Aortic dissecting aneurysms—Histopathological findings

Morphological Features of the Ascending Aorta Remodeling and Activation of Regeneratory Potential in Intima when Forming Aneurysm

In patients with an ascending aorta aneurysm, restructuring of all its layers and, first of all, the intima and media was revealed. The thickness of the intima was 79.3±63.1 μm in patients with aortic diameter <55 mm (group Ao<55) and 162.7±177.4 μm (p<0.05) in patients with aortic diameter ⩾55 mm (Ao⩾55 group), the thickness of the aortic media was 1184.0±198.2 and 1144.3±288.4 μm, respectively. In patients of the Ao<55 group, aortic dilatation was accompanied by compensatory thickening of the inner and middle layers of the aorta. In the Ao⩾55 group, thinning of the aortic media, fragmentation of elastic fibers, and its cystic degeneration were revealed. c-kit⁺ Stem cells were detected in the subendothelium of the thickened intima of the dilated ascending aorta. The appearance of c-kit⁺ cells correlated with intimal remodeling and its colonization with CD34⁺ and CD44⁺ myofibroblast-like cells.

Single-Cell RNA Sequencing Reveals Smooth Muscle Cells Heterogeneity in Experimental Aortic Dissection

Purpose: This study aims to illustrate the cellular landscape in the aorta of experimental aortic dissection (AD) and elaborate on the smooth muscle cells (SMCs) heterogeneity and functions among various cell types.

Methods: Male Apolipoprotein deficient (ApoE−/−) mice at 28 weeks of age were infused with Ang II (2,500 ng/kg/min) to induce AD. Aortas from euthanized mice were harvested after 7 days for 10×Genomics single-cell RNA sequencing (scRNA-seq), followed by the identification of cell types and differentially expressed genes (DEGs). Gene Ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis was conducted.

Results: AD was successfully induced in ApoE−/− mice. scRNA-seq identified 15 cell clusters and nine cell types, including non-immune cells (endothelials, fibroblasts, and SMCs) and immune cells (B cells, natural killer T cell, macrophages, dendritic cells, neutrophils, and mast cells). The relative numbers of SMCs were remarkably changed, and seven core DEGs (ACTA2,IL6,CTGF,BGN,ITGA8,THBS1, and CDH5) were identified in SMCs. Moreover, we found SMCs can differentiate into 8 different subtypes through single-cell trajectory analysis.

Conclusion: scRNA-seq technology can successfully identify unique cell composition in experimental AD. To our knowledge, this is the first study that provided the complete cellular landscape in AD tissues from mice, seven core DEGs and eight subtypes of SMCs were identified, and the SMCs have evolution from matrix type to inflammatory type.

Higher Plasma Aldosterone Concentrations Are Associated With Elevated Risk of Aortic Dissection and Aneurysm: a Case-Control Study

BACKGROUND

Animal models demonstrate circulating aldosterone leads to aortic dissection and aneurysm, whereas data from humans are lacking. Therefore, we aimed to examine the associations of plasma aldosterone concentrations (PAC) with aortic dissection and aneurysm.

METHODS

We identified patients with aortic dissection and aneurysm with assessed PAC before disease onset from hospital-based electronic database and set as case group. Simultaneously, age and gender-matched cohort with PAC measurement whereas without aortic dissection and aneurysm were selected as control group using ratio of 1:4. Multi-variable logistic regression analysis was used to assess the relationship of PAC with aortic dissection and aneurysm.

RESULTS

Totally, 133 cases and 531 controls (all hypertensive) were enrolled between 2004 and 2021, with 77.9% men, mean age of 55.5 years and PAC of 13.9 ng/dL. Case group showed significantly higher PAC(14.51 versus 13.65 ng/dL, P=0.012) than did control group. In logistic regression analysis, higher PAC exhibited 1.68-fold higher odds (95% CI, 1.14-2.48, P=0.008) for presence of aortic dissection and aneurysm, significant in adjusted model (odds ratio, 1.69 [95% CI, 1.11-2.57], P=0.015). In stratified analysis, the association between the 2 was observed in women of all ages and in men with coronary artery disease. Sensitivity analysis by excluding those under interfering agents at PAC measurement and those with primary aldosteronism did not change the relationship of the 2.

CONCLUSIONS

Higher PAC is associated with the increased odd for aortic dissection and aneurysm in patients with hypertension, even in the absence of primary aldosteronism, implying that PAC might be a target for prevention.

Pleural changes in patients with pneumothoraces and Marfan syndrome

Background

Patients with Marfan syndrome (MFS) often develop pneumothorax, but the features of pneumothorax in the context of MFS have not been well described in the literature. We clarified the clinical and histopathological characteristics of this condition in these patients.

Methods

Patients with MFS were selected from among all patients who underwent surgery for pneumothorax, between December 1991 and January 2015, in our hospital. We studied the histopathological characteristics of the resected lungs as well as the clinical features of the selected patients, including surgical findings and postoperative recurrence status.

Results

There were 966 operations underwent pneumothorax-related surgeries in our hospital. A total of 16 operations (1.66%) were performed on patients with MFS in 11 cases. In this study, 9 patients (6 men, 3 women) were included. Clinically, 7 patients (77.8%) had bilateral pneumothoraces and 4 (44.4%) exhibited postoperative recurrent pneumothoraces. Pathologically, the resected pulmonary bullae exhibited blood vessel cystic medial degeneration (55.6% of cases), calcification (55.6% of cases), and demonstrated elastic fiber fragmentation and degeneration (all cases).

Conclusions

As in few previous reports, many patients with MFS develop bilateral or postoperative recurrent pneumothoraces. In many patients, characteristic changes in the pulmonary bullae, possibly caused by degenerated elastic fibers, were observed.

AEBP1 Promotes the Occurrence and Development of Abdominal Aortic Aneurysm by Modulating Inflammation via the NF-κB Pathway

AIM

Inflammation plays a significant role in the pathogenesis of human abdominal aortic aneurysm (AAA). AEBP1 can promote activation of the NF-κB pathway, subsequently affecting the expression of NF-κB target genes, including inflammatory cytokines and matrix metalloproteinases (MMPs). Our objective was to examine the role of AEBP1 in the development of AAA and characterize the underlying mechanism.

METHODS

ITRAQ, RT-PCR, western blot, immunohistochemistry, and ELISA were used to compare different experimental groups with the controls and to determine the differentially expressed genes. We generated an AAA model using porcine pancreatic elastase in Sprague-Dawley rats and silenced their AEBP1 in vivo by adenoviruses injected intra-adventitially. We also silenced or overexpressed AEBP1 in human vascular smooth muscle cells in vitro in the presence and in the absence of NF-κB inhibitor BAY 11-7082.

RESULTS

Proteome iTRAQ revealed a high expression of AEBP1 in AAA patients, which was verified by qRT-PCR, western blot, immunohistochemistry, and ELISA. The mean expression level of AEBP1 in AAA patients was higher than that in controls. Along with AEBP1 upregulation, we also verified mis-activation of NF-κB in human AAA samples. The in vivo studies indicated that AEBP1 knockdown suppressed AAA progression. Finally, the in vitro studies illustrated that AEBP1 promotes activation of the NF-κB pathway, subsequently upregulating pro-inflammatory factors and MMPs.

CONCLUSIONS

Our results indicate a role of AEBP1 in the pathogenesis of AAA and provide a novel insight into how AEBP1 causes the development of AAA by activating the NF-κB pathway.

Failure properties and microstructure of healthy and aneurysmatic human thoracic aortas subjected to uniaxial extension with a focus on the media

Current clinical practice for aneurysmatic interventions is often based on the maximum diameter of the vessel and/or on the growth rate, although rupture can occur at any diameter and growth rate, leading to fatality. For 27 medial samples obtained from 12 non-aneurysmatic (control) and 9 aneurysmatic human descending thoracic aortas we examined: the mechanical responses up to rupture using uniaxial extension tests of circumferential and longitudinal specimens; the structure of these tissues using second-harmonic imaging and histology, in particular, the content proportions of collagen, elastic fibers and smooth muscle cells in the media. It was found that the mean failure stresses were higher in the circumferential directions (Control-C 1474kPa; Aneurysmatic-C 1446kPa), than in the longitudinal directions (Aneurysmatic-L 735kPa; Control-L 579kPa). This trend was the opposite to that observed for the mean collagen fiber directions measured from the loading axis (Control-L > Aneurysmatic-L > Aneurysmatic-C > Control-C), thus suggesting that the trend in the failure stress can in part be attributed to the collagen architecture. The difference in the mean values of the out-of-plane dispersion in the radial/longitudinal plane between the control and aneurysmatic groups was significant. The difference in the mean values of the mean fiber angle from the circumferential direction was also significantly different between the two groups. Most specimens showed delamination zones near the ruptured region in addition to ruptured collagen and elastic fibers. This study provides a basis for further studies on the microstructure and the uniaxial failure properties of (aneurysmatic) arterial walls towards realistic modeling and prediction of tissue failure. STATEMENT OF SIGNIFICANCE: A data set relating uniaxial failure properties to the microstructure of non-aneurysmatic and aneurysmatic human thoracic aortic medias under uniaxial extension tests is presented for the first time. It was found that the mean failure stresses were higher in the circumferential directions, than in the longitudinal directions. The general trend for the failure stresses was Control-C > Aneurysmatic-C > Aneurysmatic-L > Control-L, which was the opposite of that observed for the mean collagen fiber direction relative to the loading axis (Control-L > Aneurysmatic-L > Aneurysmatic-C > Control-C) suggesting that the trend in the failure stress can in part be attributed to the collagen architecture. This study provides a first step towards more realistic modeling and prediction of tissue failure.

Biomechanics of aortic wall failure with a focus on dissection and aneurysm: A review

Aortic dissections and aortic aneurysms are fatal events characterized by structural changes to the aortic wall. The maximum diameter criterion, typically used for aneurysm rupture risk estimations, has been challenged by more sophisticated biomechanically motivated models in the past. Although these models are very helpful for the clinicians in decision-making, they do not attempt to capture material failure. Following a short overview of the microstructure of the aorta, we analyze the failure mechanisms involved in the dissection and rupture by considering also traumatic rupture. We continue with a literature review of experimental studies relevant to quantify tissue strength. More specifically, we summarize more extensively uniaxial tensile, bulge inflation and peeling tests, and we also specify trouser, direct tension and in-plane shear tests. Finally we analyze biomechanically motivated models to predict rupture risk. Based on the findings of the reviewed studies and the rather large variations in tissue strength, we propose that an appropriate material failure criterion for aortic tissues should also reflect the microstructure in order to be effective. STATEMENT OF SIGNIFICANCE: Aortic dissections and aortic aneurysms are fatal events characterized by structural changes to the aortic wall. Despite the advances in medical, biomedical and biomechanical research, the mortality rates of aneurysms and dissections remain high. The present review article summarizes experimental studies that quantify the aortic wall strength and it discusses biomechanically motivated models to predict rupture risk. We identified contradictory observations and a large variation within and between data sets, which may be due to biological variations, different sample sizes, differences in experimental protocols, etc. Based on the findings of the reviewed literature and the rather large variations in tissue strength, it is proposed that an appropriate criterion for aortic failure should also reflect the microstructure.

Modeling lamellar disruption within the aortic wall using a particle-based approach

Aortic dissections associate with medial degeneration, thus suggesting a need to understand better the biophysical interactions between the cells and matrix that constitute the middle layer of the aortic wall. Here, we use a recently extended "Smoothed Particle Hydrodynamics" formulation to examine potential mechanisms of aortic delamination arising from smooth muscle cell (SMC) dysfunction or apoptosis, degradation of or damage to elastic fibers, and pooling of glycosaminoglycans (GAGs), with associated losses of medial collagen in the region of the GAGs. First, we develop a baseline multi-layered model for the healthy aorta that delineates medial elastic lamellae and intra-lamellar constituents. Next, we examine stress fields resulting from the disruption of individual elastic lamellae, lost SMC contractility, and GAG production within an intra-lamellar space, focusing on the radial transferal of loading rather than on stresses at the tip of the delaminated tissue. Results suggest that local disruptions of elastic lamellae transfer excessive loads to nearby intra-lamellar constituents, which increases cellular vulnerability to dysfunction or death. Similarly, lost SMC function and accumulations of GAGs increase mechanical stress on nearby elastic lamellae, thereby increasing the chance of disruption. Overall these results suggest a positive feedback loop between lamellar disruption and cellular dropout with GAG production and lost medial collagen that is more pronounced at higher distending pressures. Independent of the initiating event, this feedback loop can catastrophically propagate intramural delamination.

Histopathological evaluation of aortic dissection: a comparison of congenital versus acquired aortic wall weakness

OBJECTIVES

The aim of this study was to identify pathological changes of aortic dissection based on histopathological evaluation of aortic wall weakness by comparing patients with and without congenital abnormalities.

METHODS

We reviewed records of patients who underwent repair for dissection-related aortic disease between 2008 and 2015. Fifty patients (20 men and 30 women; mean age 66.9 ± 14.0 years) who underwent surgery with subsequent histopathological examination of the aortic wall were divided into 2 groups. Group 1 had congenital abnormalities, including Marfan syndrome and bicuspid aortic valve (n = 5), and Group 2 had no congenital abnormalities (n = 45). We compared the histopathological characteristics of the aortic wall in these patients.

RESULTS

There were significant differences in age and body surface area between the 2 groups. Although 80% of Group 1 patients developed dissection at the middle of the media, all Group 2 patients developed dissection at the outer one-third of the media, which is along the pathway of the vasa vasorum of the aortic wall. Both groups showed the same extent of degeneration of the vasa vasorum. Group 1 showed a severe score of mucoid extracellular matrix accumulation in the aortic media.

CONCLUSIONS

Although it may be multifactorial, congenital maldevelopment of the media tends to result in dissection of the centre of the media, and acquired aortic wall weakness is concentrated in the outer third of the media. Degeneration of the vasa vasorum may be an important emerging substrate for developing aortic dissection.

Relationships Between Phenotype and Function of Blood CD4+ T-Cells and Ascending Thoracic Aortic Aneurysm: an Experimental Study

Introduction

Non-familial ascending thoracic aorta dilation and aneurysms (TAAs) are silent diseases in elderly patients. Histopathology revealed that functionally polarized infiltrating CD4⁺ T-cells play a key role in aortic wall weakening.

Objective

To evaluate the possible associations between phenotype and cytokine production of circulating CD4⁺ T-lymphocytes and the presence of TAA in patients with aortic valve disease (AVD).

Methods

We studied blood samples from 10 patients with TAA and 10 patients with AVD. Flow cytometry was used to quantify: a) CD4⁺ T-lymphocytes surface expression of CD25, CD28, and chemokine receptors (CCR5, CXCR3, CX3CR1); b) fractions of in vitro stimulated CD4⁺ T-cells producing cytokines (interferon gamma [IFN-γ], interleukin [IL]-17A, IL-21, IL-10); c) CD4⁺CD25^highFoxP3⁺ regulatory T-cells (Treg) fraction. Enzyme-linked immunosorbent assays (ELISA) were performed for cytokines (IFN-γ, IL-6, IL-10, IL-17A, IL-23, transforming growth factor beta [TGF-β]) and chemokines (RANTES, CX3CL1).

Results

The total CD4⁺CD28^±CD4⁺/CX3CR1⁺ T-cells fraction was higher (P=0.0323) in AVD (20.452±4.673) than in TAA patients (8.633±2.030). The frequency ratio of CD4⁺ T-lymphocytes producing IFN-γ vs. IL-17A+IL-21 cytokine-producing CD4+ T-cells was higher (P=0.0239) in AVD (2.102±0.272) than in TAA (1.365±0.123) patients. The sum of CD4⁺CD28^±CD4⁺/CX3CR1⁺ T-cells correlated positively with values of the previous cytokine ratio (P=0.0002, R=0.732). The ratio of CD4⁺CD28^±CD4⁺/CX3CR1⁺ T-cells vs. Treg was higher (P=0.0008) in AVD (20.859±3.393) than in TAA (6.367±1.277) patients.

Conclusion

Our results show that the presence of TAA in subjects with AVD is associated with imbalance between phenotypic and cytokine-producing subsets of circulating CD4+ T-lymphocytes, prevalently oriented towards a pro-fibrotic and IFN-γ counteracting effect to functional polarization.

Acute aortic dissection diagnosed after embalming: macroscopic and microscopic findings

A 58-year-old man died suddenly in Madagascar and poisoning was suspected. The body was embalmed after death and the general state of preservation was good. We found a major aortic dissection with a large false lumen from the aortic root to the common iliac arteries and a hemopericardium with formalinized blood clot. The intimal tear was on the ascending aorta, and an intramural hemorrhage was noted at the right coronary artery, attesting to a retrograde dissection. Microscopic studies confirmed aortic dissection with extensive intramural hemorrhage and also confirmed the retrograde dissection to the right coronary artery with a reduction of 90% of the true lumen. Classically, aortic dissection occurs in individuals with hypertension and individuals with genetic disorders of collagen formation. The diagnosis is often first established at the postmortem examination. Aortic dissection is therefore dealt with largely in necropsy studies. The usual cause of death is rupture into the pericardial sac. One case of bloodless dissection has been reported but the sudden death was explained by acute myocardial ischemia secondary to dissection of the left coronary artery. In our case, we found major hemopericardium and also intramural hemorrhage at the right coronary artery. We were able to make the diagnosis of aortic dissection and exclude the suspicion of homicide 15 days after death and after embalming.

Non-traumatic and spontaneous hemothorax in the setting of forensic medical examination: a systematic literature survey

Spontaneous hemothorax is a well-known yet seldom-reported entity in forensic literature. While trauma-related hemothorax is frequently encountered in a medicolegal setting, non-traumatic and spontaneous hemothorax are relatively uncommon entities. The wide range of causes that can trigger fatal intrathoracic bleeding include thoracic aortic dissection, followed by vascular malformations, various oncological diseases, and connective tissue abnormalities. In rare instances, extramedullary hematopoiesis, ectopic pregnancy, congenital heart defects, amyloidosis, or parasitic diseases may constitute a source of bleeding. This etiological heterogeneity may, as a result, cause diagnostic difficulties during post-mortem elucidation of hemothorax. It should be borne in mind that hemothorax after low-energy trauma does not exclusively indicate traumatic hemorrhage, hence, the non-traumatic origin of bleeding must be taken into consideration. In this paper, we present a systematic review of the relevant literature enriched by the results of our observations to investigate the etiologies and recommendations for the post-mortem diagnosis of spontaneous hemothorax in an attempt to better delineate the possible medicolegal considerations. It is important that forensic pathologist as well as clinicians are aware of the diseases that could potentially give rise to fatal hemothorax.

Disparate Changes in the Mechanical Properties of Murine Carotid Arteries and Aorta in Response to Chronic Infusion of Angiotensin-II

Chronic infusion of angiotensin-II has proved useful for generating dissecting aortic aneurysms in atheroprone mice. These lesions preferentially form in the suprarenal abdominal aorta and sometimes in the ascending aorta, but reasons for such localization remain unknown. This study focused on why these lesions do not form in other large (central) arteries. Toward this end, we quantified and compared the geometry, composition, and biaxial material behavior (using a nonlinear constitutive relation) of common carotid arteries from three groups of mice: non-treated controls as well as mice receiving a subcutaneous infusion of angiotensin-II for 28 days that either did or did not lead to the development of a dissecting aortic aneurysm. Consistent with the mild hypertension induced by the angiotensin-II, the carotid wall thickened as expected and remodeled modestly. There was no evidence, however, of a marked loss of elastic fibers or smooth muscle cells, each of which appear to be initiating events for the development of aneurysms, and there was no evidence of intramural discontinuities that might give rise to dissections.

Biomechanical roles of medial pooling of glycosaminoglycans in thoracic aortic dissection

Spontaneous dissection of the human thoracic aorta is responsible for significant morbidity and mortality, yet this devastating biomechanical failure process remains poorly understood. In this paper, we present finite element simulations that support a new hypothesis for the initiation of aortic dissections that is motivated by extensive histopathological observations. Specifically, our parametric simulations show that the pooling of glycosaminoglycans/proteoglycans that is singularly characteristic of the compromised thoracic aorta in aneurysms and dissections can lead to significant stress concentrations and intra-lamellar Donnan swelling pressures. We submit that these localized increases in intramural stress may be sufficient both to disrupt the normal cell-matrix interactions that are fundamental to aortic homeostasis and to delaminate the layered microstructure of the aortic wall and thereby initiate dissection. Hence, pathologic pooling of glycosaminoglycans/proteoglycans within the medial layer of the thoracic aortic should be considered as a possible target for clinical intervention.

Aortic Dissection in the Young: A Case Report and Review of the Differential Diagnostic Considerations

Aortic dissection is a rare cause of death in young adults, which may be caused by acquired or congenital factors. We present the case of a 21-year-old man who died as a result of spontaneous aortic dissection and cardiac tamponade. At autopsy, signs of Marfan syndrome were evident both grossly and microscopically. Hodgkin lymphoma was also discovered, though was noncontributory to death. We review the causes of aortic dissection in young individuals, with a focus on the key differentiating features of predisposing inheritable connective tissue disorders. Given the implications for surviving family members, it is the obligation of the diligent forensic pathologist to be aware of these conditions, such that families may be alerted to the need for genetic counseling.

The Role of Inflammation in Type a Aortic Dissection: A Pilot Study

Type A aortic dissection (TAAD) is a severe cardiovascular disease with high mortality rates. Current evidence suggests inflammation as the main mechanism of its complex pathophysiology. Accordingly, in this study the eventual presence of inflammatory cells in aorta specimens and any contribution of these cells in both apoptosis and metalloproteinase levels were assessed. The potential relationship between plasma inflammatory molecules and TAAD was also detected. In addition, implication in TAAD susceptibility of ten common and functional single nucleotide polymorphisms (SNP)s of six candidate genes (CCR5, TLR4, ACE, eNOs, MMP-9 and −2) was determined. Thus, histo-pathological and immunoistochemical aorta examination, TUNEL testing, genotyping of ten SNPs were performed. Levels of plasma inflammatory molecules were also determined using ELISA technique. A significant inflammatory infiltrate was observed in the examined aortas. Consistent with these data, significantly higher plasma levels of systemic inflammatory mediators characterized the cases. In addition, a high risk genotype significantly associated with TAAD susceptibility was identified. Thus, inflammation producing MMPs, cytokines and death mediators seem to be the shared pathological mechanism for TAAD in the population examined.

Possible mechanical roles of glycosaminoglycans in thoracic aortic dissection and associations with dysregulated transforming growth factor-β

BACKGROUND

Four distinguishing histopathological characteristics of thoracic aortic aneurysms and dissections (TAADs) are the fragmentation or degradation of elastic fibers, loss of smooth muscle, pooling of glycosaminoglycans, and remodeling of fibrillar collagens. Of these, pooling of glycosaminoglycans appears to be unique to these lesions.

METHODS

This review acknowledges the importance of dysregulated transforming growth factor-β (TGF-β) in TAADs and offers a complementary hypothesis that increased TGF-β could contribute to the accumulation of glycosaminoglycans in the media of the proximal thoracic aorta. Regardless, observed pools of glycosaminoglycans could decrease tensile strength, cause stress concentrations, and increase intralamellar swelling pressure, all of which could initiate local delaminations that could subsequently propagate as dissections and result in a false lumen or rupture.

CONCLUSIONS

There is a pressing need to investigate potential mechanical as well as biological consequences of accumulated glycosaminoglycans in TAADs and to elucidate responsible signaling pathways, with particular attention to synthetic cells of nonmesodermal lineage. Such research could provide insight into the mechanisms of dissection and the seemingly paradoxical role of the over-expression of a cytokine that is typically associated with fibrosis but is implicated in a degenerative disease of the aorta that can result in a catastrophic mechanical failure.

Changes in aortic shape and diameters after death: comparison of early postmortem computed tomography with antemortem computed tomography

PURPOSE

The purpose of this study is to evaluate the postmortem deformation of the aorta on postmortem computed tomography (CT) by comparison with the antemortem CT in the same patient.

MATERIALS AND METHODS

A total of 58 non-traumatic patients without hemorrhagic events who underwent torso CT before and shortly after death were enrolled. Antemortem chest and abdominal CT were obtained in 44 cases and in 57 cases, respectively. The lengths of the major and minor axes of the ascending and descending thoracic aorta and the abdominal aorta were measured on both antemortem and postmortem CT in the same patient. To evaluate the shape of the aorta, the major axis-minor axis ratio (Ma-MiR) was calculated. Mean values of the diameters of the aorta and Ma-MiRs on postmortem CT were compared with those on antemortem CT using the Wilcoxon signed-rank test. We also evaluated the major and minor axes and Ma-MiRs on both antemortem and postmortem CT in two age groups: 65 years and under (n=13) and over 65 years (n=45).

RESULTS

At each level tested, the aorta significantly shrank after death (p<0.001) (ascending thoracic aorta, descending thoracic aorta, and abdominal aorta: 38.5 mm × 33.5 mm, 28.0 mm × 25.9 mm, and 24.4 mm × 21.8 mm on antemortem CT, 30.0 mm × 26.2 mm, 24.4 mm × 20.7 mm, and 21.5 mm × 14.5 mm on postmortem CT, respectively). The postmortem Ma-MiRs significantly increased at the descending thoracic aorta and the abdominal aorta (p<0.001). The diameters of the aorta are longer in older cases at all levels on both antemortem and postmortem CT. The reduction rates were larger in younger cases than older cases at all levels.

CONCLUSIONS

After death, the aorta shrunk at all levels, and became oval in shape in descending thoracic and abdominal aorta. The contraction was greater in younger cases than older cases. Investigators who interpret postmortem imaging should be aware of the postmortem deformation of the aorta.

Remodeling of intramural thrombus and collagen in an Ang-II infusion ApoE-/- model of dissecting aortic aneurysms

Fibrillar collagen endows the normal aortic wall with significant stiffness and strength and similarly plays important roles in many disease processes. For example, because of the marked loss of elastic fibers and functional smooth cells in aortic aneurysms, collagen plays a particularly important role in controlling the dilatation of these lesions and governing their rupture potential. Recent findings suggest further that collagen remodeling may also be fundamental to the intramural healing of arterial or aneurysmal dissections. To explore this possibility further, we identified and correlated regions of intramural thrombus and newly synthesized fibrillar collagen in a well-established mouse model of dissecting aortic aneurysms. Our findings suggest that intramural thrombus that is isolated from free-flowing blood creates a permissive environment for the synthesis of fibrillar collagen that, albeit initially less dense and organized, could protect that region of the dissected wall from subsequent expansion of the dissection or rupture. Moreover, alpha-smooth muscle actin positive cells appeared to be responsible for the newly produced collagen, which co-localized with significant production of glycosaminoglycans.