KLF15 maintains contractile phenotype of vascular smooth muscle cells and prevents thoracic aortic dissection by interacting with MRTFB.

Thoracic aortic dissection (TAD) is a highly dangerous cardiovascular disorder caused by weakening of the aortic wall, resulting in a sudden tear of the internal face. Progressive loss of the contractile apparatus in vascular smooth muscle cells (VSMCs) is a major event in TAD. Exploring the endogenous regulators essential for the contractile phenotype of VSMCs may aid the development of strategies to prevent TAD. Krüppel-like factor 15 (KLF15) overexpression was reported to inhibit TAD formation; however, the mechanisms by which KLF15 prevents TAD formation and whether KLF15 regulates the contractile phenotype of VSMCs in TAD are not well understood. Therefore, we investigated these unknown aspects of KLF15 function. We found that KLF15 expression was reduced in human TAD samples and ß-aminopropionitrile monofumarate-induced TAD mouse model. Klf15KO mice are susceptible to both ß-aminopropionitrile monofumarate- and angiotensin II-induced TAD. KLF15 deficiency results in reduced VSMC contractility and exacerbated vascular inflammation and extracellular matrix degradation. Mechanistically, KLF15 interacts with myocardin-related transcription factor B (MRTFB), a potent serum response factor coactivator that drives contractile gene expression. KLF15 silencing represses the MRTFB-induced activation of contractile genes in VSMCs. Thus, KLF15 cooperates with MRTFB to promote the expression of contractile genes in VSMCs, and its dysfunction may exacerbate TAD. These findings indicate that KLF15 may be a novel therapeutic target for the treatment of TAD.

S-Nitrosylation of Septin2 Exacerbates Aortic Aneurysm and Dissection by Coupling the TIAM1-RAC1 Axis in Macrophages.

BACKGROUND: S-Nitrosylation (SNO), a prototypic redox-based posttranslational modification, is involved in cardiovascular disease. Aortic aneurysm and dissection are high-risk cardiovascular diseases without an effective cure. The aim of this study was to determine the role of SNO of Septin2 in macrophages in aortic aneurysm and dissection. METHODS: Biotin-switch assay combined with liquid chromatography-tandem mass spectrometry was performed to identify the S-nitrosylated proteins in aortic tissue from both patients undergoing surgery for aortic dissection and Apoe-/- mice infused with angiotensin II. Angiotensin II-induced aortic aneurysm model and ß-aminopropionitrile-induced aortic aneurysm and dissection model were used to determine the role of SNO of Septin2 (SNO-Septin2) in aortic aneurysm and dissection development. RNA-sequencing analysis was performed to recapitulate possible changes in the transcriptome profile of SNO-Septin2 in macrophages in aortic aneurysm and dissection. Liquid chromatography-tandem mass spectrometry and coimmunoprecipitation were used to uncover the TIAM1-RAC1 (Ras-related C3 botulinum toxin substrate 1) axis as the downstream target of SNO-Septin2. Both R-Ketorolac and NSC23766 treatments were used to inhibit the TIAM1-RAC1 axis. RESULTS: Septin2 was identified S-nitrosylated at cysteine 111 (Cys111) in both aortic tissue from patients undergoing surgery for aortic dissection and Apoe-/- mice infused with Angiotensin II. SNO-Septin2 was demonstrated driving the development of aortic aneurysm and dissection. By RNA-sequencing, SNO-Septin2 in macrophages was demonstrated to exacerbate vascular inflammation and extracellular matrix degradation in aortic aneurysm. Next, TIAM1 (T lymphoma invasion and metastasis-inducing protein 1) was identified as a SNO-Septin2 target protein. Mechanistically, compared with unmodified Septin2, SNO-Septin2 reduced its interaction with TIAM1 and activated the TIAM1-RAC1 axis and consequent nuclear factor-κB signaling pathway, resulting in stronger inflammation and extracellular matrix degradation mediated by macrophages. Consistently, both R-Ketorolac and NSC23766 treatments protected against aortic aneurysm and dissection by inhibiting the TIAM1-RAC1 axis. CONCLUSIONS: SNO-Septin2 drives aortic aneurysm and dissection through coupling the TIAM1-RAC1 axis in macrophages and activating the nuclear factor-κB signaling pathway-dependent inflammation and extracellular matrix degradation. Pharmacological blockade of RAC1 by R-Ketorolac or NSC23766 may therefore represent a potential treatment against aortic aneurysm and dissection.

Asiatic acid alleviates vascular remodeling in BAPN-induced aortic dissection through inhibiting NF-κB p65/CX3CL1 signaling.

Inflammation assumes a pivotal role in the aortic remodeling of aortic dissection (AD). Asiatic acid (AA), a triterpene compound, is recognized for its strong anti-inflammatory properties. Yet, its effects on ß-aminopropionitrile (BAPN)-triggered AD have not been clearly established. The objective is to determine whether AA attenuates adverse aortic remodeling in BAPN-induced AD and clarify potential molecular mechanisms. In vitro studies, RAW264.7 cells pretreated with AA were challenged with lipopolysaccharide (LPS), and then the vascular smooth muscle cells (VSMCs)-macrophage coculture system was established to explore intercellular interactions. To induce AD, male C57BL/6J mice at three weeks of age were administered BAPN at a dosage of 1 g/kg/d for four weeks. To decipher the mechanism underlying the effects of AA, RNA sequencing analysis was conducted, with subsequent validation of these pathways through cellular experiments. AA exhibited significant suppression of M1 macrophage polarization. In the cell coculture system, AA facilitated the transformation of VSMCs into a contractile phenotype. In the mouse model of AD, AA strikingly prevented the BAPN-induced increases in inflammation cell infiltration and extracellular matrix degradation. Mechanistically, RNA sequencing analysis revealed a substantial upregulation of CX3CL1 expression in BAPN group but downregulation in AA-treated group. Additionally, it was observed that the upregulation of CX3CL1 negated the beneficial impact of AA on the polarization of macrophages and the phenotypic transformation of VSMCs. Crucially, our findings revealed that AA is capable of downregulating CX3CL1 expression, accomplishing this by obstructing the nuclear translocation of NF-κB p65. The findings indicate that AA holds promise as a prospective treatment for adverse aortic remodeling by suppressing the activity of NF-κB p65/CX3CL1 signaling pathway.

ß-Aminopropionitrile Induces Distinct Pathologies in the Ascending and Descending Thoracic Aortic Regions of Mice.

BACKGROUND: ß-aminopropionitrile (BAPN) is a pharmacological inhibitor of LOX (lysyl oxidase) and LOXLs (LOX-like proteins). Administration of BAPN promotes aortopathies, although there is a paucity of data on experimental conditions to generate pathology. The objective of this study was to define experimental parameters and determine whether equivalent or variable aortopathies were generated throughout the aortic tree during BAPN administration in mice. METHODS: BAPN was administered in drinking water for a period ranging from 1 to 12 weeks. The impacts of BAPN were first assessed with regard to BAPN dose, and mouse strain, age, and sex. BAPN-induced aortic pathological characterization was conducted using histology and immunostaining. To investigate the mechanistic basis of regional heterogeneity, the ascending and descending thoracic aortas were harvested after 1 week of BAPN administration before the appearance of overt pathology. RESULTS: BAPN-induced aortic rupture predominantly occurred or originated in the descending thoracic aorta in young C57BL/6J or N mice. No apparent differences were found between male and female mice. For mice surviving 12 weeks of BAPN administration, profound dilatation was consistently observed in the ascending region, while there were more heterogeneous changes in the descending thoracic region. Pathological features were distinct between the ascending and descending thoracic regions. Aortic pathology in the ascending region was characterized by luminal dilatation and elastic fiber disruption throughout the media. The descending thoracic region frequently had dissections with false lumen formation, collagen deposition, and remodeling of the wall surrounding the false lumen. Cells surrounding the false lumen were predominantly positive for α-SMA (α-smooth muscle actin). One week of BAPN administration compromised contractile properties in both regions equivalently, and RNA sequencing did not show obvious differences between the 2 aortic regions in smooth muscle cell markers, cell proliferation markers, and extracellular components. CONCLUSIONS: BAPN-induced pathologies show distinct, heterogeneous features within and between ascending and descending aortic regions in mice.

The activator protein-1 complex governs a vascular degenerative transcriptional programme in smooth muscle cells to trigger aortic dissection and rupture.

BACKGROUND AND AIMS: Stanford type A aortic dissection (AD) is a degenerative aortic remodelling disease marked by an exceedingly high mortality without effective pharmacologic therapies. Smooth muscle cells (SMCs) lining tunica media adopt a range of states, and their transformation from contractile to synthetic phenotypes fundamentally triggers AD. However, the underlying pathomechanisms governing this population shift and subsequent AD, particularly at distinct disease temporal stages, remain elusive. METHODS: Ascending aortas from nine patients undergoing ascending aorta replacement and five individuals undergoing heart transplantation were subjected to single-cell RNA sequencing. The pathogenic targets governing the phenotypic switch of SMCs were identified by trajectory inference, functional scoring, single-cell regulatory network inference and clustering, regulon, and interactome analyses and confirmed using human ascending aortas, primary SMCs, and a ß-aminopropionitrile monofumarate-induced AD model. RESULTS: The transcriptional profiles of 93 397 cells revealed a dynamic temporal-specific phenotypic transition and marked elevation of the activator protein-1 (AP-1) complex, actively enabling synthetic SMC expansion. Mechanistically, tumour necrosis factor signalling enhanced AP-1 transcriptional activity by dampening mitochondrial oxidative phosphorylation (OXPHOS). Targeting this axis with the OXPHOS enhancer coenzyme Q10 or AP-1-specific inhibitor T-5224 impedes phenotypic transition and aortic degeneration while improving survival by 42.88% (58.3%-83.3% for coenzyme Q10 treatment), 150.15% (33.3%-83.3% for 2-week T-5224), and 175.38% (33.3%-91.7% for 3-week T-5224) in the ß-aminopropionitrile monofumarate-induced AD model. CONCLUSIONS: This cross-sectional compendium of cellular atlas of human ascending aortas during AD progression provides previously unappreciated insights into a transcriptional programme permitting aortic degeneration, highlighting a translational proof of concept for an anti-remodelling intervention as an attractive strategy to manage temporal-specific AD by modulating the tumour necrosis factor-OXPHOS-AP-1 axis.

Gut microbial metabolite trimethylamine N-oxide induces aortic dissection.

Aortic dissection (AD) is the most catastrophic vascular disease with a high mortality rate. Trimethylamine N-oxide (TMAO), a gut microbial metabolite, has been implicated in the pathogenesis of cardiovascular diseases. However, the role of TMAO in AD and the underlying mechanisms remain unclear. This study aimed to explore the effects of TMAO on AD. Plasma and fecal samples from patients with AD and healthy individuals were collected to analyze TMAO levels and gut microbial species, respectively. The plasma levels of TMAO were significantly higher in 253 AD patients compared with those in 98 healthy subjects (3.47, interquartile range (IQR): 2.33 to 5.18 µM vs. 1.85, IQR: 1.40 to 3.35 µM; p < 0.001). High plasma TMAO levels were positively associated with AD severity. An increase in the relative abundance of TMA-producing genera in patients with AD was revealed using 16S rRNA sequencing. In the angiotensin II or ß-aminopropionitrile-induced rodent model of AD, mice fed a TMAO-supplemented diet were more likely to develop AD compared to mice fed a normal diet. Conversely, TMAO depletion mitigated AD formation in the BAPN model. RNA sequencing of aortic endothelial cells isolated from mice administered TMAO revealed significant upregulation of genes involved in inflammatory pathways. The in vitro experiments verified that TMAO promotes endothelial dysfunction and activates nuclear factor (NF)-κB signaling. The in vivo BAPN-induced AD model confirmed that TMAO increased aortic inflammation. Our study demonstrates that the gut microbial metabolite TMAO aggravates the development of AD at least in part by inducing endothelial dysfunction and inflammation. This study provides new insights into the etiology of AD and ideas for its management.

Early matrix softening contributes to vascular smooth muscle cell phenotype switching and aortic dissection through down-regulation of microRNA-143/145.

Thoracic aortic dissection (TAD) is characterized by extracellular matrix (ECM) dysregulation. Aberrations in the ECM stiffness can lead to changes in cellular functions. However, the mechanism by which ECM softening regulates vascular smooth muscle cell (VSMCs) phenotype switching remains unclear. To understand this mechanism, we cultured VSMCs in a soft extracellular matrix and discovered that the expression of microRNA (miR)-143/145, mediated by activation of the AKT signalling pathway, decreased significantly. Furthermore, overexpression of miR-143/145 reduced BAPN-induced aortic softening, switching the VSMC synthetic phenotype and the incidence of TAD in mice. Additionally, high-throughput sequencing of immunoprecipitated RNA indicated that the TEA domain transcription factor 1 (TEAD1) is a common target gene of miR-143/145, which was subsequently verified using a luciferase reporter assay. TEAD1 is upregulated in soft ECM hydrogels in vitro, whereas the switch to a synthetic phenotype in VSMCs decreases after TEAD1 knockdown. Finally, we verified that miR-143/145 levels are associated with disease severity and prognosis in patients with thoracic aortic dissection. ECM softening, as a result of promoting the VSMCs switch to a synthetic phenotype by downregulating miR-143/145, is an early trigger of TAD and provides a therapeutic target for this fatal disease. miR-143/145 plays a role in the early detection of aortic dissection and its severity and prognosis, which can offer information for future risk stratification of patients with dissection.

Cannabidiol protects against acute aortic dissection by inhibiting macrophage infiltration and PMAIP1-induced vascular smooth muscle cell apoptosis.

Acute aortic dissection (AAD) progresses rapidly and is associated with high mortality; therefore, there remains an urgent need for pharmacological agents that can protect against AAD. Herein, we examined the therapeutic effects of cannabidiol (CBD) in AAD by establishing a suitable mouse model. In addition, we performed human AAD single-cell RNA sequencing and mouse AAD bulk RNA sequencing to elucidate the potential underlying mechanism of CBD. Pathological assays and in vitro studies were performed to verify the results of the bioinformatic analysis and explore the pharmacological function of CBD. In a ß-aminopropionitrile (BAPN)-induced AAD mouse model, CBD reduced AAD-associated morbidity and mortality, alleviated abnormal enlargement of the ascending aorta and aortic arch, and suppressed macrophage infiltration and vascular smooth muscle cell (VSMC) apoptosis. Bioinformatic analysis revealed that the pro-apoptotic gene PMAIP1 was highly expressed in human and mouse AAD samples, and CBD could inhibit Pmaip1 expression in AAD mice. Using human aortic VSMCs (HAVSMCs) co-cultured with M1 macrophages, we revealed that CBD alleviated HAVSMCs mitochondrial-dependent apoptosis by suppressing the BAPN-induced overexpression of PMAIP1 in M1 macrophages. PMAIP1 potentially mediates HAVSMCs apoptosis by regulating Bax and Bcl2 expression. Accordingly, CBD reduced AAD-associated morbidity and mortality and mitigated the progression of AAD in a mouse model. The CBD-induced effects were potentially mediated by suppressing macrophage infiltration and PMAIP1 (primarily expressed in macrophages)-induced VSMC apoptosis. Our findings offer novel insights into M1 macrophages and HAVSMCs interaction during AAD progression, highlighting the potential of CBD as a therapeutic candidate for AAD treatment.

miR-485-3p targets SIRT1 in vascular smooth muscle cells mediating the occurrence of aortic dissection.

Studies have demonstrated a close correlation between MicroRNA and the occurrence of aortic dissection (AD). However, the molecular mechanisms underlying this relationship have not been fully elucidated and further exploration is still required. In this study, we found that miR-485-3p was significantly upregulated in human aortic dissection tissues. Meanwhile, we constructed in vitro AD models in HAVSMCs, HAECs and HAFs and found that the expression of miR-485-3p was increased only in HAVSMCs. Overexpression or knockdown of miR-485-3p in HAVSMCs could regulate the expression of inflammatory cytokines IL1ß, IL6, TNF-α, and NLRP3, as well as the expression of apoptosis-related proteins BAX/BCL2 and Cleaved caspase3/Caspase3. In the in vivo AD model, we have observed that miR-485-3p regulates vascular inflammation and apoptosis, thereby participating in the modulation of AD development in mice. Based on target gene prediction, we have validated that SIRT1 is a downstream target gene of miR-485-3p. Furthermore, by administering SIRT1 agonists and inhibitors to mice, we observed that the activation of SIRT1 alleviates vascular inflammation and apoptosis, subsequently reducing the incidence of AD. Additionally, functional reversal experiments revealed that overexpression of SIRT1 in HAVSMCs could reverse the cell inflammation and apoptosis mediated by miR-485-3p. Therefore, our research suggests that miR-485-3p can aggravate inflammation and apoptosis in vascular smooth muscle cells by suppressing the expression of SIRT1, thereby promoting the progression of aortic dissection.

Endothelial HDAC1-ZEB2-NuRD Complex Drives Aortic Aneurysm and Dissection Through Regulation of Protein S-Sulfhydration.

BACKGROUND: Aortic aneurysm and aortic dissection (AAD) are life-threatening vascular diseases, with endothelium being the primary target for AAD treatment. Protein S-sulfhydration is a newly discovered posttranslational modification whose role in AAD has not yet been defined. This study aims to investigate whether protein S-sulfhydration in the endothelium regulates AAD and its underlying mechanism. METHODS: Protein S-sulfhydration in endothelial cells (ECs) during AAD was detected and hub genes regulating homeostasis of the endothelium were identified. Clinical data of patients with AAD and healthy controls were collected, and the level of the cystathionine γ lyase (CSE)/hydrogen sulfide (H2S) system in plasma and aortic tissue were determined. Mice with EC-specific CSE deletion or overexpression were generated, and the progression of AAD was determined. Unbiased proteomics and coimmunoprecipitation combined with mass spectrometry analysis were conducted to determine the upstream regulators of the CSE/H2S system and the findings were confirmed in transgenic mice. RESULTS: Higher plasma H2S levels were associated with a lower risk of AAD, after adjustment for common risk factors. CSE was reduced in the endothelium of AAD mouse and aorta of patients with AAD. Protein S-sulfhydration was reduced in the endothelium during AAD and protein disulfide isomerase (PDI) was the main target. S-sulfhydration of PDI at Cys343 and Cys400 enhanced PDI activity and mitigated endoplasmic reticulum stress. EC-specific CSE deletion was exacerbated, and EC-specific overexpression of CSE alleviated the progression of AAD through regulating the S-sulfhydration of PDI. ZEB2 (zinc finger E-box binding homeobox 2) recruited the HDAC1-NuRD complex (histone deacetylase 1-nucleosome remodeling and deacetylase) to repress the transcription of CTH, the gene encoding CSE, and inhibited PDI S-sulfhydration. EC-specific HDAC1 deletion increased PDI S-sulfhydration and alleviated AAD. Increasing PDI S-sulfhydration with the H2S donor GYY4137 or pharmacologically inhibiting HDAC1 activity with entinostat alleviated the progression of AAD. CONCLUSIONS: Decreased plasma H2S levels are associated with an increased risk of aortic dissection. The endothelial ZEB2-HDAC1-NuRD complex transcriptionally represses CTH, impairs PDI S-sulfhydration, and drives AAD. The regulation of this pathway effectively prevents AAD progression.

Familial Associations of Prevalence and Cause-Specific Mortality for Thoracic Aortic Disease and Bicuspid Aortic Valve in a Large-Population Database.

BACKGROUND: Thoracic aortic disease and bicuspid aortic valve (BAV) likely have a heritable component, but large population-based studies are lacking. This study characterizes familial associations of thoracic aortic disease and BAV, as well as cardiovascular and aortic-specific mortality, among relatives of these individuals in a large-population database. METHODS: In this observational case-control study of the Utah Population Database, we identified probands with a diagnosis of BAV, thoracic aortic aneurysm, or thoracic aortic dissection. Age- and sex-matched controls (10:1 ratio) were identified for each proband. First-degree relatives, second-degree relatives, and first cousins of probands and controls were identified through linked genealogical information. Cox proportional hazard models were used to quantify the familial associations for each diagnosis. We used a competing-risk model to determine the risk of cardiovascular-specific and aortic-specific mortality for relatives of probands. RESULTS: The study population included 3 812 588 unique individuals. Familial hazard risk of a concordant diagnosis was elevated in the following populations compared with controls: first-degree relatives of patients with BAV (hazard ratio [HR], 6.88 [95% CI, 5.62-8.43]); first-degree relatives of patients with thoracic aortic aneurysm (HR, 5.09 [95% CI, 3.80-6.82]); and first-degree relatives of patients with thoracic aortic dissection (HR, 4.15 [95% CI, 3.25-5.31]). In addition, the risk of aortic dissection was higher in first-degree relatives of patients with BAV (HR, 3.63 [95% CI, 2.68-4.91]) and in first-degree relatives of patients with thoracic aneurysm (HR, 3.89 [95% CI, 2.93-5.18]) compared with controls. Dissection risk was highest in first-degree relatives of patients who carried a diagnosis of both BAV and aneurysm (HR, 6.13 [95% CI, 2.82-13.33]). First-degree relatives of patients with BAV, thoracic aneurysm, or aortic dissection had a higher risk of aortic-specific mortality (HR, 2.83 [95% CI, 2.44-3.29]) compared with controls. CONCLUSIONS: Our results indicate that BAV and thoracic aortic disease carry a significant familial association for concordant disease and aortic dissection. The pattern of familiality is consistent with a genetic cause of disease. Furthermore, we observed higher risk of aortic-specific mortality in relatives of individuals with these diagnoses. This study provides supportive evidence for screening in relatives of patients with BAV, thoracic aneurysm, or dissection.

Epigenetic Induction of Smooth Muscle Cell Phenotypic Alterations in Aortic Aneurysms and Dissections.

BACKGROUND: Smooth muscle cell (SMC) phenotypic switching has been increasingly detected in aortic aneurysm and dissection (AAD) tissues. However, the diverse SMC phenotypes in AAD tissues and the mechanisms driving SMC phenotypic alterations remain to be identified. METHODS: We examined the transcriptomic and epigenomic dynamics of aortic SMC phenotypic changes in mice with angiotensin II-induced AAD by using single-cell RNA sequencing and single-cell sequencing assay for transposase-accessible chromatin. SMC phenotypic alteration in aortas from patients with ascending thoracic AAD was examined by using single-cell RNA sequencing analysis. RESULTS: Single-cell RNA sequencing analysis revealed that aortic stress induced the transition of SMCs from a primary contractile phenotype to proliferative, extracellular matrix-producing, and inflammatory phenotypes. Lineage tracing showed the complete transformation of SMCs to fibroblasts and macrophages. Single-cell sequencing assay for transposase-accessible chromatin analysis indicated that these phenotypic alterations were controlled by chromatin remodeling marked by the reduced chromatin accessibility of contractile genes and the induced chromatin accessibility of genes involved in proliferation, extracellular matrix, and inflammation. IRF3 (interferon regulatory factor 3), a proinflammatory transcription factor activated by cytosolic DNA, was identified as a key driver of the transition of aortic SMCs from a contractile phenotype to an inflammatory phenotype. In cultured SMCs, cytosolic DNA signaled through its sensor STING (stimulator of interferon genes)-TBK1 (tank-binding kinase 1) to activate IRF3, which bound and recruited EZH2 (enhancer of zeste homolog 2) to contractile genes to induce repressive H3K27me3 modification and gene suppression. In contrast, double-stranded DNA-STING-IRF3 signaling induced inflammatory gene expression in SMCs. In Sting-/- mice, the aortic stress-induced transition of SMCs into an inflammatory phenotype was prevented, and SMC populations were preserved. Finally, profound SMC phenotypic alterations toward diverse directions were detected in human ascending thoracic AAD tissues. CONCLUSIONS: Our study reveals the dynamic epigenetic induction of SMC phenotypic alterations in AAD. DNA damage and cytosolic leakage drive SMCs from a contractile phenotype to an inflammatory phenotype.

Bestrophin3 Deficiency in Vascular Smooth Muscle Cells Activates MEKK2/3-MAPK Signaling to Trigger Spontaneous Aortic Dissection.

BACKGROUND: Aortic dissection (AD) is a fatal cardiovascular disorder without effective medications due to unclear pathogenic mechanisms. Bestrophin3 (Best3), the predominant isoform of bestrophin family in vessels, has emerged as critical for vascular pathological processes. However, the contribution of Best3 to vascular diseases remains elusive. METHODS: Smooth muscle cell-specific and endothelial cell-specific Best3 knockout mice (Best3SMKO and Best3ECKO, respectively) were engineered to investigate the role of Best3 in vascular pathophysiology. Functional studies, single-cell RNA sequencing, proteomics analysis, and coimmunoprecipitation coupled with mass spectrometry were performed to evaluate the function of Best3 in vessels. RESULTS: Best3 expression in aortas of human AD samples and mouse AD models was decreased. Best3SMKO but not Best3ECKO mice spontaneously developed AD with age, and the incidence reached 48% at 72 weeks of age. Reanalysis of single-cell transcriptome data revealed that reduction of fibromyocytes, a fibroblast-like smooth muscle cell cluster, was a typical feature of human ascending AD and aneurysm. Consistently, Best3 deficiency in smooth muscle cells decreased the number of fibromyocytes. Mechanistically, Best3 interacted with both MEKK2 and MEKK3, and this interaction inhibited phosphorylation of MEKK2 at serine153 and MEKK3 at serine61. Best3 deficiency induced phosphorylation-dependent inhibition of ubiquitination and protein turnover of MEKK2/3, thereby activating the downstream mitogen-activated protein kinase signaling cascade. Furthermore, restoration of Best3 or inhibition of MEKK2/3 prevented AD progression in angiotensin II-infused Best3SMKO and ApoE-/- mice. CONCLUSIONS: These findings unveil a critical role of Best3 in regulating smooth muscle cell phenotypic switch and aortic structural integrity through controlling MEKK2/3 degradation. Best3-MEKK2/3 signaling represents a novel therapeutic target for AD.

HSPB6 Deficiency Promotes the Development of Aortic Dissection and Rupture.

To better understand the pathogenesis of acute type A aortic dissection, high-sensitivity liquid chromatography-tandem mass spectrometry/mass spectrometry (LC-MS/MS)-based proteomics and phosphoproteomics approaches were used to identify differential proteins. Heat shock protein family B (small) member 6 (HSPB6) in aortic dissection was significantly reduced in human and mouse aortic dissection samples by real-time PCR, western blotting, and immunohistochemical staining techniques. Using an HSPB6-knockout mouse, we investigated the potential role of HSPB6 in ß-aminopropionitrile monofumarate-induced aortic dissection. We found increased mortality and increased probability of ascending aortic dissection after HSPB6 knockout compared with wild-type mice. Mechanistically, our data suggest that HSPB6 deletion promoted vascular smooth muscle cell apoptosis. More importantly, HSPB6 deletion attenuated cofilin activity, leading to excessive smooth muscle cell stiffness and eventually resulting in the development of aortic dissection and rupture. Our data suggest that excessive stiffness of vascular smooth muscle cells caused by HSPB6 deficiency is a new pathogenetic mechanism leading to aortic dissection.

Iron deficiency affects oxygen transport and activates HIF1 signaling pathway to regulate phenotypic transformation of VSMC in aortic dissection.

BACKGROUND: Aortic dissection (AD) is a macrovascular disease which is pathologically characterized by aortic media degeneration.This experiment aims to explore how iron deficiency (ID) affects the function of vascular smooth muscle cell (VSMC) and participates in the occurrence and development of AD by regulating gene expression. METHODS: The relationship between iron and AD was proved by Western-blot (WB) and immunostaining experiments in human and animals. Transcriptomic sequencing explored the transcription factors that were altered downstream. WB, flow cytometry and immunofluorescence were used to demonstrate whether ID affected HIF1 expression through oxygen transport. HIF1 signaling pathway and phenotypic transformation indexes were detected in cell experiments. The use of the specific HIF1 inhibitor PX478 further demonstrated that ID worked by regulating HIF1. RESULTS: The survival period of ID mice was significantly shortened and the pathological staining results were the worst. Transcriptomic sequencing indicated that HIF1 was closely related to ID and the experimental results indicated that ID might regulate HIF1 expression by affecting oxygen balance. HIF1 activation regulates the phenotypic transformation of VSMC and participates in the occurrence and development of AD in vivo and in vitro.PX478, the inhibition of HIF1, can improve ID-induced AD exacerbation.

Unveiling cellular and molecular aspects of ascending thoracic aortic aneurysms and dissections.

Ascending thoracic aortic aneurysm (ATAA) remains a significant medical concern, with its asymptomatic nature posing diagnostic and monitoring challenges, thereby increasing the risk of aortic wall dissection and rupture. Current management of aortic repair relies on an aortic diameter threshold. However, this approach underestimates the complexity of aortic wall disease due to important knowledge gaps in understanding its underlying pathologic mechanisms.Since traditional risk factors cannot explain the initiation and progression of ATAA leading to dissection, local vascular factors such as extracellular matrix (ECM) and vascular smooth muscle cells (VSMCs) might harbor targets for early diagnosis and intervention. Derived from diverse embryonic lineages, VSMCs exhibit varied responses to genetic abnormalities that regulate their contractility. The transition of VSMCs into different phenotypes is an adaptive response to stress stimuli such as hemodynamic changes resulting from cardiovascular disease, aging, lifestyle, and genetic predisposition. Upon longer exposure to stress stimuli, VSMC phenotypic switching can instigate pathologic remodeling that contributes to the pathogenesis of ATAA.This review aims to illuminate the current understanding of cellular and molecular characteristics associated with ATAA and dissection, emphasizing the need for a more nuanced comprehension of the impaired ECM-VSMC network.

Risk assessment for aortic dissection in Turner syndrome: The role of the aortic growth rate.

OBJECTIVE: The risk of aortic dissection (AoD) is increased in Turner syndrome (TS) but predicting those at risk is difficult. Based on scarce evidence, preventive aortic surgery is recommended when aortic diameter increases >5 mm/year. To investigate the aortic growth rate in TS and TS-related conditions associated with aortic growth. We also reported our experience of women who suffered aortic dissection (AoD), and who had preventive aortic replacement. METHODS: 151 adult TS were retrospectively identified. Women who had more than one transthoracic echocardiogram (TTE) after age 16 years were included in the aortic growth study. Aortic diameters at sinuses of Valsalva (SoV) and ascending aorta (AA) were analysed by two experts. RESULTS: 70/151 women had more than one TTE (interscan interval 4.7 years). Mean aortic growth was 0.13 ± 0.59 mm/year at SoV and 0.23 ± 0.82 mm/year at AA. Known risk factors for aortic dilatation and TS-related conditions were not associated with aortic growth. 4/151 women experienced AoD (age 25±8 years): two had paired scans for aortic growth, which was 0.67 mm/year at both SoV and AA in the first woman, and 11 mm/year (SoV) and 4 mm/year (AA) in the second. Only 1/4 of women with AoD survived; she used a TS cardiac-alert card to inform emergency personnel about her risk of AoD. 5/151 had a preventive aortic replacement, but one died post-operatively. CONCLUSIONS: Mean aortic growth in our TS population was increased compared to non-TS women and was not associated with currently known risk factors for AoD, suggesting that aortic growth rate itself could be a useful variable to stratify who is at risk for AoD.

Comparison of open thoracoabdominal repair for chronic aortic dissections and aneurysms.

OBJECTIVE: Aortic dissection is common in patients undergoing open surgical repair of thoracoabdominal aortic aneurysms (TAAAs). Most often, dissection is chronic and is associated with progressive aortic dilatation. Because contemporary outcomes in chronic dissection are not clearly understood, we compared patient characteristics and outcomes after open TAAA repair between patients with chronic dissection and those with non-dissection aneurysm. METHODS: We retrospectively analyzed data from 3470 open TAAA repairs performed in a single practice. Operations were for non-dissection aneurysm in 2351 (67.8%) and chronic dissection in 1119 (32.2%). Outcomes included operative mortality and adverse events, a composite variable comprising operative death and persistent (present at discharge) stroke, paraplegia, paraparesis, and renal failure necessitating dialysis. Logistic regression identified predictors of operative mortality and adverse events. Time-to-event analyses examined survival, death, repair failure, subsequent progressive repair, and survival free of failure or subsequent repair. RESULTS: Compared with patients with non-dissection aneurysm, those with chronic dissection were younger, had fewer atherosclerotic risk factors, and were more likely to have heritable thoracic aortic disease and undergo extent II repair. The operative mortality rate was 8.5% (n = 296) overall and was higher in non-dissection aneurysm patients (n = 217; 9.2%) than in chronic dissection patients (n = 79; 7.1%; P = .03). Adverse events were less frequent (P = .01) in patients with chronic dissection (n = 145; 13.0%), 22 (2.0%) of whom had persistent paraplegia. Chronic dissection was not predictive of operative mortality (P = .5) or adverse events (P = .6). Operative mortality and adverse events, respectively, were independently predicted by emergency repair (odds ratio [OR], 3.46 and 2.87), chronic kidney disease (OR, 1.74 and 1.81), extent II TAAA repair (OR, 1.44 and 1.73), increasing age (OR, 1.04/year and 1.04/year), and increasing aortic cross-clamp time (OR, 1.02/minutes and 1.02/minutes). Patients with chronic dissection had lower 10-year unadjusted mortality (42% vs 69%) but more frequent repair failure (5% vs 3%) and subsequent repair for progressive aortic disease (11% vs 5%) than patients with non-dissection aneurysm (P < .001); these differences were no longer statistically significant after adjustment. CONCLUSIONS: Outcomes of open TAAA repair vary by aortic disease type. Emergency repairs and atherosclerotic diseases most commonly occur in patients with non-dissection aneurysm and independently predict operative mortality. Repair of chronic dissection is associated with low rates of adverse events, including operative mortality and persistent paraplegia, along with reasonable late survival and good durability. However, patients with chronic dissection tend to more commonly undergo subsequent repair to treat progressive aortic disease, which emphasizes the need for robust long-term imaging surveillance protocols.

Natural history and long-term outcomes of medically managed Type B intramural hematoma.

OBJECTIVE: Type B intramural hematoma (IMH) is often managed medically, yet may progress to dissection, aneurysmal dilation, or rupture. The aim of this study was to report the natural history of medically managed Type B IMH, and factors associated with progression. METHODS: We reviewed patients with medically managed Type B IMH between January 1995 to December 2022 at a single center. Any patients with immediate surgical or endovascular intervention were excluded. Demographic profiles, comorbidities, imaging, and follow-up details were reviewed. Patients were divided into two groups: Group 1 had isolated IMH, and Group 2 had IMH along with aneurysm or dissection at the time of presentation. On follow-up, progression was defined as degeneration to aneurysm/dissection or increase in the thickness of IMH in Group 1. In Group 2, progression was an increase in the size of aneurysm or development of new dissection. RESULTS: Of 104 patients with Type B IMH during the study period, 92 were medically managed. The median age was 77 years, and 45 (48.9%) were females. Comorbidities included hypertension (83.7%), hypercholesterolemia (44.6%), and active smoking (47.8%). Mean Society for Vascular Surger comorbidity score was 6.3. Mean IMH thickness and aortic diameter at presentation were 8.9 mm and 38.3 mm, respectively. Median follow-up was 55 months. Overall survival at 1 year and 5 years was 85.8% and 61.9%, respectively. During follow-up, 19 patients (20.7%) required intervention, more common in Group 2 (Group 1, 8/66; 12.3% vs Group 2, 11/26; 42.3%; P = .001). This resulted in higher freedom from intervention in Group 1 at 1 year (93.5% vs 62.7%) and 5 years (87.5% vs 51.1%; P < .001). Indication for intervention was dissection (n = 4), aneurysm (n = 12), and progression of IMH (n = 3). In Group 1, progression was seen in 25 (37.9%), three (4.5%) remained stable, 29 (43.9%) had complete resolution of IMH, and nine patients were lost to follow-up. In Group 2, 11 patients (42.3%) had progression, seven (26.9%) remained stable, and eight were lost to follow-up. IMH thickness at presentation >7.2 mm is associated with both increased odds of progression (odds ratio, 3.3; 95% confidence interval, 1.2-11.1; P = .03) and intervention (odds ratio, 5.5; 95% confidence interval, 1.3-36.9; P = .03) during the follow-up. CONCLUSIONS: Although many patients with Type B IMH managed medically stabilize or regress, progression or need for intervention can occur in up to 40% of cases. This is associated with the presence of aneurysm, dissection, and IMH thickness. Long-term follow-up is mandatory as late interventions occur, particularly for higher risk patients.

Extended thoracic endovascular aortic repair is optimal therapy in acute complicated type B dissection.

BACKGROUND: Thoracic endovascular aortic repair (TEVAR) represents optimal therapy for complicated acute type B aortic dissection (aTBAD). Persistent knowledge gaps remain, including the optimal length of aortic coverage, impact on distal aortic remodeling, and fate of the dissected abdominal aorta. METHODS: Review of the Emory Aortic Database identified 92 patients who underwent TEVAR for complicated aTBAD from 2012 to 2018. Standard TEVAR covered aortic zones 3 and 4 (from the left subclavian to the mid-descending thoracic aorta). Extended TEVAR fully covered aortic zones 3 though 5 (from the left subclavian to the celiac artery). Long-term imaging, clinical follow-up, and overall and aortic-specific mortality were reviewed. RESULTS: Extended TEVAR (n = 52) required a greater length of coverage vs standard TEVAR (n = 40) (240 ± 32 mm vs 183 ± 23 mm; P < .01). In-hospital mortality occurred in 5.4% of patients (7.7% vs 2.5%; P = .27) owing to mesenteric malperfusion (n = 3) or rupture (n = 2). The overall incidences of postoperative stroke, transient paraparesis, paraplegia, and dialysis were 5.4% (3.9% vs 7.5%; P = .38), 3.2% (5.8% vs 0%; P = .18), 0%, and 0% respectively, equivalent between groups. Follow-up was 96.6% complete to a mean of 6.1 years (interquartile range, 3.5-8.6 years). There were significantly higher rates of complete thrombosis or obliteration of the entire thoracic false lumen after Extended TEVAR (82.2% vs 51.5%; P = .04). Distal aortic reinterventions were less frequent after extended TEVAR (5.8% vs 20%; P = .04). Late aorta-specific survival was 98.1% after extended TEVAR vs 92.3% for standard TEVAR (P = .32). CONCLUSIONS: Extended TEVAR for complicated aTBAD is safe, results in a high rate of total thoracic false lumen thrombosis/obliteration, and reduces distal reinterventions. Longer-term follow-up will be needed to demonstrate a survival benefit compared to limited aortic coverage.