Elastin Content Research Articles

Histological characterization of rat vocal fold across different postnatal periods.

To evaluate the vocal fold histological characteristics during different postnatal periods in rats, especially older rats. Sprague-Dawley rats aged 4 days, 4 and 12 weeks, and 12 and 24 months were used for the experiment. Five larynges were obtained for each age and cut into 5-μm consecutive sections. The expression of Ki-67 was assessed using immunohistochemistry to examine cell proliferation. Elastic van Gieson staining was used to detect the collagen and elastin concentrations. The cell type was determined using multicolor immunofluorescence. Ki-67 was not expressed in the macula flava (MF) of 12-week-, 12-month-, and 24-month-old adults. Collagen fibers in the lamina propria (LP) increased with age. The elastic fiber concentrations in the LP decreased significantly at 24 months (p < .01) but remained stable in the MF. All posterior MF cells showed strong glial fibrillary acidic protein and vimentin-positive reactions with weaker expressions of CD68 and α-smooth muscle actin (α-SMA). The myofibroblasts (α-SMA-positive) and macrophages (CD68-positive) in the LP of the 24-month-old rats were significantly the highest (p < .01). The extracellular matrix in the LP increases with age, presenting as an increase in collagen with the loss of elastin, which may be due to myofibroblast proliferation. Moreover, the cellular properties or extracellular matrix components of the mature MF in rats are comparable to those in humans.

PAI-1 Regulates the Cytoskeleton and Intrinsic Stiffness of Vascular Smooth Muscle Cells.

Plasma concentration of PAI-1 (plasminogen activator inhibitor-1) correlates with arterial stiffness. Vascular smooth muscle cells (SMCs) express PAI-1, and the intrinsic stiffness of SMCs is a major determinant of total arterial stiffness. We hypothesized that PAI-1 promotes SMC stiffness by regulating the cytoskeleton and that pharmacological inhibition of PAI-1 decreases SMC and aortic stiffness. PAI-039, a specific inhibitor of PAI-1, and small interfering RNA were used to inhibit PAI-1 expression in cultured human SMCs. Effects of PAI-1 inhibition on SMC stiffness, F-actin (filamentous actin) content, and cytoskeleton-modulating enzymes were assessed. WT (wild-type) and PAI-1-deficient murine SMCs were used to determine PAI-039 specificity. RNA sequencing was performed to determine the effects of PAI-039 on SMC gene expression. In vivo effects of PAI-039 were assessed by aortic pulse wave velocity. PAI-039 significantly reduced intrinsic stiffness of human SMCs, which was accompanied by a significant decrease in cytoplasmic F-actin content. PAI-1 gene knockdown also decreased cytoplasmic F-actin. PAI-1 inhibition significantly increased the activity of cofilin, an F-actin depolymerase, in WT murine SMCs, but not in PAI-1-deficient SMCs. RNA-sequencing analysis suggested that PAI-039 upregulates AMPK (AMP-activated protein kinase) signaling in SMCs, which was confirmed by Western blotting. Inhibition of AMPK prevented activation of cofilin by PAI-039. In mice, PAI-039 significantly decreased aortic stiffness and tunica media F-actin content without altering the elastin or collagen content. PAI-039 decreases intrinsic SMC stiffness and cytoplasmic stress fiber content. These effects are mediated by AMPK-dependent activation of cofilin. PAI-039 also decreases aortic stiffness in vivo. These findings suggest that PAI-1 is an important regulator of the SMC cytoskeleton and that pharmacological inhibition of PAI-1 has the potential to prevent and treat cardiovascular diseases involving arterial stiffening.

Effects of age, elastin density, and glycosaminoglycan accumulation on the delamination strength of human thoracic and abdominal aortas

Aortic dissection is a life-threatening condition caused by layer separation. Despite extensive research, the relationship between the aortic wall's structural integrity and dissection risk remains unclear. Glycosaminoglycan (GAG) accumulation and elastin loss are suspected to play significant roles. We investigated how age-related changes in aortic structure affect dissection susceptibility. Peeling tests were performed on longitudinal and circumferential thoracic (TA) and abdominal aortic (AA) strips from 35 donors aged 13–76 years (mean 38 ± 15 years, 34 % female). GAG, elastin, collagen, and smooth muscle cell (SMC) contents were assessed using bidirectional histology. Young TAs resisted longitudinal peeling better than circumferential, with delamination strengths of 65.4 mN/mm and 44.2 mN/mm, respectively. Delamination strength decreased with age in both directions, more rapidly longitudinally, equalizing at ∼20–25 mN/mm in older TAs. Delamination strength in AAs was 22 % higher than in TAs. No sex differences were observed. GAG density increased, while elastin density decreased by 2.5 % and 4 % per decade, respectively. Collagen density did not change with age, while SMC density decreased circumferentially. GAGs partially mediated the reduction in longitudinal delamination strength due to aging, while circumferential strength reduction was not mediated by changes in either GAG or elastin densities. This study explains why aortic dissections are more common in TAs, especially in older individuals, and why they typically propagate spirally. TAs exhibit lower delamination strength compared to AAs and experience strength reduction with age, a phenomenon linked to increased GAG accumulation and elastin loss. These findings enhance our understanding of the pathophysiological mechanisms behind aortic dissection. Statement of significanceThis work explores the age-dependent relationships between delamination strength in human aortas and wall structural content. We investigated 35 human aortas from donors aged 13 to 76 years, providing new insights into the biomechanical and histological factors that influence aortic dissection risk. Our findings elucidate how variations in elastin, glycosaminoglycan, collagen, and smooth muscle cell densities impact the structural integrity of the aorta, contributing significantly to the understanding of aortic dissection mechanisms.

Use of the senolytics dasatinib and quercetin for prevention of pelvic organ prolapse in a mouse animal model.

Senolytic agents have the potential to target age-related pathology associated with cellular senescence and reduce senescent cell activity in several disease processes. We utilized a mouse model of pelvic organ prolapse, Fibulin-5 knockout (Fbln-5-/-) mice, to assess the ability of dasatinib and quercetin (D+Q) to prevent development of prolapse. Four-week-old female Fbln-5-/- (n=63) and wild-type (WT) mice (n=54) were assigned to control (vehicle injection) or treatment (D = 5 mg/kg, Q = 50 mg/kg) groups. Weekly oral gavage injections were administered from weeks 4-8 of life. Pelvic organ prolapse quantification system measurements were obtained weekly. Vaginal tissue was harvested at 10, 12 and 20 weeks. Tissue analysis included immunostaining for cell cycle inhibitors, multiplex cytokine analysis, senescence-associated-β-galactosidase (SA-β-Gal) and histologic analysis of extracellular matrix proteins. Perineal body length was significantly longer in Fbln-5-/- treatment mice at 20 weeks. Expression of p16 and p53 was decreased in Fbln-5-/- treatment mice compared to controls (4.0% vs. 26.7%, p=0.0124 and 2.9% vs. 16.8%, p=0.272) at 20 weeks. Expression of SA-β-Gal and senescence-associated cytokines did not vary significantly between groups. At 20 weeks, vaginal tissue elastin content in Fbln-5-/- treatment mice increased compared to controls (1.04% vs. 0.84%, p=0.999). D+Q injections did not result in clinically significant differences in prolapse development but did demonstrate decreased expression of cellular senescence markers in Fbln-5-/- mice. This suggests senolytic agents may mitigate contributions of cellular senescence to tissue dysfunction associated with prolapse. Further studies are needed to confirm ideal timing, dosage, and route of senolytics in prevention of prolapse.

Greater TIMP-1 protein levels and neointimal formation represent sex-dependent cellular events limiting aortic vessel expansion in female rats.

Fragmentation/loss of the structural protein elastin represents the precipitating event translating to aortic expansion and subsequent aneurysm formation. The present study tested the hypothesis that greater protein expression of tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) and neointimal growth secondary to a reduction of medial elastin content represent sex-dependent events limiting aortic vessel expansion in females. TIMP-1 protein levels were higher in the ascending aorta of female versus male patients diagnosed with a bicuspid aortic valve (BAV). The latter paradigm was recapitulated in the aorta of adult male and female rats complemented by greater TIMP-2 expression in females. CaCl2 (0.5 M) treatment of the infrarenal aorta of adult male and female rats increased the in situ vessel diameter and expansion was significantly smaller in females despite a comparable reduction of medial elastin content. The preferential appearance of a neointimal region of the CaCl2-treated infrarenal aorta of female rats may explain in part the smaller in situ expansion and neointimal growth correlated positively with the % change of the in situ diameter. Neointimal formation was secondary to a significant increase in the density of medial/neointimal vascular smooth muscle cells (VSMCs) that re-entered the G2-M phase whereas VSMC cell cycle re-entry was attenuated in the CaCl2-treated infrarenal aorta of male rats. Thus, greater TIMP-1 expression in the aorta of female BAV patients may prevent excessive elastin fragmentation and preferential neointimal growth following CaCl2-treatment of the infrarenal aorta of female rats represents a sex-dependent biological event limiting vessel expansion secondary to a significant loss of the structural protein.

Elastin-specific MR probe for visualization and evaluation of an interleukin-1β targeted therapy for atherosclerosis

Atherosclerosis is a chronic inflammatory condition of the arteries and represents the primary cause of various cardiovascular diseases. Despite ongoing progress, finding effective anti-inflammatory therapeutic strategies for atherosclerosis remains a challenge. Here, we assessed the potential of molecular magnetic resonance imaging (MRI) to visualize the effects of 01BSUR, an anti-interleukin-1β monoclonal antibody, for treating atherosclerosis in a murine model. Male apolipoprotein E-deficient mice were divided into a therapy group (01BSUR, 2 × 0.3 mg/kg subcutaneously, n = 10) and control group (no treatment, n = 10) and received a high-fat diet for eight weeks. The plaque burden was assessed using an elastin-targeted gadolinium-based contrast probe (0.2 mmol/kg intravenously) on a 3 T MRI scanner. T1-weighted imaging showed a significantly lower contrast-to-noise (CNR) ratio in the 01BSUR group (pre: 3.93042664; post: 8.4007067) compared to the control group (pre: 3.70679168; post: 13.2982156) following administration of the elastin-specific MRI probe (p < 0.05). Histological examinations demonstrated a significant reduction in plaque size (p < 0.05) and a significant decrease in plaque elastin content (p < 0.05) in the treatment group compared to control animals. This study demonstrated that 01BSUR hinders the progression of atherosclerosis in a mouse model. Using an elastin-targeted MRI probe, we could quantify these therapeutic effects in MRI.

P102 PH-SENSOR GPR68 PLAYS A ROLE IN THE CARDIOPROTECTIVE EFFECTS OF A HIGH FIBRE DIET

Background/Objective: Dietary fibre lowers blood pressure (BP) via short-chain fatty acids, acidic metabolites released from fibre fermentation by the bacteria in the large intestine. This acidic microenvironment may activate pH-sensing receptor GPR68, expressed primarily on immune cells, which play a crucial role in BP regulation. Here, we aimed to investigate whether GPR68 confers the cardioprotective effects of a high-fibre diet in hypertension by regulating inflammatory responses. Methods: 6–8-week-old male wildtype (WT) and GPR68-deficient (Gpr68-/-) fed a control or high-fibre diet underwent subcutaneous implantation of minipumps containing Angiotensin II (0.75 mg/kg body weight/day, 4 weeks, n=8/group). BP was measured weekly by tail-cuff. Morphometric, histological, and flow cytometric analyses were performed following the 4-week protocol. Results: High-fibre-fed WT mice exhibited blunted elevations in systolic BP (week 4; p=0.0508) and lower cardiac interstitial collagen deposition (p=0.0495) compared to WT mice fed a control diet. However, high fibre did not lower BP (week 4; control vs high-fibre, p=0.689) or cardiac collagen deposition (p=0.842) in Gpr68-/- mice. High-fibre-fed WT mice exhibited improved aortic elastin content compared to control-fed WT mice (p=0.0503), whereas this remained negligible in Gpr68-/- mice (p=0.885). Flow cytometric analysis revealed that high fibre decreased aortic macrophage (p=0.0072) and neutrophil cell counts (p=0.0273) in mice, irrespective of genotype. High fibre also decreased overall renal immune cell counts (p=0.0213) and dendritic cells (p=0.0488) in mice, irrespective of genotype. Finally, high fibre-fed mice had overall decreased circulating immune cell counts (p=0.0264), specifically CD8+ T cells (p=0.0235), and γδ T cells (p=0.0264). Conclusions: High fibre intervention on Angiotensin II-treated GPR68-deficient mice did not lower their BP or cardiac fibrosis. All angiotensin II-treated mice fed a high-fibre diet exhibited prominent changes in various immune cell populations, irrespective of genotype. Nonetheless, this study provides novel insight that GPR68 is involved in the cardioprotective effects of a high-fibre diet. This is most likely via in an immune-independent manner, warranting further investigations into its underlying mechanisms of action.

GP VI-Mediated Platelet Activation and Procoagulant Activity Aggravate Inflammation and Aortic Wall Remodeling in Abdominal Aortic Aneurysm.

Platelets play an important role in cardiovascular and cerebrovascular diseases. Abdominal aortic aneurysm (AAA) is a highly lethal, atherosclerosis-related disease with characteristic features of progressive dilatation of the abdominal aorta and degradation of the vessel wall, accompanied by chronic inflammation. Platelet activation and procoagulant activity play a decisive role in the AAA pathology as they might trigger AAA development in both mice and humans. The present study investigated the impact of the major platelet collagen receptor GP (platelet glycoprotein) VI in pathophysiological processes underlying AAA initiation and progression. For experimental AAA induction in mice, PPE (porcine pancreatic elastase) and the external PPE model were used. Genetic deletion of GP VI offered protection of mice against aortic diameter expansion in experimental AAA. Mechanistically, GP VI deficiency resulted in decreased inflammation with reduced infiltration of neutrophils and platelets into the aortic wall. Furthermore, remodeling of the aortic wall was improved in the absence of GP VI, as indicated by reduced MMP (matrix metalloproteinase)-2/9 and OPN (osteopontin) plasma levels and an enhanced α-SMA (α-smooth muscle actin) content within the aortic wall, accompanied by reduced cell apoptosis. Consequently, an elevation in intima/media thickness and elastin content was observed in GP VI-deficient PPE mice, resulting in a significantly reduced aortic diameter expansion and reduced aneurysm incidence. In patients with AAA, enhanced plasma levels of soluble GP VI and fibrin, as well as fibrin accumulation within the intraluminal thrombus might serve as new biomarkers to detect AAA early. Moreover, we hypothesize that GP VI might play a role in procoagulant activity and thrombus stabilization via binding to fibrin. In conclusion, our results emphasize the potential need for a GP VI-targeted antiplatelet therapy to reduce AAA initiation and progression, as well as to protect patients with AAA from aortic rupture.

Comparison of Biomechanical and Microstructural Properties of Aortic Graft Materials in Aortic Repair Surgeries.

Mechanical mismatch between native aortas and aortic grafts can induce graft failure. This study aims to compare the mechanical and microstructural properties of different graft materials used in aortic repair surgeries with those of normal and dissected human ascending aortas. Five types of materials including normal aorta (n = 10), dissected aorta (n = 6), human pericardium (n = 8), bovine pericardium (n = 8) and Dacron graft (n = 5) were collected to perform uniaxial tensile testing to determine their material stiffness, and ultimate strength/stretch. The elastin and collagen contents in four tissue groups except for Dacron were quantified by histological examinations, while the material ultrastructure of five material groups was visualized by scanning electron microscope. Statistical results showed that three graft materials including Dacron, human pericardium and bovine pericardium had significantly higher ultimate strength and stiffness than both normal and dissected aortas. Human and bovine pericardia had significantly lower ultimate stretch than native aortas. Histological examinations revealed that normal and diseased aortic tissues had a significantly higher content of elastic fiber than two pericardial tissues, but less collagen fiber content. All four tissue groups exhibited lamellar fiber ultrastructure, with aortic tissues possessing thinner lamella. Dacron was composed of densely coalesced polyethylene terephthalate fibers in thick bundles. Aortic graft materials with denser fiber ultrastructure and/or higher content of collagen fiber than native aortic tissues, exhibited higher ultimate strength and stiffness. This information provides a basis to understand the mechanical failure of aortic grafts, and inspire the design of biomimetic aortic grafts.

Pirfenidone improves early cardiac function following myocardial infarction by enhancing the elastin/collagen ratio

BackgroundAcute myocardial infarction (AMI) is a leading cause of mortality worldwide, with reduced elastin/collagen ratios exacerbating cardiac dysfunction due to collagen-rich scar tissue replacing necrotic myocardial cells. This study aims to evaluate pirfenidone's therapeutic effect on early cardiac function post-AMI and elucidate its impact on the elastin/collagen ratio. MethodsSprague-Dawley rats were divided into four groups: Sham, AMI, AMI treated with PBS (AMI-PBS), and AMI treated with pirfenidone (AMI-PFD) (n=12 each). AMI was induced via coronary artery ligation. The AMI-PFD and AMI-PBS groups received pirfenidone and PBS for 14 days, respectively. Cardiac function, fibrosis, serum cytokines, collagen and elastin content, and their ratios were assessed. Cardiac fibroblasts (CFs) from neonatal rats were categorized into control, hypoxia-induced (LO), LO+PBS, and LO+PFD groups. ELISA measured inflammatory factors, and RT-PCR analyzed collagen and elastin gene expression. ResultsThe AMI-PFD group showed improved cardiac function and reduced serum interleukin-1β (IL-1β), IL-6, and transforming growth factor-β (TGF-β). Type I and III collagen decreased by 22.6 % (P=0.0441) and 34.4 % (P=0.0427), respectively, while elastin content increased by 79.4 % (P=0.0126). E/COLI and E/COLIII ratios rose by 81.1 % (P=0.0026) and 88.1 % (P=0.0006). CFs in the LO+PFD group exhibited decreased IL-1β, IL-6, TGF-β, type I and III collagen, with increased elastin mRNA, enhancing the elastin/collagen ratio. ConclusionPirfenidone enhances cardiac function by augmenting the early elastin/collagen ratio post-AMI.

Comparative Analysis of Decellularization Methods for the Production of Decellularized Umbilical Cord Matrix.

The importance of decellularized extracellular matrix (dECM) as a natural biomaterial in tissue engineering and regenerative medicine is rapidly growing. The core objective of the decellularization process is to eliminate cellular components while maximizing the preservation of the ECM's primary structure and components. Establishing a rapid, effective, and minimally destructive decellularization technique is essential for obtaining high-quality dECM to construct regenerative organs. This study focused on human umbilical cord tissue, designing different reagent combinations for decellularization protocols while maintaining a consistent processing time. The impact of these protocols on the decellularization efficiency of human umbilical cord tissue was evaluated. The results suggested that the composite decellularization strategy utilizing trypsin/EDTA + Triton X-100 + sodium deoxycholate was the optimal approach in this study for preparing decellularized human umbilical cord dECM. After 5 h of decellularization treatment, most cellular components were eliminated, confirmed through dsDNA quantitative detection, hematoxylin and eosin (HE) staining, and DAPI staining. Meanwhile, Masson staining, periodic acid-silver methenamine (PASM) staining, periodic acid-Schiff (PAS) staining, and immunofluorescent tissue section staining results revealed that the decellularized scaffold retained extracellular matrix components, including collagen and glycosaminoglycans (GAGs). Compared to native umbilical cord tissue, electron microscopy results demonstrated that the microstructure of the extracellular matrix was well preserved after decellularization. Furthermore, Fourier-transform infrared spectroscopy (FTIR) findings indicated that the decellularization process successfully retained the main functional group structures of extracellular matrix (ECM) components. The quantitative analysis of collagen, elastin, and GAG content validated the advantages of this decellularization process in preserving and purifying ECM components. Additionally, it was confirmed that this decellularized matrix exhibited no cytotoxicity in vitro. This study achieved short-term decellularization preparation for umbilical cord tissue through a combined decellularization strategy.

A Single Injection of ADRCs Does Not Prevent AAA Formation in Rats in a Randomized Blinded Design.

There is a pressing need for alternative medical treatments for abdominal aortic aneurysms (AAAs). Mesenchymal regenerative cells derived from adipose tissue (ADRCs) have shown potential in modulating the inflammation and immune responses that drive AAA progression. We hypothesized that ADRCs could reduce inflammation and preserve vascular integrity, potentially slowing the progression of AAA. In our study, subcutaneous adipose tissue was harvested from male Sprague Dawley rats, from which ADRCs were isolated. AAA was induced in these rats using intraluminal porcine pancreatic elastase, followed by intravenous administration of either ADRCs (106 cells) or saline (0.1 mL). We monitored the progression of AAA through weekly ultrasound, and the rats were sacrificed on day 28 for histological analysis. Our results showed no significant difference in the inner abdominal aortic diameter at day 28 between the control group (172% ± 73%, n = 17) and the ADRC-treated group (181% ± 75%, n = 15). Histological analyses of AAA cross-sections also revealed no significant difference in the infiltration of neutrophils or macrophages between the two groups. Furthermore, the integrity and content of elastin in the tunica media were similar between groups. These findings indicate that a single injection of ADRCs does not inhibit the development of AAA in rats in a randomized blinded study.

Noninvasive bipolar radiofrequency - vaginal application on swine model

The aim of the study was to evaluate the concentration of collagen and elastin fibers, the number of fibroblasts/fibrocytes and vessels, as well as depth of action in the vaginal wall in a swine model before and after intravaginal 480 kHz bipolar radiofrequency heating created by a 360-degree intravaginal applicator (Berger and Kraft Medical). Three swine’s were treated with a bipolar radiofrequency vaginal probe. Exposure to RF was administered twice, every 4 weeks, and then the vaginas were removed after slaughter, four weeks after the last RF exposure. Histology specimens were obtained from control and exposed areas. Tissue samples were stained by hematoxylin-eosin, orcein, and Mallory trichrome. The concentration of elastin and collagen fibers increased distinctly after a treatment protocol: elastin, on average, was 52.8%, and collagen, on average, was 103.6%. After the treatment protocol, we revealed a significant dispersion of fibroblasts-fibrocytes nuclei for particular animals in segmented areas, with a slightly marked falling trend. A degree of data variability cannot lead to a conclusion concerning the influence of RF heating on several vessels in evaluated areas. The depth of action of the RF heating, measured by collagen concentration, reached up to 1.3 mm of the vaginal wall thickness. Results imply that heating of the vaginal wall, created by radiofrequency, induces neocollagenogenesis and neoelastogenesis, leading to a distinctive rise of collagen and elastin fibers concentration at a depth of up to 1.3 mm of the thickness of the vaginal wall in the animal model.

Sexual Dimorphism of Elastic Fibers in Prenatal Lung Mice

Scientific data has revealed the existence of lung gender differences and therefore sparked a renewed interest in understanding the underlying mechanisms and their effect in the healthy lung development and/or in pathological conditions. Elastic fibers have an important role in lung development during pre and post-natal stages, because a well-developed pulmonary elastic fibers favour pre-natal lung maturation and enhance alveolarization. Sexual differences studies on lung elastic fibers content are focused essentially on the post-natal stage, with scarce data on pre-natal lung development. Using an experimental mice model, we developed this research work to study gender differences in the lungs elastic fibers during gestational days E15-E19, using image analysis and elastin HPLC methodologies. Our results show significant sexual dimorphism in lung elastin and elastic fibers content pre-natal stage, which is more evident in the last two gestational days (E18 and E19). Female’s mice have more elastin and elastic fibers which could mean that the elastogenesis process begins earlier than males. These results are an important contributes to understand the underlying factors involved in physiology and lung development sexual difference.

Abstract 2017: Interleukin-10 Hydrogel-Based Therapy For Abdominal Aortic Aneurysm In Rodent Model

Abdominal aortic aneurysms (AAA) are diagnosed in over 200,000 patients per year in the United States. Endovascular AAA repair offers a strategy for those unable to undergo open operation; however there still exists a treatment gap for those whose anatomy is not suitable for current stent graft options. In response to this need for novel therapeutics to prevent aneurysm proliferation, the objective of this work was to expand AAA treatment options via anti-inflammatory hydrogel application with a handheld bioprinting device. Induction of AAA in 8-week-old, male, Sprague-Dawley rats was achieved via intraluminal infusion of porcine elastase and topical application of calcium chloride to the infrarenal aorta. Following a 4-week incubation period, rats were treated with IL-10 loaded hydrogel or blank control hydrogel. The IL-10 loaded hydrogel was placed concentrically around the aorta from the lowest renal artery to the aortic bifurcation. Rats were sacrificed 4 weeks post-treatment. Histologic analysis included hematoxylin and eosin, picrosirius red, and Verhoeff-Van Gieson for inflammatory cell infiltration, collagen and elastin content, respectively. Three-dimensional aneurysm reconstruction and analysis was performed using SkyScan1076 micro-CT at baseline, post-induction/pre-treatment and sacrifice. Immunohistochemistry (IHC) was used to examine the presence of macrophage infiltration (ED1/CD68) as a marker of inflammation. Three-dimensional reconstruction demonstrated appropriate aneurysm formation in both groups and successful aneurysm mitigation in the treatment group only. Post-mortem histologic analysis showed irregularity of the aortic intima, fibrosis, abnormal collagen organization and dramatically decreased elastin concentration in control rodents while treated rats demonstrated preservation of aortic architecture. IHC demonstrated a significant increase in macrophage infiltration in the control group when compared to treated. Taken together, the results demonstrate that peri-aortic application of an IL-10 loaded hydrogel mitigates AAA expansion in a rat model. This novel approach may be a potential strategy for treating patients with AAA whose anatomy is unsuitable for endovascular intervention.

Abstract 3015: Matrix Metalloproteinase Inhibition In Rat Abdominal Aortic Aneurysm

Background: Matrix metalloproteinases (MMPs) have a robust proteolytic activity and play a fundamental role in degradation of extracellular matrix proteins. This degradation is a hallmark of the initiation, progression, and rupture of abdominal aortic aneurysms (AAAs). Hypothesis: We hypothesized that broad inhibition of MMPs with a 3 rd generation MMP inhibitor (GM6001) can reduce AAA inflammation and rupture using an established rat model. Aims: Our study aimed to investigate the potential of GM6001 in reducing AAA-related inflammation using a rat model, filling a critical gap in AAA research. Methods: Male Sprague-Dawley rats underwent intraluminal infrarenal perfusion of abdominal aorta using porcine pancreatic elastase (PPE), and daily β-aminopropionitrile (BAPN) to promote AAA rupture. Starting on postoperative day 3 (POD3) rats were treated daily either with or without GM6001 via intraperitoneal injections. On POD6, treated and untreated groups, underwent PET/CT imaging using a pan-MMP radiotracer 64Cu-RYM2 and in vivo aortic diameter measurement using ultrasound. Rate of rupture of treated and untreated groups was observed until POD14 (Fig 1A). Results: Treated rats demonstrated no evidence of toxicity or weight loss. Compared to untreated rats, treated rats had lower AAA rupture rates (P&lt;0.01; Fig 1B), smaller AAA diameters (P&lt;0.05; Fig 1C), and lower AAA MMP radiotracer uptake (P&lt;0.05; Fig 1D,1G). Total and active MMP-9 were significantly lower in treated rats (Fig 1E-F). In addition, IL-1B, IL-17A, IL-18, IFN-y, and RANTAS were significantly lower in treated rats, but TNF-a was higher (Fig 1H-M). VVG staining demonstrated a higher content of preserved elastin in treated rats (Fig 1N). Conclusion: Inhibition of MMPs with a 3 rd generation MMP inhibitor appears to be a promising therapeutic approach to impede the progression, inflammation, and rupture of AAAs in rats. This may represent a renewed pathway for MMP inhibition in human subjects with AAAs.

Daunorubicin Treatment Impairs Cardiac Function in The Ts65Dn Mouse Model Of Down Syndrome

Anthracycline treatment for leukemia is effective but has toxic side effects on the cardiovascular system. Few studies regarding the impact of anthracyclines on the heart in individuals with Down syndrome have been addressed although they are at a higher risk of developing leukemia. It is unknown if established mechanisms apply to individuals with Down syndrome. We hypothesize that anthracycline cardiotoxicity will lead to the enhanced impairment of cardiac function and initiate pronounced vascular dysfunction in a mouse model of Down syndrome. We used the Ts65Dn mouse model of Down syndrome to investigate the impact of daunorubicin chemotherapy on survival, arterial stiffness and left ventricular function. Four-month-old Ts65Dn (n=12) and wild-type control Ts65Dn (WT, n=8) mice were treated with 2mg/kg of daunorubicin or saline. Following treatment, left ventricular catheterization was performed to assess cardiac function. Serum cardiac troponin levels were evaluated using ELISA. Histological analysis was conducted on the heart and aorta of mice to assess the accumulation of elastin and collagen. We found decreased end-diastolic pressure (p=0.016) and ejection fraction (p=0.029) in Ts65Dn daunorubicin-treated mice compared to WT control. However, contractility (end-systolic pressure-volume relationship, p=0.221) and diastolic stiffness coeffcient (end-diastolic pressure-volume relationship, p=0.418) remained unchanged. Ts65Dn mice had a higher cardiac troponin concentration (p=0.02). Histological assessment showed no significant difference in collagen (p=0.841) and elastin (p=0.768) content. Daunorubicin negatively impacted end-diastolic pressure and ejection fraction of the Ts65Dn mouse model of Down syndrome. We demonstrated that we could recapitulate the findings of anthracycline cardiotoxicity in Ts65Dn mice indicating this is a good model to investigate toxicity. Continued work with this model will better elucidate the mechanisms underlying anthracycline cardiotoxicity in Down syndrome. This shows the need for constant screening after anthracycline treatment which will improve the survival of this population. NIH R21 HD099573. 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.

Tissue requirements for the application of aortic valve neocuspidization - appropriate pericardium properties and homogeneity?

Aortic valve neocuspidization (AVNeo) using autologous pericardium is a promising technique. Expected advantages are reduced immune response, appropriate biomechanics and lower treatment expenses. Nevertheless, autologous pericardium can be affected by patient's age and comorbidities. Usually, glutaraldehyde (GA) - fixed bovine pericardium is the basic material for aortic valve prostheses, easy available and carefully pre-examined in a standardized fabrication process. Aim of the study is the verification of autologous pericardial tissue homogeneity by analysing tissue thickness, biomechanics and extracellular matrix (ECM) composition. Segments of human GA-fixed pericardium selected by the surgeon based on visual criteria for cusp pre-cut and remaining after surgical AV replacement were investigated in comparison to bovine standard tissue treated equivalently. Pericardium sampling was performed at up to three positions of each sutured cusp for histological or biomechanical analysis, according to tissue availability. Human pericardia exhibited a higher heterogeneity in collagen content, density of vessel structures and elastic moduli. Thickness, vessel density and collagen and elastin content differed significantly between the species. In contrast, significant interindividual differences were detected in most properties investigated for human pericardial samples but only for tissue thickness in bovine tissues. Higher heterogeneity of human pericardium, differing vessel and collagen content compared to bovine state-of-the-art material might be detrimental for long term AV functionality or deterioration and have to be intensely investigated in patients follow up after autologous cusp replacement.

Relationships between Osteopontin, Osteoprotegerin, and Other Extracellular Matrix Proteins in Calcifying Arteries.

Osteopontin (OPN) and osteoprotegerin (OPG) are glycoproteins that participate in the regulation of tissue biomineralization. The aim of the project is to verify the hypothesis that the content of OPN and OPG in the aorta walls increases with the development of atherosclerosis and that these proteins are quantitatively related to the main proteins in the extracellular arteries matrix. Quantitative and qualitative analyses of the OPN and OPG content in 101 aorta sections have been conducted. Additionally, an enzyme-linked immunosorbent assay (ELISA) test has been performed to determine the collagen types I-IV and elastin content in the tissues. Correlations between the biochemical data and patients' age/sex, atherosclerosis stages, and calcification occurrences in the tissue have been established. We are the first to report correlations between OPN or OPG and various types of collagen and elastin content (OPG/type I collagen correlation: r = 0.37, p = 0.004; OPG/type II collagen: r = 0.34, p = 0.007; OPG/type III collagen: r = 0.39, p = 0.002, OPG/type IV collagen: r = 0.27, p = 0.03; OPG/elastin: r = 0.42, p = 0.001; OPN/collagen type I: r = 0.34, p = 0.007; OPN/collagen type II: r = 0.52, p = 0.000; OPN/elastin: r = 0.61, p = 0.001). OPN overexpression accompanies calcium deposit (CA) formation with the protein localized in the calcium deposit, whereas OPG is located outside the CA. Although OPN and OPG seem to play a similar function (inhibiting calcification), these glycoproteins have different tissue localizations and independent expression regulation. The independent expression regulation presumably depends on the factors responsible for stimulating the synthesis of collagens and elastin.

Mechanical, structural, and morphological differences in the iliac arteries

Iliac arteries play a crucial role in peripheral blood circulation. They are susceptible to various diseases, including aneurysms and atherosclerosis. Structure, material properties, and biomechanical forces acting on different regions of the iliac vasculature may contribute to the localization and progression of these pathologies. We examined 33 arterial specimens from common iliac (CI), external iliac (EI), and internal iliac (II) arteries obtained from 11 human donors (62 ± 12 years). We conducted morphometric, mechanical, and structural analyses using planar biaxial tests, constitutive modeling, and bi-directional histology on transverse and axial sections. The iliac arteries exhibited increased tortuosity and varying disease distribution with age. CI and II arteries displayed non-uniform age-related disease progression around their circumference, while EI remained healthy even in older individuals. Trends in load-free and stress-free thickness varied along the iliac vasculature. Longitudinally, EI exhibited the highest compliance compared to other iliac vessels. In contrast, CI was stiffest longitudinally, and EI was the stiffest circumferentially. Material parameters for all iliac vessels are reported for four common constitutive relations. Elastin near the internal elastic lamina displayed greater waviness in EI and II compared to CI. Also, EI had the least glycosaminoglycans (GAGs) and the highest elastin content. Our findings highlight variations in the morphological, mechanical, and structural properties of iliac arteries along their length. This data can inform vascular disease development and computational studies, and guide the development of biomimetic repair materials and devices tailored to specific iliac locations, improving vascular repair strategies.