elastin and Hypertrophy--Left-Ventricular

Zebrafish (Danio rerio) is widely used as an animal model to understand the pathophysiology of cardiovascular diseases. Here, we present the adult cardiac phenotype of weak atrium, myh6

Topics: Animals; Disease Models, Animal; Elastin; Heart Atria; Hyperplasia; Hypertrophy, Left Ventricular; Hypertrophy, Right Ventricular; Mutation; Myocytes, Cardiac; Myosin Heavy Chains; Zebrafish; Zebrafish Proteins

Development of right ventricular (RV) hypertension eventually contributes to RV and left ventricular (LV) myocardial fibrosis and dysfunction. The molecular mechanisms are not fully elucidated.. Pulmonary artery banding was used to induce RV hypertension in rats in vivo. Then, we evaluated cardiac function and regional remodeling 6 weeks after pulmonary artery banding. To further elucidate mechanisms responsible for regional cardiac remodeling, we also mimicked RV hypertensive stress by cyclic mechanical stretching applied to confluent cultures of cardiac fibroblasts, isolated from the RV free wall, septal hinge points, and LV free wall. Echocardiography and catheter evaluation demonstrated that rats in the pulmonary artery banding group developed RV hypertension with leftward septal displacement, LV compression, and increased LV end-diastolic pressures. Picrosirius red staining indicated that pulmonary artery banding induced marked RV fibrosis and dysfunction, with prominent fibrosis and elastin deposition at the septal hinge points but less LV fibrosis. These changes were associated with proportionally increased expressions of integrin-β1 and profibrotic signaling proteins, including phosphorylated Smad2/3 and transforming growth factor-β1. Moreover, mechanically stretched fibroblasts also expressed significantly increased levels of α-smooth muscle actin, integrin-β1, transforming growth factor-β1, collagen I deposition, and wrinkle formation on gel assays, consistent with myofibroblast transformation. These changes were not observed in parallel cultures of mechanically stretched fibroblasts, preincubated with the integrin inhibitor (BTT-3033).. Experimentally induced RV hypertension triggers regional RV, hinge-point, and LV integrin β1-dependent mechanotransduction signaling pathways that eventually trigger myocardial fibrosis via transforming growth factor-β1 signaling. Reduced LV fibrosis and preserved global function, despite geometrical and pressure aberrations, suggest a possible elastin-mediated protective mechanism at the septal hinge points.

Topics: Animals; Arterial Pressure; Cells, Cultured; Collagen Type I; Disease Models, Animal; Elastin; Fibrosis; Heart Ventricles; Hypertension, Pulmonary; Hypertrophy, Left Ventricular; Hypertrophy, Right Ventricular; Integrin beta1; Male; Mechanotransduction, Cellular; Pulmonary Artery; Rats, Sprague-Dawley; Transforming Growth Factor beta1; Ventricular Function, Left; Ventricular Function, Right; Ventricular Remodeling

Liver growth factor (LGF) is an endogenous albumin-bilirubin complex with antihypertensive effects in spontaneously hypertensive rats (SHR). We assessed the actions of LGF treatment on SHR mesenteric resistance and intramyocardial arteries (MRA and IMA, respectively), heart, and vascular smooth muscle cells (VSMC). SHR and Wistar-Kyoto (WKY) rats treated with vehicle or LGF (4.5 μg LGF/rat, 4 ip injections over 12 days) were used. Intra-arterial blood pressure was measured in anesthetized rats. The heart was weighted and paraffin-embedded. Proliferation, ploidy, and fibronectin deposition were studied in carotid artery-derived VSMC by immunocytochemistry. In MRA, we assessed: 1) geometry and mechanics by pressure myography; 2) function by wire myography; 3) collagen by sirius red staining and polarized light microscopy, and 4) elastin, cell density, nitric oxide (NO), and superoxide anion by confocal microscopy. Heart sections were used to assess cell density and collagen content in IMA. Left ventricular hypertrophy (LVH) regression was assessed by echocardiography. LGF reduced blood pressure only in SHR. LGF in vitro or as treatment normalized the alterations in proliferation and fibronectin in SHR-derived VSMC with no effect on WKY cells. In MRA, LGF treatment normalized collagen, elastin, and VSMC content and passive mechanical properties. In addition, it improved NO availability through reduction of superoxide anion. In IMA, LGF treatment normalized perivascular collagen and VSMC density, improving the wall-to-lumen ratio. Paired experiments demonstrated a partial regression of SHR LVH by LGF treatment. The effective cardiovascular antifibrotic and regenerative actions of LGF support its potential in the treatment of hypertension and its complications.

Topics: Analysis of Variance; Animals; Antihypertensive Agents; Bilirubin; Blood Pressure; Cell Proliferation; Cells, Cultured; Collagen; Coronary Vessels; Disease Models, Animal; Dose-Response Relationship, Drug; Elastin; Extracellular Matrix; Fibronectins; Fibrosis; Hypertension; Hypertrophy, Left Ventricular; Immunohistochemistry; Male; Mesenteric Arteries; Microscopy, Confocal; Microscopy, Polarization; Muscle, Smooth, Vascular; Myocardium; Myocytes, Smooth Muscle; Myography; Nitric Oxide; Nitric Oxide Synthase; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Serum Albumin; Serum Albumin, Human; Superoxides; Ultrasonography; Vascular Resistance; Vasodilation; Vasodilator Agents; Ventricular Remodeling

Despite extensive strides in understanding pressure overload induced heart failure, there is very little known about oxidative stress induced matrix metalloproteinase (MMP) activation, collagen degradation and remodeling in pressure overload heart failure. We hypothesize that pressure overload leads to redox imbalance causing increased expression/activity of MMP-2/9 producing collagen degradation and heart failure. To test this hypothesis, we created pressure overload heart failure by abdominal aortic stenosis (AS) in wild-type C57BL/6J and collagen mutant (Col1a1 with 129 s background) mice. At 4 weeks, post surgery, functional parameters were measured. Left ventricle (LV) tissue sections were analyzed by histology, Western Blot and PCR. The results suggest an increase in iNOS with a decrease in eNOS, an increase in nitrated protein modification and depletion of antioxidants thioredoxin and SOD in pressure overload. MMP-2/9 expression/activity and collagen degradation were increased in the AS animals. To determine whether a mutation in the collagen gene at the site of MMP cleavage mitigates cardiac hypertrophy, we used Col1a1 mice. In these mice, the AS induced LV hypertrophy (LVH) was ameliorated. In conclusion, our results suggest that AS leads to increased oxidative stress, expression/activity of MMP-2/9 and a decrease in antioxidant expression producing collagen degradation and heart failure.

Topics: Analysis of Variance; Animals; Aortic Valve Stenosis; Blood Pressure; Blotting, Western; Chronic Disease; Collagen; Disease Models, Animal; Echocardiography; Elastin; Electrocardiography; Enzyme Activation; Heart Failure; Hypertrophy, Left Ventricular; Male; Matrix Metalloproteinase 2; Matrix Metalloproteinase 9; Mice; Mice, Inbred C57BL; Mice, Mutant Strains; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Oxidative Stress; Research Design; Reverse Transcriptase Polymerase Chain Reaction; Stroke Volume; Ventricular Dysfunction, Left

Elevated oxidative stress has been characterized in numerous disorders including systemic hypertension, arterial stiffness, left ventricular hypertrophy (LVH) and heart failure. The peroxisome proliferator activated receptor gamma (PPARgamma) ameliorates oxidative stress and LVH. To test the hypothesis that PPARgamma decreased LVH and cardiac fibrosis in chronic pressure overload, in part, by increasing SOD, eNOS and elastin and decreasing NOX4, MMP and collagen synthesis and degradation, chronic pressure overload analogous to systemic hypertension was created in C57BL/6J mice by occluding the abdominal aorta above the kidneys (aortic stenosis-AS). The sham surgery was used as controls. Ciglitazone (CZ, a PPARgamma agonist, 4 microg/ml) was administered in drinking water. LV function was measured by M-Mode Echocardiography. We found that PPARgamma protein levels were increased by CZ. NOX-4 expression was increased by pressure-overload and such an increase was attenuated by CZ. SOD expression was not affected by CZ. Expression of iNOS was induced by pressure-overload, and such an increase was inhibited by CZ. Protein levels for MMP2, MMP-9, MMP-13 were induced and TIMP levels were decreased by pressure-overload. The CZ mitigated these levels. Collagen synthesis was increased and elastin levels were decreased by pressure-overload and CZ ameliorated these changes. Histochemistry showed that CZ inhibited interstitial and perivascular fibrosis. Echocardiography showed that CZ attenuated the systolic and diastolic LV dysfunction induced by pressure-overload. These observations suggested that CZ inhibited pressure-overlaod-induced cardiac remodeling, and inhibition of an induction of NOX4, iNOS, MMP-2/MMP-13 expression and collagen synthesis/degradation may play a role in pressure-overload induced cardiac remodeling.

Topics: Animals; Collagen; Elastin; Fibrosis; Heart; Hypertension; Hypertrophy, Left Ventricular; Hypoglycemic Agents; Male; Matrix Metalloproteinases; Mice; Mice, Inbred C57BL; Myocardium; NADPH Oxidase 4; NADPH Oxidases; Nitric Oxide Synthase Type III; Oxidative Stress; PPAR gamma; Superoxide Dismutase; Thiazolidinediones; Ventricular Remodeling

After a myocardial infarction, the injured region becomes fibrotic and the myocardial scar may expand if the ventricular wall lacks elasticity. Cardiac dilatation may precipitate the vicious cycle of progressive heart failure. The present study evaluated the functional benefits of increasing elastin within a myocardial scar using cell based gene therapy.. A myocardial infarction was generated by ligation of the left anterior descending artery in rats. Six days later, 2 x 10(6) syngeneic rat endothelial cells transfected with the rat elastin gene (elastin group, n=14) or an empty plasmid (control group, n=14) were transplanted into the infarct scar. Cardiac function, left ventricular (LV) volume, and infarct size were monitored over 3 months by echocardiography, Langendorff measurements, and planimetry. Elastin deposition was evaluated in the cells and in the infarct region by Western blot assay and by histological examination. Recombinant elastin was found in the scar in the elastin group but not the control group during the 3 months after cell transplantation. Histological assessment demonstrated organized elastic fibers within the infarct region. LV volume and infarct size were significantly smaller (P<0.05) in the elastin group than in the control group. Cardiac function evaluated by echocardiography and during Langendorff perfusion was significantly better (P<0.05) in the elastin group than in the control group.. Expressing recombinant elastin within the myocardial scar reduced scar expansion and prevented LV enlargement after a myocardial infarction. Altering matrix remodeling after an infarct preserved the LV function for at least 3 months.

Topics: Animals; Cells, Cultured; Cicatrix; Drug Evaluation, Preclinical; Elastin; Endothelial Cells; Extracellular Matrix; Genetic Therapy; Heart Failure; Hypertrophy, Left Ventricular; Male; Myocardial Infarction; Myocardium; Random Allocation; Rats; Rats, Inbred Lew; Recombinant Fusion Proteins; Single-Blind Method; Transfection; Ultrasonography; Ventricular Function, Left; Ventricular Remodeling

Extracellular matrix, particularly type I fibrillar collagen, provides tensile strength that allows cardiac muscle to perform systolic and diastolic functions. Collagen is induced during the transition from compensatory hypertrophy to heart failure. We hypothesized that cardiac stiffness during decompensatory hypertrophy is partly due to a decreased elastin:collagen ratio.. We prepared left ventricular tissue homogenates from spontaneously hypertensive rats (SHR) aged 30-36 weeks, which had compensatory hypertrophy with no heart failure, and from SHR aged 70-92 weeks, which had decompensatory hypertrophy with heart failure. Age- and sex-matched Wistar-Kyoto (WKY) rats were used as normotensive controls. In both SHR groups, increased levels of collagen were detected by immuno-blot analysis using type I collagen antibody. Elastin and collagen were quantitated by measuring desmosine/isodesmosine and hydroxyproline spectrophometrically, respectively. To determine whether the decrease in elastin content was due to increased elastinolytic activity of matrix metalloproteinase-2, we performed gelatin and elastin zymography on left ventricular tissue homogenates from control rats, SHR with compensatory hypertrophy and SHR with heart failure.. The elastin:collagen ratio was 0.242 +/- 0.008 in hearts from WKY rats. In SHR without heart failure, the ratio was decreased to 0.073 +/- 0.003 and in decompensatory hypertrophy with heart failure, the ratio decreased to 0.012 +/- 0.005. Matrix metalloproteinase-2 activity was increased significantly in SHR with heart failure compared with controls (P < 0.001). The level of tissue inhibitor of metalloproteinase-4 was increased in compensatory hypertrophy and markedly reduced in heart failure. Decorin was strongly reduced in decompensatory heart failure compared with control hearts.. Since collagen was induced in SHR with heart failure, decorin and elastin were decreased and the ratios of gelatinase A and elastase to tissue inhibitor of metalloproteinase-4 were increased, we conclude that heart failure is associated with adverse extracellular matrix remodeling.

Topics: Animals; Blotting, Western; Collagen; Decorin; Disease Models, Animal; Disease Progression; Elastin; Extracellular Matrix; Extracellular Matrix Proteins; Follow-Up Studies; Gelatinases; Heart Failure; Heart Ventricles; Hypertrophy, Left Ventricular; Matrix Metalloproteinase 2; Metalloendopeptidases; Myocardial Contraction; Proteoglycans; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Spectrophotometry; Tensile Strength; Tissue Inhibitor of Metalloproteinases; Transforming Growth Factor beta

We investigated possible links between left ventricular mass and central arterial elasticity in the adult spontaneously hypertensive rat (SHR) and in a subgroup of SHR in which blood pressure was normalized by chronic antihypertensive drug treatment; results were compared with those of age-matched normotensive Wistar-Kyoto rats. Two indexes of arterial elasticity, based on the measurement of aortic pressure pulse wave velocity, were used. First, the slope relating carotidofemoral pulse wave velocity to blood pressure in the phenylephrine-infused pithed preparation was used as a pressure-independent index of wall elasticity. Second, to account for hypertension- and treatment-induced aortic remodeling, elastic modulus was determined from the pulse wave velocity recorded when blood pressure reached that measured in awake animals before anesthesia and pithing, together with values for wall thickness and lumen diameter evaluated by histomorphometric analysis after in situ fixation at the same pressure. In control SHR, regression analysis of variance revealed significant correlations between left ventricular mass and both wave velocity/pressure slope and elastic modulus. Chronic antihypertensive treatment normalized all three parameters. In conclusion, this new technique provides experimental evidence of a link between left ventricular mass and central arterial elasticity.

Topics: Animals; Aorta, Thoracic; Blood Pressure; Body Weight; Calcium; Elastin; Hemodynamics; Hypertension; Hypertrophy, Left Ventricular; Male; Organ Size; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Vascular Capacitance

The effect of genetic hypertension and of chronic therapy by calcium entry blocker (CEB, isradipine) on the function and structure of large arteries has been studied in adult spontaneously hypertensive rats (SHR, n = 30) and in their normotensive control Wistar-Kyoto (WKY) rats (n = 30).. Fifteen-week-old rats were randomly allocated to treatment with isradipine (3 mg/kg subcutaneously once a day) or to placebo and followed for 12 weeks. Hemodynamic parameters, including instantaneous pressure and aortic velocity, were recorded under anesthesia at the end of the treatment period. Passive mechanical properties of carotid arteries were measured in situ in the presence or the absence of smooth muscle cell activity (potassium cyanide poisoning). Histomorphometric parameters of the carotid and aortic media, including cross-sectional area, medial thickness, nucleus density and size, and medial contents of proteins of interstitial matrix, were measured by an automated morphometric system. Untreated SHRs had greater peripheral resistance, stiffer and thicker arterial walls because of smooth muscle cell hyperplasia (thoracic aorta and carotid artery) and/or hypertrophy (thoracic aorta), and increased collagen content than did normotensive control rats. SHRs showed a significant left ventricular hypertrophy. For the whole duration of treatment, treatment with CEB normalized the arterial pressure in SHRs. We observed a significant decrease in peripheral resistance, increased cardiac output, and left ventricular contractility without significant reduction in left ventricular hypertrophy. Increases in diuresis and natriuresis were associated during the last week of treatment in both treated strains with marked increase in plasma renin activity; in contrast, urinary aldosterone was increased by treatment in WKY rats but not in SHRs. Arterial compliance was significantly increased by CEB under control and passive conditions. CEB induced a significant reduction in the medial hypertrophy of the aortic walls of SHRs and WKY rats associated with a reduction in medial hyperplasia. In the carotid artery, CEB reduced smooth muscle cell hypertrophy but did not affect the smooth muscle cell hyperplasia. Isradipine significantly reduced the arterial wall collagen contents in both strains, with marked increases in the elastin content in the carotid but not in the aortic wall.. These results suggest that (1) despite normalization of arterial pressure, chronic treatment with CEB in SHRs does not significantly reduce left ventricular hypertrophy, probably because of increase in myocardial contractility and/or increase in plasma renin activity; (2) mechanical properties of the arterial wall are normalized by treatment; and (3) remodeling of the arterial wall by CEB is not uniform according to the studied vessel.

Topics: Animals; Aorta; Biomechanical Phenomena; Carotid Arteries; Collagen; Compliance; Elastin; Hemodynamics; Hypertrophy, Left Ventricular; Isradipine; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Time Factors

To test the hypothesis that effects of angiotensin converting enzyme (ACE) inhibitors upon resistance vessel structure are responsible for their ability to cause long-term reduction in blood pressure.. Stroke-prone spontaneously hypertensive (SHRSP) and Wistar-Kyoto (WKY) rats were treated with enalapril or hydralazine from 4 to 15 weeks of age. Effects upon tail-cuff blood pressure, left ventricular hypertrophy and structural indices of the superior mesenteric artery (SMA) and its resistance vessels were assessed at 11 weeks of treatment and up to 11 weeks post-treatment.. Left ventricular hypertrophy was assessed by left ventricular weight:body weight ratios. Evidence of vascular structural change was obtained from tissue weight:body weight ratios, levels of RNA, DNA and expression of alpha-actin and elastin messenger (m)RNA.. The effects of enalapril and hydralazine upon left ventricular hypertrophy in SHRSP were consistent with their respective effects upon blood pressure. Both drugs prevented the development of medial hypertrophy in SMA and resistance vessels. This was accompanied by substantial reductions in RNA:DNA ratios. Alpha-actin mRNA levels were not affected by either drug but elastin mRNA levels were reduced by both drugs. During the first 12 days post-treatment there was evidence of structural change in SMA accompanying the increases in blood pressure but importantly not in the resistance vessels.. The effects of enalapril upon left ventricular hypertrophy and mesenteric arterial hypertrophy are totally consistent with responses to blood pressure and the persistence of structural changes post-treatment does not underlie the ability of the ACE inhibitors to persistently suppress hypertension.

Topics: Animals; Blood Pressure; Body Weight; DNA; Elastin; Enalapril; Heart Ventricles; Hydralazine; Hypertension; Hypertrophy, Left Ventricular; Male; Mesenteric Artery, Superior; Organ Size; Rats; Rats, Inbred SHR; Rats, Inbred WKY; RNA, Messenger; Vascular Resistance