Cathepsins: a new culprit behind abdominal aortic aneurysm

Intracranial Aneurysms and Genetics: An Extensive Overview of Genomic Variations, Underlying Molecular Dynamics, Inflammatory Indicators, and Forward-Looking Insights

This review initiates by outlining the clinical relevance of IA, underlining the pressing need to comprehend its foundational elements. We delve into the assorted risk factors tied to IA, spotlighting both environmental and genetic influences. Additionally, we illuminate distinct genetic syndromes linked to a pronounced prevalence of intracranial aneurysms, underscoring the pivotal nature of genetics in this ailment's susceptibility. A detailed scrutiny of genome-wide association studies allows us to identify key genomic changes and locations associated with IA risk. We further detail the molecular and physiopathological dynamics instrumental in IA's evolution and escalation, with a focus on inflammation's role in affecting the vascular landscape. Wrapping up, we offer a glimpse into upcoming research directions and the promising horizons of personalized therapeutic strategies in IA intervention, emphasizing the central role of genetic insights. This thorough review solidifies genetics' cardinal role in IA, positioning it as a cornerstone resource for professionals in the realms of neurology and genomics.

Surface-Functionalized Stem Cell-Derived Extracellular Vesicles for Vascular Elastic Matrix Regenerative Repair

Extracellular vesicles (EVs) are nanosized vesicles that carry cell-specific biomolecular information. Our previous studies showed that adult human bone marrow mesenchymal stem cell (BM-MSC)-derived EVs provide antiproteolytic and proregenerative effects in cultures of smooth muscle cells (SMCs) derived from an elastase-infused rat abdominal aortic aneurysm (AAA) model, and this is promising toward their use as a therapeutic platform for naturally irreversible elastic matrix aberrations in the aortic wall. Since systemically administered EVs poorly home into sites of tissue injury, disease strategies to improve their affinity toward target tissues are of great significance for EV-based treatment strategies. Toward this goal, in this work, we developed a postisolation surface modification strategy to target MSC-derived EVs to the AAA wall. The EVs were surface-conjugated with a short, synthetic, azide-modified peptide sequence for targeted binding to cathepsin K (CatK), a cysteine protease overexpressed in the AAA wall. Conjugation was performed using a copper-free click chemistry method. We determined that such conjugation improved EV uptake into cultured aneurysmal SMCs in culture and their binding to the wall of matrix injured vessels ex vivo. The proregenerative and antiproteolytic effects of MSC-EVs on cultured rat aneurysmal SMCs were also unaffected following peptide conjugation. From this study, it appears that modification with short synthetic peptide sequences seems to be an effective strategy for improving the cell-specific uptake of EVs and may be effective in facilitating AAA-targeted therapy.

Structural Remodeling of the Extracellular Matrix in Arteriogenesis: A Review

Lower extremity arterial occlusive disease (AOD) results in significant morbidity and mortality for the population, with up to 10% of patients ultimately requiring amputation. An alternative method for non-surgical revascularization which is yet to be fully understood is the optimization of the body's own natural collateral arterial network in a process known as arteriogenesis. Under conditions of conductance vessel stenosis or occlusion resulting in increased flow, shear forces, and pressure gradients within collaterals, positive remodeling occurs to increase the diameter and capacity of these vessels. The creation of a distal arteriovenous fistula (AVF) will drive increased arteriogenesis as compared to collateral formation with the occlusion of a conductance vessel alone by further increasing flow through these arterioles, demonstrating the capacity for arteriogenesis to form larger, more efficient collaterals beyond what is spontaneously achieved after arterial occlusion. Arteries rely on an extracellular matrix (ECM) composed of elastic fibers and collagens that provide stability under hemodynamic stress, and ECM remodeling is necessary to allow for increased diameter and flow conductance in mature arterial structures. When positive remodeling occurs, digestion of lamella and the internal elastic lamina (IEL) by matrix metalloproteinases (MMPs) and other elastases results in the rearrangement and thinning of elastic structures and may be replaced with disordered elastin synthesis without recovery of elastic function. This results in transmission of wall strain to collagen and potential for aneurysmal degeneration along collateral networks, as is seen in the pancreaticoduodenal artery (PDA) after celiac occlusion and inferior mesenteric artery (IMA) with concurrent celiac and superior mesenteric artery (SMA) occlusions. Further understanding into the development of collaterals is required to both better understand aneurysmal degeneration and optimize collateral formation in AOD.

Pathogenic mechanisms and the potential of drug therapies for aortic aneurysm

Aortic aneurysm is a permanent focal dilation of the aorta. It is usually an asymptomatic disease but can lead to sudden death due to aortic rupture. Aortic aneurysm-related mortalities are estimated at ∼200,000 deaths per year worldwide. Because no pharmacological treatment has been found to be effective so far, surgical repair remains the only treatment for aortic aneurysm. Aortic aneurysm results from changes in the aortic wall structure due to loss of smooth muscle cells and degradation of the extracellular matrix and can form in different regions of the aorta. Research over the past decade has identified novel contributors to aneurysm formation and progression. The present review provides an overview of cellular and noncellular factors as well as enzymes that process extracellular matrix and regulate cellular functions (e.g., matrix metalloproteinases, granzymes, and cathepsins) in the context of aneurysm pathogenesis. An update of clinical trials focusing on therapeutic strategies to slow abdominal aortic aneurysm growth and efforts underway to develop effective pharmacological treatments is also provided.

Extracellular matrix, regional heterogeneity of the aorta, and aortic aneurysm

Aortic aneurysm is an asymptomatic disease with dire outcomes if undiagnosed. Aortic aneurysm rupture is a significant cause of death worldwide. To date, surgical repair or endovascular repair (EVAR) is the only effective treatment for aortic aneurysm, as no pharmacological treatment has been found effective. Aortic aneurysm, a focal dilation of the aorta, can be formed in the thoracic (TAA) or the abdominal (AAA) region; however, our understanding as to what determines the site of aneurysm formation remains quite limited. The extracellular matrix (ECM) is the noncellular component of the aortic wall, that in addition to providing structural support, regulates bioavailability of an array of growth factors and cytokines, thereby influencing cell function and behavior that ultimately determine physiological or pathological remodeling of the aortic wall. Here, we provide an overview of the ECM proteins that have been reported to be involved in aortic aneurysm formation in humans or animal models, and the experimental models for TAA and AAA and the link to ECM manipulations. We also provide a comparative analysis, where data available, between TAA and AAA, and how aberrant ECM proteolysis versus disrupted synthesis may determine the site of aneurysm formation.

A review of aneurysm formation, swelling in blood vessel, in the aorta, examines distinctions between two forms of the condition and the role of proteins in the extracellular matrix which surrounds cells of the arterial wall. Rupture of aneurysms in the aorta, the body’s main artery, is a major cause of death. Researchers led by Zamaneh Kassiri at the University of Alberta, Edmonton, Canada, emphasize that aneurysms in the thoracic and abdominal regions of the aorta are distinct conditions with crucial differences in their causes. Disrupted production and assembly of the extracellular matrix and its proteins may underlie thoracic aneurysm formation. Factors triggering the degradation of extracellular matrix proteins may be more significant in abdominal aneurysms. Understanding the differing molecular mechanisms involved could help address the current lack of effective drug treatments for these dangerous conditions.

Deletion of interleukin-18 attenuates abdominal aortic aneurysm formation

BACKGROUND AND AIMS

Abdominal aortic aneurysm (AAA) is a common disease; however, its exact pathogenesis remains unknown, and no specific medical therapies are available. Interleukin (IL)-18 plays a crucial role in atherosclerotic plaque destabilization and is a strong predictor of cardiovascular death. Here, we investigated the role of IL-18 in AAA pathogenesis using an experimental mouse model.

METHODS AND RESULTS

After infusion of angiotensin II (Ang II) for 4 weeks and β-aminopropionitrile (BAPN) for 2 weeks, 58% of C57/6J wild-type (WT) mice developed AAA associated with enhanced expression of IL-18; however, disease incidence was significantly lower in IL-18^-/- mice than in WT mice (p < 0.01), although no significant difference was found in systolic blood pressure between WT mice and IL-18^-/- mice in this model. Additionally, IL-18 deletion significantly attenuated Ang II/BAPN-induced macrophage infiltration, macrophage polarization into inflammatory M1 phenotype, and matrix metalloproteinase (MMP) activation in abdominal aortas, which is associated with reduced expression of osteopontin (OPN).

CONCLUSIONS

These findings indicate that IL-18 plays an important role in the development of AAA by enhancing OPN expression, macrophage recruitment, and MMP activation. Moreover, IL-18 represents a previously unrecognized therapeutic target for the prevention of AAA formation.

Matrix Metalloproteinase in Abdominal Aortic Aneurysm and Aortic Dissection

Abdominal Aortic Aneurysm (AAA) affects 4–5% of men over 65, and Aortic Dissection (AD) is a life-threatening aortic pathology associated with high morbidity and mortality. Initiators of AAA and AD include smoking and arterial hypertension, whilst key pathophysiological features of AAA and AD include chronic inflammation, hypoxia, and large modifications to the extra cellular matrix (ECM). As it stands, only surgical methods are available for preventing aortic rupture in patients, which often presents difficulties for recovery. No pharmacological treatment is available, as such researchers are attempting to understand the cellular and molecular pathophysiology of AAA and AD. Upregulation of matrix metalloproteinase (MMPs), particularly MMP-2 and MMP-9, has been identified as a key event occurring during aneurysmal growth. As such, several animal models of AAA and AD have been used to investigate the therapeutic potential of suppressing MMP-2 and MMP-9 activity as well as modulating the activity of other MMPs, and TIMPs involved in the pathology. Whilst several studies have offered promising results, targeted delivery of MMP inhibition still needs to be developed in order to avoid surgery in high risk patients.

Role of Noncoding RNAs in the Pathogenesis of Abdominal Aortic Aneurysm

Abdominal aortic aneurysm (AAA) is a local dilatation of the abdominal aortic vessel wall and is among the most challenging cardiovascular diseases as without urgent surgical intervention, ruptured AAA has a mortality rate of >80%. Most patients present acutely after aneurysm rupture or dissection from a previously asymptomatic condition and are managed by either surgery or endovascular repair. Patients usually are old and have other concurrent diseases and conditions, such as diabetes mellitus, obesity, and hypercholesterolemia making surgical intervention more difficult. Collectively, these issues have driven the search for alternative methods of diagnosing, monitoring, and treating AAA using therapeutics and less invasive approaches. Noncoding RNAs-short noncoding RNAs (microRNAs) and long-noncoding RNAs-are emerging as new fundamental regulators of gene expression. Researchers and clinicians are aiming at targeting these microRNAs and long noncoding RNAs and exploit their potential as clinical biomarkers and new therapeutic targets for AAAs. While the role of miRNAs in AAA is established, studies on long-noncoding RNAs are only beginning to emerge, suggesting their important yet unexplored role in vascular physiology and disease. Here, we review the role of noncoding RNAs and their target genes focusing on their role in AAA. We also discuss the animal models used for mechanistic understanding of AAA. Furthermore, we discuss the potential role of microRNAs and long noncoding RNAs as clinical biomarkers and therapeutics.

Cathepsin S is associated with degradation of collagen I in abdominal aortic aneurysm

BACKGROUND

Cathepsins have been described in the pathogenesis of abdominal aortic aneurysm (AAA), their exact role, especially in collagen degradation, is still unclear. The aim of the present study was therefore to analyse relevant cathepsins in human AAA tissue samples in relation to collagen I, III, and their degradation products.

MATERIALS AND METHODS

Samples from 37 AAA patients obtained from elective open surgical repair and eight healthy non-aneurysmatic aortas from kidney donors were included. Expression of cathepsins B, D, K, L, S, cystatin C, collagen I and III, their degraded products C-Telopeptide of type 1 and 3 collagen (CTX-I, CTX-III), cellular markers for leukocytes (CD45), T cells (CD3), macrophage scavenger receptor-1 (MSR-1), synthetic, and contractile smooth muscle cells (SMCs) (smoothelin: SMTH, collagen I and III, myosin heavy chain: MHC, embryonic smooth muscle myosin heavy chain: SMemb) were determined at messenger RNA (mRNA) level, using SYBRGreen-based quantitative PCR and at protein level using enzyme-linked immunosorbent assay (ELISA).

RESULTS

Expression of cathepsins B, D, L, and S at mRNA level was significantly elevated in AAA compared to control aorta (1.7-fold, p = 0.025; 2.5-fold, p = 0.002; 2.6-fold, p = 0.034; and 7.0-fold, p = 0.003). Expression of cathepsin S correlated significantly with leukocytes and macrophages (ρ = 0.398, p = 0.033 and ρ = 0.422, p = 0.020), synthetic SMCs were significantly associated with cathepsins B, D, and L (ρ = 0.522, p = 0.003; ρ = 0.431, p = 0.015 and ρ = 0.467, p = 0.008). At protein level, cathepsins B and S were elevated in AAA compared to controls (5.4-fold, p = 0.001 and 7.3-fold, p < 0.001). Significant correlations were observed between collagen I, its degraded product, and cathepsin S (r = -0.350, p = 0.034 and r = +0.504, p < 0.001). Expression of cathepsin B was associated with SMCs, expression of cathepsin S with inflammatory cells.

CONCLUSIONS

Particularly cathepsin S was associated with the degradation product of collagen I and thus might be involved in the progression of AAA. Furthermore, cathepsin S correlated with inflammatory cells.