Activation of the alternative complement pathway modulates inflammation in thoracic aortic aneurysm/dissection.

Thoracic aortic aneurysm/dissection (TAAD) is a lethal vascular disease, and several pathological factors participate in aortic medial degeneration. We previously discovered that the complement C3a-C3aR axis in smooth muscle cells promotes the development of thoracic aortic dissection (TAD) through regulation of matrix metalloproteinase 2. However, discerning the specific complement pathway that is activated and elucidating how inflammation of the aortic wall is initiated remain unknown. We ascertained that the plasma levels of C3a and C5a were significantly elevated in patients with TAD and that the levels of C3a, C4a, and C5a were higher in acute TAD than in chronic TAD. We also confirmed the activation of the complement in a TAD mouse model. Subsequently, knocking out Cfb (Cfb) or C4 in mice with TAD revealed that the alternative pathway and Cfb played a significant role in the TAD process. Activation of the alternative pathway led to generation of the anaphylatoxins C3a and C5a, and knocking out their receptors reduced the recruitment of inflammatory cells to the aortic wall. Moreover, we used serum from wild-type mice or recombinant mice Cfb as an exogenous source of Cfb to treat Cfb KO mice and observed that it exacerbated the onset and rupture of TAD. Finally, we knocked out Cfb in the FBN1C1041G/+ Marfan-syndrome mice and showed that the occurrence of TAA was reduced. In summary, the alternative complement pathway promoted the development of TAAD by recruiting infiltrating inflammatory cells. Targeting the alternative pathway may thus constitute a strategy for preventing the development of TAAD.NEW & NOTEWORTHY The alternative complement pathway promoted the development of TAAD by recruiting infiltrating inflammatory cells. Targeting the alternative pathway may thus constitute a strategy for preventing the development of TAAD.

Reviewing hereditary connective tissue disorders: Proposals of harmonic medicolegal assessments.

Hereditary connective tissue disorders (HCTDs) are a heterogeneous group of inherited diseases. These disorders show genetic mutations with loss of function of primary components of connective tissue, such as collagen and elastic fibers. There are more than 200 conditions that involve hereditary connective tissue disorders, while the most known are Marfan syndrome, Osteogenesis Imperfecta, and Ehlers-Danlos syndromes. These disorders need continuous updates, multidisciplinary skills, and specific methodologic evaluations sharing many medicolegal issues. Marfan syndrome and Ehlers-Danlos syndromes show a high risk of early sudden death. As a consequence of this, postmortem genetic testing can identify novel genotype-phenotype correlations which help the clinicians to assess personalized cardiovascular screening programs among the ill subjects. Genetic testing is also essential to identify children suffering from Osteogenesis Imperfecta, especially when a physical abuse is clinically suspected. However, this is a well-known clinical problem even though there are still challenges to interpret genetic data and variants of unknown significance due to the current extensive use of new genetic/genomic techniques. Additionally, the more significant applications and complexities of genomic testing raise novel responsibilities on the clinicians, geneticists, and forensic practitioners as well, increasing potential liability and medical malpractice claims. This systematic review provides a detailed overview on how multidisciplinary skills belonging to clinicians, medicolegal consultants, radiologists, and geneticists can cooperate to manage HCTDs from autopsy or clinical findings to genetic testing. Thus, technical aspects need to be addressed to the medicolegal community since there is no consensus works or guidelines which specifically discuss these issues.

Aortic Dissection and a Previously Unreported ACTA2 Missense Variant Mutation in a Young Patient: A Case Report.

Hereditary connective tissue disease is known to cause aortic lesions at an early age. Familial aortic aneurysm/dissection is caused due to an ACTA2 mutation that affects smooth muscle structure. We present a case of a 15-year-old boy with a mild developmental disorder in whom no abnormalities were identified on previous physical examinations. The patient presented with severe left heart failure, extensive dissection from the ascending aorta to the common iliac artery, and myocardial and cerebral infarctions. He underwent an urgent Bentall surgery. Six months later, the patient underwent surgical reconstruction of the abdominal aorta from the aortic arch and returned to normal daily activities. Pathological examination demonstrated the absence of elastic fibers but presence of abundant reticular fibers and mucopolysaccharides from the tunica intima to the media. Genetic testing revealed a heterozygous missense variant of the ACTA2 gene. To the best of our knowledge, this is the first sporadic case of structurally abnormal smooth muscle organization resulting in clinical symptoms with no previously reported pathogenicity.

Prevention of aortic dissection and aneurysm via an ALDH2-mediated switch in vascular smooth muscle cell phenotype.

AIMS: Aortic aneurysm/dissection (AAD) is a life-threatening disorder lacking effective pharmacotherapeutic remedies. Aldehyde dehydrogenase 2 (ALDH2) polymorphism is tied with various risk factors for AAD including hypertension, atherosclerosis, and hypercholesterolaemia although direct correlation between the two remains elusive. METHODS AND RESULTS: Two independent case-control studies were conducted involving 307 AAD patients and 399 healthy controls in two geographically distinct areas in China. Our data revealed that subjects carrying mutant ALDH2 gene possessed a ∼50% reduced risk of AAD compared with wild-type (WT) alleles. Using 3-aminopropionitrile fumarate (BAPN)- and angiotensin II (Ang II)-induced AAD animal models, inhibition of ALDH2 was found to retard development of AAD. Mechanistically, ALDH2 inhibition ablated pathological vascular smooth muscle cell (VSMC) phenotypical switch through interaction with myocardin, a determinant of VSMC contractile phenotype. Using microarray and bioinformatics analyses, ALDH2 deficiency was found to down-regulate miR-31-5p, which further altered myocardin mRNA level. Gain-of-function and loss-of-function studies verified that miR-31-5p significantly repressed myocardin level and aggravated pathological VSMC phenotypical switch and AAD, an effect that was blunted by ALDH2 inhibition. We next noted that ALDH2 deficiency increased Max expression and decreased miR-31-5p level. Moreover, ALDH2 mutation or inhibition down-regulated levels of miR-31-5p while promoting myocardin downstream contractile genes in the face of Ang II in primary human VSMCs. CONCLUSIONS: ALDH2 deficiency is associated with a lower risk of AAD in patients and mice, possibly via suppressing VSMC phenotypical switch in a miR-31-5p-myocardin-dependent manner. These findings favour a role for ALDH2 and miR-31-5p as novel targets for AAD therapy.

Smooth Muscle Sirtuin 1 Blocks Thoracic Aortic Aneurysm/Dissection Development in Mice.

PURPOSE: Advancing age is the major risk factor for thoracic aortic aneurysm/dissection (TAAD). However, the causative link between age-related molecules and TAAD remains elusive. Here, we investigated the role of Sirtuin 1 (SIRT1, also known as class III histone deacetylase), the best studied member of the longevity-related Sirtuin family, in TAAD development in vivo. METHODS: We used male smooth muscle-specific SIRT1 transgenic (ST-Tg) mice, smooth muscle-specific SIRT1 knockout (ST-KO) mice, and their wild-type (WT) littermates on a C57BL/6J background to establish a TAAD model induced by oral administration of 3-aminopropionitrile fumarate (BAPN). We analyzed the incidence and fatality rates of TAAD in the groups. We examined matrix metallopeptidase 2 (MMP2) and MMP9 expression in aortas or cultured A7r5 cells via western blotting and real-time polymerase chain reaction (PCR). We performed chromatin immunoprecipitation (ChIP) to clarify the epigenetic mechanism of SIRT1-regulated MMP2 expression in vascular smooth muscle cells (VSMCs). RESULTS: BAPN treatment markedly increased the incidence of TAAD in WT mice but caused less disease in ST-Tg mice. Moreover, ST-KO mice had the highest BAPN-induced TAAD fatality rate of all the groups. Mechanistically, SIRT1 overexpression resulted in lower MMP2 and MMP9 expression after BAPN treatment in both mouse aortas and cultured A7r5 cells. The downregulation of BAPN-induced MMP2 expression by SIRT1 was mediated by deacetylation of histone H3 lysine 9 (H3K9) on the Mmp2 promoter in the A7r5 cells. CONCLUSION: Our findings suggest that SIRT1 expression in SMCs protects against TAAD and could be a novel therapeutic target for TAAD management.

Sustained activation of ADP/P2ry12 signaling induces SMC senescence contributing to thoracic aortic aneurysm/dissection.

Thoracic aortic aneurysm/dissection (TAAD) is characterized by excessive smooth muscle cell (SMC) loss, extracellular matrix (ECM) degradation and inflammation. However, the mechanism whereby signaling leads to SMC loss is unclear. We used senescence-associated (SA)-ß-gal staining and analysis of expression of senescence-related proteins (p53, p21, p19) to show that excessive mechanical stretch (20% elongation, 3600cycles/h, 48h) induced SMC senescence. SMC senescence was also detected in TAAD specimens from both mice and humans. High-performance liquid chromatography and luciferin-luciferase-based assay revealed that excessive mechanical stretch increased adenosine diphosphate (ADP) release from SMCs both in vivo and in vitro. Elevated ADP induced SMC senescence while genetic knockout of the ADP receptor, P2Y G protein-coupled receptor 12 (P2ry12), in mice protected against SMC senescence and inflammation. Both TAAD formation and rupture were significantly reduced in P2ry12-/- mice. SMCs from P2ry12-/- mice were resistant to senescence induced by excessive mechanical stretch or ADP treatment. Mechanistically, ADP treatment sustained Ras activation, whereas pharmacological inhibition of Ras protected against SMC senescence and reduced TAAD formation. Taken together, excessive mechanical stress may induce a sustained release of ADP and promote SMC senescence via P2ry12-dependent sustained Ras activation, thereby contributing to excessive inflammation and degeneration, which provides insights into TAAD formation and progression.

Mechanical stretch-induced endoplasmic reticulum stress, apoptosis and inflammation contribute to thoracic aortic aneurysm and dissection.

Thoracic aortic aneurysm/dissection (TAAD) is characterized by excessive smooth muscle cell (SMC) loss, extracellular matrix (ECM) degradation and inflammation. In response to certain stimuli, endoplasmic reticulum (ER) stress is activated and regulates apoptosis and inflammation. Excessive apoptosis promotes aortic inflammation and degeneration, leading to TAAD. Therefore, we studied the role of ER stress in TAAD formation. A lysyl oxidase inhibitor, 3-aminopropionitrile fumarate (BAPN), was administrated to induce TAAD formation in mice, which showed significant SMC loss (α-SMA level). Excessive apoptosis (TUNEL staining) and ER stress (ATF4 and CHOP), along with inflammation, were present in TAAD samples from both mouse and human. Transcriptional profiling of SMCs after mechanical stress demonstrated the expression of genes for ER stress and inflammation. To explore the causal role of ER stress in initiating degenerative signalling events and TAAD, we treated wild-type (CHOP(+/+)) or CHOP(-/-) mice with BAPN and found that CHOP deficiency protected against TAAD formation and rupture, as well as reduction in α-SMA level. Both SMC apoptosis and inflammation were significantly reduced in CHOP(-/-) mice. Moreover, SMCs isolated from CHOP(-/-) mice were resistant to mechanical stress-induced apoptosis. Taken together, our results demonstrated that mechanical stress-induced ER stress promotes SMCs apoptosis, inflammation and degeneration, providing insight into TAAD formation and progression.

Histone deacetylase 9-mediated phenotypic transformation of vascular smooth muscle cells is a potential target for treating aortic aneurysm/dissection.

Aortic aneurysm/dissection (AAD) is a serious cardiovascular condition characterized by rapid onset and high mortality rates. Currently, no effective drug treatment options are known for AAD. AAD pathogenesis is associated with the phenotypic transformation and abnormal proliferation of vascular smooth muscle cells (VSMCs). However, endogenous factors that contribute to AAD progression remain unclear. We aimed to investigate the role of histone deacetylase 9 (HDAC9) in AAD pathogenesis. HDAC9 expression was considerably increased in human thoracic aortic dissection specimens. Using RNA-sequencing (RNA-seq) and chromatin immunoprecipitation, we demonstrated that HDAC9 transcriptionally inhibited the expression of superoxide dismutase 2 and insulin-like growth factor-binding protein-3, which are critically involved in various signaling pathways. Furthermore, HDAC9 triggered the transformation of VSMCs from a systolic to synthetic phenotype, increasing their proliferation and migration abilities and suppressing their apoptosis. Consistent with these results, in vivo experiments revealed that TMP195, a pharmacological inhibitor of HDAC9, suppressed the formation of the ß-aminopropionitrile-induced AAD phenotype in mice. Our findings indicate that HDAC9 may be a novel endogenous risk factor that promotes the onset of AAD by mediating the phenotypic transformation of VSMCs. Therefore, HDAC9 may serve as a potential therapeutic target for drug-based AAD treatment. Furthermore, TMP195 holds potential as a therapeutic agent for AAD treatment.

Inducing aortic aneurysm/dissection in zebrafish: evaluating the efficacy of ß-Aminopropionic Nitrile as a model.

Aortic aneurysm/dissection (AAD) poses a life-threatening cardiovascular emergency with complex mechanisms and a notably high mortality rate. Zebrafish (Danio rerio) serve as valuable models for AAD due to the conservation of their three-layered arterial structure and genome with that of humans. However, the existing studies have predominantly focused on larval zebrafish, leaving a gap in our understanding of adult zebrafish. In this study, we utilized ß-Aminopropionic Nitrile (BAPN) impregnation to induce AAD in both larval and adult zebrafish. Following induction, larval zebrafish exhibited a 28% widening of the dorsal aortic diameter (p < 0.0004, n = 10) and aortic arch malformations, with a high malformation rate of 75% (6/8). Conversely, adult zebrafish showed a 41.67% (5/12) mortality rate 22 days post-induction. At this time point, the dorsal aortic area had expanded by 2.46 times (p < 0.009), and the vessel wall demonstrated significant thickening (8.22 ± 2.23 µM vs. 26.38 ± 10.74 µM, p < 0.05). Pathological analysis revealed disruptions in the smooth muscle layer, contributing to a 58.33% aneurysm rate. Moreover, the expression levels of acta2, tagln, cnn1a, and cnn1b were decreased, indicating a weakened contractile phenotype. Transcriptome sequencing showed a significant overlap between the molecular features of zebrafish tissues post-BAPN treatment and those of AAD patients. Our findings present a straightforward and practical method for generating AAD models in both larval and adult zebrafish using BAPN.

Methamphetamine induces thoracic aortic aneurysm/dissection through C/EBPß.

AIMS: Thoracic aortic aneurysm/dissection (TAAD) is a life-threatening disease with diverse clinical manifestations. Although the association between methamphetamine (METH) and TAAD is frequently observed, the causal relationship between METH abuse and aortic aneurysm/dissection has not been established. This study was designed to determine if METH causes aortic aneurysm/dissection and delineate the underlying mechanism. METHODS AND RESULTS: A new TAAD model was developed by exposing METH to SD rats pre-treated with lysyl oxidase inhibitor ß-aminopropionitrile (BAPN). Combination of METH and BAPN caused thoracic aortic aneurysm/dissection in 60% of rats. BAPN+METH significantly increased the expression and activities of both matrix metalloproteinase MMP2 and MMP9, consistent with the severe elastin breakage and dissection. Mechanistically, METH increased CCAAT-enhancer binding protein ß (C/EBPß) expression by enhancing mothers against decapentaplegic homolog 3 (Smad3) and extracellular regulated protein kinase (ERK1/2) signaling. METH also promoted C/EBPß binding to MMP2 and MMP9 promoters. Blocking C/EBPß significantly attenuated METH+BAPN-induced TAAD and MMP2/MMP9 expression. Moreover, BAPN+METH promoted aortic medial smooth muscle cell (SMC) apoptosis through C/EBPß-mediated IGFBP5/p53/PUMA signaling pathways. More importantly, the expression of C/EBPß, MMP2/MMP9, and apoptosis-promoting proteins was increased in the aorta of human patients with thoracic aortic dissection, suggesting that the mechanisms identified in animal study could be relevant to human disease. CONCLUSIONS: Our study demonstrated that METH exposure has a casual effect on TAAD. C/EBPß mediates METH-introduced TAAD formation by causing elastin breakage, medial cell loss and degeneration. Therefore, C/EBPß may be a potential factor for TAAD clinical diagnosis or treatment.

A novel variant in fibrillin-1 is responsible for early-onset familial thoracic aortic aneurysms in Marfan patients.

BACKGROUND: Marfan syndrome (MFS) is an inherited connective tissue disorder that affects the skeletal, ocular, and cardiovascular system. The disease's severity and clinical manifestations vary greatly due to pathogenic variants which, combined with a lack of research on the correlation between MFS's genotype and phenotype, make MFS a challenging disease to diagnose. This study aims to further the understanding of MFS by shedding light on the clinical manifestation of a novel variant in fibrillin-1 (FBN1)-the protein responsible for the genetic defects that lead to MFS. METHODS: A patient was diagnosed with MFS by combining a clinical examination (based on the 2010 revision to Ghent nosology criteria) with a targeted next-generation sequence analysis. The functional analysis of the causal mutation and the clinical details of the affected patient were then analyzed. RESULTS: The FBN1 heterozygous variant c.5081_5082insT, which is known to delete large fragments from amino acids 1702 to 2871, was found in the proband patient and her son. The two also displayed the skeletal and cardiovascular manifestations of MFS. In addition, the 14-year-old son was identified as having a dilated aortic bulb at the same rupture site of the proband's dissection, and the proband's mother also died at age 32 due to aortic dissection. CONCLUSIONS: The FBN1 variant c.5081_5082insT (p.Leu1694fs*9) is a pathogenic mutation that can cause MFS patients to experience early-onset familial thoracic aortic aneurysms (TAA). We hope that this discovery can provide further insight into the treatment of MFS patients with truncating variants in exons 42-65.

Direct proximal right subclavian artery cannulation during surgery of the thoracic aorta.

OBJECTIVE: To evaluate outcomes of single sternum access for right subclavian artery cannulation without infraclavicular incision in surgery of the thoracic aorta. METHODS: Between January 2015 and December 2019, 44 consecutive patients underwent surgery of the thoracic aorta with cannulation of the right subclavian artery, after sternotomy and before pericardiotomy, through a direct percutaneous cannula with a single access without additional infraclavicular skin incision. The indication for surgery was type A acute aortic dissection in 29 patients (65.9%), proximal aortic aneurysm in 11 (25%), and aneurysm of the aortic arch in 4 (9%). Operative procedures were replacement of the ascending aorta in 23 patients, Bentall procedure in 10, hemiarch replacement in 6, and total arch replacement in 5. The mean cardiopulmonary bypass (CPB) and cross-clamp times were 185 ± 62 minutes and 138 ± 41 minutes, respectively. RESULTS: The in-hospital mortality rate was 6.8%. Permanent neurologic dysfunction occurred in 3 patients (6.8%) and temporary neurologic dysfunction occurred in 4 patients (9.0%). There were no vascular complications related to this technique. No lesions to the vagus and recurrent laryngeal nerves have been reported. CONCLUSIONS: In our experience, a single sternum access for right subclavian artery cannulation avoids the risk and complications of an infraclavicular incision required for axillary artery cannulation. This technique is safe and represent a valid option for CBP and antegrade cerebral perfusion during surgery of the thoracic aorta.

Detection of ten novel FBN1 mutations in Chinese patients with typical or incomplete Marfan syndrome and an overview of the genotype-phenotype correlations.

OBJECTIVE: The aim of this study is to identify the mutation spectrum of FBN1 in patients with Marfan syndrome (MFS) or Marfan-Like Phenotypes and to analyze the genotype-phenotype correlations of existing literature. METHODS AND RESULTS: A total of 21 unrelated patients with a definite or suspected clinical diagnosis of MFS were recruited for research. Eleven FBN1 mutations were identified in 12 patients who strictly fulfilled the Ghent criteria for MFS, and 1 FBN1 mutations were detected in 9 patients with suspected MFS by screening the mutations of FBN1. These FBN1 mutations include 10 novel mutations (c.357 C>A, c.493 C>T, c.1374 T>A, c.4143 delG, c. 6987 C>G, c.7238 G>A, c. 7765 A>G, c.8200 A>G, c. 8431 G>A, c.8547 T>G,) and 2 previously reported mutations (c.4567 C>T, c.4615 C>T). By searching PubMed and Embase (from 1990 up to December 2018), twenty nine studies (including the present study) with 890 subjects with MFS or Marfan-like phenotypes were included to analyze the genotype-phenotype correlations. Several genotype-phenotype correlations were founded. Firstly, mutations of premature termination codons (PTC) were associated with an increased risk of major cardiovascular involvements. Secondly, the frequency of patients with major cardiovascular involvement in exons 43-65 group was as high as that in exons 24-32 group (71.4% vs. 77.0%; p = 0.238). Finally, cysteine missense mutations might be associated with major cardiovascular involvements. CONCLUSIONS: These results extended the FBN1 mutation spectrum of this rare disease and revealed the genotype-phenotype correlations in MFS by analyzing existing literature.