Human Aortic Wall Research Articles

Functional features of smooth muscle cells of the human aortic wall and their role in the pathogenesis of aneurysms

BACKGROUND: Thoracic aortic aneurysm is a chronic disease characterized by localized dilation of the vessel, including the ascending, arch and descending parts of the aorta. Aneurysm is the most dangerous disease because aortic dissection or rupture can lead to sudden death. More than 150,000 people worldwide die from aortic aneurysms every year. Despite the prevalence of this disease, the cellular mechanisms of its development remain not fully understood. AIM: evaluation of phagocytic activity and the ability to proinflammatory activation of smooth muscle cells isolated from Tunica intima and Tunica media of the thoracic part of the human aorta in patients with aneurysm. METHODS: The experiments were performed on a culture of primary smooth muscle cells (SMC) isolated from aneurysm patients, linear cultures (mesenchymal stem cells ASC52telo, fibroblasts 977hTERT, THP-1, CLTH-CL05008 and EA.hy926) and SMC isolated from healthy donors were used as controls. Phagocytic activity was studied by adding latex beads to the studied cells, the ability to internalize LDL was evaluated using the dye BDP 630/650 (Lumiprobe, Russia) and a biochemical method, the assessment of the ability to pro- and anti-inflammatory activation was studied using enzyme-linked immunosorbent assay (ELISA), during which the amount of secreted cytokines was measured: IL-8, IL-6 and IL-10. RESULTS: It has been shown that the studied cells have high phagocytic activity and the ability to internalize LDL. Thus, primary SMC from Tunica media have greater phagocytic activity than SMC obtained from healthy donors (p 0.001). In addition, IL-6 secretion after incubation with latex beads was significantly higher in SMC from Tunica media, compared with SMC from healthy donors (p 0.001). Also, IL-6 secretion after incubation with LDL was higher in SMC from Tunica intima, compared with SMC from healthy donors (p 0.001). CONCLUSION: Thus, the absorption of latex beads and LDL stimulates the secretion of proinflammatory IL-6 by primary SMC from Tunica intima and SMC from Tunica media, which are part of the aortic wall of patients with aneurysm.

Poisson function and volume ratio of soft anisotropic materials under large deformations

Accurate transverse deformation measurements are required for the estimation of the Poisson function and volume ratio. In this study, pure silicone and soft composite specimens were subjected to uniaxial tension, and the digital image correlation method was used to measure longitudinal and in- and out-of-plane transverse stretches. To minimize the effects of measurement errors on parameter estimation, the measured transverse stretches were defined in terms of the longitudinal stretch using a new formulation based on Poisson's ratios and two stretch-dependent parameters. From this formulation, Poisson functions and volume ratio for soft materials under large deformations were obtained. The results showed that pure silicone can be considered isotropic and nearly incompressible under large deformations, as expected. In contrast, Poisson's ratio of silicone reinforced with extensible fabric can exceed classical bounds, including negative value (auxetic behavior). The incompressibility assumption can be employed for describing the stress-stretch curve of pure silicone, while volume ratios are required for soft composites. Data of human skin, aortic wall, and annulus fibrosus from the literature were selected and analyzed. Except for the aortic wall, which can be considered nearly incompressible, the studied soft tissues must be regarded as compressible. All tissues presented anisotropic behavior.

Fabrication of Soft Transparent Patient-Specific Vascular Models with Stereolithographic 3D printing and Thiol-Based Photopolymerizable Coatings.

An ideal vascular phantom should be anatomically accurate, have mechanical properties as close as possible to the tissue, and be sufficiently transparent for ease of visualization. However, materials that enable the convergence of these characteristics have remained elusive. The fabrication of patient-specific vascular phantoms with high anatomical fidelity, optical transparency, and mechanical properties close to those of vascular tissue is reported. These final properties are achieved by 3D printing patient-specific vascular models with commercial elastomeric acrylic-based resins before coating them with thiol-based photopolymerizable resins. Ternary thiol-ene-acrylate chemistry is found optimal. A PETMP/allyl glycerol ether (AGE)/polyethylene glycol diacrylate (PEGDA) coating with a 30/70% AGE/PEGDA ratio applied on a flexible resin yielded elastic modulus, UTS, and elongation of 3.41MPa, 1.76 MPa, and 63.2%, respectively, in range with the human aortic wall. The PETMP/AGE/PEGDA coating doubled the optical transmission from 40% to 80%, approaching 88% of the benchmark silicone-based elastomer. Higher transparency correlates with a decrease in surface roughness from 2000 to 90nm after coating. Coated 3D-printed anatomical replicas are showcased for pre-procedural planning and medical training with good radio-opacity and echogenicity. Thiol-click chemistry coatings, as a surface treatment for elastomeric stereolithographic 3D-printed objects, address inherent limitations of photopolymer-based additive manufacturing.

Global and local stiffening of ex vivo-perfused stented human thoracic aortas: A mock circulation study.

The effects of thoracic endovascular repair (TEVAR) on the biomechanical properties of aortic tissue have not been adequately studied. Understanding these features is important for the management of endograft-triggered complications of a biomechanical nature. This study aims to examine how stent-graft implantation affects the elastomechanical behavior of the aorta. Non-pathological human thoracic aortas (n=10) were subjected to long-standing perfusion (8h) within a mock circulation loop under physiological conditions. To quantify compliance and its mismatch in the test periods without and with a stent, the aortic pressure and the proximal cyclic circumferential displacement were measured. After perfusion, biaxial tension tests (stress-stretch) were carried out to examine the stiffness profiles between non-stented and stented tissue, followed by a histological assessment. Experimental evidence shows: (i) a significant reduction in aortic distensibility after TEVAR, indicating aortic stiffening and compliance mismatch, (ii) a stiffer behavior of the stented samples compared to the non-stented samples with an earlier entry into the nonlinear part of the stress-stretch curve and (iii) strut-induced histological remodeling of the aortic wall. The biomechanical and histological comparison of the non-stented and stented aortas provides new insights into the interaction between the stent-graft and the aortic wall. The knowledge gained could refine the stent-graft design to minimize the stent-induced impacts on the aortic wall and the resulting complications. STATEMENT OF SIGNIFICANCE: Stent-related cardiovascular complications occur the moment the stent-graft expands on the human aortic wall. Clinicians base their diagnosis on the anatomical morphology of CT scans while neglecting the endograft-triggered biomechanical events that compromise aortic compliance and wall mechanotransduction. Experimental replication of endovascular repair in cadaver aortas within a mock circulation loop may have a catalytic effect on biomechanical and histological findings without an ethical barrier. Demonstrating interactions between the stent and the wall can help clinicians make a broader diagnosis such as ECG-triggered oversizing and stent-graft characteristics based on patient-specific anatomical location and age. In addition, the results can be used to optimize towards more aortophilic stent grafts.

Construction of a Human Aorta Smooth Muscle Cell Organ-On-A-Chip Model for Recapitulating Biomechanical Strain in the Aortic Wall.

Conventional two-dimensional cell culture techniques and animal models have been used in the study of human thoracic aortic aneurysm and dissection (TAAD). However, human TAAD sometimes cannot be characterized by animal models. There is an apparent species gap between clinical human studies and animal experiments that may hinder the discovery of therapeutic drugs. In contrast, the conventional cell culture model is unable to simulate in vivo biomechanical stimuli. To this end, microfabrication and microfluidic techniques have developed greatly in recent years, providing novel techniques for establishing organoids-on-a-chip models that replicate the biomechanical microenvironment. In this study, a human aorta smooth muscle cell organ-on-a-chip (HASMC-OOC) model was developed to simulate the pathophysiological parameters of aortic biomechanics, including the amplitude and frequency of cyclic strain experienced by human aortic smooth muscle cells (HASMCs) that play a vital role in TAAD. In this model, the morphology of HASMCs became elongated in shape, aligned perpendicularly to the strain direction, and presented a more contractile phenotype under strain conditions than under static conventional conditions. This was consistent with the cell orientation and phenotype in native human aortic walls. Additionally, using bicuspid aortic valve-related TAAD (BAV-TAAD) and tricuspid aortic valve-related TAAD (TAV-TAAD) patient-derived primary HASMCs, we established BAV-TAAD and TAV-TAAD disease models, which replicate HASMC characteristics in TAAD. The HASMC-OOC model provides a novel in vitro platform that is complementary to animal models for further exploring the pathogenesis of TAAD and discovering therapeutic targets.

Time-course of the human thoracic aorta ageing process assessed using uniaxial mechanical testing and constitutive modelling

Age-related remodelling of the arterial wall shifts the load bearing from the compliant elastin network to the stiffer collagen fibres. While this phenomenon has been widely investigated in animal models, human studies are lacking due to shortage of donors’ arteries. This work aimed to characterise the effect of ageing on the mechanical properties of the human aortic wall in the circumferential direction.N = 127 thoracic aortic rings (age 18–81 years) were subjected to circumferential tensile testing. The tangential elastic modulus (Kθθθθ) was calculated at pressure-equivalent stresses ranging 60–100 mmHg. Further, the mechanical data were fitted using the Holzpafel-Gasser-Ogden hyperelastic strain energy function (HGO-SEF), modelling the superimposed response of an isotropic matrix (elastin) reinforced by collagen fibres.Kθθθθ increased with age across at all considered pressures (p < 0.001), although more strongly at higher pressures. Indeed, the slope of the linear Kθθθθ-pressure relationship increased by 300% from donors <30 to ≥70 years (4.72± 2.95 to 19.06± 6.82 kPa/mmHg, p < 0.001). The HGO-SEF elastin stiffness-like parameter dropped by 31% between 30 and 40 years (p < 0.05) with non-significant changes thereafter. Conversely, changes in HGO-SEF collagen parameters were observed later at age>60 years, with the exponential constant increasing by ∼20–50 times in the investigated age range (p < 0.001).The results provided evidence that the human thoracic aorta undergoes stiffening during its life-course. Constitutive modelling suggested that these changes in arterial mechanics are related to the different degeneration time-courses of elastin and collagen; likely due to considerable fragmentation of elastin first, with the load bearing shifting from the compliant elastin to the stiffer collagen fibres. This process leads to a gradual impairment of the aortic elastic function with age.

Dissecting the Heterogeneity of Human Thoracic Aortic Aneurysms Using Single-Cell Transcriptomics.

Thoracic aortic aneurysm is a life-threatening condition caused by weakening of the thoracic aorta wall, often developing silently until dissection or rupture occurs. Despite substantial efforts in the past decade, there have been no significant therapeutic advances to prevent or clinically manage diverse forms of thoracic aortic aneurysm and dissection with the only effective treatment being surgical repair. There is an urgent need to understand intra- and inter-aneurysmal heterogeneity underlying thoracic aortic aneurysm and dissection pathogenesis. The human aortic wall consists of many cell types and exhibits significant regional heterogeneity. High-throughput single-cell RNA sequencing has emerged as the principal tool to reveal the complexity in human tissues and clinical specimens. Recent single-cell RNA sequencing studies of different aortic cell populations both in vivo and in vitro began to dissect this complexity and have provided valuable information. In this review, we summarize these findings and discuss the potential applications of single-cell transcriptomics and related high-content technologies in human thoracic aortic aneurysm and dissection research, as well as the challenges associated with it.

Characteristic distribution of eicosapentaenoic acid in human abdominal aortic aneurysm wall

Abdominal aortic aneurysm (AAA) is a vascular disease in which the abdominal aorta gradually dilates. Dilation of AAA is associated with the aortic wall weakness induced by chronic inflammation (1). Several epidemiologic studies reported that consumption of fish is associated with the prevention of AAA. Animal and human studies suggested n-3 PUFAs can protect against AAA development and rupture. These previous data provide evidence to suggest the suppressive effect of n-3 PUFAs on AAA, which has no pharmaceuticals; however, the distribution of n-3 PUFAs in the aorta is a “missing link” to understand mechanisms underlying suppressive effects of them.

An ultrastructural 3D reconstruction method for observing the arrangement of collagen fibrils and proteoglycans in the human aortic wall under mechanical load

An insight into changes of soft biological tissue ultrastructures under loading conditions is essential to understand their response to mechanical stimuli. Therefore, this study offers an approach to investigate the arrangement of collagen fibrils and proteoglycans (PGs), which are located within the mechanically loaded aortic wall. The human aortic samples were either fixed directly with glutaraldehyde in the load-free state or subjected to a planar biaxial extension test prior to fixation. The aortic ultrastructure was recorded using electron tomography. Collagen fibrils and PGs were segmented using convolutional neural networks, particularly the ESPNet model. The 3D ultrastructural reconstructions revealed a complex organization of collagen fibrils and PGs. In particular, we observed that not all PGs are attached to the collagen fibrils, but some fill the spaces between the fibrils with a clear distance to the collagen. The complex organization cannot be fully captured or can be severely misinterpreted in 2D. The approach developed opens up practical possibilities, including the quantification of the spatial relationship between collagen fibrils and PGs as a function of the mechanical load. Such quantification can also be used to compare tissues under different conditions, e.g., healthy and diseased, to improve or develop new material models. Statement of significanceThe developed approach enables the 3D reconstruction of collagen fibrils and proteoglycans as they are embedded in the loaded human aortic wall. This methodological pipeline comprises the knowledge of arterial mechanics, imaging with transmission electron microscopy and electron tomography, segmentation of 3D image data sets with convolutional neural networks and finally offers a unique insight into the ultrastructural changes in the aortic tissue caused by mechanical stimuli.

Parallel Murine and Human Aortic Wall Genomics Reveals Metabolic Reprogramming as Key Driver of Abdominal Aortic Aneurysm Progression.

BackgroundWhile numerous interventions effectively interfered with abdominal aortic aneurysm (AAA) formation/progression in preclinical models, none of the successes translated into clinical success. Hence, a systematic exploration of parallel and divergent processes in clinical AAA disease and its 2 primary models (the porcine pancreatic elastase and angiotensin‐II infusion [AngII] murine model) was performed to identify mechanisms relevant for aneurysm disease.Methods and ResultsThis study combines Movat staining and pathway analysis for histological and genomic comparisons between clinical disease and its models. The impact of a notable genomic signal for metabolic reprogramming was tested in a rescue trial (AngII model) evaluating the impact of 1‐(4‐pyridinyl)‐3‐(2‐quinolinyl)‐2‐propen‐1‐one (PFK15)‐mediated interference with main glycolytic switch PFKFB3. Histological evaluation characterized the AngII model as a dissection model that is accompanied by adventitial fibrosis. The porcine pancreatic elastase model showed a transient inflammatory response and aortic dilatation, followed by stabilization and fibrosis. Normalization of the genomic responses at day 14 confirmed the self‐limiting nature of the porcine pancreatic elastase model. Clear parallel genomic responses with activated adaptive immune responses, and particularly strong signals for metabolic switching were observed in human AAA and the AngII model. Rescue intervention with the glycolysis inhibitor PFK15 in the AngII model showed that interference with the glycolytic switching quenches aneurysm formation.ConclusionsDespite clear morphological contrasts, remarkable genomic parallels exist for clinical AAA disease and the AngII model. The metabolic response appears causatively involved in AAA progression and provides a novel therapeutic target. The clear transient genomic response classifies the porcine pancreatic elastase model as a disease initiation model.

Engineering a Human Pluripotent Stem Cell-Based in vitro Microphysiological System for Studying the Metformin Response in Aortic Smooth Muscle Cells.

Aortic aneurysm is a common cardiovascular disease characterised by continuous dilation of the aorta, and this disease places a heavy burden on healthcare worldwide. Few drugs have been suggested to be effective in controlling the progression of aortic aneurysms. Preclinical drug responses from traditional cell culture and animals are usually controversial. An effective in vitro model is of great demand for successful drug screening. In this study, we induced an in vitro microphysiological system to test metformin, which is a potential drug for the treatment of aortic aneurysms. Human pluripotent stem cell-derived aortic smooth muscle cells (hPSC-HASMCs) were cultured on an in vitro microphysiological system, which could replicate the cyclic stretch of the human native aortic wall. By using this system, we found that HASMCs were more likely to present a physiologically contractile phenotype compared to static cell cultures. Moreover, we used hPSC-HASMCs in our microphysiological system to perform metformin drug screening. The results showed that hPSC-HASMCs presented a more contractile phenotype via NOTCH 1 signalling while being treated with metformin. This result indicated that metformin could be utilised to rescue hPSC-HASMCs from phenotype switching during aortic aneurysm progression. This study helps to elucidate potential drug targets for the treatment of aortic aneurysms.

Influence of atherosclerosis on anisotropy and incompressibility of the human thoracic aortic wall

In this study, we analysed the influence of atherosclerosis on the anisotropic and incompressible behaviour of the human thoracic aortic wall under mechanical loads.The mechanical tests involved preparations of the human thoracic aortic wall, which were evaluated based on the six-stage histological classification of atherosclerosis proposed by Stary. Anisotropy was evaluated on the basis of directional tests of mechanical properties, which were determined based on a uniaxial tensile test conducted in two directions, i.e. longitudinal and circumferential. The evaluation of incompressibility was carried out based on the product of the stretch ratios obtained in the x–y and y–z planes and on the basis of Poisson’s ratio. The results presented in this study indicate that the blood vessel wall is an anisotropic material only in the case of normal vessels and in early atherosclerotic lesions. Atherosclerosis progression causes a gradual loss of the anisotropic character of the work of the thoracic aortic wall in moderate and very advanced stages of atherosclerosis under mechanical loads. The results show that the wall of the thoracic aorta is an incompressible material. Development of atherosclerosis does not cause a loss of incompressibility of the thoracic aorta. This study is the only one so far that presents changes in the mechanical properties at all stages of atherosclerotic development. A large number of preparations were included in the study, which is important for the results obtained due to the multi-factorial etiology of atherosclerosis development.

Fat-Soluble Vitamins Affect Composition of Extracellular Matrix Deposited by Human Aortic Smooth Muscle and Endothelial Cells In Vitro

Atherosclerotic cardiovascular disease is accompanied by changes in arterial connective tissue. We evaluated the effects of fat-soluble vitamins A, D, and E individually and in combinations on the composition of extracellular matrix produced and deposited by arterial wall cells, human aortic smooth muscle cells, and endothelial cells. Individually, vitamins D and E stimulated collagen type I extracellular matrix deposition in human aortic smooth muscle cell cultures. However, vitamins A, D, and E reduced collagen type IV deposition by human aortic smooth muscle cell, counteracting the stimulatory effects of vitamin C. The extracellular matrix deposition of heparan sulfate by human aortic smooth muscle cells increased by vitamin C and its combination (C+D+E). β-carotene + D + C induced the extracellular matrix deposition of collagen I by endothelial cells. Vitamin E with other vitamins resulted in either induction (E+C+A) or inhibition (E+D). The extracellular matrix deposition of type IV collagen and elastin by human aortic endothelial cells was not affected by test vitamins, except the extracellular matrix type IV collagen decrease by combinations (A+E), (A+D+E), and (C+D+E). The extracellular matrix deposition of all tested glycosaminoglycans was reduced by vitamin A and its combination (A+C+D+E). Therefore, the fat-soluble vitamins applied individually or in combination—both with each other or with ascorbic acid—can affect extracellular matrix deposition of type I and IV collagens, and key glycosaminoglycans by cultured human aortic arterial wall cells.

Finite element simulation of three dimensional residual stress in the aortic wall using an anisotropic tissue growth model

Residual stress is believed to play a significant role in the in vivo stress state of the arterial wall, but quantifying residual stress in vivo is challenging. Based on the well-known assumptions that residual stress is a result of heterogeneous arterial growth and that it homogenizes the transmural distribution of arterial wall stress, we propose a new anisotropic tissue growth model for the aorta to recover the three-dimensional residual stress field in a bi-layer human aortic wall. Finite element simulations showed that the predicted residual stress magnitude with this method are within the documented range for human aorta. Particularly, the homeostatic inter-layer stress difference is identified as a key parameter to quantify the opening angle. To the authors’ knowledge, this is the first finite element study employing anisotropic growth of aortic tissue in a bi-layer model to generate three-dimensional residual stress field, and the resultant opening angle can match with the experiments. A parametric study found that inter-layer stress homogeneity, arterial blood pressure, axial pre-stretch, and material stiffness strongly affect the residual stress field.

Mechanical Characterization of the Lamellar Structure of Human Abdominal Aorta in the Development of Atherosclerosis: An Atomic Force Microscopy Study.

Atherosclerosis is a major risk factor for cardiovascular disease. However, mechanisms of interaction of atherosclerotic plaque development and local stiffness of the lamellar structure of the arterial wall are not well established. In the current study, the local Young's modulus of the wall and plaque components were determined for three different groups of healthy, mildly diseased and advanced atherosclerotic human abdominal aortas. Histological staining was performed to highlight the atherosclerotic plaque components and lamellar structure of the aortic media, consisting of concentric layers of elastin and interlamellar zones. The force spectroscopy mode of the atomic force microscopy was utilized to determine Young's moduli of aortic wall lamellae and plaque components at the micron level. The high variability of Young's moduli (E) at different locations of the atherosclerotic plaque such as the fibrous cap (E=15.5± 2.6kPa), calcification zone (E=103.7±19.5kPa), and lipid pool (E=3.5±1.2kPa) were observed. Reduction of elastin lamellae stiffness (18.6%), as well as stiffening of interlamellar zones (50%), were detected in the diseased portion of the medial layer of abdominal aortic wall compared to the healthy artery. Additionally, significant differences in the stiffness of both elastin lamellae and interlamellar zones were observed between the diseased wall and disease-free wall in incomplete plaques. Our results elucidate the alternation of the stiffness of different lamellae in the human abdominal aortic wall with atherosclerotic plaque development and may provide new insight on the remodeling of the aortic wall during the progression of atherosclerosis.

Structural and crystal-chemical characteristics of the apatite deposits from human aortic walls.

Thermal behavior of biological apatite is the object of several studies. Crystal size, carbonate content, phase composition, and other parameters change during annealing up to 900 °C in biological minerals with apatite structure. The way these parameters change reflects the specific properties of the initial bioapatite. This work presents data on thermal transformations of pathological bioapatite from the human cardiovascular system, namely aortic wall deposits. Some minor elements, foreign to calcium hydroxyapatite (e.g., Na and Mg), can be both incorporated in the apatite structure and localized in the surface layers of crystals, modifying functions of the mineral. A new approach was proposed to determine the predominant location of minor elements, such as Mg, Na, and K, in the mineral of pathological deposits. Mg and Na in pathological apatite can be in both structurally bound (substituting calcium in lattice) and labile (localized on the crystal surface) states, while K is not able to join the apatite structure in significant amount or be chemically bound to it. This approach, based on atomic spectrometry, can be used effectively in combination with a set of traditional techniques, such as like EDS, IRS, and XRD.

Abstract 24034: MFG-E8 Fragment Medin and Arterial Aging

Background: Aging increases milk fat globule EGF-VIII (MFG-E8) expression in the rat, nonhuman primate and human aortic walls, facilitating the invasion, proliferation, and proinflammation of vascular smooth muscle cells (VSMCs). The MFG-E8 C-terminal fragment medin has been reported to be involved in the necrosis of VSMCs at the inflammatory sites of aortic dissection, however, its cleavage processes, aortic wall levels with aging and bio-role in VSMCs remains to be determined. Material and Methods: In this study, immunofluorescence, immunohistochemistry and western blot analysis demonstrate that MFG-E8 and its fragment medin ( Figure ), activated matrix metalloproteinase type II (MMP-2) and platelet derived growth factor receptor type-beta (PDGFR-β) protein levels were markedly increased in human grossly normal aortic walls from old (n=10, &gt;50 yrs) vs. younger donors (n=10, &lt;25 yrs). Importantly, exposure of medin peptide (20 to100nM) to primary cultured VSMCs isolated from young (8 mo) and old (30 mo) FXBN rat aortae significantly increased MMP-2 activation, PDGFR-β expression, and migratory capacity measured by a modified Boyden chamber in a dose-dependent manner in both also. Separate exposure of activated MMP-2 to recombinant human MFG-E8 protein and also to MFG-E8 enriched old human aortic protein markedly increased the cleavage product medin in both, which was substantially inhibited by an MMP inhibitor, GM6001. Exposure of medin to VSMCs did not significantly affect the expression of cell cycle related proteins. In addition, PDGF-BB treatment markedly activated MMP-2 in both young and old VSMCs, which was substantially reduced by a PDGFR-β inhibitor, RTK. Conclusion: Taken together, targeting MFG-E8 or its cleavage product medin is a novel approach to the prevention or treatment of large arterial aging or age-associated disease.

Abstract 490: Quantitative and Dynamic Measurements of Aortic Wall of Acute Type-A Aortic Dissection With X-Ray Phase-Contrast Tomography

Objectives: We previously reported excellent findings of X-ray phase-contrast tomography (PCX) for visualization of the formalin-fixed human aortic wall samples, and PCX enabled to demonstrate changes of tunica media in acute type A aortic dissection (AADA) . This study evaluates quantitative and dynamic measurements of fresh aortic wall samples of AADA with this modality. Methods: Fresh human aortic samples of the ascending aorta (n=7) were obtained during emergent aortic repair for AADA. Formalin-fixed human aortic walls of AADA (n=15) and normal aorta (n=15) were also investigated. PCX is approximately 1000 times more sensitive than absorption-contrast X-ray imaging and effective resolution of PCX is 11.7 μm. Quantitative and dynamic measurement has been developed to visualize changes in imaging of fresh aortic wall under various tensile force to simulate physiological condition, in which aortic wall is stretched according to blood pressure. Results: In normal aorta, quantitative measurement of density of the media was 1.095±0.003(g/cm3), and no different between intimal side (1.083±0.002) and adventitial side (1.085±0.003). On contrast, in formalin-fixed aorta of AADA, the medial density was 1.063±0.027, significantly lower than normal aorta (Figure-1), and different between intimal side and adventitial side (1.061±0.008 vs 1.081±0.011, respectively; p&lt;0.005). In fresh sample of AADA, distribution of the medial density was equal to that of formalin-fixed aorta and differences of the medial density were clearly observed with elevation of tensile force of the aortic wall (Figure-1). These differences in density within tunica media were well correlated with distribution of elastic fibers and existence of cystic medial necrosis in pathological analysis. Conclusions: X-ray phase-contrast tomography was a strong modality to understand aortic structures and pathogenesis of acute type A aortic dissection.

The crosstalk between vascular MSCs and inflammatory mediators determines the pro-calcific remodelling of human atherosclerotic aneurysm

BackgroundHuman mesenchymal stem cells (MSCs) possess well-known reparative abilities, but any defect of the immunomodulatory activity and/or the differentiation process may determine the development of human diseases, including those affecting the vascular wall. MSCs residing within the human aortic wall represent a potential cell mediator of atherosclerotic aneurysm development.MethodsMSCs isolated from healthy and aneurysm aortas were characterized by flow cytometer and tested for differentiation properties. Healthy aorta (ha)-MSCs were then subjected to inflammatory stimuli to evaluate the microenvironmental impact on their function and involvement in vascular remodelling.ResultsAbdominal aortic aneurysm (AAA)-MSCs were isolated from calcified and inflamed aortas of 12 patients with high serum levels of MMP-9 protein. AAA-MSCs expressed typical mesenchymal markers and, in line with the histological analysis, elevated levels of OPN, an osteogenic marker also involved in vascular remodelling. AAA-MSCs were highly osteogenic and underwent intense calcium deposition under proper stimulation; moreover, AAA-MSCs were able to differentiate into tubule-like structures in Matrigel, even if the lack of CD146 and the reduced structural stability suggested an inefficient maturation process. We further demonstrated an association between osteogenesis and inflammation; indeed, ha-MSCs cultured with either cytokines (TNF-α, IL-1β) or AAA-PBMCs showed increased expression of MMP-9 and osteogenic markers, to the detriment of the adipogenic regulator PPAR-γ. Interestingly, the culture with inflammatory cells highly stimulated ha-MSCs towards the osteogenic commitment.ConclusionsAAA-MSCs displayed high osteogenic potential and pathological angiogenesis that represent crucial steps for AAA progression; we showed that the inflammatory process critically addresses human vascular MSCs towards a pathological behaviour, inducing vascular bone matrix deposition and remodelling. Inhibition of this pathway may represent a pharmacological approach against arterial calcification.

Cryopreserved human aortic root allografts arterial wall: Structural changes occurring during thawing.

BackgroundThe aim of our experimental work was to assess morphological changes of arterial wall that arise during different thawing protocols of a cryopreserved human aortic root allograft (CHARA) arterial wall.MethodsThe experiment was performed on CHARAs. Two thawing protocols were tested: 1, CHARAs were thawed at a room temperature at +23°C; 2, CHARAs were placed directly into a water bath at +37°C.Microscopic samples preparationAfter fixation, all samples were washed in distilled water for 5 min, and dehydrated in a graded ethanol series (70, 85, 95, and 100%) for 5 min at each level. The tissue samples were then immersed in 100% hexamethyldisilazane for 10 minutes and air dried in an exhaust hood at room temperature. Processed samples were mounted on stainless steel stubs, coated with gold.ResultsThawing protocol 1: All 6 (100%) samples showed loss of the endothelium and damage to the subendothelial layers with randomly dispersed circular defects and micro-fractures without smooth muscle cells contractions in the tunica media.Thawing protocol 2: All 6 (100%) samples showed loss of endothelium from the luminal surface, longitudinal corrugations in the direction of blood flow caused by smooth muscle cells contractions in the tunica media with frequent fractures in the subendothelial layerConclusionAll the samples thawed at the room temperature showed smaller structural damage to the CHARA arterial wall with no smooth muscle cell contraction in tunica media when compared to the samples thawed in a water bath.