Histone deacetylase 9-mediated phenotypic transformation of vascular smooth muscle cells is a potential target for treating aortic aneurysm/dissection

Aortic aneurysm/dissection (AAD) is a serious cardiovascular condition characterized by rapid onset and high mortality rates. Currently, no effective drug treatment options are known for AAD. AAD pathogenesis is associated with the phenotypic transformation and abnormal proliferation of vascular smooth muscle cells (VSMCs). However, endogenous factors that contribute to AAD progression remain unclear. We aimed to investigate the role of histone deacetylase 9 (HDAC9) in AAD pathogenesis. HDAC9 expression was considerably increased in human thoracic aortic dissection specimens. Using RNA-sequencing (RNA-seq) and chromatin immunoprecipitation, we demonstrated that HDAC9 transcriptionally inhibited the expression of superoxide dismutase 2 and insulin-like growth factor-binding protein-3, which are critically involved in various signaling pathways. Furthermore, HDAC9 triggered the transformation of VSMCs from a systolic to synthetic phenotype, increasing their proliferation and migration abilities and suppressing their apoptosis. Consistent with these results, in vivo experiments revealed that TMP195, a pharmacological inhibitor of HDAC9, suppressed the formation of the β-aminopropionitrile-induced AAD phenotype in mice. Our findings indicate that HDAC9 may be a novel endogenous risk factor that promotes the onset of AAD by mediating the phenotypic transformation of VSMCs. Therefore, HDAC9 may serve as a potential therapeutic target for drug-based AAD treatment. Furthermore, TMP195 holds potential as a therapeutic agent for AAD treatment.

Immune Response Associated Gene Signatures in Aortic Dissection Compared to Aortic Aneurysm

BACKGROUND

Thoracic aortic dissections (TAD) are life-threatening events mostly requiring immediate surgical treatment. Although dissections mainly occur independently of thoracic aortic aneurysms (TAA), both share a high comorbidity. There are several indications for an involvement of the immune system in the development of TAD, just as in TAA. Nevertheless, specific disease-relevant genes, biomolecular processes, and immune-specific phenotypes remain unknown.

METHODS

RNA from isolated aortic smooth muscle cells from TAD (n = 4), TAA (n = 3), and control patients were analyzed using microarray-based technologies. Additionally, three publicly available bulk RNA-seq studies of TAD (n = 23) and controls (n = 17) and one single-cell RNA-seq study of TAA (n = 8) and controls (n = 3) were analyzed. Differentially expressed genes were identified and used to identify affected pathways in TAD. Five selected genes were validated by quantitative real-time polymerase chain reaction (PCR).

RESULTS

We identified 37 genes that were significantly dysregulated in at least three TAD studies-24 of them were not shown to be associated with TAD, yet. Gene ontology analysis showed that immune response was significantly affected. Five of the genes (CCL2, RNASE2, HAVCR2, CXCL8, and IL6R) were revealed as core genes that affect immune response in TAD. We compared the gene expression of those genes to TAA and found that CXCL8, IL6R, and potentially also CCL2 were upregulated in TAD.

CONCLUSIONS

The identified immune-related genes showed TAD-specificity, independent of possible pre-existing comorbidities like TAA. So, these genes represent potential biomarkers and therapeutic targets linked to the immune response in acute TAD. Additionally, we identified a set of differentially expressed genes that represents a resource for further studies.

Selenoprotein deficiency disorder predisposes to aortic aneurysm formation

Aortic aneurysms, which may dissect or rupture acutely and be lethal, can be a part of multisystem disorders that have a heritable basis. We report four patients with deficiency of selenocysteine-containing proteins due to selenocysteine Insertion Sequence Binding Protein 2 (SECISBP2) mutations who show early-onset, progressive, aneurysmal dilatation of the ascending aorta due to cystic medial necrosis. Zebrafish and male mice with global or vascular smooth muscle cell (VSMC)-targeted disruption of Secisbp2 respectively show similar aortopathy. Aortas from patients and animal models exhibit raised cellular reactive oxygen species, oxidative DNA damage and VSMC apoptosis. Antioxidant exposure or chelation of iron prevents oxidative damage in patient's cells and aortopathy in the zebrafish model. Our observations suggest a key role for oxidative stress and cell death, including via ferroptosis, in mediating aortic degeneration.

Insights into elastic fiber fragmentation: Mechanisms and treatment of aortic aneurysm in Marfan syndrome

Marfan syndrome (MFS) is an autosomal dominant connective tissue disorder caused by mutations in fibrillin 1 (FBN1) gene. These mutations result in defects in the skeletal, ocular, and cardiovascular systems. Aortic aneurysm is the leading cause of premature mortality in untreated MFS patients. Elastic fiber fragmentation in the aortic vessel wall is a hallmark of MFS-associated aortic aneurysms. FBN1 mutations result in FBN1 fragments that also contribute to elastic fiber fragmentation. Although recent research has advanced our understanding of MFS, the contribution of elastic fiber fragmentation to the pathogenesis of aneurysm formation remains poorly understood. This review provides a comprehensive overview of the molecular mechanisms of elastic fiber fragmentation and its role in the pathogenesis of aortic aneurysm progression. Increased comprehension of elastic fragmentation has significant clinical implications for developing targeted interventions to block aneurysm progression, which would benefit not only individuals with Marfan syndrome but also other patients with aneurysms. Moreover, this review highlights an overlooked connection between inhibiting aneurysm and the restoration of elastic fibers in the vessel wall with various aneurysm inhibitors, including drugs and chemicals. Investigating the underlying molecular mechanisms could uncover innovative therapeutic strategies to inhibit elastin fragmentation and prevent the progression of aneurysms.

High-Fat Diet Has a Protective Sex-Dependent Effect on Aortic Aneurysm Severity in a Marfan Syndrome Mouse Model

BACKGROUND

Marfan syndrome (MFS) is a genetic disorder caused by mutations in fibrillin-1 and is characterized by thoracic aortic aneurysms and other complications. Previous studies revealed sexual dimorphisms in formation of aortic aneurysm in patients with MFS. The current study aimed to investigate the combined role of a high-fat diet (HFD) and biological sex in aortic disease using the mgR/mgR MFS mouse model.

METHODS

Male and female mgR/mgR mice, as well as wild-type (WT) littermate mice, were fed a control diet (CD [10% fat]) or HFD (60% fat) from 4 to 12 weeks of age. Key aortic disease parameters analyzed included the diameter of the aortic wall; elastic fibre fragmentation; proteoglycan content; mRNA levels of Mmp12, Col1a1, Col3a1, and Fbn1; and fibrillin-1 deposition in the aortic wall.

RESULTS

HFD-fed female mgR/mgR mice had significantly reduced aortic diameters (35%), elastic fibre fragmentation (56%), pathologically enhanced proteoglycans (45%), and expression of Mmp12 (64%), Col1a1 (41%), and Col3a1 (43%) compared with male mgR/mgR mice on HFD. Fibrillin-1 deposition and Fbn1 mRNA levels were unaffected. The data reveal a protective effect of HFD in female mice. In contrast, CD did not exert any protective effects.

CONCLUSIONS

This study demonstrates a specific sexual dimorphism in MFS mice, with HFD exerting an explicit protective effect on severity of aortic disease in female mice. These preclinical data may be useful for developing nutritional recommendations for individuals with MFS in the longer term.

Ascending aortic aneurysm and histopathology in Alport syndrome: a case report

BACKGROUND

Alport syndrome (AS) is caused by mutations in type IV collagen genes that typically target and compromise the integrity of basement membranes in kidney, ocular, and sensorineural cochlear tissues. Type IV and V collagens are also integral components of arterial walls, and whereas collagenopathies including AS are implicated in aortic disease, the incidence of aortic aneurysm in AS is unknown probably because of underreporting. Consequently, AS is not presently considered an independent risk factor for aortic aneurysm and more detailed case studies including histological evidence of basement membrane abnormalities are needed to determine such a possible linkage.

CASE PRESENTATION

Here, we present unique histopathological findings of an ascending aortic aneurysm collected at the time of surgery from an AS patient wherein hypertension was the only other known risk factor.

CONCLUSIONS

The studies reveal classical histological features of aortic aneurysm, including atheroma, lymphocytic infiltration, elastin disruption, and myxoid degeneration with probable AS association.

Vascular smooth muscle-specific YAP/TAZ deletion triggers aneurysm development in mouse aorta

Inadequate adaption to mechanical forces, including blood pressure, contributes to development of arterial aneurysms. Recent studies have pointed to a mechanoprotective role of YAP and TAZ in vascular smooth muscle cells (SMCs). Here, we identified reduced expression of YAP1 in human aortic aneurysms. Vascular SMC-specific knockouts (KOs) of YAP/TAZ were thus generated using the integrin α8-Cre (Itga8-Cre) mouse model (i8-YT-KO). i8-YT-KO mice spontaneously developed aneurysms in the abdominal aorta within 2 weeks of KO induction and in smaller arteries at later times. The vascular specificity of Itga8-Cre circumvented gastrointestinal effects. Aortic aneurysms were characterized by elastin disarray, SMC apoptosis, and accumulation of proteoglycans and immune cell populations. RNA sequencing, proteomics, and myography demonstrated decreased contractile differentiation of SMCs and impaired vascular contractility. This associated with partial loss of myocardin expression, reduced blood pressure, and edema. Mediators in the inflammatory cGAS/STING pathway were increased. A sizeable increase in SOX9, along with several direct target genes, including aggrecan (Acan), contributed to proteoglycan accumulation. This was the earliest detectable change, occurring 3 days after KO induction and before the proinflammatory transition. In conclusion, Itga8-Cre deletion of YAP and TAZ represents a rapid and spontaneous aneurysm model that recapitulates features of human abdominal aortic aneurysms.

Lineage-Specific Induced Pluripotent Stem Cell-Derived Smooth Muscle Cell Modeling Predicts Integrin Alpha-V Antagonism Reduces Aortic Root Aneurysm Formation in Marfan Syndrome Mice

BACKGROUND

The role of increased smooth muscle cell (SMC) integrin αv signaling in Marfan syndrome (MFS) aortic aneurysm remains unclear. Herein, we examine the mechanism and potential efficacy of integrin αv blockade as a therapeutic strategy to reduce aneurysm progression in MFS.

METHODS

Induced pluripotent stem cells (iPSCs) were differentiated into aortic SMCs of the second heart field (SHF) and neural crest (NC) lineages, enabling in vitro modeling of MFS thoracic aortic aneurysms. The pathological role of integrin αv during aneurysm formation was confirmed by blockade of integrin αv with GLPG0187 in Fbn1C1039G/+ MFS mice.

RESULTS

iPSC-derived MFS SHF SMCs overexpress integrin αv relative to MFS NC and healthy control SHF cells. Furthermore, integrin αv downstream targets (FAK [focal adhesion kinase]/AktThr308/mTORC1 [mechanistic target of rapamycin complex 1]) were activated, especially in MFS SHF. Treatment of MFS SHF SMCs with GLPG0187 reduced p-FAK/p-AktThr308/mTORC1 activity back to control SHF levels. Functionally, MFS SHF SMCs had increased proliferation and migration compared to MFS NC SMCs and control SMCs, which normalized with GLPG0187 treatment. In the Fbn1C1039G/+ MFS mouse model, integrin αv, p-AktThr308, and downstream targets of mTORC1 proteins were elevated in the aortic root/ascending segment compared to littermate wild-type control. Mice treated with GLPG0187 (age 6-14 weeks) had reduced aneurysm growth, elastin fragmentation, and reduction of the FAK/AktThr308/mTORC1 pathway. GLPG0187 treatment reduced the amount and severity of SMC modulation assessed by single-cell RNA sequencing.

CONCLUSIONS

The integrin αv-FAK-AktThr308 signaling pathway is activated in iPSC SMCs from MFS patients, specifically from the SHF lineage. Mechanistically, this signaling pathway promotes SMC proliferation and migration in vitro. As biological proof of concept, GLPG0187 treatment slowed aneurysm growth and p-AktThr308 signaling in Fbn1C1039G/+ mice. Integrin αv blockade via GLPG0187 may be a promising therapeutic approach to inhibit MFS aneurysmal growth.

Phospholipase Cε insufficiency causes ascending aortic aneurysm and dissection

Phospholipase Cε (PLCε) is a phospholipase C isoform with a wide range of physiological functions. It has been implicated in aortic valve disorders, but its role in frequently associated aortic disease remains unclear. To determine the role of PLCε in thoracic aortic aneurysm and dissection (TAAD) we used PLCε-deficient mice, which develop aortic valve insufficiency and exhibit aortic dilation of the ascending thoracic aorta and arch without histopathological evidence of injury. Fourteen days of infusion of Plce1+/+ and Plce1-/- mice with angiotensin II (ANG II), which induces aortic dilation and dissection, led to sudden death secondary to ascending aortic dissection in 43% of Plce1-/- versus 5% of Plce1+/+ mice (P < 0.05). Medial degeneration and TAAD were detected in 80% of Plce1-/- compared with 10% of Plce1+/+ mice (P < 0.05) after 4 days of ANG II. Treatment with ANG II markedly increased PLCε expression within the ascending aortic adventitia. Total RNA sequencing demonstrated marked upregulation of inflammatory and fibrotic pathways mediated by interleukin-1β, interleukin-6, and tumor necrosis factor-α. In silico analysis of whole exome sequences of 258 patients with type A dissection identified 5 patients with nonsynonymous PLCE1 variants. Our data suggest that PLCε deficiency plays a role in the development of TAAD and aortic insufficiency.NEW & NOTEWORTHY We describe a novel phenotype by which PLCε deficiency predisposes to aortic valve insufficiency and ascending aortic aneurysm, dissection, and sudden death in the setting of ANG II-mediated hypertension. We demonstrate PLCE1 variants in patients with type A aortic dissection and aortic insufficiency, suggesting that PLCE1 may also play a role in human aortic disease. This finding is of very high significance because it has not been previously demonstrated that PLCε directly mediates aortic dissection.

Allopurinol blocks aortic aneurysm in a mouse model of Marfan syndrome via reducing aortic oxidative stress

BACKGROUND

Increasing evidence indicates that redox stress participates in MFS aortopathy, though its mechanistic contribution is little known. We reported elevated reactive oxygen species (ROS) formation and NADPH oxidase NOX4 upregulation in MFS patients and mouse aortae. Here we address the contribution of xanthine oxidoreductase (XOR), which catabolizes purines into uric acid and ROS in MFS aortopathy.

METHODS AND RESULTS

In aortic samples from MFS patients, XOR protein expression, revealed by immunohistochemistry, increased in both the tunicae intima and media of the dilated zone. In MFS mice (Fbn1^C1041G/+), aortic XOR mRNA transcripts and enzymatic activity of the oxidase form (XO) were augmented in the aorta of 3-month-old mice but not in older animals. The administration of the XOR inhibitor allopurinol (ALO) halted the progression of aortic root aneurysm in MFS mice. ALO administrated before the onset of the aneurysm prevented its subsequent development. ALO also inhibited MFS-associated endothelial dysfunction as well as elastic fiber fragmentation, nuclear translocation of pNRF2 and increased 3'-nitrotyrosine levels, and collagen maturation remodeling, all occurring in the tunica media. ALO reduced the MFS-associated large aortic production of H₂O₂, and NOX4 and MMP2 transcriptional overexpression.

CONCLUSIONS

Allopurinol interferes in aortic aneurysm progression acting as a potent antioxidant. This study strengthens the concept that redox stress is an important determinant of aortic aneurysm formation and progression in MFS and warrants the evaluation of ALO therapy in MFS patients.

Embryologic Origin Influences Smooth Muscle Cell Phenotypic Modulation Signatures in Murine Marfan Syndrome Aortic Aneurysm

BACKGROUND

Aortic root smooth muscle cells (SMC) develop from both the second heart field (SHF) and neural crest. Disparate responses to disease-causing Fbn1 variants by these lineages are proposed to promote focal aortic root aneurysm formation in Marfan syndrome (MFS), but lineage-stratified SMC analysis in vivo is lacking.

METHODS

We generated SHF lineage-traced MFS mice and performed integrated multiomic (single-cell RNA and assay for transposase-accessible chromatin sequencing) analysis stratified by embryological origin. SMC subtypes were spatially identified via RNA in situ hybridization. Response to TWIST1 overexpression was determined via lentiviral transduction in human aortic SMCs.

RESULTS

Lineage stratification enabled nuanced characterization of aortic root cells. We identified heightened SHF-derived SMC heterogeneity including a subset of Tnnt2 (cardiac troponin T)-expressing cells distinguished by altered proteoglycan expression. MFS aneurysm-associated SMC phenotypic modulation was identified in both SHF-traced and nontraced (neural crest-derived) SMCs; however, transcriptomic responses were distinct between lineages. SHF-derived modulated SMCs overexpressed collagen synthetic genes and small leucine-rich proteoglycans while nontraced SMCs activated chondrogenic genes. These modulated SMCs clustered focally in the aneurysmal aortic root at the region of SHF/neural crest lineage overlap. Integrated RNA-assay for transposase-accessible chromatin analysis identified enriched Twist1 and Smad2/3/4 complex binding motifs in SHF-derived modulated SMCs. TWIST1 overexpression promoted collagen and SLRP gene expression in vitro, suggesting TWIST1 may drive SHF-enriched collagen synthesis in MFS aneurysm.

CONCLUSIONS

SMCs derived from both SHF and neural crest lineages undergo phenotypic modulation in MFS aneurysm but are defined by subtly distinct transcriptional responses. Enhanced TWIST1 transcription factor activity may contribute to enriched collagen synthetic pathways SHF-derived SMCs in MFS.

Inhibition of endothelial Nox2 activation by LMH001 protects mice from angiotensin II-induced vascular oxidative stress, hypertension and aortic aneurysm

Endothelial oxidative stress and inflammation attributable to the activation of a Nox2-NADPH oxidase are key features of many cardiovascular diseases. Here, we report a novel small chemical compound (LMH001, MW = 290.079), by blocking phosphorylated p47^phox interaction with p22^phox, inhibited effectively angiotensin II (AngII)-induced endothelial Nox2 activation and superoxide production at a small dose (IC50 = 0.25 μM) without effect on peripheral leucocyte oxidative response to pathogens. The therapeutic potential of LMH001 was tested using a mouse model (C57BL/6J, 7-month-old) of AngII infusion (0.8 mg/kg/d, 14 days)-induced vascular oxidative stress, hypertension and aortic aneurysm. Age-matched littermates of p47^phox knockout mice were used as controls of Nox2 inhibition. LMH001 (2.5 mg/kg/d, ip. once) showed no effect on control mice, but inhibited completely AngII infusion-induced excess ROS production in vital organs, hypertension, aortic walls inflammation and reduced incidences of aortic aneurysm. LMH001 effects on reducing vascular oxidative stress was due to its inhibition of Nox2 activation and was abrogated by knockout of p47^phox. LMH001 has the potential to be developed as a novel drug candidate to treat oxidative stress-related cardiovascular diseases.

Ciprofloxacin accelerates aortic enlargement and promotes dissection and rupture in Marfan mice

OBJECTIVE

Aortic aneurysm and dissection are major life-threatening complications of Marfan syndrome. Avoiding factors that promote aortic damage is critical in managing the care of these patients. Findings from clinical and animal studies raise concerns regarding fluoroquinolone use in patients at risk for aortic aneurysm and dissection. Therefore, we examined the effects of ciprofloxacin on aortic aneurysm and dissection development in Marfan mice.

METHODS

Eight-week-old Marfan mice (Fbn1C1041G/+) were given ciprofloxacin (100 mg/kg/d; n = 51) or vehicle (n = 59) for 4 weeks. Mice were monitored for 16 weeks. Aortic diameters were measured by using ultrasonography, and aortic structure was examined by using histopathologic and immunostaining analyses.

RESULTS

Vehicle-treated Fbn1C1041G/+ mice showed progressive aortic enlargement, with aortic rupture occurring in 5% of these mice. Compared with vehicle-treated Fbn1C1041G/+ mice, ciprofloxacin-treated Fbn1C1041G/+ mice showed accelerated aortic enlargement (P = .01) and increased incidences of aortic dissection (25% vs 47%, P = .03) and rupture (5% vs 25%, P = .005). Furthermore, ciprofloxacin-treated Fbn1C1041G/+ mice had higher levels of elastic fiber fragmentation, matrix metalloproteinase expression, and apoptosis than did vehicle-treated Fbn1C1041G/+ mice.

CONCLUSIONS

Ciprofloxacin accelerates aortic root enlargement and increases the incidence of aortic dissection and rupture in Marfan mice, partially by suppressing lysyl oxidase expression and further compromising the inherited defect in aortic elastic fibers. Our findings substantiate that ciprofloxacin should be avoided in patients with Marfan syndrome.

Deep learning enables genetic analysis of the human thoracic aorta

Enlargement or aneurysm of the aorta predisposes to dissection, an important cause of sudden death. We trained a deep learning model to evaluate the dimensions of the ascending and descending thoracic aorta in 4.6 million cardiac magnetic resonance images from the UK Biobank. We then conducted genome-wide association studies in 39,688 individuals, identifying 82 loci associated with ascending and 47 with descending thoracic aortic diameter, of which 14 loci overlapped. Transcriptome-wide analyses, rare-variant burden tests and human aortic single nucleus RNA sequencing prioritized genes including SVIL, which was strongly associated with descending aortic diameter. A polygenic score for ascending aortic diameter was associated with thoracic aortic aneurysm in 385,621 UK Biobank participants (hazard ratio = 1.43 per s.d., confidence interval 1.32-1.54, P = 3.3 × 10-20). Our results illustrate the potential for rapidly defining quantitative traits with deep learning, an approach that can be broadly applied to biomedical images.

Roles of mTOR in thoracic aortopathy understood by complex intracellular signaling interactions

Thoracic aortopathy–aneurysm, dissection, and rupture–is increasingly responsible for significant morbidity and mortality. Advances in medical genetics and imaging have improved diagnosis and thus enabled earlier prophylactic surgical intervention in many cases. There remains a pressing need, however, to understand better the underlying molecular and cellular mechanisms with the hope of finding robust pharmacotherapies. Diverse studies in patients and mouse models of aortopathy have revealed critical changes in multiple smooth muscle cell signaling pathways that associate with disease, yet integrating information across studies and models has remained challenging. We present a new quantitative network model that includes many of the key smooth muscle cell signaling pathways and validate the model using a detailed data set that focuses on hyperactivation of the mechanistic target of rapamycin (mTOR) pathway and its inhibition using rapamycin. We show that the model can be parameterized to capture the primary experimental findings both qualitatively and quantitatively. We further show that simulating a population of cells by varying receptor reaction weights leads to distinct proteomic clusters within the population, and that these clusters emerge due to a bistable switch driven by positive feedback in the PI3K/AKT/mTOR signaling pathway.

Cell signaling drives changes across scales, from altered transcription at the single-cell level to tissue-level growth and remodeling. Studying complex interactions within cell signaling pathways can lead to a better understanding of the progression of disease. In particular, we are interested in how vascular cells can change their phenotype in a way that exacerbates aortopathy, namely, the development of aneurysms, dissections, and rupture. In this study we built a novel cell signaling network model of a vascular smooth muscle cell using archival data and used it to capture the effects of a genetic knock-out and subsequent pharmacologic rescue. We then used the model to simulate populations of smooth muscle cells and found that small perturbations to the strength of signaling can lead to distinct clusters of cells. With further analysis of the network substructures, we found that a positive feedback loop within the network was responsible for the distinct phenotypes we saw in our clusters of simulated cells. We believe that this work not only helps us to understand changes in smooth muscle cell phenotype but also opens the possibility to study other signaling perturbations associated with aortopathy.

Molecular and Cellular Dynamics of Aortic Aneurysms Revealed by Single-Cell Transcriptomics

The aorta is highly heterogeneous, containing many different types of cells that perform sophisticated functions to maintain aortic homeostasis. Recently, single-cell RNA sequencing studies have provided substantial new insight into the heterogeneity of vascular cell types, the comprehensive molecular features of each cell type, and the phenotypic interrelationship between these cell populations. This new information has significantly improved our understanding of aortic biology and aneurysms at the molecular and cellular level. Here, we summarize these findings, with a focus on what single-cell RNA sequencing analysis has revealed about cellular heterogeneity, cellular transitions, communications among cell populations, and critical transcription factors in the vascular wall. We also review the information learned from single-cell RNA sequencing that has contributed to our understanding of the pathogenesis of vascular disease, such as the identification of cell types in which aneurysm-related genes and genetic variants function. Finally, we discuss the challenges and future directions of single-cell RNA sequencing applications in studies of aortic biology and diseases.

Anti-TGFβ (Transforming Growth Factor β) Therapy With Betaglycan-Derived P144 Peptide Gene Delivery Prevents the Formation of Aortic Aneurysm in a Mouse Model of Marfan Syndrome

Objective

We investigated the effect of a potent TGFβ (transforming growth factor β) inhibitor peptide (P144) from the betaglycan/TGFβ receptor III on aortic aneurysm development in a Marfan syndrome mouse model.

Approach and Results

We used a chimeric gene encoding the P144 peptide linked to apolipoprotein A-I via a flexible linker expressed by a hepatotropic adeno-associated vector. Two experimental approaches were performed: (1) a preventive treatment where the vector was injected before the onset of the aortic aneurysm (aged 4 weeks) and followed-up for 4 and 20 weeks and (2) a palliative treatment where the vector was injected once the aneurysm was formed (8 weeks old) and followed-up for 16 weeks. We evaluated the aortic root diameter by echocardiography, the aortic wall architecture and TGFβ signaling downstream effector expression of pSMAD2 and pERK1/2 by immunohistomorphometry, and Tgfβ1 and Tgfβ2 mRNA expression levels by real-time polymerase chain reaction. Marfan syndrome mice subjected to the preventive approach showed no aortic dilation in contrast to untreated Marfan syndrome mice, which at the same end point age already presented the aneurysm. In contrast, the palliative treatment with P144 did not halt aneurysm progression. In all cases, P144 improved elastic fiber morphology and normalized pERK1/2-mediated TGFβ signaling. Unlike the palliative treatment, the preventive treatment reduced Tgfβ1 and Tgfβ2 mRNA levels.

Conclusions

P144 prevents the onset of aortic aneurysm but not its progression. Results indicate the importance of reducing the excess of active TGFβ signaling during the early stages of aortic disease progression.

Effect of miR-126 on the Proliferation and Migration of Vascular Smooth Muscle Cells in Aortic Aneurysm Mice Under PI3K/AKT/mTOR Signaling Pathway

This paper is to investigate the expression changes of Phosphatidylinositol-3 Kinase (PI3K), protein kinase B (AKT), and Mammalian Target of Rapamycin (mTOR) in Vascular Smooth Muscle Cells (VSMCs) of aortic aneurysm mice, and to analyze the mechanism of VSMCs proliferation and migration. Aortic VSMCs cells were cultured using BALB/c mice as the research object. VSMCs were identified using artificial intelligence-based digital microscopy equipment, and liposome-transfected VSMCs experiments were performed. Real-time PCR was used for the mRNA expression levels of miR-126 and Phosphatase and Tensin Homolog (PTEN). Western blot was used for the protein expression levels of PTEN, PI3K, AKT, and mTOR. The cultured cells were identified as mouse VSMCs using digital microscopes based on artificial intelligence. Compared with the normal group, the expression of miR-126 and PTEN mRNA in the model group were significantly increased and reduced, respectively. Compared with the model group, the expression level of miR-126 and PTEN mRNA in the inhibitor group were significantly reduced and increased, respectively. Compared with the model group, the expression of miR-126 and PTEN mRNA in the ursolic acid group was significantly reduced and increased, respectively. After liposome transfection, compared with the normal group, the expression of PTEN protein in the model group was significantly reduced, and the expression of PI3K protein was significantly increased. Compared with the model group, the expression of PTEN protein was significantly increased and the expression of PI3K protein was significantly decreased in the transfection group. Compared with the control group, the expression of PI3K, AKT and mTOR protein in the model group was significantly increased. Compared with the model group, the expression of PI3K, AKT, and mTOR protein in the ursolic acid group was significantly reduced. The expressions of PI3K, AKT and mTOR protein in PI3K inhibitor group and AKT inhibitor group were significantly reduced. In conclusion, ursolic acid can inhibit the proliferation and migration of VSMCs in aortic aneurysm mice through the miR-126/PTEN/PI3K/AKT/mTOR signaling pathway. Furthermore, PTEN gene and miR-126 negatively regulate PI3K/AKT/mTOR and PTEN/PI3K/AKT/mTOR signaling pathway, respectively .

Loss of Transforming Growth Factor Beta Signaling in Aortic Smooth Muscle Cells Causes Endothelial Dysfunction and Aortic Hypercontractility

[Figure: see text].

Identification of Molecular Regulatory Features and Markers for Acute Type A Aortic Dissection

BACKGROUND

Acute type A aortic dissection (ATAAD) is one of the most lethal cardiovascular diseases, and its molecular mechanism remains unclear.

METHODS

Differentially expressed genes (DEGs) between ATAAD and control were detected by limma R package in GSE52093, GSE153434, GSE98770, and GSE84827, respectively. The coexpression network of DEGs was identified by the WGCNA package. Enrichment analysis was performed for module genes that were positively correlated with ATAAD using clusterProfiler R package. In addition, differentially methylated markers between aortic dissection and control were identified by ChAMP package. After comparing with ATAAD-related genes, a protein-protein interaction (PPI) network was established based on the STRING database. The genes with the highest connectivity were identified as hub genes. Finally, differential immune cell infiltration between ATAAD and control was identified by ssGSEA.

RESULTS

From GSE52093 and GSE153434, 268 module genes were obtained with consistent direction of differential expression and high correlation with ATAAD. They were significantly enriched in T cell activation, HIF-1 signaling pathway, and cell cycle. In addition, 2060 differentially methylated markers were obtained from GSE84827. Among them, 77 methylation markers were ATAAD-related DEGs. Using the PPI network, we identified MYC, ITGA2, RND3, BCL2, and PHLPP2 as hub genes. Finally, we identified significantly differentially infiltrated immune cells in ATAAD.

CONCLUSION

The hub genes we identified may be regulated by methylation and participate in the development of ATAAD through immune inflammation and oxidative stress response. The findings may provide new insights into the molecular mechanisms and therapeutic targets for ATAAD.

P-Selectin Glycoprotein Ligand-1 Deficiency Protects Against Aortic Aneurysm Formation Induced by DOCA Plus Salt

PURPOSE

P-selectin glycoprotein ligand-1 (PSGL-1) acts as a crucial regulator for the inflammatory cells infiltration by mediating the adhesion of leukocytes. However, the role of PSGL-1 in aortic aneurysm remains elusive. Here, we investigated the role of PSGL-1 in aortic aneurysm (AA) development.

METHODS

We first detected PSGL-1 expression in samples from aortic aneurysm patients and mouse AA models via western blotting, immunofluorescence, and flow cytometry, and then we used global PSGL-1 knockout mice and their wild type controls to establish an aortic aneurysm model induced by deoxycorticosterone acetate (DOCA) plus high salt (HS). The incidence, fatality rates, and the pathological changes of aortic aneurysm were analyzed in each group. The inflammation, adhesion molecules expression, and PSGL-1 mediated leukocyte-endothelial adhesion and their underlying mechanisms were explored further.

RESULTS

Increased PSGL-1 levels were observed in human and mouse aortic aneurysm, and on leukocytes of mice treated with DOCA+HS. PSGL-1 deficiency reduced the incidence and severity of aortic aneurysm significantly, as well as decreased elastin fragmentation, collagen accumulation, and smooth muscle cells degeneration. Mechanistically, the protective effect of PSGL-1 inhibition was mediated by the reduced adhesion molecules, and the subsequently reduced leukocyte-endothelial adhesion through the NF-κB pathway, which finally led to reduced inflammatory cells infiltration and decreased inflammatory factors expression.

CONCLUSION

PSGL-1 deficiency is protective against inflammatory cells migration and recruitment in the condition of AA through attenuation of leukocyte-endothelial adhesion. Inhibition of PSGL-1 may be a potential therapeutic target for the prevention and treatment of human AA.

Single-Cell Transcriptomic Profiling of Vascular Smooth Muscle Cell Phenotype Modulation in Marfan Syndrome Aortic Aneurysm

OBJECTIVE

To delineate temporal and spatial dynamics of vascular smooth muscle cell (SMC) transcriptomic changes during aortic aneurysm development in Marfan syndrome (MFS). Approach and Results: We performed single-cell RNA sequencing to study aortic root/ascending aneurysm tissue from Fbn1C1041G/+ (MFS) mice and healthy controls, identifying all aortic cell types. A distinct cluster of transcriptomically modulated SMCs (modSMCs) was identified in adult Fbn1C1041G/+ mouse aortic aneurysm tissue only. Comparison with atherosclerotic aortic data (ApoE-/- mice) revealed similar patterns of SMC modulation but identified an MFS-specific gene signature, including plasminogen activator inhibitor-1 (Serpine1) and Kruppel-like factor 4 (Klf4). We identified 481 differentially expressed genes between modSMC and SMC subsets; functional annotation highlighted extracellular matrix modulation, collagen synthesis, adhesion, and proliferation. Pseudotime trajectory analysis of Fbn1C1041G/+ SMC/modSMC transcriptomes identified genes activated differentially throughout the course of phenotype modulation. While modSMCs were not present in young Fbn1C1041G/+ mouse aortas despite small aortic aneurysm, multiple early modSMCs marker genes were enriched, suggesting activation of phenotype modulation. modSMCs were not found in nondilated adult Fbn1C1041G/+ descending thoracic aortas. Single-cell RNA sequencing from human MFS aortic root aneurysm tissue confirmed analogous SMC modulation in clinical disease. Enhanced expression of TGF-β (transforming growth factor beta)-responsive genes correlated with SMC modulation in mouse and human data sets.

CONCLUSIONS

Dynamic SMC phenotype modulation promotes extracellular matrix substrate modulation and aortic aneurysm progression in MFS. We characterize the disease-specific signature of modSMCs and provide temporal, transcriptomic context to the current understanding of the role TGF-β plays in MFS aortopathy. Collectively, single-cell RNA sequencing implicates TGF-β signaling and Klf4 overexpression as potential upstream drivers of SMC modulation.

Functional characterization and circulating expression profile of dysregulated microRNAs in BAV-associated aortopathy

Compelling evidence has shown that microRNAs (miRs) are involved in the pathophysiology of BAV-associated aortopathy. The purpose of this study was to assess the biological role as well as the circulating expression of two miRs (miR-424-3p and miR-3688-3p) that have been previously identified as significantly dysregulated in thoracic aortic aneurysm specimens of BAV patients. Bioinformatic tools were used to predict miR gene targets followed by functional validation transfecting synthetic miR mimics and negative controls into human aortic smooth muscle cells (HASMCs). Levels of miRs and target genes were evaluated by qRT-PCR. The circulating miR expression profile analysis was assessed on plasma samples collected from a cohort of 72 patients with aortopathy including 39 BAV (33 males; 58 ± 13 years) and 33 TAV patients (26 males; 67 ± 9 years). Computational analysis revealed that SMAD7 and YAP1 were potential targets of miR-424-3p and miR-3688-3p, respectively. Transfection with mimics confirmed a significantly decreased gene expression of SMAD7 and YAP1 compared to mimic negative control (p = 0.04 and p = 0.0005, respectively) or blank control (p = 0.01 and p = 0.0007, respectively). Overexpression of miR-3688-3p also significantly upregulated pro-apoptotic caspase-3 gene expression compared to mimic negative control (p = 0.02) or blank control (p = 0.01). Furthermore, a significant down-regulation of the circulating miR-424-3p was observed in BAV compared to TAV patients (p = 0.001). In multiple linear regression analysis, the aortic valve morphology (β = - 0.29, p = 0.04) and the presence of aortic stenosis (β = - 0.28, p = 0.03) had a significant effect on the miR-424-3p expression. In conclusion, our study demonstrated that miR-424-3p and miR-3688-3p directly targeted SMAD7 and YAP1 in HASMCs, pivotal genes of the TGF-β and Hippo-signaling pathways. Circulating miR-424-3p was also found to be significantly decreased in BAV patients when compared to TAV patients, especially in patients with aortic stenosis. Further large studies of well-characterized BAV patient cohorts are needed to define the clinical significance of the miR-424-3p.

Novel mediators of aneurysm progression in bicuspid aortic valve disease

Bicuspid aortic valve (BAV) disease is a congenital abnormality that is associated with ascending aortic aneurysm yet many of the molecular mechanisms remain unknown. To identify novel molecular mechanisms of aneurysm formation we completed microarray analysis of the proximal (severely dilated) and distal (less dilated) regions of the ascending aorta from five patients with BAV. We identified 180 differentially expressed genes, 40 of which were validated by RT-qPCR. Most genes had roles in inflammation and endothelial cell function including cytokines and growth factors, cell surface receptors and the Activator Protein 1 (AP-1) transcription factor family (FOS, FOSB and JUN) which was chosen for further study. AP-1 was differentially expressed within paired BAV aneurysmal samples (n = 8) but not Marfan patients (n = 5). FOS protein was significantly enriched in BAV aortas compared to normal aortas but unexpectedly, ERK1/2 activity, an upstream regulator of FOS was reduced. ERK1/2 activity was restored when BAV smooth muscle cells were cultured in vitro. An mRNA-miRNA network within paired patient samples identified AP-1 as a central hub of miRNA regulation. FOS knockdown in BAV SMCs increased expression of miR-27a, a stretch responsive miRNA. AP-1 and miR-27a were also dysregulated in a mouse model of aortic constriction. In summary, this study identified a central role for AP-1 signaling in BAV aortic dilatation by using paired mRNA-miRNA patient sample. Upstream analysis of AP-1 regulation showed that the ERK1/2 signaling pathway is dysregulated and thus represents a novel chain of mediators of aortic dilatation in BAV which should be considered in future studies.

Variable cardiovascular phenotypes associated with SMAD2 pathogenic variants

SMAD2 is a downstream effector in the TGF-β signaling pathway, which is important for pattern formation and tissue differentiation. Pathogenic variants in SMAD2 have been reported in association with arterial aneurysms and dissections and in large cohorts of subjects with complex congenital heart disease (CHD). We used whole exome sequencing (WES) to investigate the molecular cause of CHD and other congenital anomalies in three probands and of an arterial aneurysm in an additional patient. Patients 1 and 2 presented with complex CHD, developmental delay, seizures, dysmorphic features, short stature, and poor weight gain. Patient 3 was a fetus with complex CHD and heterotaxy. The fourth patient is an adult female with aortic root aneurysm and physical features suggestive of a connective tissue disorder. WES identified pathogenic truncating variants, a splice variant, and a predicted deleterious missense variant in SMAD2. We compare the phenotypes and genotypes in our patients with previously reported cases. Our data suggest two distinct phenotypes associated with pathogenic variants in SMAD2: complex CHD with or without laterality defects and other congenital anomalies, and a late-onset vascular phenotype characterized by arterial aneurysms with connective tissue abnormalities.

Comparative gene array analyses of severe elastic fiber defects in late embryonic and newborn mouse aorta

Elastic fibers provide reversible elasticity to the large arteries and are assembled during development when hemodynamic forces are increasing. Mutations in elastic fiber genes are associated with cardiovascular disease. Mice lacking expression of the elastic fiber genes elastin ( Eln-/-), fibulin-4 ( Efemp2-/-), or lysyl oxidase ( Lox-/-) die at birth with severe cardiovascular malformations. All three genetic knockout models have elastic fiber defects, aortic wall thickening, and arterial tortuosity. However, Eln-/- mice develop arterial stenoses, while Efemp2-/- and Lox-/- mice develop ascending aortic aneurysms. We performed comparative gene array analyses of these three genetic models for two vascular locations and developmental stages to determine differentially expressed genes and pathways that may explain the common and divergent phenotypes. We first examined arterial morphology and wall structure in newborn mice to confirm that the lack of elastin, fibulin-4, or lysyl oxidase expression provided the expected phenotypes. We then compared gene expression levels for each genetic model by three-way ANOVA for genotype, vascular location, and developmental stage. We found three genes upregulated by genotype in all three models, Col8a1, Igfbp2, and Thbs1, indicative of a common response to severe elastic fiber defects in developing mouse aorta. Genes that are differentially regulated by vascular location or developmental stage in all three models suggest mechanisms for location or stage-specific disease pathology. Comparison of signaling pathways enriched in all three models shows upregulation of integrins and matrix proteins involved in early wound healing, but not of mature matrix molecules such as elastic fiber proteins or fibrillar collagens.

Ari-1 Regulates Myonuclear Organization Together with Parkin and Is Associated with Aortic Aneurysms

Nuclei are actively positioned and anchored to the cytoskeleton via the LINC (Linker of Nucleoskeleton and Cytoskeleton) complex. We identified mutations in the Parkin-like E3 ubiquitin ligase Ariadne-1 (Ari-1) that affect the localization and distribution of LINC complex members in Drosophila. ari-1 mutants exhibit nuclear clustering and morphology defects in larval muscles. We show that Ari-1 mono-ubiquitinates the core LINC complex member Koi. Surprisingly, we discovered functional redundancy between Parkin and Ari-1: increasing Parkin expression rescues ari-1 mutant phenotypes and vice versa. We further show that rare variants in the human homolog of ari-1 (ARIH1) are associated with thoracic aortic aneurysms and dissections, conditions resulting from smooth muscle cell (SMC) dysfunction. Human ARIH1 rescues fly ari-1 mutant phenotypes, whereas human variants found in patients fail to do so. In addition, SMCs obtained from patients display aberrant nuclear morphology. Hence, ARIH1 is critical in anchoring myonuclei to the cytoskeleton.

Diabetes Reduces Severity of Aortic Aneurysms Depending on the Presence of Cell Division Autoantigen 1 (CDA1)

Diabetes is a negative risk factor for aortic aneurysm, but the underlying explanation for this phenomenon is unknown. We have previously demonstrated that cell division autoantigen 1 (CDA1), which enhances transforming growth factor-β signaling, is upregulated in diabetes. We hypothesized that CDA1 plays a key role in conferring the protective effect of diabetes against aortic aneurysms. Male wild-type, CDA1 knockout (KO), apolipoprotein E (ApoE) KO, and CDA1/ApoE double-KO (dKO) mice were rendered diabetic. Whereas aneurysms were not observed in diabetic ApoE KO and wild-type mice, 40% of diabetic dKO mice developed aortic aneurysms. These aneurysms were associated with attenuated aortic transforming growth factor-β signaling, reduced expression of various collagens, and increased aortic macrophage infiltration and matrix metalloproteinase 12 expression. In the well-characterized model of angiotensin II-induced aneurysm formation, concomitant diabetes reduced fatal aortic rupture and attenuated suprarenal aortic expansion, changes not seen in dKO mice. Furthermore, aortic CDA1 expression was downregulated ∼70% within biopsies from human abdominal aortic aneurysms. The identification that diabetes is associated with upregulation of vascular CDA1 and that CDA1 deletion in diabetic mice promotes aneurysm formation provides evidence that CDA1 plays a role in diabetes to reduce susceptibility to aneurysm formation.

Unspliced XBP1 Confers VSMC Homeostasis and Prevents Aortic Aneurysm Formation via FoxO4 Interaction

RATIONALE

Although not fully understood, the phenotypic transition of vascular smooth muscle cells exhibits at the early onset of the pathology of aortic aneurysms. Exploring the key regulators that are responsible for maintaining the contractile phenotype of vascular smooth muscle cells (VSMCs) may confer vascular homeostasis and prevent aneurysmal disease. XBP1 (X-box binding protein 1), which exists in a transcriptionally inactive unspliced form (XBP1u) and a spliced active form (XBP1s), is a key component in response to endoplasmic reticular stress. Compared with XBP1s, little is known about the role of XBP1u in vascular homeostasis and disease.

OBJECTIVE

We aim to investigate the role of XBP1u in VSMC phenotypic switching and the pathogenesis of aortic aneurysms.

METHODS AND RESULTS

XBP1u, but not XBP1s, was markedly repressed in the aorta during the early onset of aortic aneurysm in both angiotensin II-infused apolipoprotein E knockout (ApoE-/-) and CaPO4 (calcium phosphate)-induced C57BL/6J murine models, in parallel with a decrease in smooth muscle cell contractile apparatus proteins. In vivo studies revealed that XBP1 deficiency in smooth muscle cells caused VSMC dedifferentiation, enhanced vascular inflammation and proteolytic activity, and significantly aggravated both thoracic and abdominal aortic aneurysms in mice. XBP1 deficiency, but not an inhibition of XBP1 splicing, induced VSMC switching from the contractile phenotype to a proinflammatory and proteolytic phenotype. Mechanically, in the cytoplasm, XBP1u directly associated with the N terminus of FoxO4 (Forkhead box protein O 4), a recognized repressor of VSMC differentiation via the interaction and inhibition of myocardin. Blocking the XBP1u-FoxO4 interaction facilitated nuclear translocation of FoxO4, repressed smooth muscle cell marker genes expression, promoted proinflammatory and proteolytic phenotypic transitioning in vitro, and stimulated aortic aneurysm formation in vivo.

CONCLUSIONS

Our study revealed the pivotal role of the XBP1u-FoxO4-myocardin axis in maintaining the VSMC contractile phenotype and providing protection from aortic aneurysm formation.

MicroRNA-124 controls human vascular smooth muscle cell phenotypic switch via Sp1

Phenotypic switch of vascular smooth muscle cells (VSMCs) plays an important role in the pathogenesis of atherosclerosis and aortic dissection. However, the mechanisms of phenotypic modulation are still unclear. MicroRNAs have emerged as important regulators of VSMC function. We recently found that microRNA-124 (miR-124) was downregulated in proliferative vascular diseases that were characterized by a VSMC phenotypic switch. Therefore, we speculated that the aberrant expression of miR-124 might play a critical role in human aortic VSMC phenotypic switch. Using quantitative RT-PCR, we found that miR-124 was dramatically downregulated in the aortic media of clinical specimens of the dissected aorta and correlated with molecular markers of the contractile VSMC phenotype. Overexpression of miR-124 by mimicking transfection significantly attenuated platelet-derived growth factor-BB-induced human aortic VSMC proliferation and phenotypic switch. Furthermore, we identified specificity protein 1 (Sp1) as the downstream target of miR-124. A luciferase reporter assay was used to confirm direct miR-124 targeting of the 3'-untranslated region of the Sp1 gene and repression of Sp1 expression in human aortic VSMCs. Furthermore, constitutively active Sp1 in miR-124-overexpressing VSMCs reversed the antiproliferative effects of miR-124. These results demonstrated a novel mechanism of miR-124 modulation of VSMC phenotypic switch by targeting Sp1 expression.NEW & NOTEWORTHY Previous studies have demonstrated that miR-124 is involved in the proliferation of a variety of cell types. However, miRNAs are expressed in a tissue-specific manner. We first identified miR-124 as a critical regulator in human aortic vascular smooth muscle cell differentiation, proliferation, and phenotype switch by targeting the 3'-untranslated region of specificity protein 1.

Vascular remodeling: A redox-modulated mechanism of vessel caliber regulation

Vascular remodeling, i.e. whole-vessel structural reshaping, determines lumen caliber in (patho)physiology. Here we review mechanisms underlying vessel remodeling, with emphasis in redox regulation. First, we discuss confusing terminology and focus on strictu sensu remodeling. Second, we propose a mechanobiological remodeling paradigm based on the concept of tensional homeostasis as a setpoint regulator. We first focus on shear-mediated models as prototypes of remodeling closely dominated by highly redox-sensitive endothelial function. More detailed discussions focus on mechanosensors, integrins, extracellular matrix, cytoskeleton and inflammatory pathways as potential of mechanisms potentially coupling tensional homeostasis to redox regulation. Further discussion of remodeling associated with atherosclerosis and injury repair highlights important aspects of redox vascular responses. While neointima formation has not shown consistent responsiveness to antioxidants, vessel remodeling has been more clearly responsive, indicating that despite the multilevel redox signaling pathways, there is a coordinated response of the whole vessel. Among mechanisms that may orchestrate redox pathways, we discuss roles of superoxide dismutase activity and extracellular protein disulfide isomerase. We then discuss redox modulation of aneurysms, a special case of expansive remodeling. We propose that the redox modulation of vascular remodeling may reflect (1) remodeling pathophysiology is dominated by a particularly redox-sensitive cell type, e.g., endothelial cells (2) redox pathways are temporospatially coordinated at an organ level across distinct cellular and acellular structures or (3) the tensional homeostasis setpoint is closely connected to redox signaling. The mechanobiological/redox model discussed here can be a basis for improved understanding of remodeling and helps clarifying mechanisms underlying prevalent hard-to-treat diseases.

Plk1 regulates contraction of postmitotic smooth muscle cells and is required for vascular homeostasis

Polo-like kinase 1 (PLK1), an essential regulator of cell division, is currently undergoing clinical evaluation as a target for cancer therapy. We report an unexpected function of Plk1 in sustaining cardiovascular homeostasis. Plk1 haploinsufficiency in mice did not induce obvious cell proliferation defects but did result in arterial structural alterations, which frequently led to aortic rupture and death. Specific ablation of Plk1 in vascular smooth muscle cells (VSMCs) led to reduced arterial elasticity, hypotension, and an impaired arterial response to angiotensin II in vivo. Mechanistically, we found that Plk1 regulated angiotensin II-dependent activation of RhoA and actomyosin dynamics in VSMCs in a mitosis-independent manner. This regulation depended on Plk1 kinase activity, and the administration of small-molecule Plk1 inhibitors to angiotensin II-treated mice led to reduced arterial fitness and an elevated risk of aneurysm and aortic rupture. We thus conclude that a partial reduction of Plk1 activity that does not block cell division can nevertheless impair aortic homeostasis. Our findings have potentially important implications for current approaches aimed at PLK1 inhibition for cancer therapy.

In vivo MR-angiography for the assessment of aortic aneurysms in an experimental mouse model on a clinical MRI scanner: Comparison with high-frequency ultrasound and histology

BACKGROUND

MR-angiography currently represents one of the clinical reference-standards for the assessment of aortic-dimensions. For experimental research in mice, dedicated preclinical high-field MRI scanners are used in most studies. This type of MRI scanner is not available in most institutions. The aim of this study was to evaluate the potential of MR-angiography performed on a clinical MR scanner for the assessment of aortic aneurysms in an experimental mouse model, compared to a preclinical high-resolution ultrasound imaging system and histopathology.

METHODS

All in vivo MR imaging was performed with a clinical 3T MRI system (Philips Achieva) equipped with a clinical gradient system in combination with a single-loop surface-coil (47 mm). All MR sequences were based on clinically used sequences. For ultrasound, a dedicated preclinical high-resolution system (30 MHz linear transducer, Vevo770, VisualSonics) was used. All imaging was performed with an ApoE knockout mouse-model for aortic aneurysms. Histopathology was performed as reference-standard at all stages of aneurysm development.

RESULTS

MR-angiography on a clinical 3T system enabled the clear visualization of the aortic lumen and aneurysmal dilation at different stages of aneurysm development. A close correlation (R2 = 0.98; p < 0.001) with histological area measurements was found. Additionally, a good agreement between MR and ultrasound area measurements in systole (R2 = 0.91; p < 0.001) and diastole (R2 = 0.94; p < 0.001) were measured. Regarding interobserver reproducibility, MRI measurements yielded a smaller 95% confidence interval and a closer interreader correlation compared to ultrasound measurements (-0.37-0.46; R2 = 0.97 vs. -0.78-0.88; R2 = 0.87).

CONCLUSION

This study demonstrates that MR-angiography, performed on a clinical 3T MR scanner, enables the reliable detection and quantification of the aortic dilatation at different stages of aneurysm development in an experimental mouse model.

P38 MAPK Signaling Pathway Mediates Angiotensin II-Induced miR143/145 Gene Cluster Downregulation during Aortic Dissection Formation

BACKGROUND

We endeavored to prove that angiotensin II (Ang II) regulates both the expression of micro-RNA143/145 (miR143/145) and differentiation of vascular smooth muscle cells (VSMCs) during the formation of aortic dissection (AD). We also studied the contribution of p38 mitogen-activated protein kinase (MAPK) signaling pathway toward this process.

METHODS

Ascending aortic tissues were harvested from the patients with AD and organ donors. Tissues were immunostained with labeled antibodies targeting p38 MAPK, phospho-p38 MAPK, alpha-smooth muscle actin (α-SMA), and osteopontin (OPN). Next, we treated mouse aortic VSMCs with different regimens of Ang II (duration and dosages) in vitro and determined expression levels of miR143/145 and VSMC phenotype marker proteins (α-SMA and OPN) by quantitative polymerase chain reaction and/or western blotting. SB203580 was used to inhibit the p38 MAPK signaling pathway. Finally, the VSMC phenotype was validated by immunofluorescence microscopy.

RESULTS

Expression of phospho-p38 MAPK was significantly greater in the AD tissue. Ang II induced the phenotypic switching of VSMCs along with the downregulation of an miR143/145 gene cluster. Expression of OPN and phospho-p38 was significantly increased in VSMCs treated with 0.1 μM Ang II for 12 hr. Furthermore, the expression of miR143 and miR145 was downregulated by Ang II treatment. When the p38 MAPK signaling pathway was blocked by pretreatment with an SB203580 inhibitor, the expression of miR143, miR145, and VSMC phenotypic markers was not affected by Ang II. Immunohistochemical staining of aortic tissues donated by AD patients and healthy donors showed that the expression of α-SMA decreased in pathological tissue, while the OPN increased and the arrangement of the smooth muscle cells of the media was dysregulated, which we verified in vitro.

CONCLUSIONS

Ang II could regulate the expression of miR143/145 gene cluster and the phenotypic switching of VSMCs via the p38 MAPK signaling pathway. This may play an important role in the pathogenesis of AD.

Association of the KLK1 rs5516 G allele and the ACE D allele with aortic aneurysm and atherosclerotic stenosis

OBJECTIVE

Atherosclerosis underlies aortic aneurysm (AA) and atherosclerotic stenosis (AS). Kallikrein-1 (KLK1) and angiotensin-converting enzyme (ACE) are 2 key molecules in kallikrein-kinin systems and renin-angiotensin systems, respectively, which are responsible for maintaining vascular balance and stability, playing important roles in atherosclerosis. We aimed to assess the involvement of single nucleotide polymorphism rs5516 in KLK1 as well as the insertion/deletion rs4646994 polymorphism in ACE in the development of AA and AS.

METHODS

We enrolled Chinese Han patients with AA (N = 408) and AS (N = 432), as well as healthy controls (N = 408). Clinical and demographic characteristics were assessed. Genotypes were analyzed with recessive and dominant models.

RESULTS

The rs5516 G allele of KLK1 was significantly associated with AA (P < 0.001), and the D allele of ACE was significantly associated with both AA (P < 0.001) and AS (P < 0.001). The GG and DD genotypes were significantly associated with both AA (P = 0.013) and AS (P < 0.001) in a recessive model, and were synergistic with hypertension in AA patients, but not in AS. Patients with CC/DD, CG/ID, or GG/II genotypes, which were synergistic with hypertension, had a greater risk of developing AA, while CC/DD, CG/DD, GG/ID, or GG/DD genotypes, which were not synergistic with hypertension, contributed to the development of AS.

CONCLUSION

The KLK1 rs5516 G allele is closely associated with AA, and the ACE D allele is closely related to AA and AS.

Defective Connective Tissue Remodeling in Smad3 Mice Leads to Accelerated Aneurysmal Growth Through Disturbed Downstream TGF-β Signaling

Aneurysm-osteoarthritis syndrome characterized by unpredictable aortic aneurysm formation, is caused by SMAD3 mutations. SMAD3 is part of the SMAD2/3/4 transcription factor, essential for TGF-β-activated transcription. Although TGF-β-related gene mutations result in aneurysms, the underlying mechanism is unknown. Here, we examined aneurysm formation and progression in Smad3^-/- animals. Smad3^-/- animals developed aortic aneurysms rapidly, resulting in premature death. Aortic wall immunohistochemistry showed no increase in extracellular matrix and collagen accumulation, nor loss of vascular smooth muscle cells (VSMCs) but instead revealed medial elastin disruption and adventitial inflammation. Remarkably, matrix metalloproteases (MMPs) were not activated in VSMCs, but rather specifically in inflammatory areas. Although Smad3^-/- aortas showed increased nuclear pSmad2 and pErk, indicating TGF-β receptor activation, downstream TGF-β-activated target genes were not upregulated. Increased pSmad2 and pErk staining in pre-aneurysmal Smad3^-/- aortas implied that aortic damage and TGF-β receptor-activated signaling precede aortic inflammation. Finally, impaired downstream TGF-β activated transcription resulted in increased Smad3^-/- VSMC proliferation. Smad3 deficiency leads to imbalanced activation of downstream genes, no activation of MMPs in VSMCs, and immune responses resulting in rapid aortic wall dilatation and rupture. Our findings uncover new possibilities for treatment of SMAD3 patients; instead of targeting TGF-β signaling, immune suppression may be more beneficial.

[THE ROLE OF TRANSFORMING GROWTH FACTOR-B IN IMMUNOPATHOGENESIS OF DISEASES OF CONNECTIVE TISSUE]

The recent studies of molecular physiology of fibrillin and pathophysiology of inherent disorders of structure and function of connective tissue such as dissection and aneurysm of aorta, myxomatously altered cusps and prolapses of mitral valve, syndrome of hyper-mobility of joints, demonstrated that important role in development of these malformations play alterations of transfer of signals by growth factors and matrix cellular interaction. These conditions under manifesting Marfan's syndrome can be a consequence of anomalies of fibrillin-1 which deficiency unbrakes process of activation of transforming growth factor-β (TGFβ). The involvement of TGFβ in pathogenesis of Marfan's syndrome permits consider antagonists of angiotensin-transforming enzymes as potential pharmaceuticals in therapy of this disease. The article presents analysis of publications' data related to this problem.

A disintegrin and metalloproteinase with thrombospondin motif 1 (ADAMTS1) expression increases in acute aortic dissection

Acute aortic dissection (AAD) is a life-threatening cardiovascular disease caused by progressive medial degeneration of the aortic wall. A disintegrin and metalloproteinase with thrombospondin motifs 1 (ADAMTS1) is a recently identified extracellular metalloproteinase participating in the development of vascular disease, such as atherosclerosis. In the present study, we found that ADAMTS1 was significantly elevated in blood samples from AAD patients compared with patients with acute myocardial infarction and healthy volunteers. Based on these findings, we established an AAD model by infusing angiotensin II in older mice. AAD was successfully developed in aorta tissues, with an incidence of 42% after 14 days in the angiotensin II group. Macrophage and neutrophil infiltration was observed in the media of the aorta, and ADAMTS1 overexpression was found in the aorta by Western blot and immunohistochemistry. Double immunofluorescence staining showed the expression of ADAMTS1 in macrophages and neutrophils. Consistent with the upregulation of ADAMTS1 in aortic dissection tissues, versican (a proteoglycan substrate of ADAMTS1) was degraded significantly more in these tissues than in control aortic tissues. These data suggest that the increased expression of ADAMTS1 protein in macrophages and neutrophils that infiltrated aortic tissues may promote the progression of AAD by degrading versican.

Association of relative telomere length with cardiovascular disease in a large chronic kidney disease cohort: the GCKD study

BACKGROUND

Chronic kidney disease (CKD) affects 10-15% of the general population and affected individuals are at an increased risk for cardiovascular disease (CVD). Since telomere length is considered to be involved in biological aging, we tested whether relative telomere length (RTL) might be a marker for these two diseases.

METHODS

The German Chronic Kidney Disease (GCKD) study is an ongoing prospective cohort study including patients with CKD of moderate severity. RTL was measured by qPCR in 4955 out of 5217 GCKD patients at baseline.

RESULTS

RTL was distributed in the cohort with a mean ± SD of 0.95 ± 0.19. CVD was present in 1266 patients. Each decrease of RTL by 0.1 unit was associated with a higher probability for prevalent CVD: OR = 1.06, 95% CI 1.02-1.11, p = 0.007 (adjusted for age, sex, eGFR, BMI, ln-CRP, smoking, hypertension, diabetes, and lipids). Similar findings were observed for history of specific CVD entities, such as coronary artery disease (OR = 1.05, p = 0.025), myocardial infarction (OR = 1.08, p = 0.013) and percutaneous transluminal coronary angioplasty (OR = 1.06, p = 0.032). The strongest associations were found for interventions at the carotid arteries (OR = 1.25, p = 0.001) as well as aortic aneurysms (OR = 1.22, p = 0.001).

CONCLUSIONS

In the presence of CKD there is a significant association between shorter RTL and CVD manifestations. RTL appears to be a marker reflecting changes in homeostasis associated with CKD that may contribute to the excess CVD risk.

Performance comparison of ultrasound-based methods to assess aortic diameter and stiffness in normal and aneurysmal mice

OBJECTIVE

Several ultrasound-based methods are currently used to assess aortic diameter, circumferential strain and stiffness in mice, but none of them is flawless and a gold standard is lacking. We aimed to assess the validity and sensitivity of these methods in control animals and animals developing dissecting abdominal aortic aneurysm.

METHODS AND RESULTS

We first compared systolic and diastolic diameters as well as local circumferential strains obtained in 47 Angiotensin II-infused ApoE(-/-) mice with three different techniques (BMode, short axis MMode, long axis MMode), at two different abdominal aortic locations (supraceliac and paravisceral), and at three different time points of abdominal aneurysm formation (baseline, 14 days and 28 days). We found that short axis BMode was preferred to assess diameters, but should be avoided for strains. Short axis MMode gave good results for diameters but high standard deviations for strains. Long axis MMode should be avoided for diameters, and was comparable to short axis MMode for strains. We then compared pulse wave velocity measurements using global, ultrasound-based transit time or regional, pressure-based transit time in 10 control and 20 angiotensin II-infused, anti-TGF-Beta injected C57BL/6 mice. Both transit-time methods poorly correlated and were not able to detect a significant difference in PWV between controls and aneurysms. However, a combination of invasive pressure and MMode diameter, based on radio-frequency data, detected a highly significant difference in local aortic stiffness between controls and aneurysms, with low standard deviation.

CONCLUSIONS

In small animal ultrasound the short axis view is preferred over the long axis view to measure aortic diameters, local methods are preferred over transit-time methods to measure aortic stiffness, invasive pressure-diameter data are preferred over non-invasive strains to measure local aortic stiffness, and the use of radiofrequency data improves the accuracy of diameter, strain as well as stiffness measurements.

[Novel pharmacological strategies for aortic dilation in Marfan syndrome: from mouse models to human patients]

Marfan syndrome (MS) is a congenital disorder of the connective tissue characterized by aortic dilation with frequent progression to aortic aneurysms requiring surgical intervention. Although mutations in the fibrillin-1 (FBN1) gene have been recognized as the genetic cause of MS a long time ago, only recently deeper knowledge of the molecular mechanisms underlying fibrillin-1 biology and the crucial role of transforming growth factor-β and angiotensin II receptor type 1 antagonists have been elucidated. This review focuses on the most commonly used animal models to investigate the molecular mechanisms underlying MS, and on novel pharmacological strategies to reduce aortic dilation in MS.

The spectrum of FBN1, TGFβR1, TGFβR2 and ACTA2 variants in 594 individuals with suspected Marfan Syndrome, Loeys-Dietz Syndrome or Thoracic Aortic Aneurysms and Dissections (TAAD)

INTRODUCTION

In this study, patients suspected of having a clinical diagnosis of Marfan Syndrome (MFS), Loeys-Dietz Syndrome (LDS) and Thoracic Aortic Aneurysms and Dissections (TAAD) were referred for genetic testing and examined for mutations in the FBN1, TGFβR1, TGFβR2 and ACTA2 genes.

METHODS

We examined 594 samples from unrelated individuals and different combinations of genes were sequenced, including one or more of the following: FBN1, TGFβR1, TGFβR2, ACTA2, and, in some cases, FBN1 was analyzed by MLPA to detect large deletions.

RESULTS

A total of 112 patients had a positive result. Of those, 61 had a clinical diagnosis of MFS, eight had LDS, three had TAAD and 40 patients had clinical features with no specific diagnosis provided. A total of 44 patients had an inconclusive result; of these, 12 patients were referred with a clinical diagnosis of MFS, 4 with LDS and 9 with TAAD and 19 had no clinical diagnosis. A total of 89 mutations were novel.

CONCLUSION

This study reveals the rate of detection of variants in several genes associated with MFS, LDS and TAAD. The evaluation of patients by individuals with expertise in the field may decrease the likelihood of ordering unnecessary molecular testing. Nevertheless, genetic testing supports the diagnosis of MFS, LDS and TAAD.

Current siRNA targets in atherosclerosis and aortic aneurysm

Atherosclerosis (ATH) and aortic aneurysms (AA) remain challenging chronic diseases that confer high morbidity and mortality despite advances in medical, interventional, and surgical care. RNA interference represents a promising technology that may be utilized to silence genes contributing to ATH and AA. Despite positive results in preclinical and some clinical feasibility studies, challenges such as target/sequence validation, tissue specificity, transfection efficiency, and mitigation of unwanted off-target effects remain to be addressed. In this review the most current targets and some novel approaches in siRNA delivery are being discussed. Due to the plethora of investigated targets, only studies published between 2010 and 2014 were included.

[Clinical guideline 'Turner syndrome']

Turner syndrome occurs in women who are missing one X chromosome. The most obvious symptoms are small stature and ovarian failure. Turner patients have an increased risk of a large number of disorders, and should therefore have lifelong medical supervision. Recent insights into patient management have been incorporated into the guidelines. Patients are increasingly involved in their own treatment. In patients with 45,X karyotype, Y-chromosomal material is actively sought in a larger number of cells and/or other tissues, using FISH. Pubertal induction therapy, if required, is initiated at an appropriate age. Egg donation or vitrification are new therapeutic options for fertility treatment. Monitoring for cardiac and vascular disease using cardiac ultrasound and MRI is performed more often, partly in connection with the risk of aortal dissection. The coordination of care of patients with Turner syndrome is concentrated in specialized centres in the Netherlands and Belgium.

Bicuspid aortic valve aortopathy: genetics, pathophysiology and medical therapy

The association between ascending aortic aneurysm (AA) and bicuspid aortic valve (BAV) has been well established. Different genetic, haemodynamic and cardiovascular risk factors have been implicated in the development and progression of AA. However, to date, definite conclusions cannot be drawn regarding the exact molecular, cellular and haemodynamic mechanisms causing BAV-associated aortopathy. For this study, we performed a thorough electronic systematic review of the literature using MEDLINE (1960-2012) and EMBASE databases. MeSH terms included: 'bicuspid aortic valve and ascending aorta', 'bicommissural aortic valve and aneurysm', 'bicuspid aortopathy', 'bicuspid aortic valve pathophysiology', 'bicuspid aortic valve and genetics' and 'bicuspid aortic valve and treatment'. We aim in this review to discuss the mechanisms, pathophysiology, genetics and modern drug therapy in the context of BAV-associated aortopathy.

Expression of matrix metalloproteinase-12 in aortic dissection

BACKGROUND

Aortic dissection(AD) is an acute process of large blood vessels characterized by dangerous pathogenic conditions and high disability and high mortality. The pathogenesis of AD remains debated. Matrix metalloproteinase-12 (MMP-12) participates in many pathological processes such as abdominal aortic aneurysm, atherosclerosis, emphysema and cancer. However, this elastase has rarely been assessed in the presence of AD. The aim of the present study was to investigate the expression of MMP-12 in aortic tissue so as to offer a better understanding of the possible mechanisms of AD.

METHODS

The protein expression levels of MMP-12 were analyzed and compared in aorta tissue and the blood serum samples by reverse transcription polymerase chain reaction(RT-PCR), Western blotting, immuno-histochemistry, fluorescence resonance energy transfer ( FRET ) activity assay and enzyme-linked immuno sorbent assay ( ELISA ), respectively. Ascending aorta tissue specimens were obtained from 12 patients with an acute Stanford A-dissection at the time of aortic replacement, and from 4 patients with coronary artery disease (CAD) undergoing coronary artery bypass surgery. Meanwhile, serum samples were harvested from 15 patients with an acute Stanford A-dissection and 10 healthy individuals who served as the control group.

RESULTS

MMP-12 activity could be detected in both AD and CAD groups, but the level in the AD group was higher than those in the CAD group (P < 0.05). MMP-12 proteolysis existed in both serum samples of the AD and healthy groups, and the activity level in the AD group was clearly higher than in the healthy group (P < 0.05). For AD patients, MMP-12 activity in serum was higher than in the aorta wall (P < 0.05). MMP-12 activity in the aortic wall tissue can be inhibited by MMP inhibitor v (P < 0.05).

CONCLUSION

The present study directly demonstrates that MMP-12 proteolytic activity exists within the aorta specimens and blood samples from aortic dissection patients. MMP-12 might be of potential relevance as a clinically diagnostic tool and therapeutic target in vascular injury and repair.