Single gene disorders of the aortic wall

Thoracic Aortic Aneurysm and Dissection: Review and Recommendations for Evaluation

ABSTRACT

Aortic dissection and rupture (collectively termed "sudden aortic death") are commonly encountered by forensic pathologists, with an estimated incidence at autopsy between 0.6% and 7.7%. Despite this, there is no standard of practice for the evaluation of sudden aortic death at autopsy.Recent studies have shown 20% of patients with thoracic aortic aneurysm or dissection (TAAD) have an identifiable genetic syndrome, and 19% will have an affected first-degree relative. The past 2 decades have seen identification of new culprit genes and syndromes, which can have subtle or nonexistent external phenotypes. A high index of suspicion is warranted to identify possible hereditary TAAD (H-TAAD), allowing family members to obtain screening to avoid catastrophic vascular events. Forensic pathologists need broad knowledge of the spectrum of H-TAAD and awareness of the relative significance of hypertension, pregnancy, substance use, and microscopic changes of aortic architecture.This article reviews the common subtypes of H-TAAD, including Marfan syndrome, vascular Ehlers-Danlos, Loeys-Dietz, and familial thoracic aortic aneurysm and dissection. Recommendations for the evaluation of sudden aortic death at autopsy are presented, including (1) performance of a complete autopsy, (2) documentation of aortic circumference and valve morphology, (3) notifying family of the need for screening, and (4) preservation of a sample for potential genetic testing.

Estimation of Selected Minerals in Aortic Aneurysms-Impaired Ratio of Zinc to Lead May Predispose?

The objective of this study was to estimate the content of copper, zinc, selenium, cadmium, and lead in the tissue of patients with aortic aneurysms. Molar ratio of Cu/Zn and antioxidant micronutrients to toxic elements was also calculated. A total of 108 patients: 47 with abdominal aortic aneurysm (AAA), 61 patients with thoracic aortic aneurysm (TAA), and a control group of 20 abdominal aortic (AA) and 20 thoracic aortic (TA) wall samples from the deceased were studied. The concentrations of mineral components in the tissue samples were determined by the AAS method. The average concentration of Cu in the aortic wall of patients with TAA was significantly lower than in the aortic wall samples of healthy people. The mean concentration of Zn in the aortic wall of patients with AAA and TAA was significantly lower than in the control group samples. Cu/Zn ratio was significantly higher in AAA patients than in control group which indicates a greater role of oxidative stress and inflammatory process in this type of aneurysm. The concentration of Se was significantly decreased in TAA patients compared with the control group; in turn, the concentration of Pb was increased in this group of patients. We observed significantly lower Cu/Pb ratio in TAA patients than in control group, whereas Zn/Pb ratio was significantly lower comparing with control samples in both types of aneurysms. In the examined aneurysms, we have shown the differences in concentrations of mineral components compared with the control tissues. The Zn concentration was decreased in both AAA and TAA samples. Impaired ratio of Zn to Pb may predispose to aortic aneurysms.

Myocardial Protection from Ischemia-Reperfusion Damage by the Antioxidant Effect of Hibiscus sabdariffa Linnaeus on Metabolic Syndrome Rats

Cardiovascular diseases (CVD) constitute one of the most prevalent health problems worldwide, being strongly associated with metabolic syndrome (MS). Oxidative stress (OS) is present in both CVD and MS. Infusions of Hibiscus sabdariffa Linnaeus (HSL) have antioxidant properties and could therefore decrease the presence of OS in these diseases. The aim of this study was to evaluate myocardial protection during ischemia/reperfusion due to the antioxidant effect of HSL infusion (3%) on a MS rat model induced by the administration of 30% sucrose in drinking water. We determined in control, MS, and MS + HSL rat hearts (n = 6 per group) cardiac mechanical performance (CMP), coronary vascular resistance (CVR), and activities of manganese and copper/zinc superoxide dismutases (Mn and Cu/Zn-SOD), peroxidases, glutathione peroxidase (GPx), catalase (CAT), glutathione s-transferase (GST), glutathione reductase (GR), and glutathione (GSH). We also determined lipoperoxidation (LPO), total antioxidant capacity (TAC), and the nitrate/nitrite ratio (NO₃⁻/NO₂⁻). The treatment with the HSL infusion restored the CMP (p = 0.01) and CVR (p = 0.04) and increased the Mn- (p = 0.02), Cu/Zn-SOD (p = 0.05), peroxidases (p = 0.04), GST (p = 0.02) activity, GHS (p = 0.02), TAC (p = 0.04), and NO₃⁻/NO₂⁻ (p = 0.01) and decreased the LPO (p = 0.02) in the heart of MS rats undergoing ischemia/reperfusion. The results suggest that the treatment with an infusion from HSL calices protects the cardiac function from damage by ischemia and reperfusion through the antioxidant activities of the substances it possesses. It favors antioxidant enzymatic activities and nonenzymatic antioxidant capacity.

Recommendations for genetic testing and counselling after sudden cardiac death: practical aspects for Swiss practice

There is a need to standardise, within a coordinated Swiss framework, the practical aspects of genetic testing and genetic counselling on possibly inherited cardiovascular disorders in relatives of a sudden cardiac death (SCD) victim. Because of the major advances in genetic investigation techniques and recent publication of international guidelines in the field of cardiology, genetics and pathology, we consider it important to summarise the current evidence and propose an optimal approach to post-mortem genetic investigation for SCD victims and their families in Switzerland. In this article, we discuss important technical, financial and medico-ethical aspects, and provide updated information on specific situations in which forensic pathologists, general practitioners and cardiologists should suspect a genetic origin of the SCD. At present, the principles of benefit, the duty to warn and the impact of genetic information for family members at risk are considered as strong justifications for post-mortem disclosure and prevail over the arguments of respect for a deceased person’s privacy and confidentiality. This paper underlines also the need to update and improve the general knowledge concerning the genetic risk of cardiovascular pathologies, the importance to perform an autopsy and post-mortem genetic testing in SCD victims, and to develop standardized post-mortem disclosure policy at national and international levels for SCD cases and relatives.

Application of induced pluripotent stem cells to model smooth muscle cell function in vascular diseases

Vascular smooth muscle cells (SMC) play an essential role in remodeling the vasculature during disease progression. Induced pluripotent stem cells (iPSC) provide an attractive approach to obtain autologous SMC source for patient-specific disease modeling. Here we discuss the current methods to 1) derive functional SMC from iPSC, 2) model vascular diseases using SMC generated from patient-derived iPSC, and 3) modulate microenvironmental cues to enhance cellular differentiation and functionality and better mimic the physiological environment. We emphasize that continuous exploration of biomaterial technologies to engineer a more SMC-specific microenvironment will provide further insight on complex vascular diseases.

Sudden aortic death-proposal for a comprehensive diagnostic approach in forensic and in clinical pathology practice

BACKGROUNDS

Aortic rupture or dissection as immediate cause of sudden death is encountered in forensic and clinical autopsy practice. Despite a common denominator of 'sudden aortic death' (SAD), we expect that in both settings the diagnostic workup, being either primarily legal or primarily disease related, differs substantially, which may affect the eventual diagnoses.

METHODS

We retrospectively reviewed case records of deceased persons who fitted a diagnosis of SAD in the continuous autopsy cohorts in a forensic (Suisse) and a clinical setting (The Netherlands). Clinical characteristics, data from post-mortem imaging, tissue blocks for histological analysis and results of ancillary studies were reviewed for its presence and outcome.

RESULTS

SAD was found in 7.7% in the forensic versus 2.2% in the clinical autopsies. In the forensic setting, autopsy was always combined with post-mortem imaging, showing variable outcome on detection of aortic disruption and/or pericardial bleeding. Histology of aorta was performed in 12/35 cases, mostly in the natural deaths. In the clinical setting, histology of the aorta was available in all cases, but post-mortem imaging in none. In both settings, underlying aortic disease was mostly cystic medial degeneration, atherosclerosis or a combination of both, with occasional rare unexpected diagnosis. Also in both, a genetic cause of aortic dissection was revealed in a minority (three cases).

CONCLUSION

Sudden aortic death (SAD) is more commonly encountered in a forensic than in a clinical setting. Major differences in the approach of SAD between these settings coincide with similarities in causes of death and underlying diseases. To ensure a correct diagnosis, we recommend that the investigation of SAD includes a study of the medical history, a full autopsy with histology of major organs including aorta, and storage of material for toxicological and genetic testing. Post-mortem radiological examination, useful for documentation and screening purposes, is feasible as non-invasive alternative when autopsy is not possible, but cannot substitute a full autopsy.

Vascular diseases: aortitis, aortic aneurysms, and vascular calcification

Inflammatory diseases of the aorta broadly include noninfectious and infectious aortitis, periaortitis, atherosclerosis, and inflammatory atherosclerotic aneurysms. Aortitis is uncommon but is increasingly recognized as an important cause of aortic aneurysms and dissections. Abdominal (AAA) and thoracic aortic aneurysms (TAA) have different pathologies and etiologies. AAAs are the most common type of aortic aneurysm, and the vast majority of these are atherosclerotic. The causes of TAA vary depending on the site of involvement, but medial degeneration is a common pathologic substrate, regardless of etiology, and genetic influences play a prominent role in TAA expression. Standardized classification schemes for inflammatory and degenerative diseases of the aorta have only recently been added to the pathology literature. A brief overview of the new histopathologic classifications for aortic inflammatory and degenerative diseases has recently been published by the Society for Cardiovascular Pathology and the Association for European Cardiovascular Pathology as a consensus document on the surgical pathology of the aorta. Vascular calcification is a highly regulated biologic process, and the mechanisms leading to vascular calcification are under investigation. Calcification may occur in the intima (atherosclerotic) or in the media secondary to metabolic disease. Rarely, vascular calcification may be associated with genetic disorders.

The Abdominal Aortic Aneurysm and Intraluminal Thrombus: Current Concepts of Development and Treatment

The pathogenesis of the abdominal aortic aneurysm (AAA) shows several hallmarks of atherosclerotic and atherothrombotic disease, but comprises an additional, predominant feature of proteolysis resulting in the degradation and destabilization of the aortic wall. This review aims to summarize the current knowledge on AAA development, involving the accumulation of neutrophils in the intraluminal thrombus and their central role in creating an oxidative and proteolytic environment. Particular focus is placed on the controversial role of heme oxygenase 1/carbon monoxide and nitric oxide synthase/peroxynitrite, which may exert both protective and damaging effects in the development of the aneurysm. Treatment indications as well as surgical and pharmacological options for AAA therapy are discussed in light of recent reports.

Applications of nuclear reprogramming and directed differentiation in vascular regenerative medicine

As vertebrates proceed through embryonic development the growing organism cannot survive on diffusion of oxygen and nutrients alone and establishment of vascular system is fundamental for embryonic development to proceed. Dysfunction of the vascular system in adults is at the heart of many disease states such as hypertension and atherosclerosis. In this review we will focus on attempts to generate the key cells of the vascular system, the endothelial and smooth muscle cells, using human embryonic stem cells (hESCs) and human induced pluripotent stem cells (iPSCs). Regardless of their origin, be it embryonic or via somatic cell reprogramming, pluripotent stem cells provide limitlessly self-renewing populations of material suitable for the generation of multi-lineage isogenic vascular cells-types that can be used as tools to study normal cell and tissue biology, model disease states and also as tools for drug screening and future cell therapies.

Analysis of oxidative stress enzymes and structural and functional proteins on human aortic tissue from different aortopathies

The role of oxidative stress in different aortopathies is evaluated. Thirty-two tissue samples from 18 men and 14 women were divided into: 4 control (C) subjects, 11 patients with systemic arterial hypertension (SAH), 4 with variants of Marfan's syndrome (MV), 9 with Marfan's syndrome (M), 2 with Turner's syndrome, and 2 with Takayasu's arteritis (TA). Aorta fragments were homogenized. Lipoperoxidation (LPO), copper-zinc and manganese superoxide dismutase (Mn and Cu-Zn-SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione S-transferase (GST), endothelial nitric oxide synthase (eNOS), nitrates and nitrites (NO3(-)/NO2(-)), and type IV collagen, and laminin were evaluated. There was an increase in Mn- and Cu-Zn-SOD activity in SAH, MV, M, and Turner's syndrome. There was also an increase in CAT activity in M and Turner' syndrome. GPx and GST activity decreased and LPO increased in all groups. eNOS was decreased in SAH, MV, and M and NO3 (-)/NO2 (-) were increased in SAH and TA. Type IV collagen was decreased in Turner's syndrome and TA. Laminin γ-1 was decreased in MV and increased in M. In conclusion, similarities and differences in oxidative stress in the different aortopathies studied including pathologies with aneurysms were found with alterations in SOD, CAT, GPx, GST, and eNOS activity that modify subendothelial basement membrane proteins.

New population-based exome data question the pathogenicity of some genetic variants previously associated with Marfan syndrome

Background

Marfan syndrome (MFS) is a rare autosomal dominantly inherited connective tissue disorder with an estimated prevalence of 1:5,000. More than 1000 variants have been previously reported to be associated with MFS. However, the disease-causing effect of these variants may be questionable as many of the original studies used low number of controls. To study whether there are possible false-positive variants associated with MFS, four in silico prediction tools (SIFT, Polyphen-2, Grantham score, and conservation across species) were used to predict the pathogenicity of these variant.

Results

Twenty-three out of 891 previously MFS-associated variants were identified in the ESP. These variants were distributed on 100 heterozygote carriers in 6494 screened individuals. This corresponds to a genotype prevalence of 1:65 for MFS. Using a more conservative approach (cutoff value of >2 carriers in the EPS), 10 variants affected a total of 82 individuals. This gives a genotype prevalence of 1:79 (82:6494) in the ESP. A significantly higher frequency of MFS-associated variants not present in the ESP were predicted to be pathogenic with the agreement of ≥3 prediction tools, compared to the variants present in the ESP (p = 3.5 × 10⁻¹⁵).

Conclusions

This study showed a higher genotype prevalence of MFS than expected from the phenotype prevalence in the general population. The high genotype prevalence suggests that these variants are not the monogenic cause of MFS. Therefore, caution should be taken with regard to disease stratification based on these previously reported MFS-associated variants.

Current evidence and insights about genetics in thoracic aorta disease

Thoracic aortic aneurysms have been historically considered to be caused by etiologic factors similar to those implied in abdominal aortic aneurysms. However, during the past decade, there has been increasing evidence that almost 20% of thoracic aortic aneurysms may be associated with a genetic disease, often within a syndromic or familial disorder. Moreover, the presence of congenital anomalies, such as bicuspid aortic valve, may have a unique common genetic underlying cause. Finally, also sporadic forms have been found to be potentially associated with genetic disorders, as highlighted by the analysis of rare variants and expression of specific microRNAs. We therefore sought to perform a comprehensive review of the role of genetic causes in the development of thoracic aortic aneurysms, by analyzing in detail the current evidence of genetic alterations in syndromes such as Marfan, Loeys-Dietz, and Ehler-Danlos, familial or sporadic forms, or forms associated with bicuspid aortic valve.

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.

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.

Pathology of the Aorta

The aorta is a distinctive surgical pathology specimen removed most frequently for aneurysm or dissection. Genetic syndromes, inflammatory processes and acquired diseases of aging result in aortic pathology; these are presented in terms of pathology, differential diagnosis and classification schemes. The pathologic context of a variety of commonly encountered histopathologies is described.