Aortic root smooth muscle cells (SMC) develop from both the second heart field (SHF) and neural crest. Disparate responses to disease-causing
variants by these lineages are proposed to promote focal ...aortic root aneurysm formation in Marfan syndrome (MFS), but lineage-stratified SMC analysis in vivo is lacking.
We generated SHF lineage-traced MFS mice and performed integrated multiomic (single-cell RNA and assay for transposase-accessible chromatin sequencing) analysis stratified by embryological origin. SMC subtypes were spatially identified via RNA in situ hybridization. Response to
overexpression was determined via lentiviral transduction in human aortic SMCs.
Lineage stratification enabled nuanced characterization of aortic root cells. We identified heightened SHF-derived SMC heterogeneity including a subset of
(cardiac troponin T)-expressing cells distinguished by altered proteoglycan expression. MFS aneurysm-associated SMC phenotypic modulation was identified in both SHF-traced and nontraced (neural crest-derived) SMCs; however, transcriptomic responses were distinct between lineages. SHF-derived modulated SMCs overexpressed collagen synthetic genes and small leucine-rich proteoglycans while nontraced SMCs activated chondrogenic genes. These modulated SMCs clustered focally in the aneurysmal aortic root at the region of SHF/neural crest lineage overlap. Integrated RNA-assay for transposase-accessible chromatin analysis identified enriched
and
complex binding motifs in SHF-derived modulated SMCs. TWIST1 overexpression promoted collagen and
gene expression in vitro, suggesting TWIST1 may drive SHF-enriched collagen synthesis in MFS aneurysm.
SMCs derived from both SHF and neural crest lineages undergo phenotypic modulation in MFS aneurysm but are defined by subtly distinct transcriptional responses. Enhanced TWIST1 transcription factor activity may contribute to enriched collagen synthetic pathways SHF-derived SMCs in MFS.
Gene mutations in the extracellular matrix protein fibrillin-1 cause connective tissue disorders including Marfan syndrome (MFS) with clinical symptoms in the cardiovascular, skeletal, and ocular ...systems. Patients with MFS also exhibit alterations in adipose tissues, which in some individuals leads to lipodystrophy, whereas in others to obesity. We have recently demonstrated that fibrillin-1 regulates adipose tissue homeostasis. Here, we examined how fibrillin-1 abnormality affects metabolic adaptation to different diets. We used two MFS mouse models: hypomorph
mice and
mice with a fibrillin-1 missense mutation. When
mice were fed with high-fat diet (HFD) for 12 wk, male mice were heavier than littermate controls (LCs), whereas female mice gained less weight compared with LCs. Female
mice on an HFD for 24 wk were similarly protected from weight gain. Male
mice on an HFD demonstrated higher insulin levels, insulin intolerance, circulating levels of cholesterol, and high-density lipoproteins. Moreover, male HFD-fed
mice showed a higher liver weight and a fatty liver phenotype, which was reduced to LC levels after orchiectomy. Phosphorylation of protein kinase-like endoplasmic reticulum kinase (PERK) and the expression of sterol regulatory element-binding protein 1 (
) in livers of HFD-fed male
mice were elevated. In conclusion, the data demonstrate that male mice of both the MFS models are susceptible to HFD-induced obesity and diabetes. Moreover, male
mice develop a fatty liver phenotype, likely mediated by a baseline increased endoplasmic reticulum stress. In contrast, female MFS mice were protected from the consequence of HFD.
Abstract Background In many cardiac units, aortic valve-sparing operations have become the preferred surgical procedure to treat aortic root aneurysm in patients with Marfan syndrome, based on ...relatively short-term outcomes. Objectives This study examined the long-term outcomes of aortic valve-sparing operations in patients with Marfan syndrome. Methods All patients with Marfan syndrome operated on for aortic root aneurysm from 1988 through 2012 were followed prospectively for a median of 10 years. Follow-up was 100% complete. Time-to-event analyses were calculated using the Kaplan-Meier method with log-rank test for comparisons. Results A total of 146 patients with Marfan syndrome had aortic valve-sparing operations. Reimplantation of the aortic valve was performed in 121 and remodeling of the aortic root was performed in 25 patients. Mean age was 35.7 ± 11.4 years and two-thirds were men. Nine patients had acute, 2 had chronic type A, and 3 had chronic type B aortic dissections before surgery. There were 1 operative and 6 late deaths, 5 caused by complications of dissections. Mortality rate at 15 years was 6.8 ± 2.9%, higher than the general population matched for age and sex. Five patients required reoperation on the aortic valve: 2 for endocarditis and 3 for aortic insufficiency. Three patients developed severe, 4 moderate, and 3 mild-to-moderate aortic insufficiency. Rate of aortic insufficiency at 15 years was 7.9 ± 3.3%, lower after reimplantation than remodeling. Nine patients developed new distal aortic dissections during follow-up. Rate of dissection at 15 years was 16.5 ± 3.4%. Conclusions Aortic valve-sparing operations in patients with Marfan syndrome were associated with low rates of valve-related complications in long-term follow-up. Residual and new aortic dissections were the leading cause of death.
The fibrillins, large extracellular matrix molecules, are polymerized to form “microfibrils.” The fibrillin microfibril scaffold is populated by microfibril-associated proteins and by growth factors, ...which are likely to be latent. The scaffold, associated proteins, and bound growth factors, together with cellular receptors that can sense the microfibril matrix, constitute the fibrillin microenvironment. Activation of TGFβ signaling is associated with the Marfan syndrome, which is caused by mutations in fibrillin-1. Today we know that mutations in fibrillin-1 cause the Marfan syndrome as well as Weill-Marchesani syndrome (and other acromelic dysplasias) and result in opposite clinical phenotypes: tall or short stature; arachnodactyly or brachydactyly; joint hypermobility or stiff joints; hypomuscularity or hypermuscularity. We also know that these different syndromes are associated with different structural abnormalities in the fibrillin microfibril scaffold and perhaps with specific cellular receptors (mechanosensors). How does the microenvironment, framed by the microfibril scaffold and populated by latent growth factors, work? We must await future investigations for the molecular and cellular mechanisms that will answer this question. However, today we can appreciate the importance of the fibrillin microfibril niche as a contextual environment for growth factor signaling and potentially for mechanosensation.
•The fibrillin microenvironment consists of a fibrillin microfibril scaffold, associated microfibril proteins, bound growth factors, and cells that interact with this microenvironment.•Studies in human and mouse indicate that fibrillins control TGFβ and BMP signaling.•Genetic evidence from the fibrillinopathies demonstrate that fibrillins control musculoskeletal growth.•Genetic disorders are associated with distinct structural abnormalities in fibrillin microfibrils and with distinct cellular receptors that can sense the fibrillin microenvironment.•The fibrillin microfibril niche provides an important contextual environment for growth factor signaling and potentially for mechanosensation.
To optimize care for children with Marfan syndrome (MFS) in the Netherlands, Dutch MFS growth charts were constructed. Additionally, we aimed to investigate the effect of FBN1 variant type ...(haploinsufficiency HI/dominant negative DN) on growth, and compare MFS‐related height increase across populations. Height and weight data of individuals with MFS aged 0–21 years were retrospectively collected. Generalized Additive Models for Location, Scale and Shape (GAMLSS) was used for growth chart modeling. To investigate genotype–phenotype relationships, FBN1 variant type was included as an independent variable in height‐for‐age and BMI‐for‐age models. MFS‐related height increase was compared with that of previous MFS growth studies from the United States, Korea, and France. Height and weight data of 389 individuals with MFS were included (210 males). Height‐for‐age, BMI‐for‐age, and weight‐for‐height charts reflected the tall and slender MFS habitus throughout childhood. Mean increase in height of individuals with MFS compared with the general Dutch population was significantly lower than in the other three MFS populations compared to their reference populations. FBN1‐HI variants were associated with taller height in both sexes, and decreased BMI in females (p‐values <0.05). This Dutch MFS growth study broadens the notion that genetic background and MFS variant type (HI/DN) influence tall and slender stature in MFS.
Marfan syndrome (MFS) is a connective tissue disorder affecting the cardiovascular, ocular, and skeletal system, which may be accompanied by psychological features. This study aimed to determine the ...prevalence of fatigue, anxiety, and symptoms of depression in MFS patients, and to assess the degree to which sociodemographic and clinical variables are associated with fatigue and psychological aspects. The prevalence of fatigue, anxiety, and symptoms of depression were assessed in two cohorts of MFS patients and compared with healthy controls. The checklist individual strength (CIS), and hospital anxiety and depression scale (HADS) questionnaires were utilized. Medical status was assessed (family history of MFS, aortic root dilatation >40 mm, previous aortic surgery, aortic dissection, chronic pain, skeletal involvement, and scoliosis). Severe fatigue was experienced by 37% of the total MFS cohort (n = 155). MFS patients scored significantly higher on the CIS questionnaire, concerning severe fatigue, as compared with the general Dutch population (p < 0.0001). There were no differences in HADS anxiety or depression scores. In older MFS patients, with a more severe cardiovascular phenotype, chronic pain, and a higher unemployment rate, significantly more symptoms of depression were observed, when compared with the general population (p = 0.027) or compared with younger MFS patients (p = 0.026). Multivariate analysis, showed that anxiety was associated with chronic pain (p = 0.022) and symptoms of depression with unemployment (p = 0.024). MFS patients report significantly more severe fatigue as compared with the general population. Since the cause of fatigue is unclear, more research may be needed. Psychological intervention, for example, cognitive behavioral therapy, may contribute to a reduction in psychological symptoms.
Marfan syndrome (MFS) is an autosomal dominant genetic disorder characterized by aortic root dilation and dissection and an abnormal fibrillin-1 synthesis. In this observational study, we evaluated ...aortic stiffness in MFS and its association with ascending aorta diameters and fibrillin-1 genotype.
A total of 116 Marfan adult patients without history of cardiovascular surgery, and 144 age, sex, blood pressure and heart rate matched controls were enrolled. All patients underwent arterial stiffness evaluation through carotid-femoral pulse wave velocity (PWV) and central blood pressure waveform analysis (PulsePen tonometer). Fibrillin-1 mutations were classified based on the effect on the protein, into 'dominant negative' and 'haploinsufficient' mutations.
PWV and central pulse pressure were significantly higher in MFS patients than in controls respectively 7.31 (6.81-7.44) vs. 6.69 (6.52-6.86) m/s, P = 0.0008; 41.3 (39.1-43.5) vs. 34.0 (32.7-35.3) mmHg, P < 0.0001, with a higher age-related increase of PWV in MFS (β 0.062 vs. 0.036). Pressure amplification was significantly reduced in MFS 18.2 (15.9-20.5) vs. 33.4 (31.6-35.2)%, P < 0.0001. Central pressure profile was altered even in MFS patients without aortic dilatation. Multiple linear regression models showed that PWV independently predicted aortic diameters at the sinuses of Valsalva (ß = 0.243, P = 0.002) and at the sinotubular junction (ß = 0.186, P = 0.048). PWV was higher in 'dominant negative' than 'haploinsufficient' fibrillin-1 mutations 7.37 (7.04-7.70) vs. 6.60 (5.97-7.23) m/s, P = 0.035, although this difference was not significant after adjustment.
Aortic stiffness is increased in MFS, independently from fibrillin-1 genotype and is associated with diameters of ascending aorta. Alterations in central hemodynamics are present even when aortic diameter is within normal limits. Our findings suggest an accelerated arterial aging in MFS.
To delineate temporal and spatial dynamics of vascular smooth muscle cell (SMC) transcriptomic changes during aortic aneurysm development in Marfan syndrome (MFS). Approach and Results: We performed ...single-cell RNA sequencing to study aortic root/ascending aneurysm tissue from
(MFS) mice and healthy controls, identifying all aortic cell types. A distinct cluster of transcriptomically modulated SMCs (modSMCs) was identified in adult
mouse aortic aneurysm tissue only. Comparison with atherosclerotic aortic data (ApoE
mice) revealed similar patterns of SMC modulation but identified an MFS-specific gene signature, including plasminogen activator inhibitor-1 (
) and Kruppel-like factor 4 (
). We identified 481 differentially expressed genes between modSMC and SMC subsets; functional annotation highlighted extracellular matrix modulation, collagen synthesis, adhesion, and proliferation. Pseudotime trajectory analysis of
SMC/modSMC transcriptomes identified genes activated differentially throughout the course of phenotype modulation. While modSMCs were not present in young
mouse aortas despite small aortic aneurysm, multiple early modSMCs marker genes were enriched, suggesting activation of phenotype modulation. modSMCs were not found in nondilated adult
descending thoracic aortas. Single-cell RNA sequencing from human MFS aortic root aneurysm tissue confirmed analogous SMC modulation in clinical disease. Enhanced expression of TGF-β (transforming growth factor beta)-responsive genes correlated with SMC modulation in mouse and human data sets.
Dynamic SMC phenotype modulation promotes extracellular matrix substrate modulation and aortic aneurysm progression in MFS. We characterize the disease-specific signature of modSMCs and provide temporal, transcriptomic context to the current understanding of the role TGF-β plays in MFS aortopathy. Collectively, single-cell RNA sequencing implicates TGF-β signaling and
overexpression as potential upstream drivers of SMC modulation.
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