left ventricular mass ratio in idiopathic dilated cardiomyopathy

The administration of high-mobility group box 1 fragment prevents deterioration of cardiac performance by enhancement of bone marrow mesenchymal stem cell homing in the delta-sarcoglycan-deficient hamster

Objectives

We hypothesized that systemic administration of high-mobility group box 1 fragment attenuates the progression of myocardial fibrosis and cardiac dysfunction in a hamster model of dilated cardiomyopathy by recruiting bone marrow mesenchymal stem cells thus causing enhancement of a self-regeneration system.

Methods

Twenty-week-old J2N-k hamsters, which are δ-sarcoglycan-deficient, were treated with systemic injection of high-mobility group box 1 fragment (HMGB1, n = 15) or phosphate buffered saline (control, n = 11). Echocardiography for left ventricular function, cardiac histology, and molecular biology were analyzed. The life-prolonging effect was assessed separately using the HMGB1 and control groups, in addition to a monthly HMGB1 group which received monthly systemic injections of high-mobility group box 1 fragment, 3 times (HMGB1, n = 11, control, n = 9, monthly HMGB1, n = 9).

Results

The HMGB1 group showed improved left ventricular ejection fraction, reduced myocardial fibrosis, and increased capillary density. The number of platelet-derived growth factor receptor-alpha and CD106 positive mesenchymal stem cells detected in the myocardium was significantly increased, and intra-myocardial expression of tumor necrosis factor α stimulating gene 6, hepatic growth factor, and vascular endothelial growth factor were significantly upregulated after high-mobility group box 1 fragment administration. Improved survival was observed in the monthly HMGB1 group compared with the control group.

Conclusions

Systemic high-mobility group box 1 fragment administration attenuates the progression of left ventricular remodeling in a hamster model of dilated cardiomyopathy by enhanced homing of bone marrow mesenchymal stem cells into damaged myocardium, suggesting that high-mobility group box 1 fragment could be a new treatment for dilated cardiomyopathy.

Adaptive-Outward and Maladaptive-Inward Arterial Remodeling Measured by Intravascular Ultrasound in Hyperhomocysteinemia and Diabetes

Background: Coronary artery remodeling implies structural changes in the vessel wall in response to various pathophysiologic conditions. However, the classification of remodeling is unclear. We hypothesized that the adaptive, positive-outward remodeling is a reactive and compensatory response to the stress. The maladaptive negative-inward constrictive remodeling is a passive atherosclerotic condition in which the vessel becomes stiffer.

Methods: Patients with atherosclerotic lesions underwent intravascular ultrasound (IVUS) scans. The size of the vessels distal to and proximal to plaques were analyzed by IVUS. Diabetes was created in mice by an intraperitoneal injection of alloxan (65 mg/kg). To reduce remodeling, mice received ciglitazone, an agonist of peroxisome proliferators activated receptor-g (PPARg) in drinking water. After 8 weeks, atherosclerotic vessels were analyzed for collagen and elastin.

Results: IVUS data suggest an adaptive coronary arterial remodeling was a positive compensatory response to various pathologic stimuli; for example, with the deposition of atherosclerotic plaque, coronary arterial segments enlarged to maintain luminal area. This phenomenon was commonly observed during the initial phases of the development of atherosclerosis. However, negative coronary artery remodeling, or a decrease in vessel area with the formation of atherosclerotic plaque, was maladaptive and was associated with smoking, hypertension, hyperhomocysteinemia, diabetes mellitus, and also after percutaneous coronary interventions (restenosis). In diabetic mice, there was increased collagen and decreased elastin contents; however, treatment with ciglitazone ameliorated the decrease in elastin contents.

Conclusion: Global enlargement of the coronary vascular tree occurs during pressure and volume overload associated with ventricular hypertrophic states such as athletic conditioning, hypertensive heart disease, and dilated cardiomyopathy. On the other hand, maladaptive coronary arterial remodeling occurs in patients with severe deconditioning, diabetes mellitus, after coronary artery bypass surgery, and in some instances, postintervention.

Umbilical cord blood-derived mesenchymal stem cells: new therapeutic weapons for idiopathic dilated cardiomyopathy?

Dilated cardiomyopathy is the most frequent etiology of non-ischemic heart failure. In a majority of cases the causal mechanism is unknown, giving rise to the term 'idiopathic' dilated cardiomyopathy (IDCM). Major pathological derangements include patchy interstitial fibrosis, degenerated cardiomyocytes, and dilatation of the cardiac chambers, but recent evidence suggests that disease progression may also have the signature of cardiac endothelial dysfunction. As we better understand the molecular basis of IDCM, novel therapeutic approaches, mainly gene transfer and cell-based therapies, are being explored. Cells with regenerative potential have been extensively tested in cardiac diseases of ischemic origin in both pre-clinical and clinical settings. However, whether cell therapy has any clinical value in IDCM patients is still being evaluated. This article is a concise summary of cell therapy studies for IDCM, with a focus on recent advances that highlight the vascular potential exhibited by umbilical cord blood-derived mesenchymal stem cells (UCBMSCs). We also provide an overview of cardiac vasculature as a key regulator of subjacent myocardial integrity and function, and discuss the potential mechanisms of UCBMSC amelioration of IDCM myocardium. Consideration of these issues shows that these cells are conceivably new therapeutic agents for this complex and elusive human disorder.

Typical coronary appearance of dilated cardiomyopathy versus left ventricular concentric hypertrophy: coronary volumes measured by multislice computed tomography

Several coronary angiographic studies have reported that enlarged and tortuous epicardial coronary arteries are characteristic of patients with left ventricular concentric hypertrophy (LVCH). Recently, we showed that small volumes opacified by contrast medium can be accurately measured by 64-multislice computed tomography (MSCT) and that there is a direct relationship between the coronary artery volume and left ventricular (LV) mass. However, the relationship of coronary artery volume with LV mass in patients with dilated cardiomyopathy (DCM) is unknown. The present study was designed to investigate this issue. Thirteen patients with DCM and 18 patients with LVCH who underwent MSCT angiography were included in this analysis. The coronary arteries were segmented on a workstation, and the appropriate window settings obtained from the results of the phantom experiments were applied to the volume-rendered images to calculate the total coronary artery volume (right and left coronary arteries). The absolute coronary lengths and volumes in patients with LVCH and DCM were greater than those in controls. The coronary artery volumes adjusted for LV mass in patients with DCM were found to be smaller than those in patients with LVCH or in controls, and these values did not differ between patients with LVCH and controls (DCM 4.1 ± 0.9, LVCH 5.4 ± 1.4, controls 5.5 ± 2.3 ml/100 g of LV mass, P < 0.005; DCM vs LVCH, P < 0.01; and DCM vs control, P < 0.0005). This study showed that the increase in the coronary artery volume in patients with LVCH matched the increase in LV mass, but a decreased coronary volume with regard to LV mass was characteristic of patients with DCM.

Idiopathic dilated cardiomyopathy exhibits defective vascularization and vessel formation

BACKGROUND

Ultrastructural findings of idiopathic dilated cardiomyopathy (IDCM) include myocyte atrophy and myofilament loss, yet little is known about the vascular abnormalities present in IDCM.

METHODS AND RESULTS

Patients with IDCM and controls underwent multi-slice CT to examine length and diameter of epicardial vasculature. The levels of mobilizing cytokines and circulating EPCs were assessed by endothelial colony formation assay and flow cytometry. Immunohistochemistry and Western blot were used to examine microvessel density and expression of HIF-1alpha and beta-catenin. Main epicardial coronary arteries were shorter and smaller, and microvascular density was reduced in the epicardium in IDCM. Epicardial vessel paucity was associated with increased numbers of HIF-1alpha(+) cells (46.8+/-13.1% vs. 19.4+/-9.4%, p=0.006) indicating local epicardial hypoxia and elevation of circulating VEGF-A (394 pg/mL vs. 22 pg/mL, p=0.001). The number of mobilized progenitors CD133(+)/VEGF-R2(+) was 21-fold higher in IDCM compared with controls (6.5+/-3.3% vs. 0.3+/-0.2%; p<0.001). Moreover, this defective vascularization was associated with reduced myocardial expression of vascular beta-catenin, an important angiogenic regulator.

CONCLUSIONS

This study shows defective vascularization and impaired vasculogenesis (the de novo vascular organization of mobilized endothelial progenitors) and angiogenesis (by which new blood vessels are formed from pre-existing mature endothelial cells) in human IDCM.

Microvascular development in porcine right and left ventricular walls

Patients with congenital heart disease who have a morphological right ventricle (RV) serving as a systemic ventricle have an increased incidence of RV dysfunction. A different structural response of microvessels to increased pressure load in the RV is a possible mechanism for this dysfunction. To examine the merit of this hypothesis, we explored the possibility that in the normal heart, the branching architecture of microvasculature in walls of the left ventricle (LV) and RV mature differently. The branching structure of intramyocardial arterioles and their downstream branches were investigated using three-dimensional (3D) micro-computed tomography (CT) images in different regions of the RV and LV walls of normal fetal, 1-mo, and 5-mo old pigs. The results point to a significant difference in the volume of myocardium perfused per vessel cross-sectional area (CSA) between the LV and RV walls at 5 mo. We speculate that this difference may be related to the reserve functional capacity of the LV, which requires a corresponding reserve in the expansion capacity of vasculature in the LV wall.

Coronary atherosclerosis in end-stage idiopathic dilated cardiomyopathy: an innocent bystander?

AIMS

Coronary atherosclerosis is occasionally found in the hearts of patients diagnosed with idiopathic dilated cardiomyopathy (IDCM), who have undergone heart transplantation (HTx). This study investigates the pathology of coronary trees in IDCM patients and correlates the findings with risk factors for atherosclerosis.

METHODS AND RESULTS

The coronary trees of hearts excised at transplantation from 55 IDCM patients [43 males, mean (+/-SD) age at diagnosis and HTx: 37.4+/-13.4 and 42.1+/-14.6 years, respectively] underwent systematic pathological investigation. The inclusion criteria were: interval between the last pre-HTx angiography and the HTx of <10 years and the absence of ischaemic events in between; the absence of ventricular scars at pathological study; optimal pre-HTx medical treatment, and no ventricular assist devices. The median time between the pre-HTx angiography and the HTx was 13 months (range: 1-93). Fifteen of the 55 patients (27%) had critical plaques in at least one of the 70 segments of the epicardial coronary tree. A multivariate statistical analysis showed that male sex, age, and dyslipidaemia were independent predictors of critical atherosclerosis.

CONCLUSION

One-fourth of the patients with end-stage IDCM hearts excised at HTx (all with angiographically normal coronary arteries at first diagnosis) have bystander critical coronary atherosclerosis whose functional role (if any) deserves investigation.

The VEGF +405 CC Promoter Polymorphism is Associated With an Impaired Prognosis in Patients With Chronic Heart Failure: A MERIT-HF Substudy

BACKGROUND

A common polymorphism positioned at +405 of the vascular endothelial growth factor (VEGF) gene is known to influence VEGF protein production. In contrast, a second polymorphism, positioned at -460 polymorphism, has no reported functional effects. VEGF is linked to angiogenesis and might directly influence the clinical outcome of patients with chronic heart failure (CHF). We investigated the association between two VEGF polymorphisms and morbidity and mortality in patients with CHF.

METHODS AND RESULTS

VEGF promoter polymorphisms +405 and -460 were examined in 596 CHF patients enrolled in the Metoprolol CR/XL Randomized Intervention Trial in Heart Failure (MERIT-HF) study and in 187 healthy controls. In CHF patients, a risk ratio for each genotype was calculated using the combined endpoint of all-cause mortality or hospitalization. The allele frequencies of the +405 and -460 polymorphisms for the CHF cohort and for 187 healthy controls were not significantly different. However, the presence of the +405 CC genotype (frequency 0.14) was independently associated with an adverse outcome as described by the MERIT study combined endpoint compared with the +405 GG genotype (risk ratio 1.65; 95%CI 1.03-2.64; P = .039). The -460 polymorphism was not associated with an altered prognosis ( P = .60).

CONCLUSION

Our results indicate that the VEGF +405 CC genotype is associated with an adverse clinical outcome in patients with CHF. This genotype has been associated with lower plasma VEGF levels, suggesting a possible mechanism of action for the gene variant. This belief is further supported by the fact that the VEGF -460 polymorphism, which does not affect plasma VEGF levels, did not adversely affect the prognosis.