The ARVC causing TMEM43-p.S358L mutation has impact on the lipid metabolism

Funding Acknowledgements

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 450999875

Background

Transmembrane protein 43 (TMEM43) is a phylogenetically highly conserved and ubiquitously expressed protein with unknown function. The protein contains four transmembrane domains located in the inner nuclear envelope and the endoplasmic reticulum (ER). A large acidic domain located between the first and second transmembrane domains, with unknown function, is exposed to the ER lumen. TMEM43-c.1073C>T is a rare fully penetrant mutation that leads to arrhythmogenic right ventricular cardiomyopathy type 5 (ARVC5). ARVC5 is associated with myocardial fibrosis, fibrofatty replacement and progressive loss of right ventricular myocardial tissue and severe arrhythmias causing sudden cardiac death (SCD) especially in males. The pathomechanism of ARVC5 is not well understood.

Methods

We isolated and cultivated primary dermal fibroblasts of three different individuals carrying TMEM43-c.1073C>T (p.S358L). Proteins were isolated from cell cultures and analysed by Orbitrap mass spectrometry. Proteome data of the mutation carriers were compared to TMEM43 wildtype control fibroblasts. Additionally, TMEM43-p.S358L and control fibroblasts were investigated by transmission electron microscopy (TEM).

Results

A total of 9 proteins were upregulated in fibroblasts expressing TMEM43-p.S358L (p<0.003). Of note, proteins involved in fatty acid metabolism, such as acyl-coenzym A (CoA) thioesterase 1 encoded by the gene ACOT1, and Malonate-CoA ligase encoded by ACSF3 were strongly upregulated (FC>3 or >2, respectively). ACOT1 catalyses hydrolysis acyl-CoAs to long chain fatty acids and CoA. ACSF3 catalyses the formation of thioesters between fatty acids and CoA. ACOT1 and ACSF3 regulate the intracellular levels of free fatty acids and are expressed in the cardiomyocytes of the human myocardium. TEM images of TMEM43-p.S358L carriers show an accumulation of multilamellar vesicles, which may support the dysregulation of the lipid metabolism.

Conclusion

The differentially regulated proteins in dermal fibroblasts and the accumulation of multilamellar vesicles suggest a dysregulation of the lipid metabolism by TMEM43-p.S358L, which may also have relevance for the development of myocardial fibrofatty replacement contributing to ARVC5.

Truncated titin proteins and titin haploinsufficiency are targets for functional recovery in human cardiomyopathy due to TTN mutations

[Figure: see text].

Mechanical circulatory support does not reduce advanced myocardial fibrosis in patients with end-stage heart failure

AIMS

Mechanical unloading by ventricular assist devices (VADs) has become increasingly important for the therapy of end-stage heart failure during the last decade. However, VAD support was claimed to be associated with partial reverse remodelling. Unfortunately, the literature describes the contradictory effects of VAD systems on cardiac fibrosis, a hallmark of cardiac remodelling. To clarify these inconsistent results, the effects on cardiac fibrosis before and after mechanical unloading in 125 patients were examined.

METHODS AND RESULTS

Left ventricular myocardial tissue from ischaemic or non-ischaemic cardiomyopathy patients undergoing VAD implantation and subsequent cardiac transplantation and non-failing hearts of the control group were analysed for 4-hydroxyproline (4OH-P) content as a marker for collagen protein. In addition, collagen cross-linking and mRNAs of collagens I and III and transforming growth factor beta-1 were measured. 4OH-P content was significantly increased in failing hearts compared with the control group and increased (P < 0.05) after mechanical unloading (nmol/mg tissue, mean ± standard deviation: 16.74 ± 9.68 vs. 7.75 ± 2.39 and 18.57 ± 9.19). However, plotting of the 4OH-P ratios (post/pre-VAD) against the collagen content pre-VAD could be fitted by non-linear regression. Collagen cross-linking correlated strongly with the total collagen content in pre- and post-VAD myocardium (r²  = 0.73 and 0.71, respectively). In contrast to the total collagen content, all three mRNAs of fibrotic genes were significantly down-regulated during VAD support when compared to pre-VAD.

CONCLUSIONS

This investigation of a comparably large patient cohort revealed that cardiac fibrosis was strongly increased in heart failure and increased even after mechanical unloading. The mRNAs of collagens I and III are independently regulated from the collagen protein.

Cardiomyopathy-associated mutations in the RS domain affect nuclear localization of RBM20

Mutations in RBM20 encoding the RNA-binding motif protein 20 (RBM20) are associated with an early onset and clinically severe forms of cardiomyopathies. Transcriptome analyses revealed RBM20 as an important regulator of cardiac alternative splicing. RBM20 mutations are especially localized in exons 9 and 11 including the highly conserved arginine and serine-rich domain (RS domain). Here, we investigated in several cardiomyopathy patients, the previously described RBM20-mutation p.Pro638Leu localized within the RS domain. In addition, we identified in a patient the novel mutation p.Val914Ala localized in the (glutamate-rich) Glu-rich domain of RBM20 encoded by exon 11. Its impact on the disease was investigated with a novel TTN- and RYR2-splicing assay based on the patients' cardiac messenger RNA. Furthermore, we showed in cell culture and in human cardiac tissue that mutant RBM20-p.Pro638Leu is not localized in the nuclei but causes an abnormal cytoplasmic localization of the protein. In contrast the splicing deficient RBM20-p.Val914Ala has no influence on the intracellular localization. These results indicate that disease-associated variants in RBM20 lead to aberrant splicing through different pathomechanisms dependent on the localization of the mutation. This might have an impact on the future development of therapeutic strategies for the treatment of RBM20-induced cardiomyopathies.

0873 Obstructive Sleep Apnea Impacts Brain Development in Obese Children and Adolescents: An MRI Study

Introduction

Obstructive sleep apnea (OSA) is a breathing disorder characterized by episodes of nocturnal hypoxia and chronic systemic inflammation, affecting more than 50% of obese youths. Both obesity and OSA independently have a negative impact on brain structure and function, but their combined effect on the developing brain is unknown. The purpose of this study was to assess MRI measurements of cortical thickness (CT) in obese youths with various degrees of OSA severity. We hypothesized that CT is abnormal in obese adolescents with OSA.

Methods

55 obese subjects (26 females, 29 males, mean 14.3 ± 2.4 years) were included in the analysis. All subjects were assessed with polysomnography (PSG) to evaluate presence and severity of OSA. T1-weighted MPRAGE images were acquired using a 3T MRI scanner following PSG. CT was extracted using the CIVET 2.1.1 pipeline, and statistical analysis was performed on SurfStat to examine global and regional CT in relation to age using a general linear model.

Results

Based on PSG outcome, subjects were divided into 3 groups, no OSA (OAHI &lt; 1.5 events/hr., n = 15), mild OSA (OAHI &lt; 5, n = 14), and moderate/severe OSA (OAHI &#8805; 5, n = 26). Cortical thickness analysis revealed a negative-trending correlation between global CT and age in no OSA (T = -0.49, P &gt; 0.6), as seen in typical development. This correlation weakened in the presence of mild OSA (T = -0.20, P &gt; 0.8) and became significantly positive in moderate/severe OSA (T = 3.87, P = 0.001), affecting several cortical areas.

Conclusion

These results indicate that brain development in obese adolescents with moderate/severe OSA significantly deviates from the typical trajectory of cortical thinning. This thickening could be due to exacerbated inflammation from the combined effect of both diseases, or a neurotrophic effect of leptin. More data is needed to validate these findings.

Support

None

Changes in Von Willebrand factor profile predicts clinical outcomes in patients on mechanical circulatory support

BACKGROUND

The associations between mechanical circulatory support (MCS), acquired von Willebrand syndrome (AvWS), and clinical outcome are incompletely understood.

METHODS

In 128 heart failure patients with pulsatile MCS implants (65 total artificial heart or biventricular assist device implants, 63 left ventricular assist device [LVAD] implants) and 76 patients with continuous flow LVAD implants, we analyzed the von Willebrand factor (vWF) profile before (≤24 h) and 17.5 (standard deviation: 5.1) days after device implant. We determined vWF concentrations, vWF activity, and vWF collagen binding capacity and calculated ratios of vWF activity/binding capacity with vWF concentration. The relation of the vWF profile with clinical outcomes such as stroke, gastrointestinal bleeding, and survival was also evaluated. Events were assessed up to 1 year of device implant.

RESULTS

All entities of vWF were already significantly elevated preoperatively and remained high after MCS implantation. The ratios of vWF activity/concentration (vWF:RCo/Ag) and collagen binding capacity/concentration (vWF:CBA/Ag) were significantly reduced preoperatively and remained low postoperatively, indicating AvWS. The preoperative alterations in the vWF profile were already present in patients without intra-aortic balloon pump and/or extracorporeal circulatory membrane oxygenation implants. The vWF profile was unrelated to postoperative stroke. However, a higher postoperative ratio of vWF:CBA/Ag was independently associated with increased gastrointestinal bleeding. In addition, a postoperative increase in vWF concentrations and activity were independent predictors of increased 1-year mortality.

CONCLUSIONS

Our data indicate that AvWS is present in heart failure patients before device implantation, and is independently associated with clinical outcomes, especially with 1-year mortality.

Breath-Hold Blood Oxygen Level-Dependent MRI: A Tool for the Assessment of Cerebrovascular Reserve in Children with Moyamoya Disease

BACKGROUND AND PURPOSE

There is a critical need for a reliable and clinically feasible imaging technique that can enable prognostication and selection for revascularization surgery in children with Moyamoya disease. Blood oxygen level-dependent MR imaging assessment of cerebrovascular reactivity, using voluntary breath-hold hypercapnic challenge, is one such simple technique. However, its repeatability and reliability in children with Moyamoya disease are unknown. The current study sought to address this limitation.

MATERIALS AND METHODS

Children with Moyamoya disease underwent dual breath-hold hypercapnic challenge blood oxygen level-dependent MR imaging of cerebrovascular reactivity in the same MR imaging session. Within-day, within-subject repeatability of cerebrovascular reactivity estimates, derived from the blood oxygen level-dependent signal, was computed. Estimates were associated with demographics and intellectual function. Interrater reliability of a qualitative and clinically applicable scoring scheme was assessed.

RESULTS

Twenty children (11 males; 12.1 ± 3.3 years) with 30 MR imaging sessions (60 MR imaging scans) were included. Repeatability was "good" on the basis of the intraclass correlation coefficient (0.70 ± 0.19). Agreement of qualitative scores was "substantial" (κ = 0.711), and intrarater reliability of scores was "almost perfect" (κ = 0.83 and 1). Younger participants exhibited lower repeatability (P = .027). Repeatability was not associated with cognitive function (P > .05). However, abnormal cerebrovascular reactivity was associated with slower processing speed (P = .015).

CONCLUSIONS

Breath-hold hypercapnic challenge blood oxygen level-dependent MR imaging is a repeatable technique for the assessment of cerebrovascular reactivity in children with Moyamoya disease and is reliably interpretable for use in clinical practice. Standardization of such protocols will allow further research into its application for the assessment of ischemic risk in childhood cerebrovascular disease.

Cardiomyocyte Hypertrophy in Arrhythmogenic Cardiomyopathy

Arrhythmogenic cardiomyopathy (AC) is a hereditary disease leading to sudden cardiac death or heart failure. AC pathology is characterized by cardiomyocyte loss and replacement fibrosis. Our goal was to determine whether cardiomyocytes respond to AC progression by pathological hypertrophy. To this end, we examined tissue samples from AC patients with end-stage heart failure and tissue samples that were collected at different disease stages from desmoglein 2-mutant mice, a well characterized AC model. We find that cardiomyocyte diameters are significantly increased in right ventricles of AC patients. Increased mRNA expression of the cardiac stress marker natriuretic peptide B is also observed in the right ventricle of AC patients. Elevated myosin heavy chain 7 mRNA expression is detected in left ventricles. In desmoglein 2-mutant mice, cardiomyocyte diameters are normal during the concealed disease phase but increase significantly after acute disease onset on cardiomyocyte death and fibrotic myocardial remodeling. Hypertrophy progresses further during the chronic disease stage. In parallel, mRNA expression of myosin heavy chain 7 and natriuretic peptide B is up-regulated in both ventricles with right ventricular preference. Calcineurin/nuclear factor of activated T cells (Nfat) signaling, which is linked to pathological hypertrophy, is observed during AC progression, as evidenced by Nfatc2 and Nfatc3 mRNA in cardiomyocytes and increased mRNA of the Nfat target regulator of calcineurin 1. Taken together, we demonstrate that pathological hypertrophy occurs in AC and is secondary to cardiomyocyte loss and cardiac remodeling.

Influence of Mechanical Circulatory Support on Endothelin Receptor Expression in Human Left Ventricular Myocardium from Patients with Dilated Cardiomyopathy (DCM)

Background

In terminal failing hearts ventricular assist devices (VAD) are implanted as a bridge to transplantation. Endothelin receptor (ETR) antagonists are used for treatment of secondary pulmonary hypertension in VAD patients. However, the cardiac ETR regulation in human heart failure and during VAD support is incompletely understood.

Methods

In paired left ventricular samples of 12 dilated cardiomyopathy patients we investigated the density of endothelin A (ET_A) and B (ET_B) receptors before VAD implantation and after device removal. Left ventricular samples of 12 non-failing donor hearts served as control. Receptor quantification was performed by binding of [¹²⁵I]-ET-1 in the presence of nonselective and ET_A selective ETR ligands as competitors. Additionally, the ETR mRNA expression was analyzed using quantitative real-time-PCR.

Results

The mRNA of ET_A but not ET_B receptors was significantly elevated in heart failure, whereas total ETR density analyzed by radioligand binding was significantly reduced due to ET_B receptor down regulation. ET_A and ET_B receptor density showed poor correlation to mRNA data (spearman correlation factor: 0.43 and 0.31, respectively). VAD support had no significant impact on the density of both receptors and on mRNA expression of ET_A whereas ET_B mRNA increased during VAD. A meta-analysis reveals that the ET_A receptor regulation in human heart failure appears to depend on non-failing hearts.

Conclusions

In deteriorating hearts of patients suffering from dilated cardiomyopathy the ET_A receptor density is not changed whereas the ET_B receptor is down regulated. The mRNA and the proteins of ET_A and ET_B show a weak correlation. Non-failing hearts might influence the interpretation of ET_A receptor regulation. Mechanical unloading of the failing hearts has no impact on the myocardial ETR density.

Normal-appearing white matter permeability distinguishes poor cognitive performance in processing speed and working memory

BACKGROUND AND PURPOSE

Secondary-progressive MS is characterized by reduced acute inflammation and contrast enhancement but with increased axonal degeneration and cognitive/clinical disability that worsens with advanced disease. Relative recirculation, extracted from DSC is a surrogate measure of BBB integrity. We hypothesized that normal-appearing white matter relative recirculation is reduced in cognitively impaired compared with nonimpaired secondary-progressive MS, reflecting more advanced disease.

MATERIALS AND METHODS

Cognitive performance was classified as impaired or nonimpaired by use of Minimal Assessment of Cognitive Function In MS test components. Demographic data, brain parenchymal fraction, WM lesion fraction, and weighted mean normal-appearing white matter relative recirculation were compared in cognitively dichotomized groups. Univariate and multivariate logistic regressions were used to study the association between cognitive test results and normal-appearing white matter relative recirculation.

RESULTS

The mean (SD) age of 36 patients with secondary-progressive MS studied was 55.9 ± 9.3 years; 13 of 36 (36%) patients were male. A highly significant difference between normal-appearing white matter relative recirculation and WM lesion relative recirculation was present for all patients (P < .001). Normal-appearing white matter relative recirculation in impaired patients was significantly lower than in nonimpaired subjects for the Symbol Digit Modalities Test (P = .007), Controlled Word Association Test (P = .008), and Paced Auditory Serial Addition Test (P = .024). The Expanded Disability Status Scale demonstrated an inverse correlation with normal-appearing white matter relative recirculation (r = -0.319, P = .075). After adjustment for confounders, significant normal-appearing white matter relative recirculation reduction persisted for the Symbol Digit Modalities Test (P = .023) and the Paced Auditory Serial Addition Test (P = .047) but not for the Controlled Word Association Test (P = .13) in impaired patients.

CONCLUSIONS

Significant normal-appearing white matter relative recirculation reduction exists in cognitively impaired patients with secondary-progressive MS, localizing to the domains of processing speed and working memory.

Regulation of cyclic adenosine monophosphate release by selective β2-adrenergic receptor stimulation in human terminal failing myocardium before and after ventricular assist device support

BACKGROUND

Response to catecholamines is blunted in terminal heart failure due to β-receptor downregulation and uncoupling from adenylyl cyclase (AC). Improved myocardial responsiveness to catecholamines after ventricular assist device (VAD) support is associated with upregulation of β1-adrenergic receptors (β1-ARs). Little is known about the regulation of AC and β2-AR coupling after VAD; moreover β2-AR stimulation during VAD was claimed to induce myocardial recovery.

METHODS

We analyzed in VAD-supported human myocardium the regulation of AC activity upon β1-AR and selective β2-AR stimulation in 8 non-failing hearts (NF) and 17 paired samples of VAD patients. AC messenger RNA was measured by TaqMan. AC was stimulated via β2-AR using clenbuterol (β2-AR agonist) and bisoprolol (β1-AR blocker). Organ bath experiments were done with trabeculae from both ventricles. Samples were stratified according to chronic or acute heart failure history.

RESULTS

Isoprenaline-induced AC activity was downregulated (p < 0.001) pre-VAD and increased significantly (p < 0.05) after unloading (mean ± standard deviation pmole/mg/min) in NF (47.9 ± 14.9), pre-VAD (24.35 ± 13.3), and post-VAD (50.04 ± 50.25). Forskolin stimulation revealed significant (p < 0.05) upregulation of AC activity during VAD, especially in acutely failing hearts (NF, 192.1 ± 68.7; pre-VAD, 191.1 ± 60.4; post-VAD, 281.5 ± 133). However, forskolin stimulation relative to isoprenaline-induced inotropy remained reduced before and after VAD compared with NF. The selective stimulation of β2-AR did not reveal influence of VAD support on β2-AR-AC coupling. Stimulation of ventricular trabeculae by > 100 μmole/liter clenbuterol revealed negative inotropic responses.

CONCLUSIONS

VAD does not influence β2-AR coupling to AC stimulation. Elevated response to catecholamines after VAD support is influenced by β1-AR upregulation and modulation of AC activity. Restoration of β-adrenergic responsiveness was restricted to acutely failing hearts.

Myocardial transcriptome analysis of human arrhythmogenic right ventricular cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited cardiomyopathy primarily of the right ventricle characterized through fibrofatty replacement of cardiomyocytes. The genetic etiology in ARVC patients is most commonly caused by dominant inheritance and high genetic heterogeneity. Though histological examinations of ARVC-affected human myocardium reveals fibrolipomatous replacement, the molecular mechanisms leading to loss of cardiomyocytes are largely unknown. We therefore analyzed the transcriptomes of six ARVC hearts and compared our findings to six nonfailing donor hearts (NF). To characterize the ARVC-specific transcriptome, we compared our findings to samples from seven patients with idiopathic dilated cardiomyopathy (DCM). The myocardial DCM and ARVC samples were prepared from hearts explanted during an orthotopic heart transplantation representing myocardium from end-stage heart failure patients (NYHA IV). From each heart, left (LV) and right ventricular (RV) myocardial samples were analyzed by Affymetrix HG-U133 Plus 2.0 arrays, adding up to six sample groups. Unsupervised cluster analyses of the groups revealed a clear separation of NF and cardiomyopathy samples. However, in contrast to the other samples, the analyses revealed no distinct expression pattern in LV and RV of myocardial ARVC samples. We further identified differentially expressed transcripts using t-tests and found transcripts separating diseased and NF ventricular myocardium. Of note, in failing myocardium only ~15-16% of the genes are commonly regulated compared with NF samples. In addition both cardiomyopathies are clearly distinct on the transcriptome level. Comparison of the expression patterns between the failing RV and LV using a paired t-test revealed a lack of major differences between LV and RV gene expression in ARVC hearts. Our study is the first analysis of specific ARVC-related RV and LV gene expression patterns in terminal failing human hearts.

Wavelets and fuzzy relational classifiers: a novel diffusion-weighted image analysis system for pediatric metabolic brain diseases

The diffusion-weighted imaging (DWI) technique can be utilized to investigate a variety of diseases. We propose an automated pilot system, which assists in the diagnosis of metabolic brain diseases, utilizing the DWI. In this study, DWI images are preprocessed and exponential apparent diffusion coefficient (eADC) images are produced. The eADC images are later brain extracted and normalized to a standard brain template. Subsequently, we utilized wavelets to denoise the eADC images. The images are rectified, thresholded and now conspicuous abnormal regions are subsequently identified utilizing different brain atlases. Abnormal regions constitute the features that will be used by a fuzzy relational classifier in order to categorize the diseases. A sensitivity and specificity of 60% and 93.33%, respectively, in detecting metabolic brain diseases have been achieved.

Global gene expression analysis in nonfailing and failing myocardium pre- and postpulsatile and nonpulsatile ventricular assist device support

Mechanical unloading by ventricular assist devices (VAD) leads to significant gene expression changes often summarized as reverse remodeling. However, little is known on individual transcriptome changes during VAD support and its relationship to nonfailing hearts (NF). In addition no data are available for the transcriptome regulation during nonpulsatile VAD support. Therefore we analyzed the gene expression patterns of 30 paired samples from VAD-supported (including 8 nonpulsatile VADs) and 8 nonfailing control hearts (NF) using the first total human genome array available. Transmural myocardial samples were collected for RNA isolation. RNA was isolated by commercial methods and processed according to chip-manufacturer recommendations. cRNA were hybridized on Affymetrix HG-U133 Plus 2.0 arrays, providing coverage of the whole human genome Array. Data were analyzed using Microarray Analysis Suite 5.0 (Affymetrix) and clustered by Expressionist software (Genedata). We found 352 transcripts were differentially regulated between samples from VAD implantation and NF, whereas 510 were significantly regulated between VAD transplantation and NF (paired t-test P < 0.001, fold change ≥1.6). Remarkably, only a minor fraction of 111 transcripts was regulated in heart failure (HF) and during VAD support. Unsupervised hierarchical clustering of paired VAD and NF samples revealed separation of HF and NF samples; however, individual differentiation of VAD implantation and VAD transplantation was not accomplished. Clustering of pulsatile and nonpulsatile VAD did not lead to robust separation of gene expression patterns. During VAD support myocardial gene expression changes do not indicate reversal of the HF phenotype but reveal a distinct HF-related pattern. Transcriptome analysis of pulsatile and nonpulsatile VAD-supported hearts did not provide evidence for a pump mode-specific transcriptome pattern.

Texture analysis: a review of neurologic MR imaging applications

Texture analysis describes a variety of image-analysis techniques that quantify the variation in surface intensity or patterns, including some that are imperceptible to the human visual system. Texture analysis may be particularly well-suited for lesion segmentation and characterization and for the longitudinal monitoring of disease or recovery. We begin this review by outlining the general procedure for performing texture analysis, identifying some potential pitfalls and strategies for avoiding them. We then provide an overview of some intriguing neuro-MR imaging applications of texture analysis, particularly in the characterization of brain tumors, prediction of seizures in epilepsy, and a host of applications to MS.

Contrast-enhanced MR imaging in acute ischemic stroke: T2* measures of blood-brain barrier permeability and their relationship to T1 estimates and hemorrhagic transformation

BACKGROUND AND PURPOSE

rtPA is an effective treatment for AIS, yet it is substantially underused due to the increased risk of HT. Recent work suggests that permeability-related information can be extracted from routine T2*-based perfusion images by measuring the rR of the contrast agent. Given that other T2*-based measures have recently been proposed, the purpose of this study was to evaluate 4 such permeability measures in identifying patients with AIS who will proceed to HT.

MATERIALS AND METHODS

Eighteen patients with AIS were examined within a mean of 3.3 +/- 1.4 hours postonset. Dynamic T2*-weighted imaging consisted of a single-shot EPI following a bolus of gadodiamide. HT was determined on follow-up CT or MR imaging at 24-72 hours. Mean values of rR, Peak Height, Recovery, as well as Slope were calculated and analyzed on the basis of follow-up HT status.

RESULTS

Eight patients proceeded to HT. The mean rR for patients with HT was significantly greater than that for patients without HT (0.22 +/- 0.06 versus 0.14 +/- 0.06, P = .006), while there was a trend toward decreased %Recovery in patients with HT (76 +/- 6 versus 82 +/- 11%, P = .092). There was a significant negative correlation between %Recovery and rR (r = -0.88, P < .001). No significant differences or trends were detected with respect to Peak Height or Slope.

CONCLUSIONS

Both rR and %Recovery can be readily extracted from a routine perfusion MR imaging dataset and show potential for identifying HT during the acute phase poststroke.

Recombinant tissue plasminogen activator increases blood-brain barrier disruption in acute ischemic stroke: an MR imaging permeability study

BACKGROUND AND PURPOSE

Although thrombolytic therapy (recombinant tissue plasminogen activator [rtPA]) represents an important step forward in acute ischemic stroke (AIS) management, there is a clear need to identify high-risk patients. The purpose of this study was to investigate the role of quantitative permeability (KPS) MR imaging in patients with AIS treated with and without rtPA. We hypothesized that rtPA would increase KPS and that KPS MR imaging can be used to predict the risk of hemorrhagic transformation (HT).

MATERIALS AND METHODS

Thirty-six patients with AIS were examined within a mean of 3.6 hours of documented symptom onset. KPS MR imaging was performed as part of our AIS protocol. KPS coefficients in the stroke lesion were estimated for all patients, and the relationship between KPS and both HT and rtPA was investigated by using Student t tests. Receiver operating characteristic (ROC) curves were computed for predicting HT from KPS.

RESULTS

The occurrence rate of HT for patients who received rtPA and those who did not was 43% and 37%, respectively. Assessment of KPS in the lesion revealed significant differences between those who hemorrhaged and those who did not (P < .0001) as well as between rtPA-treated and untreated patients (P = .008). ROC analysis indicated a KPS threshold of 0.67 mL/100 g/min, with a sensitivity of 92% and a specificity of 78%.

CONCLUSIONS

The results of this study indicate that KPS is able to identify patients at higher risk of HT and may allow use of physiologic imaging rather than time from onset of symptoms to guide treatment decision.

Genomic profiling of developing cardiomyocytes from recombinant murine embryonic stem cells reveals regulation of transcription factor clusters

Cardiomyocytes derived from pluripotent embryonic stem cells (ESC) have the advantage of providing a source for standardized cell cultures. However, little is known on the regulation of the genome during differentiation of ESC to cardiomyocytes. Here, we characterize the transcriptome of the mouse ESC line CM7/1 during differentiation into beating cardiomyocytes and compare the gene expression profiles with those from primary adult murine cardiomyocytes and left ventricular myocardium. We observe that the cardiac gene expression pattern of fully differentiated CM7/1-ESC is highly similar to adult primary cardiomyocytes and murine myocardium, respectively. This finding is underlined by demonstrating pharmacological effects of catecholamines and endothelin-1 on ESC-derived cardiomyocytes. Furthermore, we monitor the temporal changes in gene expression pattern during ESC differentiation with a special focus on transcription factors involved in cardiomyocyte differentiation. Thus, CM7/1-ESC-derived cardiomyocytes are a promising new tool for functional studies of cardiomyocytes in vitro and for the analysis of the transcription factor network regulating pluripotency and differentiation to cardiomyocytes.

Plasma biomarkers of myocardial fibrosis and remodeling in terminal heart failure patients supported by mechanical circulatory support devices

BACKGROUND

In this study we analyzed putative biomarkers for myocardial remodeling in plasma from 55 endstage heart failure patients with the need for mechanical circulatory support (MCS). We compared our data to 40 healthy controls and examined if MCS by either ventricular assist devices or total artificial hearts has an impact on plasma concentrations of remodeling biomarkers.

METHODS & RESULTS

Plasma biomarkers were analysed pre and 30 days post implantation of a MCS device using commercially available enzyme linked immunosorbent assays (ELISA). We observed that the plasma concentrations of remodeling biomarkers: tissue inhibitor of metalloproteinase 1 (TIMP1), tenascin C (TNC), galectin 3 (LGALS3), osteopontin (OPN) and of neurohumoral biomarker brain natriuretic peptide (BNP), are significantly elevated in patients with terminal heart failure compared to healthy controls. We did not find elevated plasma concentrations for matrix metalloproteinase 2 (MMP2) and procollagen I C-terminal peptide (PCIP). However, only BNP plasma levels were reduced by MCS, whereas the concentrations of remodeling biomarkers remained elevated or even increased further 30 days after MCS. LGALS3 plasma concentrations at device implantation were significantly higher in patients who did not survive MCS due to multi organ failure (MOF).

CONCLUSIONS

Our findings indicate that mechanical unloading in endstage heart failure is not reflected by a rapid reduction of remodeling plasma biomarkers.

PCA-SGA implementation in classification and disease specific feature extraction of the brain MRS signals

The medical diagnostic systems often suffer from the high dimensional data. In this study, Principle Component Analysis (PCA) has been used for dimensionality reduction of the brain Magnetic Resonance Spectroscopy (MRS) signals. Afterwards, the Simple Genetic Algorithms (SGA) is utilized in order to classify different brain diseases. SGA is later used to extract MRS signal features in case of metabolic brain diseases (MD). The PCA-SGA implementation received the specificity of 89.91%. The SGA was able to achieve the sensitivity of 84.84% and positive predictivity of 88.46% in extracting disease specific MRS signal features.

Transforming growth factor beta1-regulated xylosyltransferase I activity in human cardiac fibroblasts and its impact for myocardial remodeling

In cardiac fibrosis remodeling of the failing myocardium is associated with a complex reorganization of the extracellular matrix (ECM). Xylosyltransferase I and Xylosyltransferase II (XT-I and XT-II) are the key enzymes in proteoglycan biosynthesis, which are an important fraction of the ECM. XT-I was shown to be a measure for the proteoglycan biosynthesis rate and a biochemical fibrosis marker. Here, we investigated the XT-I and XT-II expression in cardiac fibroblasts and in patients with dilated cardiomyopathy and compared our findings with nonfailing donor hearts. We analyzed XT-I and XT-II expression and the glycosaminoglycan (GAG) content in human cardiac fibroblasts incubated with transforming growth factor (TGF)-beta(1) or exposed to cyclic mechanical stretch. In vitro and in vivo no significant changes in the XT-II expression were detected. For XT-I we found an increased expression in parallel with an elevated chondroitin sulfate-GAG content after incubation with TGF-beta(1) and after mechanical stretch. XT-I expression and subsequently increased levels of GAGs could be reduced with neutralizing anti-TGF-beta(1) antibodies or by specific inhibition of the activin receptor-like kinase 5 or the p38 mitogen-activated protein kinase pathway. Usage of XT-I small interfering RNA could specifically block the increased XT-I expression under mechanical stress and resulted in a significantly reduced chondroitin sulfate-GAG content. In the left and right ventricular samples of dilated cardiomyopathy patients, our data show increased amounts of XT-I mRNA compared with nonfailing controls. Patients had raised levels of XT-I enzyme activity and an elevated proteoglycan content. Myocardial remodeling is characterized by increased XT-I expression and enhanced proteoglycan deposition. TGF-beta(1) and mechanical stress induce XT-I expression in cardiac fibroblasts and have impact for ECM remodeling in the dilated heart. Specific blocking of XT-I expression confirmed that XT-I catalyzes a rate-limiting step during fibrotic GAG biosynthesis.

Selective upregulation of β1-adrenergic receptors and dephosphorylation of troponin I in end-stage heart failure patients supported by ventricular assist devices

In terminal failing hearts, adrenergic receptors are downregulated and intracellular adrenergic signal transduction is inhibited. Mechanical circulatory support by ventricular assist devices (VAD) is used to bridge patients to heart transplantation. Mechanical unloading by VAD may induce reverse remodeling in heart transplantation (HTx) candidates. However, little is known on beta-adrenergic receptor subtype regulation and adrenergic signal transduction under VAD-support. We investigated paired myocardial samples from 16 VAD-supported patients and 9 non-failing donor hearts. We analyzed beta-adrenergic receptor subtype regulation by real-time PCR and radioligand binding and cardiac troponin I phosphorylation (by phospho-cTnI-specific antibodies). We found that the beta1-adrenergic receptor (beta1AR) is downregulated at VAD-implantation on mRNA and protein levels whereas the beta2-adrenergic receptor (beta2AR) was not. After VAD-support, beta1AR protein but not its mRNA was upregulated, whereas the degree of cTnI-phosphorylation was reduced. Upregulation of beta1AR was enhanced by beta blocking medication during VAD-support. However, in 9 out of 15 patients, beta1AR-density remained below the 0.25 percentile of donor hearts. VAD-support is associated with partial normalization of the betaAR-signal transduction pathways. This beneficial effect is related to a posttranscriptional increase in beta1AR-density.

Relevance of brain natriuretic peptide in preload-dependent regulation of cardiac sarcoplasmic reticulum Ca2+ ATPase expression

BACKGROUND

In heart failure (HF), ventricular myocardium expresses brain natriuretic peptide (BNP). Despite the association of elevated serum levels with poor prognosis, BNP release is considered beneficial because of its antihypertrophic, vasodilating, and diuretic properties. However, there is evidence that BNP-mediated signaling may adversely influence cardiac remodeling, with further impairment of calcium homeostasis.

METHODS AND RESULTS

We studied the effects of BNP on preload-dependent myocardial sarcoplasmic reticulum Ca2+ ATPase (SERCA2a) expression. In rabbit isolated muscle strips stretched to high preload and shortening isotonically over 6 hours, the SERCA/glyceraldehyde phosphate dehydrogenase mRNA ratio was enhanced by 168% (n=8) compared with unloaded preparations (n=8; P<0.001). Recombinant human BNP at a concentration typically found in end-stage HF patients (350 pg/mL) abolished SERCA upregulation by stretch (n=9; P<0.0001 versus BNP free). Inhibition of cyclic guanosine 3',5' monophosphate (cGMP)-phosphodiesterase-5 mimicked this effect, whereas inhibition of cGMP-dependent protein kinase restored preload-dependent SERCA upregulation in the presence of recombinant human BNP. Furthermore, in myocardium from human end-stage HF patients undergoing cardiac transplantation (n=15), BNP expression was inversely correlated with SERCA levels. Moreover, among 23 patients treated with left ventricular assist devices, significant SERCA2a recovery occurred in those downregulating BNP.

CONCLUSIONS

Our data indicate that preload stimulates SERCA expression. BNP antagonizes this mechanism via guanylyl cyclase-A, cGMP, and cGMP-dependent protein kinase. This novel action of BNP to uncouple preload-dependent SERCA expression may adversely affect contractility in patients with HF.

Influence of ACE-inhibition and mechanical unloading on the regulation of extracellular matrix proteins in the myocardium of heart transplantation candidates bridged by ventricular assist devices

BACKGROUND

Whether adverse structural changes in the myocardium due to remodelling can be reversed by ventricular assist device (VAD) support in patients with end-stage heart failure is controversial.

AIMS

To investigate the effect of VAD support on the extra-cellular matrix.

METHODS

We analysed the collagen content in terminal failing ventricles of VAD-patients and donor hearts using 4-hydroxyproline for total collagen and real time RT-PCR for fibronectin (FN), collagen I alpha 1 (Col1A1), III alpha 1 (Col3A1) and TGF beta 1 analysis.

RESULTS

Compared to donor hearts we found similar increases in Col1A1 and TGF beta1 but not Col3A1 and FN mRNAs, which were similar in the myocardium from patients receiving a VAD or heart transplant. However, patients receiving ACE-I during VAD-support had lower Col1A1 mRNA content at transplantation. The total collagen content was not influenced by mechanical unloading or by ACE-I medication.

CONCLUSION

Mechanical unloading by VAD does not reduce the collagen content of the terminal failing ventricle possibly due to increased TGF beta1 levels. However, Col1A1 production may be reduced by ACE-I medication during VAD support.

Increased cardiac expression of tissue inhibitor of metalloproteinase-1 and tissue inhibitor of metalloproteinase-2 is related to cardiac fibrosis and dysfunction in the chronic pressure-overloaded human heart

BACKGROUND

Alterations in the balance of matrix metalloproteinases (MMPs) and their specific tissue inhibitors (TIMPs) are involved in left ventricular (LV) remodeling. Whether their expression is related to interstitial fibrosis or LV dysfunction in patients with chronic pressure overload-induced LV hypertrophy, however, is unknown.

METHODS AND RESULTS

Therefore, cardiac biopsies were taken in 36 patients with isolated aortic stenosis (AS) and in 29 control patients without LV hypertrophy. Microarray analysis revealed significantly increased mRNA expression of collagen types I, III, and IV and transcripts involved in collagen synthesis, including procollagen endopeptidase and lysine and proline hydroxylases, in AS compared with control patients. Collagen deposition was greater in AS than in control patients and was most pronounced in AS patients with severe diastolic dysfunction. Cardiac mRNA expression of TIMP-1 and TIMP-2 was significantly increased in AS compared with control patients (mRNA transcript levels normalized to GAPDH: TIMP-1, 0.67+/-0.1 in AS versus 0.37+/-0.08 in control patients; TIMP-2, 9.5+/-2.6 in AS versus 1.6+/-0.4 in control patients; P<0.05 for both) but did not differ significantly for MMP-1, -2, or -9. Cardiac TIMP-1 and -2 transcripts were significantly related to the degree of interstitial fibrosis and proportional to diastolic dysfunction in AS patients.

CONCLUSIONS

Cardiac expression of TIMP-1 and TIMP-2 is significantly increased in chronic pressure-overloaded human hearts compared with controls and is related to the degree of interstitial fibrosis.

The structural examination of myocardial samples from patients with end-stage heart failure supported by ventricular assist devices using electron microscopy and amino acid analysis reveals low degree of reverse remodeling

BACKGROUND

Chronic heart failure is a multifactorial, progressive disease of many causes and is associated with complex ventricular remodeling. Deposition of extracellular matrix proteins and sarcomeric disarray of the myocytes occur in end-stage heart failure. Ventricular assist devices (VAD), implanted as bridge to transplantation, may reverse ventricular remodeling. Although successfully weaning patients from VAD support has been reported, it is not clear to what degree reversal of remodeling occurs in unloaded failing hearts. Because collagen deposition and ultrastructural disarray are hallmarks of myocardial remodeling, we analyzed the myocardial ultrastructure and collagen content of VAD-supported hearts before and after mechanical unloading.

METHODS

We used amino acid analysis to measure collagen content (4-hydroxyproline content) in 24 transplant candidates receiving VAD support. We used transmission electron microscopy to examine the ultrastructure in 6 patients receiving VAD support.

RESULTS

The 4-hydroxyproline content increased significantly at VAD implantation and was not altered by mechanical unloading. The ultrastructure showed signs of persisting cardiomyopathy.

CONCLUSION

Mechanical unloading does not alter the total collagen content of the supported, failing heart. Thus, structural reversal of the remodeling process associated with heart failure is not a general phenomenon in mechanically unloaded hearts.

Differential regulation of Ca2+-dependent ATPase-activity in left ventricular myocardium during mechanical circulatory support

BACKGROUND

Myocardial recovery is observed in some end-stage heart failure patients after mechanical circulatory support. The sarcoplasmic reticulum Ca(2+)-adenosine triphosphatase (Ca2+-ATPase) activity is down-regulated in failing myocardium and contributes to heart failure-associated contraction/relaxation abnormalities. Regulation of Ca(2+)-ATPase after mechanical support was shown to be heterogeneous. Thus, we analyzed Ca(2+)-ATPase activity and protein expression in the paired myocardial samples of 21 patients supported by ventricular assist devices to identify factors that influence restoration of the Ca(2+)-transient after ventricular assist device support.

METHODS

We measured Ca(2+)-ATPase activity using a reduced nicotinamide-adenine dinucleotide-coupled reaction, determined sarcoplasmic reticulum Ca(2+)-dependent ATPase protein using Western blotting, and determined 4-hydroxyproline using amino-acid analysis.

RESULTS

The mean Ca(2+)-ATPase activity decreased at assist-device implantation and slightly increased at transplantation, but remained significantly lower than in non-failing donor hearts. However, individual responses were heterogeneous. Patients with older age, increased left ventricular diameter, and increased 4-hydroxyproline content showed down-regulation of Ca(2+)-ATPase activity, whereas we found up-regulation in patients with low values for these parameters after assist-device support.

CONCLUSIONS

Sarcoplasmic reticulum Ca(2+)-ATPase activity, which influences the myocardial Ca(2+)-transient, generally is not restored to normal values in assist-device-supported hearts, but depends on a combined score of the left ventricular end-diastolic diameter, degree of ventricular fibrosis, and age of the patient at the time of assist-device implantation.

Effects of dietary fatty acids on the composition and oxidizability of low-density lipoprotein

OBJECTIVE

The objective of this study was to compare the effects of dietary monounsaturated fatty acids (MUFA), n-6 and n-3 polyunsaturated fatty acids (PUFA) on LDL composition and oxidizability.

DESIGN, SETTING AND SUBJECTS

Sixty-nine healthy young volunteers, students at a nearby college, were included. Six subjects withdrew because of intercurrent illness and five withdrew because they were unable to comply with the dietary regimen.

INTERVENTIONS

The participants received a 2-week wash-in diet rich in saturated fatty acids (SFA) followed by diets rich in refined olive oil, rapeseed oil or sunflower oil for 4 weeks. Intakes of vitamin E and other antioxidants did not differ significantly between the diets.

RESULTS

At the end of the study, LDL oxidizability was lowest in the olive oil group (lag time: 72.6 min), intermediate in the rapeseed oil group (68.2 min) and highest in the sunflower oil group (60.4 min, P<0.05 for comparison of all three groups). Despite wide variations in SFA intake, the SFA content of LDL was not statistically different between the four diets (25.8-28.5% of LDL fatty acids). By contrast, the PUFA (43.5%-60.5% of LDL fatty acids) and MUFA content of LDL (13.7-29.1% of LDL fatty acids) showed a wider variability dependent on diet.

CONCLUSIONS

Enrichment of LDL with MUFA reduces LDL susceptibility to oxidation. As seen on the rapeseed oil diet this effect is independent of a displacement of higher unsaturated fatty acids from LDL. Evidence from this diet also suggests that highly unsaturated n-3 fatty acids in moderate amounts do not increase LDL oxidizability when provided in the context of a diet rich in MUFA.