Project description:Mitral valve prolapse (MVP) is often benign but can progress to mitral regurgitation, requiring invasive treatment. In mgR mice with hypomorphic Fbn1 mutations—mimicking Marfan syndrome—myxomatous mitral degeneration and regurgitation develop by 12 weeks. TGF-β and mTOR signaling activation, along with macrophage infiltration, appear by 4 weeks, before histological changes. Short-term rapamycin treatment blocks early TGF-β activation and inflammation, while long-term mTOR or TGF-β inhibition rescues valve degeneration. Transcriptomics revealed integrins as upstream regulators of mTOR. Blocking integrin signaling or altering its pathway prevented mTOR activation. These findings are conserved in human MVP, suggesting that mTOR activation via abnormal integrin-matrix signaling drives disease and that mTOR inhibition may be a potential therapy.
Project description:In this study, we carried out a large-scale proteome profiling of human mitral valve tissues resected from patients with mitral valve prolapse.
Project description:Evaluation of global expression patterns provides a molecular portrait of mitral valve disease, yields insight into the pathophysiologic aspects of DMVD, and identifies intriguing genes and pathways for further study. (Am J Vet Res 2006;67:1307–1318) Keywords: control vs diseased 4 controls( beagle crosses) and 4 affected (1 Daschund, 1 Lhasa apso, 2 miniature poodles)
Project description:Evaluation of global expression patterns provides a molecular portrait of mitral valve disease, yields insight into the pathophysiologic aspects of DMVD, and identifies intriguing genes and pathways for further study. (Am J Vet Res 2006;67:1307–1318) Keywords: control vs diseased
Project description:Background: Mitral valve prolapse (MVP) is a common valvular heart disease associated related to substantial morbidity and potential mortality. The molecular mechanisms underlying disease development remain incompletely understood. We previously identified a large family in which a missense variant in LTBP2 (Val1506Met) co-segregated with MVP, suggesting a role for LTBP2 in maintaining mitral valve integrity. Objective: To investigate the role of LTBP2 in mitral valve extracellular matrix (ECM) homeostasis and its contribution to MVP pathogenesis. Methods: LTBP2 knockout (KO) mice and primary fibroblast cultures were used to assess the effects of LTBP2 deficiency on ECM organization. Immunofluorescence staining was performed on mitral valve tissue and cultured fibroblasts to evaluate ECM protein expression and localization. Scanning electron microscopy (SEM) was used to examine microfibrillar ECM architecture, while quantitative RT-PCR and RNA sequencing were employed to assess ECM-related gene expression and pathway alterations. Results: LTBP2 deficiency resulted in significant alterations in ECM organization. Immunofluorescence analysis demonstrated increased elastin expression in KO mitral valves and fibroblasts, whereas fibrillin-1, collagen III, and fibulin-5 levels were mostly unchanged. SEM revealed significant disorganization of the microfibrillar ECM architecture in LTBP2-deficient mitral valves. Consistent with these findings, qRT-PCR confirmed significantly increased elastin expression in KO fibroblasts. RNA-seq pathway analysis identified significant enrichment of pathways related to extracellular matrix organization, elastic fiber formation, and TGF-β signaling. Conclusions: These findings demonstrate that LTBP2 is a critical regulator of mitral valve ECM homeostasis. Loss of LTBP2 leads to elastin accumulation, disruption of ECM architecture, and dysregulation of ECM-related signaling pathways, providing mechanistic insight into how LTBP2 dysfunction may contribute to myxomatous degeneration and MVP pathogenesis
Project description:The mitral valve is a highly complex structure which regulates blood flow from the left atrium to the left ventricle (LV) avoiding a significant forward gradient during diastole or regurgitation during systole. The integrity of the mitral valve is also essential for the maintenance of normal LV size, geometry, and function. Significant advances in the comprehension of the biological, functional, and mechanical behavior of the mitral valve have recently been made. However, current knowledge of protein components in the normal human mitral valve is still limited and complicated by the low cellularity of this tissue and the presence of high abundant proteins from the extracellular matrix. We employed here an integrated proteomic approach to analyse the protein composition of the normal human mitral valve and reported confident identification of 422 proteins, some of which have not been previously described in this tissue. In particular, we described the ability of pre-MS separation technique based on liquid-phase IEF and SDS-PAGE to identify the largest number of proteins. These initial results provide a valuable basis for future studies aimed at analysing in depth the mitral valve protein composition and at investigating potential pathogenetic molecular mechanisms.
Project description:We here report the results of a mitral valve transcriptome study designed to identify genes and molecular pathways involved in development of congestive heart failure (CHF) following myxomatous mitral valve disease (MMVD) in dogs. The study is focused on a cohort of elderly age-matched dogs (n=34, age ~10 years) from a single breed – Cavalier King Charles Spaniels (CKCS) – with a high incidence of MMVD. The cohort comprises 19 dogs (10♀, 9♂) without MMVD-associated CHF, and 15 dogs (6♀, 9♂) with CHF caused by MMVD. I.e. we compare gene expression in breed and age matched groups of dogs, which only differ with respect to CHF status. We identify 56 genes, which are differentially expressed between the two groups. In this list of genes, we confirm an enrichment of genes related to the TNFβ signaling pathway, extracellular matrix organization, vascular development, and endothelium damage, which also have been identified in previous studies. However, the genes with the greatest difference in expression between the two groups are CNTN3 and MYH1. Both genes encode proteins, which are predicted to have an effect on the contractile activity of myocardial cells, which in turn may have an effect on valvular performance and hemodynamics across the mitral valve. This may result in shear forces with impact on MMVD progression.
Project description:Congenital heart malformations include mitral valve defects, which remain largely unexplained. During embryogenesis, a restricted population of endocardial cells within the atrioventricular canal undergoes an endothelial-to-mesenchymal transition to give rise to mitral valvular cells. However, the identity and fate decisions of these progenitors as well as the behavior and distribution of their derivatives in valve leaflets remain unknown. We used single-cell RNA sequencing (scRNA-seq) of genetically labeled endocardial cells and microdissected mouse embryonic and postnatal mitral valves to characterize the developmental road. We defined the metabolic processes underlying the specification of the progenitors and their contributions to subtypes of valvular cells. Using retrospective multicolor clonal analysis, we describe specific modes of growth and behavior of endocardial cell-derived clones, which build up, in a proper manner, functional valve leaflets. Our data identify how both genetic and metabolic mechanisms specifically drive the fate of a subset of endocardial cells toward their distinct clonal contribution to the formation of the valve.
Project description:Rational: We previously reported evidence of endothelial to mesenchymal transition (EndMT) and fibrosis in mitral valve (MV) leaflets at two to six months post-myocardial infarction (MI) in sheep. The onset of these changes and the mechanism of their instigation are not known. Early modulation of EndMT and fibrosis in MV leaflets may limit the development of ischemic mitral regurgitation (IMR) and heart failure. H Objective: To test the hypothesis that circulating molecules present in plasma within days after MI incite EndMT and fibrotic processes in MV leaflets. Method and Results: Ovine MVs harvested 8-10 days after inferior MI (IMI) showed an increase in MV thickness by histology and onset of EndMT, shown by increased CD31/α-smooth muscle actin (α-SMA)+ cells in post-MI MV leaflets (10.5±6.9%) versus sham (2.6±4%). In vitro, post-MI plasma induced EndMT and pro-fibrotic markers and enhanced migration of primary mitral valve endothelial cells (VECs). In contrast, sham plasma did not, despite the presence of TGFβ2 at levels known to induce EndMT in VECs (2 ng/ml). Analysis of sham versus post-MI plasma using a cytokine array revealed a significant drop in the Wnt signaling antagonist secreted frizzled-related protein 3 (sFRP3) in post-MI plasma compared to sham plasma, which was confirmed by ELISA. Addition of recombinant sFRP3 to post-MI plasma reversed its EndMT-inducing effect on mitral VECs, measured by restored VE-cadherin, reduced α-SMA, and reduced TGFβ1-3 expression. Extracellular signal related kinase 1/2 and SMAD2/3 phosphorylation were increased in mitral VEC by post-MI plasma, and both were blocked by supplementing the post-MI plasma with sFRP3. RNA-seq analysis of mitral VECs exposed to post-MI versus sham plasma for 24 hours showed upregulated forkhead box M1 (FOXM1), a transcription factor previously shown to drive fibrosis. FOXM1 was co-localized with CD31 in MV leaflets obtained from sheep at 8-10 days post-MI, which suggests FOXM1 may be linked to EndMT initiation. Blocking FOXM1 with Siomycin A (Sio A) reduced EndMT and pro-fibrotic transcripts in post-MI plasma treated mitral VECs. Finally, post-MI plasma-induced and TGFβ-induced FOXM1 was downregulated by sFRP3. Conclusions: Reduced sFRP3 in post-MI plasma appears to facilitate the onset of TGFβ-driven EndMT and fibrosis in mitral VECs by increasing the transcription factor FOXM1. Restoring sFRP3 levels and/or inhibiting FOXM1 may provide new strategies to minimize maladaptive changes that occur in the MV due to MI.