transforming-growth-factor-beta and Mitral-Valve-Insufficiency

Topics: Age Factors; Animals; Cardiovascular Diseases; Cell Movement; Endothelial Cells; Epithelial-Mesenchymal Transition; Extracellular Matrix; Heart Valves; Leukocyte Common Antigens; Mice; Mitral Valve; Mitral Valve Insufficiency; Models, Animal; Myocardial Infarction; Neovascularization, Physiologic; Sheep; Stress, Physiological; Transforming Growth Factor beta

In mitral valve prolapse (MVP), leaflet thickening has recently been suggested to be due, in addition to a myxomatous degeneration, to the presence of a superimposed tissue (SIT), defined as an additional fibrous layer on top of the original leaflet. The mechanisms of SIT formation are currently unknown. We hypothesized that SIT formation would result from excessive leaflet stress and we used a unique ex vivo model to assess the correlation between leaflet remodelling and the type and location of mechanical stress and to elucidate the mechanisms underlying SIT formation.. Human diseased mitral valves (MVs; n = 21) were histologically analysed for SIT formation and original leaflet thickening. The SIT comprised of various compositions of extracellular matrix and could reach more than 50% of total leaflet thickness. Original leaflet and SIT thickness did not show significant correlation (r = -0.27, P = 0.23), suggesting different regulatory mechanisms. To study the role of the mechanical environment on MV remodelling, mouse MV were cultured in their natural position in the heart and subjected to various haemodynamic conditions representing specific phases of the cardiac cycle and the MVP configuration. SIT formation was induced in the ex vivo model, mostly present on the atrial side, and clearly dependent on the duration, type, and extent of mechanical stress. Specific stainings and lineage tracing experiments showed that SIT comprises of macrophages and myofibroblasts and is associated with the activation of the transforming growth factor-beta and bone morphogenetic protein signalling pathways. Migration of valvular interstitial cells and macrophages through breakages of the endothelial cell lining contributed to SIT formation.. Mechanical stresses induce specific cellular and molecular changes in the MV that result in SIT formation. These observations provide the first insights in the mechanism of SIT formation and represent an initial step to identify potential novel and early treatment for MVP.

Topics: Aged; Animals; Bone Morphogenetic Proteins; Cell Movement; Endothelial Cells; Female; Hemodynamics; Humans; Macrophages; Male; Mechanotransduction, Cellular; Mice, Transgenic; Middle Aged; Mitral Valve; Mitral Valve Insufficiency; Mitral Valve Prolapse; Phosphorylation; Smad Proteins; Stress, Mechanical; Time Factors; Tissue Culture Techniques; Transforming Growth Factor beta

Transforming growth factor beta-activated kinase 1 (TAK1) is a highly conserved kinase protein encoded by MAP3K7, and activated by multiple extracellular stimuli, growth factors and cytokines. Heterozygous variants in MAP3K7 cause the cardiospondylocarpofacial syndrome (CSCFS) which is characterized by short stature, dysmorphic facial features, cardiac septal defects with valve dysplasia, and skeletal anomalies. CSCFS has been described in seven patients to date and its molecular pathogenesis is only partially understood. Here, the functional effects of the MAP3K7 c.737-7A > G variant, previously identified in a girl with CSCFS and additional soft connective tissue features, were explored. This splice variant generates an in-frame insertion of 2 amino acid residues in the kinase domain of TAK1. Computational analysis revealed that this in-frame insertion alters protein dynamics in the kinase activation loop responsible for TAK1 autophosphorylation after binding with its interactor TAB1. Co-immunoprecipitation studies demonstrate that the ectopic expression of TAK1-mutated protein impairs its ability to physically bind TAB1. In patient's fibroblasts, MAP3K7 c.737-7A > G variant results in reduced TAK1 autophosphorylation and dysregulation of the downstream TAK1-dependent signaling pathway. TAK1 loss-of-function is associated with an impaired TGFβ-mediated α-SMA cytoskeleton assembly and cell migration, and defective autophagy process. These findings contribute to our understanding of the molecular pathogenesis of CSCFS and might offer the rationale for the design of novel therapeutic targets.

Topics: Abnormalities, Multiple; Actins; Adaptor Proteins, Signal Transducing; Autophagy; Child; Cytoskeleton; Female; Fibroblasts; Hearing Loss, Bilateral; Humans; Loss of Function Mutation; MAP Kinase Kinase Kinases; Mitral Valve Insufficiency; Mutation; Osteosclerosis; Phosphorylation; Polymorphism, Single Nucleotide; Protein Binding; Signal Transduction; Transforming Growth Factor beta

Fstl1 (Follistatin-like 1) is a secreted protein that is expressed in the atrioventricular valves throughout embryonic development, postnatal maturation, and adulthood. In this study, we investigated the loss of Fstl1 in the endocardium/endothelium and their derived cells.. We conditionally ablated Fstl1 from the endocardial lineage using a transgenic Tie2-Cre mouse model. These mice showed a sustained Bmp and Tgfβ signaling after birth. This resulted in ongoing proliferation and endocardial-to-mesenchymal transition and ultimately in deformed nonfunctional mitral valves and a hypertrophic dilated heart. Echocardiographic and electrocardiographic analyses revealed that loss of Fstl1 leads to mitral regurgitation and left ventricular diastolic dysfunction. Cardiac function gradually deteriorated resulting in heart failure with preserved ejection fraction and death of the mice between 2 and 4 weeks after birth.. We report on a mouse model in which deletion of Fstl1 from the endocardial/endothelial lineage results in deformed mitral valves, which cause regurgitation, heart failure, and early cardiac death. The findings provide a potential molecular target for the clinical research into myxomatous mitral valve disease.

Topics: Animals; Bone Morphogenetic Proteins; Cell Lineage; Cell Proliferation; Disease Models, Animal; Disease Progression; Endocardium; Endothelial Cells; Epithelial-Mesenchymal Transition; Follistatin-Related Proteins; Genetic Predisposition to Disease; Heart Conduction System; Heart Failure; Integrases; Mice, Knockout; Mitral Valve; Mitral Valve Insufficiency; Mitral Valve Prolapse; Phenotype; Receptor, TIE-2; Signal Transduction; Time Factors; Transcription Factors; Transforming Growth Factor beta; Ventricular Dysfunction, Left; Ventricular Function, Left; Ventricular Remodeling

After myocardial infarction (MI), mitral valve (MV) tethering stimulates adaptive leaflet growth, but counterproductive leaflet thickening and fibrosis augment mitral regurgitation (MR), doubling heart failure and mortality. MV fibrosis post-MI is associated with excessive endothelial-to-mesenchymal transition (EMT), driven by transforming growth factor (TGF)-β overexpression. In vitro, losartan-mediated TGF-β inhibition reduces EMT of MV endothelial cells.. This study tested the hypothesis that profibrotic MV changes post-MI are therapeutically accessible, specifically by losartan-mediated TGF-β inhibition.. The study assessed 17 sheep, including 6 sham-operated control animals and 11 with apical MI and papillary muscle retraction short of producing MR; 6 of the 11 were treated with daily losartan, and 5 were untreated, with flexible epicardial mesh comparably limiting left ventricular (LV) remodeling. LV volumes, tethering, and MV area were quantified by using three-dimensional echocardiography at baseline and at 60 ± 6 days, and excised leaflets were analyzed by histopathology and flow cytometry.. Post-MI LV dilation and tethering were comparable in the losartan-treated and untreated LV constraint sheep. Telemetered sensors (n = 6) showed no significant losartan-induced changes in arterial pressure. Losartan strongly reduced leaflet thickness (0.9 ± 0.2 mm vs. 1.6 ± 0.2 mm; p < 0.05; 0.4 ± 0.1 mm sham animals), TGF-β, and downstream phosphorylated extracellular-signal-regulated kinase and EMT (27.2 ± 12.0% vs. 51.6 ± 11.7% α-smooth muscle actin-positive endothelial cells, p < 0.05; 7.2 ± 3.5% sham animals), cellular proliferation, collagen deposition, endothelial cell activation (vascular cell adhesion molecule-1 expression), neovascularization, and cells positive for cluster of differentiation (CD) 45, a hematopoietic marker associated with post-MI valve fibrosis. Leaflet area increased comparably (17%) in constrained and losartan-treated sheep.. Profibrotic changes of tethered MV leaflets post-MI can be modulated by losartan without eliminating adaptive growth. Understanding the cellular and molecular mechanisms could provide new opportunities to reduce ischemic MR.

Topics: Angiotensin II Type 1 Receptor Blockers; Animals; Disease Models, Animal; Echocardiography, Three-Dimensional; Endothelial Cells; Fibrosis; Humans; Losartan; Mitral Valve; Mitral Valve Insufficiency; Myocardial Infarction; Papillary Muscles; Sheep; Transforming Growth Factor beta; Ventricular Remodeling

Ischemic mitral regurgitation (MR) is classically ascribed to functional restriction of normal leaflets, but recent studies have suggested post-myocardial infarction (MI) mitral valve (MV) leaflet fibrosis and thickening, challenging valve normality. Progression of leaflet thickness post-MI has not been studied. We hypothesized that excessive MV remodeling post-MI contributes to MR. Our objectives are to characterize MV changes after MI and relate them to MR.. Three groups of 40 patients with serial echocardiograms over a mean of 23.4 months were identified from an echocardiography database: patients first studied early (6±12 days) and late (12±7 years) after an inferior MI and normal controls. MV thickness was correlated with MR. We studied the mechanisms for MV changes in a sheep model (6 apical MI versus 6 controls) followed for 8 weeks, with MV cellular and histopathologic analyses. Early post-MI, leaflet thickness was found to be similar to controls (2.6±0.5 vs 2.5±0.4 mm;. MV thickness increases post-MI and correlates with MR, suggesting an organic component to ischemic MR. MV fibrotic remodeling can indicate directions for future therapy.

Topics: Adaptation, Physiological; Aged; Aged, 80 and over; Animals; Biopsy; Collagen; Disease Models, Animal; Echocardiography, Doppler, Color; Epithelial-Mesenchymal Transition; Female; Fibrosis; Humans; Male; Middle Aged; Mitral Valve; Mitral Valve Insufficiency; Myocardial Infarction; Retrospective Studies; Sheep, Domestic; Time Factors; Transforming Growth Factor beta

Marfan syndrome (MFS) is a systemic disorder of connective tissue caused by mutations in fibrillin-1. Cardiac dysfunction in MFS has not been characterized halting the development of therapies of cardiac complication in MFS. We aimed to study the age-dependent cardiac remodeling in the mouse model of MFS FbnC1039G+/- mouse [Marfan heterozygous (HT) mouse] and its association with valvular regurgitation. Marfan HT mice of 2-4 mo demonstrated a mild hypertrophic cardiac remodeling with predominant decline of diastolic function and increased transforming growth factor-β canonical (p-SMAD2/3) and noncanonical (p-ERK1/2 and p-p38 MAPK) signaling and upregulation of hypertrophic markers natriuretic peptides atrium natriuretic peptide and brain natriuretic peptide. Among older HT mice (6-14 mo), cardiac remodeling was associated with two distinct phenotypes, manifesting either dilated or constricted left ventricular chamber. Dilatation of left ventricular chamber was accompanied by biochemical evidence of greater mechanical stress, including elevated ERK1/2 and p38 MAPK phosphorylation and higher brain natriuretic peptide expression. The aortic valve regurgitation was registered in 20% of the constricted group and 60% of the dilated group, whereas mitral insufficiency was observed in 40% of the constricted group and 100% of the dilated group. Cardiac dysfunction was not associated with the increase of interstitial fibrosis and nonmyocyte proliferation. In the mouse model fibrillin-1, haploinsufficiency results in the early onset of nonfibrotic hypertrophic cardiac remodeling and dysfunction, independently from valvular abnormalities. MFS heart is vulnerable to stress-induced cardiac dilatation in the face of valvular regurgitation, and stress-activated MAPK signals represent a potential target for cardiac management in MFS.

Topics: Animals; Cardiomegaly; Fibrillin-1; Fibrillins; Fibrosis; Hemodynamics; Male; MAP Kinase Signaling System; Marfan Syndrome; Mice; Mice, Inbred C57BL; Microfilament Proteins; Mitral Valve Insufficiency; Myocardium; p38 Mitogen-Activated Protein Kinases; Phenotype; Smad2 Protein; Smad3 Protein; Transforming Growth Factor beta; Ultrasonography; Ventricular Function, Left

In patients with myocardial infarction (MI), leaflet tethering by displaced papillary muscles induces mitral regurgitation (MR), which doubles mortality. Mitral valves (MVs) are larger in such patients but fibrosis sets in counterproductively. The investigators previously reported that experimental tethering alone increases mitral valve area in association with endothelial-to-mesenchymal transition.. The aim of this study was to explore the clinically relevant situation of tethering and MI, testing the hypothesis that ischemic milieu modifies mitral valve adaptation.. Twenty-three adult sheep were examined. Under cardiopulmonary bypass, the papillary muscle tips in 6 sheep were retracted apically to replicate tethering, short of producing MR (tethered alone). Papillary muscle retraction was combined with apical MI created by coronary ligation in another 6 sheep (tethered plus MI), and left ventricular remodeling was limited by external constraint in 5 additional sheep (left ventricular constraint). Six sham-operated sheep were control subjects. Diastolic mitral valve surface area was quantified by 3-dimensional echocardiography at baseline and after 58 ± 5 days, followed by histopathology and flow cytometry of excised leaflets.. Tethered plus MI leaflets were markedly thicker than tethered-alone valves and sham control subjects. Leaflet area also increased significantly. Endothelial-to-mesenchymal transition, detected as α-smooth muscle actin-positive endothelial cells, significantly exceeded that in tethered-alone and control valves. Transforming growth factor-β, matrix metalloproteinase expression, and cellular proliferation were markedly increased. Uniquely, tethering plus MI showed endothelial activation with vascular adhesion molecule expression, neovascularization, and cells positive for CD45, considered a hematopoietic cell marker. Tethered plus MI findings were comparable with external ventricular constraint.. MI altered leaflet adaptation, including a profibrotic increase in valvular cell activation, CD45-positive cells, and matrix turnover. Understanding cellular and molecular mechanisms underlying leaflet adaptation and fibrosis could yield new therapeutic opportunities for reducing ischemic MR.

Topics: Adaptation, Physiological; Animals; Cell Proliferation; Disease Models, Animal; Echocardiography, Three-Dimensional; Epithelial-Mesenchymal Transition; Matrix Metalloproteinases; Mitral Valve; Mitral Valve Insufficiency; Myocardial Infarction; Papillary Muscles; Sheep; Transforming Growth Factor beta; Ventricular Remodeling

Cardiospondylocarpofacial (CSCF) syndrome is characterized by growth retardation, dysmorphic facial features, brachydactyly with carpal-tarsal fusion and extensive posterior cervical vertebral synostosis, cardiac septal defects with valve dysplasia, and deafness with inner ear malformations. Whole-exome sequencing identified heterozygous MAP3K7 mutations in six distinct CSCF-affected individuals from four families and ranging in age from 5 to 37 years. MAP3K7 encodes transforming growth factor β (TGF-β)-activated kinase 1 (TAK1), which is involved in the mitogen-activated protein kinase (MAPK)-p38 signaling pathway. MAPK-p38 signaling was markedly altered when expression of non-canonical TGF-β-driven target genes was impaired. These findings support the loss of transcriptional control of the TGF-β-MAPK-p38 pathway in fibroblasts obtained from affected individuals. Surprisingly, although TAK1 is located at the crossroad of inflammation, immunity, and cancer, this study reports MAP3K7 mutations in a developmental disorder affecting mainly cartilage, bone, and heart.

Topics: Abnormalities, Multiple; Adolescent; Adult; Carpal Bones; Cervical Vertebrae; Child; Child, Preschool; Female; Fibroblasts; Gene Expression Regulation; Hearing Loss, Bilateral; Hearing Loss, Conductive; Heterozygote; Humans; Interleukin-1beta; Male; MAP Kinase Kinase Kinases; MAP Kinase Signaling System; Mitral Valve Insufficiency; Mutation; Osteosclerosis; p38 Mitogen-Activated Protein Kinases; Syndrome; Tarsal Bones; Transforming Growth Factor beta; Young Adult

Little is known about the pathophysiology of myxomatous degeneration of the mitral valve, the pathological hallmark of mitral valve prolapse, associated with symptomatic mitral regurgitation, heart failure, and death. Excess transforming growth factor (TGF)-β signaling is known to cause mitral valve degeneration and regurgitation in a mouse model of Marfan syndrome. We examined if TGF-β signaling is dysregulated in clinical specimens of sporadic mitral valve prolapse compared with explanted nondiseased mitral valves and we tested the effects of angiotensin II receptor blockers on TGF-β signaling in cultured human mitral valve cells.. Operative specimens, cultured valve tissues, and cultured valvular interstitial cells were obtained from patients with mitral valve prolapse undergoing mitral valve repair or from organ donors without mitral valve disease. Increased extracellular matrix in diseased valve tissue correlated with an upregulation of TGF-β expression and signaling as evidenced by SMAD2/3 phosphorylation. Both TGF-β ligand and signaling mediators colocalized primarily to valvular interstitial cells suggesting autocrine/paracrine activation. In cultured valve tissue, exogenous TGF-β increased basal extracellular matrix production, whereas serological neutralization of TGF-β inhibited disease-driven extracellular matrix overproduction. TGF-β-induced extracellular matrix production in cultured valvular interstitial cells was dependent on SMAD2/3 and p38 signaling and was inhibited by angiotensin II receptor blockers.. TGF-β has a profibrotic role in the pathogenesis of sporadic mitral valve prolapse. Attenuation of TGF-β signaling by angiotensin II receptor blockers may represent a mechanistically based strategy to modulate the pathological progression of mitral valve prolapse in patients.

Topics: Angiotensin Receptor Antagonists; Benzimidazoles; Benzoates; Biphenyl Compounds; Cells, Cultured; Collagen; Elastic Tissue; Extracellular Matrix Proteins; Fibrosis; Gene Expression Regulation; Genetic Diseases, X-Linked; Heart Defects, Congenital; Humans; Losartan; Mitral Valve Insufficiency; Mitral Valve Prolapse; Myxoma; Polymerase Chain Reaction; Signal Transduction; Smad2 Protein; Smad3 Protein; Telmisartan; Tetrazoles; Transforming Growth Factor beta; Vimentin

Scarring and collagen deposition in the valves and destruction of myocytes may result from the combined effects of a smoldering rheumatic process and a constant trauma to the mitral valve or aortic valve by the turbulent flow in rheumatic heart disease (RHD). Transforming growth factor-beta1 (TGF-beta1) may be responsible for the increased valvular fibrosis and calcification in the pathogenesis of RHD. However, the role of TGF-beta1 genetic variant in RHD has not been studied. This case-controlled study was carried out to investigate the possible relationship between the TGF-beta1 gene C-509T and T869C polymorphisms and RHD among the Chinese population in Taiwan.. A group of 115 patients with RHD documented by using echocardiography and 100 age- and sex-matched healthy control patients were studied. TGF-beta1 gene C-509T and T869C polymorphisms were identified with polymerase chain reaction-based restriction analysis.. A significant difference was seen in the distribution of genotypes between patients with RHD and control patients for either TGF-beta1 C-509T polymorphism (P <.0001) or T869C polymorphism (P <.0001). The frequency of TGF-beta1 C-509T CC genotype was lower in the RHD group than in the control group (chi2 = 19.05, P <.0001), which suggests that this genotype may confer protective effects against RHD. A significant difference was seen in the distribution of allelic frequency between patients with RHD and control patients for TGF-beta1 T869C polymorphism (P =.04). The odds ratio (OR) for risk of RHD associated with TGF-beta1 T869C T allele was 1.49 (95% CI, 1.02-2.19). Further categorization of patients with RHD into mitral valve disease and combined valve disease subgroups revealed no statistical difference in these gene polymorphisms when compared with the 2 subgroups.. Patients with RHD have a lower frequency of TGF-beta1 C-509T CC genotype and a higher frequency of T869C T allele, which supports a role for the TGF-beta1 gene C-509T and T869C polymorphisms in determining the risk/protection of RHD in Taiwan Chinese patients.

Topics: Adult; Aged; Case-Control Studies; China; Female; Genetics, Population; Genotype; Heart Valve Diseases; Humans; Male; Middle Aged; Mitral Valve Insufficiency; Mitral Valve Stenosis; Polymorphism, Genetic; Rheumatic Heart Disease; Severity of Illness Index; Taiwan; Transforming Growth Factor beta; Transforming Growth Factor beta1; Ultrasonography