Single-Molecule Spatial Transcriptomics of Human Thoracic Aortic Aneurysms Uncovers Calcification-Related CARTPT-Expressing Smooth Muscle Cells.

BACKGROUND: Although single-cell RNA-sequencing is commonly applied to dissect the heterogeneity in human tissues, it involves the preparation of single-cell suspensions via cell dissociation, causing loss of spatial information. In this study, we employed high-resolution single-cell transcriptome imaging to reveal rare smooth muscle cell (SMC) types in human thoracic aortic aneurysm (TAA) tissue samples. METHODS: Single-molecule spatial distribution of transcripts from 140 genes was analyzed in fresh-frozen human TAA samples with region and sex-matched controls. In vitro studies and tissue staining were performed to examine human CART prepropeptide (CARTPT) regulation and function. RESULTS: We captured thousands of cells per sample including a spatially distinct CARTPT-expressing SMC subtype enriched in male TAA samples. Immunoassays confirmed human CART (cocaine- and amphetamine-regulated transcript) protein enrichment in male TAA tissue and truncated CARTPT secretion into cell culture medium. Oxidized low-density lipoprotein, a cardiovascular risk factor, induced CARTPT expression, whereas CARTPT overexpression in human aortic SMCs increased the expression of key osteochondrogenic transcription factors and reduced contractile gene expression. Recombinant human CART treatment of human SMCs further confirmed this phenotype. Alizarin red staining revealed calcium deposition in male TAA samples showing similar localization with human CART staining. CONCLUSIONS: Here, we demonstrate the feasibility of single-molecule imaging in uncovering rare SMC subtypes in the diseased human aorta, a difficult tissue to dissociate. We identified a spatially distinct CARTPT-expressing SMC subtype enriched in male human TAA samples. Our functional studies suggest that human CART promotes osteochondrogenic switch of aortic SMCs, potentially leading to medial calcification of the thoracic aorta.

Loss of TIMP3, but not TIMP4, exacerbates thoracic and abdominal aortic aneurysm.

AIMS: Aorta exhibits regional heterogeneity (structural and functional), while different etiologies for thoracic and abdominal aortic aneurysm (TAA, AAA) are recognized. Tissue inhibitor of metalloproteinases (TIMPs) regulate vascular remodeling through different mechanisms. Region-dependent functions have been reported for TIMP3 and TIMP4 in vascular pathologies. We investigated the region-specific function of these TIMPs in development of TAA versus AAA. METHODS & RESULTS: TAA or AAA was induced in male and female mice lacking TIMP3 (Timp3-/-), TIMP4 (Timp4-/-) or in wildtype (WT) mice by peri-adventitial elastase application. Loss of TIMP3 exacerbated TAA and AAA severity in males and females, with a greater increase in proteinase activity, smooth muscle cell phenotypic switching post-AAA and -TAA, while increased inflammation was detected in the media post-AAA, but in the adventitia post-TAA. Timp3-/- mice showed impaired intimal barrier integrity post-AAA, but a greater adventitial vasa-vasorum branching post-TAA, which could explain the site of inflammation in AAA versus TAA. Severity of TAA and AAA in Timp4-/- mice was similar to WT mice. In vitro, Timp3 knockdown more severely compromised the permeability of human aortic EC monolayer compared to Timp4 knockdown or the control group. In aneurysmal aorta specimens from patients, TIMP3 expression decreased in the media in AAA, and in adventitial in TAA specimens, consistent with the impact of its loss in AAA versus TAA in mice. CONCLUSION: TIMP3 loss exacerbates inflammation, adverse remodeling and aortic dilation, but triggers different patterns of remodeling in AAA versus TAA, and through different mechanisms.

Familial Associations of Prevalence and Cause-Specific Mortality for Thoracic Aortic Disease and Bicuspid Aortic Valve in a Large-Population Database.

BACKGROUND: Thoracic aortic disease and bicuspid aortic valve (BAV) likely have a heritable component, but large population-based studies are lacking. This study characterizes familial associations of thoracic aortic disease and BAV, as well as cardiovascular and aortic-specific mortality, among relatives of these individuals in a large-population database. METHODS: In this observational case-control study of the Utah Population Database, we identified probands with a diagnosis of BAV, thoracic aortic aneurysm, or thoracic aortic dissection. Age- and sex-matched controls (10:1 ratio) were identified for each proband. First-degree relatives, second-degree relatives, and first cousins of probands and controls were identified through linked genealogical information. Cox proportional hazard models were used to quantify the familial associations for each diagnosis. We used a competing-risk model to determine the risk of cardiovascular-specific and aortic-specific mortality for relatives of probands. RESULTS: The study population included 3 812 588 unique individuals. Familial hazard risk of a concordant diagnosis was elevated in the following populations compared with controls: first-degree relatives of patients with BAV (hazard ratio [HR], 6.88 [95% CI, 5.62-8.43]); first-degree relatives of patients with thoracic aortic aneurysm (HR, 5.09 [95% CI, 3.80-6.82]); and first-degree relatives of patients with thoracic aortic dissection (HR, 4.15 [95% CI, 3.25-5.31]). In addition, the risk of aortic dissection was higher in first-degree relatives of patients with BAV (HR, 3.63 [95% CI, 2.68-4.91]) and in first-degree relatives of patients with thoracic aneurysm (HR, 3.89 [95% CI, 2.93-5.18]) compared with controls. Dissection risk was highest in first-degree relatives of patients who carried a diagnosis of both BAV and aneurysm (HR, 6.13 [95% CI, 2.82-13.33]). First-degree relatives of patients with BAV, thoracic aneurysm, or aortic dissection had a higher risk of aortic-specific mortality (HR, 2.83 [95% CI, 2.44-3.29]) compared with controls. CONCLUSIONS: Our results indicate that BAV and thoracic aortic disease carry a significant familial association for concordant disease and aortic dissection. The pattern of familiality is consistent with a genetic cause of disease. Furthermore, we observed higher risk of aortic-specific mortality in relatives of individuals with these diagnoses. This study provides supportive evidence for screening in relatives of patients with BAV, thoracic aneurysm, or dissection.

Urate-Lowering Therapy Inhibits Thoracic Aortic Aneurysm and Dissection Formation in Mice.

BACKGROUND: Thoracic aortic aneurysm and dissection (TAAD) is a highly lethal vascular disease without effective drug therapy. Whether elevated serum concentrations of uric acid are involved in TAAD development remains unclear. METHODS: Serum uric acid levels were detected in different TAAD mouse models and patients. The urate-lowering drug allopurinol was administered in the drinking water of TAAD mice. Adenine diet-induced mice were established to investigate the role of hyperuricemia in TAAD formation and RNA-sequencing of thoracic aortas from these mice was performed. RESULTS: We found serum uric acid levels were elevated in various mouse TAAD models, including mice fed a ß-aminopropionitrile diet, Marfan mice with fibrillin-1 haploinsufficiency (Fbn1C1041G/+), and ApoE-/- mice infused with Ang II (angiotensin II), as well as in patients with TAAD. Administration of urate-lowering drug allopurinol in the drinking water significantly alleviated TAAD formation in ß-aminopropionitrile-treated mice, Fbn1C1041G/+ mice, and Ang II-infused ApoE-/- mice. Moreover, an adenine diet was used to induce hyperuricemia in mice. Intriguingly, a 4-week adenine diet feeding directly induced TAAD formation characterized by increased maximal thoracic aortic diameters and severe elastin degradation, which were ameliorated by allopurinol. Unbiased RNA-sequencing in mouse thoracic aortas suggested that FcγR (Fc gamma receptor) was upregulated upon adenine diet, but reciprocally repressed by allopurinol. Mechanistically, hyperuricemia activated FcγR-mediated ERK1/2 (extracellular signal-regulated kinase 1/2) phosphorylation to induce macrophage inflammation and TAAD development, which was abrogated by allopurinol or FcγR deficiency. CONCLUSIONS: This study uncovered an important and previously unrecognized role of hyperuricemia in mediating the pathogenesis of TAAD, and uric acid-lowering drug may represent a promising therapeutic approach for TAAD.

Impact of Reconstructing Intercostal Artery on Spinal Cord Circulation During Open Surgery for Thoracoabdominal Aortic Aneurysm

ABSTRACT Introduction: We evaluated the outcomes of the selective intercostal artery reconstruction for preventing spinal cord injury during thoracoabdominal aortic aneurysm repair. Methods: We retrospectively assessed 84 consecutive patients who underwent thoracoabdominal aortic aneurysm repairs between 2004 and 2016. The mean age of the patients was 57.3 years. We performed preoperative multidetector computed tomography in 74 patients (88.0%) to identify the Adamkiewicz artery. Spinal cord injury preventive measures included motor evoked potential monitoring, hypothermia induction, Adamkiewicz artery or other intercostal artery reconstruction, and cerebrospinal fluid drainage. Results: The hospital death rate was 5.9%, and paraplegia occurred in four patients (4.7%). The Adamkiewicz artery or other intercostal arteries were reconstructed selectively in 46 patients (54.7%). Of these patients, 41 underwent postoperative multidetector computed tomography, which revealed occlusion of the reconstructed grafts in 23 patients (56.0%). There was no paraplegia in the patients who underwent reconstruction of the Adamkiewicz artery, which was patent on postoperative multidetector computed tomography. Univariate analysis showed no significant effect of various risk factors on the development of spinal cord injury. Conclusion: Outcome of open surgery for thoracoabdominal aortic aneurysm in our institution regarding spinal cord injury was satisfactory. The benefits of Adamkiewicz artery reconstruction remain inconclusive, and further larger studies are required to identify its validation for spinal cord protection in thoracoabdominal aortic aneurysm repair.

Impact of Reconstructing Intercostal Artery on Spinal Cord Circulation During Open Surgery for Thoracoabdominal Aortic Aneurysm.

INTRODUCTION: We evaluated the outcomes of the selective intercostal artery reconstruction for preventing spinal cord injury during thoracoabdominal aortic aneurysm repair. METHODS: We retrospectively assessed 84 consecutive patients who underwent thoracoabdominal aortic aneurysm repairs between 2004 and 2016. The mean age of the patients was 57.3 years. We performed preoperative multidetector computed tomography in 74 patients (88.0%) to identify the Adamkiewicz artery. Spinal cord injury preventive measures included motor evoked potential monitoring, hypothermia induction, Adamkiewicz artery or other intercostal artery reconstruction, and cerebrospinal fluid drainage. RESULTS: The hospital death rate was 5.9%, and paraplegia occurred in four patients (4.7%). The Adamkiewicz artery or other intercostal arteries were reconstructed selectively in 46 patients (54.7%). Of these patients, 41 underwent postoperative multidetector computed tomography, which revealed occlusion of the reconstructed grafts in 23 patients (56.0%). There was no paraplegia in the patients who underwent reconstruction of the Adamkiewicz artery, which was patent on postoperative multidetector computed tomography. Univariate analysis showed no significant effect of various risk factors on the development of spinal cord injury. CONCLUSION: Outcome of open surgery for thoracoabdominal aortic aneurysm in our institution regarding spinal cord injury was satisfactory. The benefits of Adamkiewicz artery reconstruction remain inconclusive, and further larger studies are required to identify its validation for spinal cord protection in thoracoabdominal aortic aneurysm repair.

A preliminary experience of retroperitoneal approach by partial resection of the tenth rib for repairing Crawford type Ⅳ thoracoabdominal aortic aneurysm and complex abdominal aortic aneurysm / 中华普通外科杂志

Objective:To evaluate a surgical approach for partial resection of the tenth rib through a retroperitoneal approach for the exposure of Crawford type IV thoracoabdominal aortic aneurysm and complex abdominal aortic aneurysm from 2014 to 2019.Methods:A retrospective analysis was conducted on clinical data and follow-up results of 7 patients who underwent treatment for Crawford type IV thoracoabdominal aortic aneurysm and complex abdominal aortic aneurysm through partial resection of the tenth rib via a retroperitoneal approach.Results:One case (14.3%) had associated Marfan syndrome, and 5 cases (71.4%) underwent left renal artery reconstruction. None of the patients experienced severe complications such as cardiopulmonary complications or renal failure postoperatively, and there was no statistically significant difference in serum creatinine levels between preoperative and postoperative stages during hospitalization ( P=0.205). Follow-up examinations showed no long-term vascular stenosis. Conclusions:Partial resection of the tenth rib through a retroperitoneal approach can avoid incisions of the pleura and diaphragm. It allows for the exposure of the aorta below the diaphragm and has the ability to treat aortic diseases below the diaphragm with smaller incisions and lower complication risks.

3D printing-assisted pre-fenestration and branch stent endovascular repair for the treatment of thoracoabdominal aortic aneurysms / 中华普通外科杂志

Objective:To evaluate the safety and efficacy of 3D printing-assisted pre-fenestration and branch stent endovascular repair (F/b EVAR) in the treatment of thoracoabdominal aortic aneurysms.Methods:The clinical data of 26 patients treated with 3D printing-assisted F/b EVAR for complicated thoracic and abdominal aortic diseases at the Department of Vascular Surgery, the Ninth People's Hospital,Shanghai Jiaotong University School of Medicine from May 2019 to Sep 2022 were retrospectively analyzed.Results:The success rate in these 26 cases of TAAA with 3D printing combined with F/b EVAR was 97.89%, and the mean follow-up time was (8.03±4.15) months. Four cases had Ⅲc internal leakage and disappeared during the follow-up. One case of type Ⅲ leakage were narrowed during follow-up. Ic type internal leakage occurred in 1 patient and disappeared after the addition of a stent at the distal end. During the follow-up period, aortic CTA indicated that 1 patient had renal artery stent occlusion and smooth blood in other visceral branches. No complications such as organ ischemia, lower limb ischemia and all-cause death occurred during follow-up.Conclusion:3D printing-assisted F/b EVAR minimally invasive repair of TAAA is a feasible, effective and safe technique, with high success rate and low complication rate of visceral branch artery reconstruction.

Mid term results of fenestrated branch stent technique for the treatment of thoracoabdominal aortic aneurysms / 中华普通外科杂志

Objective:To evaluate the mid-term results of fenestrated/branched endovascular aortic repair (f/b EVAR) for the treatment of thoracoabdominal aortic aneurysms. M ethods The clinical data of 105 thoracoabdominal aortic aneurysm patients treated with f/b EVAR at the Department of Vascular Surgery of Nanjing Drum Tower Hospital from 2018 to 2019 were retrospectively analyzed. Results:There were 43 cases of thoracoabdominal aortic aneurysm and 62 cases of thoracoabdominal aortic aissection.A total of 336 branch arteries were reconstructed,and technical success rate was 94.3%. 100 cases (95.2%) were followed-up, 6 cases (5.7%) received reoperation interventions, and 11 cases (10.5%) died. During the follow-up period, 69 cases had complete imaging data. Based on the recent CT date of the thoracoabdominal aorta, 58 patients hael positive aortic remodeling and 11 patients hael negative and indeterminate remodeling; there were 31 cases (29.5%) of endoleaks, including 7 cases (6.7%) of type Ⅰb endoleaks, 8 cases (7.6%) of type Ⅱ, 1 case (0.95%) of type Ⅲa, 13 cases (12.4%) of type Ⅲc endoleaks and 2 cases (1.9%) of type Ⅳ. Conclusions:The mid-term follow-up results were satisfactory for TAAA treated with f/b EVAR. Internal leakage remains key point for f/b EVAR.

Left ventricular remodeling following aortic root and ascending aneurysm repair.

Objective: Adverse left ventricular remodeling due to a mismatch between stiffness of native aortic tissue and current polyester grafts may be under-recognized. This study was conducted to evaluate the impact of proximal aortic replacement on adverse remodeling of the left ventricle. Materials and methods: All aortic root and ascending aortic aneurysm patients were identified (n = 2,001, 2006-2019). The study cohort consisted of a subset of patients (n = 98) with two or more electrocardiogram (ECG)-gated CT angiograms, but without concomitant aortic valve disease or bicuspid aortic valve, connective tissue disease, acute aortic syndrome or prior history of aortic repair or mitral valve surgery. LV myocardial mass was measured from CT data and indexed to body surface area (LVMI). The study cohort was divided into a surgery group (n = 47) and a control group; optimal medical therapy group (OMT, n = 51). Results: The mean age was 60 ± 11 years (80% male). Beta-blocker use was significantly more frequent in the surgery group (89 vs. 57%, p < 0.001), whereas, all other antihypertensive drugs were more frequent in the OMT group. The average follow-up was 9.1 ± 4.0 months for the surgery group and 13.7 ± 6.3 months for the OMT group. Average LVMI at baseline was similar in both groups (p = 0.934). LVMI increased significantly in the surgery group compared to the OMT group (3.7 ± 4.1 vs. 0.6 ± 4.4 g/m2, p = 0.001). Surgery, baseline LVMI, age, and sex were found to be independent predictors of LVMI increased on multivariable analysis. Conclusion: Proximal aortic repair with stiff polyester grafts was associated with increased LV mass in the first-year post-operative and may promote long-term adverse cardiac remodeling. Further studies should be considered to evaluate the competing effects of aortic aneurysm related mortality against risks of long-term graft induced aortic stiffening and the potential implications on current size thresholds for intervention.

Performance of a deep learning tool to detect missed aortic dilatation in a large chest CT cohort.

Purpose: Thoracic aortic (TA) dilatation (TAD) is a risk factor for acute aortic syndrome and must therefore be reported in every CT report. However, the complex anatomy of the thoracic aorta impedes TAD detection. We investigated the performance of a deep learning (DL) prototype as a secondary reading tool built to measure TA diameters in a large-scale cohort. Material and methods: Consecutive contrast-enhanced (CE) and non-CE chest CT exams with "normal" TA diameters according to their radiology reports were included. The DL-prototype (AIRad, Siemens Healthineers, Germany) measured the TA at nine locations according to AHA guidelines. Dilatation was defined as >45 mm at aortic sinus, sinotubular junction (STJ), ascending aorta (AA) and proximal arch and >40 mm from mid arch to abdominal aorta. A cardiovascular radiologist reviewed all cases with TAD according to AIRad. Multivariable logistic regression (MLR) was used to identify factors (demographics and scan parameters) associated with TAD classification by AIRad. Results: 18,243 CT scans (45.7% female) were successfully analyzed by AIRad. Mean age was 62.3 ± 15.9 years and 12,092 (66.3%) were CE scans. AIRad confirmed normal diameters in 17,239 exams (94.5%) and reported TAD in 1,004/18,243 exams (5.5%). Review confirmed TAD classification in 452/1,004 exams (45.0%, 2.5% total), 552 cases were false-positive but identification was easily possible using visual outputs by AIRad. MLR revealed that the following factors were significantly associated with correct TAD classification by AIRad: TAD reported at AA [odds ratio (OR): 1.12, p < 0.001] and STJ (OR: 1.09, p = 0.002), TAD found at >1 location (OR: 1.42, p = 0.008), in CE exams (OR: 2.1-3.1, p < 0.05), men (OR: 2.4, p = 0.003) and patients presenting with higher BMI (OR: 1.05, p = 0.01). Overall, 17,691/18,243 (97.0%) exams were correctly classified. Conclusions: AIRad correctly assessed the presence or absence of TAD in 17,691 exams (97%), including 452 cases with previously missed TAD independent from contrast protocol. These findings suggest its usefulness as a secondary reading tool by improving report quality and efficiency.

Reduction ascending aortoplasty: A retrospective analysis of outcomes and risk factors.

Objectives: Indication for Reduction of Ascending Aortoplasty (RAA) and long-term outcomes remain unclear. This study analyzed the outcomes after nonreinforced RAA in two Austrian centers. Methods: Patients with RAA at two Austrian centers between 6/2,009 and 6/2,017 were retrospectively analyzed. Aortic diameters were measured by CT pre- and post-operatively. Patients were assigned according to valve morphology and imaging modality. Results: Overall, 253 patients underwent RAA [women: 30.8%; median age 74 (63-79) years] with a mean preoperative ascending diameter of 44.7 (±3.5) mm. RAA-related postoperative adverse events occurred in 1.2% (n = 3) over a follow-up of a median of 3.8 (2.4-5.5) years: One type A aortic dissection, one lethal aortic rupture at the suture line, and one suture line bleeding with cardiac tamponade and need of surgical revision. The overall survival rate was 89.7%. Aortic valve morphology itself was no risk factor for mortality (Log-Rank: 0.942). One hundred and forty patients had a tricuspid [TAV: (55.3%)] aortic valve and 113 patients had a bicuspid aortic valve [BAV: (44.7%)]. Redilatation to a diameter >50 mm according to CT follow-up occurred in 5.7% (n = 5 of 87). One patient needed reoperation with RAA and aortic valve replacement due to a prosthesis-patient mismatch after aortic valve replacement and aortic redilatation. Conclusion: Non-reinforced RAA is a safe, feasible, and reproducible procedure with low rates of perioperative complications in selected patients primarily undergoing aortic valve repair with a dilated ascending aorta. Aortic valve morphology has no impact on mortality after RAA.

Dissecting the Heterogeneity of Human Thoracic Aortic Aneurysms Using Single-Cell Transcriptomics.

Thoracic aortic aneurysm is a life-threatening condition caused by weakening of the thoracic aorta wall, often developing silently until dissection or rupture occurs. Despite substantial efforts in the past decade, there have been no significant therapeutic advances to prevent or clinically manage diverse forms of thoracic aortic aneurysm and dissection with the only effective treatment being surgical repair. There is an urgent need to understand intra- and inter-aneurysmal heterogeneity underlying thoracic aortic aneurysm and dissection pathogenesis. The human aortic wall consists of many cell types and exhibits significant regional heterogeneity. High-throughput single-cell RNA sequencing has emerged as the principal tool to reveal the complexity in human tissues and clinical specimens. Recent single-cell RNA sequencing studies of different aortic cell populations both in vivo and in vitro began to dissect this complexity and have provided valuable information. In this review, we summarize these findings and discuss the potential applications of single-cell transcriptomics and related high-content technologies in human thoracic aortic aneurysm and dissection research, as well as the challenges associated with it.

Disintegrin and Metalloproteinases (ADAMs [A Disintegrin and Metalloproteinase] and ADAMTSs [ADAMs With a Thrombospondin Motif]) in Aortic Aneurysm.

Aortic aneurysm is a complex pathology that can be lethal if not detected in time. Although several molecular mechanisms and pathways have been identified to be involved in aortic aneurysm development and growth, the current lack of an effective pharmacological treatment highlights the need for a more thorough understanding of the factors that regulate the remodeling of the aortic wall in response to triggers that lead to aneurysm formation. This task is further complicated by the regional heterogeneity of the aorta and that thoracic and abdominal aortic aneurysm are distinct pathologies with different risk factors and distinct course of progression. ADAMs (a disintegrin and metalloproteinases) and ADAMTS (ADAMs with a thrombospondin motif) are proteinases that share similarities with other proteinases but possess unique and diverse properties that place them in a category of their own. In this review, we discuss what is known on how ADAMs and ADAMTSs are altered in abdominal aortic aneurysm and thoracic aortic aneurysm in patients, in different animal models, and their role in regulating the function of different vascular and inflammatory cell types. A full understanding of the role of ADAMs and ADAMTSs in aortic aneurysm will help reveal a more complete understanding of the underlying mechanism driving aneurysm formation, which will help towards developing an effective treatment in preventing or limiting the growth of aortic aneurysm.

Aging Alters the Aortic Proteome in Health and Thoracic Aortic Aneurysm.

BACKGROUND: Aging enhances most chronic diseases but its impact on human aortic tissue in health and in thoracic aortic aneurysms (TAA) remains unclear. METHODS: We employed a human aortic biorepository of healthy specimens (n=17) and those that underwent surgical repair for TAA (n=20). First, we performed proteomics comparing aortas of healthy donors to aneurysmal specimens, in young (ie, <60 years of age) and old (ie, ≥60 years of age) subjects. Second, we measured proteins, via immunoblotting, involved in mitophagy (ie, Parkin) and also mitochondrial-induced inflammatory pathways, specifically TLR (toll-like receptor) 9, STING (stimulator of interferon genes), and IFN (interferon)-ß. RESULTS: Proteomics revealed that aging transformed the aorta both quantitatively and qualitatively from health to TAA. Whereas young aortas exhibited an enrichment of immunologic processes, older aortas exhibited an enrichment of metabolic processes. Immunoblotting revealed that the expression of Parkin directly correlated to subject age in health but inversely to subject age in TAA. In TAA, but not in health, phosphorylation of STING and the expression of IFN-ß was impacted by aging regardless of whether subjects had bicuspid or tricuspid valves. In subjects with bicuspid valves and TAAs, TLR9 expression positively correlated with subject age. Interestingly, whereas phosphorylation of STING was inversely correlated with subject age, IFN-ß positively correlated with subject age. CONCLUSIONS: Aging transforms the human aortic proteome from health to TAA, leading to a differential regulation of biological processes. Our results suggest that the development of therapies to mitigate vascular diseases including TAA may need to be modified depending on subject age.

Second Heart Field-Derived Cells Contribute to Angiotensin II-Mediated Ascending Aortopathies.

BACKGROUND: The ascending aorta is a common location for aneurysm and dissection. This aortic region is populated by a mosaic of medial and adventitial cells that are embryonically derived from either the second heart field (SHF) or the cardiac neural crest. SHF-derived cells populate areas that coincide with the spatial specificity of thoracic aortopathies. The purpose of this study was to determine whether and how SHF-derived cells contribute to ascending aortopathies. METHODS: Ascending aortic pathologies were examined in patients with sporadic thoracic aortopathies and angiotensin II (AngII)-infused mice. Ascending aortas without overt pathology from AngII-infused mice were subjected to mass spectrometry-assisted proteomics and molecular features of SHF-derived cells were determined by single-cell transcriptomic analyses. Genetic deletion of either Lrp1 (low-density lipoprotein receptor-related protein 1) or Tgfbr2 (transforming growth factor-ß receptor type 2) in SHF-derived cells was conducted to examine the effect of SHF-derived cells on vascular integrity. RESULTS: Pathologies in human ascending aortic aneurysmal tissues were predominant in outer medial layers and adventitia. This gradient was mimicked in mouse aortas after AngII infusion that was coincident with the distribution of SHF-derived cells. Proteomics indicated that brief AngII infusion before overt pathology occurred evoked downregulation of smooth muscle cell proteins and differential expression of extracellular matrix proteins, including several LRP1 ligands. LRP1 deletion in SHF-derived cells augmented AngII-induced ascending aortic aneurysm and rupture. Single-cell transcriptomic analysis revealed that brief AngII infusion decreased Lrp1 and Tgfbr2 mRNA abundance in SHF-derived cells and induced a unique fibroblast population with low abundance of Tgfbr2 mRNA. SHF-specific Tgfbr2 deletion led to embryonic lethality at E12.5 with dilatation of the outflow tract and retroperitoneal hemorrhage. Integration of proteomic and single-cell transcriptomics results identified PAI1 (plasminogen activator inhibitor 1) as the most increased protein in SHF-derived smooth muscle cells and fibroblasts during AngII infusion. Immunostaining revealed a transmural gradient of PAI1 in both ascending aortas of AngII-infused mice and human ascending aneurysmal aortas that mimicked the gradient of medial and adventitial pathologies. CONCLUSIONS: SHF-derived cells exert a critical role in maintaining vascular integrity through LRP1 and transforming growth factor-ß signaling associated with increases of aortic PAI1.