Project description:Congenital aortic valve disease (AVD) is one of the most common type of congenital heart defects whose molecular and genetic basis is poorly understood. Pathogenic variants in NOTCH1 and GATA5 have been associated with AVD including aortic valve stenosis (AVS) and bicuspid aortic valve (BAV). Whereas previous genetic mouse models of AVD with Notch1 haploinsufficiency or Gata5 deletion alone display limitations with regards to significant perinatal lethality or a partially penetrance, and here, we generate a new murine model by intercrossing Notch1 and Gata5 heterozygote mice. We demonstrate that Notch1;Gata5 compound mutant mice display highly penetrant and clinically relevant congenital AVS without early lethality. Echocardiographic examination shows progressive AVS and aortic dilatation in Notch1+/-;Gata5-/- compound mutant mice at 6 and 16 weeks of age. Histologic analysis of 16 week old Notch1;Gata5 compound mutant mouse hearts identifies myxomatous aortic valves with thickened and dysmorphic leaflets. Morphologic analysis reveals the presence of BAV in a subset of Notch1;Gata5 compound mice. Furthermore, histologic analysis demonstrates AVS and aortic valve leaflet thickening with proteoglycan accumulation at embryonic day 18.5 and postnatal day 10, consistent with congenital disease. RNA-sequencing analysis of postnatal day 10 aortic valves demonstrates dysregulation of extracellular matrix (ECM) genes in Notch1+/-;Gata5-/- compound mutant mice. In conclusion, we demonstrate a novel genetic interaction between Notch1 and Gata5, which is critical for the proper aortic valve development, and show that Notch1+/-;Gata5-/- compound mutant mice represent a novel mouse model of congenital and progressive AVS.
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: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:We are interested in the role of NOTCH1 and Shear Stress in Aortic Valve Endothelium. Primary human aortic valve endothelium was subjected to 4 conditions in vitro. 1) Control siRNA, No shear stress. 2) NOTCH1 siRNA, No shear stress. 3) Control siRNA, 15 dynes/cm2 shear stress. 4) NOTCH1 siRNA, 15 dynes/cm2 shear stress. Triplicates of each condition were pooled for library perp and sequencing
Project description:Bicuspid aortic valve (BAV) is the most common congenital cardiovascular disease in general population and is frequently associated with the development of thoracic aortic aneurysm (TAA). There is no effective strategy to intervene with TAA progression due to an incomplete understanding of the pathogenesis. In this study, protein analyses of human aortic tissues showed the insufficient expression of NOTCH1 and impaired mitochondrial dynamics in BAV-TAA. To verify it, we constructed aorta-on-a-chip to replicate the rhythmic tensile on human aorta, on which human aortic smooth muscle cells (HAoSMCs) endured a microenvironment of biomimetic strain unattainable in animal models. HAoSMCs with NOTCH1-knockdown exhibited reduced contractile phenotype and were accompanied by attenuated mitochondrial fusion. Furthermore, we identified that mitochondrial fusion activators (leflunomide and teriflunomide) or mitochondrial fission inhibitor (Mdivi-1) rescued the mitochondrial dysfunction in HAoSMCs from BAV-TAA patients. These findings suggest that impaired mitochondrial dynamics could be a potential therapeutic target for BAV-TAA.
Project description:Bicuspid aortic valve (BAV) is a common congenital cardiac anomaly, with an estimated incidence of 1-2%. It is responsible for the greatest burden of aortic valve disease in patients younger than 70 years in North America. We performed microRNA profiling in end-stage valve leaflets with BAV and TAV. Patients undergoing elective aortic valve replacement for aortic stenosis at St. Michael’s Hospital, University of Toronto, between June 2010 and June 2011 were enrolled. Aortic valve leaflets were obtained intraoperatively from patients with congenital bicuspid (BAV; N=10) and tricuspid aortic valves (TAV; N=10) at the time of valve replacement. Leaflets were flash frozen in liquid nitrogen. MiRNA was isolated using the miRNeasy kit (Qiagen, Hilden, Germany) according to the manufacturer`s instructions. For miRNA microarray analysis, total RNA was directly labeled with biotin and hybridized to the GenoExplorer microRNA human array containing 1583 human miRNA probes (Genosensor, Tempe, AZ) and the fluorescent signals were then scanned using a GenePix 4000b Biochip. The average of 3 mean fluorescence signal intensities for each miRNA probe was normalized to that for tRNAmet. Precursor miRNAs detected at 2-fold greater than background were considered to be expressed. Data were analyzed with GenePix 5.0 software, provided by GenoSensor Corp.
Project description:Bicuspid aortic valve (BAV) is a common congenital cardiac anomaly, with an estimated incidence of 1-2%. It is responsible for the greatest burden of aortic valve disease in patients younger than 70 years in North America. We performed microRNA profiling in end-stage valve leaflets with BAV and TAV.
Project description:Ascending aortic aneurysms (AscAA) are a life-threatening disease whose molecular basis is poorly understood. Mutations in NOTCH1 have been linked to bicuspid aortic valve (BAV), which is associated with AscAA. Here, we describe a novel role for Notch1 in AscAA. We found that Notch1 haploinsufficiency exacerbated the aneurysmal aortic root dilation seen in the Marfan syndrome mouse model and that heterozygous deletion of Notch1 in the second heart field (SHF) lineage recapitulated this exacerbated phenotype. Lineage tracing analysis showed that loss of Notch1 in the SHF reduces the number of SHF-derived smooth muscle cells in the aortic root, and RNA-seq analysis demonstrated distinct in vivo expression patterns between lineage-specific regions of the ascending aorta. Finally, Notch1+/- mice in a predominantly 129S6 background develop aortic root dilation, indicating that loss of Notch1 independently predisposes to AscAA. These findings are the first to demonstrate a SHF lineage-specific role for Notch1 in AscAA and suggest that genes linked to the development of BAV may also contribute to the associated aortopathy.