Fragmentation Of Elastic Fibers Research Articles

Dexamethasone attenuated thoracic aortic aneurysm and dissection in vascular smooth muscle cell Tgfbr2-disrupted mice with CCL8 suppression.

What is the central question of this study? What is the relationship of chemokine (C-C motif) ligand 8 (CCL8) to thoracic aortic aneurysm and dissection (TAAD) formation in postnatal mice with vascular smooth muscle cell (VSMC) Tgfbr2 disruption, and is dexamethasone a potential treatment? What is the main finding and its importance? CCL8 was associated with the formation of TAAD in VSMC Tgfbr2-disrupted mice. Dexamethasone reduced TAAD formation and inhibited mitogen-activated protein kinase (p-p38) and nuclear factor-κB (p-p65) signalling pathways. CCL8 might be an important promoter of aortic inflammation. Dexamethasone provided potential therapeutic effects in TAAD treatment. Aortic inflammation plays a vital role in initiation and progression of thoracic aortic aneurysm and dissection (TAAD). Disturbance of the transforming growth factor-β (TGF-β) signalling pathway is believed to be one of the pathogenic mechanisms of TAAD. Initially, Myh11-CreERT2 .Tgfbr2f/f male mice were used to build a TAAD mouse model, and bioinformatic analyses revealed enriched inflammatory signal pathways and upregulated chemokine (C-C motif) ligand 8 (CCL8). So we hypothesized that vascular smooth muscle cell (VSMC) Tgfbr2 disruption in postnatal mice results in aortic inflammation associated with CCL8 secretion. Real-time quantitative PCR and serum enzyme-linked immunosorbent assay (ELISA) results confirmed that CCL8 expression began to increase after VSMC Tgfbr2 disruption. Next, we cultured mouse thoracic aortas ex vivo, and observed that the protein expression of CCL8 in culture supernatants was increased by ELISA. Subsequently, the co-localization of CCL8 with α-smooth muscle actin or CD68 was found to be significantly increased by immunofluorescence. Then, dexamethasone (DEX) was used to treat TAAD in VSMC Tgfbr2-disrupted mice; the results of histochemical, immunofluorescence and immunohistochemical staining indicated that DEX therapy reduced CCL8 secretion, inflammatory cell recruitment, aortic medial thickening, elastic fibre fragmentation, extracellular matrix degradation and contractile apparatus impairment, and thereby ameliorated TAAD formation. Western blotting showed that mitogen-activated protein kinase and nuclear factor-κB signalling pathways in aorta were overactivated after VSMC Tgfbr2 disruption, but inhibited by DEX therapy. Altogether, CCL8 might be an important promoter in TAAD formation of VSMC Tgfbr2-disrupted mice, and DEX provided potential therapeutic effects in TAAD treatment.

Congested Heart Failure in Small Breeds Dogs

Mitral valve disease, commonly known as MVD, is the most common heart disease in dogs, accounting for nearly 75% of all dogs affected. The characteristic of this predominant disease includes collagen degradation, elastic fiber fragmentation and proteoglycan accumulation, leading to deterioration of the mitral valve and ultimately, congestive heart failure (CHF). Treatment to reverse or even delay the damaging effects of MVD has not yet been discovered due to a lack of awareness of the underlying processes. Furthermore, this disease in dogs has many similarities with the human MVD and may potentially serve as a translational model for studying MVD further. Therefore, it is imperative to identify the causes and underlying mechanisms associated with canine MVD in order to treat these patients more efficiently at the earliest detectable stage. MicroRNAs (miRNAs) are small, 21‐25 nucleotides in length, non‐coding RNAs that can down‐regulate the expression of protein coding genes by binding to the 3’UTR sites in their messenger RNAs (mRNA), causing either degradation or gene silencing. Prior studies have shown that one miRNA may regulate multiple mRNAs, subsequently effecting the downstream levels of gene expression. Furthermore, if miRNAs prove to be a useful biomarker of heart disease, not only may they serve as detectors of early disease onset, but they may also be useful as therapeutic agents. Given this recent data, we propose to test the hypothesis that circulating miRNAs may be useful biomarkers for detection of CHF, secondary to MVD. Liquid biopsies (blood samples) were collected in EDTA tubes from 7 healthy dogs with no prior history of heart disease and 7 dogs being treated for CHF secondary to MVD. Total serum RNA was isolated using miRNeasy Serum/Plasma Kit (Qiagen). Isolated RNA was then reverse transcribed using miScript II RT Kit (Qiagen) and lastly, miRNA was quantified using miScript SYBR Green PCR Kit, along with miScript miRNA PCR Arrays (Qiagen).

Abstract 558: De Novo Synthesis Of Elastic Fibers In Dissected Aortas Of β-aminopropionitrile-administered Mice

Introduction: Elastin, a major component of extracellular matrix, is vital for aortic development and maintenance of integrity. It assumed that elastin synthesis does not occur in aortas of adults, as elastin fibers are stable molecule that may have a half-life as long as ~70 years. However, there is no direct evidence to verify this speculation. In addition, it remains unclear whether and how age-dependent alteration of elastin synthesis impacts the integrity of aortic wall. Methods and Results: First, elastin mRNA abundance was assessed in the aorta of male C57BL/6J mice at different ages (0, 2, 4, 10, 20 and 40-week-old, n=6/group). qPCR revealed that elastin mRNA was more abundant in the aorta at 2 weeks than 0 week of age, and decreased drastically at 4 weeks of age. Of note, elastin mRNA was barely detectable after 10 weeks of age. Lysyl oxidase, a key regulator in crosslinking of elastic fibers during aortic development, were also examined. Consistent with the temporal changes in elastin mRNA abundance, both molecules peaked at 2 weeks of age, and were much less abundant after 10 weeks of age. These results indicate that elastin synthesis and crosslinking were highly activated in the juvenile phase, but diminished in the adult phase. We next investigated the impact of age-dependent deletion of elastin synthesis and crosslinking on aortic integrity. β-aminopropionitrile (BAPN, 0.5% wt/vol) was administered for 12 weeks to induce aortic aneurysms and dissections in juvenile and adult male C57BL/6J mice (4, 24 weeks of age, n=15, 37/group). Corresponding to elastin mRNA abundance, development of aortic aneurysms and dissections were observed only in mice with BAPN started at juvenile, but not adult, phase. It is noteworthy that multiple laminas of fragmented elastic fibers were detected adjacent to the false lumen of dissected aortas. Since our time course study revealed that elastin synthesis was diminished after 10 weeks of age, elastic fibers observed around the false lumen was considered to be synthesized in response to aortopathy formation. Conclusion: Elastin mRNA synthesis is suppressed in the aorta of adult mice. However, its synthesis is reactivated in dissected aortas of BAPN-administered mice.

Biaxial Murine Vaginal Remodeling With Reproductive Aging.

Higher reproductive age is associated with an increased risk of gestational diabetes, pre-eclampsia, and severe vaginal tearing during delivery. Further, menopause is associated with vaginal stiffening. However, the mechanical properties of the vagina during reproductive aging before the onset of menopause are unknown. Therefore, the first objective of this study was to quantify the biaxial mechanical properties of the nulliparous murine vagina with reproductive aging. Menopause is further associated with a decrease in elastic fiber content, which may contribute to vaginal stiffening. Hence, our second objective was to determine the effect of elastic fiber disruption on the biaxial vaginal mechanical properties. To accomplish this, vaginal samples from CD-1 mice aged 2-14 months underwent extension-inflation testing protocols (n = 64 total; n = 16/age group). Then, half of the samples were randomly allocated to undergo elastic fiber fragmentation via elastase digestion (n = 32 total; 8/age group) to evaluate the role of elastic fibers. The material stiffness increased with reproductive age in both the circumferential and axial directions within the control and elastase-treated vaginas. The vagina demonstrated anisotropic mechanical behavior, and anisotropy increased with age. In summary, vaginal remodeling with reproductive age included increased direction-dependent material stiffness, which further increased following elastic fiber disruption. Further work is needed to quantify vaginal remodeling during pregnancy and postpartum with reproductive aging to better understand how age-related vaginal remodeling may contribute to an increased risk of vaginal tearing.

Extracellular Matrix in Aging Aorta.

The aging population is booming all over the world and arterial aging causes various age-associated pathologies such as cardiovascular diseases (CVDs). The aorta is the largest elastic artery, and transforms pulsatile flow generated by the left ventricle into steady flow to maintain circulation in distal tissues and organs. Age-associated structural and functional changes in the aortic wall such as dilation, tortuousness, stiffening and losing elasticity hamper stable peripheral circulation, lead to tissue and organ dysfunctions in aged people. The extracellular matrix (ECM) is a three-dimensional network of macromolecules produced by resident cells. The composition and organization of key ECM components determine the structure-function relationships of the aorta and therefore maintaining their homeostasis is critical for a healthy performance. Age-associated remodeling of the ECM structural components, including fragmentation of elastic fibers and excessive deposition and crosslinking of collagens, is a hallmark of aging and leads to functional stiffening of the aorta. In this mini review, we discuss age-associated alterations of the ECM in the aortic wall and shed light on how understanding the mechanisms of aortic aging can lead to the development of efficient strategy for aortic pathologies and CVDs.

Acetylsalicylic Acid Reduces Passive Aortic Wall Stiffness and Cardiovascular Remodelling in a Mouse Model of Advanced Atherosclerosis.

Acetylsalicylic acid (ASA) is widely used in secondary prevention of cardiovascular (CV) disease, mainly because of its antithrombotic effects. Here, we investigated whether ASA can prevent the progression of vessel wall remodelling, atherosclerosis, and CV complications in apolipoprotein E deficient (ApoE−/−) mice, a model of stable atherosclerosis, and in ApoE−/− mice with a mutation in the fibrillin-1 gene (Fbn1C1039G+/−), which is a model of elastic fibre fragmentation, accompanied by exacerbated unstable atherosclerosis. Female ApoE−/− and ApoE−/−Fbn1C1039G+/− mice were fed a Western diet (WD). At 10 weeks of WD, the mice were randomly divided into four groups, receiving either ASA 5 mg/kg/day in the drinking water (ApoE−/− (n = 14), ApoE−/−Fbn1C1039G+/− (n = 19)) or plain drinking water (ApoE−/− (n = 15), ApoE−/−Fbn1C1039G+/− (n = 21)) for 15 weeks. ApoE−/−Fbn1C1039G+/− mice showed an increased neutrophil–lymphocyte ratio (NLR) compared to ApoE−/− mice, and this effect was normalised by ASA. In the proximal ascending aorta wall, ASA-treated ApoE−/−Fbn1C1039G+/− mice showed less p-SMAD2/3 positive nuclei, a lower collagen percentage and an increased elastin/collagen ratio, consistent with the values measured in ApoE−/− mice. ASA did not affect plaque progression, incidence of myocardial infarction and survival of ApoE−/−Fbn1C1039G+/− mice, but systolic blood pressure, cardiac fibrosis and hypertrophy were reduced. In conclusion, ASA normalises the NLR, passive wall stiffness and cardiac remodelling in ApoE−/−Fbn1C1039G+/− mice to levels observed in ApoE−/− mice, indicating additional therapeutic benefits of ASA beyond its classical use.

310 Ruptured sinus of Valsalva aneurysm as a rare cause of sisto-diastolic murmur: role of multimodality imaging in diagnosis and surgical planning

Abstract A 27-year-old man had an incidental finding of sisto-diastolic murmur during a screening medical evaluation. Transthoracic and subsequent transesophageal echocardiography revealed a saccular enlargement of non-coronary (NC) sinus of Valsalva. The aneurysm extended into the right atrium (RA) and presented a large wall discontinuity, with continuous sisto-diastolic flow from the aorta to the right atrium. Computed tomography confirmed the findings and excluded other associated abnormalities. The patient underwent urgent surgical intervention. Intraoperatively, findings reported a floppy and cribrose saccular aneurysm sprouting from the NC sinus inside the RA. The correction turned out to be very challenging due to the close connection between the aneurysmal wall and the tricuspid valve (TV) and aortic valve (AV) annuli. The aortic NC sinus was excised and replaced with a Dacron patch. Damaging of the TV septal leaflet required repair through a consolidating suture involving the septal leaflet of TV and the corresponding annular insertion. AV replacement was also needed due to damage of the AV NC cusp. No complications occurred during the postoperative stay. Histopathology revealed severe atrophy of muscular and elastic fibres of the aortic wall, elastic fiber fragmentation, replacement fibrosis and extensive deposition of mucopolysaccharides. Sinus of Valsalva aneurysm (SoVA) is a rare condition characterized by an enlargement of the aortic root between the aortic valve and the sinotubular junction. SoVA can be either congenital, as a consequence of weakness of the elastic lamina, or acquired, due to infective, degenerative, or traumatic conditions. A prevalence of 0.09% was described in autopsy series and males are more frequently affected. Acute rupture of SoVA requires emergent surgery because of acute life-threatening haemodynamic instability. Congenital and chronic ruptured SoVA could be asymptomatic. Nevertheless, such incidental finding requires urgent surgical correction due to the possibility of unexpected further rupture, generating massive left-right shunt. The close relationship with nearby anatomical structures is a major issue which should be taken into account. In this perspective multimodality imaging is of paramount importance, allowing for a fine surgical planning and avoidance of complications.

Mechanical characterization of dissected and dilated human ascending aorta using Fung-type hyperelastic models with pre-identified initial tangent moduli for low-stress distensibility

Ascending aortic dissection (AD) is a potentially fatal vascular disease associated with degradation and fragmentation of the elastic fibers in the aortic media, increasing low-stress distensibility, and a dilated aorta may lead to dissection. In this study, a Fung-type hyperelastic model was formulated incorporating the initial tangent moduli (ITM) of stress–strain curves as an index of low-stress distensibility. ITM were correlated with the material constants by linearizing incompressible stress–strain relationships at zero strain. For uniaxial loading tests, the robustness of the material constants was examined in the stress ranges of 0–200, 0–180, and 0–160 kPa and to the ITM values of 100%, 95%, and 90%. Examination revealed stable changes in the material constants of 80% of the specimens. For equibiaxial stretch tests, the material constants were determined for each curve of the isotropic and anisotropic deformation groups by pre-identifying the ITM and minimizing fitting errors using isotropic or anisotropic models. The errors for all groups were <6% using a transversely isotropic model, and <10% for an orthotropic model. Comparisons with experimental curves showed that Fung-type models described both the ITM and significant stiffening at high stress levels. The mechanical characteristics of the aorta in the stage prior/posterior to dissection is such that while hardening occurs under both low- and high-stress levels with an increase in collagen content as an aging response, softening occurs under low-stress conditions due to histological abnormalities such as elastin deficiency and fragmentation. Numerical simulations using Fung-type models implied that elastic fiber degeneration and fragmentation in AD tissues reduced not only the low-stress stiffness but also the elastic stiffness with superimposed shear. The latter stiffness was modulated by the stiffening at high stress levels in tensile deformation behavior and normal-strain state under physiological loading conditions, and therefore provides further insight into wall rupture.

Sex Differences in Proximal Thoracic Aortic Disease Pathology: A Call to Action

Abstract Introduction/Objective Sex disparity is reported across all forms of cardiovascular diseases. Only few studies have focused on sex differences in thoracic aortic disease pathology. We aim to identify and understand sex differences in this patient group to bridge the knowledge gap and improve clinicopathologic outcomes. Methods/Case Report This is a retrospective analysis of 83 proximal thoracic aortic aneurysm and dissection (TAAD) cases treated at a single quaternary care center in 2019. Chart review was done for demographics. Consensus criteria (Stone JR et al. Cardiovasc Pathol 2015; 24:267-78; Halushka MK et al. Cardiovasc Pathol 2016; 25:247-57) and a scoring system (Waters KM et al. Cardiovasc Pathol 2017; 30:6-11) were used for pathology reporting. Clinical correlation was also made. Pearson’s chi-square test was used for statistical analysis. Results (if a Case Study enter NA) 83 patients (61 male and 22 female) were retrieved. Overall thoracic aortopathy was higher among males, accounting for 73.4% of individuals with TAAD. In a subgroup analysis, there was no sex difference in dissection, aortic root involvement, and bicuspid aortic valve (p&amp;gt;0.05). Genetic aortopathy was more prevalent in females than males (27.2% vs 9.8%, p=0.04) alongside early age at first aortic event (median age: 31y vs 52y). Histopathologically, females had frequent translamellar mucoid extracellular matrix accumulation (45.4% vs 22.9%, p=0.04), extensive (54.5% vs 27.8%, p=0.02) and severe (59% vs 34.4%, p=0.04) elastic fiber fragmentation, higher band like (9% vs 6.5%, p&amp;gt;0.05) plus extensive (13.6% vs 4.9%, p&amp;gt;0.05) smooth muscle nuclei loss, and extensive (13.6% vs 1.6%, p=0.01) plus dense (4.5% vs 1.6%, p&amp;gt;0.05) laminar medial collapse than males. Conclusion In our patient population, females have a lower prevalence of thoracic aortic disease treated with open repair. However, those who develop TAAD harbor a greater burden of wall pathology and probable worse outcomes. We recommend sex-based analysis of all research on thoracic aortic diseases.

089 Autofluorescence imaging for non-invasive visualization and quantification of skin lesions of patients with pseudoxanthoma elasticum

Pseudoxanthoma elasticum (PXE, OMIM 264800) is a rare multisystemic autosomal recessive connective tissue disorder. In PXE patients, mutations in the ABCC6 gene lead to ectopic deposition of calcium salts and fragmentation of elastic fibers. Dystrophic calcification results in skin manifestations, followed by severe ocular and cardiovascular complications. The aim of this study was to introduce a novel non-invasive technique for visualization and quantification of the severity of skin lesions of PXE patients.

Aortic distensibility in Marfan syndrome: a potential predictor of aortic events?

ObjectivesPatients with Marfan syndrome (MFS) are prone to develop aortic aneurysms due to fragmentation of elastic fibres, resulting in reduced distensibility of the aorta. Reduced distensibility was previously shown to...

Deletion of type VIII collagen reduces blood pressure, increases carotid artery functional distensibility and promotes elastin deposition

Arterial stiffening is a significant predictor of cardiovascular disease development and mortality. In elastic arteries, stiffening refers to the loss and fragmentation of elastic fibers, with a progressive increase in collagen fibers. Type VIII collagen (Col-8) is highly expressed developmentally, and then once again dramatically upregulated in aged and diseased vessels characterized by arterial stiffening. Yet its biophysical impact on the vessel wall remains unknown. The purpose of this study was to test the hypothesis that Col-8 functions as a matrix scaffold to maintain vessel integrity during extracellular matrix (ECM) development. These changes are predicted to persist into the adult vasculature, and we have tested this in our investigation. Through our in vivo and in vitro studies, we have determined a novel interaction between Col-8 and elastin. Mice deficient in Col-8 (Col8−/−) had reduced baseline blood pressure and increased arterial compliance, indicating an enhanced Windkessel effect in conducting arteries. Differences in both the ECM composition and VSMC activity resulted in Col8−/− carotid arteries that displayed increased crosslinked elastin and functional distensibility, but enhanced catecholamine-induced VSMC contractility. In vitro studies revealed that the absence of Col-8 dramatically increased tropoelastin mRNA and elastic fiber deposition in the ECM, which was decreased with exogenous Col-8 treatment. These findings suggest a causative role for Col-8 in reducing mRNA levels of tropoelastin and the presence of elastic fibers in the matrix. Moreover, we also found that Col-8 and elastin have opposing effects on VSMC phenotype, the former promoting a synthetic phenotype, whereas the latter confers quiescence. These studies further our understanding of Col-8 function and open a promising new area of investigation related to elastin biology.

Dynamic Crosstalk between Vascular Smooth Muscle Cells and the Aged Extracellular Matrix.

Vascular aging is accompanied by the fragmentation of elastic fibers and collagen deposition, leading to reduced distensibility and increased vascular stiffness. A rigid artery facilitates elastin to degradation by MMPs, exposing vascular cells to greater mechanical stress and triggering signaling mechanisms that only exacerbate aging, creating a self-sustaining inflammatory environment that also promotes vascular calcification. In this review, we highlight the role of crosstalk between smooth muscle cells and the vascular extracellular matrix (ECM) and how aging promotes smooth muscle cell phenotypes that ultimately lead to mechanical impairment of aging arteries. Understanding the underlying mechanisms and the role of associated changes in ECM during aging may contribute to new approaches to prevent or delay arterial aging and the onset of cardiovascular diseases.

Dermoscopic features of pseudoxanthoma elasticum

Pseudoxanthoma elasticum (PXE), also known as Gröenblad-Strandberg syndrome, is an autosomal recessive connective tissue disease characterized by aberrant mineralization of soft connective tissue resulting in fragmentation of elastic fibers, involving primarily the skin, eyes and cardiovascular. To our knowledge, there is only two other reports of the dermoscopic features of PXE in the literature. We report clinical and dermoscopic description of two new cases. We hypothesize for the first time that the dermoscopic appearance may differ according to the age of PXE lesions.

Diabetic Foot: The Role of Fasciae, a Narrative Review.

Wound healing is an intricate, dynamic process, in which various elements such as hyperglycemia, neuropathy, blood supply, matrix turnover, wound contraction, and the microbiome all have a role in this "out of tune" diabetic complex symphony, particularly noticeable in the complications of diabetic foot. Recently it was demonstrated that the fasciae have a crucial role in proprioception, muscular force transmission, skin vascularization and tropism, and wound healing. Indeed, the fasciae are a dynamic multifaceted meshwork of connective tissue comprised of diverse cells settled down in the extracellular matrix and nervous fibers; each constituent plays a particular role in the fasciae adapting in various ways to the diverse stimuli. This review intends to deepen the discussion on the possible fascial role in diabetic wounds. In diabetes, the thickening of collagen, the fragmentation of elastic fibers, and the changes in glycosaminoglycans, in particular hyaluronan, leads to changes in the stiffness, gliding, and the distribution of force transmission in the fasciae, with cascading repercussions at the cellular and molecular levels, consequently feeding a vicious pathophysiological circle. A clear scientific perception of fascial role from microscopic and macroscopic points of view can facilitate the identification of appropriate treatment strategies for wounds in diabetes and create new perspectives of treatment.

Early Aberrant Angiogenesis Due to Elastic Fiber Fragmentation in Aortic Valve Disease.

Elastic fiber fragmentation (EFF) is a hallmark of aortic valve disease (AVD), and neovascularization has been identified as a late finding related to inflammation. We sought to characterize the relationship between early EFF and aberrant angiogenesis. To examine disease progression, regional anatomy and pathology of aortic valve tissue were assessed using histochemistry, immunohistochemistry, and electron microscopy from early-onset (<40 yo) and late-onset (≥40 yo) non-syndromic AVD specimens. To assess the effects of EFF on early AVD processes, valve tissue from Williams and Marfan syndrome patients was also analyzed. Bicuspid aortic valve was more common in early-onset AVD, and cardiovascular comorbidities were more common in late-onset AVD. Early-onset AVD specimens demonstrated angiogenesis without inflammation or atherosclerosis. A distinct pattern of elastic fiber components surrounded early-onset AVD neovessels, including increased emilin-1 and decreased fibulin-5. Different types of EFF were present in Williams syndrome (WS) and Marfan syndrome (MFS) aortic valves; WS but not MFS aortic valves demonstrated angiogenesis. Aberrant angiogenesis occurs in early-onset AVD in the absence of inflammation, implicating EFF. Elucidation of underlying mechanisms may inform the development of new pharmacologic treatments.

Application of deep learning neural network in pathological image classification of non-inflammatory aortic membrane degeneration

Objective: To investigate the value of deep learning in classifying non-inflammatory aortic membrane degeneration. Methods: Eighty-nine cases of non-inflammatory aortic media degeneration diagnosed from January to June 2018 were collected at Beijing Anzhen Hospital, Capital Medical University, China and scanned into digital sections. 1 627 hematoxylin and eosin stained photomicrographs were extracted. Combined with the ResNet18-based deep convolution neural network model, 4-category classification of pathological images were performed to diagnose the non-inflammatory aortic lesion. Results: The prediction model of artificial intelligence assisted diagnosis had the best accuracy, sensitivity and precision in identifying lesions with smooth muscle cell nuclei loss, which were 99.39%, 98.36% and 98.36%, respectively. The classification accuracy of elastic fiber fragmentation and/or loss lesions was 98.08%, while that of intralamellar mucoid extracellular matrix accumulation lesions was 96.93%. The overall accuracy of the classification model was 96.32%, and the area under the curve was 0.982. Conclusions: The accuracy of deep learning neural network model in the 4-category classification of non-inflammatory aortic lesionsis confirmed based on digital photomicrographs. This method can effectively improve the diagnostic efficiency of pathologists.

A human importin-β-related disorder: Syndromic thoracic aortic aneurysm caused by bi-allelic loss-of-function variants in IPO8

Importin 8, encoded by IPO8, is a ubiquitously expressed member of the importin-β protein family that translocates cargo molecules such as proteins, RNAs, and ribonucleoprotein complexes into the nucleus in a RanGTP-dependent manner. Current knowledge of the cargoes of importin 8 is limited, but TGF-β signaling components such as SMAD1-4 have been suggested to be among them. Here, we report that bi-allelic loss-of-function variants in IPO8 cause a syndromic form of thoracic aortic aneurysm (TAA) with clinical overlap with Loeys-Dietz and Shprintzen-Goldberg syndromes. Seven individuals from six unrelated families showed a consistent phenotype with early-onset TAA, motor developmental delay, connective tissue findings, and craniofacial dysmorphic features. A C57BL/6N Ipo8 knockout mouse model recapitulates TAA development from 8-12weeks onward in both sexes but most prominently shows ascending aorta dilatation with a propensity for dissection in males. Compliance assays suggest augmented passive stiffness of the ascending aorta in male Ipo8-/- mice throughout life. Immunohistological investigation of mutant aortic walls reveals elastic fiber disorganization and fragmentation along with a signature of increased TGF-β signaling, as evidenced by nuclear pSmad2 accumulation. RT-qPCR assays of the aortic wall in male Ipo8-/- mice demonstrate decreased Smad6/7 and increased Mmp2 and Ccn2 (Ctgf) expression, reinforcing a role for dysregulation of the TGF-β signaling pathway in TAA development. Because importin 8 is the most downstream TGF-β-related effector implicated in TAA pathogenesis so far, it offers opportunities for future mechanistic studies and represents a candidate drug target for TAA.

Blood pressure-independent inhibition of Marfan aortic root widening by the angiotensin II receptor blocker valsartan.

Marfan syndrome (MFS) is a genetic disorder that results in accelerated aortic root widening and aneurysm. However, management of MFS patients with blood pressure (BP)‐lowering medications, such as angiotensin II (AngII) receptor blocker (ARB) losartan, continues to pose challenges due to their questionable efficacy at attenuating the rate of aortic root widening in patients. Herein we investigate the anti‐aortic root widening effects of a sub‐BP‐lowering dose valsartan, an ARB previously linked to non‐BP lowering anti‐remodeling effects. Despite absence of BP‐lowering effects, valsartan attenuated MFS aortic root widening by 75.9%, which was similar to a hypotensive dose of losartan (79.4%) when assessed by ultrasound echocardiography. Medial thickening, elastic fiber fragmentation, and phospho‐ERK signaling were also inhibited to a similar degree with both treatments. Valsartan and losartan decreased vascular contractility ex vivo between 60% and 80%, in a nitric oxide (NO)‐sensitive fashion. Valsartan increased acetylcholine (Ach)‐induced vessel relaxation and phospho‐eNOS levels in the aortic vessel supporting BP‐independent activation of protective endothelial function, which is critical to ARB‐mediated aortic root stability. This study supports the concept of achieving aortic root stability with valsartan in absence of BP‐lowering effects, which may help address efficacy and compliance issues with losartan‐based MFS patient management.

Re-interventions after the Ross procedure: reasons, technical approaches, immediate outcomes

Re-interventions after pulmonary autograft aortic valve replacement (Ross procedure) may be associated with dysfunction of the neoaortic, neopulmonary, or both operated valves. Late dysfunction, other than infective endocarditis, is associated with underlying conditions, technical errors, and unsuitable pulmonary trunk replacement materials. Re-interventions are technically complex, while tactical approaches have not been definitively formulated. Objective: to analyze re-interventions in patients after Ross procedure, technical approaches and immediate outcomes. Material and methods. Between 2001 and 2019, 14 patients were reoperated upon within 2 days to 21 years after primary Ross procedure. Early prosthetic endocarditis (2) and technical errors (1) were the reasons for early postoperative re-intervention. Neoaortic valve insufficiency (7), including pulmonary valve dysfunction (2), pulmonary valve degeneration (2), pulmonary prosthetic valve endocarditis (1), aortic, pulmonary and mitral valve endocarditis (1) were the reasons for late postoperative re-intervention. Based on the lesion volume, neoaortic valve replacement (3), neoaortic root replacement (6), including pulmonary valve/trunk replacement (8), and pulmonary trunk stenting (2) were performed. Results. In-hospital mortality was 7.1%. One patient died of early endocarditis after primary procedure. The postoperative period for the remaining patients was uneventful. Microscopic examination of the neoaorta revealed fragmentation of elastic fibers and rearrangement of tissue histoarchitectonics. In the pulmonary position, the aortic allograft and stentless xenograft had severe calcification and valve stenosis. Conclusions. Neoaortic valve insufficiency associated with cusp prolapse and neoaortic root dilatation may be the reasons for re-interventions after the Ross procedure. The second reason for re-interventions is valve graft dysfunction in the pulmonary trunk position. Elective reoperations on the neoaortic root and/or lung graft, despite the large volume, can be performed with low mortality and morbidity. Aortic allografts and xenografts for reconstruction of the right ventricular outflow tract (RVOT) is unjustified due to early and more severe dysfunction compared to pulmonary allograft.