Aortopathy in Marfan syndrome: an update

Pathobiology of Aortic Aneurysms and Dissections: Synthesis of Recent Investigations and Evolving Insights

The pathobiology of aortic disease is linked to aortic region: atherosclerosis for abdominal aorta, primary medial degeneration or aortitis for ascending thoracic aorta, and all causes for descending thoracic aorta and thoracoabdominal lesions. The pathogenesis of aortic dissection involves damage of the outer media from impaired perfusion from dysfunctional vasa vasorum, formation of discrete foci of disrupted vascular smooth muscle cell-elastic fiber extension-contractile units, and imbalance of radial sheer stress across the aortic wall, thereby creating an intimal tear and linear dissection. Thoracic aortic aneurysms develop from the chronic progression of medial degeneration coupled with the weakening of the remodeled adventitia, allowing for aortic dilatation. Precipitating factors include hypertension and mutations of genes regulating the vascular smooth muscle cell-elastic fiber extension-contractile units. Criteria are presented for distinguishing genetic from acquired causes of thoracic aortic aneurysms and dissections, with important implications for therapeutic and surgical decisions in the care of these patients.

Aneurysm Associated with Vascular Wall Degeneration in Bearded Dragons (Pogona vitticeps)

This study describes the clinical, gross, and histologic findings in 17 cases of aneurysms in bearded dragons (Pogona vitticeps). The clinical presentation ranged from incidental to sudden and unexpected death. The affected vasculature was predominantly arterial; however, based on the topographical locations of the lesions, gross structure, and drainage, some veins were likely involved. Magnetic resonance imaging and computerized tomography scans of 1 animal showed a large aneurysm of the internal carotid artery extending from near its aortic origin into the caudal head. Aneurysms were organized in 5 groups based on their anatomical locations: cephalic, cranial coelom (for all near the heart), caudal coelom (for the mesenteric vessels and descending aorta), limbs, and tail. The cranial coelomic region was the most prevalent location. Gross findings were large hematomas or red serosanguineous fluid filling the adjacent area, as most of the aneurysms (94%) were ruptured at the time of the study. The main histological findings were degenerative changes of the vessel walls characterized by moderate to severe disruption of the collagen and elastic fibers of the tunica media and adventitia (100%), followed by thickening of the intima with thrombi formation (54%) and dissecting hematoma of the vessel wall (47%). Vasculitis (29%), mineralization (6%), and lipid deposits (6%) in the vessel wall were observed occasionally. Based on these findings, the vascular dilations and ruptures observed in bearded dragons likely are associated with weakness of the vessel walls caused by degenerative changes in the intimal and medial tunics.

miRNA Regulation of Cell Phenotype and Parietal Remodeling in Atherosclerotic and Non-Atherosclerotic Aortic Aneurysms: Differences and Similarities

Aortic aneurysms are a serious health concern as their rupture leads to high morbidity and mortality. Abdominal aortic aneurysms (AAAs) and thoracic aortic aneurysms (TAAs) exhibit differences and similarities in their pathophysiological and pathogenetic features. AAA is a multifactorial disease, mainly associated with atherosclerosis, characterized by a relevant inflammatory response and calcification. TAA is rarely associated with atherosclerosis and in some cases is associated with genetic mutations such as Marfan syndrome (MFS) and bicuspid aortic valve (BAV). MFS-related and non-genetic or sporadic TAA share aortic degeneration with endothelial-to-mesenchymal transition (End-Mt) and fibrosis, whereas in BAV TAA, aortic degeneration with calcification prevails. microRNA (miRNAs) contribute to the regulation of aneurysmatic aortic remodeling. miRNAs are a class of non-coding RNAs, which post-transcriptionally regulate gene expression. In this review, we report the involvement of deregulated miRNAs in the different aortic remodeling characterizing AAAs and TAAs. In AAA, miRNA deregulation appears to be involved in parietal inflammatory response, smooth muscle cell (SMC) apoptosis and aortic wall calcification. In sporadic and MFS-related TAA, miRNA deregulation promotes End-Mt, SMC myofibroblastic phenotypic switching and fibrosis with glycosaminoglycan accumulation. In BAV TAA, miRNA deregulation sustains aortic calcification. Those differences may support the development of more personalized therapeutic approaches.

Versican accumulation drives Nos2 induction and aortic disease in Marfan syndrome via Akt activation

Thoracic aortic aneurysm and dissection (TAAD) is a life-threatening condition associated with Marfan syndrome (MFS), a disease caused by fibrillin-1 gene mutations. While various conditions causing TAAD exhibit aortic accumulation of the proteoglycans versican (Vcan) and aggrecan (Acan), it is unclear whether these ECM proteins are involved in aortic disease. Here, we find that Vcan, but not Acan, accumulated in Fbn1C1041G/+ aortas, a mouse model of MFS. Vcan haploinsufficiency protected MFS mice against aortic dilation, and its silencing reverted aortic disease by reducing Nos2 protein expression. Our results suggest that Acan is not an essential contributor to MFS aortopathy. We further demonstrate that Vcan triggers Akt activation and that pharmacological Akt pathway inhibition rapidly regresses aortic dilation and Nos2 expression in MFS mice. Analysis of aortic tissue from MFS human patients revealed accumulation of VCAN and elevated pAKT-S473 staining. Together, these findings reveal that Vcan plays a causative role in MFS aortic disease in vivo by inducing Nos2 via Akt activation and identify Akt signaling pathway components as candidate therapeutic targets.

SPINT2 is involved in the proliferation, migration and phenotypic switching of aortic smooth muscle cells: Implications for the pathogenesis of thoracic aortic dissection

Thoracic aortic dissection (TAD) is a severe and extremely dangerous cardiovascular disease. Proliferation, migration and phenotypic switching of vascular smooth muscle cells (SMCs) are major pathogenetic mechanisms involved in the development of TAD. The present study was designed to investigate the expression and potential function of serine peptidase inhibitor Kunitz type 2 (SPINT2) in TAD. The gene expression profile data for ascending aorta from patients with TAD were downloaded from the GEO database with the accession number GSE52093. Bioinformatics analysis using GEO2R indicated that the differentially expressed SPINT2 was prominently decreased in TAD. The expression levels of SPINT2 mRNA and protein in aortic dissection specimens and normal aorta tissues were measured using reverse transcription-quantitative PCR and western blotting. SPINT2 expression was downregulated in clinical samples from aortic dissection specimens of patients with TAD compared with the corresponding expression noted in tissues derived from patients without TAD. In vitro, platelet-derived growth factor BB (PDGF-BB) was applied to induce the isolated primary mouse aortic SMC phenotypic modulation (a significant upregulation in the expression levels of synthetic markers), and the SMCs were infected with the adenoviral vector, Ad-SPINT2, to construct SPINT2-overexpressed cell lines. SMC viability was detected by an MTT assay and SMC proliferation was detected via the presence of Ki-67-positive cells (immunofluorescence staining). To explore the effects of SPINT2 on SMC migration, a wound healing assay was conducted. ELISA and western blotting assays were used to measure the content and expression levels of MMP-2 and MMP-9. The expression levels of vimentin, collagen I, α-SMA and SM22α were measured using western blotting. The PDGF-BB-induced proliferation and migration of SMCs were recovered by SPINT2 overexpression. The increase in the expression levels of SPINT2 reduced the expression levels of active matrix metalloproteinases (MMPs), MMP-2 and MMP-9. Overexpression of SPINT2 suppressed SMC switching from a contractile to a synthetic type, as evidenced by decreased vimentin and collagen I expression levels along with increased α-smooth muscle actin and smooth muscle protein 22-α expression levels. Furthermore, activation of ERK was inhibited in SPINT2-overexpressing SMCs. A specific ERK agonist, 12-O-tetradecanoylphorbol-13-acetate, reversed the SPINT2-mediated inhibition of SMC migration and the phenotypic switching. Collectively, the data indicated that SPINT2 was implicated in the proliferation, migration and phenotypic switching of aortic SMCs, suggesting that it may be involved in TAD progression.

miR-632 Induces DNAJB6 Inhibition Stimulating Endothelial-to-Mesenchymal Transition and Fibrosis in Marfan Syndrome Aortopathy

Marfan syndrome (MFS) is a connective tissue disorder caused by FBN1 gene mutations leading to TGF-β signaling hyperactivation, vascular wall weakness, and thoracic aortic aneurysms (TAAs). The pathogenetic mechanisms are not completely understood and patients undergo early vascular surgery to prevent TAA ruptures. We previously reported miR-632 upregulation in MFS TAA tissues compared with non-genetic TAA tissues. DNAJB6 is a gene target of miR-632 in cancer and plays a critical role in blocking epithelial-to-mesenchymal transition by inhibiting the Wnt/β catenin pathway. TGF-β signaling also activates Wnt/β catenin signaling and induces endothelial-to-mesenchymal transition (End-Mt) and fibrosis. We documented that miR-632 upregulation correlated with DNAJB6 expression in both the endothelium and the tunica media of MFS TAA (p < 0.01). Wnt/β catenin signaling, End-Mt, and fibrosis markers were also upregulated in MFS TAA tissues (p < 0.05, p < 0.01 and p < 0.001). Moreover, miR-632 overexpression inhibited DNAJB6, inducing Wnt/β catenin signaling, as well as End-Mt and fibrosis exacerbation (p < 0.05 and p < 0.01). TGF-β1 treatment also determined miR-632 upregulation (p < 0.01 and p < 0.001), with the consequent activation of the aforementioned processes. Our study provides new insights about the pathogenetic mechanisms in MFS aortopathy. Moreover, the high disease specificity of miR-632 and DNAJB6 suggests new potential prognostic factors and/or therapeutic targets in the progression of MFS aortopathy.

The prognostic marker elastin correlates with epithelial-mesenchymal transition and vimentin-positive fibroblasts in gastric cancer

Elastin (ELN) fibers are essential constituents of the tumor microenvironment of gastric cancer (GC). However, few studies have investigated the clinical prognostic significance of ELN in GC. We screened for molecular markers that were highly related to distant metastasis by transcriptome sequencing. The Cancer Genome Atlas (TCGA) and Harbin Medical University (HMU) validation cohorts were used to validate ELN expression and to explore molecular mechanisms. Immunohistochemistry for ELN, vimentin (VIM), and fibroblast activation protein, and elastic fiber-specific staining were used to evaluate the relationship between ELN and prognosis. R studio was used to construct a nomogram prognostic model. In this study, we found that ELN mRNA levels were significantly higher in cancer tissues and were associated with poor prognosis in TCGA and HMU patients. Gene set enrichment analysis showed that ELN was mainly enriched in the epithelial-mesenchymal transition (EMT) pathway. The mRNA expression of ELN was positively correlated with fibroblast molecular markers, especially VIM. For validation, we collected a tissue microarray containing 180 pairs of samples. We found that ELN was positively correlated with VIM expression in cancer tissue but not in paracancerous tissues by immunohistochemistry staining. Univariate and multivariate analyses showed that the expression of ELN and lymph node metastasis rate were independent predictors for overall survival. Moreover, a nomogram model was used to evaluate the risk of death by combining the expression of ELN and lymph node metastasis rate. ELN may play an important role in the progression of GC by regulating EMT and is a useful prognostic indicator in predicting the prognosis of GC.

Short-term rapamycin treatment increases life span and attenuates aortic aneurysm in a murine model of Marfan-Syndrome

BACKGROUND

Marfan syndrome (MFS) is a genetic disorder leading to medial aortic degeneration and life-limiting dissections. To date, there is no causal prevention or therapy. Rapamycin is a potent and selective inhibitor of the mechanistic target of rapamycin (mTOR) protein kinase, regulating cell growth and metabolism. The mgR/mgR mice represent an accepted MFS model for studying aortic pathologies to understand the underlying molecular pathomechanisms. This study investigated whether rapamycin inhibits the development of thoracic aortic aneurysms and dissections in mgR/mgR mice.

METHODS

Isolated primary aortic smooth muscle cells (mAoSMCs) from mgR/mgR mice were used for in vitro studies. Two mg kg/BW rapamycin was injected intraperitoneally daily for two weeks, beginning at 7-8 weeks of age. Mice were sacrificed 30 days post-treatment. Histopathological and immunofluorescence analyses were performed using adequate tissue specimens and techniques. Animal survival was evaluated accompanied by periodic echocardiographic examinations of the aorta.

RESULTS

The protein level of the phosphorylated ribosomal protein S6 (p-RPS6), a downstream target of mTOR, was significantly increased in the aortic tissue of mgR/mgR mice. In mAoSMCs isolated from these animals, expression of mTOR, p-RPS6, tumour necrosis factor α, matrix metalloproteinase-2 and -9 was significantly suppressed by rapamycin, demonstrating its anti-inflammatory capacity. Short-term rapamycin treatment of Marfan mice was associated with delayed aneurysm formation, medial aortic elastolysis and improved survival.

CONCLUSIONS

Short-term rapamycin-mediated mTOR inhibition significantly reduces aortic aneurysm formation and thus increases survival in mgR/mgR mice. Our results may offer the first causal treatment option to prevent aortic complications in MFS patients.

Early and midterm results of frozen elephant trunk operation with Evita open stent-graft in patients with Marfan syndrome: results of a multicentre study

BACKGROUND

Endovascular treatment of patients with Marfan syndrome (MFS) is not recommended. Hybrid procedures such as frozen elephant trunk (FET), which combines stent-graft deployment with an integrated non-stented fabric graft for proximal grafting and suturing, have not been previously evaluated. The aim of this study was to assess the safety and feasibility of FET operation in patients with MFS.

METHODS

Patients enrolled in the International E-vita Open Registry (IEOR) who underwent FET procedure between January 2001 and February 2020 meeting Ghent criteria for MFS were included in the study. Early and midterm results were retrospectively analyzed. Preoperative, postoperative and follow-up computed tomography angiography scans were analysed.

RESULTS

We analyzed 37 patients [mean age 38 ± 11 years, 65% men]. Acute or chronic aortic dissection was present in 35 (95%) patients (14 and 21 patients respectively). Two (5%) patients had an aneurysm without dissection. Malperfusion syndrome was present in 4 patients. Twenty-nine (78%) patients had history of aortic surgical interventions. The 30-day and in-hospital mortality amounted to 8 and 14% respectively. False lumen exclusion was present in 73% in stented segment in last postoperative CT. The overall 5-year survival was 71% and freedom from reintervention downstream was 58% at 5 years. Of the nine patients who required reintervention for distal aortic disease, one patient died.

CONCLUSIONS

FET operation for patients with MFS can be performed with acceptable mortality and morbidity. In long-term follow-up no reinterventions on the aortic arch were required. FET allows for easier second stage operations providing platform for surgical and endovascular reinterventions.

The Predictive Role of Plasma Biomarkers in the Evolution of Aortopathies Associated with Congenital Heart Malformations

Dilatation of the aorta is a constantly evolving condition that can lead to the ultimate life-threatening event, acute aortic dissection. Recent research has tried to identify quantifiable biomarkers, with both diagnostic and prognostic roles in different aortopathies. Most studies have focused on the bicuspid aortic valve, the most frequent congenital heart disease (CHD), and majorly evolved around matrix metalloproteinases (MMPs). Other candidate biomarkers, such as asymmetric dimethylarginine, soluble receptor for advanced glycation end-products or transforming growth factor beta have also gained a lot of attention recently. Most of the aortic anomalies and dilatation-related studies have reported expression variation of tissular biomarkers. The ultimate goal remains, though, the identification of biomarkers among the serum plasma, with the upregulation of circulating MMP-1, MMP-2, MMP-9, tissue inhibitor of metalloproteinase-1 (TIMP-1), asymmetric dimethylarginine (ADMA), soluble receptor for advanced glycation end-products (sRAGE) and transforming growth factor beta (TGF-β) being reported in association to several aortopathies and related complications in recent research. These molecules are apparently quantifiable from the early ages and have been linked to several CHDs and hereditary aortopathies. Pediatric data on the matter is still limited, and further studies are warranted to elucidate the role of plasmatic biomarkers in the long term follow-up of potentially evolving congenital aortopathies.

The NO signalling pathway in aortic aneurysm and dissection

Recent studies have shown that NO is a central mediator in diseases associated with thoracic aortic aneurysm, such as Marfan syndrome. The progressive dilation of the aorta in thoracic aortic aneurysm ultimately leads to aortic dissection. Unfortunately, current medical treatments have neither halt aortic enlargement nor prevented rupture, leaving surgical repair as the only effective treatment. There is therefore a pressing need for effective therapies to delay or even avoid the need for surgical repair in thoracic aortic aneurysm patients. Here, we summarize the mechanisms through which NO signalling dysregulation causes thoracic aortic aneurysm, particularly in Marfan syndrome. We discuss recent advances based on the identification of new Marfan syndrome mediators related to pathway overactivation that represent potential disease biomarkers. Likewise, we propose iNOS, sGC and PRKG1, whose pharmacological inhibition reverses aortopathy in Marfan syndrome mice, as targets for therapeutic intervention in thoracic aortic aneurysm and are candidates for clinical trials.

Elastic tissue disruption is a major pathogenic factor to human vascular disease

Elastic fibers are essential components of the arterial extracellular matrix. They consist of the protein elastin and an array of microfibrils that support the protein and connect it to the surrounding matrix. The elastin gene encodes tropoelastin, a protein that requires extensive cross-linking to become elastin. Tropoelastin is expressed throughout human life, but its expression levels decrease with age, suggesting that the potential to synthesize elastin persists during lifetime although declines with aging. The initial abnormality documented in human atherosclerosis is fragmentation and loss of the elastic network in the medial layer of the arterial wall, suggesting an imbalance between elastic fiber injury and restoration. Damaged elastic structures are not adequately repaired by synthesis of new elastic elements. Progressive collagen accumulation follows medial elastic fiber disruption and fibrous plaques are formed, but advanced atherosclerosis lesions do not develop in the absence of prior elastic injury. Aging is associated with arterial extracellular matrix anomalies that evoke those present in early atherosclerosis. The reduction of elastic fibers with subsequent collagen accumulation leads to arterial stiffening and intima-media thickening, which are independent predictors of incident hypertension in prospective community-based studies. Arterial stiffening precedes the development of hypertension. The fundamental role of the vascular elastic network to arterial structure and function is emphasized by congenital disorders caused by mutations that disrupt normal elastic fiber production. Molecular changes in the genes coding tropoelastin, lysyl oxidase (tropoelastin cross-linking), and elastin-associated microfibrils, including fibrillin-1, fibulin-4, and fibulin-5 produce severe vascular injury due to absence of functional elastin.

Elastic fibers: formation, function, and fate during aging and disease

Elastic fibers are extracellular components of higher vertebrates and confer elasticity and resilience to numerous tissues and organs such as large blood vessels, lungs, and skin. Their formation and maturation take place in a complex multistage process called elastogenesis. It requires interactions between very different proteins but also other molecules and leads to the deposition and crosslinking of elastin's precursor on a scaffold of fibrillin-rich microfibrils. Mature fibers are exceptionally resistant to most influences and, under healthy conditions, retain their biomechanical function over the life of the organism. However, due to their longevity, they accumulate damages during aging. These are caused by proteolytic degradation, formation of advanced glycation end products, calcification, oxidative damage, aspartic acid racemization, lipid accumulation, carbamylation, and mechanical fatigue. The resulting changes can lead to diminution or complete loss of elastic fiber function and ultimately affect morbidity and mortality. Particularly, the production of elastokines has been clearly shown to influence several life-threatening diseases. Moreover, the structure, distribution, and abundance of elastic fibers are directly or indirectly influenced by a variety of inherited pathological conditions, which mainly affect organs and tissues such as skin, lungs, or the cardiovascular system. A distinction can be made between microfibril-related inherited diseases that are the result of mutations in diverse microfibril genes and indirectly affect elastogenesis, and elastinopathies that are linked to changes in the elastin gene. This review gives an overview on the formation, structure, and function of elastic fibers and their fate over the human lifespan in health and disease.

AAV-mediated AP-1 decoy oligonucleotide expression inhibits aortic elastolysis in a mouse model of marfan syndrome

AIMS

Marfan syndrome is one of the most common inherited disorders of connective tissue caused by fibrillin-1 mutations, characterized by enhanced transcription factor AP-1 DNA binding activity and subsequently abnormally increased expression and activity of matrix-metalloproteinases (MMPs). We aimed to establish a novel adeno-associated virus (AAV)-based strategy for long-term expression of an AP-1 neutralising RNA hairpin (hp) decoy oligonucleotide (dON) in the aorta to prevent aortic elastolysis in a murine model of Marfan syndrome.

METHODS AND RESULTS

Using fibrillin-1 hypomorphic mice (mgR/mgR), aortic grafts from young (9 weeks old) donor mgR/mgR mice were transduced ex vivo with AAV vectors and implanted as infrarenal aortic interposition grafts in mgR/mgR mice. Grafts were explanted after 30 days. For in vitro studies isolated primary aortic smooth muscle cells from mgR/mgR mice were used. Elastica-van-Giesson staining visualized elastolysis, ROS production was assessed using DHE staining. RNA F.I.S.H. verified AP-1 hp dON generation in the ex vivo transduced aortic tissue. MMP expression and activity were assessed by western blotting and immunoprecipitation combined with zymography.Transduction resulted in stable therapeutic dON expression in endothelial and smooth muscle cells. MMP expression and activity, ROS formation as well as expression of monocyte chemoattractant protein-1 were significantly reduced. Monocyte graft infiltration declined and the integrity of the elastin architecture was maintained. RNAseq analyzis confirmed the beneficial effect of AP-1 neutralisation on the pro-inflammatory environment in smooth muscle cells.

CONCLUSIONS

This novel approach protects from deterioration of aortic stability by sustained delivery of nucleic acids-based therapeutics and further elucidated how to interfere with the mechanism of elastolysis.

TRANSLATIONAL PERSPECTIVE

This study provides a novel single treatment option to achieve long-term expression of a transcription factor AP-1 neutralising decoy oligonucleotide in the aorta of mgR/mgR mice with the potential to prevent life-threatening elastolysis and aortic complications.

Surgical Outcome and Histological Differences between Individuals with TGFBR1 and TGFBR2 Mutations in Loeys-Dietz Syndrome

PURPOSE

To identify differences in surgical outcomes between patients with transforming growth factor-beta receptor (TGFBR) 1 and TGFBR2 mutations in Loeys-Dietz syndrome (LDS).

METHODS

In all, 22 LDS patients between 1998 and 2015 were divided into the two groups: TGFBR1 (n = 11) and TGFBR2 mutation (n = 11).

RESULTS

The freedom from aortic reoperation was similar between the two groups (p = 0.19, log-rank). In the subanalysis, the freedom from aortic reoperation was lower in female patients with TGFBR2 mutations (n = 6) than in other patients (p = 0.08). The freedom from aortic dissection (AD) after the initial surgery was also lower in female patients with TGFBR2 mutation than in other patients (p = 0.025). All patients with TGFBR2 mutations revealed grade III cystic medial necrosis (CMN), whereas 67% of patients with TGFBR1 mutations showed CMN (p = 0.033) and only one patient had grade III (p <0.001).

CONCLUSION

LDS patients with TGFBR2 mutations had higher grade of CMN than those of TGFBR1 mutations. In particular, in female patients with TGFBR2 mutations, AD after the initial surgery and reoperation were more frequent than those of other LDS patients.

Ulnar Artery Aneurysm as a Late Sequela of Marfan Syndrome

Marfan syndrome (MFS) is a connective tissue disorder caused by mutations of the FBN1 gene encoding fibrillin-1, which leads to overexpression of transforming growth factor-β, increased hyaluronan deposition, and matrix metalloproteinase activity in the media of the aorta and other muscular arteries. Marfan syndrome patients present with connective tissue laxity and aneurysmal changes to muscular arteries. Successful medical and surgical intervention has prolonged the life expectancy of MFS patients, which can allow atypical presentations of the syndrome to manifest. We present a case of a 49-year-old man with MFS who developed an ulnar artery aneurysm that was treated by excision and vein grafting.

Specific miRNA and Gene Deregulation Characterize the Increased Angiogenic Remodeling of Thoracic Aneurysmatic Aortopathy in Marfan Syndrome

Marfan syndrome (MFS) is a connective tissue disease caused by mutations in the FBN1 gene, leading to alterations in the extracellular matrix microfibril assembly and the early formation of thoracic aorta aneurysms (TAAs). Non-genetic TAAs share many clinico-pathological aspects with MFS and deregulation of some microRNAs (miRNAs) has been demonstrated to be involved in the progression of TAA. In this study, 40 patients undergoing elective ascending aorta surgery were enrolled to compare TAA histomorphological features, miRNA profile and related target genes in order to find specific alterations that may explain the earlier and more severe clinical outcomes in MFS patients. Histomorphological, ultrastructural and in vitro studies were performed in order to compare aortic wall features of MFS and non-MFS TAA. MFS displayed greater glycosaminoglycan accumulation and loss/fragmentation of elastic fibers compared to non-MFS TAA. Immunohistochemistry revealed increased CD133⁺ angiogenic remodeling, greater MMP-2 expression, inflammation and smooth muscle cell (SMC) turnover in MFS TAA. Cultured SMCs from MFS confirmed higher turnover and α-smooth muscle actin expression compared with non-MFS TAA. Moreover, twenty-five miRNAs, including miR-26a, miR-29, miR-143 and miR-145, were found to be downregulated and only miR-632 was upregulated in MFS TAA in vivo. Bioinformatics analysis revealed that some deregulated miRNAs in MFS TAA are implicated in cell proliferation, extracellular matrix structure/function and TGFβ signaling. Finally, gene analysis showed 28 upregulated and seven downregulated genes in MFS TAA, some of them belonging to the CDH1/APC and CCNA2/TP53 signaling pathways. Specific miRNA and gene deregulation characterized the aortopathy of MFS and this was associated with increased angiogenic remodeling, likely favoring the early and more severe clinical outcomes, compared to non-MFS TAA. Our findings provide new insights concerning the pathogenetic mechanisms of MFS TAA; further investigation is needed to confirm if these newly identified specific deregulated miRNAs may represent potential therapeutic targets to counteract the rapid progression of MFS aortopathy.

Microarray analysis of long non-coding RNA expression profiles in Marfan syndrome

Long non-coding RNAs (lncRNAs) serve a crucial role in every aspect of cell biological functions as well as in a variety of diseases, including cardiovascular disease, cancer and nervous system disease. However, the differential expression profiles of lncRNAs in Marfan syndrome (MFS) have not been reported. The aim of the present study was to identify potential target genes behind the pathogenesis of MFS by analyzing microarray profiles of lncRNA in aortic tissues from individuals with MFS and normal aortas (NA). The differentially expressed lncRNA profiles between MFS (n=3) and NA (n=4) tissues were analyzed using microarrays. Bioinformatics analyses were used to further investigate the candidate lncRNAs. Reverse transcription-quantitative (RT-qPCR) was applied to validate the results. In total, the present study identified 294 lncRNAs (245 upregulated and 49 downregulated) and 644 mRNAs (455 upregulated and 189 downregulated) which were differential expressed between MFS and NA tissues (fold change ≥1.5; P<0.05). Gene Ontology enrichment analysis indicated that the differentially expressed mRNAs were involved in cell adhesion, elastic fiber assembly, extracellular matrix (ECM) organization, the response to virus and the inflammatory response. Kyoto Encyclopedia of Gene and Genomes pathway analysis indicated that the differentially expressed mRNAs were mainly associated with focal adhesion, the ECM-receptor interaction, the mitogen-activated protein kinase signaling pathway and the tumor necrosis factor signaling pathway. The lncRNA-mRNA coexpression network analysis further elucidated the interaction between the lncRNAs and mRNAs. A total of five lncRNAs (uc003jka.1, uc003jox.1, X-inactive specific transcript, linc-lysophosphatidic acid receptor 1 and linc-peptidylprolyl isomerase domain and WD repeat containing 1) with the highest degree of coexpression were selected and confirmed using RT-qPCR. In the present study, expression profiles of lncRNA and mRNA in MFS were revealed using microarray analysis. These results provided novel candidates for further investigation of the molecular mechanisms and effective targeted therapies for MFS.

The RNA-binding fragile-X mental retardation protein and its role beyond the brain

It is well-established that variations of a CGG repeat expansion in the gene FMR1, which encodes the fragile-X mental retardation protein (FMRP), cause the neurocognitive disorder, fragile-X syndrome (FXS). However, multiple observations suggest a general and complex regulatory role of FMRP in processes outside the brain: (1) FMRP is ubiquitously expressed in the body, suggesting it functions in multiple organ systems; (2) patients with FXS can exhibit a physical phenotype that is consistent with an underlying abnormality in connective tissue; (3) different CGG repeat expansion lengths in FMR1 result in different clinical outcomes due to different pathogenic mechanisms; (4) the function of FMRP as an RNA-binding protein suggests it has a general regulatory role. This review details the complex nature of FMRP and the different CGG repeat expansion lengths and the evidence supporting the essential role of the protein in a variety of biological and pathological processes.

Biomechanical properties and histomorphometric features of aortic tissue in patients with or without bicuspid aortic valve

Background

We sought to investigate and compare biomechanical properties and histomorphometric findings of thoracic ascending aorta aneurysm (TAA) tissue from patients with bicuspid aortic valve (BAV) and tricuspid aortic valve (TAV) in order to clarify mechanisms underlying differences in the clinical course.

Methods

Circumferential sections of TAA tissue in patients with BAV (BAV-TAA) and TAV (TAV-TAA) were obtained during surgery and used for biomechanical tests and histomorphometrical analysis.

Results

In BAV-TAA, we observed biomechanical higher peak stress and lower Young modulus values compared with TAV-TAA wall. The right lateral longitudinal region seemed to be the most fragile zone of the TAA wall. Mechanical stress-induced rupture of BAV-TAA tissue was sudden and uniform in all aortic wall layers, whereas a gradual and progressive aortic wall breakage was described in TAV-TAA. Histomorphometric analysis revealed higher amount of collagen but not elastin in BAV-TAA tunica media.

Conclusions

The higher deformability of BAV-TAA tissue supports the hypothesis that increased wall shear stress doesn’t explain the increased risk of sudden onset of rupture and dissection; other mechanisms, likely related to alteration of specific genetic pathways and epigenetic signals, could be investigated to explain differences in aortic dissection and rupture in BAV patients.

Beyond plaque: A pictorial review of non-atherosclerotic abnormalities of extracranial carotid arteries

The common carotid artery (CCA) and extracranial internal carotid artery are subject to a wide variety of non-atheromatous pathologies. These entities are often overshadowed in both research and clinical realms by atherosclerotic disease. Nevertheless, non-atherosclerotic disease of the carotid arteries may have profound, even devastating, neurologic consequences. Hence, this review will cover both common and uncommon forms of extracranial carotid artery pathologies in a pictorial format, in order to aid the diagnostician in identifying and differentiating such pathologies.

Genetic and epigenetic regulation of abdominal aortic aneurysms

Abdominal aortic aneurysms (AAAs) are focal dilations of the aorta that develop from degenerative changes in the media and adventitia of the vessel. Ruptured AAAs have a mortality of up to 85%, thus it is important to identify patients with AAA at increased risk for rupture who would benefit from increased surveillance and/or surgical repair. Although the exact genetic and epigenetic mechanisms regulating AAA formation are not completely understood, Mendelian cases of AAA, which result from pathologic variants in a single gene, have helped provide a basic understanding of AAA pathophysiology. More recently, genome wide associated studies (GWAS) have identified additional variants, termed single nucleotide polymorphisms, in humans that may be associated with AAAs. While some variants may be associated with AAAs and play causal roles in aneurysm pathogenesis, it should be emphasized that the majority of SNPs do not actually cause disease. In addition to GWAS, other studies have uncovered epigenetic causes of disease that regulate expression of genes known to be important in AAA pathogenesis. This review describes many of these genetic and epigenetic contributors of AAAs, which altogether provide a deeper insight into AAA pathogenesis.

Severe aortic root dilatation in infantile Marfan syndrome

Cardiovascular manifestations of Marfan syndrome are associated with increased mortality, especially in the pediatric population. Early recognition is critical to long-term management. We present two cases of genetically defined "classical" Marfan syndrome presenting with severe infantile aortic root dilatation among siblings and discuss options for therapy.

Marfan syndrome: A therapeutic challenge for long-term care

Marfan syndrome (MFS) is an autosomal dominant genetic disorder caused by mutations in the fibrillin-1 gene. Acute aortic dissection is the leading cause of death in patients suffering from MFS and consequence of medial degeneration and aneurysm formation. In addition to its structural function in the formation of elastic fibers, fibrillin has a major role in keeping maintaining transforming growth factor β (TGF-β) in an inactive form. Dysfunctional fibrillin increases TGF-β bioavailability and concentration in the extracellular matrix, leading to activation of proinflammatory transcription factors. In turn, these events cause increased expression of matrix metalloproteinases and cytokines that control the migration and infiltration of inflammatory cells into the aorta. Moreover, TGF-β causes accumulation of reactive oxygen species leading to further degradation of elastin fibers. All these processes result in medial elastolysis, which increases the risk of vascular complications. Although MFS is a hereditary disease, symptoms and traits are usually not noticeable at birth. During childhood or adolescence affected individuals present with severe tissue weaknesses, especially in the aorta, heart, eyes, and skeleton. Considering this, even young patients should avoid activities that exert additional stress and pressure on the aorta and the cardiovascular system. Thus, if the diagnosis is made and prophylactic treatment is initiated in a timely fashion, MFS and its preliminary pathophysiologic vascular remodeling can be successfully ameliorated reducing the risk of life-threatening complications. This commentary focuses on new research opportunities and molecular findings on MFS, discusses future challenges and possible long-term therapies.

The Potential Beneficial Effects of Resveratrol on Cardiovascular Complications in Marfan Syndrome Patients⁻Insights from Rodent-Based Animal Studies

Marfan syndrome (MFS) patients are at risk for cardiovascular disease. In particular, for aortic aneurysm formation, which ultimately can result in a life-threatening aortic dissection or rupture. Over the years, research into a sufficient pharmacological treatment option against aortopathy has expanded, mostly due to the development of rodent disease models for aneurysm formation and dissections. Unfortunately, no optimal treatment strategy has yet been identified for MFS. The biologically-potent polyphenol resveratrol (RES), that occurs in nuts, plants, and the skin of grapes, was shown to have a positive effect on aortic repair in various rodent aneurysm models. RES demonstrated to affect aortic integrity and aortic dilatation. The beneficial processes relevant for MFS included the improvement of endothelial dysfunction, extracellular matrix degradation, and smooth muscle cell death. For the wide range of beneficial effects on these mechanisms, evidence was found for the following involved pathways; alleviating oxidative stress (change in eNOS/iNOS balance and decrease in NOX4), reducing protease activity to preserve the extracellular matrix (decrease in MMP2), and improving smooth muscle cell survival affecting aortic aging (changing the miR21/miR29 balance). Besides aortic features, MFS patients may also suffer from manifestations concerning the heart, such as mitral valve prolapse and left ventricular impairment, where evidence from rodent models shows that RES may aid in promoting cardiomyocyte survival directly (SIRT1 activation) or by reducing oxidative stress (increasing superoxide dismutase) and increasing autophagy (AMPK activation). This overview discusses recent RES studies in animal models of aortic aneurysm formation and heart failure, where different advantageous effects have been reported that may collectively improve the aortic and cardiac pathology in patients with MFS. Therefore, a clinical study with RES in MFS patients seems justified, to validate RES effectiveness, and to judge its suitability as potential new treatment strategy.

Histologic differences between the ascending and descending aortas in young adults with fibrillin-1 mutations

OBJECTIVES

This study aimed to review the clinical results of young adult patients with aortic disease associated with mutations in the fibrillin-1 gene (FBN1) and disclose the histologic differences between the ascending and descending aortas.

METHODS

Between 2012 and 2015, 94 patients aged less than 50 years underwent surgery for thoracic aortic diseases. Forty-two patients (44.7%) had FBN-1 mutations. Of these, 40 patients (42.5%) with surgical specimens for histologic evaluation were included in the study. With the histologic results including the specimen sampled at their previous operations, cystic medial necrosis was classified into 3 grades according to the degree of the cystic area.

RESULTS

Thirty-nine patients (97.5%) had aortic root dilatation (Z ≥2), and 13 patients (32.5%) had ectopia lentis. Thirty-nine patients (97.5%) fulfilled the diagnostic criteria for Marfan syndrome. There were no in-hospital deaths. The majority (27/29: 93.1%) of the specimens of the ascending aorta revealed cystic medial necrosis pattern. With grade III being the most severe condition, these cases were classified into grade I (n = 2), grade II (n = 5), and grade III (n = 20). In contrast, only 6 specimens (6/17: 35.3%) of the descending aorta showed a cystic medial necrosis pattern that was classified into grade I (n = 2) and grade III (n = 4), (P < .00001).

CONCLUSIONS

Fewer specimens of the descending aorta revealed cystic medial necrosis compared with those of the ascending aorta. This difference might influence the characteristic aortic disease in Marfan syndrome associated with FBN-1 mutations.

Large-Scale Analysis of Redox-Sensitive Conditionally Disordered Protein Regions Reveals Their Widespread Nature and Key Roles in High-Level Eukaryotic Processes

Recently developed quantitative redox proteomic studies enable the direct identification of redox-sensing cysteine residues that regulate the functional behavior of target proteins in response to changing levels of reactive oxygen species. At the molecular level, redox regulation can directly modify the active sites of enzymes, although a growing number of examples indicate the importance of an additional underlying mechanism that involves conditionally disordered proteins. These proteins alter their functional behavior by undergoing a disorder-to-order transition in response to changing redox conditions. However, the extent to which this mechanism is used in various proteomes is currently unknown. Here, a recently developed sequence-based prediction tool incorporated into the IUPred2A web server is used to estimate redox-sensitive conditionally disordered regions at a large scale. It is shown that redox-sensitive conditional disorder is fairly widespread in various proteomes and that its presence strongly correlates with the expansion of specific domains in multicellular organisms that largely rely on extra stability provided by disulfide bonds or zinc ion binding. The analyses of yeast redox proteomes and human disease data further underlie the significance of this phenomenon in the regulation of a wide range of biological processes, as well as its biomedical importance.

MicroCT imaging reveals differential 3D micro-scale remodelling of the murine aorta in ageing and Marfan syndrome

Aortic wall remodelling is a key feature of both ageing and genetic connective tissue diseases, which are associated with vasculopathies such as Marfan syndrome (MFS). Although the aorta is a 3D structure, little attention has been paid to volumetric assessment, primarily due to the limitations of conventional imaging techniques. Phase-contrast microCT is an emerging imaging technique, which is able to resolve the 3D micro-scale structure of large samples without the need for staining or sectioning.

Methods: Here, we have used synchrotron-based phase-contrast microCT to image aortae of wild type (WT) and MFS Fbn1^C1039G/+ mice aged 3, 6 and 9 months old (n=5). We have also developed a new computational approach to automatically measure key histological parameters.

Results: This analysis revealed that WT mice undergo age-dependent aortic remodelling characterised by increases in ascending aorta diameter, tunica media thickness and cross-sectional area. The MFS aortic wall was subject to comparable remodelling, but the magnitudes of the changes were significantly exacerbated, particularly in 9 month-old MFS mice with ascending aorta wall dilations. Moreover, this morphological remodelling in MFS aorta included internal elastic lamina surface breaks that extended throughout the MFS ascending aorta and were already evident in animals who had not yet developed aneurysms.

Conclusions: Our 3D microCT study of the sub-micron wall structure of whole, intact aorta reveals that histological remodelling of the tunica media in MFS could be viewed as an accelerated ageing process, and that phase-contrast microCT combined with computational image analysis allows the visualisation and quantification of 3D morphological remodelling in large volumes of unstained vascular tissues.

Non-coding RNAs in aneurysmal aortopathy

Aortic aneurysms represent a major public health burden, and currently have no medical treatment options. The pathophysiology behind these aneurysms is complex and variable, depending on location and underlying cause, and generally involves progressive dysfunction of all elements of the aortic wall. Changes in smooth muscle behavior, endothelial signaling, extracellular matrix remodeling, and to a variable extent inflammatory signaling and cells, all contribute to the dilation of the aorta, ultimately resulting in high mortality and morbidity events including dissection and rupture. A large number of researchers have identified non-coding RNAs as crucial regulators of aortic aneurysm development, both in humans and in animal models. While most work to-date has focused on microRNAs, intriguing information has also begun to emerge regarding the role of long-non-coding RNAs. This review summarizes the currently available data regarding the involvement of non-coding RNAs in aneurysmal aortopathies. Going forward, these represent key potential therapeutic targets that might be leveraged in the future to slow or prevent aortic aneurysm formation, progression and rupture.

A mutation update on the LDS-associated genes TGFB2/3 and SMAD2/3

The Loeys–Dietz syndrome (LDS) is a connective tissue disorder affecting the cardiovascular, skeletal, and ocular system. Most typically, LDS patients present with aortic aneurysms and arterial tortuosity, hypertelorism, and bifid/broad uvula or cleft palate. Initially, mutations in transforming growth factor‐β (TGF‐β) receptors (TGFBR1 and TGFBR2) were described to cause LDS, hereby leading to impaired TGF‐β signaling. More recently, TGF‐β ligands, TGFB2 and TGFB3, as well as intracellular downstream effectors of the TGF‐β pathway, SMAD2 and SMAD3, were shown to be involved in LDS. This emphasizes the role of disturbed TGF‐β signaling in LDS pathogenesis. Since most literature so far has focused on TGFBR1/2, we provide a comprehensive review on the known and some novel TGFB2/3 and SMAD2/3 mutations. For TGFB2 and SMAD3, the clinical manifestations, both of the patients previously described in the literature and our newly reported patients, are summarized in detail. This clearly indicates that LDS concerns a disorder with a broad phenotypical spectrum that is still emerging as more patients will be identified. All mutations described here are present in the corresponding Leiden Open Variant Database.

Characterization of a new decellularized bovine pericardial biological mesh: Structural and mechanical properties

Implants made from naturally-derived biomaterials, also called biological meshes or biomeshes, typically derive from decellularized extracellular matrix of either animal or human tissue. Biomeshes have many biomedical applications such as ligament repair, bone and cartilage regeneration and soft tissue replacement. Bovine collagen is one of the most widely used and abundantly available xenogenic materials. In particular, bovine pericardium is widely used as extracellular matrix bioprosthetic tissue. The efficiency of a pericardial mesh to function as scaffold depends on the quality of the decellularization protocol used. Moreover, the biomesh mechanical features are critical for a successful surgical repair process, as they must reproduce the biological properties of the autologous tissue. Different methods of physical, chemical, or enzymatic decellularization exist, but no one has proved to be ideal. Therefore, in the present study, we developed a novel decellularization protocol for a bovine pericardium-derived biomesh. We characterized the biomesh obtained by comparing some ultrastructural, physical and mechanical features to a reference commercial biomesh. Quantification revealed that our novel decellularization process removed about 90% of the native pericardial DNA. Microscopic and ultrastructural analysis documented the maintenance of the physiological structure of the pericardial collagen. Moreover, mechanical tests showed that both the extension and resilience of the new biomesh were statistically higher than the commercial control ones. The results presented in this study demonstrate that our protocol is promising in preparing high quality bovine pericardial biomeshes, encouraging further studies to validate its use in tissue engineering and regenerative medicine protocols.

High-Resolution Morphological Approach to Analyse Elastic Laminae Injuries of the Ascending Aorta in a Murine Model of Marfan Syndrome

In Marfan syndrome, the tunica media is disrupted, which leads to the formation of ascending aortic aneurysms. Marfan aortic samples are histologically characterized by the fragmentation of elastic laminae. However, conventional histological techniques using transverse sections provide limited information about the precise location, progression and 3D extension of the microstructural changes that occur in each lamina. We implemented a method using multiphoton excitation fluorescence microscopy and computational image processing, which provides high-resolution en-face images of segmented individual laminae from unstained whole aortic samples. We showed that internal elastic laminae and successive 2^nd laminae are injured to a different extent in murine Marfan aortae; in particular, the density and size of fenestrae changed. Moreover, microstructural injuries were concentrated in the aortic proximal and convex anatomical regions. Other parameters such as the waviness and thickness of each lamina remained unaltered. In conclusion, the method reported here is a useful, unique tool for en-face laminae microstructure assessment that can obtain quantitative three-dimensional information about vascular tissue. The application of this method to murine Marfan aortae clearly shows that the microstructural damage in elastic laminae is not equal throughout the thickness of the tunica media and in the different anatomical regions of the ascending aorta.

Vascular diseases: aortitis, aortic aneurysms, and vascular calcification

Inflammatory diseases of the aorta broadly include noninfectious and infectious aortitis, periaortitis, atherosclerosis, and inflammatory atherosclerotic aneurysms. Aortitis is uncommon but is increasingly recognized as an important cause of aortic aneurysms and dissections. Abdominal (AAA) and thoracic aortic aneurysms (TAA) have different pathologies and etiologies. AAAs are the most common type of aortic aneurysm, and the vast majority of these are atherosclerotic. The causes of TAA vary depending on the site of involvement, but medial degeneration is a common pathologic substrate, regardless of etiology, and genetic influences play a prominent role in TAA expression. Standardized classification schemes for inflammatory and degenerative diseases of the aorta have only recently been added to the pathology literature. A brief overview of the new histopathologic classifications for aortic inflammatory and degenerative diseases has recently been published by the Society for Cardiovascular Pathology and the Association for European Cardiovascular Pathology as a consensus document on the surgical pathology of the aorta. Vascular calcification is a highly regulated biologic process, and the mechanisms leading to vascular calcification are under investigation. Calcification may occur in the intima (atherosclerotic) or in the media secondary to metabolic disease. Rarely, vascular calcification may be associated with genetic disorders.

Analysis of TGFBR1*6A variant in individuals evaluated for Marfan syndrome

Marfan syndrome (MFS) and Loeys-Dietz syndrome (LDS) are genetic disorders that affect connective tissue as a result of dysregulated TGF-β signaling. MFS is most frequently caused by mutations in FBN1 whereas Loeys-Dietz syndrome results from mutations in TGFBR1 or TGFBR2. There is substantial inter- and intra-familial phenotypic variability among these disorders, suggesting the presence of genetic modifiers. Previously, a polymorphism in the TGFβR1 protein termed the TFGBR1*6A allele was found to be overrepresented in patients with MFS and was identified as a low penetrance allele with suggestion as a possible modifier. To further investigate the importance of this variant, a retrospective review of genetic and phenotypic findings was conducted for 335 patients evaluated for suspicion of MFS or related disorders. In patients with a diagnosis of MFS, the presence of the TFGBR1*6A allele was not associated with phenotypic differences. Similarly, careful phenotyping of patients who carried the TFGBR1*6A allele but did not have MFS did not identify an altered frequency of specific connective tissue features. In this small cohort, the results did not reach significance to identify the TFGBR1*6A allele as a major modifier for aortic dilation, ectopia lentis, or systemic features associated with MFS or other connective tissue disorders. © 2016 Wiley Periodicals, Inc.

A Decade of Discovery in the Genetic Understanding of Thoracic Aortic Disease

Aortic aneurysms are responsible for a significant number of all deaths in Western countries. In this review we provide a perspective on the important progress made over the past decade in the understanding of the genetics of this condition, with an emphasis on the more frequent forms of vascular smooth muscle and transforming growth factor β (TGF-β) signalling alterations. For several nonsyndromic and syndromic forms of thoracic aortic disease, a genetic basis has now been identified, with 3 main pathomechanisms that have emerged: perturbation of the TGF-β signalling pathway, disruption of the vascular smooth muscle cell (VSMC) contractile apparatus, and impairment of extracellular matrix synthesis. Because smooth muscle cells and proteins of the extracellular matrix directly regulate TGF-β signalling, this latter pathway emerges as a key component of thoracic aortic disease initiation and progression. These discoveries have revolutionized our understanding of thoracic aortic disease and provided inroads toward gene-specific stratification of treatment. Last, we outline how these genetic findings are translated into novel pharmaceutical approaches for thoracic aortic disease.

Evidence of Aortopathy in Mice with Haploinsufficiency of Notch1 in Nos3-Null Background

Thoracic aortic aneurysms (TAA) are a significant cause of morbidity and mortality in humans. While the exact etiology is unknown, genetic factors play an important role. Mutations in NOTCH1 have been linked to bicuspid aortic valve (BAV) and aortopathy in humans. The aim of this study was to determine if haploinsufficiency of Notch1 contributes to aortopathy using Notch1^+/−; Nos3^−/− mice. Echocardiographic analysis of Notch1^+/−; Nos3^−/− mice reveals effacement of the sinotubular junction and a trend toward dilation of the aortic sinus. Furthermore, examination of the proximal aorta of Notch1^+/−; Nos3^−/− mice reveals elastic fiber degradation, a trend toward increased matrix metalloproteinase 2 expression, and increased smooth muscle cell apoptosis, features characteristic of aneurysmal disease. Although at a lower penetrance, we also found features consistent with aortopathic changes in Notch1 heterozygote mice and in Nos3-null mice. Our findings implicate a novel role for Notch1 in aortopathy of the proximal aorta.

Genetics of ischaemic stroke in young adults

Background

Stroke may be a clinical expression of several inherited disorders in humans. Recognition of the underlined genetic disorders causing stroke is important for a correct diagnosis, for genetic counselling and, even if rarely, for a correct therapeutic management. Moreover, the genetics of complex diseases such the stroke, in which multiple genes interact with environmental risk factors to increase risk, has been revolutionized by the Genome-Wide Association Study (GWAS) approach.

Scope of review

Here we review the single-gene causes of ischemic stroke, bringing the reader from the candidate gene method toward the exciting new horizons of genetic technology.

Major conclusions

The aetiological diagnosis of ischemic stroke in young adults is more complex than in the elderly. The identification of a genetic cause is important to provide appropriate counseling and to start a correct therapy, when available. The advent of GWAS technology, such as for other complex pathological conditions, has contributed enormously to the understanding of many of these genetic bases. For success large, well phenotyped case cohorts are required, and international collaborations are essential.

General significance

This review focuses on the main causes of genetically-based ischemic stroke in young adults, often classified as indeterminate, investigating also the recent findings of the GWAS, in order to improve diagnostic and therapeutic management.

•

The aetiological diagnosis of stroke in young adults needs a different and more complex diagnostic work up than in older adults.

•

Stroke may be a clinical expression of several inherited disorders in humans.

•

The most common genetic causes of stroke are CADASIL, Fabry and mitochondrial diseases.

•

Recognition of the underlined genetic disorders causing stroke is important for the correct management of the patient.

Molecular mechanisms of inherited thoracic aortic disease - from gene variant to surgical aneurysm

Aortic dissection is a catastrophic event that has a high mortality rate. Thoracic aortic aneurysms are the clinically silent precursor that confers an increased risk of acute aortic dissection. There are several gene mutations that have been identified in key structural and regulatory proteins within the aortic wall that predispose to thoracic aneurysm formation. The most common and well characterised of these is the FBN1 gene mutation that is known to cause Marfan syndrome. Others less well-known mutations include TGF-β1 and TGF-β2 receptor mutations that cause Loeys-Dietz syndrome, Col3A1 mutations causing Ehlers-Danlos Type 4 syndrome and Smad3 and-4, ACTA2 and MYHII mutations that cause familial thoracic aortic aneurysm and dissection. Despite the variation in the proteins affected by these genetic mutations, there is a unifying pathological end point of medial degeneration within the wall of the aorta characterised by vascular smooth muscle cell loss, fragmentation and loss of elastic fibers, and accumulation of proteoglycans and glycosaminoglycans within vascular smooth muscle cell-depleted areas of the aortic media. Our understanding of these mutations and their post-translational effects has led to a greater understanding of the pathophysiology that underlies thoracic aortic aneurysm formation. Despite this, there are still many unanswered questions regarding the molecular mechanisms. Further elucidation of the signalling pathways will help us identify targets that may be suitable modifiers to enhance treatment of this often fatal condition.