Project description:Valve remodeling is a complex process involving extracellular matrix organization, development of trilaminar structures, and physical elongation of valve leaflets. However, the cellular and molecular mechanisms regulating valve remodeling and their roles in congenital valve disorders remain poorly understood. Semilunar valves and atrioventricular valves from healthy and age-matched human fetal hearts with pulmonary stenosis (PS) were collected. Single-Cell RNA-sequencing (scRNA-seq) was performed to determine the transcriptomic landscape of multiple valvular cell subtypes in valve remodeling and disease. Spatial localization of newly-identified cell subtypes was determined via immunofluorescence and RNA in situ hybridization. The molecular mechanisms mediating valve development was investigated utilizing primary human fetal valve interstitial cells (VICs) and endothelial cells (VECs). scRNA-seq analysis of healthy human fetal valves identified a novel APOE+ elastin-producing VIC subtype (Elastin-VIC) spatially located underneath VECs sensing the unidirectional flow. Knockdown of APOE in fetal VICs resulted in significant elastogenesis defects. In pulmonary valve with PS, we observed decreased expression of APOE and other genes regulating elastogenesis such as EMILIN1 and LOXL1, as well as elastin fragmentation. These findings suggested the crucial role of APOE in regulating elastogenesis during valve remodeling. Furthermore, cell-cell interaction analysis revealed that JAG1 from unidirectional VECs activates NOTCH signaling in Elastin-VICs through NOTCH3. In vitro Jag1 treatment in VICs increased the expression of elastogenesis-related genes and enhanced contractile functions with related gene expression. This was accompanied by activation of NOTCH signaling and elastogenesis observed in VICs co-cultured with VECs in the presence of unidirectional flow. Notably, we found that the JAG1-NOTCH3 signaling pair was drastically reduced in the PS valves. Lastly, we demonstrated that APOE is indispensable for JAG1-induced NOTCH activation in VICs, reinforcing the presence of a synergistic intrinsic and external regulatory network involving APOE and NOTCH signaling that is responsible for regulating elastogenesis during human valve remodeling. scRNA-seq analysis of human fetal valves identified a novel Elastin-VIC subpopulation, and revealed mechanism of intrinsic APOE and external NOTCH signaling from VECs sensing unidirectional flow in regulating elastogenesis during valve remodeling. These mechanisms may contribute to the pathogenesis of elastic malformation in congenital valve disease.
Project description:Our studies identify a mechanism of signaling crosstalk during valve morphogenesis that sheds light on the origin of congenital heart defects associated with reduced Notch function.
Project description:Aortic valve calcification is the most common form of valvular heart disease, but the mechanisms of calcific aortic valve disease (CAVD) are unknown. NOTCH1 mutations are associated with aortic valve malformations and adult-onset calcification in families with inherited disease. The Notch signaling pathway is critical for multiple cell differentiation processes, but its role in the development of CAVD is not well understood. The aim of this study was to investigate the molecular changes that occur with inhibition of Notch signaling in the aortic valve. Notch signaling pathway members are expressed in adult aortic valve cusps, and examination of diseased human aortic valves revealed decreased expression of NOTCH1 in areas of calcium deposition. To identify downstream mediators of Notch1, we examined gene expression changes that occur with chemical inhibition of Notch signaling in rat aortic valve interstitial cells (AVICs). We found significant downregulation of Sox9 along with several cartilage-specific genes that were direct targets of the transcription factor, Sox9. Loss of expression Sox9 has been published to be associated with aortic valve calcification. Utilizing an in vitro porcine aortic valve calcification model system, inhibition of Notch activity resulted in accelerated calcification while stimulation of Notch signaling attenuated the calcific process. Finally, the addition of Sox9 was able to prevent the calcification of porcine AVICs that occurs with Notch inhibition. In conclusion, loss of Notch signaling contributes to aortic valve calcification via a Sox9-dependent mechanism. 3 samples of aortic valve interstitial cells treated with DAPT were compared with 3 samples of aortic valve interstitial cells treated with DMSO
Project description:Calcific aortic valve disease (CAVD) is an increasingly prevalent condition and endothelial dysfunction is implicated in its etiology. We previously identified nitric oxide (NO) as a calcification inhibitor by its activation of NOTCH1, which is genetically linked to human CAVD. Here, we show that NO rescues calcification by a S-nitrosylation-mediated mechanism in porcine aortic valve interstitial cells (pAVICs) and single cell RNA-seq demonstrated regulation of NOTCH pathway by NO. A unbiased proteomic approach to identify S-nitrosylated proteins in valve cells found enrichment of the ubiquitin proteasome pathway and implicated S-nitrosylation of USP9X in NOTCH regulation during calcification. Furthermore, S-nitrosylated USP9X was shown to deubiquitinate and stabilize MIB1 for NOTCH1 activation. Consistent with this, genetic deletion of Usp9x in mice demonstrated aortic valve disease and human calcified aortic valves displayed reduced S-nitrosylation of USP9X. These results demonstrate a novel mechanism by which S-nitrosylation dependent regulation of ubiquitin-associated pathway prevents CAVD.
Project description:Aortic valve calcification is the most common form of valvular heart disease, but the mechanisms of calcific aortic valve disease (CAVD) are unknown. NOTCH1 mutations are associated with aortic valve malformations and adult-onset calcification in families with inherited disease. The Notch signaling pathway is critical for multiple cell differentiation processes, but its role in the development of CAVD is not well understood. The aim of this study was to investigate the molecular changes that occur with inhibition of Notch signaling in the aortic valve. Notch signaling pathway members are expressed in adult aortic valve cusps, and examination of diseased human aortic valves revealed decreased expression of NOTCH1 in areas of calcium deposition. To identify downstream mediators of Notch1, we examined gene expression changes that occur with chemical inhibition of Notch signaling in rat aortic valve interstitial cells (AVICs). We found significant downregulation of Sox9 along with several cartilage-specific genes that were direct targets of the transcription factor, Sox9. Loss of expression Sox9 has been published to be associated with aortic valve calcification. Utilizing an in vitro porcine aortic valve calcification model system, inhibition of Notch activity resulted in accelerated calcification while stimulation of Notch signaling attenuated the calcific process. Finally, the addition of Sox9 was able to prevent the calcification of porcine AVICs that occurs with Notch inhibition. In conclusion, loss of Notch signaling contributes to aortic valve calcification via a Sox9-dependent mechanism.
Project description:E12.5 AV cushion and E17.5 AV valve from wild-type FVB/N mice and in vitro cultured MC3T3 cells In the study we demonstrated shared gene expression in embryonic heart valve development and Osteoblast progenitor cells. The atrioventricular (AV) valves of the heart develop from undifferentiated mesenchymal endocardial cushions, that later remodel into stratified valves with diversified extracellular matrix (ECM). Because the mature valves express genes associated with osteogenesis and exhibit disease-associated calcification, we hypothesized the existence of shared regulatory pathways active in the remodeling AV valves and in bone progenitor cells. In order to define gene regulatory programs of valvulogenesis relative to osteoblast progenitors, we undertook Affymetrix gene expression profiling analysis of murine embryonic day (E)12.5 AV cushions compared to E17.5 remodeled AV valves (mitral and tri-cuspid) and to pre-osteoblast MC3T3-E1 (subclone4) cells. Overall MC3T3 cells were significantly more similar to E17.5 valves than to E12.5 cushions, supporting the hypothesis that valve remodeling involves the expression of many genes also expressed in osteoblasts. Several transcription factors characteristic of mesenchymal and osteoblast precursor cells, including Twist1 are predominant in E12.5 cushion. Valve remodeling also includes differential regulation of matrix metalloproteinases and their inhibitors as well as characteristic collagen isoform switching. Among the most highly enriched genes during valvulogenesis were members of the small leucine-rich proteoglycan (SLRP) family including Asporin, a known negative regulator of osteoblast differentiation and mineralization. Together, these data support shared gene expression profiles of the remodeling valves and osteoblast bone precursor cells in normal valve development and homeostasis with potential functions in calcific valve disease. Keywords: Embryonic valve development time point
Project description:The complex genetics underlying human cardiac disease is evidenced by its heterogenous manifestation, multigenic basis and sporadic occurrence. These features have hampered disease modelling and mechanistic understanding. Here, we show that two structural cardiac diseases, left ventricular non-compaction (LVNC) and bicuspid aortic valve (BAV), can be caused by a combined set of inherited heterozygous mutations. We used CRISPR-Cas9 gene editing to generate mice harboring two mutations in the NOTCH ligand regulator MINDBOMB1 identified in LVNC families. One Mib1 mutation causes LVNC only in heteroallelic combination with a conditional Mib1 allele, while the other leads to BAV in a NOTCH-sensitized genetic background. These data suggest that the LVNC phenotype may be influenced by genetic modifiers present in these families, while valve defects are very sensitive to NOTCH haploinsufficiency. Whole-exome sequencing revealed single-nucleotide variants in the ASXL3, APCDD1 and TMX3, CEP192 and BCL7A genes, co-segregating with the MIB1 mutations and LVNC. We generated mice harboring the orthologous variants in the corresponding Mib1 backgrounds. Triple heterozygous Mib1 Apcdd1 Asxl3 mutants show LVNC, while quadruple heterozygous Mib1 Cep192 Tmx3;Bcl7a mice show BAV and other valve-associated defects. Biochemical assays suggest interactions between CEP192, BCL7A and NOTCH. Gene profiling of murine hearts and human induced pluripotent stem cell-derived cardiomyocytes reveals defective metabolic maturation. These findings provide evidence for a common genetic substrate for LVNC and BAV involving MIB1 and genetic modifiers
Project description:The role of TIMP3 in the context of cardiovascular remodeling is relatively unexplored when considering classical risk factors such as hypercholesterolemia, diabetes and hypertension. To learn more the role of TIMP3 in the progression of cardiovascular disease we combined genetics, metabolomics and in vivo phenotypical analysis using the hypercholesterolemic ApoE null mice to generate ApoE-/-Timp3-/- mice, the latter showing increased atherosclerosis, increased mortality and arrhythmias compared to ApoE-/- mice. We have previously described Timp3-/-mice in ( Fiorentino, L., et al., Regulation of TIMP3 in diabetic nephropathy: a role for microRNAs. Acta Diabetol, 2013) . To generate ApoE-/-Timp3-/- knockout animals we crossbred the 2 strains. Offsprings were then backcrossed into ApoE animals for 6 generations to generate a pure lineage. Collectively, metabolite profiles, gene and protein expression consistently suggested a role for TIMP3 to underlie a decreased activation of PPARα/AMPK to dampen fatty acids β-oxidation eventually leading to atherosclerotic plaque composition vulnerability and perturbation of heart metabolism. mRNA profiling in ApoE-/-Timp3-/- mice revealed a TIMP3 effect to regulate Apelin, which we found decreased in the circulation due to its specific downregulation at the myocardial level but not in other well known sites of expression such as the adipose tissue. mRNA sequencing of the heart of ApoE-/-Timp3-/- mice vs ApoE-/- littermates controls.