Mutations in myosin heavy chain 11 cause a syndrome associating thoracic aortic aneurysm/aortic dissection and patent ductus arteriosus

Cardiovascular manifestations in men and women carrying a FBN1 mutation

AIMS

In patients with Marfan syndrome and other type-1 fibrillinopathies, genetic testing is becoming more easily available, leading to the identification of mutations early in the course of the disease. This study evaluates the cardiovascular (CV) risk associated with the discovery of a fibrillin-1 (FBN1) mutation.

METHODS AND RESULTS

A total of 1,013 probands with pathogenic FBN1 mutations were included, among whom 965 patients [median age: 22 years (11-34), male gender 53%] had data suitable for analysis. The percentage of patients with an ascending aortic (AA) dilatation increased steadily with increasing age and reached 96% (95% CI: 94-97%) by 60 years. The presence of aortic events (dissection or prophylactic surgery) was rare before 20 years and then increased progressively, reaching 74% (95% CI: 67-81%) by 60 years. Compared with women, men were at higher risk for AA dilatation [≤ 30 years: 57% (95% CI: 52-63) vs. 50% (95% CI: 45-55), P = 0.0076] and aortic events [≤ 30 years: 21% (95% CI: 17-26) vs. 11% (95% CI: 8-16), P < 0.0001; adjusted HR: 1.4 (1.1-1.8), P = 0.005]. The prevalence of mitral valve (MV) prolapse [≤ 60 years: 77% (95% CI: 72-82)] and MV regurgitation [≤ 60 years: 61% (95% CI: 53-69)] also increased steadily with age, but surgery limited to the MV remained rare [≤ 60 years: 13% (95% CI: 8-21)]. No difference between genders was observed (for all P> 0.20). From 1985 to 2005 the prevalence of AA dilatation remained stable (P for trend = 0.88), whereas the percentage of patients with AA dissection significantly decreased (P for trend = 0.01).

CONCLUSION

The CV risk remains important in patients with an FBN1 gene mutation and is present throughout life, justifying regular aortic monitoring. Aortic dilatation or dissection should always trigger suspicion of a genetic background leading to thorough examination for extra-aortic features and comprehensive pedigree investigation.

Genetic factors in non-syndromic congenital heart malformations

The genetic defect in most patients with non-syndromic congenital heart malformations (CHM) is unknown, although more than 40 different genes have already been implicated. Only a minority of CHM seems to be due to monogenetic mutations, and the majority occurs sporadically. The multifactorial inheritance hypothesis of common diseases suggesting that the cumulative effect of multiple genetic and environmental risk factors leads to disease, might also apply for CHM. We review here the monogenic disease genes with high-penetrance mutations, susceptibility genes with reduced-penetrance mutations, and somatic mutations implicated in non-syndromic CHM.

Canadian Cardiovascular Society 2009 Consensus Conference on the management of adults with congenital heart disease: outflow tract obstruction, coarctation of the aorta, tetralogy of Fallot, Ebstein anomaly and Marfan's syndrome

With advances in pediatric cardiology and cardiac surgery, the population of adults with congenital heart disease (CHD) has increased. In the current era, there are more adults with CHD than children. This population has many unique issues and needs. Since the 2001 Canadian Cardiovascular Society Consensus Conference report on the management of adults with CHD, there have been significant advances in the field of adult CHD. Therefore, new clinical guidelines have been written by Canadian adult CHD physicians in collaboration with an international panel of experts in the field. Part II of the guidelines includes recommendations for the care of patients with left ventricular outflow tract obstruction and bicuspid aortic valve disease, coarctation of the aorta, right ventricular outflow tract obstruction, tetralogy of Fallot, Ebstein anomaly and Marfan's syndrome. Topics addressed include genetics, clinical outcomes, recommended diagnostic workup, surgical and interventional options, treatment of arrhythmias, assessment of pregnancy risk and follow-up requirements. The complete document consists of four manuscripts that are published online in the present issue of The Canadian Journal of Cardiology. The complete document and references can also be found at www.ccs.ca or www.cachnet.org.

Histopathology of an iliac aneurysm in a case of Menkes disease

In Menkes disease, arterial tortuosity is frequent, whereas true aneurysms are rare. Here, we report aneurysmal pathology occurring in an infant with Menkes disease. An iliac aneurysm was diagnosed in a 2-month-old boy and attributed to Menkes syndrome on the basis of plasma copper deficiency. Samples of the aneurysmal wall were taken during surgery for histopathological analysis. As in other forms of aneurysm, the arterial wall was characterized by smooth muscle cell (SMC) disappearance, linked to SMC apoptosis and oxidative stress, areas of mucoid degeneration, and extracellular matrix breakdown, including disappearance of elastic fibers and presence of abnormal collagen.

FBN1 mutations in patients with descending thoracic aortic dissections

Aortic aneurysm and dissection cause significant morbidity and mortality. There are several known single gene disorders that predispose to isolated aortic disease and eventually aneurysm and dissection. FBN1 mutations are associated with multiple clinical phenotypes, including Marfan syndrome (MFS), MASS phenotype, and familial ectopia lentis, but rarely with isolated aortic aneurysm and dissection. In this report, we describe three patients who presented with primary descending thoracic aortic dissection and who were found to have an FBN1 mutation. None of the patients fulfilled clinical criteria for the diagnosis of MFS, and all had few or none of the skeletal features typical of the condition. Two patients had a history of long-term hypertension, and such a history was suspected in the third patient. These observations suggest that some individuals with FBN1 mutations have significant aortic disease involvement of other systems that is typical of FBN1 mutation-related syndromes. Superimposed risk factors, such as hypertension, may weaken the aortic wall and eventually lead to aortic dissection. Given that the cost continues to decrease, we suggest that diagnostic DNA sequencing for FBN1 mutations in patients with thoracic aortic aneurysms and dissection may be a practical clinical step in evaluating such patients and at-risk family members.

Marfan syndrome. Part 1: pathophysiology and diagnosis

Marfan syndrome is a connective-tissue disease inherited in an autosomal dominant manner and caused mainly by mutations in the gene FBN1. This gene encodes fibrillin-1, a glycoprotein that is the main constituent of the microfibrils of the extracellular matrix. Most mutations are unique and affect a single amino acid of the protein. Reduced or abnormal fibrillin-1 leads to tissue weakness, increased transforming growth factor beta signaling, loss of cell-matrix interactions, and, finally, to the different phenotypic manifestations of Marfan syndrome. Since the description of FBN1 as the gene affected in patients with this disorder, great advances have been made in the understanding of its pathogenesis. The development of several mouse models has also been crucial to our increased understanding of this disease, which is likely to change the treatment and the prognosis of patients in the coming years. Among the many different clinical manifestations of Marfan syndrome, cardiovascular involvement deserves special consideration, owing to its impact on prognosis. However, the diagnosis of patients with Marfan syndrome should be made according to Ghent criteria and requires a comprehensive clinical assessment of multiple organ systems. Genetic testing can be useful in the diagnosis of selected cases.

Genetic analysis of young adult patients with aortic disease not fulfilling the diagnostic criteria for Marfan syndrome

BACKGROUND

Although the existence of the young patients with aortic disease not fulfilling the diagnostic criteria for Marfan syndrome (MFS) has been known, the etiology of their disease has not yet been elucidated. The purpose of the present study was to elucidate the genetic and clinical features of the young patients with aortic disease not having MFS.

METHODS AND RESULTS

Eighty young adult patients with aortic disease were examined. They were divided into a definite MFS (n=51) and a non-definite MFS group (n=29) according to the Ghent nosology. Clinical and genetic characteristics were compared between the 2 groups. Among 29 non-definite MFS probands, 1 (3%) FBN1, 2 (7%) TGFBR1, and 3 (10%) TGFBR2 mutations were found, and 4 ACTA2 mutations were found in the 23 probands examined without FBN1, TGFBR1, or TGFBR2 mutations. In total, more than 10 out of 29 (34%) probands in the non-definite MFS group were associated with genetic mutations. Skeletal involvement was less frequent in the non-definite than in the definite MFS group (7% vs 82%, P<0.01).

CONCLUSIONS

In the probands with aortic diseases in young who cannot be diagnosed with MFS, mutations other than FBN1 mutations accounted for at least one-third of all causes of aortic disease.

Fibulin-4 deficiency results in ascending aortic aneurysms: a potential link between abnormal smooth muscle cell phenotype and aneurysm progression

RATIONALE

Loss of fibulin-4 during embryogenesis results in perinatal lethality because of aneurysm rupture, and defective elastic fiber assembly has been proposed as an underlying cause for the aneurysm phenotype. However, aneurysms are never seen in mice deficient for elastin, or for fibulin-5, which absence also leads to compromised elastic fibers.

OBJECTIVE

We sought to determine the mechanism of aneurysm development in the absence of fibulin-4 and establish the role of fibulin-4 in aortic development.

METHODS AND RESULTS

We generated germline and smooth muscle cell (SMC)-specific deletion of the fibulin-4 gene in mice (Fbln4(GKO) and Fbln4(SMKO), respectively). Fbln4(GKO) and Fbln4(SMKO) aortic walls fail to fully differentiate, exhibiting reduced expression of SM-specific contractile genes and focal proliferation of SMCs accompanied by degenerative changes of the medial wall. Marked upregulation of extracellular signal-regulated kinase 1/2 signaling pathway was observed in the aneurysmal wall of Fbln4(GKO) and Fbln4(SMKO) mice and both mutants developed aneurysm predominantly in the ascending thoracic aorta. In vitro, Fbln4(GKO) SMCs exhibit an immature SMC phenotype with a marked reduction of SM-myosin heavy chain and increased proliferative capacity.

CONCLUSIONS

The vascular phenotype in Fbln4 mutant mice is remarkably similar to a subset of human thoracic aortic aneurysms caused by mutations in SMC contractile genes. Our study provides a potential link between the intrinsic properties of SMCs and aneurysm progression in vivo and supports the dual role of fibulin-4 in the formation of elastic fibers as well as terminal differentiation and maturation of SMCs in the aortic wall.

Mutation of ACTA2 gene as an important cause of familial and nonfamilial nonsyndromatic thoracic aortic aneurysm and/or dissection (TAAD)

Approximately 20% of aortic aneurysm and/or dissection (AAD) cases result from inherited disorders, including several systemic and syndromatic connective-tissue disorders, such as Marfan syndrome, Ehlers-Danlos syndrome, and Loeys-Dietz syndrome, which are caused by mutations in the FBN1, COL3A1, and TGFBR1 and TGFBR2 genes, respectively. Nonsyndromatic AAD also has a familial background, and mutations of the ACTA2 gene were recently shown to cause familial AAD. In the present study, we conducted sequence analyses of the ACTA2 gene in 14 unrelated Japanese patients with familial thoracic AAD (TAAD), and in 26 with sporadic and young-onset TAAD. Our results identified three mutations of ACTA2, two novel [p.G152_T205del (c.616+1G>T), p.R212Q] and one reported (p.R149C), in the 14 patients with familial TAAD, and a novel mutation (p.Y145C) of ACTA2 in the 26 sporadic and young-onset TAAD patients, each of which are considered to be causative for TAAD. Some of the clinical features of these patients were the same as previously reported, whereas others were different. These findings confirm that ACTA2 mutations are important in familial TAAD, while the first sporadic and young-onset TAAD case with an ACTA2 mutation was also identified.

Proteomic profiling of medial degeneration in human ascending aorta

OBJECTIVE

The objective of this study was the construction of a reference map for aortic medial degeneration by a proteomic approach.

DESIGN AND METHODS

A proteomic profiling of the media of human ascending aorta was performed by two-dimensional electrophoresis and MALDI-TOF mass spectrometry.

RESULTS

A reliable protocol for two-dimensional electrophoresis analysis of human aortic media proteins was developed allowing the selection and identification of 52 spots. Protein identifications revealed that the predominant vascular smooth muscle cell proteins isolated from grade 1 aortic medial degeneration (MD) included proteins involved in muscle contraction, protein folding, cytoskeletal structure and metabolic processes, and those with antioxidant or transport functions. The most populated functional classes were those related to muscle contraction and cytoskeletal proteins, including actin, calmodulin, calponin, myosin light chain, tropomyosin, vimentin, profilin and transgelin.

CONCLUSIONS

The obtained aortic MD proteomic profile provides a relevant background for future studies aimed to find further specific molecular changes potentially related to the aortic MD process.

Identification of vasculature-specific genes by microarray analysis of Etsrp/Etv2 overexpressing zebrafish embryos

Signaling pathways controlling vasculogenesis, angiogenesis, and myelopoiesis are still poorly understood, in part because not all genes important for vasculature or myeloid cell formation have been characterized. To identify novel potential regulators of vasculature and myeloid cell formation we performed microarray analysis of zebrafish embryos that overexpress Ets1-related protein (Etsrp/Etv2/ER71), sufficient to induce vasculogenesis and myelopoiesis (Sumanas and Lin [2006] Development 121:3141-3150; Lee [2008] Cell Stem Cell 2:497-507; Sumanas et al. [2008] Blood 111:4500-4510). We performed sequence homology and expression analysis for up-regulated genes that were novel or previously unassociated with the zebrafish vasculature formation. Angiotensin II type 2 receptor (agtr2), src homology 2 domain containing E (she), mannose receptor C1 (mrc1), endothelial cell-specific adhesion molecule (esam), yes-related kinase (yrk/fyn), zinc finger protein, multitype 2b (zfpm2b/fog2b), and stabilin 2 (stab2) were specifically expressed in vascular endothelial cells during early development while keratin18 expression was localized to the myeloid cells. Identification of vasculature and myeloid-specific genes will be important for dissecting molecular mechanisms of vasculogenesis/angiogenesis and myelopoiesis.

Surgical treatment of patients enrolled in the national registry of genetically triggered thoracic aortic conditions

BACKGROUND

Genetic disorders are an important cause of thoracic aortic aneurysms (TAAs) in young patients. Despite advances in the treatment of genetically triggered TAAs, the optimal syndrome-specific treatment approach remains undefined. We used data from the National Institutes of Health-funded, multicenter National Registry of Genetically Triggered Thoracic Aortic Aneurysms and Cardiovascular Conditions (GenTAC) to characterize the contemporary surgical treatment of patients with genetically triggered TAAs.

METHODS

GenTAC's aim is to collect longitudinal clinical data and banked biospecimens from 2800 patients with genetically triggered TAAs. We analyzed data from the 606 patients (mean age, 37.5 years) enrolled in GenTAC to date whose clinical data were available.

RESULTS

The patients' primary diagnoses included Marfan syndrome (35.8%), bicuspid aortic valve with aneurysm (29.2%), and familial TAAs and dissections (10.7%). Of these, 56.4% had undergone at least one operation; the most common indications were aneurysm (85.7%), valve dysfunction (65.8%), and dissection (25.4%). Surgical procedures included replacement of the aortic root (50.6%), ascending aorta (64.8%), aortic arch (27.9%), and descending or thoracoabdominal aorta (12.4%). Syndrome-specific differences in age, indications for operation, and procedure type were identified.

CONCLUSIONS

Patients with genetically transmitted TAAs evaluated in tertiary care centers frequently undergo surgical repair. Aneurysm repairs most commonly involve the aortic root and ascending aorta; distal repairs are less common. Like TAAs themselves, complications of TAAs, including dissection and aortic valve dysfunction, are important indications for intervention. Future studies will focus on syndrome- and gene-specific phenotypes, biomarkers, treatments, and outcomes to improve the treatment of patients with TAAs.

Syndromic and non-syndromic aneurysms of the human ascending aorta share activation of the Smad2 pathway

Common features such as elastic fibre destruction, mucoid accumulation, and smooth muscle cell apoptosis are co-localized in aneurysms of the ascending aorta of various aetiologies. Recent experimental studies reported an activation of TGF-beta in aneurysms related to Marfan (and Loeys-Dietz) syndrome. Here we investigate TGF-beta signalling in normal and pathological human ascending aortic wall in syndromic and non-syndromic aneurysmal disease. Aneurysmal ascending aortic specimens, classified according to aetiology: syndromic MFS (n = 15, including two mutations in TGFBR2), associated with BAV (n = 15) or degenerative forms (n = 19), were examined. We show that the amounts of TGF-beta1 protein retained within and released by aneurysmal tissue were greater than for control aortic tissue, whatever the aetiology, contrasting with an unchanged TGF-beta1 mRNA level. The increase in stored TGF-beta1 was associated with enhanced LTBP-1 protein and mRNA levels. These dysregulations of the extracellular ligand are associated with higher phosphorylated Smad2 and Smad2 mRNA levels in the ascending aortic wall from all types of aneurysm. This activation correlated with the degree of elastic fibre fragmentation. Surprisingly, there was no consistent association between the nuclear location of pSmad2 and extracellular TGF-beta1 and LTBP-1 staining and between their respective mRNA expressions. In parallel, decorin was focally increased in aneurysmal media, whereas biglycan was globally decreased in aneurysmal aortas. In conclusion, this study highlights independent dysregulations of TGF-beta retention and Smad2 signalling in syndromic and non-syndromic aneurysms of the ascending aorta.

Extracellular microfibrils: contextual platforms for TGFbeta and BMP signaling

The extracellular matrix plays a key role in organ formation and tissue homeostasis. Recent studies have revealed that fibrillin assemblies (microfibrils) confer both tissue integrity and regulate signaling events that instruct cell performance and that perturbation of either function manifests in disease. These analyses have also indicated that fibrillin assemblies impart contextual specificity to TGFbeta and BMP signaling. Moreover, correlative evidence suggests functional coupling between cell-directed assembly of microfibrils and targeting of TGFbeta and BMP complexes to fibrillins. Hence, the emerging view is that fibrillin-rich microfibrils are molecular integrators of structural and instructive signals with TGFbetas and BMPs as nodal points that convert extracellular inputs into discrete and context-dependent cellular responses.

Determination of genetic predisposition to patent ductus arteriosus in preterm infants

OBJECTIVE

Patent ductus arteriosus is a common morbidity associated with preterm birth. The incidence of patent ductus arteriosus increases with decreasing gestational age to approximately 70% in infants born at 25 weeks' gestation. Our major goal was to determine if genetic risk factors play a role in patent ductus arteriosus seen in preterm infants.

METHODOLOGY

We investigated whether single-nucleotide polymorphisms in genes that regulate smooth muscle contraction, xenobiotic detoxification, inflammation, and other processes are markers for persistent patency of ductus arteriosus. Initially, 377 single-nucleotide polymorphisms from 130 genes of interest were evaluated in DNA samples collected from 204 infants with a gestational age of <32 weeks. A family-based association test was performed on genotyping data to evaluate overtransmission of alleles.

RESULTS

P values of <.01 were detected for genetic variations found in 7 genes. This prompted additional analysis with an additional set of 162 infants, focusing on the 7 markers with initial P values of <.01, and 1 genetic variant in the angiotensin II type I receptor previously shown to be related to patent ductus arteriosus. Of the initial positive signals, single-nucleotide polymorphisms in the transcription factor AP-2 beta and tumor necrosis factor receptor-associated factor 1 genes remained significant. Additional haplotype analysis revealed genetic variations in prostacyclin synthase to be associated with patent ductus arteriosus. An angiotensin II type I receptor polymorphism previously reported to be associated with patent ductus arteriosus after prophylactic indomethacin administration was not associated with the presence of a patent ductus arteriosus in our population.

CONCLUSIONS

Overall, our data support a role for genetic variations in transcription factor AP-2 beta, tumor necrosis factor receptor-associated factor 1, and prostacyclin synthase in the persistent patency of the ductus arteriosus seen in preterm infants.

Rationale and design of the National Registry of Genetically Triggered Thoracic Aortic Aneurysms and Cardiovascular Conditions (GenTAC)

BACKGROUND

Although the management of thoracic aortic aneurysms (TAAs) has improved significantly, patients presenting with aortic dissections, rupture, or other acute complications of TAAs continue to have high rates of morbidity and mortality. Accumulating data have indicated that many TAAs are due to underlying gene mutations. A comprehensive approach to the study of TAAs resulting from genetic mutations is needed to translate this information into advances in treatment.

OBJECTIVE

The National Registry of Genetically Triggered Thoracic Aortic Aneurysms and Cardiovascular Conditions (GenTAC) was established to provide a biospecimen inventory and bioinformatics infrastructure to enable research to advance the clinical management of genetically triggered TAAs and related complications.

METHODS

GenTAC is a longitudinal observational cohort study enrolling patients with conditions related to genetically induced TAAs from 5 regional clinical centers in the United States.

RESULTS

More than 700 subjects with associated clinical histories, physical examinations, imaging data, and biospecimens have been enrolled in the Registry to date. Enrollment is expected to continue until September 2010. Total enrollment of nearly 3,000 subjects is expected. No interim analysis has yet been undertaken.

CONCLUSIONS

GenTAC has been established to facilitate studies by GenTAC investigators and others that will advance multiple scientific frontiers in thoracic aortic disease. Genotypic, proteomic, clinical, and imaging data will be integrated systematically with outcomes data to determine the optimal clinical management of patients with genetically induced TAAs.

Assessment of arterial stiffness, a translational medicine biomarker system for evaluation of vascular risk

AIMS

Stiffening of the large arteries is a common feature of aging and is exacerbated by a number of disorders such as hypertension, diabetes, and renal disease. Arterial stiffening is recognized as an important and independent risk factor for cardiovascular events. This article will provide a comprehensive review of the recent advance on assessment of arterial stiffness as a translational medicine biomarker for cardiovascular risk.

DISCUSSIONS

The key topics related to the mechanisms of arterial stiffness, the methodologies commonly used to measure arterial stiffness, and the potential therapeutic strategies are discussed. A number of factors are associated with arterial stiffness and may even contribute to it, including endothelial dysfunction, altered vascular smooth muscle cell (SMC) function, vascular inflammation, and genetic determinants, which overlap in a large degree with atherosclerosis. Arterial stiffness is represented by biomarkers that can be measured noninvasively in large populations. The most commonly used methodologies include pulse wave velocity (PWV), relating change in vessel diameter (or area) to distending pressure, arterial pulse waveform analysis, and ambulatory arterial stiffness index (AASI). The advantages and limitations of these key methodologies for monitoring arterial stiffness are reviewed in this article. In addition, the potential utility of arterial stiffness as a translational medicine surrogate biomarker for evaluation of new potentially vascular protective drugs is evaluated.

CONCLUSIONS

Assessment of arterial stiffness is a sensitive and useful biomarker of cardiovascular risk because of its underlying pathophysiological mechanisms. PWV is an emerging biomarker useful for reflecting risk stratification of patients and for assessing pharmacodynamic effects and efficacy in clinical studies.

[Pathobiology of idiopathic ascending aortic aneurysms]

BACKGROUND

The majority of ascending aortic aneurysms cannot be related to any specific etiology and should be qualified as idiopathic. The incidence of this disease is increasing in the population of the developed countries but its pathobiology is poorly understood.

AIM

This article is reviewing the publications concerning the pathobiology of idiopathic ascending aortic aneurysms.

SOURCES

A PubMed search on articles published in English or French, between January 1965 and December 2007, on key-words << aortic root >>, << ascending aorta >>, << aortic arch >>, << thoracic aorta >>, << aneurysm >>, << dilatation >> and << dissection >> was undertaken. Articles on aneurysms related to inflammatory and infectious diseases, congenital or genetic syndromes were excluded.

RESULTS

The presented data suggests that destructive remodeling of the aortic wall, inflammation and angiogenesis, biomechanical wall stress, and molecular genetics are relevant mechanisms of idiopathic ascending aortic aneurysm formation and progression.

LIMITS

Sparse data available from few direct studies offer limited knowledge on pathobiology of idiopathic ascending aortic aneurysms.

CONCLUSION

A more intimate knowledge of the triggers and perpetrating factors of this disease might offer new diagnostic and treatment options.

Surgical pathology of chronic ascending aortic dissections

AIMS

A majority of aortic dissections affect the ascending aorta and are acute in nature. Chronic dissections in this region are uncommon. This report characterises the clinicopathological features of 15 non-iatrogenic chronic ascending aortic dissections.

METHODS

Among 65 patients who had surgery for ascending aortic dissection over a period of 6 years, 15 showed morphological evidence of chronic dissection. Clinical data and morphological features of these were analysed.

RESULTS

Twelve patients (80%) were over the age of 50 years, with a male predominance (11 patients, 73.33%). Exertional dyspnoea was the most common presenting symptom, while chest pain was noted in three cases. An echocardiographic diagnosis of dissection was made in six patients. The disease was restricted to the ascending aorta in nine (60%) and all had aortic regurgitation of varying severity. Areas of recent dissection were also noted in three specimens. The risk factors or pathogenetic mechanisms noted were hypertension in four and Marfan's syndrome, penetrating atherosclerotic ulcer, patent ductus arteriosus, and vehicular accident, in one patient each. The aortic segment of the latter patient had shown intimal flaps to be associated with multiple saucer-shaped depressions with thin walls. These features were also noted in two of the seven patients without risk factors and in two hypertensives. This raises the possibility of subclinical intimal injury sustained during sudden deceleration with blunt chest trauma. Significant aortopathy was seen in 10 cases.

CONCLUSIONS

Chronic dissections as a cause of aortic regurgitation and aneurysmal dilatation, especially in the elderly, should be kept in mind. This may follow sudden deceleration intimal injuries, superimposed on aged-related medial degeneration.

Transforming growth factor-beta signaling in thoracic aortic aneurysm development: a paradox in pathogenesis

Thoracic aortic aneurysms (TAAs) are potentially devastating, and due to their asymptomatic behavior, pose a serious health risk characterized by the lack of medical treatment options and high rates of surgical morbidity and mortality. Independent of the inciting stimuli (biochemical/mechanical), TAA development proceeds by a multifactorial process influenced by both cellular and extracellular mechanisms, resulting in alterations of the structure and composition of the vascular extracellular matrix (ECM). While the role of enhanced ECM proteolysis in TAA formation remains undisputed, little attention has been focused on the upstream signaling events that drive the remodeling process. Recent evidence highlighting the dysregulation of transforming growth factor-beta (TGF-beta) signaling in ascending TAAs from Marfan syndrome patients has stimulated an interest in this intracellular signaling pathway. However, paradoxical discoveries have implicated both enhanced TGF-beta signaling and loss of function TGF-beta receptor mutations, in aneurysm formation; obfuscating a clear functional role for TGF-beta in aneurysm development. In an effort to elucidate this subject, TGF-beta signaling and its role in vascular remodeling and pathology will be reviewed, with the aim of identifying potential mechanisms of how TGF-beta signaling may contribute to the formation and progression of TAA.

Effects of prenatal tobacco exposure on gene expression profiling in umbilical cord tissue

Maternal smoking doubles the risk of delivering a low birth weight infant. The purpose of this study was to analyze differential gene expression in umbilical cord tissue as a function of maternal smoking, with an emphasis on growth-related genes. We recruited 15 pregnant smokers and 15 women who never smoked during pregnancy to participate. RNA was isolated from umbilical cord tissue collected and snap frozen at the time of delivery. Microarray analysis was performed using the Affymetrix GeneChip Scanner 3000. Six hundred seventy-eight probes corresponding to 545 genes were differentially expressed (i.e. had an intensity ratio > +/- 1.3 and a corrected significance value p < 0.005) in tissue obtained from smokers versus nonsmokers. Genes important for fetal growth, angiogenesis, or development of connective tissue matrix were upregulated among smokers. The most highly upregulated gene was CSH1, a somatomammotropin gene. Two other somatomammotropin genes (CSH2 and CSH-L1) were also upregulated. The most highly downregulated gene was APOBEC3A; other downregulated genes included those that may be important in immune and barrier protection. Validation of the three somatomammotropin genes showed a high correlation between qPCR and microarray expression. We conclude that maternal smoking may be associated with altered gene expression in the offspring.

Genetic factors in congenital heart malformation

Congenital heart disease is the commonest malformation in humans and contributes greatly to the burden of disease in infancy. Increasingly, developmental origins are also implicated in heart disease in adults. Significant advances have been made over the past decade in elucidating morphogenetic events of heart formation and their underlying molecular cascades, mostly in animal models. Clinical studies are increasingly successful in quantifying and unraveling genetic factors. This review focuses on recent progress made in understanding the genetic underpinnings of normal and abnormal heart formation and highlights the importance of understanding these mechanisms to improve patient management.

Unregulated smooth-muscle myosin in human intestinal neoplasia

A recent study described a recessive ATPase activating germ-line mutation in smooth-muscle myosin (smmhc/myh11) underlying the zebrafish meltdown (mlt) phenotype. The mlt zebrafish develops intestinal abnormalities reminiscent of human Peutz-Jeghers syndrome (PJS) and juvenile polyposis (JP). To examine the role of MYH11 in human intestinal neoplasia, we searched for MYH11 mutations in patients with colorectal cancer (CRC), PJS and JP. We found somatic protein-elongating frameshift mutations in 55% of CRCs displaying microsatellite instability and in the germ-line of one individual with PJS. Additionally, two somatic missense mutations were found in one microsatellite stable CRC. These two missense mutations, R501L and K1044N, and the frameshift mutations were functionally evaluated. All mutations resulted in unregulated molecules displaying constitutive motor activity, similar to the mutant myosin underlying mlt. Thus, MYH11 mutations appear to contribute also to human intestinal neoplasia. Unregulated MYH11 may affect the cellular energy balance or disturb cell lineage decisions in tumor progenitor cells. These data challenge our view on MYH11 as a passive differentiation marker functioning in muscle contraction and add to our understanding of intestinal neoplasia.

Differential response of human fetal smooth muscle cells from arterial duct to retinoid acid

AIM

The aim of the present study was to understand the role of retinoic acid (RA) in the development of isolated patent ductus arteriosus and the features of arterial duct-derived vascular smooth muscle cells (VSMC).

METHODS

The VSMC were isolated, and the biological characteristics and the response to RA were investigated in the arterial duct, aorta, and pulmonary artery VSMC from 6 human embryonic samples. Western blotting, immunostaining, and cell-based ELISA were employed to analyze the proliferation regulation of VSMC.

RESULTS

The VSMC from the arterial duct expressed proliferating cell nuclear antigen (PCNA) at a significantly lower rate than those from the aorta and pulmonary artery, but expressed a higher level of Bax and Bcl-2. The expression level of PCNA or Bcl-2 was associated with the embryonic age. The effects of RA on the VSMC from the arterial duct were quite different from those from the aorta and pulmonary artery. In arterial duct VSMC, RA stimulated PCNA expression, but such stimulation could be suppressed by CD2366, an antagonist of nuclear retinoid receptor activation. In aorta or pulmonary artery VSMC, the expression response of PCNA to RA was insignificant. The ratio of Bax/Bcl-2 decreased in arterial duct VSMC after RA treatment due to the significant inhibition of Bax expression.

CONCLUSION

The VSMC from the arterial duct possessed distinct biological behaviors. RA might be important in the development of ductus arteriosus VSMC.

Myocardin regulates expression of contractile genes in smooth muscle cells and is required for closure of the ductus arteriosus in mice

Myocardin (Myocd) is a potent transcriptional coactivator that has been implicated in cardiovascular development and adaptation of the cardiovascular system to hemodynamic stress. To determine the function of myocardin in the developing cardiovascular system, Myocd(F/F)/Wnt1-Cre(+) and Myocd(F/F)/Pax3-Cre(+) mice were generated in which the myocardin gene was selectively ablated in neural crest-derived SMCs populating the cardiac outflow tract and great arteries. Both Myocd(F/F)/Wnt1-Cre(+) and Myocd(F/F)/Pax3-Cre(+) mutant mice survived to birth, but died prior to postnatal day 3 from patent ductus arteriosus (PDA). Neural crest-derived SMCs populating the ductus arteriosus (DA) and great arteries exhibited a cell autonomous block in expression of myocardin-regulated genes encoding SMC-restricted contractile proteins. Moreover, Myocd-deficient vascular SMCs populating the DA exhibited ultrastructural features generally associated with the SMC synthetic, rather than contractile, phenotype. Consistent with these findings, ablation of the Myocd gene in primary aortic SMCs harvested from Myocd conditional mutant mice caused a dramatic decrease in SMC contractile protein expression. Taken together, these data demonstrate that myocardin regulates expression of genes required for the contractile phenotype in neural crest-derived SMCs and provide new insights into the molecular and genetic programs that may underlie PDA.

Dilation-dependent activation of platelets and prothrombin in human thoracic ascending aortic aneurysm

OBJECTIVE

The purpose of this study was to investigate whether thoracic ascending aortic aneurysm (TAAA) induces platelet activation as mural thrombus participates in aortic dilatation in abdominal aortic aneurysm and TAAA are associated with rheological factors favoring coagulation activation.

METHODS AND RESULTS

We studied the relation between coagulation activation and aortic diameter in Marfan patients (MFS) with various aortic diameters (n=52). We then studied patients presenting large aneurysms associated with bicuspid aortic valve (BAV) and degenerative form. Lastly, we used immunochemistry and biochemistry to investigate prothrombin/thrombin retention within the aortic wall. Microparticles, sGPV, tissue factor, and TAT complexes were increased in plasma from MFS with large aneurysms (>or=45 mm) compared to MFS with limited aortic dilatation (<45 mm). Similar elevations were observed in all patients with large aortic aneurysms, regardless of the etiology, the site of maximal aortic dilation, associated valvulopathy, risk factors, or treatments. P-selectin and platelet-bound fibrinogen were also increased, demonstrating platelet activation in large aneurysms. Significant increase in sCD146 plasma concentration suggested alteration of endothelium.

CONCLUSIONS

Platelet activation occurs in patients with large aneurysms of the ascending aorta, is dependent on aortic dilation, and is associated with thrombin generation, part of which appears to be retained in mucoid degeneration areas.