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Aortic aneurysm is common, accounting for 1–2% of all deaths in industrialized countries. Early theories of the causes of human aneurysm mostly focused on inherited or acquired defects in components of the extracellular matrix in the aorta. Although several mutations in the genes encoding extracellular matrix proteins have been recognized, more recent discoveries have shown important perturbations in cytokine signalling cascades and intracellular components of the smooth muscle contractile apparatus. The modelling of single-gene heritable aneurysm disorders in mice has shown unexpected involvement of the transforming growth factor-β cytokine pathway in aortic aneurysm, highlighting the potential for new therapeutic strategies.

Murine studies suggest that aortic-root dilation in Marfan's syndrome is due to excessive signaling by transforming growth factor β (TGF-β) and can be mitigated by TGF-β antagonists, such as angiotensin II–receptor blockers (ARBs). This study reviewed data on 18 pediatric patients with Marfan's syndrome who had begun ARB therapy and had been followed for at least 12 months. The rate of increase in aortic-root diameter was significantly slowed after the initiation of ARB therapy. This study reviewed data on pediatric patients with Marfan's syndrome who had begun ARB therapy. The rate of increase in aortic-root diameter was significantly slowed after the initiation of ARB therapy. Marfan's syndrome, an autosomal dominant connective-tissue disorder affecting approximately 1 in 5000 people, is caused by mutations in the gene encoding fibrillin-1 ( FBN1 ). 1 , 2 FBN1 mutations lead to defects in multiple organ systems, of which the most life-threatening is progressive enlargement and dissection of the aortic root. 3 , 4 Current medical management of Marfan's syndrome is focused on serial cardiac-imaging studies and the use of pharmacologic agents to reduce hemodynamic stress on the aortic wall. Pharmacologic treatment often involves the use of beta-adrenergic–receptor antagonists (beta-blockers), although other agents, such as angiotensin-converting–enzyme (ACE) inhibitors and calcium-channel blockers, have been used . . .

TGF-β is essential for vascular development; however, excess TGF-β signaling promotes thoracic aortic aneurysm and dissection in multiple disorders, including Marfan syndrome. Since the pathology of TGF-β overactivity manifests primarily within the arterial media, it is widely assumed that suppression of TGF-β signaling in vascular smooth muscle cells will ameliorate aortic disease. We tested this hypothesis by conditional inactivation of Tgfbr2, which encodes the TGF-β type II receptor, in smooth muscle cells of postweanling mice. Surprisingly, the thoracic aorta rapidly thickened, dilated, and dissected in these animals. Tgfbr2 disruption predictably decreased canonical Smad signaling, but unexpectedly increased MAPK signaling. Type II receptor-independent effects of TGF-β and pathological responses by nonrecombined smooth muscle cells were excluded by serologic neutralization. Aortic disease was caused by a perturbed contractile apparatus in medial cells and growth factor production by adventitial cells, both of which resulted in maladaptive paracrine interactions between the vessel wall compartments. Treatment with rapamycin restored a quiescent smooth muscle phenotype and prevented dissection. Tgfbr2 disruption in smooth muscle cells also accelerated aneurysm growth in a murine model of Marfan syndrome. Our data indicate that basal TGF-β signaling in smooth muscle promotes postnatal aortic wall homeostasis and impedes disease progression.

Despite significant research efforts, clinical practice for arterial bypass surgery has been stagnant, and engineered grafts continue to face postimplantation challenges. Here, we describe the development and application of a durable small-diameter vascular graft with tailored regenerative capacity. We fabricated small-diameter vascular grafts by electrospinning fibrin tubes and poly(ε-caprolactone) fibrous sheaths, which improved suture retention strength and enabled long-term survival. Using surface topography in a hollow fibrin microfiber tube, we enable immediate, controlled perfusion and formation of a confluent endothelium within 3–4 days in vitro with human endothelial colony-forming cells, but a stable endothelium is noticeable at 4 weeks in vivo. Implantation of acellular or endothelialized fibrin grafts with an external ultrathin poly(ε-caprolactone) sheath as an interposition graft in the abdominal aorta of a severe combined immunodeficient Beige mouse model supports normal blood flow and vessel patency for 24 weeks. Mechanical properties of the implanted grafts closely approximate the native abdominal aorta properties after just 1 week in vivo. Fibrin mediated cellular remodeling, stable tunica intima and media formation, and abundant matrix deposition with organized collagen layers and wavy elastin lamellae. Endothelialized grafts evidenced controlled healthy remodeling with delayed and reduced macrophage infiltration alongside neo vasa vasorum-like structure formation, reduced calcification, and accelerated tunica media formation. Our studies establish a small-diameter graft that is fabricated in less than 1 week, mediates neotissue formation and incorporation into the native tissue, and matches the native vessel size and mechanical properties, overcoming main challenges in arterial bypass surgery.

Failure of integrin-mediated cell-matrix attachment is sufficient to initiate dermal fibrosis and autoimmunity in mouse models of scleroderma; integrin-modulating therapies prevent the recruitment and activation of plasmacytoid dendritic cells that appear central to immunological dysregulation and maintenance of the pro-fibrotic synthetic programme. Scleroderma pathogenesis and treatment Stiff skin syndrome, a form of scleroderma characterized by fibrosis of the skin, is caused by mutations in the integrin binding region of fibrillin-1. Harry Dietz and colleagues have developed a genetically engineered mouse model of stiff skin syndrome and show that mouse lines that harbour analogous amino acid substitutions in fibrillin-1 recapitulate aggressive skin fibrosis, and that this can be prevented by integrin-modulating therapies and reversed by antagonism of the pro-fibrotic cytokine transforming growth factor β (TGF-β). This work demonstrates that it is possible to reverse established dermal fibrosis, and suggests several therapeutic strategies including β 1 integrin activation and blockade of signalling by β 2 integrin, TGF-β or ERK. In systemic sclerosis (SSc), a common and aetiologically mysterious form of scleroderma (defined as pathological fibrosis of the skin), previously healthy adults acquire fibrosis of the skin and viscera in association with autoantibodies 1 . Familial recurrence is extremely rare and causal genes have not been identified. Although the onset of fibrosis in SSc typically correlates with the production of autoantibodies, whether they contribute to disease pathogenesis or simply serve as a marker of disease remains controversial and the mechanism for their induction is largely unknown 2 . The study of SSc is hindered by a lack of animal models that recapitulate the aetiology of this complex disease. To gain a foothold in the pathogenesis of pathological skin fibrosis, we studied stiff skin syndrome (SSS), a rare but tractable Mendelian disorder leading to childhood onset of diffuse skin fibrosis with autosomal dominant inheritance and complete penetrance. We showed previously that SSS is caused by heterozygous missense mutations in the gene ( FBN1 ) encoding fibrillin-1, the main constituent of extracellular microfibrils 3 . SSS mutations all localize to the only domain in fibrillin-1 that harbours an Arg-Gly-Asp (RGD) motif needed to mediate cell–matrix interactions by binding to cell-surface integrins 3 . Here we show that mouse lines harbouring analogous amino acid substitutions in fibrillin-1 recapitulate aggressive skin fibrosis that is prevented by integrin-modulating therapies and reversed by antagonism of the pro-fibrotic cytokine transforming growth factor β (TGF-β). Mutant mice show skin infiltration of pro-inflammatory immune cells including plasmacytoid dendritic cells, T helper cells and plasma cells, and also autoantibody production; these findings are normalized by integrin-modulating therapies or TGF-β antagonism. These results show that alterations in cell–matrix interactions are sufficient to initiate and sustain inflammatory and pro-fibrotic programmes and highlight new therapeutic strategies.

Loeys–Dietz syndrome is a connective tissue disorder predisposing individuals to aortic and arterial aneurysms. Presenting with a wide spectrum of multisystem involvement, medical management for some individuals is complex. This review of literature and expert opinion aims to provide medical guidelines for care of individuals with Loeys–Dietz syndrome. Genet Med 16 8, 576–587.

Angiotensin II (AngII) mediates progression of aortic aneurysm, but the relative contribution of its type 1 (AT1) and type 2 (AT2) receptors remains unknown. We show that loss of AT2 expression accelerates the aberrant growth and rupture of the aorta in a mouse model of Marfan syndrome (MFS). The selective AT1 receptor blocker (ARB) losartan abrogated aneurysm progression in the mice; full protection required intact AT2 signaling. The angiotensin-converting enzyme inhibitor (ACEi) enalapril, which limits signaling through both receptors, was less effective. Both drugs attenuated canonical transforming growth factor—β (TGFβ) signaling in the aorta, but losartan uniquely inhibited TGFβ-mediated activation of extracellular signal—regulated kinase (ERK), by allowing continued signaling through AT2. These data highlight the protective nature of AT2 signaling and potentially inform the choice of therapies in MFS and related disorders.

COVID-19 infection and vaccination have been reported to confer an elevated risk for cardiovascular events (CVE). We sought to determine whether individuals with an underlying vascular connective tissue disorder including Marfan syndrome (MFS), Loeys-Dietz syndrome (LDS), or vascular Ehlers Danlos syndrome (vEDS) are at increased risk for cardiac events after COVID-19 infection or vaccination. 325 respondents self-reported data through a cross-sectional, web-based survey available from 22 November 2021, through 15 March 2022 regarding COVID-19 illness and vaccinations, the occurrence of any CVE, and adverse events following vaccination. The data were analyzed using a Cox proportional hazards model with time varying indicators for COVID-19 illness/vaccination in the preceding 30 days. COVID-19 illness was significantly associated with an increased rate of a new abnormal heart rhythm 30 days following infection. No other CVEs were reported in the 90 days after COVID-19 illness. We did not find evidence of an increased rate of any CVE in the 30 days following any COVID-19 vaccination dose. In respondents with MFS, LDS, or vEDS, we uncovered no evidence of an increase in CVEs in the 30 days following COVID-19 illness, with the possible exception of dysrhythmia. In light of the absence of a substantial increase in self-reported CVEs in the 30 days following COVID-19 vaccination, these data are in keeping with the recommendation from the Marfan Foundation Professional Advisory Board that all eligible persons be vaccinated for COVID-19.

Collagen remodeling is an integral part of tissue development, maintenance, and regeneration, but excessive remodeling is associated with various pathologic conditions. The ability to target collagens undergoing remodeling could lead to new diagnostics and therapeutics as well as applications in regenerative medicine; however, such collagens are often degraded and denatured, making them difficult to target with conventional approaches. Here, we present caged collagen mimetic peptides (CMPs) that can be photo-triggered to fold into triple helix and bind to collagens denatured by heat or by matrix metalloproteinase (MMP) digestion. Peptide-binding assays indicate that the binding is primarily driven by stereo-selective triple-helical hybridization between monomeric CMPs of high triple-helical propensity and denatured collagen strands. Photo-triggered hybridization allows specific staining of collagen chains in protein gels as well as photo-patterning of collagen and gelatin substrates. In vivo experiments demonstrate that systemically delivered CMPs can bind to collagens in bones, as well as prominently in articular cartilages and tumors characterized by high MMP activity. We further show that CMP-based probes can detect abnormal bone growth activity in a mouse model of Marfan syndrome. This is an entirely new way to target the microenvironment of abnormal tissues and could lead to new opportunities for management of numerous pathologic conditions associated with collagen remodeling and high MMP activity.

Hypermobile Ehlers-Danlos syndrome is a heritable connective tissue disorder associated with generalized joint hypermobility but also other multisystem comorbidities, many of which may be exacerbated during a viral illness or after a vaccination. We sought to determine whether individuals with hypermobile Ehlers Danlos syndrome report an increase in adverse events, including cardiovascular events, after COVID-19 illness or vaccination. A cross-sectional web-based survey was made available from November 22, 2021, through March 15, 2022. 368 respondents primarily from the United States self-reported data including diagnosis. We used a Cox proportional hazards model with time varying indicators for COVID-19 illness or vaccination in the previous 30 days. We found a significantly increased rate of new abnormal heart rhythms reported in the 30 days following COVID-19 illness. No additional cardiovascular events were reported after COVID-19 illness. 2.5% of respondents with COVID-19 illness were hospitalized. We did not find a statistically significant increased rate of cardiovascular events in the 30 days following any COVID-19 vaccination dose. Post COVID-19 vaccination, 87.2% of hypermobile Ehlers-Danlos syndrome respondents endorsed an expected adverse event (EAE), and 3.1% reported an emergency department visit/hospitalization, of those who received at least one vaccine dose. Events possibly reflecting exacerbation of orthostasis/dysautonomia were common. Respondents did not report an increased rate of any cardiovascular events in the 30 days following COVID-19 vaccination; however, those with hypermobile Ehlers-Danlos syndrome experienced a high rate of expected adverse events after vaccination consistent with a high baseline prevalence of similar symptoms. No cardiovascular events other than new abnormal heart rhythms were reported at any point after a COVID-19 illness.