The effect of losartan on progressive aortic dilatation in patients with Marfan's syndrome: a meta-analysis of prospective randomized clinical trials

Association of polymorphisms in FBN1, MYH11, and TGF-β signaling-related genes with susceptibility of sporadic thoracic aortic aneurysm and dissection in the Zhejiang Han population

Background

Sporadic thoracic aortic aneurysm and dissection (sTAAD) is a complicated vascular disease with a high mortality rate. And its genetic basis has not been fully explored.

Method

Here, 122 sTAAD patients and 98 healthy individuals were recruited, and 10 single nucleotide polymorphisms were selected and analyzed (FBN1 rs10519177, rs1036477, rs2118181, MYH11 rs115364997, rs117593370, TGFβ1 rs1800469, TGFβ2 rs900, TGFβR2 rs764522, rs1036095, and rs6785385). Moreover, multiple logistic regression analysis was used to evaluate gene-environment interactions.

Results

We identified that TGFβR2 rs1036095 dominant model CC + CG genotype (GT) (P = 0.004) may be a factor of increased risk of sTAAD, especially for women. FBN1 rs1036477 recessive model AA GT (P = 0.009) and FBN1 rs2118181 dominant model CC + CT GT (P = 0.009) were correlated to an increased death rate in sTAAD men patients. Gene-environment interactions indicated TGFβR2 rs1036095 dominant model (CC + CG)/GG to be a higher-risk factor for sTAAD (odds ratio = 3.255; 95% confidence interval: 1.324-8.000, P = 0.01).

Conclusions

TGFβR2 rs1036095, FBN1 rs1036477, and FBN1 rs2118181 were identified as factors of increased risk of sTAAD. Gene-environment interactions were associated with the risk of sTAAD.

Drug-based cardiovascular prevention in patients with Marfan Syndrome: a systematic review

INTRODUCTION

Marfan Syndrome (MFS) is a rare and complex genetic disorder associated with increased aortic growth and aortic disease. The effectiveness of cardiovascular medical therapies aiming to slow down aortic growth has been tested in several trials, particularly beta-blockers and angiotensin receptor blockers, however showing conflicting results.

EVIDENCE ACQUISITION

We conducted a systematic review on PubMed (Medline), Cochrane library, Google Scholar, and Biomed Central databases between January and February 2022. We selected relevant articles focusing on patients with MFS treated with beta-blockers, angiotensin receptors blockers, or both, and reporting data on the effect of the drugs on 1) slowing down aortic dilatation; 2) the reduction of aortic complication (aortic dissection, mortality, aortic surgery); and with a 3) follow-up length of at least two years. A total of 16 studies were selected.

EVIDENCE SYNTHESIS

Beta-blockers remain the mainstay of therapy as they have proven to slow aortic enlargement. Angiotensin receptor blockers are a useful alternative and with proven benefit as an add-on therapy to limit aortic growth. Neither beta-blockers, nor angiotensin receptor blockers have shown meaningful results on clinical aortic endpoints.

CONCLUSIONS

The current evidence of pharmacological treatment for MFS patients is conflicting due to the lack of large, randomized clinical trials with adequate follow-up studies and homogeneous age grouping. Beta-blockers and angiotensin receptor blockers are the only available treatments to reduce aortic growth. A recently published patient-level meta-analysis confirmed that angiotensin receptor blockers and beta-blockers have a similar effect on reducing the rate of increase of the aortic root Z score, used singularly or as add-on therapy. Considering the current evidence on new features related with MFS (such as mitral annular disjunction - MAD) bearing a potential additional increased arrhythmic risk, it is of paramount importance to establish the role of beta-blockers and angiotensin receptor blockers in clinical endpoints of this population as well.

Genetic Basis, New Diagnostic Approaches, and Updated Therapeutic Strategies of the Syndromic Aortic Diseases: Marfan, Loeys-Dietz, and Vascular Ehlers-Danlos Syndrome

Syndromic aortic diseases (SADs) encompass various pathological manifestations affecting the aorta caused by known genetic factors, such as aneurysms, dissections, and ruptures. However, the genetic mutation underlying aortic pathology also gives rise to clinical manifestations affecting other vessels and systems. As a consequence, the main syndromes currently identified as Marfan, Loeys-Dietz, and vascular Ehlers-Danlos are characterized by a complex clinical picture. In this contribution, we provide an overview of the genetic mutations currently identified in order to have a better understanding of the pathogenic mechanisms. Moreover, an update is presented on the basis of the most recent diagnostic criteria, which enable an early diagnosis. Finally, therapeutic strategies are proposed with the goal of improving the rates of patient survival and the quality of life of those affected by these SADs.

Heterogenous improvements in endothelial function by sub-blood pressure lowering doses of ARBs result in major anti-aortic root remodeling effects

Low basal nitric oxide (NO) production is associated with a dysfunctional endothelium and vascular diseases. We have shown that some angiotensin II (AngII) receptor type 1 (AT1R) blockers (ARBs), a group of clinic-approved blood pressure (BP)-lowering medications, are also capable of activating endothelial function acutely and chronically, both ex vivo and in vivo, in pleiotropic, AngII-independent fashions, which suggested that endothelial function enhancement with ARBs may be independent of their well-documented BP lowering properties. Herein, we attempt to identify the most potent ARB at activating endothelial function when administered at sub-BP-lowering doses and determine its anti-aortic root remodeling properties in a model of Marfan syndrome (MFS). Amongst the 8 clinically available ARBs tested, only telmisartan and azilsartan induced significant (70% and 49%, respectively) NO-dependent inhibition of aortic contractility when administered for 4 weeks at sub-BP lowering, EC₅ doses. Low-dose telmisartan (0.47 mg/kg) attenuated MFS-associated aortic root widening, medial thickening, and elastic fiber fragmentation to the same degree as high-dose telmisartan (10 mg/kg) despite wide differences in BP lowering between the two doses. Our study suggests that telmisartan is the most potent ARB at promoting increased endothelial function at low sub-BP doses and that it retained major aortic root widening inhibition activities. ARBs may enhance endothelial function independently from BP-lowering pathways, which could lead to new therapeutic approaches.

The Genetics and Typical Traits of Thoracic Aortic Aneurysm and Dissection

Genetic predisposition and risk factors such as hypertension and smoking can instigate the development of thoracic aortic aneurysm (TAA), which can lead to highly lethal aortic wall dissection and/or rupture. Monogenic defects in multiple genes involved in the elastin-contractile unit and the TGFβ signaling pathway have been associated with TAA in recent years, along with several genetic modifiers and risk-conferring polymorphisms. Advances in omics technology have also provided significant insights into the processes behind aortic wall degeneration: inflammation, epigenetics, vascular smooth muscle phenotype change and depletion, reactive oxygen species generation, mitochondrial dysfunction, and angiotensin signaling dysregulation. These recent advances and findings might pave the way for a therapy that is capable of stopping and perhaps even reversing aneurysm progression.

Angiotensin Receptor Blockers vs. Beta-Blocker Therapy for Marfan Syndrome: A Systematic Review and Meta-Analysis

OBJECTIVE

Several RCTs have been conducted to assess the efficacy and safety of angiotensin receptor blocker (ARB) and beta-blocker (BB) therapy for Marfan syndrome (MFS), but the existing evidence is limited and conflicting. This study aimed to compare the efficacy and safety of different therapies.

APPROACH

The PubMed, Embase, Web of Science, and Cochrane Library databases were electronically searched up to March 2021 to retrieve randomized controlled trials regarding the efficacy and safety of ARB-related (including ARB-only and ARB+BB treatment) and BB-only treatment for treating patients with MFS. The revised risk-of-bias tool was used for quality assessment. The odds ratio (OR) and standard mean difference (SMD) with 95% confidence interval (CI) were used to estimate the pooled effect size.

RESULTS

Fourteen reports of nine trials involving 1,449 patients were included in the meta-analysis. Regarding aortic root dilation, the ARB-related regimen has efficacy comparable with that of the BB-only regimen in patients with MFS (pooled SMD = -0.16, 95% CI [-0.33; 0.01]; p = 0.06), while in the ARB+BB vs. BB-only subgroup, a significant difference was observed (pooled SMD = -0.26; 95% CI [-0.40; -0.11]; p < 0.01). In addition, there were no significant differences in other aortic dilation-related measures (aortic root Z scores, ascending aorta, pulmonary artery, aortic annulus, sinotubular junction, aortic arch, thoracic aorta, and abdominal aorta diameter change) or cardiovascular events (aortic dissection, aortic surgery, and death) between the two regimens.

CONCLUSION

Our results showed that the clinical efficacy of ARB-only therapy is not inferior to that of BB-only therapy. Moreover, ARB+BB therapy showed superior therapeutic effects without significant adverse effects.

Racial and ethnic differences in response to treatment for Marfan syndrome

OBJECTIVE

To determine whether racial/ethnic differences exist for the treatment of Marfan syndrome aortopathy. The 2014 Pediatric Heart Network randomised trial of losartan versus atenolol in Marfan syndrome paediatric and young adult patients showed no treatment differences in the rate of aortic root growth over 3 years; however, they did not examine racial/ethnic differences, and recent data suggest that angiotensin receptor blockers may have different pharmacologic effects in different racial/ethnic populations.

METHODS

We performed a secondary analysis of public-use data from the Pediatric Heart Network randomised trial comparing the differences by race/ethnicity (non-Hispanic White, non-Hispanic Black, and Hispanic patients) amongst the treatment groups for the primary outcome of rate of aortic root enlargement by z score and secondary outcome of rate of change of absolute diameter of aortic root, z score and absolute diameter of ascending aorta, and blood pressure changes.

RESULTS

For aortic root enlargement by z score amongst non-Hispanic White patients, patients on losartan exhibited an annual z score change of -0.090 ± 0.016, compared to -0.146 ± 0.015 for those on atenolol (p = 0.01), favouring atenolol. For Hispanic and non-Hispanic Black patients, there was no difference in primary or secondary outcomes between treatment groups.

CONCLUSION

Non-Hispanic White patients had a small, but statistically significantly greater decrease in aortic root z score favouring atenolol over losartan. There were no significant differences amongst Hispanic or non-Hispanic Black patients, which may be due to relatively small size numbers. These findings may have important implications for medication selection by race/ethnicity in Marfan syndrome patients, which has not previously been evaluated in studies.

Nitric oxide in the Marfan vasculature: Friend or foe?

Marfan syndrome (MFS) is a connective tissue disorder caused by mutations in the FBN1 gene, which encodes fibrillin-1, a protein essential for the formation and stabilization of elastic fibers as well as signaling homeostasis. Progressive aortic root widening is the most serious manifestation of MFS as it can lead to aortic dissection, aneurysm formation and rupture. However, despite their ability to decrease the hemodynamic stress the aorta is subjected to, anti-hypertensive medications often lead to underwhelming reductions in the rate of aortic root dilation, which illustrates how fragmental our understanding of MFS-associated aortic remodeling is. This manuscript summarizes recent evidence that document nitric oxide (NO) synthase (NOS)-related changes to the vasculature during the pathogenesis of MFS and how they result in a unique state of vascular dysfunction that likely plays a causal role in the aortic root widening process. We also review how clinic-approved and experimental therapies as well lifestyle approaches may promote aortic root stability by correcting NO homeostasis, which if properly optimized may improve outcomes in this population afflicted by a notoriously refractory type of aortopathy.

Proof-of-Concept: Antisense Oligonucleotide Mediated Skipping of Fibrillin-1 Exon 52

Marfan syndrome is one of the most common dominantly inherited connective tissue disorders, affecting 2–3 in 10,000 individuals, and is caused by one of over 2800 unique FBN1 mutations. Mutations in FBN1 result in reduced fibrillin-1 expression, or the production of two different fibrillin-1 monomers unable to interact to form functional microfibrils. Here, we describe in vitro evaluation of antisense oligonucleotides designed to mediate exclusion of FBN1 exon 52 during pre-mRNA splicing to restore monomer homology. Antisense oligonucleotide sequences were screened in healthy control fibroblasts. The most effective sequence was synthesised as a phosphorodiamidate morpholino oligomer, a chemistry shown to be safe and effective clinically. We show that exon 52 can be excluded in up to 100% of FBN1 transcripts in healthy control fibroblasts transfected with PMO52. Immunofluorescent staining revealed the loss of fibrillin 1 fibres with ~50% skipping and the subsequent re-appearance of fibres with >80% skipping. However, the effect of exon skipping on the function of the induced fibrillin-1 isoform remains to be explored. Therefore, these findings demonstrate proof-of-concept that exclusion of an exon from FBN1 pre-mRNA can result in internally truncated but identical monomers capable of forming fibres and lay a foundation for further investigation to determine the effect of exon skipping on fibrillin-1 function.

Celiprolol but not losartan improves the biomechanical integrity of the aorta in a mouse model of vascular Ehlers-Danlos syndrome

AIMS

Antihypertensive drugs are included in the medical therapy of vascular Ehlers-Danlos syndrome (vEDS). The β-blocker celiprolol has been suggested to prevent arterial damage in vEDS, but the underlying mechanism remains unclear. It is also unknown whether the widely used angiotensin II receptor type 1 antagonist losartan has a therapeutic effect in vEDS. Here, we evaluated the impact of celiprolol and losartan on the biomechanical integrity of the vEDS thoracic aorta.

METHODS AND RESULTS

We established a new approach to measure the maximum tensile force at rupture of uniaxially stretched murine thoracic aortic rings. In a vEDS model, which we (re-)characterized here at molecular level, heterozygous mice showed a significant reduction in the rupture force compared to wild-type mice, reflecting the increased mortality due to aortic rupture. For the assessment of treatment effects, heterozygous mice at 4 weeks of age underwent a 4-week treatment with celiprolol, losartan, and, as a proof-of-concept drug, the matrix metalloproteinase inhibitor doxycycline. Compared to age- and sex-matched untreated heterozygous mice, treatment with doxycycline or celiprolol resulted in a significant increase of rupture force, whereas no significant change was detected upon losartan treatment.

CONCLUSIONS

In a vEDS model, celiprolol or doxycycline, but not losartan, can improve the biomechanical integrity of the aortic wall, thereby potentially reducing the risk of dissection and rupture. As doxycycline is a broad-spectrum antibiotic with considerable side effects, celiprolol may be more suitable for a long-term therapy and thus rather indicated for the medication of patients with vEDS.

Characterization of doxycycline-mediated inhibition of Marfan syndrome-associated aortic dilation by multiphoton microscopy

Marfan syndrome (MFS) is a connective tissue disorder that results in aortic root widening and aneurysm if unmanaged. We have previously reported doxycycline, a nonselective matrix metalloproteinases (MMPs) inhibitor, to attenuate aortic root widening and improve aortic contractility and elasticity in MFS mice. We were also first to use multiphoton microscopy, a non-invasive and label-free imaging technique, to quantify and link the aortic ultrastructure to possible changes in the skin dermis. Here, we aimed to assess the effects of long-term doxycycline treatment on the aortic ultrastructure and skin dermis of MFS mice through immunohistochemical evaluation and quantification of elastic and collagen content and morphology using multiphoton microscopy. Our results demonstrate a rescue of aortic elastic fiber fragmentation and disorganization accompanied by a decrease in MMP-2 and MMP-9 expression within the aortic wall in doxycycline-treated MFS mice. At 12 months of age, reduced skin dermal thickness was observed in both MFS and control mice, but only dermal thinning in MFS mice was rescued by doxycycline treatment. MMP-2 and MMP-9 expression was reduced in the skin of doxycycline-treated MFS mice. A decrease in dermal thickness was found to be positively associated with increased aortic root elastin disorganization and wall thickness. Our findings confirm the beneficial effects of doxycycline on ultrastructural properties of aortic root as well as on skin elasticity and structural integrity in MFS mice.

Losartan for Preventing Aortic Root Dilatation in Patients with Marfan Syndrome: A Meta-Analysis of Randomized Trials

INTRODUCTION

The role of losartan in preventing aortic root dilatation in Marfan syndrome has been evaluated in many clinical trials; however, the results are conflicting.

METHODS

We performed a computerized search of MEDLINE, EMBASE and COCHRANE databases through February 2019 for randomized clinical trials evaluating the effect of losartan in patients with Marfan syndrome. The main outcome was the change in the aortic root diameter in the losartan versus control groups.

RESULTS

Our final analysis included seven randomized trials with a total of 1352 patients and average weighted follow-up of 37.8 months. Change in aortic root diameter was significantly smaller with losartan compared with control [weighted means: 0.44 vs. 0.58 mm, mean difference (MD) = -0.13; 95% CI -0.24 to -0.02; p = 0.02]. Subgroup analysis according to the control group showed no significant subgroup interaction when comparing losartan with beta-blockers versus with standard therapy (pinteraction= 0.27). The composite outcome of aortic surgery, dissection or mortality did not differ between the losartan and control groups (risk ratio = 1.03; 95% CI 0.72-1.49, p = 0.86).

CONCLUSION

In this meta-analysis including seven randomized trials, the use of losartan was associated with a significantly smaller change in aortic root diameter in patients with Marfan syndrome.

Accelerated Marfan syndrome model recapitulates established signaling pathways

OBJECTIVE

Marfan syndrome (MFS) represents a genetic disorder with a range of clinical features, including proximal aortic aneurysms. Extensive research has revealed an abundance of transforming growth factor beta from a mutation in fibrillin-1 to be the key biochemical mechanism of aneurysm formation. Many important signaling pathways downstream of transforming growth factor beta have been further characterized. Our laboratory has previously demonstrated a unique murine model of MFS resulting in the accelerated formation of ascending aortic aneurysms and dilated cardiomyopathies. This study aims to characterize the relevance of this model to known signaling mechanisms in MFS.

METHODS

Fibrillin 1C^1039G/+ heterozygous mice (ie, MFS), with a mutation in fibrillin-1, were supplemented with 4.5 mg/kg/d angiotensin II to accelerate aneurysm formation. Four mouse groups were analyzed: wild type with or without angiotensin II and MFS with or without angiotensin II. Aortic tissue from these samples were subjected to western blotting and phosphoimaging to query various signaling pathways.

RESULTS

Mice with MFS displayed downstream regulation in both the canonical (Smad2) and noncononical (extracellular signal-regulated kinases and P38) pathways characteristic of MFS. However, these downstream signals were exaggerated in the MFS mice supplemented with angiotensin II (accelerated model), matching the observed phenotypic severity of this model.

CONCLUSIONS

The murine MFS model depicted here accelerates ascending aortic aneurysm formation and cardiomyopathies via well-characterized MFS signaling cascades. The mechanistic relevance of the accelerated murine MFS model suggests that it could be an important tool in future studies hoping to characterize MFS signaling in an expedited experimental design.

The effects of losartan versus beta-blockers on cardiovascular protection in marfan syndrome: A systematic review and meta-analysis

BACKGROUND AND PURPOSE

Variable effects of beta-blockers (BB) and/or angiotensin receptor blockers (ARB) were reported to retard aortic root growth in Marfan syndrome (MFS). This study aimed to compare the effects of BB therapy and ARB-related therapies on cardiovascular protection in MFS.

METHODS

Studies of randomized control trials comparing the efficacy of only-BB and ARB-related (only-ARB or ARB-plus-BB) therapies for MFS published before July 31, 2018 in PubMed, Embase, and the Cochrane Library were selected. The outcomes included changes in aortic growth and cardiovascular events.

RESULTS

Eight trials involving 1381 patients were included. Patients received only-BB and ARB-related therapies did not differ significantly in changes in aortic growth (aortic root diameter: standardized mean difference [SMD] = 0.04, 95% confidence interval [CI]: -0.11-0.19, p = 0.63) or cardiovascular events (aortic dissection: Peto odds ratio [OR] = 1.67, 95% CI: 0.42-6.72, p = 0.47; aortic surgery: risk ratio = 0.97, 95% CI: 0.66-1.41, p = 0.86; death: Peto OR = 2.78, 95% CI: 0.39-19.82, p = 0.31). Subgroup analysis revealed that ARB-plus-BB therapy exhibited nonsignificantly better outcomes than only-BB therapy (aortic root diameter: SMD = 0.11, 95% CI: -0.22-0.45, p = 0.52; ascending aorta diameter: SMD = 0.10, 95% CI: -0.07-0.27, p = 0.26; aortic surgery: Peto OR = 1.10, 95% CI: 0.75-1.61, p = 0.62).

CONCLUSION

For cardiovascular protection in MFS, only-ARB therapy is not inferior to only-BB therapy. Moreover, the outcomes of ARB-plus-BB therapy seemed to be favourable to those of only-BB therapy.

Pharmacologic Management of Aneurysms

Current management of aortic aneurysms relies exclusively on prophylactic operative repair of larger aneurysms. Great potential exists for successful medical therapy that halts or reduces aneurysm progression and hence alleviates or postpones the need for surgical repair. Preclinical studies in the context of abdominal aortic aneurysm identified hundreds of candidate strategies for stabilization, and data from preoperative clinical intervention studies show that interventions in the pathways of the activated inflammatory and proteolytic cascades in enlarging abdominal aortic aneurysm are feasible. Similarly, the concept of pharmaceutical aorta stabilization in Marfan syndrome is supported by a wealth of promising studies in the murine models of Marfan syndrome-related aortapathy. Although some clinical studies report successful medical stabilization of growing aortic aneurysms and aortic root stabilization in Marfan syndrome, these claims are not consistently confirmed in larger and controlled studies. Consequently, no medical therapy can be recommended for the stabilization of aortic aneurysms. The discrepancy between preclinical successes and clinical trial failures implies shortcomings in the available models of aneurysm disease and perhaps incomplete understanding of the pathological processes involved in later stages of aortic aneurysm progression. Preclinical models more reflective of human pathophysiology, identification of biomarkers to predict severity of disease progression, and improved design of clinical trials may more rapidly advance the opportunities in this important field.

In vivo characterization of doxycycline-mediated protection of aortic function and structure in a mouse model of Marfan syndrome-associated aortic aneurysm

Aortic aneurysm is the most life-threatening complication in Marfan syndrome (MFS) patients. Doxycycline, a nonselective matrix metalloproteinases inhibitor, was reported to improve the contractile function and elastic fiber structure and organization in a Marfan mouse aorta using ex vivo small chamber myography. In this study, we assessed the hypothesis that a long-term treatment with doxycycline would reduce aortic root growth, improve aortic wall elasticity as measured by pulse wave velocity, and improve the ultrastructure of elastic fiber in the mouse model of MFS. In our study, longitudinal measurements of aortic root diameters using high-resolution ultrasound imaging display significantly decreased aortic root diameters and lower pulse wave velocity in doxycycline-treated Marfan mice starting at 6 months as compared to their non-treated MFS counterparts. In addition, at the ultrastructural level, our data show that long-term doxycycline treatment corrects the irregularities of elastic fibers within the aortic wall of Marfan mice to the levels similar to those observed in control subjects. Our findings underscore the key role of matrix metalloproteinases during the progression of aortic aneurysm, and provide new insights into the potential therapeutic value of doxycycline in blocking MFS-associated aortic aneurysm.

The transition of pediatric Marfan patients to adult care: a challenge and its risks

Background

Care for patients with Marfan syndrome (MFS) has improved substantially in recent decades. Increasing clinical knowledge and genetic analysis allow early diagnosis of the disease in childhood. Because of the earlier initiation to preventive and medical treatment, patients' life expectancy has risen. To ensure optimal care, pediatric patients require a safe follow-up regime, multidisciplinary care, and a safe transition to adult care.

Methods

We collected a sample of 149 pediatric Marfan patients, of whom 34 patients had already been transferred to adult care or who were currently transitioning. First, we evaluated clinical aspects of patients that manifest in childhood and are present in the transition process. Second, we analyzed the transition process itself.

Results

We found age-dependent manifestation of organ pathologies. Dilatation of the sinus of Valsalva showed a particularly high prevalence during the transition process and 62% of patients required medical treatment. Mean onset of aortic root dilatation was 9.9±5.8 years. Concerning systemic manifestation in MFS skin striae, wrist and thumb sign, and reduced elbow extension occurred significantly more often in patients who were transitioning than in younger children with MFS. All other clinical Marfan features showed an increased prevalence in patients who were transitioning compared with younger patients. In our cohort, transition was successful in 20 patients (58.9%), 12 patients (35.3%) are still in the transition process and 2 patients (5.9%) were lost to follow up.

Conclusions

Marfan patients in the transition process are already under a chronic disease condition with a high onset of especially cardiovascular pathologies. Although early medical treatment in childhood is effective, the pathologies of the connective tissue require lifelong attention and influence life in many ways. The big challenge during transition is the double change of responsibility from the parents and pediatric doctor to the patient and adult doctor. Consequently, patients in transition process require special attention and close contact with the doctor and the family. A reevaluation by the supervising pediatric Marfan specialist of the successful transition to adult care is indispensable before the pediatric care of Marfan patients is completed.

Medical management of aortic disease in children with Marfan syndrome

PURPOSE OF REVIEW

Marfan syndrome (MFS) is the most common cause of aortic aneurysm in children and is associated with premature mortality. Whereas surgical therapy remains the primary treatment to prevent aortic complications, medical therapy may slow or prevent aortic growth. Pediatricians and pediatric cardiologists should become familiar with the diagnosis and management of MFS. This review focuses on the medical management for the most important life-threatening manifestation of MFS, thoracic aortic disease.

RECENT FINDINGS

Several large-scale clinical trials and one meta-analysis have been reported comparing angiotensin receptors blockers with the standard therapy, beta blockers.

SUMMARY

From the assembled evidence described in this review, beta blockers and angiotensin receptors blockers show clinical equivalence and either class of agent may be an appropriate choice for the medical management of aortic growth in children with MFS.

Precise Therapy for Thoracic Aortic Aneurysm in Marfan Syndrome: A Puzzle Nearing Its Solution

Marfan Syndrome (MFS) is a rare connective tissue disorder, resulting from mutations in the fibrillin-1 gene, characterized by pathologic phenotypes in multiple organs, the most detrimental of which affects the thoracic aorta. Indeed, thoracic aortic aneurysms (TAA), leading to acute dissection and rupture, are today the major cause of morbidity and mortality in adult MFS patients. Therefore, there is a compelling need for novel therapeutic strategies to delay TAA progression and counteract aortic dissection occurrence. Unfortunately, the wide phenotypic variability of MFS patients, together with the lack of a complete genotype-phenotype correlation, have represented until now a barrier hampering the conduction of translational studies aimed to predict disease prognosis and drug discovery. In this review, we will illustrate available therapeutic strategies to improve the health of MFS patients. Starting from gold standard surgical overtures and the description of the main pharmacological approaches, we will comprehensively review the state-of-the-art of in vivo MFS models and discuss recent clinical pharmacogenetic results. Finally, we will focus on induced pluripotent stem cells (iPSC) as a technology that, if integrated with preclinical research and pharmacogenetics, could contribute in determining the best therapeutic approach for each MFS patient on the base of individual differences. Finally, we will suggest the integration of preclinical studies, pharmacogenetics and iPSC technology as the most likely strategy to help solve the composite puzzle of precise medicine in this condition.

TGF-β Signaling-Related Genes and Thoracic Aortic Aneurysms and Dissections

Transforming growth factor-β (TGF)-β signaling plays a crucial role in the development and maintenance of various organs, including the vasculature. Accordingly, the mutations in TGF-β signaling pathway-related genes cause heritable disorders of the connective tissue, such as Marfan syndrome (MFS), Loeys-Dietz syndrome (LDS), and Shprintzen-Goldberg syndrome (SGS), and these syndromes may affect skeletal, ocular, pulmonary, and cardiovascular systems. Aortic root aneurysms are common problems that can result in aortic dissection or rupture, which is the leading cause of sudden death in the natural history of MFS and LDS, and recent improvements in surgical treatment have improved life expectancy. However, there is currently no genotype-specific medical treatment. Accumulating evidence suggest that not only structural weakness of connective tissue but also increased TGF-β signaling contributes to the complicated pathogenesis of aortic aneurysm formation, but a comprehensive understanding of governing molecular mechanisms remains lacking. Inhibition of angiotensin II receptor signaling and endothelial dysfunction have gained attention as a possible MFS treatment strategy, but interactions with TGF-β signaling remain elusive. Heterozygous loss-of-function mutations in TGF-β receptors 1 and 2 (TGFBR1 and TGFBR2) cause LDS, but TGF-β signaling is activated in the aorta (referred to as the TGF-β paradox) by mechanisms yet to be elucidated. In this review, we present and discuss the current understanding of molecular mechanisms responsible for aortopathies of MFS and related disorders.

Isolated aortic root dilation in homocystinuria

BACKGROUND

Vascular complications in homocystinuria have been known for many years, but there have been no reports to date on involvement of the ascending aorta.

METHODS

We conducted a cross-sectional study of patients with homocystinuria, known to a single metabolic centre, and evaluated in 2016 with a transthoracic echocardiogram. Aortic root dilation was defined as Z-score ≥ 2.0 SD, and graded mild (Z-score 2.0-3.0), moderate (Z-score 3.01-4.0) and severe (Z-score > 4.0).

RESULTS

The study population included 34 patients, median age of 44.3 years (IQR 33.3-52.2), 50% males, 69% diagnosed aged <18 years and 29% pyridoxine-responsive. Eight (24%) had a history of hypertension. Seven patients (21%) were found to have a dilation of the aortic root, mild in two cases (6%), moderate in four (12%) and severe in one (3%). None had dilation of the ascending aorta. Significant aortic regurgitation, secondary to moderate aortic root dilation, was documented in two patients. A single patient had significant mitral regurgitation due to prolapse of both valve leaflets, as well as mild aortic root dilation. Comparing patients with a dilation of the aortic root to those without, there were no significant clinical, laboratory or echocardiographic differences, with the only exception being that the diameter of the ascending aorta was larger in the group with a dilated aortic root, albeit within normal limits.

CONCLUSIONS

A subset of patients with homocystinuria have isolated dilation of the aortic root similar to that observed in Marfan syndrome.

Efficacy of losartan as add-on therapy to prevent aortic growth and ventricular dysfunction in patients with Marfan syndrome: a randomized, double-blind clinical trial

BACKGROUND

Marfan syndrome (MFS) is a multisystemic hereditary connective tissue disease. Aortic root aneurysms and dissections are the most common and life-threatening cardiovascular disorders affecting these patients. Other cardiac manifestations include mitral valve prolapse, ventricular dysfunction and arrhythmias. Medical treatment of cardiovascular features is ultimately aimed at slowing down aortic root growth rate and preventing dissection. Losartan has been proposed as a new therapeutic tool for this purpose. To which extent losartan affects cardiac function has not been studied previously.

METHODS

We designed a prospective, double-blind, randomized placebo-controlled trial to evaluate the effect of losartan added to beta-blocker therapy on aortic growth and ventricular function in patients with MFS. Secondary outcomes were aortic dissection, prophylactic aortic surgery and death.

RESULTS

Twenty-two patients were enrolled in the trial. There was a mild and similar increase in the aortic root during the 3 years of follow-up in both groups (median 1 mm, IQR [-1-1.5] and 1 mm, IQR [-0.25-1] in the losartan and placebo group, respectively, p = 1). Diastolic and systolic ventricular function was normal at baseline in both groups and remained stable during the study. One patient in the placebo group presented a subclavian artery dissection during follow-up.

CONCLUSION

Losartan on top of beta-blocker therapy has no additional effect on aortic growth or on cardiac function in patients with MFS. Our results are underpowered but are in line with the result from other groups. In order to have a better insight on whether a group of patients could benefit more from losartan therapy, the outcome of an on-going meta-analysis should be awaited.

Thoracic Aortic Aneurysm Development in Patients with Bicuspid Aortic Valve: What Is the Role of Endothelial Cells?

Bicuspid aortic valve (BAV) is the most common type of congenital cardiac malformation. Patients with a BAV have a predisposition for the development of thoracic aortic aneurysm (TAA). This pathological aortic dilation may result in aortic rupture, which is fatal in most cases. The abnormal aortic morphology of TAAs results from a complex series of events that alter the cellular structure and extracellular matrix (ECM) composition of the aortic wall. Because the major degeneration is located in the media of the aorta, most studies aim to unravel impaired smooth muscle cell (SMC) function in BAV TAA. However, recent studies suggest that endothelial cells play a key role in both the initiation and progression of TAAs by influencing the medial layer. Aortic endothelial cells are activated in BAV mediated TAAs and have a substantial influence on ECM composition and SMC phenotype, by secreting several key growth factors and matrix modulating enzymes. In recent years there have been significant advances in the genetic and molecular understanding of endothelial cells in BAV associated TAAs. In this review, the involvement of the endothelial cells in BAV TAA pathogenesis is discussed. Endothelial cell functioning in vessel homeostasis, flow response and signaling will be highlighted to give an overview of the importance and the under investigated potential of endothelial cells in BAV-associated TAA.

Endovascular treatment of genetically linked aortic diseases

Background

The most important structural proteins of the vascular wall are collagen and elastin. Genetically linked connective tissue diseases lead to degeneration, aneurysm formation and spontaneous dissection or rupture of arteries. The most well-known are Marfan syndrome, vascular Ehlers-Danlos syndrome (type IV), Loeys-Dietz syndrome and familial aortic aneurysms and dissections.

Objective

This review article addresses the current status of endovascular treatment options for important connective tissue diseases.

Material and methods

Evaluation of currently available randomized studies and registry data.

Results

The treatment of choice for patients that are mostly affected at a young age is primarily conservative or open repair. There is only limited evidence for endovascular aortic repair (EVAR) of abdominal aneurysms or thoracic endovascular aortic repair (TEVAR).

Conclusion

The progression of the disease with dilatation leads to secondary endoleaks and high reintervention rates with uncertain long-term results. For this reason, there is currently consensus that EVAR and TEVAR should be limited to justified exceptional cases and emergency situations in patients with genetically linked aortic diseases.