The Role Matrix Metalloproteinases in the Production of Aortic Aneurysm

Hydrogen Sulfide Ameliorates Heart Aging by Downregulating Matrix Metalloproteinase-9

PURPOSE

Aging contributes significantly to cardiovascular diseases and cardiac dysfunction, leading to the upregulation of matrix metalloproteinase-9 (MMP-9) in the heart and a significant decrease in hydrogen sulfide (H2S) content, coupled with impaired cardiac diastolic function. This study explores whether supplementing exogenous hydrogen sulfide during aging ameliorates the decline in H2S concentration in the heart, suppresses MMP-9 expression, and improves the age-associated impairment in cardiac morphology and function.

METHODS

We collected plasma from healthy individuals of different ages to determine the relationship between aging and H2S and MMP-9 levels through Elisa detection and liquid chromatography-tandem mass spectrometry (LC/MC) detection of plasma H2S content. Three-month-old mice were selected as the young group, while 18-month-old mice were selected as the old group, and sodium hydrosulfide (NaHS) was injected intraperitoneally from 15 months old until 18 months old as the old + NaHS group. Plasma MMP-9 content was detected using Elisa, plasma H2S content, cardiac H2S content, and cystathionine gamma-lyase (CSE) activity were detected using LC/MC, and cardiac function was detected using echocardiography. Heart structure was assessed using hematoxylin and eosin staining, Masone staining was used to detect the degree of cardiac fibrosis, while western blot was used to detect the expression of MMP-9, CSE, and aging marker proteins. Knockdown of MMP-9 and CSE in H9c2 cells using small interfering RNA was carried out to determine the upstream-downstream relationship between MMP-9 and CSE.

RESULTS

H2S content in the plasma of healthy individuals decreases with escalating age, whereas MMP-9 level rises with age progression. Aging leads to a decrease in H2S levels in the heart and plasma of mice, severe impairment of cardiac diastolic function, interstitial relaxation, and fibrosis of the heart. Supplementing with exogenous H2S can improve these phenomena.

CONCLUSION

H2S maintains the structure and function of the heart by inhibiting the expression of MMP-9 during the aging process.

A Novel Strategy for the Treatment of Aneurysms: Inhibition of MMP-9 Activity through the Delivery of TIMP-1 Encoding Synthetic mRNA into Arteries

Aneurysms pose life-threatening risks due to the dilatation of the arteries and carry a high risk of rupture. Despite continuous research efforts, there are still no satisfactory or clinically effective pharmaceutical treatments for this condition. Accelerated inflammatory processes during aneurysm development lead to increased levels of matrix metalloproteinases (MMPs) and destabilization of the vessel wall through the degradation of the structural components of the extracellular matrix (ECM), mainly collagen and elastin. Tissue inhibitors of metalloproteinases (TIMPs) directly regulate MMP activity and consequently inhibit ECM proteolysis. In this work, the synthesis of TIMP-1 protein was increased by the exogenous delivery of synthetic TIMP-1 encoding mRNA into aortic vessel tissue in an attempt to inhibit MMP-9. In vitro, TIMP-1 mRNA transfection resulted in significantly increased TIMP-1 protein expression in various cells. The functionality of the expressed protein was evaluated in an appropriate ex vivo aortic vessel model. Decreased MMP-9 activity was detected using in situ zymography 24 h and 48 h post microinjection of 5 µg TIMP-1 mRNA into the aortic vessel wall. These results suggest that TIMP-1 mRNA administration is a promising approach for the treatment of aneurysms.

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.

FRET Sensor-Modified Synthetic Hydrogels for Real-Time Monitoring of Cell-Derived Matrix Metalloproteinase Activity using Fluorescence Lifetime Imaging

Matrix remodeling plays central roles in a range of physiological and pathological processes and is driven predominantly by the activity of matrix metalloproteinases (MMPs), which degrade extracellular matrix (ECM) proteins. Our understanding of how MMPs regulate cell and tissue dynamics is often incomplete as in vivo approaches are lacking and many in vitro strategies cannot provide high-resolution, quantitative measures of enzyme activity in situ within tissue-like 3D microenvironments. Here, we incorporate a Förster resonance energy transfer (FRET) sensor of MMP activity into fully synthetic hydrogels that mimic many properties of the native ECM. We then use fluorescence lifetime imaging to provide a real-time, fluorophore concentration-independent quantification of MMP activity, establishing a highly accurate, readily adaptable platform for studying MMP dynamics in situ. MCF7 human breast cancer cells encapsulated within hydrogels highlight the detection of MMP activity both locally, at the sub-micron level, and within the bulk hydrogel. Our versatile platform may find use in a range of biological studies to explore questions in the dynamics of cancer metastasis, development, and tissue repair by providing high-resolution, quantitative and in situ readouts of local MMP activity within native tissue-like environments.

Pathogenesis-Guided Rational Engineering of Nanotherapies for the Targeted Treatment of Abdominal Aortic Aneurysm by Inhibiting Neutrophilic Inflammation

Abdominal aortic aneurysm (AAA) remains a fatal disease in the elderly. Currently, no drugs can be clinically used for AAA therapy. Considering the pivotal role of neutrophils in the pathogenesis of AAA, herein we propose the targeted therapy of AAA by site-specifically regulating neutrophilic inflammation. Based on a luminol-conjugated α-cyclodextrin material (LaCD), intrinsically anti-inflammatory nanoparticles (NPs) were engineered by simple nanoprecipitation, which were examined as a nanotherapy (defined as LaCD NP). After efficient accumulation in the aneurysmal aorta and localization in pathologically relevant inflammatory cells in rats with CaCl2-induced AAA, LaCD NP significantly alleviated AAA progression, as implicated by the decreased aortic expansion, suppressed elastin degradation, inhibited calcification, and improved structural integrity of the abdominal aorta. By functionalizing LaCD NP with alendronate, a calcification-targeting moiety, the in vivo aneurysmal targeting capability of LaCD NP was considerably enhanced, thereby affording significantly potentiated therapeutic outcomes in AAA rats. Mechanistically, LaCD NP can effectively inhibit neutrophil-mediated inflammatory responses in the aneurysmal aorta. Particularly, LaCD NP potently attenuated the formation of neutrophil extracellular traps (NETs), thereby suppressing NETs-mediated pro-inflammatory events and NETosis-associated negative effects responsible for AAA progression. Consequently, we demonstrated the effectiveness and underlying mechanisms of anti-NETosis nanotherapies for the targeted treatment of AAA. Our findings provide promising insights into discovering precision therapies for AAA and other inflammatory vascular diseases.

Rapidly Growing and Ruptured Great Saphenous Vein Aneurysm in a Liver Transplant Patient

Venous aneurysms are rare vascular malformations that can lead to significant clinical complications, including thrombosis, pulmonary embolism, rupture, and even fatal outcomes when not promptly and adequately managed. This case report presents a liver transplant patient under immunosuppressive therapy who developed a rapidly progressing great saphenous vein aneurysm, ultimately requiring urgent surgical intervention due to acute bleeding from the ruptured aneurysm. Immunosuppression emerges as a potential key factor in the formation and rapid growth of the aneurysm, with the pathophysiological mechanism potentially involving increased expression of specific matrix metalloproteinases. Further research is warranted to gain a better understanding of the role of immunosuppression in the development of venous aneurysms.

Targeted proteomics and metabolomics for biomarker discovery in abdominal aortic aneurysm and post-EVAR sac volume

BACKGROUND AND AIMS

Abdominal aortic aneurysm (AAA) patients undergo uniform surveillance programs both leading up to, and following surgery. Circulating biomarkers could play a pivotal role in individualizing surveillance. We applied a multi-omics approach to identify relevant biomarkers and gain pathophysiological insights.

MATERIALS AND METHODS

In this cross-sectional study, 108 AAA patients and 200 post-endovascular aneurysm repair (post-EVAR) patients were separately investigated. We performed partial least squares regression and ingenuity pathway analysis on circulating concentrations of 96 proteins (92 Olink Cardiovascular-III panel, 4 ELISA-assays) and 199 metabolites (measured by LC-TQMS), and their associations with CT-based AAA/sac volume.

RESULTS

The median (25th-75th percentile) maximal diameter was 50.0 mm (46.0, 53.0) in the AAA group, and 55.4 mm (45.0, 64.2) in the post-EVAR group. Correcting for clinical characteristics in AAA patients, the aneurysm volume Z-score differed 0.068 (95 %CI: (0.042, 0.093)), 0.066 (0.047, 0.085) and -0.051 (-0.064, -0.038) per Z-score valine, leucine and uPA, respectively. After correcting for clinical characteristics and orthogonalization in the post-EVAR group, the sac volume Z-score differed 0.049 (0.034, 0.063) per Z-score TIMP-4, -0.050 (-0.064, -0.037) per Z-score LDL-receptor, -0.051 (-0.062, -0.040) per Z-score 1-OG/2-OG and -0.056 (-0.066, -0.045) per Z-score 1-LG/2-LG.

CONCLUSIONS

The branched-chain amino acids and uPA were related to AAA volume. For post-EVAR patients, LDL-receptor, monoacylglycerols and TIMP-4 are potential biomarkers for sac volume. Additionally, distinct markers for sac change were identified.

Female-Specific Considerations in Aortic Health and Disease

The aorta plays a central role in the modulation of blood flow to supply end organs and to optimize the workload of the left ventricle. The constant interaction of the arterial wall with protective and deleterious circulating factors, and the cumulative exposure to ventriculoarterial pulsatile load, with its associated intimal-medial changes, are important players in the complex process of vascular aging. Vascular aging is also modulated by biomolecular processes such as oxidative stress, genomic instability, and cellular senescence. Concomitantly with well-established cardiometabolic and sex-specific risk factors and environmental stressors, arterial stiffness is associated with cardiovascular disease, which remains the leading cause of morbidity and mortality in women worldwide. Sexual dimorphisms in aortic health and disease are increasingly recognized and explain-at least in part-some of the observable sex differences in cardiovascular disease, which will be explored in this review. Specifically, we will discuss how biological sex affects arterial health and vascular aging and the implications this has for development of certain cardiovascular diseases uniquely or predominantly affecting women. We will then expand on sex differences in thoracic and abdominal aortic aneurysms, with special considerations for aortopathies in pregnancy.

New Directions in Diagnostics for Aortic Aneurysms: Biomarkers and Machine Learning

This review article presents an appraisal of pioneering technologies poised to revolutionize the diagnosis and management of aortic aneurysm disease, with a primary focus on the thoracic aorta while encompassing insights into abdominal manifestations. Our comprehensive analysis is rooted in an exhaustive survey of contemporary and historical research, delving into the realms of machine learning (ML) and computer-assisted diagnostics. This overview draws heavily upon relevant studies, including Siemens' published field report and many peer-reviewed publications. At the core of our survey lies an in-depth examination of ML-driven diagnostic advancements, dissecting an array of algorithmic suites to unveil the foundational concepts anchoring computer-assisted diagnostics and medical image processing. Our review extends to a discussion of circulating biomarkers, synthesizing insights gleaned from our prior research endeavors alongside contemporary studies gathered from the PubMed Central database. We elucidate the prevalent challenges and envisage the potential fusion of AI-guided aortic measurements and sophisticated ML frameworks with the computational analyses of pertinent biomarkers. By framing current scientific insights, we contemplate the transformative prospect of translating fundamental research into practical diagnostic tools. This narrative not only illuminates present strides, but also forecasts promising trajectories in the clinical evaluation and therapeutic management of aortic aneurysm disease.

The future for the therapeutics of abdominal aortic aneurysm: engineered nanoparticles drug delivery for abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a severe cardiovascular disease with a high mortality rate. Several screening and diagnostic methods have been developed for AAA early diagnosis. Open surgery and endovascular aortic repair (EVAR) are clinically available for patients who meet the indications for surgery. However, for non-surgical patients, limited drugs exist to inhibit or reverse the progression of aneurysms due to the complex pathogenesis and biological structure of AAA, failing to accumulate precisely on the lesion to achieve sufficient concentrations. The recently developed nanotechnology offers a new strategy to address this problem by developing drug-carrying nanoparticles with enhanced water solubility and targeting capacity, prolonged duration, and reduced side effects. Despite the rising popularity, limited literature is available to highlight the progression of the field. Herein, in this review, we first discuss the pathogenesis of AAA, the methods of diagnosis and treatment that have been applied clinically, followed by the review of research progressions of constructing different drug-loaded nanoparticles for AAA treatment using engineered nanoparticles. In addition, the feasibility of extracellular vesicles (EVs) and EVs-based nanotechnology for AAA treatment in recent years are highlighted, together with the future perspective. We hope this review will provide a clear picture for the scientists and clinicians to find a new solution for AAA clinical management.

Pathogenetic Significance of Long Non-Coding RNAs in the Development of Thoracic and Abdominal Aortic Aneurysms

Aortic aneurysm (AA) is a life-threatening condition with a high prevalence and risk of severe complications. The aim of this review was to summarize the data on the role of long non-coding RNAs (lncRNAs) in the development of AAs of various location. Within less than a decade of studies on the role of lncRNAs in AA, using experimental and bioinformatic approaches, scientists have obtained the data confirming the involvement of these molecules in metabolic pathways and pathogenetic mechanisms critical for the aneurysm development. Regardless of the location of pathological process (thoracic or abdominal aorta), AA was found to be associated with changes in the expression of various lncRNAs in the tissue of the affected vessels. The consistency of changes in the expression level of lncRNA, mRNA and microRNA in aortic tissues during AA development has been recordedand regulatory networks implicated in the AA pathogenesis in which lncRNAs act as competing endogenous RNAs (ceRNA networks) have been identified. It was found that the same lncRNA can be involved in different ceRNA networks and regulate different biochemical and cellular events; on the other hand, the same pathological process can be controlled by different lncRNAs. Despite some similarities in pathogenesis and overlapping of involved lncRNAs, the ceRNA networks described for abdominal and thoracic AA are different. Interactions between lncRNAs and other molecules, including those participating in epigenetic processes, have also been identified as potentially relevant to the AA pathogenesis. The expression levels of some lncRNAs were found to correlate with clinically significant aortic features and biochemical parameters. Identification of regulatory RNAs functionally significant in the aneurysm development is important for clarification of disease pathogenesis and will provide a basis for early diagnostics and development of new preventive and therapeutic drugs.

Injectable Shear-Thinning Hydrogels with Sclerosing and Matrix Metalloproteinase Modulatory Properties for the Treatment of Vascular Malformations

Sac embolization of abdominal aortic aneurysms (AAAs) remains clinically limited by endoleak recurrences. These recurrences are correlated with recanalization due to the presence of endothelial lining and matrix metalloproteinases (MMPs)-mediated aneurysm progression. This study incorporated doxycycline (DOX), a well-known sclerosant and MMPs inhibitor, into a shear-thinning biomaterial (STB)-based vascular embolizing hydrogel. The addition of DOX was expected to improve embolizing efficacy while preventing endoleaks by inhibiting MMP activity and promoting endothelial removal. The results showed that STBs containing 4.5% w/w silicate nanoplatelet and 0.3% w/v of DOX were injectable and had a 2-fold increase in storage modulus compared to those without DOX. STB-DOX hydrogels also reduced clotting time by 33% compared to untreated blood. The burst release of DOX from the hydrogels showed sclerosing effects after 6 h in an ex vivo pig aorta model. Sustained release of DOX from hydrogels on endothelial cells showed MMP inhibition (ca. an order of magnitude larger than control groups) after 7 days. The hydrogels successfully occluded a patient-derived abdominal aneurysm model at physiological blood pressures and flow rates. The sclerosing and MMP inhibition characteristics in the engineered multifunctional STB-DOX hydrogels may provide promising opportunities for the efficient embolization of aneurysms in blood vessels.

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.

Evidence Accumulates: Patients with Ascending Aneurysms Are Strongly Protected from Atherosclerotic Disease

Ascending thoracic aortic aneurysms may be fatal upon rupture or dissection and remain a leading cause of death in the developed world. Understanding the pathophysiology of the development of ascending thoracic aortic aneurysms may help reduce the morbidity and mortality of this disease. In this review, we will discuss our current understanding of the protective relationship between ascending thoracic aortic aneurysms and the development of atherosclerosis, including decreased carotid intima-media thickness, low-density lipoprotein levels, coronary and aortic calcification, and incidence of myocardial infarction. We also propose several possible mechanisms driving this relationship, including matrix metalloproteinase proteins and transforming growth factor-β.

Quantitative Magnetic Resonance Imaging to Assess Progression and Rupture Risk of Aortic Aneurysms: A Scoping Review

PURPOSE

In current practice, the diameter of an aortic aneurysm is utilized to estimate the rupture risk and decide upon timing of elective repair, although it is known to be imprecise and not patient-specific. Quantitative magnetic resonance imaging (MRI) enables the visualization of several biomarkers that provide information about processes within the aneurysm and may therefore facilitate patient-specific risk stratification. We performed a scoping review of the literature on quantitative MRI techniques to assess aortic aneurysm progression and rupture risk, summarized these findings, and identified knowledge gaps.

METHODS

Literature concerning primary research was of interest and the medical databases PubMed, Scopus, Embase, and Cochrane were systematically searched. This study used the PRISMA protocol extension for scoping reviews. Articles published between January 2010 and February 2023 involving animals and/or humans were included. Data were extracted by 2 authors using a predefined charting method.

RESULTS

A total of 1641 articles were identified, of which 21 were included in the scoping review. Quantitative MRI-derived biomarkers were categorized into hemodynamic (8 studies), wall (5 studies) and molecular biomarkers (8 studies). Fifteen studies included patients and/or healthy human subjects. Animal models were investigated in the other 6 studies. A cross-sectional study design was the most common, whereas 5 animal studies had a longitudinal component and 2 studies including patients had a prospective design. A promising hemodynamic biomarker is wall shear stress (WSS), which is estimated based on 4D-flow MRI. Molecular biomarkers enable the assessment of inflammatory and wall deterioration processes. The ADAMTS4-specific molecular magnetic resonance (MR) probe showed potential to predict abdominal aortic aneurysm (AAA) formation and rupture in a murine model. Wall biomarkers assessed using dynamic contrast-enhanced (DCE) MRI showed great potential for assessing AAA progression independent of the maximum diameter.

CONCLUSION

This scoping review provides an overview of quantitative MRI techniques studied and the biomarkers derived from them to assess aortic aneurysm progression and rupture risk. Longitudinal studies are needed to validate the causal relationships between the identified biomarkers and aneurysm growth, rupture, or repair. In the future, quantitative MRI could play an important role in the personalized risk assessment of aortic aneurysm rupture.

CLINICAL IMPACT

The currently used maximum aneurysm diameter fails to accurately assess the multifactorial pathology of an aortic aneurysm and precisely predicts rupture in a patient-specific manner. Quantitative magnetic resonance imaging (MRI) enables the detection of various quantitative parameters involved in aneurysm progression and subsequent rupture. This scoping review provides an overview of the studied quantitative MRI techniques, the biomarkers derived from them, and recommendations for future research needed for the implementation of these biomarkers. Ultimately, quantitative MRI could facilitate personalized risk assessment for patients with aortic aneurysms, thereby reducing untimely repairs and improving rupture prevention.

Circulating biomarkers of cardiovascular disease are related to aneurysm volume in abdominal aortic aneurysm

BACKGROUND

Surveillance programs in abdominal aortic aneurysms (AAA) are mainly based on imaging and leave room for improvement to timely identify patients at risk for AAA growth. Many biomarkers are dysregulated in patients with AAA, which fuels interest in biomarkers as indicators of disease progression. We examined associations of 92 cardiovascular disease (CVD)-related circulating biomarkers with AAA and sac volume.

METHODS

In a cross-sectional analysis, we separately investigated (1) 110 watchful waiting (WW) patients (undergoing periodic surveillance imaging without planned intervention) and (2) 203 patients after endovascular aneurysm repair (EVAR). The Cardiovascular Panel III (Olink Proteomics AB, Sweden) was used to measure 92 CVD-related circulating biomarkers. We used cluster analyses to investigate protein-based subphenotypes, and linear regression to examine associations of biomarkers with AAA and sac volume on CT scans.

RESULTS

Cluster analyses revealed two biomarker-based subgroups in both WW and EVAR patients, with higher levels of 76 and 74 proteins, respectively, in one subgroup versus the other. In WW patients, uPA showed a borderline significant association with AAA volume. Adjusting for clinical characteristics, there was a difference of -0.092 (-0.148, -0.036) loge mL in AAA volume per SD uPA. In EVAR patients, after multivariable adjustment, four biomarkers remained significantly associated with sac volume. The mean effects on sac volume per SD difference were: LDLR: -0.128 (-0.212, -0.044), TFPI: 0.139 (0.049, 0.229), TIMP4: 0.110 (0.023, 0.197), IGFBP-2: 0.103 (0.012, 0.194).

CONCLUSION

LDLR, TFPI, TIMP4, and IGFBP-2 were independently associated with sac volume after EVAR. Subgroups of patients with high levels of the majority of CVD-related biomarkers emphasize the intertwined relationship between AAA and CVD.ClinicalTrials.gov Identifier: NCT03703947.

Binding of Pentagalloyl Glucose to Aortic Wall Proteins: Insights from Peptide Mapping and Simulated Docking Studies

Pentagalloyl glucose (PGG) is currently being investigated as a non-surgical treatment for abdominal aortic aneurysms (AAAs); however, the molecular mechanisms of action of PGG on the AAA matrix components and the intra-luminal thrombus (ILT) still need to be better understood. To assess these interactions, we utilized peptide fingerprinting and molecular docking simulations to predict the binding of PGG to vascular proteins in normal and aneurysmal aorta, including matrix metalloproteinases (MMPs), cytokines, and fibrin. We performed PGG diffusion studies in pure fibrin gels and human ILT samples. PGG was predicted to bind with high affinity to most vascular proteins, the active sites of MMPs, and several cytokines known to be present in AAAs. Finally, despite potential binding to fibrin, PGG was shown to diffuse readily through thrombus at physiologic pressures. In conclusion, PGG can bind to all the normal and aneurysmal aorta protein components with high affinity, potentially protecting the tissue from degradation and exerting anti-inflammatory activities. Diffusion studies showed that thrombus presence in AAAs is not a barrier to endovascular treatment. Together, these results provide a deeper understanding of the clinical potential of PGG as a non-surgical treatment of AAAs.

Redox Dysregulation of Vascular Smooth Muscle Sirtuin-1 in Thoracic Aortic Aneurysm in Marfan Syndrome

BACKGROUND

Thoracic aortic aneurysms (TAAs) are abnormal aortic dilatations and a major cardiovascular complication of Marfan syndrome. We previously demonstrated a critical role for vascular smooth muscle (VSM) SirT1 (sirtuin-1), a lysine deacetylase, against maladaptive aortic remodeling associated with chronic oxidative stress and aberrant activation of MMPs (matrix metalloproteinases).

METHODS

In this study, we investigated whether redox dysregulation of SirT1 contributed to the pathogenesis of TAA using fibrillin-1 hypomorphic mice (Fbn1mgR/mgR), an established model of Marfan syndrome prone to aortic dissection/rupture.

RESULTS

Oxidative stress markers 3-nitrotyrosine and 4-hydroxynonenal were significantly elevated in aortas of patients with Marfan syndrome. Moreover, reversible oxidative post-translational modifications (rOPTM) of protein cysteines, particularly S-glutathionylation, were dramatically increased in aortas of Fbn1mgR/mgR mice, before induction of severe oxidative stress markers. Fbn1mgR/mgR aortas and VSM cells exhibited an increase in rOPTM of SirT1, coinciding with the upregulation of acetylated proteins, an index of decreased SirT1 activity, and increased MMP2/9 activity. Mechanistically, we demonstrated that TGFβ (transforming growth factor beta), which was increased in Fbn1mgR/mgR aortas, stimulated rOPTM of SirT1, decreasing its deacetylase activity in VSM cells. VSM cell-specific deletion of SirT1 in Fbn1mgR/mgR mice (SMKO-Fbn1mgR/mgR) caused a dramatic increase in aortic MMP2 expression and worsened TAA progression, leading to aortic rupture in 50% of SMKO-Fbn1mgR/mgR mice, compared with 25% of Fbn1mgR/mgR mice. rOPTM of SirT1, rOPTM-mediated inhibition of SirT1 activity, and increased MMP2/9 activity were all exacerbated by the deletion of Glrx (glutaredoxin-1), a specific deglutathionylation enzyme, while being corrected by overexpression of Glrx or of an oxidation-resistant SirT1 mutant in VSM cells.

CONCLUSIONS

Our novel findings strongly suggest a causal role of S-glutathionylation of SirT1 in the pathogenesis of TAA. Prevention or reversal of SirT1 rOPTM may be a novel therapeutic strategy to prevent TAA and TAA dissection/ruptures in individuals with Marfan syndrome, for which, thus far, no targeted therapy has been developed.

Residual Aneurysmal Sac Shrinkage Post-Endovascular Aneurysm Repair: The Role of Preoperative Inflammatory Markers

INTRODUCTION

In this study, we evaluated the role of preoperative inflammatory markers as Neutrophil-to-Lymphocyte (NLR) and Platelet-to-Lymphocyte (PLR) ratios in relation to post-endovascular aneurysm repair (EVAR) sac shrinkage, which is known to be an important factor for abdominal aortic aneurysm (AAA) healing.

METHODS

This was a single-center retrospective observational study. All patients who underwent the EVAR procedure from January 2017 to December 2020 were eligible for this study. Pre-operative blood samples of all patients admitted were used to calculate NLR and PLR. Sac shrinkage was defined as a decrease of ≥5 mm in the maximal sac diameter. The optimal NLR and PLR cut-offs for aneurysmal sac shrinkage were obtained from ROC curves. Stepwise multivariate analysis was performed in order to identify independent risk and protective factors for the absence of AAA shrinkage. Kaplan-Meier curves were used to evaluate survival rates with respect to the AAA shrinkage.

RESULTS

A total of 184 patients were finally enrolled. The mean age was 75.8 ± 8.3 years, and 85.9% were male (158/184). At a mean follow-up of 43 ± 18 months, sac shrinkage was registered in 107 patients (58.1%). No-shrinking AAA patients were more likely to be older, to have a higher level of NLR and PLR, and be an active smoker. Kaplan-Meier curves highlighted a higher rate of survival for shrinking AAA patients with respect to their counterparts (p < 0.03). Multivariate analysis outlined active smoking and NLR as independent risk factors for no-shrinking AAA.

CONCLUSIONS

Inflammation emerged as a possible causative factor for no-shrinking AAA, playing a role in aneurysmal sac remodeling. This study revealed that inflammatory biomarkers, such as NLR and PLR, can be used as a preoperative index of AAA sac behavior after EVAR procedures.

Immune-dysregulated neutrophils characterized by upregulation of CXCL1 may be a potential factor in the pathogenesis of abdominal aortic aneurysm and systemic lupus erythematosus

Background

The abdominal aortic aneurysm (AAA) incidence is closely related to systemic lupus erythematosus (SLE). However, the common mechanisms between AAA and SLE are still unknown. The purpose of this research was to examine the main molecules and pathways involved in the immunization process that lead to the co-occurrence of AAA and SLE through the utilization of quantitative bioinformatics analysis of publicly available RNA sequencing databases. Moreover, routine blood test information was gathered from 460 patients to validate the findings.

Materials and methods

Datasets of both AAA (GSE57691 and GSE205071) and SLE (GSE50772 and GSE154851) were downloaded from the Gene Expression Omnibus (GEO) database, and differentially expressed genes (DEGs) were analyzed using bioinformatic tools. To determine the functions of the common differentially expressed genes (DEGs), Gene Ontology (GO) and Kyoto Encyclopedia analyses were conducted. Subsequently, the hub gene was identified through cytoHubba, and its validation was carried out in GSE47472 for AAA and GSE81622 for SLE. Immune cell infiltration analysis was performed to identify the key immune cells correlated with AAA and SLE, and to evaluate the correlation between key immune cells and the hub gene. Subsequently, the routine blood test data of 460 patients were collected, and the result of the immune cell infiltration analysis was further validated by univariate and multivariate logistic regression analysis.

Results

A total of 25 common DEGs were obtained, and three genes were screened by cytoHubba algorithms. Upon validation of the datasets, CXCL1 emerged as the hub gene with strong predictive capabilities, as evidenced by an area under the curve (AUC) > 0.7 for both AAA and SLE. The infiltration of immune cells was also validated, revealing a significant upregulation of neutrophils in the AAA and SLE datasets, along with a correlation between neutrophil infiltration and CXCL1 upregulation. Clinical data analysis revealed a significant increase in neutrophils in both AAA and SLE patients (p < 0.05). Neutrophils were found to be an independent factor in the diagnosis of AAA and SLE, exhibiting good diagnostic accuracy with AUC >0.7.

Conclusion

This study elucidates CXCL1 as a hub gene for the co-occurrence of AAA and SLE. Neutrophil infiltration plays a central role in the development of AAA and SLE and may serve to be a potential diagnostic and therapeutic target.

Serum levels of Matrix Metalloproteinases (MMPs) in patients undergoing endovascular intervention for peripheral arterial disease

OBJECTIVES

Matrix metalloproteinases (MMPs) play a significant role in the development and progression of atherosclerotic vascular disease. The purpose of this study was to measure and document the profile of plasma circulating MMPs in patients with peripheral arterial disease (PAD) undergoing endovascular revascularization.

METHODS

This was a single centre prospective observational study with 80 patients with PAD enrolled. They underwent percutaneous balloon angioplasty and/or angioplasty with stent. Exclusion criteria were acute limb ischemia, active inflammation, wet gangrene, liver disease, end stage renal failure and cancer. Patients that underwent open or hybrid (open and endovascular) approach, were also excluded from the study. Venous blood samples were taken preoperatively, 24 hours and 6 months postoperatively. The values of MMP-2, MMP-3, MMP-7, MMP-9 and their inhibitors (Tissue Inhibitor of metalloproteinases, TIMP), TIMP-1 and TIMP-2 were measured.

RESULTS

The mean age was 67.1 years and 66 of them (82.5%) were male. During the clinical follow up (mean 35.8% months), 12 patients died (16.4%), 15 (20.5%) of them had a major adverse limb event (MALE) and 14 (19.2%) of them had a major adverse cardiovascular event (MACE). There was a statistically significant raise in the values of MMP-2. MMP-3 and MMP-7 at 6 months postoperatively, when compared to the preoperative and 24 hours postoperative values. There was no correlation of MMP and TIMP values with mortality, MALE and MACE events.

CONCLUSIONS

The present single-centre prospective study documented increased circulating levels of MMPs post-operatively in PAD patients undergoing endovascular treatment. Vascular trauma caused by angioplasty, could trigger expression of MMPs and TIMPs, but the absence of any association with clinical complications requires further investigation.

Single-cell transcriptome analysis identifies Versican(+) myofibroblast as a hallmark for thoracic aortic aneurysm marked by activation of PI3K-AKT signaling pathway

BACKGROUND

Thoracic aortic aneurysm (TAA) is a silent but dangerous cardiovascular disease. Understanding molecular mechanisms of TAA on single-cell level might provide new strategies for preventing and treating TAA.

METHODS

Single-cell RNA sequencing was performed on control and aneurysmal thoracic aorta to find out specific cell clusters and cell types. Western blot and histological staining were used to verify the findings of single-cell transcriptome analysis. Characteristics of Versican (VCAN) overexpressed myofibroblast was evaluated through bioinformatic methods and experimental validation.

RESULTS

A total of 3 control and 8 TAA specimens were used for single-cell transcriptome analysis including 48,128 thoracic aortic cells. Among these cells, we found out a specific cell cluster containing both hallmarks of smooth muscle cell (SMC) and fibroblast. Thus, we defined these cells as myofibroblast. Further single-cell transcriptome analysis identified VCAN as a cellular marker of myofibroblast. Western blot and histological staining revealed that VCAN(+) myofibroblast was significantly increased in TAA specimens compared with control individuals. Differential analysis, functional, pathway enrichment analysis and cell-cell communication analysis demonstrated that VCAN(+) myofibroblast was closely associated with previous reported TAA associated pathological process including SMC proliferation, SMC migration and extracellular matrix (ECM) disruption. Pathway analysis found out significant activation of PI3K-AKT signaling pathway within VCAN(+) myofibroblast, which was further confirmed by experimental validation.

CONCLUSIONS

Single-cell RNA sequencing identified VCAN(+) myofibroblast as a typical cellular hallmark of TAA. These cells might participate in the pathogenesis of TAA through activation of PI3K-AKT signaling pathway to link SMC proliferation, SMC migration and ECM disruption.

TCF7L1 Accelerates Smooth Muscle Cell Phenotypic Switching and Aggravates Abdominal Aortic Aneurysms

Phenotypic switching of vascular smooth muscle cells is a central process in abdominal aortic aneurysm (AAA) pathology. We found that knockdown TCF7L1 (transcription factor 7-like 1), a member of the TCF/LEF (T cell factor/lymphoid enhancer factor) family of transcription factors, inhibits vascular smooth muscle cell differentiation. This study hints at potential interventions to maintain a normal, differentiated smooth muscle cell state, thereby eliminating the pathogenesis of AAA. In addition, our study provides insights into the potential use of TCF7L1 as a biomarker for AAA.

Bioinformatics-based identification of lipid- and immune-related biomarkers in abdominal aortic aneurysms

Background

Abdominal aortic aneurysm (AAA) manifest as a natural inflammatory process with permanent dilation and terminal rupture. Nevertheless, the pathogenesis of AAA remains a mystery, and treatment is still controversial. Lipid metabolism and immune system are involved in AAA progression, which has been well documented. However, lipid- and immune-related (LIR) biomarkers need to be further elucidated.

Methods

The AAA-related datasets were retrieved from the GEO database, and the datasets were analyzed for differential gene expression by NetworkAnalyst. GO and KEGG pathway enrichment analysis of differentially expressed mRNA (DE-mRNA) was performed using Metscape, and LIR DE-mRNA was further screened. AAA rat model was constructed using porcine pancreatic elastase to verify the differential expression of LIR DE-mRNA.

Results

The GSE47472 and GSE57691 datasets respectively identified 614 (containing 381 down-regulated and 233 up-regulated DE-mRNAs) and 384 (containing 218 down-regulated and 164 up-regulated DE-mRNAs) DE-mRNAs. Intersection and union of DE-mRNAs were 13 and 983, respectively. The main terms involved in the union of DE-mRNAs included "immune system process", "metabolic process", "Chemokine signaling pathway", "hematopoietic cell lineage" and "Cholesterol metabolism". In vivo experiments revealed that LIR DE-mRNAs of PDIA3, TYROBP, and HSPA1A were significantly low expression in AAA abdominal aortic tissues, and HCK and SERPINE1 were significantly high expression, which is consistent with the bioinformatics analysis.

Conclusions

PDIA3, TYROBP, HSPA1A, HCK and SERPINE1 may serve as LIR biomarkers of AAA, which provides new insights and theoretical guidance for the future treatment, early prevention and progression of AAA.

Loss of myeloid Tsc2 predisposes to angiotensin II-induced aortic aneurysm formation in mice

RATIONALE

Genetic studies have proved the involvement of Tuberous sclerosis complex subunit 2 (Tsc2) in aortic aneurysm. However, the exact role of macrophage Tsc2 in the vascular system remains unclear. Here, we examined the potential function of macrophage Tsc2 in the development of aortic remodeling and aortic aneurysms.

METHODS AND RESULTS

Conditional gene knockout strategy combined with histology and whole-transcriptomic analysis showed that Tsc2 deficiency in macrophages aggravated the progression of aortic aneurysms along with an upregulation of proinflammatory cytokines and matrix metallopeptidase-9 in the angiotensin II-induced mouse model. G protein-coupled receptor 68 (Gpr68), a proton-sensing receptor for detecting the extracellular acidic pH, was identified as the most up-regulated gene in Tsc2 deficient macrophages compared with control macrophages. Additionally, Tsc2 deficient macrophages displayed higher glycolysis and glycolytic inhibitor 2-deoxy-D-glucose treatment partially attenuated the level of Gpr68. We further demonstrated an Tsc2-Gpr68-CREB network in macrophages that regulates the inflammatory response, proteolytic degradation and vascular homeostasis. Gpr68 inhibition largely abrogated the progression of aortic aneurysms caused by Tsc2 deficiency in macrophages.

CONCLUSIONS

The findings reveal that Tsc2 deficiency in macrophages contributes to aortic aneurysm formation, at least in part, by upregulating Gpr68 expression, which subsequently drives proinflammatory processes and matrix metallopeptidase activation. The data also provide a novel therapeutic strategy to limit the progression of the aneurysm resulting from Tsc2 mutations.

Pathophysiological Role of Chymase-Activated Matrix Metalloproteinase-9

Chymase present in mast cells can directly form matrix metalloproteinase (MMP)-9 from proMMP-9. Chymase-activated MMP-9 has been reportedly closely related to the pathogenesis of various diseases, and inflammation-related diseases in particular. Upregulated chymase and MMP-9 have been observed in tissues from patients and animal models of aortic aneurysm, inflammatory gastrointestinal and hepatic diseases, acute pancreatic failure, atopic dermatitis and rheumatoid arthritis. Chymase at these regions is only derived from mast cells, while MMP-9 is derived from macrophages and neutrophils in addition to mast cells. Chymase inhibitors attenuate MMP-9 formation from pro-MMP-9, and ameliorate the development and progression of these disorders, along with reduction in inflammatory cell numbers. MMP-9 activated by chymase might also be involved in angiogenesis in the tumor environment. Development of angiogenesis around several cancers is closely related to the expression of chymase and MMP-9, and postoperative survival curves have revealed that patients with a higher number of chymase positive cells have lower survival rates. In this review, we wanted to clarify the role of chymase-activated MMP-9, which might become an important therapeutic target for various inflammatory disorders.

The Nonproteolytic Intracellular Domain of Membrane-Type 1 Matrix Metalloproteinase Coordinately Modulates Abdominal Aortic Aneurysm and Atherosclerosis in Mice-Brief Report

BACKGROUND

MT1-MMP (membrane-type 1 matrix metalloproteinase, MMP-14) is a transmembrane-anchored protein with an extracellular proteinase domain and a cytoplasmic tail devoid of proteolytic functions but capable of mediating intracellular signaling that regulates tissue homeostasis. MT1-MMP extracellular proteolytic activity has been shown to regulate pathological remodeling in aortic aneurysm and atherosclerosis. However, the role of the nonproteolytic intracellular domain of MT1-MMP in vascular remodeling in abdominal aortic aneurysms (AAA) is unknown.

METHODS

We generated a mutant mouse that harbors a point mutation (Y573D) in the MT1-MMP cytoplasmic domain that abrogates the MT1-MMP signaling function without affecting its proteolytic activity. These mice and their control wild-type littermates were subjected to experimental AAA modeled by angiotensin II infusion combined with PCSK9 (proprotein convertase subtilisin/kexin type 9) overexpression and high-cholesterol feeding.

RESULTS

The mutant mice developed more severe AAA than the control mice, with concomitant generation of intraaneurysmal atherosclerotic lesions and dramatically increased macrophage infiltration and elastin degradation. Aortic lesion-associated and bone marrow-derived macrophages from the mutant mice exhibited an enhanced inflammatory state and expressed elevated levels of proinflammatory Netrin-1, a protein previously demonstrated to promote both atherosclerosis and AAA.

CONCLUSIONS

Our findings show that the cytoplasmic domain of MT1-MMP safeguards from AAA and atherosclerotic plaque development through a proteolysis-independent signaling mechanism associated with Netrin-1 expression. This unexpected function of MT1-MMP unveils a novel mechanism of synchronous onset of AAA and atherogenesis and highlights its importance in the control of vascular wall homeostasis.

Elastin turnover in ocular diseases: A special focus on age-related macular degeneration

The extracellular matrix (ECM) and its turnover play a crucial role in the pathogenesis of several inflammatory diseases, including age-related macular degeneration (AMD). Elastin, a critical protein component of the ECM, not only provides structural and mechanical support to tissues, but also mediates several intracellular and extracellular molecular signaling pathways. Abnormal turnover of elastin has pathological implications. In the eye elastin is a major structural component of Bruch's membrane (BrM), a critical ECM structure separating the retinal pigment epithelium (RPE) from the choriocapillaris. Reduced integrity of macular BrM elastin, increased serum levels of elastin-derived peptides (EDPs), and elevated elastin antibodies have been reported in AMD. Existing reports suggest that elastases, the elastin-degrading enzymes secreted by RPE, infiltrating macrophages or neutrophils could be involved in BrM elastin degradation, thus contributing to AMD pathogenesis. EDPs derived from elastin degradation can increase inflammatory and angiogenic responses in tissues, and the elastin antibodies are shown to play roles in immune cell activity and complement activation. This review summarizes our current understanding on the elastases/elastin fragments-mediated mechanisms of AMD pathogenesis.

Selective Inhibitors of Medium-Size S1' Pocket Matrix Metalloproteinases: A Stepping Stone of Future Drug Discovery

Among various matrix metalloproteinases (MMPs), MMPs having medium-size S1' pockets are established as promising biomolecular targets for executing crucial roles in cancer, cardiovascular diseases, and neurodegenerative diseases. However, no such MMP inhibitors (MMPIs) are available to date as drug candidates despite a lot of continuous research work for more than three decades. Due to a high degree of structural resemblance among these MMPs, designing selective MMPIs is quite challenging. However, the variability and uniqueness of the S1' pockets of these MMPs make them promising targets for designing selective MMPIs. In this perspective, the overall structural aspects of medium-size S1' pocket MMPs including the unique binding patterns of enzyme-inhibitor interactions have been discussed in detail to acquire knowledge regarding selective inhibitor designing. This overall knowledge will surely be a curtain raiser for the designing of selective MMPIs as drug candidates in the future.

Platelet TGF-β1 inhibits the migration and proliferation of smooth muscle cells in aneurysms

BACKGROUND

The study explored the role of platelet TGF-β1 from the perspective of inhibiting the excessive proliferation, migration and invasion of murine aortic vascular smooth muscle cells (MASMCs).

METHOD

The platelets were first extracted from C57BL/6 mice, and the TGF-β1 protein was obtained after the purification of protein. In vitro, the concentrations of angiotensin Ⅱ (Ang Ⅱ) and TGF-β1 for intervention were screened by testing the viability of MASMCs, followed by the analysis concerning the effects of platelets, Ang Ⅱ and TGF-β1 on the proliferation, migration, invasion, and the expressions of pathway-related proteins in MASMCs. In vivo, an Ang Ⅱ-induced mouse model was established. TGF-β1 was injected into the tail of mice as a therapeutic agent, and its action mechanism was further verified by the treatment of inhibitor SB505124. The results of the cell experiment were validated by evaluating the maximum diameter of abdominal aorta, the proportion of total weight, the changes of both pathology and the expressions of pathway-related proteins in the mice.

RESULT

0.5 ng/mL Ang Ⅱ and 15 ng/mL TGF-β1 were chosen for treatment. The following results of cell functional experiments and Western blot assay demonstrated that Ang Ⅱ promoted the proliferation, migration and invasion of MASMCs via regulating related pathways, the effects of which were evidently reversed by TGF-β1 and platelets. Consistent results were also observed in the animal experiments, where TGF-β1 effectively alleviated Ang Ⅱ-induced abdominal aortic injury in mice.

CONCLUSION

TGF-β1 in platelets inhibits Ang Ⅱ-induced proliferation, migration and invasion of MASMCs.

Pemafibrate Prevents Rupture of Angiotensin II-Induced Abdominal Aortic Aneurysms

Background

Abdominal aortic aneurysm (AAA) is a life-threatening disease that lacks effective preventive therapies. This study aimed to evaluate the effect of pemafibrate, a selective peroxisome proliferator-activated receptor alpha (PPARα) agonist, on AAA formation and rupture.

Methods

Experimental AAA was induced by subcutaneous angiotensin II (AngII) infusion in ApoE ^{- / -} mice for 4 weeks. Pemafibrate (0.1 mg/kg/day) was administered orally. Dihydroethidium staining was used to evaluate the reactive oxygen species (ROS).

Results

The size of the AngII-induced AAA did not differ between pemafibrate- and vehicle-treated groups. However, a decreased mortality rate due to AAA rupture was observed in pemafibrate-treated mice. Pemafibrate ameliorated AngII-induced ROS and reduced the mRNA expression of interleukin-6 and tumor necrosis factor-α in the aortic wall. Gelatin zymography analysis demonstrated significant inhibition of matrix metalloproteinase-2 activity by pemafibrate. AngII-induced ROS production in human vascular smooth muscle cells was inhibited by pre-treatment with pemafibrate and was accompanied by an increase in catalase activity. Small interfering RNA-mediated knockdown of catalase or PPARα significantly attenuated the anti-oxidative effect of pemafibrate.

Conclusion

Pemafibrate prevented AAA rupture in a murine model, concomitant with reduced ROS, inflammation, and extracellular matrix degradation in the aortic wall. The protective effect against AAA rupture was partly mediated by the anti-oxidative effect of catalase induced by pemafibrate in the smooth muscle cells.

Deficiency of cystathionine gamma-lyase promotes aortic elastolysis and medial degeneration in aged mice

Enzymatic degradation of elastin by matrix metalloproteinases (MMPs) leads to the permanent dilation of aortic wall and constitutes the most prominent characters of aortic aneurysm and aging-related medial degeneration. Hydrogen sulfide (H₂S) as a gasotransmitter exhibits a wide variety of cardio-protective functions through its anti-inflammatory and anti-oxidative actions. Cystathionine gamma-lyase (CSE) is a main H₂S-generating enzyme in cardiovascular system. The regulatory roles of CSE/H₂S system on elastin homeostasis and blood vessel degeneration have not yet been explored. Here we found that aged CSE knockout mice had severe aortic dilation and elastic degradation in abdominal aorta and were more sensitive to angiotensin II-induced aortic elastolysis and medial degeneration. Administration of NaHS would protect the mice from angiotensin II-induced inflammation, gelatinolytic activity, elastin fragmentation, and aortic dilation. In addition, human aortic aneurysm samples had higher inflammatory infiltration and lower expression of CSE. In cultured smooth muscle cells (SMCs), TNFα-induced MMP2/9 hyperactivity and elastolysis could be attenuated by exogenously applied NaHS or CSE overexpression while further deteriorated by complete knockout of CSE. It was further found that H₂S inhibited MMP2 transcription by posttranslational modification of Sp1 via S-sulfhydration. H₂S also directly suppressed MMP hyperactivity by S-sulfhydrating the cysteine switch motif. Taken together, this study revealed the involvement of CSE/H₂S system in the pathogenesis of aortic elastolysis and medial degeneration by maintaining the inactive form of MMPs, suggesting that CSE/H₂S system can be a target for the prevention of age-related medial degeneration and treatment of aortic aneurysm.

Akkermansia muciniphila Alters Gut Microbiota and Immune System to Improve Cardiovascular Diseases in Murine Model

The gut microbiota plays an important role in a variety of cardiovascular diseases. The probiotics screened based on microbiota can effectively improve metabolism and immune function of the body, which is of great value in the field of cardiovascular disease treatment. Abdominal aortic aneurysms (AAA) refer to the lesion or injury of the abdominal aortic wall resulting in a localized bulge, which is one of the cardiovascular diseases with pulsing mass as the main clinical symptom. Previous studies have confirmed that A. muciniphila was depleted in the guts of AAA patients or mice. A. muciniphila is a potential probiotic for the treatment of intestinal microbiome-related diseases. Therefore, this study aims to investigate the effects of A. muciniphila on gut microbiota and disease-related biomarkers in AAA mice. C57BL/6J mice were used to construct the AAA model and treated with A. muciniphila. Aortic aneurysm formation in the AAA group is associated with the increased diameter of the abdominal aorta and inflammatory infiltration. A. muciniphila inhibited the formation of AAA and repaired tissue damage. The number of gut microbiota and α diversity index were decreased in the model group. A. muciniphila increased the number of gut microbiota and α diversity in AAA mice. The abundance of uncultured bacterium and Lactobacillus were increased, while the abundance of the Lachnospiraceae NK4A136 group was reduced in the AAA group. Compared with the control group, the levels of MMP-1, MMP-9, IL-33, CTSB, and CTSL in tissue and the levels of IL-6, IFN-γ, and CRP in blood were significantly increased, and the levels of IL-4, IL-10, and IL-17A in blood were significantly decreased in the AAA group. The intervention of A. muciniphila reversed these changes. The gut microbiota function prediction showed changes in E. coli, Clostridium, and Lactobacillus metabolism-related functional pathways. Akkermansia was negatively correlated with Helicobacter and Lactobacillus and positively correlated with Clostridium_sensu_stricto_1 and Escherichia shigella at the genus level. In conclusion, A. muciniphila inhibited the formation of AAA by restoring gut microbiota diversity, altering the expression of peripheral immune factors, and the functions of E. coli, Clostridium, and Lactobacillus, which may provide a new theoretical basis for the application of probiotics in cardiovascular diseases.

The Role of Obesity, Inflammation and Sphingolipids in the Development of an Abdominal Aortic Aneurysm

Abdominal aortic aneurysm (AAA) is a local dilatation of the vessel equal to or exceeding 3 cm. It is a disease with a long preclinical period commonly without any symptoms in its initial stage. Undiagnosed for years, aneurysm often leads to death due to vessel rupture. The basis of AAA pathogenesis is inflammation, which is often associated with the excess of adipose tissue, especially perivascular adipose tissue, which synthesizes adipocytokines that exert a significant influence on the formation of aneurysms. Pro-inflammatory cytokines such as resistin, leptin, and TNFα have been shown to induce changes leading to the formation of aneurysms, while adiponectin is the only known compound that is secreted by adipose tissue and limits the development of aneurysms. However, in obesity, adiponectin levels decline. Moreover, inflammation is associated with an increase in the amount of macrophages infiltrating adipose tissue, which are the source of matrix metalloproteinases (MMP) involved in the degradation of the extracellular matrix, which are an important factor in the formation of aneurysms. In addition, an excess of body fat is associated with altered sphingolipid metabolism. It has been shown that among sphingolipids, there are compounds that play an opposite role in the cell: ceramide is a pro-apoptotic compound that mediates the development of inflammation, while sphingosine-1-phosphate exerts pro-proliferative and anti-inflammatory effects. It has been shown that the increase in the level of ceramide is associated with a decrease in the concentration of adiponectin, an increase in the concentration of TNFα, MMP-9 and reactive oxygen species (which contribute to the apoptosis of vascular smooth muscle cell). The available data indicate a potential relationship between obesity, inflammation and disturbed sphingolipid metabolism with the formation of aneurysms; therefore, the aim of this study was to systematize the current knowledge on the role of these factors in the pathogenesis of abdominal aortic aneurysm.

Matrix metaloproteinases in vascular pathology

Vascular diseases are the main cause of morbidity and mortality. The vascular extracellular matrix (ECM) is essential in mechanical support, also regulating the cellular behavior fundamental to vascular function and homeostasis. Vascular remodeling is an adaptive response to various physiological and pathological changes and is associated with aging and vascular diseases. The aim of this review is provide a general overview of the involvement of MMPs in the pathogenesis of vascular diseases, namely, arterial hypertension, atherosclerosis, aortic aneurysms and myocardial infarction. The change in the composition of the ECM by matrix metalloproteinases (MMPs) generates a pro-inflammatory microenvironment that modifies the phenotypes of endothelial cells and vascular smooth muscle cells. They play a central role in morphogenesis, tissue repair and remodeling in response to injury, e.g., after myocardial infarction, and in progression of diseases such as atherosclerosis. Alterations in specific MMPs could influence arterial remodeling and lead to various pathological disorders such as hypertension and aneurysm formation. MMPs are regulated by endogenous tissue inhibitors of metalloproteinases (TIMPs), and the MMP/TIMP ratio generally determines the extent of ECM protein degradation and tissue remodeling. Studies are currently focused on improving the diagnostic and prognostic value of MMPs involved in the pathogenic process, increasing their therapeutic potential, and monitoring the disease. New selective MMP inhibitors may improve the specificity of these inhibitors, target specific MMPs in relevant pathological conditions and mitigate some of the side effects.

Association of TGF-β Canonical Signaling-Related Core Genes With Aortic Aneurysms and Aortic Dissections

Transforming growth factor-beta (TGF-β) signaling is essential for the maintenance of the normal structure and function of the aorta. It includes SMAD-dependent canonical pathways and noncanonical signaling pathways. Accumulated genetic evidence has shown that TGF-β canonical signaling-related genes have key roles in aortic aneurysms (AAs) and aortic dissections and many gene mutations have been identified in patients, such as those for transforming growth factor-beta receptor one TGFBR1, TGFBR2, SMAD2, SMAD3, SMAD4, and SMAD6. Aortic specimens from patients with these mutations often show paradoxically enhanced TGF-β signaling. Some hypotheses have been proposed and new AA models in mice have been constructed to reveal new mechanisms, but the role of TGF-β signaling in AAs is controversial. In this review, we focus mainly on the role of canonical signaling-related core genes in diseases of the aorta, as well as recent advances in gene-mutation detection, animal models, and in vitro studies.

Molecular Imaging of Aortic Aneurysm and Its Translational Power for Clinical Risk Assessment

Aortic aneurysms (AAs) are dilations of the aorta, that are often fatal upon rupture. Diagnostic radiological techniques such as ultrasound (US), magnetic resonance imaging (MRI), and computed tomography (CT) are currently used in clinical practice for early diagnosis as well as clinical follow-up for preemptive surgery of AA and prevention of rupture. However, the contemporary imaging-based risk prediction of aneurysm enlargement or life-threatening aneurysm-rupture remains limited as these are restricted to visual parameters which fail to provide a personalized risk assessment. Therefore, new insights into early diagnostic approaches to detect AA and therefore to prevent aneurysm-rupture are crucial. Multiple new techniques are developed to obtain a more accurate understanding of the biological processes and pathological alterations at a (micro)structural and molecular level of aortic degeneration. Advanced anatomical imaging combined with molecular imaging, such as molecular MRI, or positron emission tomography (PET)/CT provides novel diagnostic approaches for in vivo visualization of targeted biomarkers. This will aid in the understanding of aortic aneurysm disease pathogenesis and insight into the pathways involved, and will thus facilitate early diagnostic analysis of aneurysmal disease. In this study, we reviewed these molecular imaging modalities and their association with aneurysm growth and/or rupture risk and their limitations. Furthermore, we outline recent pre-clinical and clinical developments in molecular imaging of AA and provide future perspectives based on the advancements made within the field. Within the vastness of pre-clinical markers that have been studied in mice, molecular imaging targets such as elastin/collagen, albumin, matrix metalloproteinases and immune cells demonstrate promising results regarding rupture risk assessment within the pre-clinical setting. Subsequently, these markers hold potential as a future diagnosticum of clinical AA assessment. However currently, clinical translation of molecular imaging is still at the onset. Future human trials are required to assess the effectivity of potentially viable molecular markers with various imaging modalities for clinical rupture risk assessment.

Daxx ameliorates abdominal aortic aneurysm through inhibiting the TGF-β1-mediated PI3K/AKT/ID2 signaling pathway

Background

Abdominal aortic aneurysm (AAA) is a potentially life-threatening vascular abnormality, that, if ruptured, is almost universally fatal without repair, and is associated with up to 50% mortality even if repaired in hospital. To date, there is no drug therapy that has clinically proven benefit to reduce or prevent expansion of AAA. The aim of this study was to investigate whether Daxx could affect AAA through inhibiting the PI3K/AKT/ID2 signaling pathway mediated by transforming growth factor β-1 (TGFβ1).

Methods

The AAA model was constructed by injecting angiotensin Ⅱ (Ang-Ⅱ) into rats, and the Daxx lentivirus vector was constructed. Hematoxylin and eosin (HE) staining was used to detect the wall thickness of the abdominal aorta in rats. The gene and protein expressions in abdominal aortic tissues were detected utilizing western blot, immunohistochemistry (IHC) and fluorescence quantitative real-time polymerase chain reaction (qRT-PCR). Finally, the concentration of TGF-β1 in abdominal aortic tissue was determined by ELISA.

Results

The abdominal aortic wall thickness was decreased in the Daxx expression group (by HE staining), and Daxx overexpression markedly reduced the protein expression levels of MMP2 and MMP9. Proteins related to the PI3K/AKT/ID2 signaling pathway were highly enhanced in the aneurysm wall of rats, but were reduced following Daxx addition. Moreover, Daxx reduced the damage to elastin (by IHC), and the expression levels of α-SMA and SM22α were up-regulated by Daxx (by qRT-PCR). The concentration of TGF-β1 was correlated with the activation of the PI3K/AKT/ID2 signaling pathway (by ELISA), whereas AKT overexpression weakened the inhibitory effect of Daxx.

Conclusion

Daxx ameliorated several mechanisms that contributed to expansion of AAA suppressing the tissue concentration of TGF-β1, thereby inhibiting the activation of the PI3K/AKT/ID2 signaling pathway. This evidence might form the basis to develop a therapeutic target for AAA.

Artificial Intelligence Uncovers Natural MMP Inhibitor Crocin as a Potential Treatment of Thoracic Aortic Aneurysm and Dissection

Thoracic aortic aneurysm and dissection (TAAD) is a lethal cardiovascular condition without effective pharmaceutical therapy. Identifying novel drugs that target the key pathogenetic components is an urgent need. Bioinformatics analysis of pathological studies indicated “extracellular matrix organization” as the most significant functional pathway related to TAAD, in which matrix metallopeptidase (MMP) 2 and MMP9 ranked above other proteases. MMP1-14 were designated as the prototype molecules for docking against PubChem Compound Database using Surflex-Dock, and nine natural compounds were identified. Using a generic MMP activity assay and an aminopropionitrile (BAPN)-induced TAAD mouse model, we identified crocin as an effective MMP inhibitor, suppressing the occurrence and rupture of TAAD. Biolayer interferometry and AI/bioinformatics analyses indicated that crocin may inhibit MMP2 activity by direct binding. Possible binding sites were investigated. Overall, the integration of artificial intelligence and functional experiments identified crocin as an MMP inhibitor with strong therapeutic potential.

Thrombospondins in human aortic aneurysms

Thrombospondins are a family of matricellular proteins with a multimeric structure that is known to be involved in several biological and pathological processes. Their relationship with vascular disorders has raised special interest recently. Aortic aneurysms are related to the impairment of vascular remodeling, in which extracellular matrix proteins seem to play an important role. Thus, research in thrombospondins, and their potential role in aneurysm development is progressively gaining importance. Nevertheless, studies showing thrombospondin dysregulation in human samples are still scarce. Although studies performed in vitro and in vivo models are essential to understand the molecular mechanisms and pathways underlying the disorder, descriptive studies in human samples are also necessary to ascertain their real value as biomarkers and/or novel therapeutic targets. The present article reviews the latest findings regarding the role of thrombospondins in aortic aneurysm development, paying particular attention to the studies performed in human samples.

Role and interaction between ACE1, ACE2 and their related genes in cardiovascular disorders

Cardiovascular disease is the greatest health care burden and one of the most common causes of death worldwide. Less is known about the genetic factors that are responsible for predisposition to cardiovascular disease thus; the molecular and genetic mechanisms underlying cardiovascular diseases remain obscure. One important regulator of blood pressure homeostasis is the renin-angiotensin system (RAS). The protease renin cleaves angiotensinogen into the inactive decameric peptide angiotensin I (AngI). Angiotensin-converting enzyme (ACE) catalyzes the cleavage of the Ang I into the active octomer angiotensin II (Ang II). In humans, can ACE polymorphism has been associated with determinants of renal and cardiovascular function and pharmacological inhibition of ACE and Ang II receptors are effective in lowering blood pressure and preventing kidney disease. In addition, inhibition of ACE and Ang II receptors has beneficial effects in heart failure. A homologue of ACE, termed ACE2, has been identified; it is predominantly expressed in the vascular endothelial cells of the kidney and heart. Unlike ACE, ACE2 functions as a carboxypeptidase, cleaving a single residue from AngI, generating Ang1-9, and a single residue from AngII to generate Ang1-7. Nevertheless, the in vivo role of ACE2 in the cardiovascular system and the RAS is not known.

Association of IL-10 and CRP with Pulse Wave Velocity in Patients with Abdominal Aortic Aneurysm

Background: Markers of inflammation and arterial stiffness are predictors of cardiovascular morbidity and events, but their roles in the mechanisms and progression of abdominal aortic aneurysm (AAA) in males have not been fully investigated. This study explored possible associations between inflammatory marker levels and arterial stiffness in males with AAA. Methods: A total of 270 males (191 AAA and 79 controls) were included in the study. Arterial stiffness was assessed using non-invasive applanation tonometry to measure the regional pulse wave velocity between the carotid and femoral arteries and the carotid and radial arteries. Blood samples were obtained, and interleukin-10 (IL-10) and CRP levels were analysed. Results: Subjects with an AAA had higher levels of IL-10 (21.5 ± 14.0 ng/mL versus 16.6 ± 9.3 ng/mL) compared to controls (p = 0.007). In the AAA cohort, subjects with T2DM showed higher levels of IL-10 (26.4 ± 17.3 versus 20.4 ± 13.0, p = 0.036). We observed a positive correlation between PWVcf and CRP in the control group (r = 0.332) but not the AAA group. PWVcf and CRP were negatively correlated (r = 0.571) in the T2DM subjects treated with metformin in the AAA group. Conclusion: Arterial stiffness is related to the degree of inflammation reflected by CRP and IL-10 levels in males with an AAA. IL-10 is negatively correlated with arterial stiffness in these subjects. This finding suggests that IL-10 may decrease arterial stiffness in males with AAA. The negative correlation between CRP and PWVcf in males with T2DM treated with metformin may indicate that metformin influences the arterial wall to decrease stiffness in subjects with AAA.

Cycloastragenol Inhibits Experimental Abdominal Aortic Aneurysm Progression

The pathogenesis of abdominal aortic aneurysm involves vascular inflammation and elastin degradation. Astragalusradix contains cycloastragenol, which is known to be anti-inflammatory and to protect against elastin degradation. We hypothesized that cycloastragenol supplementation inhibits abdominal aortic aneurysm progression. Abdominal aortic aneurysm was induced in male rats by intraluminal elastase infusion in the infrarenal aorta and treated daily with cycloastragenol (125 mg/kg/day). Aortic expansion was followed weekly by ultrasound for 28 days. Changes in aneurysmal wall composition were analyzed by mRNA levels, histology, zymography and explorative proteomic analyses. At day 28, mean aneurysm diameter was 37% lower in the cycloastragenol group (p < 0.0001). In aneurysm cross sections, elastin content was insignificantly higher in the cycloastragenol group (10.5% ± 5.9% vs. 19.9% ± 16.8%, p = 0.20), with more preserved elastin lamellae structures (p = 0.0003) and without microcalcifications. Aneurysmal matrix metalloprotease-2 activity was reduced by the treatment (p = 0.022). Messenger RNA levels of inflammatory- and anti-oxidative markers did not differ between groups. Explorative proteomic analysis showed no difference in protein levels when adjusting for multiple testing. Among proteins displaying nominal regulation were fibulin-5 (p = 0.02), aquaporin-1 (p = 0.02) and prostacyclin synthase (p = 0.007). Cycloastragenol inhibits experimental abdominal aortic aneurysm progression. The suggested underlying mechanisms involve decreased matrix metalloprotease-2 activity and preservation of elastin and reduced calcification, thus, cycloastragenol could be considered for trial in abdominal aortic aneurysm patients.

Dapagliflozin Ameliorates the Formation and Progression of Experimental Abdominal Aortic Aneurysms by Reducing Aortic Inflammation in Mice

Background. Dapagliflozin, a sodium glucose transporter protein-2 (SGLT-2) inhibitor, reduces the risk for cardiovascular diseases. However, the influence of dapagliflozin on nondissecting abdominal aortic aneurysms (AAAs) remains unclear. Methods. AAAs were created in male C57BL/6 mice via intra-aortic porcine pancreatic elastase (PPE) infusion. Mice were daily treated with dapagliflozin (1 or 5 mg/kg body weight) or an equal volume of vehicle through oral gavage beginning one day prior to PPE infusion for 14 days. To investigate its translational value, dapagliflozin or vehicle was also administered to mice with existing AAAs in another cohort. Aortic diameters were measured prior to (day 0 for baseline) and 14 days after PPE infusion. After sacrifice, mice aortae were collected, and following histological analyses were performed. Results. Dapagliflozin treatment significantly reduced aneurysmal aortic expansion following PPE infusion as compared to vehicle treatment especially at 5 mg/kg body weight (approximately 21% and 33% decreases in 1 and 5 mg/kg treatment groups, respectively). The dose-dependent attenuation of AAAs by dapagliflozin was also confirmed on histological analyses. Dapagliflozin remarkably reduced aortic accumulation of macrophages, CD4+ T cells, and B cells particularly following dapagliflozin treatment at 5 mg/kg. Dapagliflozin treatment also markedly attenuated medial SMC loss. Though the difference was not significant, dapagliflozin treatment tended to attenuate CD8+ T cells and elastin degradation. Dapagliflozin treatment at 5 mg/kg caused a 53% reduction in neovessel density. Furthermore, dapagliflozin treatment mitigated further progress of existing AAAs. Conclusion. Dapagliflozin treatment ameliorated PPE-induced AAAs by inhibiting aortic leukocytes infiltration and angiogenesis.

Integrated analysis and the identification of a circRNA-miRNA-mRNA network in the progression of abdominal aortic aneurysm

Background

Abdominal aortic aneurysm (AAA) is a disease commonly seen in the elderly. The aneurysm diameter increases yearly, and the larger the AAA the higher the risk of rupture, increasing the risk of death. However, there are no current effective interventions in the early stages of AAA.

Methods

Four gene expression profiling datasets, including 23 normal artery (NOR) tissue samples and 97 AAA tissue samples, were integrated in order to explore potential molecular biological targets for early intervention. After preprocessing, differentially expressed genes (DEGs) between AAA and NOR were identified using LIMMA package. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analysis were conducted using the DAVID database. The protein-protein interaction network was constructed and hub genes were identified using the STRING database and plugins in Cytoscape. A circular RNA (circRNA) profile of four NOR tissues versus four AAA tissues was then reanalyzed. A circRNA-miRNA-mRNA interaction network was constructed after predictions were made using the Targetscan and Circinteractome databases.

Results

A total of 440 DEGs (263 up-regulated and 177 down-regulated) were identified in the AAA group, compared with the NOR group. The majority were associated with the extracellular matrix, tumor necrosis factor-α, and transforming growth factor-β. Ten hub gene-encoded proteins (namely IL6, RPS27A, JUN, UBC, UBA52, FOS, IL1B, MMP9, SPP1 and CCL2) coupled with a higher degree of connectivity hub were identified after protein‐protein interaction network analysis. Our results, in combination with the results of previous studies revealed that miR-635, miR-527, miR-520h, miR-938 and miR-518a-5p may be affected by circ_0005073 and impact the expression of hub genes such as CCL2, SPP1 and UBA52. The miR-1206 may also be affected by circ_0090069 and impact RPS27A expression.

Conclusions

This circRNA-miRNA-mRNA network may perform critical roles in AAA and may be a novel target for early intervention.

Platelet protects angiotensin II-driven abdominal aortic aneurysm formation through inhibition of inflammation

BACKGROUND

Inflammation is the primary cause of abdominal aortic aneurysm (AAA) formation and development. It has been reported that platelets protect against septic shock by inhibiting inflammation. However, it is unclear whether platelets protect AAA progress via suppressing inflammation.

METHODS

A mouse model of AAA was established by a daily administration of angiotensin II (Ang II, 1000 ng/kg/min) for 28-day. The AAA mice received 1 × 10⁹ platelets transfusion in normal saline every 3rd day for 1 month. Hematoxylin and eosin, Masson's trichrome, and elastic van Gieson staining techniques were used to analyze the morphology of the abdominal aorta. Immunohistochemistry was used to detect any infiltration of inflammatory cells, inflammatory factors, and matrix metalloproteins (MMPs) in the aortic tissue. Western blot and enzyme-linked immunosorbent assay (ELISA) were used to examine the inflammatory factor proteins levels in the aortic wall and peripheral blood, respectively.

RESULTS

Platelets infusion significantly suppressed the Ang II-driven elevation of aortic diameter, AAA formation (52.38% decrease, P < 0.05), aortic expansion, elastic lamina destruction, and inflammatory response. In addition, MMP-2 and MMP-9 production were also reduced by platelets transfusion.

CONCLUSIONS

For the first time, our study reported the beneficial effect of platelet transfusion in suppressing the Ang II-driven AAA progress in mice through the inhibition of inflammation.

AAA Revisited: A Comprehensive Review of Risk Factors, Management, and Hallmarks of Pathogenesis

Despite declining incidence and mortality rates in many countries, the abdominal aortic aneurysm (AAA) continues to represent a life-threatening cardiovascular condition with an overall prevalence of about 2-3% in the industrialized world. While the risk of AAA development is considerably higher for men of advanced age with a history of smoking, screening programs serve to detect the often asymptomatic condition and prevent aortic rupture with an associated death rate of up to 80%. This review summarizes the current knowledge on identified risk factors, the multifactorial process of pathogenesis, as well as the latest advances in medical treatment and surgical repair to provide a perspective for AAA management.