Layered Media Research Articles

Cyclic olefin copolymer (COC) as a promising biomaterial for affecting bacterial colonization: investigation on Vibrio campbellii

Cyclic olefin copolymer (COC) has emerged as an interesting biocompatible material for Organ-on-a-Chip (OoC) devices monitoring growth, viability, and metabolism of cells. Despite ISO 10993 approval, systematic investigation of bacteria grown onto COC is a still not documented issue.This study discusses biofilm formations of the canonical wild type BB120 Vibrio campbellii strain on a native COC substrate and addresses the impact of the physico-chemical properties of COC compared to conventional hydroxyapatite (HA) and poly(dimethylsiloxane) (PDMS) surfaces.An interdisciplinary approach combining bacterial colony counting, light microscopy imaging and advanced digital image processing remarks interesting results. First, COC can reduce biomass adhesion with respect to common biopolymers, that is suitable for tuning biofilm formations in the biological and medical areas. Second, remarkably different biofilm morphology (dendritic complex patterns only in the case of COC) was observed among the examined substrates. Third, the observed biofilm morphogenesis was related to the interaction of COC with the conditioning layer of the planktonic biological medium. Fourth, Level Co-occurrence Matrix (CGLM)-based analysis enabled quantitative assessment of the biomass textural fractal development under different coverage conditions. All of this is of key practical relevance in searching innovative biocompatible materials for pharmaceutical, implantable and medical products.

Enhanced expression of miR-20a driven by nanog exacerbated the degradation of extracellular matrix in thoracic aortic dissection

Thoracic aortic dissection (TAD) is a life-threatening vascular disease manifested as intramural bleeding in the medial layers of the thoracic aorta. The key histopathologic feature of TAD is medial degeneration, characterized by depletion of vascular smooth muscle cells (VSMCs) and degradation of extracellular matrix (ECM). MicroRNA, as essential epigenetic regulators, can inhibit the protein expression of target genes without modifying the sequences. This study aimed to elucidate the role and underlying mechanism of miR-20a, a member of the miR-17-92 cluster, in regulating ECM degradation during the pathogenesis of TAD. The expression of the miR-17-92 cluster was significantly increased in synthetic VSMCs derived from TAD lesions compared to contractile VSMCs isolated from normal thoracic aortas. Notably, the expression of miR-20a was increased in VSMCs in response to serum exposure and various stimuli. In TAD lesions, the expression of miR-20a was significantly negatively correlated with that of elastin. Elevated expression of miR-20a was also observed in thoracic aortas of TAD mice induced by β-aminopropionitrile fumarate and angiotensin II. Overexpression of miR-20a via mimic transfection enhanced the growth and invasive capabilities of VSMCs, with no significant impact on their migratory activity or the expression of phenotypic markers (α-SMA, SM22, and OPN). Silencing of miR-20a with inhibitor transfection mitigated the hyperactivation of MMP2 in VSMCs stimulated by PDGF-bb, as evidenced by reduced levels of active-MMP2 and increased levels of pro-MMP2. Subsequently, TIMP2 was identified as a novel target gene of miR-20a. The role of miR-20a in promoting the activation of MMP2 was mediated by the suppression of TIMP2 expression in VSMCs. In addition, the elevated expression of miR-20a was found to be directly driven by Nanog in VSMCs. Collectively, these findings indicate that miR-20a plays a crucial role in maintaining the homeostasis of the thoracic aortic wall during TAD pathogenesis and may represent a potential therapeutic target for TAD.

An Improved Method to Compute the Mutual Capacitance between Interdigital Transducers in Radio Frequency Surface Acoustic Wave Filters

This paper proposes an improved method to calculate the mutual capacitance between interdigital transducer (IDT) electrodes to enhance the accuracy of the traditional coupling-of-modes (COM) model, which is commonly used to simulate surface acoustic wave (SAW) filters and duplexers. In this method, the boundary element method (BEM) is adopted to obtain the capacitance per unit length in a layered medium, while the partial capacitance (PC) method is used to derive the effective relative permittivity of the multi-layered IDT. Numerical results from commercially available software are provided for comparison with the results calculated using the proposed method. The consistent results verify the validity and accuracy of this method, which also demonstrates significantly faster calculation speed compared to commercially available software. Precise electrical response prediction of a dual-mode SAW (DMS) filter can be achieved by applying this method to the COM model, and this ultra-fast calculation method can also be included in filter design optimization.

Reconstruction of elastic inclusions in layered medium

We consider the recovery of small inclusions in a two-layered and an arbitrary multi-layered medium for the elastic equation, respectively. We use layer potential techniques and asymptotic analysis to obtain asymptotic expansions of the perturbed elastic field in a two-layered and an arbitrary multi-layered medium, respectively. Furthermore, we show the uniqueness of the recovery of the locations and Lamé constants of small inclusions through a single measurement.

A RARE CASE OF TYPE A AORTIC DISSECTION PRESENTING AS ACUTE STROKE: A DIAGNOSTIC CHALLENGE

Abstract A 60–year–old woman presented to the emergency department with acute left hemiplegia, not chest pains. Past medical history was significant for family history of aortic aneurysm, arterial hypertension. At brain–CT was reported hypodensity areas in posterior arm of the right internal capsule and in right tempero–polar lobe, confirmed on brain–MRI, and compatible with acute ischemic injury. Echocolor–dopper of epiaortic vessels documentated ulcerated plaque into the right common carotid artery (CCA). Selective catheterization found focal dissection obstructing the flow, treated with self–expanding stent. On echocardiography evalutation for suspiction of TAAD: dilatation of ascending aorta with flap oscillation, severe arotic regurgitation, pericardial effusion (Fig. 1). CT–Angiography was performed with evidence of type A dissection extending superiorly to the right CCA and inferiorly to the iliac bifurcation. For coma state, the patient was mechanically ventilated, and seriate CTs showed new ischemic lesions and hemorrhagic infarction of previous. Because of contraindication for cardiac surgery due neurological state, the patient was referred at medical therapy as bridge to hybrid aortic arc substitution at resolution of intracranial hemorrhages. In the next days there was progressive improvement neurological status with restoration of sensory and autonomic breathing with hemodynamic stability. Aortic dissection (AD) is defined as a disruption of the medial layer leading to the formation of two lumens separated by an intimomedial flap. AD is a critical diagnosis to make due to life–threatening outcomes and its non–specific presentation as in the case of our patient where the management of AD was delayed due to an unusual initial clinical presentation. Multimodality imaging approach has been fundamental for correct diagnosis and risk stratification. A limited number of studies have reported cases with stroke as the first symptom with concomitant TAAD. Concomitant intracerebral hemorrhage and TAAD is a very rare presentation and the optimal timing of surgery in these patients is unknown. In our opinion, patients who presents acute stroke should be carefully evaluated using multimodal imaging to exclude TAAD before administering reperfusion therapy. In addition, performing CAS before surgery for TAAD is challenging but might be a valid treatment option to maintain good brain perfusion and improve prognosis, but further investigations are needed.

Mathematical Model of Vibration-Centrifugal Processing of Parts Using Loose Abrasive

The article presents some new theoretical and experimental solution of a scientific and applied problem of technological support for vibratory centrifugal processing of complex-profiled parts in a bulk abrasive environment. This solution aims to increase productivity while ensuring the desired quality of the processed surfaces. The authors have developed a mathematical model that describes the action of abrasive particles on the surface of the parts, taking into account the parameters of the granular abrasive medium based on Voigt’s law. This allows the description of dynamic processes in the processing environment for a wide range of material types. The natural frequencies of oscillations of the processed medium layer have been determined, which depend on the amplitude of its vibrations for different densities of soft and hard materials of the processed medium and the medium with linear-elastic properties. The methodology includes the use of test equipment to conduct experimental research on the process, which involves determining changes in specific metal removal rates and surface roughness using the frequency converter Altivar 71 with the PowerSuite v.2.5.0 software.

СИГНАЛЬНА МАКРОМОДЕЛЬ ОПТОПАРИ НА СТРУКТУРАХ ОРГАНІЧНОЇ ЕЛЕКТРОНІКИ

The paper is devoted to the basic approaches to the realization of the macromodel of optocouplers on organic structures for sensor devices. It is shown that the use of such structures is largely limited due to the time drift of parameters and temperature instability. In the course of the research, the possibility of compensating for these parameters directly during the operation of organic optocouples by measuring and analyzing the parameter drift was established. For this purpose, specialized built-in in-situ diagnostic systems and controlled signal transducers are used. In order to verify the functioning and optimize the parameters of signal transducers of built-in in- situ diagnostic systems, the paper describes the main approaches and the result of the implementation of the optocouple macromodel. The macromodel provides the ability to specify the components of sensor electronics optocouplers in accordance with the approaches and syntax of SPICE modeling and reflects parametric modulation with changes in ambient temperature, time instability, and flicker noise. The macromodel consists of five modules that describe the processes and specify the characteristics of the optocoupler: the light emitter (LED), self-heating of the optocoupler structure by the supply current, the optical medium or active layer of the optosensor, time drift and flicker noise, and the light receiver (photodiode or photoresistor). The modules are represented by substitution schemes of electrical components in accordance with the principle of functional analogy. The main approaches to specifying the parameters of macromodel components and examples of parametric studies based on it are considered. The use of the developed model makes it possible to obtain the values of compensation parameters for operational adjustment, in accordance with the operating conditions and properties of organic structures.

Efficient modeling of heat conduction in multiply bonded composites covered with thermal barrier coating

In engineering practice, 3D (three-dimensional) composites consisting of multiply thin layers of anisotropic materials have been extensively applied. For enhancing their thermal endurance, the composites are often coated with a very thin layer of medium with low conductivity, usually referred to as the thermal barrier coating (TBC). This paper presents an efficient algorithm for the boundary element method (BEM) to accurately compute the nearly singular integrals in modeling 3D anisotropic heat conduction in TBC-coated composites, consisting of several thin anisotropic media. This algorithm is especially efficient because no analytical transformation of the integrands is involved as proposed in the past. When the TBC is prescribed with Dirichlet condition, a new equivalent convective condition is proposed to replace the TBC modeling. Moreover, thin films of adhesives on interfaces are considered by introducing interfacial conductance. In the end, several examples are presented.

A Comparison of Three-Layer and Single-Layer Small Vascular Grafts Manufactured via the Roto-Evaporation Method.

This study used the roto-evaporation technique to engineer a 6 mm three-layer polyurethane vascular graft (TVG) that mimics the architecture of human coronary artery native vessels. Two segmented polyurethanes were synthesized using lysine (SPUUK) and ascorbic acid (SPUAA), and the resulting materials were used to create the intima and adventitia layers, respectively. In contrast, the media layer of the TVG was composed of a commercially available polyurethane, Pearlbond 703 EXP. For comparison purposes, single-layer vascular grafts (SVGs) from individual polyurethanes and a polyurethane blend (MVG) were made and tested similarly and evaluated according to the ISO 7198 standard. The TVG exhibited the highest circumferential tensile strength and longitudinal forces compared to single-layer vascular grafts of lower thicknesses made from the same polyurethanes. The TVG also showed higher suture and burst strength values than native vessels. The TVG withstood up to 2087 ± 139 mmHg and exhibited a compliance of 0.15 ± 0.1%/100 mmHg, while SPUUK SVGs showed a compliance of 5.21 ± 1.29%/100 mmHg, akin to coronary arteries but superior to the saphenous vein. An indirect cytocompatibility test using the MDA-MB-231 cell line showed 90 to 100% viability for all polyurethanes, surpassing the minimum 70% threshold needed for biomaterials deemed cytocompatibility. Despite the non-cytotoxic nature of the polyurethane extracts when grown directly on the surface, they displayed poor fibroblast adhesion, except for SPUUK. All vascular grafts showed hemolysis values under the permissible limit of 5% and longer coagulation times.

Ethanol-induced lung and cardiac right ventricular inflammation and remodeling underlie progression to pulmonary arterial hypertension.

Current research on ethanol-induced cardiovascular anomalies has focused on left ventricular (LV) function and blood pressure. To extend this area of research, we sought to determine whether ethanol-induced alterations in the structure and function of the right cardiac ventricle (RV) and pulmonary artery (PA) lead to pulmonary arterial hypertension (PAH). Two groups of male Sprague-Dawley rats received a balanced liquid diet containing 5% ethanol (w/v) or a pair-fed isocaloric liquid diet for 8 weeks. Weekly echocardiography was conducted to evaluate cardiopulmonary function, and lung and RV tissues were collected for exvivo histological and molecular studies. The ethanol-treated rats exhibited: (1) Elevated mean pulmonary arterial pressure and decreased pulmonary artery acceleration time/ejection time; (2) Pulmonary vascular remodeling comprising intrapulmonary artery medial layer thickening; and (3) RV hypertrophy along with increased RV/LV + septum, RV diameter, RV cardiomyocyte cross-sectional area, and LV mass/body weight ratio. These responses were associated with increased lung and RV pro-inflammatory markers, endothelin-1 (ET-1), TNF-α, and IL-6 levels and higher ET-1,ET-1 type A/B receptor ratio, and downregulation of the cytoprotective protein, bone morphogenetic protein receptor 2 (BMPR2), in the lungs. These findings show that moderate ethanol-induced cardiopulmonary changes underlie progression to PAH via an upregulated proinflammatory ET1-TNFα-IL6 pathway and suppression of the anti-inflammatory BMPR2.

Dynamic seismic signatures in a fluid‐saturated porous periodically layered medium considering effects of intrinsic anisotropy

AbstractThe interlayer wave‐induced fluid flow is an important mechanism for seismic attenuation and dispersion, as well as frequency‐dependent anisotropy, in the fluid‐saturated porous layered medium. This mechanism is closely related to the medium physical properties, and thus quantifying this mechanism is of significance for the seismic inversion of medium physical properties. Although numerous models have been proposed to quantify this mechanism, most models do not consider the effects of layer intrinsic anisotropy. To solve this problem, the effective complex‐valued and frequency‐dependent stiffness coefficients are derived for the fluid‐saturated porous medium composed of periodic transversely isotropic layers. Using the derived solutions, we study the effects of layer intrinsic anisotropy on seismic dispersion and attenuation, as well as frequency‐dependent anisotropy. It has been found that different matrix or fluid property contrasts between adjacent layers lead to different effects of intrinsic anisotropy. In addition, the effects of intrinsic anisotropy are also influenced by the fluid distribution when both matrix and fluid properties contrast among adjacent layers exist. In the low‐ and high‐frequency limits of wave‐induced fluid flow, our model reduces to the previous known results, which validates the correctness of our model. Our model can be applied in the seismic inversion of physical properties of reservoirs with intrinsic anisotropy, such as shale and tight sandstone reservoirs. In addition, our model can also be extended to cases with more complex intrinsic anisotropy and, thus, can be applied to complex anisotropic fractured reservoirs in the future.

Relationship between histomorphology and biomechanical properties of the ascending aortic wall in the aneurysm zone

Introduction. Thoracic aortic aneurysm (TAA) ranks 17th among all causes of a death. Over the past decade, the incidence rate of TAA increased several times and occurs in about 10 out of 100 thousand people per year. The search for the causes that lead to TAA is an urgent task. Local mechanical stress on the aortic wall leads to significant molecular and cellular changes in its tissue.Aim: To investigate the relationship between biomechanical properties and histological changes in the TAA tissue.Material and Methods. Thirty patients with TAA were included in the study. During surgery, fragments of the resected ascending aorta were obtained from each patient and subjected to uniaxial biomechanical testing to failure on an Instron 3343 testing machine (Instron, USA). Ultimate tensile stress at failure (σv, MPa), ultimate strain at failure (ε, mm/mm × %) and area under stress-strain curves (S, cm2) were calculated. In addition, the intraoperative material was fixed in formalin for histological examination of cellular and tissue changes in the aneurysm area. Inflammatory changes, the severity of aortic wall fibrosis and collagen/elastin ratio were assessed.Results. Atherosclerotic changes of the thoracic aortic wall were found in 43.3% (subgroup 1), aortitis – in 3.3%, connective tissue dysplasia – in 53.3% (subgroup 2) of the patients. Patient with inflammatory changes of the aortic wall was excluded. The biomechanical properties of the aorta were not statistically different between groups. A correlation was found between age with εcirc (r = –0.49) and Scirc (r = –0.54) and Slong (r = –0.5). A correlation was also found between εcirc and the degree of fibrosis in the medial layer of the aortic wall (r = –0.5) and collagen/elastin ratio (r = –0.61).Conclusions. Atherosclerotic changes in the aortic wall do not change the biomechanical properties of the TAA. However, structural changes in the medial layer of the aortic wall in the aneurysm zone result in reduced of its mechanical strength.

Fractional derivative modeling for dynamic response of layered viscoelastic media under moving time-harmonic loads

The dynamic response of layered viscoelastic media under moving time-harmonic loads is an important issue in transportation geotechnics. However, the existing research often has limitations in terms of the constant creep rate or time-independent relaxation modulus. To fill this gap, this study introduces a fractional Zener model to simulate the viscoelastic properties of media. First, the governing equations of the elastic medium are converted into ordinary differential equations using an integral transform. Subsequently, by introducing the fractional viscoelastic model and extended precise integration method, a solution to the dynamic response of layered viscoelastic media under moving time-harmonic loads is obtained. After comparing the results with those in existing literature, the reliability and accuracy of the proposed solution were verified. Finally, a parametric analysis was performed to further explore the influence of load velocity and fractional order on the dynamic response of the viscoelastic media.

A New Method of Plane-Wave Ultrasound Imaging Based on Reverse Time Migration.

Coherent plane-wave compounding technique enables rapid ultrasound imaging with comparable image quality to traditional B-mode imaging that relies on focused beam transmission. However, existing methods assume homogeneity in the imaged medium, neglecting the heterogeneity in sound velocities and densities present in real tissues, resulting in noise reverberation. This study introduces the Reverse Time Migration (RTM) method for ultrasound plane-wave imaging to overcome this limitation, which is combined with a method for estimating the speed of sound in layered media. Simulation results in a homogeneous background demonstrate that RTM reduces side lobes and grating lobes by approximately 30 dB, enhancing the contrast-to-noise ratio by 20% compared to conventional delay and sum (DAS) beamforming. Moreover, RTM achieves superior imaging outcomes with fewer compounding angles. The lateral resolution of the RTM with 5-9 angle compounding is able to achieve the effectiveness of the DAS method with 15-19 angle compounding, and the CNR of the RTM with 11-angle compounding is almost the same as that of the DAS with 21-angle compounding. In a heterogeneous background, experimental simulations and in vitro wire phantom experiments confirm RTM's capability to correct depth imaging, focusing reflected waves on point targets. In vitro porcine tissue experiments enable accurate imaging of layer interfaces by estimating the velocities of multiple layers containing muscle and fat. The proposed imaging procedure optimizes velocity estimation in complex media, compensates for the impact of velocity differences, provides more reliable imaging results.

Evaluation of the optimum conditions of an anaerobic Down-flow Stationary Fixed Film reactor for swine wastewater treatment

The Down-flow Stationary Fixed Film (DSFF) reactor is a downstream anaerobic reactor combined with a fixed layer of adhesive media that is capable of handling large organic loads, has cheap investment costs, and has a shorter treatment time than other conventional anaerobic technologies. In this study, the DSFF reactor was used to investigate its potential to remove contaminants from swine wastewater. The optimal operating conditions of the DSFF reactor including hydraulic retention time (HRT), organic concentration, and nutrient ratio were investigated. The obtained results showed that the COD removal efficiency increased from 50% to 79.721% when the influent COD enhanced from 500 to 3000 mg/L. The COD removal efficiency was 85.66%, 61.71% and 50.81% at three different nutritional ratios of C/N/P:250/1.5/1, C/N/P:250/7.5/1, and C/N/P:250/7.5/0.2, respectively. The overall results revealed that the optimal HRT is 12 hours, the optimal COD concentration is between 2000 mg/L and 3000 mg/L, and the optimal nutrient ratio is C/N/P:250/1.5/1. The DSFF reactor effectively manages BOD and phosphorus removal while handling a range of contamination levels in swine wastewater. Furthermore, there is no significant sludge loss and the operation mode is simple. This reactor is potentially appropriate for implementation in pig farming households.

Wave Interaction with Fractured Porous Layer in Porous Medium

Wave Interaction with Fractured Porous Layer in Porous Medium

Abstract 2018: The Role Of Interleukin 27 Receptor Signaling In Regulation Of Intestinal Barrier, Gut Microbiota And Abdominal Aortic Aneurysm.

Abdominal aortic aneurysm (AAA) is a cardiovascular disease characterized by accumulation of immune cells, inflammation, and degradation of medial layer of the abdominal aorta. Angiotensin II (Ang II) plays a key role in controlling blood pressure but is also able to regulate various immune and non-immune cells. While some studies suggested the role of Ang II in dysbiosis, the link between alteration of intestinal microbiota and AAA is largely unexplored. Cytokines are established regulators of inflammatory milieu in the aortic wall in AAA, but their distant contribution, for example via control of intestinal microbial homeostasis and cooperation with Ang II, has never been explored. Interleukin (IL)27 is a member of the IL6/IL12 superfamily that regulates various immune and non-immune cells. We previously showed that IL27R signaling cooperates with Ang II in the regulation of myelopoiesis thereby promoting AAA. Myeloid progenitor expansion and myeloid cell production driven by AngII are blunted in Apoe -/- Il27ra -/- mice. Here we found that Apoe -/- Il27ra -/- mice were also protected from gut dysbiosis and contain less pro-inflammatory bacterial genera in their colons. Unexpectedly, microbiota depletion accelerated AAA development in Apoe -/- Il27ra -/- mice, while Apoe -/- controls were protected from the disease. RNA seq analysis revealed upregulation of inflammatory pathways and downregulation in tight junctions and collagen in colons of Apoe -/- Il27ra -/- mice with ablated microbiota. Transcriptomic analysis of Apoe -/- colonic organoids stimulated with recIL27 shows upregulation of pathways linked to cell proliferation, cell cycle, and junction genes, indicating direct role of IL27. The analysis of the bone marrow revealed elevation of early myeloid progenitors which correlated with heightened circulating monocytes and neutrophils in Apoe -/- Il27ra -/- mice with ablated microbiota. Non-targeted metabolomics revealed microbiota and IL27R signaling-dependent alteration of serum metabolites likely mediating the effect on myeloid cells and AAA. Overall, our work uncovers novel role of IL27R signaling in the regulation of AAA, mechanistically connecting intestinal barrier and microbiota to the pathogenesis of this CVD.

Abstract 1147: Crosstalk Between Alk5 And Mtorc1 Signaling Promotes VSMC Differentiation And The Therapeutic Effect Of Rapamycin

Background: Vascular smooth muscle cells (VSMC) phenotypic switching contributes to vascular repair and remodeling but also to pathologies including intimal hyperplasia. The mTORC1 inhibitor rapamycin is an effective drug-eluting stent agent that promotes VSMC differentiation. TGFβ also promotes VSMC differentiation through SMAD transcription factors. We investigated unexpected convergence between these pathways in VSMC plasticity. Methods: We assessed the interactions between rapamycin and the TGFβ1 (ALK5) signaling in human coronary artery SMCs and in vascular remodeling using inducible SMC-specific knockout mice (ALK5iKO). Results: Genome-wide histone H3K27 acetylation analysis unexpectedly identified SMAD binding elements as the motif most enriched after rapamycin treatment of hCASMCs. Treatment with rapamycin promoted rapid phosphorylation of SMAD2/3. Extensive signaling studies revealed that this phosphorylation required ALK5 activity but not TGF-β ligand. Surprisingly, ALK5 and SMAD2/3 were required for rapamycin-induced differentiation. We determined that rapamycin relieves FKBP12 inhibition of ALK5 to promote ligand independent Smad signaling, and FKBP12 knockdown was sufficient to induce contractile genes. Notably, rapamycin treatment induced an interaction between TET2 and SMAD2/3, and these SMADs were required for differentiation-associated chromatin remodeling, including DNA hydroxymethylation and H3K27 acetylation at contractile genes, suggesting that SMADs and TET2 function in concert at SBE- and CArG-containing promoter regions. Furthermore, ALK5iKO mice exhibited severe intimal hyperplasia after carotid artery injury compared to controls and were entirely resistant to the therapeutic effect of rapamycin, despite persistent inhibition of mTORC1. Consistent with in vitro findings, treatment with rapamycin elevated pSmad3 staining post-injury in the medial layer of control but not ALK5iKO mice. Conclusions: We report the surprising observation that rapamycin requires FKBP12/ALK5/SMAD2/3 signaling in order to promote TET2-dependent chromatin remodeling and SMC differentiation. Understanding these mechanisms may reveal new therapeutic strategies for treating vascular diseases.

Abstract 2144: Smooth Muscle Cell Specific Beclin-1 Deficiency Promotes Aging-accelerated Aortic Stiffness In Mice

Background and Objective: Aortic stiffness, a hallmark of aging, is a significant riskfactor for cardiovascular diseases like hypertension and atherosclerosis. Vascularsmooth muscle cells (SMCs) play a crucial role in maintaining aortic structural integrity,and increased SMC stiffness contributes to age-accelerated aortic stiffness.Autophagy, a self-regulatory cellular process, declines with aging, predisposingindividuals to age-related diseases. Reduced levels of Beclin-1, a key autophagyinduction gene, have been observed in aging-associated diseases. However, thecontribution of SMC-derived Beclin-1 in aortic stiffness progression remains unknown.This study examined the contribution of SMC-derived Beclin-1 to aortic stiffnessdevelopment in mice. Methods and Results: Ultrasound measurements revealed increased aortic stiffnessin 60-week-old aged mice, characterized by elevated pulse-wave velocity (PWV) andreduced aortic distensibility and radial strain compared to 8-week-old young mice.Western blot and immunohistochemistry analyses showed a decline of aortic Beclin-1in the SMC-rich aortic medial layer of aged mice. To investigate the role of SMC-Beclin-1 in aortic stiffness, mice with inducible SMC-Beclin-1 deletion were generated bybreeding Acta2-CreERT2 hemizygous mice with Beclin-1 floxed mice. Baselinemeasurements at 8 weeks showed no PWV difference between Beclin-1 x Acta2-CreERT2 (Cre+) and non-Cre littermates (Cre-). However, following tamoxifen-induced Cre recombination, SMC-Beclin-1 deficiency significantly accelerated PWVby 18 weeks (Cre-: 2.4 ± 0.1 vs Cre+: 4.1 ± 0.2 m/s; P<0.001), accompanied byreduced aortic distensibility (Cre-:115.4 ± 3.2 vs Cre+: 93.1 ± 3.4; P<0.001) and radialstrain(Cre-:20.3 ± 0.7 vs Cre+:15.8 ± 0.7; P<0.001). Histological analyses indicatedthat Beclin-1 deficiency increased collagen deposition in aortic media and adventitia.RNA Sequencing and Western blot analyses identified extracellular matrix regulatingGalectin-3 and S100A4 as novel targets of Beclin-1, selectively upregulated in SMC-Beclin-1 deficient aorta. Conclusion: These findings suggest that SMC-derived Beclin-1 plays a critical rolein suppressing aging-accelerated aortic stiffness in mice.

Enteral Protease Inhibition Preserves Aortic Ultrastructure and Mechanics in Experimental Trauma/Hemorrhagic Shock

Introduction: Vascular compliance of large arteries is often overlooked in acute trauma/hemorrhagic shock (T/HS), as standard interventions, such as vasopressors, typically target systemic vascular resistance (SVR) regulated by small arterioles. However, patients may become refractory to vasopressors, and efforts to raise SVR may not restore mean arterial blood pressure (MAP), which is crucial for organ perfusion. We have previously reported compromised vascular compliance after T/HS in vivo with increased pulse wave velocity and ex vivo with diminished circumferential distensibility, that were both partially mitigated by enteral serine protease inhibition. To further elucidate the mechanisms behind these adverse changes, our aim was to directly assess the material stiffness, extracellular matrix (ECM) morphology, and matrix metalloproteinase (MMP) activity within the aortic wall tissue after T/HS, as well as to evaluate the effectiveness of enteral protease inhibition in this context.Methods: Anesthetized Wistar rats (350 - 400g) underwent laparotomy (trauma) and exsanguination to maintain a MAP of 35-40 mmHg for 90 minutes (shock). Animals were randomly assigned to receive either enteral gabexate mesilate protease inhibitor treatment (GM-treated) or vehicle-only (Untreated) via an orally-inserted catheter; investigators were blinded to the treatment assignation. At the conclusion of the shock period, animals were resuscitated with intravenous Lactated Ringer’s solution (LR) for two hours to achieve and maintain a MAP of at least 60 mmHg. A sham control group was also included for comparison. In all groups, the thoracic aorta was bisected, with one half sectioned for atomic force microscopy and histology and the other half homogenized for gelatin zymography. Liquid-phase force mapping was conducted on random areas (1600 μm2) of the medial layer in triplicate to determine the average Young’s modulus of the tissue. Collagen fibers were stained with picrosirius red, and elastin fibers were stained with Verhoeff Van Gieson. Results: After being subjected to T/HS and LR reperfusion, the aortic media of the Untreated group had a significantly higher average Young’s modulus than that of healthy sham vessels (862.7 kPa vs. 556.5 kPa, p < 0.05). The GM-treated group, however, better preserved its material elasticity (~650 kPa). These stiffness values negatively correlate with corresponding animals’ final MAP values measured at the end of the reperfusion period (r2 = 0.5031), supporting an association between vascular compliance and hemodynamic stability. The area of collagen within the tunica media was found to be significantly decreased in the Untreated compared to the sham group (4.93% vs. 10.26%, p < 0.05), but GM treatment was able to prevent collagen degradation (8.48%). Disruptions in elastin fibers were also observed at a higher frequency in the Untreated T/HS aorta compared to sham controls (3.3 vs. 1.7, p < 0.05) or GM-treated aortas (3.3 vs. 1.6, p < 0.05). Gelatin zymography revealed that enteral GM treatment also significantly attenuated elevated plasma MMP-9 (0.85 vs. 1.97 A.U., p < 0.01) and tissue MMP-2 activity (0.86 vs. 1.80 A.U., p < 0.05) seen following T/HS. Conclusions: Fluid-resuscitated traumatic hemorrhagic shock resulted in ultrastructural and biomechanical alterations in the aorta, indicating a loss in compliance. Enteral gabexate mesilate treatment effectively mitigated these pathological changes to the vasculature, suggesting the potential involvement of serine proteases in aortic ECM remodeling and large artery dysfunction in T/HS. Interventions against central artery impairment may be a promising strategy for improving blood pressure and survival in circulatory shock. Department of Defense Award W81XWH-17-2-0047. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.