A disintegrin and metalloprotease -8 and -15 and susceptibility for ascending aortic dissection

Aortic elastic fiber degeneration during acute type a aortic dissection and reverse aortic remodeling

BACKGROUND

Progression of proximal or distal aortic dilatation is defined as reverse aortic remodeling after surgery for acute type A aortic dissection (ATAAD) that may be dependent on aortic wall degeneration.

METHODS

We investigated whether aortic wall degeneration is associated with reverse aortic remodeling leading to aortic reoperation after surgery for ATAAD. Altogether, 141 consecutive patients undergoing surgery for ATAAD at Tampere were evaluated. The resected ascending aortic wall at surgery was processed for 42 degenerative, atherosclerotic and inflammatory histological variables. Patients undergoing aortic reoperations (Redos) were compared with those without aortic reoperations (Controls) during a mean 4.9-year follow-up.

RESULTS

Redos were younger than Controls (56 and 66 years, respectively, P < 0.001), and had less frequently previous cardiac surgery prior to ATAAD. Initial surgery encompassed replacement of the ascending aorta in the majority. There were 21 Redos in which one patient died during follow-up as compared with 51 deaths in Controls (log Rank P = 0.002). Histology of the aortic wall revealed increased elastic fiber fragmentation, loss, and disorganization in Redos as compared with Controls (2.1 ± 0.5 vs. 1.9 ± 0.5, Point score unit (PSU), P = 0.043 and 1.7 ± 0.8 vs. 1.2 ± 0.8, PSU, P = 0.016, respectively). Moderate atherosclerosis occurred less often in Redos vs. Controls (9.5% vs. 33%, PSU, P = 0.037, respectively).

CONCLUSIONS

According to this exploratory study, histopathology reveals distinctive aortic wall degeneration during ATAAD. Reverse aortic remodeling after ATAAD is associated with the presence of ascending aortic wall elastic fiber fragmentation, loss and disorganization during ATAAD.

Disintegrin and Metalloproteinases (ADAMs [A Disintegrin and Metalloproteinase] and ADAMTSs [ADAMs With a Thrombospondin Motif]) in Aortic Aneurysm

Aortic aneurysm is a complex pathology that can be lethal if not detected in time. Although several molecular mechanisms and pathways have been identified to be involved in aortic aneurysm development and growth, the current lack of an effective pharmacological treatment highlights the need for a more thorough understanding of the factors that regulate the remodeling of the aortic wall in response to triggers that lead to aneurysm formation. This task is further complicated by the regional heterogeneity of the aorta and that thoracic and abdominal aortic aneurysm are distinct pathologies with different risk factors and distinct course of progression. ADAMs (a disintegrin and metalloproteinases) and ADAMTS (ADAMs with a thrombospondin motif) are proteinases that share similarities with other proteinases but possess unique and diverse properties that place them in a category of their own. In this review, we discuss what is known on how ADAMs and ADAMTSs are altered in abdominal aortic aneurysm and thoracic aortic aneurysm in patients, in different animal models, and their role in regulating the function of different vascular and inflammatory cell types. A full understanding of the role of ADAMs and ADAMTSs in aortic aneurysm will help reveal a more complete understanding of the underlying mechanism driving aneurysm formation, which will help towards developing an effective treatment in preventing or limiting the growth of aortic aneurysm.

Research progress on the pathogenesis of aortic dissection

Aortic dissection (AD) is a critical cardiovascular disease due to the separation of media and adventitia caused by the rupture of vascular wall intima. The disease has a high mortality rate of about 1% to 3% for each additional hour, since the adventitia of the aorta can rupture and bleed to death at any time. Although great progress has been made in clinical treatment of aortic dissection, and the mortality rate has been significantly reduced, the pathogenesis is still not very clear. At present, related studies have confirmed that inflammation of aortic wall promotes the occurrence and development of AD. Although the mechanism of aortic dissection is more complicated, some studies have shown that the infiltration of monocytes/macrophages into the aortic wall is the main pathogenic mechanism of the disease. This review introduces the latest research results on the mechanism of macrophage infiltration and plasticity in aortic dissection.

Ascending aortic wall degeneration in patients with bicuspid versus tricuspid aortic valve

Background

The magnitude of ascending aortic degeneration in patients with bicuspid aortic valves (BAV) is controversial.

Methods

The aim of this study was to investigate ascending aortic wall degeneration in patients with BAV as compared with tricuspid aortic valves (TAV). The ascending aortic wall of 67 consecutive patients was processed for histology and immunohistochemistry. The extent of surgery and wall degeneration were investigated. Unadjusted survival was evaluated by Kaplan–Meier analysis. Median follow-up for patients with BAV and TAV was 3.8 years (interquartile range [IQR] 3.5–4.1) and 3.7 years (IQR 3.4–3.9), respectively.

Results

There were 33 patients with BAV and 34 with TAV. Mid-ascending aorta diameter was 54 mm (IQR 50–60). Replacement of the aortic valve, together with an ascending aortic prosthesis, was more frequent in BAV vs TAV patients (24% vs. 3%, P = 0.013). However, medial fibrosis, elastic fiber thinning, incremental medial degeneration and smooth muscle cell nuclei loss were less prominent in BAV vs TAV patients (0.1 ± 0.4 vs. 0.8 ± 1.4, P = 0.016; 0.6 ± 1.4 vs. 1.6 ± 2.0, P = 0.027; 1.7 ± 0.7 vs. 2.2 ± 0.8, P = 0.045 and 2.3 ± 1.5 vs. 3.2 ± 1.3, P = 0.026, respectively).

Conclusions

Since degeneration of the ascending aortic wall was seldom prominent, histopathology alone may not support the need for surgery of the dilated ascending aorta in BAV patients as compared with TAV patients.

ADAM and ADAMTS disintegrin and metalloproteinases as major factors and molecular targets in vascular malfunction and disease

A Disintegrin and Metalloproteinase (ADAM) and A Disintegrin and Metalloproteinase with Thrombospondin Motifs (ADAMTS) are two closely related families of proteolytic enzymes. ADAMs are largely membrane-bound enzymes that act as molecular scissors or sheddases of membrane-bound proteins, growth factors, cytokines, receptors and ligands, whereas ADAMTS are mainly secreted enzymes. ADAMs have a pro-domain, and a metalloproteinase, disintegrin, cysteine-rich and transmembrane domain. Similarly, ADAMTS family members have a pro-domain, and a metalloproteinase, disintegrin, and cysteine-rich domain, but instead of a transmembrane domain they have thrombospondin motifs. Most ADAMs and ADAMTS are activated by pro-protein convertases, and can be regulated by G-protein coupled receptor agonists, Ca²⁺ ionophores and protein kinase C. Activated ADAMs and ADAMTS participate in numerous vascular processes including angiogenesis, vascular smooth muscle cell proliferation and migration, vascular cell apoptosis, cell survival, tissue repair, and wound healing. ADAMs and ADAMTS also play a role in vascular malfunction and cardiovascular diseases such as hypertension, atherosclerosis, coronary artery disease, myocardial infarction, heart failure, peripheral artery disease, and vascular aneurysm. Decreased ADAMTS13 is involved in thrombotic thrombocytopenic purpura and microangiopathies. The activity of ADAMs and ADAMTS can be regulated by endogenous tissue inhibitors of metalloproteinases and other synthetic small molecule inhibitors. ADAMs and ADAMTS can be used as diagnostic biomarkers and molecular targets in cardiovascular disease, and modulators of ADAMs and ADAMTS activity may provide potential new approaches for the management of cardiovascular disorders.

Excessive DNA damage mediates ECM degradation via the RBBP8/NOTCH1 pathway in sporadic aortic dissection

Stanford type A aortic dissection (TA-AD) is a life-threatening disease. Most cases of aortic dissection (AD) are sporadic rather than inherited. Unlike that of inherited AD, the pathogenesis of sporadic AD is still unclear. In the current study, we aimed to explore the pathogenesis of sporadic AD through transcriptome sequencing data analyses. We downloaded sporadic TA-AD transcriptome profiles from Gene Expression Omnibus (GEO) and found response to DNA damage stimulus was activated in AD. Furthermore, by conducting mouse AD tissue single cell RNA sequencing and immunostaining, we found that DNA damage mainly occurred in smooth muscle cells (SMCs) and fibroblasts. Next, we examined the repair patterns in response to DNA damage and found the linker molecules RBBP8/NOTCH1 between DNA damage/repair and extracellular matrix (ECM) organization through protein-protein interaction analysis. Thus, we proposed that DNA damage could contribute to AD by regulating ECM changes. To explore the underlying mechanism, we knocked down the DNA repair-related gene RBBP8 in aortic SMCs, which could exacerbate DNA damage, and observed decreased expression level of NOTCH1. Inhibition of NOTCH1 with crenigacestat in vivo accelerated β-aminopropionitrile-induced formation of AD and increased mortality. Meanwhile, phenotype switching of SMCs was induced by Notch1 knockdown or inhibition; this switching occurred via a pathway involving downregulation of contractile marker gene expression and upregulation of MMP2 expression, which might aggravate ECM degradation. In conclusion, excessive DNA damage is a characteristic pathological change of sporadic aortic dissection, which might contribute to ECM changes and AD development via action on the NOTCH1 pathway.

Contribution of ADAM17 and related ADAMs in cardiovascular diseases

A disintegrin and metalloproteases (ADAMs) are key mediators of cell signaling by ectodomain shedding of various growth factors, cytokines, receptors and adhesion molecules at the cellular membrane. ADAMs regulate cell proliferation, cell growth, inflammation, and other regular cellular processes. ADAM17, the most extensively studied ADAM family member, is also known as tumor necrosis factor (TNF)-α converting enzyme (TACE). ADAMs-mediated shedding of cytokines such as TNF-α orchestrates immune system or inflammatory cascades and ADAMs-mediated shedding of growth factors causes cell growth or proliferation by transactivation of the growth factor receptors including epidermal growth factor receptor. Therefore, increased ADAMs-mediated shedding can induce inflammation, tissue remodeling and dysfunction associated with various cardiovascular diseases such as hypertension and atherosclerosis, and ADAMs can be a potential therapeutic target in these diseases. In this review, we focus on the role of ADAMs in cardiovascular pathophysiology and cardiovascular diseases. The main aim of this review is to stimulate new interest in this area by highlighting remarkable evidence.

High NOR-1 (Neuron-Derived Orphan Receptor 1) Expression Strengthens the Vascular Wall Response to Angiotensin II Leading to Aneurysm Formation in Mice

No drug therapy has shown to limit abdominal aortic aneurysm (AAA) growth or rupture, and the understanding of the disease biology is incomplete; whereby, one challenge of vascular medicine is the development of good animal models and therapies for this life-threatening condition. The nuclear receptor NOR-1 (neuron-derived orphan receptor 1) controls biological processes involved in AAA; however, whether it plays a role in this pathology is unknown. Through a gain-of-function approach we assessed the impact of NOR-1 expression on the vascular response to Ang II (angiotensin II). We used 2 mouse models that overexpress human NOR-1 in the vasculature, one of them specifically in vascular smooth muscle cells. NOR-1 transgenesis amplifies the response to Ang II enhancing vascular inflammation (production of proinflammatory cytokines, chemokines, and reactive oxygen species), increasing MMP (matrix metalloproteinase) activity and disturbing elastin integrity, thereby broking the resistance of C57BL/6 mice to Ang II-induced AAA. Genes encoding for proteins critically involved in AAA formation (Il [interleukin]-6, Il-1β, Cxcl2, [C-X-C motif chemokine ligand 2], Mcp-1 [monocyte chemoattractant protein 1], and Mmp2) were upregulated in aneurysmal tissues. Both animal models show a similar incidence and severity of AAA, suggesting that high expression of NOR-1 in vascular smooth muscle cell is a sufficient condition to strengthen the response to Ang II. These alterations, including AAA formation, were prevented by the MMP inhibitor doxycycline. Microarray analysis identified gene sets that could explain the susceptibility of transgenic animals to Ang II-induced aneurysms, including those related with extracellular matrix remodeling, inflammatory/immune response, sympathetic activity, and vascular smooth muscle cell differentiation. These results involve NOR-1 in AAA and validate mice overexpressing this receptor as useful experimental models.

Neovascularization with chronic inflammation characterizes ascending aortic dissection

Objective:

Neovascularization of the aortic wall may be associated with aortic dissection (AD). Aortic wall endothelial CD31 deposition together with chronic inflammation indicates angiogenesis that may lead to tissue disruption. We studied the presence of neovascularization of the ascending aortic wall by characterizing CD31 positive endothelial cells.

Methods:

Aortic wall routine histology and immunohistochemistry for CD31, T- and B-lymphocytes, plasma cells, macrophages, endothelial cells, smooth muscle cells, and cell proliferation were performed on 35 selected patients who underwent surgery for the ascending aorta, and the samples were grouped according to the presence of AD.

Results:

Three subjects with Marfan syndrome were excluded from the study. A total of 14 out of 32 patients had AD. A total of 18 patients were operated on due to dilatation only. Chronic inflammation of the adventitia (p=0.003), media (p=0.001), and intima (p=0.005) was increased in AD. Neovascularization was predominant in the outer third medial layer in AD (p=0.037), corresponding to the site of aortic wall disruption. A receiver operating characteristic curve analysis showed that neovascularization was associated with AD (AUC 0.750; SE 0.092; p=0.022; 95% CI 0.570–0.930).

Conclusion:

Endothelial immunohistochemistry confirms neovascularization of the outer third medial layer during AD. Aortic wall remodeling including neovascularization characterizes AD. Chronic inflammation and neovascularization of the dilated ascending aorta suggest susceptibility for AD.

Differentially expressed genes and canonical pathways in the ascending thoracic aortic aneurysm - The Tampere Vascular Study

Ascending thoracic aortic aneurysm (ATAA) is a multifactorial disease with a strong inflammatory component. Surgery is often required to prevent aortic rupture and dissection. We performed gene expression analysis (Illumina HumanHT-12 version 3 Expression BeadChip) for 32 samples from ATAA (26 without/6 with dissection), and 28 left internal thoracic arteries (controls) collected in Tampere Vascular study. We compared expression profiles and conducted pathway analysis using Ingenuity Pathway Analysis (IPA) to reveal differences between ATAA and a healthy artery wall. Almost 5000 genes were differentially expressed in ATAA samples compared to controls. The most downregulated gene was homeobox (HOX) A5 (fold change, FC = -25.3) and upregulated cadherin-2 (FC = 12.6). Several other HOX genes were also found downregulated (FCs between -25.3 and -1.5, FDR < 0.05). 43, mostly inflammatory, canonical pathways in ATAA were found to be significantly (p < 0.05, FDR < 0.05) differentially expressed. The results remained essentially the same when the 6 dissected ATAA samples were excluded from the analysis. We show for the first time on genome level that ATAA is an inflammatory process, revealing a more detailed molecular pathway level pathogenesis. We propose HOX genes as potentially important players in maintaining aortic integrity, altered expression of which might be important in the pathobiology of ATAA.

Carbonic anhydrase IX deposits are associated with increased ascending aortic dilatation

OBJECTIVES

Carbonic anhydrase IX (CA IX) expression is induced by local hypoxia. We studied whether CA IX deposits associate with ascending aortic dilatation.

DESIGN

Aortic wall histology, CA IX expression, presence of leukocytes, plasma cells, macrophages, endothelial cells, smooth muscle cells, cell proliferation, elastin and collagen were studied in histological specimens collected from 30 patients who underwent surgery for ascending aorta. The samples were grouped according to presence of CA IX deposits.

RESULTS

Twenty out of 30 patients had CA IX-positive deposits within the adventitia, whereas 10 specimens remained negative. Adventitial inflammation was increased in CA IX-positive samples as compared with CA IX-negative ones (p < 0.01). The mean diameter of the ascending aorta at the sinotubular junction increased significantly in patients with CA IX-positive staining as compared with CA IX-negative cases (63 ± 3 vs 53 ± 2 mm, p < 0.02). Receiver operating characteristic curve analysis confirmed the association of CA IX positivity with increased ascending aortic dilatation (AUC 0.766; S.E. 0.090; p = 0.020; 95% C.I. 0.590-0.941).

CONCLUSIONS

Positive CA IX staining in certain aortic specimens suggests that increased CA activity may contribute to ascending aortic dilatation.

Stanford-A acute aortic dissection, inflammation, and metalloproteinases: a review

Acute aortic dissection (AAD) is a life-threatening disease with an incidence of about 2.6-3.6 cases per 100,000/year. Depending on the site of rupture, AAD is classified as Stanford-A when the ascending aortic thoracic tract and/or the arch are involved, and Stanford-B when the descending thoracic aorta and/or aortic abdominal tract are targeted. It was recently shown that inflammatory pathways underlie aortic rupture in both type A and type B Stanford AAD. An immune infiltrate has been found within the middle and outer tunics of dissected aortic specimens. It has also been observed that the recall and activation of macrophages inside the middle tunic are key events in the early phases of AAD. Macrophages are able to release metalloproteinases (MMPs) and pro-inflammatory cytokines which, in turn, give rise to matrix degradation and neoangiogenesis. An imbalance between the production of MMPs and MMP tissue inhibitors is pivotal in the extracellular matrix degradation underlying aortic wall remodelling in dissections occurring both in inherited conditions and in atherosclerosis. Among MMPs, MMP-12 is considered a specific marker of aortic wall disease, whatever the genetic predisposition may be. The aim of this review is, therefore, to take a close look at the immune-inflammatory mechanisms underlying Stanford-A AAD.

Aiming at one-stage corrective surgery for extended thoracic aortic dilatation

Definitive treatment of extended thoracic aortic dilatation is a major surgical challenge. Histopathology of resected thoracic aortic wall may reveal undiagnosed aortitis affecting outcome. We sought to investigate the benefit of thorough histopathology after one-stage corrective surgery for the treatment of extended thoracic aortic dilatation. Five patients underwent one-stage corrective surgery using the hybrid open arch repair by the frozen elephant trunk together with endovascular aortic grafting. A representative sample of the resected aortic arch was procured for histology. T- and B-lymphocytes, plasma cells, macrophages, and immunoglobulin G4 (IgG4) positivity were evaluated by immunohistochemistry. The mean preoperative maximum aortic diameter was 54 mm (range, 41-79 mm). The mean follow-up was 18 months (range, 1-24 months). As confirmed by computed tomography (CT) upon follow-up, complete thrombosis of the false lumen at the level of the frozen elephant trunk was achieved in all patients with dissection. One patient was operated due to atherosclerotic dilatation of the thoracic aorta, and postoperative CT showed successful exclusion of the atherosclerotic dilatation; this 75-year-old man was diagnosed with IgG4-positive aortitis and experienced unexpected blindness after surgery without evidence of emboli or long-term neurological impairment upon repeated brain CT. The hybrid open arch repair by the frozen elephant trunk and simultaneous endovascular repair is a feasible choice for one-stage surgery through sternotomy aiming at definitive treatment of extended thoracic aortic pathology. However, systematic evaluation of inflammation may reveal concealed aortitis affecting postoperative outcome and need for long-term surveillance.

Biological features of thoracic aortic diseases. Where are we now, where are we heading to: established and emerging biomarkers and molecular pathways

Thoracic aortic aneurysms (TAAs) and aortic dissections (ADs) are among the main causes of mortality and morbidity in Western countries. For this reason, the diagnosis, prevention and prediction of TAAs and ADs have become a very active area of research; in fact, it is important to monitor and predict the evolution of these diseases over time. It is also critical, in cases of doubtful diagnosis, to receive some guidance from biochemical assays, particularly in the case of ADs. Although biological testing for disease prediction has already been discussed several times, the role of biomarkers in TAAs and ADs is still under discussion for routine patient screening, periodical follow-up or for prompt diagnosis in emergency conditions. In this review, we update the current knowledge and new trends regarding the role of biomarkers in thoracic aortic diseases, focusing on established and emerging biomarkers in the fields of genetics, inflammation, haemostasis and matrix remodelling as well as on substances released upon cell damage. Other than D-dimer, a sensitive but not a specific marker for the diagnosis of AD that has been widely tested by several authors and currently seems a viable option in ambiguous cases, the remaining markers have been most frequently assessed in limited or mixed patient populations. This currently precludes their widespread adoption as diagnostic or prognostic tools, even if many of these markers are conceptually promising. In years to come, we expect that future studies will further clarify the diagnostic and prognostic features of several established and emerging biomarkers that, to date, are still in the translational limbo separating biological discovery from a practical clinical role.

A particular phenotype of ascending aorta aneurysms as precursor of type A aortic dissection

OBJECTIVES

We aimed to identify a phenotype of ascending thoracic aortic aneurysm (TAA), which, more than others, evolves into type A dissection (TAD).

METHODS

Aortic specimens were obtained from patients undergoing surgical repair of TAA and TAD (108 and 26, respectively). Histopathological and immunohistochemical analyses were performed by using adequate tissue specimens, appropriate techniques and criteria.

RESULTS

We identified the three following TAA phenotypes: phenotype I (cystic medial degeneration balanced by a substitutive fibrosis, in absence of medial apoptosis and with a faint collagenase concentration), phenotype II (cystic medial degeneration of higher grade, respectively, than substitutive fibrosis, with focal medial apoptosis and moderate collagenase concentration), and phenotype III (elevated cystic medial degeneration without substitutive fibrosis, with plurifocal medial apoptosis and severe collagenase concentration). The same medial degenerative lesions of TAA phenotype III were observed in TAD tissue samples.

CONCLUSIONS

The morphological identity of medial lesions observed in both the TAA phenotype III and in TAD aortas might be assumed to be the precursor-and consequently the optimal biomarker- of dissection, independently of aneurysm diameter or valvular disorder. Identification of genetic risk factors, useful both in diagnostics and in developing more targeted treatment for individual patients, might also be needed.