Aortic Arch Tissue Research Articles

Embryonic aortic arch material properties obtained by optical coherence tomography-guided micropipette aspiration

It is challenging to determine the in vivo material properties of a very soft, mesoscale arterial vesselsof size ∼ 80 to 120 μm diameter. This information is essential to understand the early embryonic cardiovascular development featuring rapidly evolving dynamic microstructure. Previous research efforts to describe the properties of the embryonic great vessels are very limited. Our objective is to measure the local material properties of pharyngeal aortic arch tissue of the chick-embryo during the early Hamburger-Hamilton (HH) stages, HH18 and HH24. Integrating the micropipette aspiration technique with optical coherence tomography (OCT) imaging, a clear vision of the aspirated arch geometry is achieved for an inner pipette radius of Rp = 25 μm. The aspiration of this region is performed through a calibrated negatively pressurized micro-pipette. A computational finite element model is developed to model the nonlinear behaviour of the arch structure by considering the geometry-dependent constraints. Numerical estimations of the nonlinear material parameters for aortic arch samples are presented. The exponential material nonlinearity parameter (a) of aortic arch tissue increases statistically significantly from a = 0.068 ± 0.013 at HH18 to a = 0.260 ± 0.014 at HH24 (p = 0.0286). As such, the aspirated tissue length decreases from 53 μm at HH18 to 34 μm at HH24. The calculated NeoHookean shear modulus increases from 51 Pa at HH18 to 93 Pa at HH24 which indicates a statistically significant stiffness increase. These changes are due to the dynamic changes of collagen and elastin content in the media layer of the vessel during development.

Abstract 11748: Prophylactic Aortic Arch Replacement in Patients With Loeys-Dietz Syndrome: Surgical Outcomes and Molecular Rationale

Introduction: Loeys-Dietz syndrome (LDS) patients typically develop focal aortic root aneurysm but have substantial risk of distal aortic events (arch aneurysm and type B dissection) after root replacement. We offer prophylactic arch replacement to LDS patients of all genotypes undergoing elective valve-sparing aortic root replacement (VSARR) to prevent late aortic events. We hypothesized that non-dilated LDS aortic arch tissue demonstrates ongoing deterioration at the time of VSARR. Methods: Aortic tissue was anatomically segmented (root, ascending, arch) then examined via histology and single-cell RNA sequencing (‘scRNAseq’, n=4 patients) to comprehensively profile cellular phenotypes. Results: LDS patients (n=8, mean age 37.9 years, 87.5% male) had root aneurysm (mean 45.1 ± 8.9mm) without ascending (35.1± 7.8mm) or arch dilation (28.7 ± 2.8mm) and underwent concurrent VSARR and branched graft total arch replacement. There were no perioperative deaths or strokes and no distal aortic events or reoperations after median 1.26 years follow-up. Histologically, elastin fragmentation and collagen deposition were detectable in each aortic segment (n=4). scRNAseq identified a continuum of smooth muscle cell (SMC) phenotype modulation associated with progressively reduced contractile gene expression. Pathway analysis of 260 genes enriched during SMC modulation identified heightened integrin signaling, transforming growth factor-beta-responsiveness, cell adhesion, and extracellular matrix remodeling. Histologic confirmation using RNA probes specific for modulated SMCs (TGF-beta responsive gene SERPINE1 and glycoprotein TNFRSF11B ) identified these cells in the tunica media layer of each aortic segment, with greatest density in the root aneurysm but extending to the arch. In age-matched donor aortas, TNFRSF11B + cells were restricted to the atherosclerotic tunica intima, confirming specificity of medial SMC modulation in aneurysm. Conclusions: Total arch replacement during elective VSARR is feasible without substantial morbidity. In LDS patients with root aneurysm, matrix deterioration and SMC phenotype modulation are present in the non-dilated aortic arch, providing molecular rationale for aggressive arch replacement.

Dicer prevents activation of the type I interferon pathway in lipid-loaded macrophages

Abstract Background The expression of the endonuclease Dicer in macrophages decreases atherosclerosis and necrotic core formation by producing microRNAs such as miR-10a. This effect of Dicer is associated with enhanced mitochondrial respiration in lipid-loaded macrophages. However, the mechanism by which Dicer-dependent production of miRNAs in lipid-loaded macrophages regulates mitochondrial function is unclear. Purpose We aimed to determine the effect of Dicer on lipid-loaded macrophages in the context of atherosclerosis. Methods Mice with a myeloid cell-specific knockout of Dicer (Lys-Cre/Dicerflox/flox/Apoe−/− mice [M-Dicer−/−]) and control mice (Lys-Cre/DicerWT/WT/Apoe−/− mice [M-Dicer+/+]) were fed a high-fat diet (HFD) for 24 weeks. The oxygen consumption rate (OCR) in aortic arch plaques was studied ex vivo by Seahorse Flux XF 24 Analyzer. Bone marrow-derived macrophages (BMDMs) were stimulated with oxLDL (100 μg/mL) for 72 h. Lipid-loaded macrophages were used for proteomic analysis by mass spectrometry. RIP-prime- seq was performed in tAgo2 immunoprecipitates (IP) from Dicer+/+ and Dicer−/− BMDMs. The miRNA expression profile was determined in lipid-loaded BMDMs by NanoString technology. Stat1 phosphorylation was determined in lipid-loaded macrophages by Jess automated western blot system (ProteinSimple). Result The OCR in aortic arch tissue with plaques was higher than in those without plaques in M-Dicer+/+ mice after 24 weeks of HFD feeding. Dicer knockout in macrophages decreased the OCR in aortic arch tissues with plaques but not in aortic arch tissues without plaques (n=3–4, p<0.05). The proteomic analysis of oxLDL-treated BMDMs indicated that Dicer knockout activated the type I interferon signaling pathway by up-regulating the expression of STAT1/2 and interferon-stimulated genes, such as ISG15. Proteins related to mitochondrial DNA were upregulated (e.g., Dnmt3a) or downregulated (e.g., Tfam) by Dicer knockout (n=5, adj.p<0.05). RIP-prime-seq from BMDMs showed that 1376 transcripts were significantly enriched in the tAgo IP from Dicer+/+ compared with that from Dicer−/− BMDMs (n=3–5, adj.p<0.05) including Dnmt3a and Stat2. STAT1 phosphorylation was increased in Dicer−/− compared with Dicer+/+ BMDMs. Among the 299 miRNAs downregulated by Dicer knockout in lipid-loaded macrophages (n=6, adj.p<0.05), miR-29 and miR-30 have highly conserved binding sites (predicted by TargetScan) for Dnmt3a. Conclusion Our results indicate that Dicer expression in lipid-loaded macrophages limits Stat1/2-driven type I interferon response due to mitochondrial damage. This effect may be mediated by the suppression of Dnmt3a by miRNAs such as miR-29 and miR-30. This suggests that targeting Dnmt3a-mediated mitochondrial damage in lipid-loaded macrophages by miRNAs may be therapeutic strategy to limit atherosclerosis. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): DFG

Role of Artesunate on cardiovascular complications in rats with type 1 diabetes mellitus

BackgroundThe present study aimed to evaluate the effect of artesunate (ART) on the reduction of cardiovascular complications in a type 1 diabetes model and to investigate the associated mechanism based on the receptor for advanced glycation end-product (RAGE)/NF-κB signaling pathway.MethodsA total of 40 male Sprague-Dawley rats were randomly divided into five groups: The healthy, diabetic, 50 mg/kg ART (ig) treatment diabetic, 100 mg/kg ART (ig) treatment diabetic, and 6 U/kg insulin (iH) treatment diabetic groups. The treatment lasted 4 weeks after the diabetic model was established via intraperitoneal injection of streptozotocin. Blood samples were collected, and cardiovascular tissues were harvested and processed to measure various parameters after the animals were sacrificed. The myocardium and aortic arch tissues were evaluated using hematoxylin-eosin and Masson staining. Expression levels of RAGE, NF-κB, matrix metalloproteinase MMP9, MMP1 and CD68 in the myocardium and aortic arch tissues were detected using immunohistochemistry, and mRNA expression was determined using reverse transcription-quantitative PCR.ResultsThe results of the present study demonstrated that ART treatment may restrain diabetes-induced cardiovascular complications by maintaining heart and body weight while reducing blood glucose, as well as regulating blood lipid indicators to normal level (P < 0.05). The expression levels of NF-κB, CD68, MMP1, MMP9 and RAGE were decreased in the ART-treated diabetic rats (P < 0.05).ConclusionsART treatment may have a protective role against diabetes-associated cardiovascular complications in diabetic rats by inhibiting the expression of proteins in the RAGE/NF-κB signaling pathway and downstream inflammatory factors. High concentrations of ART had a hypoglycemic effect, while a low concentration of ART prevented cardiovascular complications.

TMT-Based Quantitative Proteomic Analysis Identification of Integrin Alpha 3 and Integrin Alpha 5 as Novel Biomarkers in Pathogenesis of Acute Aortic Dissection.

Background Acute aortic dissection (AAD) is a devastating cardiovascular disease with a high rate of disability and mortality. This disease often rapidly progresses to fatal multiple organ hypoperfusion, and the incidence has been increasing in recent years. However, the molecular mechanisms have yet to be clarified. This study is aimed at identifying the differential abundance proteins (DAPs) of aortic arch tissues in patients with AAD by proteomics and select possible proteins involved in AAD pathogenesis. Methods The fresh aortic arch tissues obtained from 5 AAD patients and 1 healthy donor were analyzed by amine-reactive tandem mass tag (TMT) labelling and mass spectrometry; then, the pathological sections of another 10 healthy donors and 20 AAD patients were chosen to verify the proteomic results by immunohistochemistry. Results Of 809 proteins identified by proteomic analysis, 132 differential abundance proteins (DAPs) were screened, of which 100 proteins were significantly downregulated while 32 upregulated. Among 100 downregulated proteins, two proteins with known function, integrin alpha 3 (ITGA-3) and ITGA-5, were selected as target proteins involved in AAD pathogenesis. Two target DAPs were verified by immunohistochemisty, and the results showed that the integrated option density (IOD) of ITGA-3 and ITGA-5 in AAD patients was significantly lower than that in healthy donors, which were consistent with the proteomic results (P < 0.001). Conclusion ITGA-3 and ITGA-5 represent novel biomarkers for the pathogenesis of AAD and might be a therapeutic target in the future.

Intermittent Hypoxia Improves Atherosclerosis Associated with Upregulation of Hif-1α and Nf-κB in Aortic Arch and Serum of Rabbits

Objectives To investigate the role of HIF-1α and NF-κB in intermittent hypoxia (IH) induced atherosclerosis in rabbits. Methods New-Zealand White rabbits were exposed to IH for 12 weeks (intermittent hypoxia of 21% O2 for 30 s and 8% O2 for 30 s, cyclically repeated for 8 h/day). We randomly assigned 48 male rabbits to groups of normoxia (RA) or IH. The rabbits in the RA group were continuously exposed to room air. After intervention of 4, 8, and 12 weeks, serum and aortic arch tissues were subjected to Elisa and immunohistochemical staining analyses respectively. The formation of atherosclerosis in the aortic arch was observed by HE. Results The formation of atherosclerosis in aortic tissue was observed by HE staining after IH. Compared with the RA rats, the level of HIF-1α and NF-κB in the serum of IH rats started to increase 4, 8, and 12 weeks after the beginning of the experiment (p 0.05). NF-κB protein expression was significantly increased after IH (p Conclusions IH may, through increased HIF-1α and NF-κB in rabbits, lead to lipid deposition, which leads to the formation of atherosclerosis and the occurrence of cardiovascular and cerebrovascular diseases.

Acute aortic dissection type A: from the past to the present

Acute aortic dissection type A (AADA) is a disease that has a catastrophic impact on a patient's life. Although refinements in perioperative and surgical care have translated into improved outcomes for patients affected by AADA, hospital mortality after surgery still remains very high, ranging from 15% to 30%. The management of AADA is complex and dictated by the modality of presentation, extent and location of the disease. Attempts to formulate consensus statements and relevant guidelines have identified significant gaps in the AADA knowledge with reference to pathogenesis, appropriate management and configuration for clinical services. Several international registries have been created to generate an evidence base that can address current and future management. In this context, the extensive use of surgical/hybrid approaches in treating AADA should be encouraged as well as more extensive interventions to replace the entire dissected aortic root and aortic arch tissues. In addition, the excellent outcome results recently achieved by high-volume surgical centers with focused expertise in AADA pointed out the need for regionalized super-centers offering specific multidisciplinary aortic surgery programs with dedicated high-specialized surgeons.

Hypertensive Changes Within the Aortic Arch of Infants and Children With Isolated Coarctation

Despite repair, a significant proportion of patients with coarctation of the aorta (CoA) present with late hypertension. Increased gene expression of aortic wall collagen and vascular smooth muscle cell markers occurs in the presence of hypertension. Before repair, a patent ductus arteriosus (PDA) limits hypertension proximal to the coarctation. We hypothesize that preoperative collagen and vascular smooth muscle expression from the aortic arch in children is variable, depending on the presence or absence of a PDA. We analyzed the expression patterns of collagen and vascular smooth muscle cell markers in 25 children with CoA using a quantitative polymerase chain reaction. Aortic arch tissue proximal to the CoA was normalized to descending aortic tissue distal to the coarctation. Collagen-I, transforming growth factor-β, elastin, and calponin were analyzed. At repair, 19 patients were aged younger than 3 months (14 with a PDA, 5 with a ligamentum arteriosum), and the remaining 6 were older than 1 year. There was no difference in age or weight between infants with or without a PDA. Infants without a PDA had the greatest difference in collagen-I expression compared with infants with a PDA (7.0 ± 1.6-fold vs 0.8 ± 1.1-fold, p = 0.01). Expression of transforming growth factor-β (4.3 ± 1.4 vs 2.6 ± 2.3, p = 0.01) and calponin (3.7 ± 0.7 vs 0.6 ± 1.1, p = 0.05) was lower from infants with vs without a PDA. Our findings provide evidence of preoperative changes in the aortic arch before repair, particularly in the absence of a PDA.

Total aortic arch replacement: current approach using the trifurcated graft technique.

Since the pioneering work of DeBakey, Cooley, and colleagues more than 50 years ago, surgical treatment of aneurysms involving the transverse aortic arch has been associated with substantial morbidity and mortality. Over the past 15 years, techniques for replacing the diseased aortic arch have evolved substantially. Previously, our approach to these operations involved femoral cannulation, profound-to-deep hypothermic circulatory arrest and retrograde cerebral perfusion, and the island technique for reattaching the brachiocephalic vessels. In contrast, we currently use innominate artery cannulation, deep-to-moderate hypothermic circulatory arrest with antegrade cerebral perfusion, bilateral cerebral monitoring with near-infrared spectroscopy, and the trifurcated graft (Y-graft) technique for reattaching the arch branches. Cannulating the innominate artery to provide an inflow site for cardiopulmonary bypass has facilitated the use of antegrade cerebral perfusion as a cerebral protection strategy; the left common carotid artery is additionally perfused to provide bilateral cerebral perfusion. Despite having a systemic circulatory arrest time that often exceeds 60 minutes, these improved perfusion strategies make it possible to consistently avoid cerebral circulatory arrest all together. A moderate temperature target of between 18 and 23 °C is now used; this appears to reduce the risk of hypothermic coagulopathy and improve hemostasis. Y-graft techniques, such as the trifurcated graft approach, have the advantages of eliminating residual aortic arch tissue and being easily tailored to the needs of the individual patient. This report describes total aortic arch replacement in patients with aneurysms that are confined to the ascending aorta and transverse aortic arch.

Total arch replacement procedure in a child with Loeys-Dietz syndrome

I read with great interest this article describing a total aortic root and arch replacement in a patient with Loeys–Dietz syndrome (LDS) [1]. There is no doubt that this case was a monumental effort and a tribute to their cardiac surgical programme. There is already a sufficient body of literature validating valvesparing root replacements in children with connective tissue disorders [2–4], so the value of the article lies in their description of the arch replacement. This raises two related questions regarding the arch repair: the indication for total arch repair and the technique of arch repair. The available literature reports very few cases of arch repair for patients with LDS [5, 6]. This implies that aneurysmal involvement of the arch is rare or is a later part of the nature history not yet described. The aortic arch in this case is minimally involved on the superior aspect, leaving the possibility that more conventional resection of the underneath side of the arch with the ascending aortic graft bevelled with a single anastomosis to the arch would have been sufficient. It remains unknown if this more straightforward approach would have been sufficient. The approach used by the authors has a clear advantage of complete resection of all aortic arch tissue at the expense of a more extensive procedure (270 min of cardiopulmonary bypass) and preventing any growth potential of the arch. Flow to the distal arch is limited by a 10 mm diameter section of Dacron graft. As our experience with LDS grows, the indications for complete resection of the aortic arch, as described in this case report, will hopefully be clarified.

A detailed microscopic study of the changes in the aorta of experimental model of postmenopausal rats fed with repeatedly heated palm oil

Hypercholesterolaemia, increase in lipid peroxidation and hyperhomocysteinaemia may contribute to the pathogenesis of atherosclerosis. This study was performed to examine the effects of repeatedly heated palm oil mixed with 2% cholesterol diet on atherosclerosis in oestrogen-deficient postmenopausal rats. Ovariectomy causes disruption of tunica intima layer of the rat aorta simulating a postmenopausal condition in females. Twenty-four ovariectomized female Sprague-Dawley rats were divided into four groups. The control group received 2% cholesterol diet without palm oil. A diet with 2% cholesterol content fortified with fresh, once-heated and five-times-heated palm oil was given to the other treatment groups. The rats were sacrificed at the end of 4 months of study and the aortic arch tissue was processed for histomorphometry and electron microscopy. On observation, there was disruption of the intimal layer of the ovariectomized rat aorta. There was no obvious ultrastructural change in the aorta of the rats fed with fresh palm oil. The ultrastructural changes were minimal with once-heated palm oil, in which there was a focal disruption of the endothelial layer. The focal disruption was more pronounced with five-times-heated palm oil. The results of this study show that the ingestion of fresh palm oil may have a protective effect on the aorta but such a protective action may be lost when the palm oil is repeatedly heated. The study may be clinically important for all postmenopausal women who are susceptible to atherosclerosis.

Adenosine A1 receptor expression during the transition from compensated pressure overload hypertrophy to heart failure

Myocardial adenosine is increased in pressure-overload hypertrophy (POH) and exerts important cardioprotective effects that delay transition to left ventricular failure. Adenosine-mediated signaling is attenuated in POH, but whether this depends on receptor or postreceptor defects is unknown. We therefore examined left ventricular adenosine A1-receptor gene and protein expression in experimental POH. Six week-old Sprague-Dawley rats were subjected to abdominal aortic banding (group B) or sham operation (group S). Echocardiography and left ventricular catheterization were performed 10 weeks later under ketamine anesthesia. Left ventricular and lung weight indices were obtained postmortem. A1-Receptor mRNA and protein expression were measured in samples from left ventricular, right ventricular and aortic arch tissue. Group B rats were subgrouped as having compensated or decompensated hypertrophy according to the absence or presence of lung congestion (lung weight index below or above mean +/- 2SD compared with group S rats). Both mRNA and protein A1-receptor expression were significantly increased in compensated group B versus group S rats (by, respectively, 37 and 77%; both P < 0.01). This was not observed in decompensated group B rats. No consistent gene or receptor expression changes were observed in right ventricular or aortic tissues. In compensated POH, increased interstitial adenosine concentrations are accompanied by increased expression of the specific receptor mediating the major cardioprotective effects of this autacoid. Such overexpression is no longer detectable once the transition from POH to left ventricular failure has occurred. These observations may have pathophysiological and, in perspective, therapeutic relevance to the course of hypertensive heart disease.

Innate immune recognition of invasive bacteria accelerates atherosclerosis in apolipoprotein E-deficient mice.

Infectious diseases have emerged as potential risk factors for cardiovascular disease (CVD). Epidemiological studies support a connection between periodontal disease, a chronic inflammatory disease of the supporting tissues of the teeth, and CVD. To directly test the connection between periodontal disease and atherosclerosis, apoE-/- mice were orally challenged with the periodontal disease pathogen Porphyromonas gingivalis or an invasion-impaired P gingivalis fimbriae-deficient mutant (FimA-). Both wild-type P gingivalis and the FimA- mutant were detected in blood and aortic arch tissue of apoE-/- mice by PCR after challenge. ApoE-/- mice challenged with wild-type P gingivalis presented with increased atherosclerotic plaque and expressed the innate immune response markers Toll-like receptor (TLR)-2 and TLR-4 in aortic tissue. Despite detection of the FimA- mutant in the blood and in aortic arch tissue, apoE-/- mice challenged with the FimA- mutant did not present with periodontal disease, upregulation of TLRs, or accelerated atherosclerosis. Furthermore, we demonstrate that immunization to control P gingivalis-elicited periodontal disease concomitantly prevents P gingivalis-accelerated atherosclerosis. We conclude that invasive P gingivalis accelerates atherosclerosis.

Nuclear microscopy investigations into the role of iron in atherosclerosis

Using nuclear microscopy we have investigated elemental distributions and concentrations in aortic arch tissue sections from three groups of rabbits: (a) rabbits on normal diet (normal group), (b) rabbits on a high-cholesterol diet (control group), and (c) rabbits on a high-cholesterol diet and depleted in iron by weekly bleeding (test group). Rabbits in each group were sacrificed at 4-week time intervals, at 4, 8, 12 and 16 weeks.As early as 4 weeks, the aortic arches of control rabbits showed signs of fatty streaks and lesions, with a 2-fold average increase of iron concentration in the artery wall of cholesterol fed rabbits compared to the normal group. At 12 and 16 weeks the control group exhibited well-developed atherosclerotic lesions with an accompanying 3-fold increase in iron. The test group showed a significant reduction of lesion formation compared to the controls, and only after 12 weeks was an increase in iron concentration in the aortic arch observed.These findings show that controlled blood letting results in reduced uptake of iron by the artery wall and delayed atherosclerotic lesion formation. This correlation strongly suggests that iron has an important role in the aetiology of atherosclerosis.