<p>Calcineurin is both necessary and sufficient to induce cardiac hypertrophy, an independent risk factor for arrhythmia, dilated cardiomyopathy, heart failure, and sudden cardiac death. However, current knowledge of the downstream effectors of calcineurin is limited. My study utilizes <italic>Drosophila melanogaster</italic> to 1) establish a reliable model for discovering novel modifiers of calcineurin-induced cardiomyopathy; and 2) discover and characterize novel modifiers of calcineurin-induced cardiomyopathy.</p><p>In this study, I generated sensitized <italic>Drosophila</italic> lines expressing constitutively active calcineurin (CanA<super>act</super>) that was either fused to yellow fluorescent protein (YFP) or a Flag epitope (Flag-tagged) specifically in the heart using the cardiac-specific tinC driver (<italic>tinC-CanA<super>act</super></italic>). These sensitized lines displayed significant cardiac enlargement as assayed via optical coherence tomography (OCT), histology, and confocal microscopy. The feasibility of this method was established by testing <italic>Drosophila</italic> expressing deficiency of a known calcineurin modifier, Mef2. </p><p>Employing a targeted deficiency screen informed by calcineurin modifier screens in the eye and mesoderm, Galactokinase (<italic>Galk</italic>) was discovered as a novel modifier of calcineurin-induced cardiomyopathy in the fly through 1) genetic deficiencies, transposable elements, and RNAi disrupting <italic>Galk</italic> expression rescued <italic>tinC-CanA<super>act</super></italic>-induced cardiomyopathy; and 2) transposable element in <italic>Galk</italic> rescued <italic>tinC-CanA<super>act</super></italic>-induced decreased life span. Further characterization identified that the genetic disruption of <italic>Galk</italic> rescued CanA<super>act</super>-induced phenotypes driven in the posterior wing, but not ectodermaly, mesodermaly, or ubiquitously driven phenotypes. In a separate region, genetic disruption of the galactoside-binding lectin, galectin, was also found to rescue <italic>tinC-CanA<super>act</super></italic>-induced cardiac enlargement.</p><p>Together, these results characterize <italic>tinC-CanA<super>act</super></italic>-induced cardiac enlargement in the fly, establish that the <italic>tinC-CanA<super>act</super></italic> sensitized line is a reliable model for discovering novel calcineurin regulators and suggest that galactokinase and galectin-regulated glycosylation is important for calcineurin-induced cardiomyopathy. These results have the potential to provide insight into new treatments for cardiac hypertrophy.</p> / Dissertation

Die weltweite Zunahme der Prävalenz von Übergewicht und Adipositas und den damit verbundenen medizinischen und sozioökonomischen Herausforderungen stellt eine der wesentlichen Herausforderungen der modernen medizinischen Versorgung dar. Im Mittelpunkt stehen dabei insbesondere die Auswirkungen von Übergewicht und Adipositas auf das kardiovaskuläre System und den damit verbundenen funktionellen und strukturellen Veränderungen der kardiovaskulären Funktion. Als Mediatoren dieser funktionellen und strukturellen Veränderungen stehen dabei zunehmend Adipozytokine im Interesse wissenschaftlicher Arbeiten. Unter Adipozytokinen versteht man in diesem Zusammenhang einen Sammelbegriff für von Adipozyten und anderen Fettgewebszellen sezernierten autokrin-, endokrin- und parakrin wirkenden bioaktiven Molekülen. Insbesondere bei Übergewicht und Adipositas kommt es zu einer charakteristischen Veränderung im Sekretionsmuster dieser Adipozytokine. Die Wirkung einzelner Adipozytokine auf die kardiovaskuläre Funktion wurde in den letzten Jahren intensiv untersucht, über die Wirkung ganzer Adipozytokinprofile ist bisher jedoch nur wenig bekannt. Ziel der vorliegenden Arbeit war es zu klären, welchen Einfluss eine 24-stündige Behandlung von neonatalen ventrikulären Kardiomyozyten mit einem physiologischen Adipozytokin-Profil auf Hypertrophie-assoziierte Signalwege und Zellproteine hat.

Die weltweite Zunahme der Prävalenz von Übergewicht und Adipositas und den damit verbundenen medizinischen und sozioökonomischen Herausforderungen stellt eine der wesentlichen Herausforderungen der modernen medizinischen Versorgung dar. Im Mittelpunkt stehen dabei insbesondere die Auswirkungen von Übergewicht und Adipositas auf das kardiovaskuläre System und den damit verbundenen funktionellen und strukturellen Veränderungen der kardiovaskulären Funktion. Als Mediatoren dieser funktionellen und strukturellen Veränderungen stehen dabei zunehmend Adipozytokine im Interesse wissenschaftlicher Arbeiten. Unter Adipozytokinen versteht man in diesem Zusammenhang einen Sammelbegriff für von Adipozyten und anderen Fettgewebszellen sezernierten autokrin-, endokrin- und parakrin wirkenden bioaktiven Molekülen. Insbesondere bei Übergewicht und Adipositas kommt es zu einer charakteristischen Veränderung im Sekretionsmuster dieser Adipozytokine. Die Wirkung einzelner Adipozytokine auf die kardiovaskuläre Funktion wurde in den letzten Jahren intensiv untersucht, über die Wirkung ganzer Adipozytokinprofile ist bisher jedoch nur wenig bekannt. Ziel der vorliegenden Arbeit war es zu klären, welchen Einfluss eine 24-stündige Behandlung von neonatalen ventrikulären Kardiomyozyten mit einem physiologischen Adipozytokin-Profil auf Hypertrophie-assoziierte Signalwege und Zellproteine hat.

Cardiac hypertrophy leading to heart failure remains a leading cause of morbidity and mortality in the 21st century despite major therapeutic advances. Improved understanding of novel molecular and cellular processes contributing to cardiac hypertrophy therefore continues to be important. Cyclin-dependent Kinase 9 (CDK9), part of a family of proteins controlling cell cycle and growth, has emerged as one such potential candidate over the last 5 years. CDK9 is the catalytic subunit of the CDK9/CyclinT complex and acts by phosphorylating the carboxy-terminal domain of RNA polymerase II. Hypertrophic signals, such as Endothelin-1 (ET-1) and phenylephrine, have been shown to cause CDK9 activation leading to a hypertrophic response in cultured mouse cardiomyocytes associated with reactivation of the foetal gene program. CDK9 also forms a complex with GATA4 to play a role in differentiation of mouse ES cells into cardiomyocytes. These findings suggest a specific role for CDK9 in controlling growth and differentiation of cardiomyocytes and merits further study in models where cardiomyocyte differentiation and proliferation are key contributors. In contrast to mammals, zebrafish retain a high cardiomyocyte proliferative capacity throughout their life span and can readily repair following injury. I have examined the role of CDK9 on global and cardiac development in the zebrafish embryo. I have also assessed the impact of CDK9 manipulation on response to ventricle injury using a laser-induced injury model developed and validated as part of my thesis. My findings confirm that normal growth of the embryonic ventricle is associated with a rapid increase in cardiomyocyte number, that was of 50% in the period 96-120 hpf, accompanied by increasing chamber trabeculation. This is also characterized by an increase in the gene expression of most of cardiac development relevant transcription factors, i.e. GATA4, 5 and 6, and MEF2c. The significant reduced cardiovascular function (14% of Ejection Fraction compared to 20% in controls) at 2 h post laser injury in the zebrafish embryonic heart promptly recovers at 24 hour post-laser, accompanied by acceleration of cardiomyocyte proliferation, that increased of 49% in injured ventricles compared to 20% in controls in the period 2-24 h post-laser. Pharmacological and genetic inhibition of CDK9 activity also significantly reduced cardiac growth, cardiomyocyte number, ventricle function and impairs functional recovery following laser injury. Conversely, genetic inhibition of LARP7, a CDK9 repressor, resulted in increased cardiomyocyte number and was associated with full functional and cellular recovery following laser-injury. In conclusion, I have provided evidence, in the zebrafish embryonic heart, that CDK9 plays an important role in cardiac growth and development and impacts significantly on cardiomyocyte proliferation. I have also shown that CDK9 manipulation significantly affects cellular and functional recovery following laser-induced injury. Further studies are required to further define the role of CDK9 and LARP7 in the heart and develop therapeutic strategies using this pathway that could contribute to cellular repair mechanisms in the adult mammalian heart.

The incidence of cardiovascular diseases including cardiac hypertrophy and failure in pre-menopausal women is lower compared to age-matched men but the risk of heart disease increases substantially after the onset of menopause. It has been postulated that female sex hormones play an important role in cardiovascular health in pre-menopausal women. In animal studies including spontaneously hypertensive (SHR) rats, the development of cardiac hypertrophy is attenuated by 17&#946;-estradiol treatment. Cardiac energy metabolism is crucial for normal function of the heart. In cardiac hypertrophy and heart failure, the myocardium undergoes a metabolic shift from fatty acid as primary cardiac energy source to glucose, which re-introduces the fetal type of metabolism that representing the glucose as a major source of energy. Many studies have reported that the disruption of the balance between glucose and fatty acid metabolism plays an important role in cardiac pathologies including hypertrophy, heart failure, diabetes, dilative cardiomyopathy and myocardial infarction. Glucose enters cardiomyocytes via GLUT1 and GLUT4 glucose transporters and GLUT4 is the major glucose transporter which is insulin-dependent. Cardiac-selective GLUT4 deficiency leads to cardiac hypertrophy. This shows that the decrease in cardiac glucose uptake may play a direct role in the pathogenesis of cardiac hypertrophy. Estrogens modulate glucose homeostasis in the liver and the skeletal muscle. But it is not known whether estrogens affect also cardiac glucose uptake which could provide another mechanism to explain the prevention of cardiac hypertrophy by female sex hormones. In the present study, SHR Rats were ovariectomized (OVX), not ovariectomized (sham) or ovariectomized and treated with subcutaneous 17&#946;-estradiol. After 6 weeks of treatment, body weight, the serum levels of estrogen, insulin, intra-peritoneal glucose tolerance test (IP-GTT), myocardial glucose uptake by FDG-PET (2-(18F)-fluoro-deoxyglucose (18FDG) and Positron Emission Tomography), cardiac glucose transporter expression and localization and cardiac hexokinase activity were analyzed. As results of this study, PET analysis of female SHR revealed decreased cardiac glucose uptake in OVX animals compared to intact that was normalized by estrogen supplementation. Interestingly, there was no change in global glucose tolerance among the treatment groups. Serum insulin levels and cardiac hexokinase activity were elevated by E2 substitution. The protein content of cardiac glucose transporters GLUT-4 and GLUT-1, and their translocation as determined by fractionation studies and immuno-staining did not show any significant change by ovariectomy and estrogen replacement. Also levels of insulin receptor substrate-1 (IRS-1) and its tyrosine phosphorylation, which is required for activation and translocation of GLUT4, was un-affected in all groups of SHR. Cardiac gene expression analysis in SHR heart showed that ei4Ebp1 and Frap1 genes which are involved in the mTOR signaling pathway, were differentially expressed upon estrogen treatment. These genes are known to be activated in presence of glucose in the heart. As a conclusion of this study, reduced myocardial FDG uptake in ovariectomized spontaneously hypertensive rat is normalized by 17&#946;-estradiol treatment. Increased myocardial hexokinase appears as a potential mechanism to explain increased myocardial glucose uptake by 17&#946;-estradiol. Increased cardiac glucose uptake in response to 17&#946;-estradiol in ovariectomized SHR may provide a novel mechanism to explain the reduction of cardiac hypertrophy in E2 treated SHR. Therefore, 17&#946;-estradiol improves cardiac glucose utilization in ovariectomized SHR which may give rise to possible mechanism for its protective effects against cardiac hypertrophy. / Erkrankungen des kardiovaskulären Systems, wie beispielsweise Herzhypertrophie oder Herzinsuffizienz treten bei Frauen vor der Menopause im Vergleich zu gleichaltrigen Männern seltener auf. Das Risiko für eine solche kardiovaskuläre Erkrankung steigt jedoch drastisch mit dem Beginn der Menopause an. Aus diesem Grund wird angenommen, dass weibliche Geschlechtshormone kardioprotektive Wirkungen besitzen. Tierstudien an spontan hypertensiven Ratten (SHR) haben belegt, dass eine Herzhypertrophie durch die Behandlung der Tiere mit 17&#946;-Estradiol abgemildert werden kann. Entscheidend für die Funktion des Myokards ist sein Energiemetabolimus, der sich im Verlauf einer Hypertrophie oder Herzinsuffizienz vom primären Fettsäurestoffwechsel auf Glucosemetabolismus umschaltet. Diese Situation entspricht der des fetalen Herzens. Viele Studien haben belegt, dass eine Störung der Balance zwischen Glucose- und Fettsäurestoffwechsel oftmals ein erstes Anzeichen für einen pathologischen Zustand des Herzens, wie z.B. Hypertrophie, Herzinsuffizienz, Diabetes, dilative Kardiomyopathie und Myokardinfarkt ist. Im gesunden Herzen gelangt Glucose über die zwei Glucosetransporter GLUT1 und GLUT4 in die Zellen des Myokards, wobei der insulinabhängige Glut4-Transporter der Hauptglucosetransporter ist. Eine GLUT4-Defizienz führt daher ebenfalls zu einer Herzhypertrophie was wiederum zeigt, dass eine verminderte Glucoseaufnahme im direkten Zusammenhang mit pathologischen Zuständen des Herzens steht. Bisherige Studien haben gezeigt, dass Östrogen an der Glucosehomöostase in Leber und Skelettmuskeln beteiligt ist. Jedoch ist wenig darüber bekannt, ob Östrogen ebenfalls in die kardiale Glucosehomöostase eingreift und inwiefern die kardioprotektive Wirkung des Östrogens in diesem Zusammenhang steht.In der vorliegenden Arbeit wurden weibliche SH-Ratten ovariektomiert (OVX), nicht ovariektomiert (sham) oder ovariektomiert und zusätzlich subkutan mit 17&#946;-Estradiol behandelt. Nach einer Behandlungszeit von 6 Wochen wurden dann das Körpergewicht, die Serumspiegel von Östrogen, Insulin und IPGTT bestimmt, und die Glucoseaufnahme des Myokards mittels FDG-PET analysiert. Zusätzlich wurden Expression und zelluläre Lokalisation der kardialen Glucosetransporter sowie die kardiale Hexokinaseaktivität untersucht. Es konnte gezeigt werden, dass sich eine verminderte Glucoseaufnahme des Herzens bei ovariektomierten Tieren durch Östrogen-Supplementation normalisieren lässt. Eine Abweichung bezüglich der Glucosetoleranz der einzelnen Gruppen konnte nicht beobachtet werden. Jedoch konnte ein erhöhter Insulinspiegel des Serums und eine erhöhte kardiale Aktivität des Enzyms Hexokinase durch die Behandlung mit Östrogen bei den ovariektomierten Tieren beschrieben werden. Durch Fraktionierungen und immunhistologische Untersuchungen konnte kein signifikanter Unterschied in Bezug auf die Menge sowie die Translokation der Glucosetransporter GLUT1 und GLUT4 im Myokard zwischen den einzelnen Behandlungen der Tiere beschrieben werden. Ferner konnte zwischen den einzelnen Tiergruppen auch kein Unterschied zwischen dem Insulin Rezeptor Substrat-1 (IRS-1) und seiner Tyrosin-phosphorylierten Form festgestellt werden, die für die Aktivierung und Translokation des GLUT4 benötigt werden. Analysen der Genexpression in den Herzen der SH-Ratten konnten allerdings zeigen, dass die Gene ei4Ebp1 und Frap1, die im mTOR Signalweg involviert sind, bei den Östrogen-supplementierten Tieren ein abweichendes Expressionsmuster aufweisen. Über diese Gene ist bekannt, dass sie in der Gegenwart von Glucose im Herzen aktiviert werden und bei der Entstehung einer Herzhypertrophie mitwirken. Basierend auf den PET-Analysen und der Hexokinaseaktivität lässt sich als Resultat dieser Arbeit aussagen, dass Östrogen die kardiale Glucoseaufnahme in SH-Ratten fördert. Diese Ergebnisse könnten einen Hinweis auf einen noch unbekannten Mechanismus geben, um die protektive Wirkung des Östrogens im Hinblick auf die Herzhypertrophie zu erklären. Hinsichtlich der Tatsache, dass keine Veränderungen in der Translokation der GLUT4-Transporter in der Plasmamembran bei den einzelnen Behandlungen der Tiere zu verzeichnen sind, jedoch Veränderungen der Glucoseaufnahme durch die PET-Analysen dargestellt werden konnten, besteht jedoch noch Erklärungsbedarf. Es liegen diverse Studien vor, die diesen Unterschied damit erklären könnten, dass der GLUT4-Transporter in einer inaktiven Form in der Plasmamembran vorliegt bis die Glucoseaufnahme durch den GLUT4-Transporter mittels der Insulin Signaltransduktionskaskade reguliert wird.

A hipertrofia cardíaca é um dos principais mecanismos de adaptação do coração frente a uma sobrecarga de trabalho e pode advir de estímulos patológicos como a hipertensão arterial levando a um prejuízo funcional ou por estímulos fisiológicos como o treinamento físico que por outro lado, promove adaptações benéficas no coração. Na última década uma nova classe de moléculas, os miRNAs, vem sendo estudada como reguladores da expressão gênica em diversos tipos celulares, inclusive os cardiomiócitos. Entretanto, estudos sobre a participação de miRNAs nas adaptações induzidas pelo treinamento físico ainda são escassos. O presente trabalho teve como principal objetivo avaliar o efeito do treinamento físico aeróbio no perfil de expressão de miRNAs no coração de ratos espontaneamente hipertensos (SHR) bem como selecionar miRNAs com padrão alterado no SHR e revertido pelo treinamento físico e analisar seu papel funcional através de aplicativos de bioinformática. Os animais foram divididos em três grupos: ratos espontaneamente hipertensos sedentários (SHR-S), SHR treinados (SHR-T) e um grupo normotenso sedentário (WKY-S). O grupo SHR-T desempenhou um protocolo de treinamento de natação de 60 minutos, 5 vezes por semana durante 10 semanas e com um sobrecarga de 5% do peso corporal na cauda. Foram feitas análises hemodinâmicas (pressão arterial, PA e freqüência cardíaca de repouso, FC), funcionais (capacidade física, consumo de oxigênio, ecocardiograma), bioquímicas a expressão de miRNAs (microarray, Real Time-PCR) e computacionais (predição de alvos e anotação de vias de sinalização). Os principais resultados foram: 1. A PA e FC reduziu no grupo SHR-T em relação aos animais sedentários; 2. A capacidade de tolerância ao esforço, VO2 pico aumentou no grupo SHR-T; 3. Análise ecocardiográfica mostrou que a onda E, Onda A e razão E/A melhoram no grupo SHR-T. 4. Análise de microarray encontrou 6 diferentes padrões no perfil de expressão de miRNAs na comparação dos grupos WKY-S, SHR-S e SHR-T; 5. 6 miRNAs alterados no SHR-S tiveram sua expressão revertida no SHR-T (miR-1, 22, 27a, 27b, 29c e 451); 7. Análise bioinformática mostrou que esse grupo de miRNAs tem como alvo predito diversas vias de sinalização relacionados com o remodelamento cardíaco como MAPK, TGF-beta e Wnt, além de vias relacionadas com estrutura do citoesqueleto e metabolismo energético. Em conclusão, nossos resultados sugerem que os miRNAs: 1, 22, 27a, 27b, 29c e 451 podem estar governando vias de sinalização celular envolvidas no processos de reversão do quadro patológico. Esse fato abre novas perspectivas a respeito da utilização dessas moléculas como forma de terapias / Cardiac hypertrophy is a major mechanism of adaptation of the heart by the increased workload and may result from pathological stimuli such as high blood pressure leading to functional impairment or by physiological stimuli such as physical training, that on other hand promotes beneficial adaptations on the heart. In the last decade a new class of molecules, miRNAs, has been studied as regulators of gene expression in different cell type, including cardiomyocytes. However, few studies have investigated the miRNAs involved in adaptations to physical training. This study aimed to evaluate the effect of aerobic exercise training on expression profiling of miRNAs in the heart of spontaneously hypertensive rats (SHR) as well as select miRNAs with altered pattern in SHR and reversed by physical training and analyze their functional role through bioinformatics applications. The animals were divided into 3 groups: sedentary hypertensive rats (SHR-S), trained SHR (SHR-T) and sedentary Wistar Kyoto rats (WKY-S). The SHR-T group performed a swimming training protocol of 60 minutes, 5 times a week for 10 weeks and with overload of 5% of body weight in the tail. We analyzed hemodynamic (blood pressure, BP and resting heart rate, HR), functional (physical capacity, oxygen consumption and echocardiogram), biochemical (microarray and Real Time-PCR to miRNAs) and computational (prediction of targets and annotation cell signaling pathways) parameters. The main findings were: 1. The BP and HR decreased in SHR-T group compared to the sedentary animals; 2. The exercise tolerance and peak VO2 increased in SHR-T group; 3.Echocardiographic analysis showed that the E wave, A wave and E/A ratio improved in SHR-T group; 4. Microarray analysis found six different miRNAs expression profile in the comparison groups WKY-S, SHR-S and SHR-T; 5. Six miRNAs were altered in SHR-S and were reversed in the SHR-T (miR-1,22, 27a, 27b, 29c and 451); 7. Bioinformatics analysis showed that this miRNA cluster has multiple predicted targets in signaling pathways related to cardiac remodeling as MAPK, Wnt and TGF-beta and others genes associate to cytoskeletal structure and energetic metabolism. In conclusion, our results suggest that miRNAs: 1, 22, 27a, 27b, 29c and 451 can be controlling cell signaling pathways involved in the process of reversing the disease. These results open new perspectives on the use of these molecules as a therapeutic treatment

The pathogenesis of heart failure (HF) involves compensatory left ventricular hypertrophy. Reactive oxygen species (ROS) are elevated in HF and mediate myocardial hypertrophy. ROS also mediate formation of lipid peroxidation byproducts, yet little is known about their role in promoting hypertrophy. One lipid peroxidation byproduct, 4-hydroxy-trans-2-nonenal (HNE) is a reactive aldehyde that forms covalent adducts on proteins. HNE levels are also elevated in HF and may mediate hypertrophy via HNE-adduct formation. LKB1 - a tumor suppressor protein - regulates cellular growth through activation of the downstream kinase AMPK. Activation of AMPK suppresses functions that consume ATP and simultaneously activates processes to generate energy. The LKB1 protein is inhibited by oxidants, but whether this results in myocardial hypertrophy is unclear. I hypothesized that HNE can directly promote cardiac hypertrophy via the modification of LKB1. In HEK293T cells I observed that HNE adducts inhibit activity of LKB1 through direct oxidative modification. Mutation of LKB1 Lys-96 or Lys-97 resulted in less HNE-LKB1 adduct formation. Mutation of LKB1 Lys-97 prevented the inhibitory effect of HNE, suggesting that HNE-adduction at this residue is sufficient to inhibit LKB1. In cardiomyocytes HNE inhibited both LKB1 and AMPK, increased phosphorylation of mTOR, p70S6K, and S6K, and increased protein synthesis. HNE also activated Erk1/2, which contributed to S6K activation but was not required for cellular growth. Hypertrophic S6K activation was dependent on mTOR. Mice fed a high-fat high-sucrose (HFHS) diet have myocardial hypertrophy that can be prevented by antioxidants. Hearts of HFHS mice have HNE-LKB1 adducts, inhibited LKB1 activity, yet no change in AMPK activation. Mice lacking aldehyde dehydrogenase 2 (ALDH2), an enzyme involved in HNE detoxification, have increased myocardial hypertrophy when fed HFHS diet yet have increased LKB1 activity. In summary HNE directly causes hypertrophy in cardiomyocytes. This occurs through inhibition of LKB1 and in part through Erk1/2 activation. In HFHS-fed mice HNE-LKB1 adduct formation is associated with decreased LKB1 activity. Impairing detoxification of reactive aldehydes in the ALDH2-KO mice is sufficient to increase myocardial hypertrophy, but this appears to be independent of LKB1. This study demonstrates a novel mechanism of cardiac hypertrophy caused by reactive aldehydes.

Tissues are not solely composed of cells. The extracellular matrix is important for the cell well-being and cell-cell communication. The glycosaminoglycan hyaluronan (HYA) is a widely distributed extracellular matrix (ECM) component. The molecule has prominent physicochemical properties, foremost viscoelastic and osmotic, but participates in many biological processes such as cell migration, proliferation, tissue turnover, wound healing and angiogenesis. HYA is synthesised by either of three different hyaluronan-synthesising enzymes, HAS1-3, and its main ligand is the transmembrane receptor CD44. In the heart and vessels the matrix components are of great importance for endurance and elasticity which are prerequisites for a normal function. The aims of the study were to describe the distribution of HYA and its receptor CD44 in normal cardiovascular tissue and to investigate the ECM composition in myocardial hypertrophy. Normal conditions were studied in a rat model. These studies showed that the tunica adventitia in almost all vessels stained strongly for HYA. The expression in the tunica intima and media on the venous side, differed between the vessels and was almost absent on the arterial side. In the adult animals only minute amounts of CD44 were detected. The expression of both HYA and CD44 was increased in newborn rats. In the heart HYA was unevenly distributed in the interstitium. Strong HYA-staining was seen in the valves and in the adventitia of intramyocardial vessels. Almost no CD44-staining was observed. Notably, there was no obvious difference between newborn and adult animals. In an experimental rat model of pressure-induced cardiac hypertrophy the mRNA-levels of HAS1, HAS2, CD44, basic Fibroblast Growth Factor (FGF-2) and Fibroblast Growth Factor Receptor-1 (FGFR-1) were elevated on day 1 after aortic banding. HAS2, CD44 and FGFR-1 were at basal levels on day 42. The HYA-concentration was significally elevated on day 1. HYA was detected in the interstitium by histochemistry and CD44 was detected mainly in and around the intramyocardial vessels. The HYA-staining was increased in myectomi specimens from patients with HCM compared to controls. HYA was detected in the interstitium, in fibrous septas and in the adventitia of intramyocardial vessels. No CD44 was detected in HCM or in control specimens. Our results indicate that HYA and CD44 play an active role in the maturing vessel tree and that the ECM content of HYA is increased in experimental myocardial hypertrophy and human hypertrophic cardiomyopathy.

No description available.

Cardiac hypertrophy is clinically defined as a relative increase in heart size associated with a thickening of the ventricular wall. It is a common feature of individuals suffering from different cardio-vascular or metabolic conditions and leads to heart failure. The structural, functional and molecular mechanisms which induce hypertrophy independent of hemodynamic alterations are poorly characterized. In this study, questions about whether cardiac-specific neuro-endocrine activation or metabolic imbalance are sufficient to induce hypertrophic structural and functional remodeling are addressed using genetically manipulated mouse models of primary cardiac hypertrophy. (For complete abstract open document)