Extracellular Tuning of Mitochondrial Respiration Leads to Aortic Aneurysm.

BACKGROUND: Marfan syndrome (MFS) is an autosomal dominant disorder of the connective tissue caused by mutations in the FBN1 (fibrillin-1) gene encoding a large glycoprotein in the extracellular matrix called fibrillin-1. The major complication of this connective disorder is the risk to develop thoracic aortic aneurysm. To date, no effective pharmacologic therapies have been identified for the management of thoracic aortic disease and the only options capable of preventing aneurysm rupture are endovascular repair or open surgery. Here, we have studied the role of mitochondrial dysfunction in the progression of thoracic aortic aneurysm and mitochondrial boosting strategies as a potential treatment to managing aortic aneurysms. METHODS: Combining transcriptomics and metabolic analysis of aortas from an MFS mouse model (Fbn1c1039g/+) and MFS patients, we have identified mitochondrial dysfunction alongside with mtDNA depletion as a new hallmark of aortic aneurysm disease in MFS. To demonstrate the importance of mitochondrial decline in the development of aneurysms, we generated a conditional mouse model with mitochondrial dysfunction specifically in vascular smooth muscle cells (VSMC) by conditional depleting Tfam (mitochondrial transcription factor A; Myh11-CreERT2Tfamflox/flox mice). We used a mouse model of MFS to test for drugs that can revert aortic disease by enhancing Tfam levels and mitochondrial respiration. RESULTS: The main canonical pathways highlighted in the transcriptomic analysis in aortas from Fbn1c1039g/+ mice were those related to metabolic function, such as mitochondrial dysfunction. Mitochondrial complexes, whose transcription depends on Tfam and mitochondrial DNA content, were reduced in aortas from young Fbn1c1039g/+ mice. In vitro experiments in Fbn1-silenced VSMCs presented increased lactate production and decreased oxygen consumption. Similar results were found in MFS patients. VSMCs seeded in matrices produced by Fbn1-deficient VSMCs undergo mitochondrial dysfunction. Conditional Tfam-deficient VSMC mice lose their contractile capacity, showed aortic aneurysms, and died prematurely. Restoring mitochondrial metabolism with the NAD precursor nicotinamide riboside rapidly reverses aortic aneurysm in Fbn1c1039g/+ mice. CONCLUSIONS: Mitochondrial function of VSMCs is controlled by the extracellular matrix and drives the development of aortic aneurysm in Marfan syndrome. Targeting vascular metabolism is a new available therapeutic strategy for managing aortic aneurysms associated with genetic disorders.

Neuron-derived orphan receptor-1 modulates cardiac gene expression and exacerbates angiotensin II-induced cardiac hypertrophy.

Hypertensive cardiac hypertrophy (HCH) is a common cause of heart failure (HF), a major public health problem worldwide. However, the molecular bases of HCH have not been completely elucidated. Neuron-derived orphan receptor-1 (NOR-1) is a nuclear receptor whose role in cardiac remodelling is poorly understood. The aim of the present study was to generate a transgenic mouse over-expressing NOR-1 in the heart (TgNOR-1) and assess the impact of this gain-of-function on HCH. The CAG promoter-driven transgenesis led to viable animals that over-expressed NOR-1 in the heart, mainly in cardiomyocytes and also in cardiofibroblasts. Cardiomyocytes from TgNOR-1 exhibited an enhanced cell surface area and myosin heavy chain 7 (Myh7)/Myh6 expression ratio, and increased cell shortening elicited by electric field stimulation. TgNOR-1 cardiofibroblasts expressed higher levels of myofibroblast markers than wild-type (WT) cells (α 1 skeletal muscle actin (Acta1), transgelin (Sm22α)) and were more prone to synthesise collagen and migrate. TgNOR-1 mice experienced an age-associated remodelling of the left ventricle (LV). Angiotensin II (AngII) induced the cardiac expression of NOR-1, and NOR-1 transgenesis exacerbated AngII-induced cardiac hypertrophy and fibrosis. This effect was associated with the up-regulation of hypertrophic (brain natriuretic peptide (Bnp), Acta1 and Myh7) and fibrotic markers (collagen type I α 1 chain (Col1a1), Pai-1 and lysyl oxidase-like 2 (Loxl2)). NOR-1 transgenesis up-regulated two key genes involved in cardiac hypertrophy (Myh7, encoding for ß-myosin heavy chain (ß-MHC)) and fibrosis (Loxl2, encoding for the extracellular matrix (ECM) modifying enzyme, Loxl2). Interestigly, in transient transfection assays, NOR-1 drove the transcription of Myh7 and Loxl2 promoters. Our findings suggest that NOR-1 is involved in the transcriptional programme leading to HCH.

p-SMAD2/3 and DICER promote pre-miR-21 processing during pressure overload-associated myocardial remodeling.

Transforming growth factor-ß (TGF-ß) induces miR-21 expression which contributes to fibrotic events in the left ventricle (LV) under pressure overload. SMAD effectors of TGF-ß signaling interact with DROSHA to promote primary miR-21 processing into precursor miR-21 (pre-miR-21). We hypothesize that p-SMAD-2 and -3 also interact with DICER1 to regulate the processing of pre-miR-21 to mature miR-21 in cardiac fibroblasts under experimental and clinical pressure overload. The subjects of the study were mice undergoing transverse aortic constriction (TAC) and patients with aortic stenosis (AS). In vitro, NIH-3T3 fibroblasts transfected with pre-miR-21 responded to TGF-ß1 stimulation by overexpressing miR-21. Overexpression and silencing of SMAD2/3 resulted in higher and lower production of mature miR-21, respectively. DICER1 co-precipitated along with SMAD2/3 and both proteins were up-regulated in the LV from TAC-mice. Pre-miR-21 was isolated bound to the DICER1 maturation complex. Immunofluorescence analysis revealed co-localization of p-SMAD2/3 and DICER1 in NIH-3T3 and mouse cardiac fibroblasts. DICER1-p-SMAD2/3 protein-protein interaction was confirmed by in situ proximity ligation assay. Myocardial up-regulation of DICER1 constituted a response to pressure overload in TAC-mice. DICER mRNA levels correlated directly with those of TGF-ß1, SMAD2 and SMAD3. In the LV from AS patients, DICER mRNA was up-regulated and its transcript levels correlated directly with TGF-ß1, SMAD2, and SMAD3. Our results support that p-SMAD2/3 interacts with DICER1 to promote pre-miR-21 processing to mature miR-21. This new TGFß-dependent regulatory mechanism is involved in miR-21 overexpression in cultured fibroblasts, and in the pressure overloaded LV of mice and human patients.

BAMBI (BMP and activin membrane-bound inhibitor) protects the murine heart from pressure-overload biomechanical stress by restraining TGF-ß signaling.

Left ventricular (LV) pressure overload is a major cause of heart failure. Transforming growth factors-ß (TGF-ßs) promote LV remodeling under biomechanical stress. BAMBI (BMP and activin membrane-bound inhibitor) is a pseudoreceptor that negatively modulates TGF-ß signaling. The present study tests the hypothesis that BAMBI plays a protective role during the adverse LV remodeling under pressure overload. The subjects of the study were BAMBI knockout mice (BAMBI(-/-)) undergoing transverse aortic constriction (TAC) and patients with severe aortic stenosis (AS). We examined LV gene and protein expression of remodeling-related elements, histological fibrosis, and heart morphology and function. LV expression of BAMBI was increased in AS patients and TAC-mice and correlated directly with TGF-ß. BAMBI deletion led to a gain of myocardial TGF-ß signaling through canonical (Smads) and non-canonical (TAK1-p38 and TAK1-JNK) pathways. As a consequence, the remodeling response to pressure overload in BAMBI(-/-) mice was exacerbated in terms of hypertrophy, chamber dilation, deterioration of long-axis LV systolic function and diastolic dysfunction. Functional remodeling associated transcriptional activation of fibrosis-related TGF-ß targets, up-regulation of the profibrotic micro-RNA-21, histological fibrosis and increased metalloproteinase-2 activity. Histological remodeling in BAMBI(-/-) mice involved TGF-ßs. BAMBI deletion in primary cardiac fibroblasts exacerbated TGF-ß-induced profibrotic responses while BAMBI overexpression in NIH-3T3 fibroblasts attenuated them. Our findings identify BAMBI as a critical negative modulator of myocardial remodeling under pressure overload. We suggest that BAMBI is involved in negative feedback loops that restrain the TGF-ß remodeling signals to protect the pressure-overloaded myocardium from uncontrolled extracellular matrix deposition in humans and mice.

Versican accumulation drives Nos2 induction and aortic disease in Marfan syndrome via Akt activation.

Thoracic aortic aneurysm and dissection (TAAD) is a life-threatening condition associated with Marfan syndrome (MFS), a disease caused by fibrillin-1 gene mutations. While various conditions causing TAAD exhibit aortic accumulation of the proteoglycans versican (Vcan) and aggrecan (Acan), it is unclear whether these ECM proteins are involved in aortic disease. Here, we find that Vcan, but not Acan, accumulated in Fbn1C1041G/+ aortas, a mouse model of MFS. Vcan haploinsufficiency protected MFS mice against aortic dilation, and its silencing reverted aortic disease by reducing Nos2 protein expression. Our results suggest that Acan is not an essential contributor to MFS aortopathy. We further demonstrate that Vcan triggers Akt activation and that pharmacological Akt pathway inhibition rapidly regresses aortic dilation and Nos2 expression in MFS mice. Analysis of aortic tissue from MFS human patients revealed accumulation of VCAN and elevated pAKT-S473 staining. Together, these findings reveal that Vcan plays a causative role in MFS aortic disease in vivo by inducing Nos2 via Akt activation and identify Akt signaling pathway components as candidate therapeutic targets.

BMP7-based peptide agonists of BMPR1A protect the left ventricle against pathological remodeling induced by pressure overload.

Aortic stenosis (AS) exposes the left ventricle (LV) to pressure overload leading to detrimental LV remodeling and heart failure. In animal models of cardiac injury or hemodynamic stress, bone morphogenetic protein-7 (BMP7) protects LV against remodeling by counteracting TGF-ß effects. BMP receptor 1A (BMPR1A) might mediate BMP7 antifibrotic effects. Herein we evaluated BMP7-based peptides, THR123 and THR184, agonists of BMPR1A, as cardioprotective drugs in a pressure overload model. We studied patients with AS, mice subjected to four-week transverse aortic constriction (TAC) and TAC release (de-TAC). The LV of AS patients and TAC mice featured Bmpr1a downregulation. Also, pSMAD1/5/(8)9 was reduced in TAC mice. Pre-emptive treatment of mice with THR123 and THR184, during the four-week TAC period, normalized pSMAD1/5/(8)9 levels in the LV, attenuated overexpression of remodeling-related genes (Col 1α1, ß-MHC, BNP), palliated structural damage (hypertrophy and fibrosis) and alleviated LV dysfunction (systolic and diastolic). THR184 administration, starting fifteen days after TAC, halted the ongoing remodeling and partially reversed LV dysfunction. The reverse remodeling after pressure overload release was facilitated by THR184. Both peptides diminished the TGF-ß1-induced hypertrophic gene program in cardiomyocytes, collagen transcriptional activation in fibroblasts, and differentiation of cardiac fibroblasts to myofibroblasts. Molecular docking suggests that both peptides bind with similar binding energies to the BMP7 binding domain at the BMPR1A. The present study results provide a preclinical proof-of-concept of potential therapeutic benefits of BMP7-based small peptides, which function as agonists of BMPR1A, against the pathological LV remodeling in the context of aortic stenosis.

Sirtuins: To Be or Not To Be in Diabetic Cardiomyopathy.

Diabetic cardiomyopathy is the leading cause of death among people with diabetes. Despite its severity and poor prognosis, there are currently no approved specific drugs to prevent or even treat diabetic cardiomyopathy. There is a need to understand the pathogenic mechanisms underlying the development of diabetic cardiomyopathy to design new therapeutic strategies. These mechanisms are complex and intricate and include metabolic dysregulation, inflammation, oxidative stress, fibrosis, and apoptosis. Sirtuins, a group of deacetylase enzymes, play an important role in all these processes and are, therefore, potential molecular targets for treating this disease. In this review, we discuss the role of sirtuins in the heart, focusing on their contribution to the pathogenesis of diabetic cardiomyopathy and how their modulation could be therapeutically useful.

Aortic disease in Marfan syndrome is caused by overactivation of sGC-PRKG signaling by NO.

Thoracic aortic aneurysm, as occurs in Marfan syndrome, is generally asymptomatic until dissection or rupture, requiring surgical intervention as the only available treatment. Here, we show that nitric oxide (NO) signaling dysregulates actin cytoskeleton dynamics in Marfan Syndrome smooth muscle cells and that NO-donors induce Marfan-like aortopathy in wild-type mice, indicating that a marked increase in NO suffices to induce aortopathy. Levels of nitrated proteins are higher in plasma from Marfan patients and mice and in aortic tissue from Marfan mice than in control samples, indicating elevated circulating and tissue NO. Soluble guanylate cyclase and cGMP-dependent protein kinase are both activated in Marfan patients and mice and in wild-type mice treated with NO-donors, as shown by increased plasma cGMP and pVASP-S239 staining in aortic tissue. Marfan aortopathy in mice is reverted by pharmacological inhibition of soluble guanylate cyclase and cGMP-dependent protein kinase and lentiviral-mediated Prkg1 silencing. These findings identify potential biomarkers for monitoring Marfan Syndrome in patients and urge evaluation of cGMP-dependent protein kinase and soluble guanylate cyclase as therapeutic targets.

Sex-Specific Regulation of miR-29b in the Myocardium Under Pressure Overload is Associated with Differential Molecular, Structural and Functional Remodeling Patterns in Mice and Patients with Aortic Stenosis.

Pressure overload in patients with aortic stenosis (AS) induces an adverse remodeling of the left ventricle (LV) in a sex-specific manner. We assessed whether a sex-specific miR-29b dysregulation underlies this sex-biased remodeling pattern, as has been described in liver fibrosis. We studied mice with transverse aortic constriction (TAC) and patients with AS. miR-29b was determined in the LV (mice, patients) and plasma (patients). Expression of remodeling-related markers and histological fibrosis were determined in mouse LV. Echocardiographic morpho-functional parameters were evaluated at baseline and post-TAC in mice, and preoperatively and 1 year after aortic valve replacement (AVR) in patients with AS. In mice, miR-29b LV regulation was opposite in TAC-males (down-regulation) and TAC-females (up-regulation). The subsequent changes in miR-29b targets (collagens and GSK-3ß) revealed a remodeling pattern that was more fibrotic in males but more hypertrophic in females. Both systolic and diastolic cardiac functions deteriorated more in TAC-females, thus suggesting a detrimental role of miR-29b in females, but was protective in the LV under pressure overload in males. Clinically, miR-29b in controls and patients with AS reproduced most of the sexually dimorphic features observed in mice. In women with AS, the preoperative plasma expression of miR-29b paralleled the severity of hypertrophy and was a significant negative predictor of reverse remodeling after AVR; therefore, it may have potential value as a prognostic biomarker.

SIRT3-mediated inhibition of FOS through histone H3 deacetylation prevents cardiac fibrosis and inflammation.

Sirtuin 3 (SIRT3) is a deacetylase that modulates proteins that control metabolism and protects against oxidative stress. Modulation of SIRT3 activity has been proposed as a promising therapeutic target for ameliorating metabolic diseases and associated cardiac disturbances. In this study, we investigated the role of SIRT3 in inflammation and fibrosis in the heart using male mice with constitutive and systemic deletion of SIRT3 and human cardiac AC16 cells. SIRT3 knockout mice showed cardiac fibrosis and inflammation that was characterized by augmented transcriptional activity of AP-1. Consistent with this, SIRT3 overexpression in human and neonatal rat cardiomyocytes partially prevented the inflammatory and profibrotic response induced by TNF-α. Notably, these effects were associated with a decrease in the mRNA and protein levels of FOS and the DNA-binding activity of AP-1. Finally, we demonstrated that SIRT3 inhibits FOS transcription through specific histone H3 lysine K27 deacetylation at its promoter. These findings highlight an important function of SIRT3 in mediating the often intricate profibrotic and proinflammatory responses of cardiac cells through the modulation of the FOS/AP-1 pathway. Since fibrosis and inflammation are crucial in the progression of cardiac hypertrophy, heart failure, and diabetic cardiomyopathy, our results point to SIRT3 as a potential target for treating these diseases.

Gender differences of echocardiographic and gene expression patterns in human pressure overload left ventricular hypertrophy.

Gender influence on left ventricular (LV) remodeling associated to aortic valve stenosis (AS) has been long recognized, but underlying myocardial gene expression patterns have not been explored. We studied whether sex differences in echocardiographic LV anatomy and function in AS patients are associated with specific changes in myocardial mRNA expression of remodeling proteins. AS (n=39) and control (n=23)patients were assessed echocardiographically, and LV myocardial mRNA levels were quantified by PCR. AS patients exhibit increased wall thicknesses and LV mass index (LVMI), but only men show chamber dilation.Collagens and fibronectin mRNA levels increased correlatively to transforming growth factor-beta1 (TGF-beta1). In AS women, collagen I upregulation was proportionally higher than other extracellular matrix (ECM)components. No changes in matrix metalloproteinase-2 and tissue inhibitor of metalloproteinase-2 were detected. Gene expressions of sarcomeric proteins (beta-myosin heavy chain and myosin light chain-2) and TGF-beta1 were directly correlated with each other. Myosin light chain-2 mRNA levels increased proportionally to the transvalvular gradient, but women did so in a greater extent than men for a given gradient. In women, the hypertrophic growth response, reflected by LVMI, was proportional to the expression of genes encoding sarcomeric proteins and TGF-beta1. In men, chamber dilation and deterioration of LVEF was proportional to collagens, fibronectin, and TGF-beta1 gene expression levels. We evidenced gender biased gene expression patterns of the intracellular TGF-beta pathways involving the Smad branch, but not the TAK-1 branch, that could contribute to the remodeling differences observed in AS men and women. Based on these findings, a gender specific therapeutic approach of pressure overload LV hypertrophy could be justified.

Experimental modelling of cardiac pressure overload hypertrophy: Modified technique for precise, reproducible, safe and easy aortic arch banding-debanding in mice.

Pressure overload left ventricular hypertrophy is a known precursor of heart failure with ominous prognosis. The development of experimental models that reproduce this phenomenon is instrumental for the advancement in our understanding of its pathophysiology. The gold standard of these models is the controlled constriction of the mid aortic arch in mice according to Rockman's technique (RT). We developed a modified technique that allows individualized and fully controlled constriction of the aorta, improves efficiency and generates a reproducible stenosis that is technically easy to perform and release. An algorithm calculates, based on the echocardiographic arch diameter, the intended perimeter at the constriction, and a suture is prepared with two knots separated accordingly. The aorta is encircled twice with the suture and the loop is closed with a microclip under both knots. We performed controlled aortic constriction with Rockman's and the double loop-clip (DLC) techniques in mice. DLC proved superiority in efficiency (mortality and invalid experiments) and more homogeneity of the results (transcoarctational gradients, LV mass, cardiomyocyte hypertrophy, gene expression) than RT. DLC technique optimizes animal use and generates a consistent and customized aortic constriction with homogeneous LV pressure overload morphofunctional, structural, and molecular features.

Conditional deletion of Rcan1 predisposes to hypertension-mediated intramural hematoma and subsequent aneurysm and aortic rupture.

Aortic intramural hematoma (IMH) can evolve toward reabsorption, dissection or aneurysm. Hypertension is the most common predisposing factor in IMH and aneurysm patients, and the hypertensive mediator angiotensin-II induces both in mice. We have previously shown that constitutive deletion of Rcan1 isoforms prevents Angiotensin II-induced aneurysm in mice. Here we generate mice conditionally lacking each isoform or all isoforms in vascular smooth muscle cells, endothelial cells, or ubiquitously, to determine the contribution to aneurysm development of Rcan1 isoforms in vascular cells. Surprisingly, conditional Rcan1 deletion in either vascular cell-type induces a hypercontractile phenotype and aortic medial layer disorganization, predisposing to hypertension-mediated aortic rupture, IMH, and aneurysm. These processes are blocked by ROCK inhibition. We find that Rcan1 associates with GSK-3ß, whose inhibition decreases myosin activation. Our results identify potential therapeutic targets for intervention in IMH and aneurysm and call for caution when interpreting phenotypes of constitutively and inducibly deficient mice.

Nitric oxide mediates aortic disease in mice deficient in the metalloprotease Adamts1 and in a mouse model of Marfan syndrome.

Heritable thoracic aortic aneurysms and dissections (TAAD), including Marfan syndrome (MFS), currently lack a cure, and causative mutations have been identified for only a fraction of affected families. Here we identify the metalloproteinase ADAMTS1 and inducible nitric oxide synthase (NOS2) as therapeutic targets in individuals with TAAD. We show that Adamts1 is a major mediator of vascular homeostasis, given that genetic haploinsufficiency of Adamts1 in mice causes TAAD similar to MFS. Aortic nitric oxide and Nos2 levels were higher in Adamts1-deficient mice and in a mouse model of MFS (hereafter referred to as MFS mice), and Nos2 inactivation protected both types of mice from aortic pathology. Pharmacological inhibition of Nos2 rapidly reversed aortic dilation and medial degeneration in young Adamts1-deficient mice and in young or old MFS mice. Patients with MFS showed elevated NOS2 and decreased ADAMTS1 protein levels in the aorta. These findings uncover a possible causative role for the ADAMTS1-NOS2 axis in human TAAD and warrant evaluation of NOS2 inhibitors for therapy.

Left ventricular volume shifts and aortic root expansion during isovolumic contraction.

BACKGROUND AND AIM OF THE STUDY: Aortic valve opening involves conformational changes of the aortic root, including the ventricular-aortic junction (VAJ), sinotubular junction (STJ), and cusps. Moreover, the aortic root is contiguous with the left ventricular outflow tract (LVOT), which changes diameter throughout the cardiac cycle. Aortic root expansion prior to valve opening facilitates outward displacement of aortic cusp attachments, which helps flatten the cusps, thereby reducing cusp stress and fatigue, ultimately enhancing functional valve durability. The mechanisms underlying aortic root expansion prior to valve opening, however, remain incompletely characterized. The study aim was to establish a link between such aortic root expansion and intraventricular volume shifts into the LVOT during isovolumic contraction (IVC). METHODS: Miniature radiopaque markers were implanted on the left ventricle, VAJ, STJ, and aortic cusps of six sheep. After one week, 3-D marker coordinates were obtained using biplane videofluoroscopy (60 Hz). Triangular areas at the VAJ and STJ were calculated; LV main chamber (non-LVOT) and LVOT volumes were calculated using multiple tetrahedra. End-diastole was defined as the peak of the electrocardiogram R-wave, and end-IVC when aortic cusp separation began. RESULTS: During IVC, blood within the left ventricle was redistributed to the LVOT: mean LVOT volume was increased (+0.2 +/- 0.1 ml, p = 0.009) as non-LVOT volume fell (-0.8 +/- 0.4 ml, p = 0.006). Concomitantly, the aortic root expanded as both VAJ and STJ areas increased (+0.23 +/- 0.12 cm2 (p = 0.005) and +0.25 +/- 0.14 cm2 (p = 0.007), respectively) prior to aortic cusp separation. CONCLUSION: Aortic root expansion prior to valve opening is closely related to intraventricular volume shifts into the LVOT during IVC. Such volume shifts may 'prime' the aortic valve for ejection. These findings expand our understanding of cardiac dynamics by showing that blood acts as a coupling link between various cardiac units. Preservation of these normal aortic root dynamics may enhance the efficacy and durability of aortic surgical interventions.

Infestation of a diabetic foot by Wohlfahrtia magnifica.

Myiasis is the infestation of animals or humans by larvae from some species of dipteran flies. Depending on the tissues invaded, the maggots of these insects can produce different diseases of the skin, or mucoses (ocular, genitourinary, and oropharyngeal). Wohlfahrtia magnifica is one of the species causing myiasis; although it is a real veterinary problem, it rarely infests humans and extraordinarily in the context we describe. We herein present the case of a diabetic patient diagnosed with class IV peripheral vascular disease (Fontaine classification) who suffered infestation by W. magnifica and the management given to this pathologic process. The patient consented to the publication of this report.

Extracellular heat shock protein 90 binding to TGFß receptor I participates in TGFß-mediated collagen production in myocardial fibroblasts.

The pathological remodeling heart shows an increase in left ventricular mass and an excess of extracellular matrix deposition that can over time cause heart failure. Transforming growth factor ß (TGFß) is the main cytokine controlling this process. The molecular chaperone heat shock protein 90 (Hsp90) has been shown to play a critical role in TGFß signaling by stabilizing the TGFß signaling cascade. We detected extracellular Hsp90 in complex with TGFß receptor I (TGFßRI) in fibroblasts and determined a close proximity between both proteins suggesting a potential physical interaction between the two at the plasma membrane. This was supported by in silico studies predicting Hsp90 dimers and TGFßRI extracellular domain interaction. Both, Hsp90aa1 and Hsp90ab1 isoforms participate in TGFßRI complex. Extracellular Hsp90 inhibition lessened the yield of collagen production as well as the canonical TGFß signaling cascade, and collagen protein synthesis was drastically reduced in Hsp90aa1 KO mice. These observations together with the significant increase in activity of Hsp90 at the plasma membrane pointed to a functional cooperative partnership between Hsp90 and TGFßRI in the fibrotic process. We propose that a surface population of Hsp90 extracellularly binds TGFßRI and this complex behaves as an active participant in collagen production in TGFß-activated fibroblasts. We also offer an in vivo insight into the role of Hsp90 and its isoforms during cardiac remodeling in murine aortic banding model suffering from pathological cardiac remodeling and detect circulating Hsp90 overexpressed in remodeling mice.

Myocardial and circulating levels of microRNA-21 reflect left ventricular fibrosis in aortic stenosis patients.

BACKGROUND: Various human cardiovascular pathophysiological conditions associate aberrant expression of microRNAs (miRNAs) and circulating miRNAs are emerging as promising biomarkers. In mice, myocardial miR-21 overexpression is related to cardiac fibrosis elicited by pressure overload. This study was designed to determine the role of myocardial and plasmatic miR-21 in the maladaptive remodeling of the extracellular matrix induced by pressure overload in aortic stenosis (AS) patients and the clinical value of miR-21 as a biomarker for pathological myocardial fibrosis. METHODS: In left ventricular biopsies from 75 AS patients and 32 surgical controls, we quantified the myocardial transcript levels of miR-21, miR-21-targets and ECM- and TGF-ß-signaling-related elements. miR-21 plasma levels were determined in 25 healthy volunteers and in AS patients. In situ hybridization of miR-21 was performed in myocardial sections. RESULTS: The myocardial and plasma levels of miR-21 were significantly higher in the AS patients compared with the controls and correlated directly with the echocardiographic mean transvalvular gradients. miR-21 overexpression was confined to interstitial cells and absent in cardiomyocytes. Using bootstrap validated multiple linear regression, the variance in myocardial collagen expression was predicted by myocardial miR-21 (70% of collagen variance) or plasma miR-21 (52% of collagen variance), together with the miR-21 targets RECK and PDCD4, and effectors of TGF-ß signaling. CONCLUSIONS: Our results support the role of miR-21 as a regulator of the fibrotic process that occurs in response to pressure overload in AS patients and underscore the value of circulating miR-21 as a biomarker for myocardial fibrosis.

Circulating levels of miR-133a predict the regression potential of left ventricular hypertrophy after valve replacement surgery in patients with aortic stenosis.

BACKGROUND: Myocardial microRNA-133a (miR-133a) is directly related to reverse remodeling after pressure overload release in aortic stenosis patients. Herein, we assessed the significance of plasma miR-133a as an accessible biomarker with prognostic value in predicting the reversibility potential of LV hypertrophy after aortic valve replacement (AVR) in these patients. METHODS AND RESULTS: The expressions of miR-133a and its targets were measured in LV biopsies from 74 aortic stenosis patients. Circulating miR-133a was measured in peripheral and coronary sinus blood. LV mass reduction was determined echocardiographically. Myocardial and plasma levels of miR-133a correlated directly (r=0.46, P<0.001) supporting the myocardium as a relevant source of plasma miR-133a. Accordingly, a significant gradient of miR-133a was found between coronary and systemic venous blood. The preoperative plasma level of miR-133a was higher in the patients who normalized LV mass 1 year after AVR than in those exhibiting residual hypertrophy. Logistic regression analysis identified plasma miR-133a as a positive predictor of the hypertrophy reversibility after surgery. The discrimination of the model yielded an area under the receiver operator characteristic curve of 0.89 (P<0.001). Multiple linear regression analysis revealed plasma miR-133a and its myocardial target Wolf-Hirschhorn syndrome candidate 2/Negative elongation factor A as opposite predictors of the LV mass loss (g) after AVR. CONCLUSIONS: Preoperative plasma levels of miR-133a reflect their myocardial expression and predict the regression potential of LV hypertrophy after AVR. The value of this bedside information for the surgical timing, particularly in asymptomatic aortic stenosis patients, deserves confirmation in further clinical studies.

Androgens contribute to sex differences in myocardial remodeling under pressure overload by a mechanism involving TGF-ß.

BACKGROUND: In clinical studies, myocardial remodeling in aortic valve stenosis appears to be more favorable in women than in men, even after menopause. In the present study, we assessed whether circulating androgens contribute to a less favorable myocardial remodeling under pressure overload in males. We examined sex-related differences in one-year-old male and female mice. Whereas male mice at this age exhibited circulating androgen levels within the normal range for young adults, the circulating estrogens in females were reduced. The contribution of gonadal androgens to cardiac remodeling was analyzed in a group of same-age castrated mice. METHODOLOGY/PRINCIPAL FINDINGS: Animals were subjected to transverse aortic constriction (TAC). Echocardiography was performed 2 weeks after TAC and myocardial mRNA levels of TGF-ßs, Smads 2 and 3, collagens, fibronectin, ß-myosin heavy chain and α-myosin heavy chain were determined by q-PCR. Protein detection of p-SMAD2/3 was performed by Western Blot. Histological staining of fibrosis was performed with picrosirius red and Masson's trichrome. Compared with females, males developed more severe tissue fibrosis, LV dilation and hemodynamic dysfunction. TAC-males showed higher myocardial expression levels of TGF-ßs and the treatment with a neutralizing antibody to TGF-ß prevented myocardial fibrosis development. Orchiectomy diminished TAC-induced up-regulation of TGF-ßs and TGF-ß target genes, and it also reduced fibrosis and hemodynamic dysfunction. The capability of androgens to induce TGF-ß expression was confirmed in NIH-3T3 fibroblasts and H9C2 cardiomyocytes exposed to dihydrotestosterone. CONCLUSIONS/SIGNIFICANCE: Our results indicate that circulating androgens are responsible for the detrimental effects in the myocardium of older male mice subjected to pressure overload through a mechanism involving TGF-ßs.