AIM2 Inflammasome Activation Contributes to Aortic Dissection in a Sporadic Aortic Disease Mouse Model

BACKGROUND

The absent in melanoma 2 (AIM2) inflammasome induces pyroptosis, tissue inflammation, and extracellular matrix destruction. We tested the hypothesis that the AIM2 inflammasome contributes to aortic aneurysm and dissection (AAD) development by promoting pyroptosis in smooth muscle cells (SMCs).

METHODS

We examined AIM2 expression in aortic tissues from patients with ascending thoracic aortic aneurysm (ATAA) and aortic dissection (ATAD) and from organ donor controls. AIM2's role in AAD development was evaluated in AIM2-deficient mice in a sporadic AAD model induced by challenging mice with a high-fat diet and angiotensin II infusion. The direct effects of dsDNA on SMC death in vitro were studied.

RESULTS

Western blot analyses showed that AIM2 was increased in ATAD compared to ATAA and control tissue. Immunofluorescence demonstrated increased AIM2 in SMCs and macrophages in the aortic media and adventitia of dissected tissue. Increased AIM2 abundance was associated with increased cleavage of caspase-1 and cleavage of gasdermin-D, indicating activation of pyroptosis. In a mouse model of sporadic AAD induced by high-fat diet and angiotensin II infusion, AIM2-deficient mice showed significant reduction in aortic dissection, but not aneurysm formation in all aortic segments, versus wild-type mice. Finally, treating cultured human aortic SMCs with double-stranded DNA induced AIM2 expression, caspase-1 cleavage, and gasdermin-D cleavage; these effects were reduced by silencing AIM2 and caspase-1 genes, suggesting involvement of the AIM2 inflammasome in cytosolic DNA-induced activation of SMC pyroptosis.

CONCLUSIONS

Activation of the AIM2 inflammasome cascade contributes to aortic degeneration and dissection, in part, by activating pyroptosis.

Ciprofloxacin accelerates aortic enlargement and promotes dissection and rupture in Marfan mice

OBJECTIVE

Aortic aneurysm and dissection are major life-threatening complications of Marfan syndrome. Avoiding factors that promote aortic damage is critical in managing the care of these patients. Findings from clinical and animal studies raise concerns regarding fluoroquinolone use in patients at risk for aortic aneurysm and dissection. Therefore, we examined the effects of ciprofloxacin on aortic aneurysm and dissection development in Marfan mice.

METHODS

Eight-week-old Marfan mice (Fbn1C1041G/+) were given ciprofloxacin (100 mg/kg/d; n = 51) or vehicle (n = 59) for 4 weeks. Mice were monitored for 16 weeks. Aortic diameters were measured by using ultrasonography, and aortic structure was examined by using histopathologic and immunostaining analyses.

RESULTS

Vehicle-treated Fbn1C1041G/+ mice showed progressive aortic enlargement, with aortic rupture occurring in 5% of these mice. Compared with vehicle-treated Fbn1C1041G/+ mice, ciprofloxacin-treated Fbn1C1041G/+ mice showed accelerated aortic enlargement (P = .01) and increased incidences of aortic dissection (25% vs 47%, P = .03) and rupture (5% vs 25%, P = .005). Furthermore, ciprofloxacin-treated Fbn1C1041G/+ mice had higher levels of elastic fiber fragmentation, matrix metalloproteinase expression, and apoptosis than did vehicle-treated Fbn1C1041G/+ mice.

CONCLUSIONS

Ciprofloxacin accelerates aortic root enlargement and increases the incidence of aortic dissection and rupture in Marfan mice, partially by suppressing lysyl oxidase expression and further compromising the inherited defect in aortic elastic fibers. Our findings substantiate that ciprofloxacin should be avoided in patients with Marfan syndrome.

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 low-density lipoprotein receptor-related protein 1 (Lrp1) or transforming growth factor-β receptor 2 (Tgfbr2) in SHF-derived cells was conducted to examine the impact 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 following AngII infusion that was coincident with the distribution of SHF-derived cells. Proteomics indicated that brief AngII infusion, prior to overt pathology, evoked downregulation of SMC 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 plasminogen activator inhibitor 1 (PAI1) as the most increased protein in SHF-derived SMCs 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 TGF-β signaling associated with increases of aortic PAI1.

Racial and Ethnic Disparities in Abdominal Aortic Aneurysm Evaluation and Treatment Rates in Texas

INTRODUCTION

Screening identifies intact abdominal aortic aneurysm (iAAA) before progression to ruptured AAA (rAAA). However, screening efforts have been limited by low overall diagnostic yield and by unequal screening among minority populations. The goal was to identify equitable AAA screening strategies for both majority and minority populations.

METHODS

We performed epidemiological and geospatial analyses of inpatient and outpatient procedures for iAAA or rAAA at Texas hospitals from 2006 through 2014 at all non-federal hospitals and clinics in Texas. Data were aggregated by area (metropolitan statistical area or rural region), then supplemented by six additional data sources to estimate AAA repair incidence rates, rates of AAA-related clinic and ultrasonography visits, distance to providers, and location and number of unrecognized AAAs.

RESULTS

The majority of AAA repairs occurred among 65-84 year-old men in large metropolitan areas categorized as White. Area procedure rates for rAAA and iAAA were strongly correlated (R²=0.47). Two other variables-the proportions of persons categorized as White and persons aged ≥65 years in a region-identified subgroups within the majority population that were at high risk for iAAA (R²=0.46). Lower rates of clinic visits and AAA ultrasonograms were seen among persons categorized as Black. The several areas with disproportionately-higher rAAA:iAAA ratios were found, mainly affecting persons categorized as Black.

CONCLUSIONS

Multiple focused AAA screening strategies may be needed to address disproportionately-lower AAA identification among persons categorized as Black.

Single-Cell Analysis of Aneurysmal Aortic Tissue in Patients with Marfan Syndrome Reveals Dysfunctional TGF-β Signaling

The molecular and cellular processes leading to aortic aneurysm development in Marfan syndrome (MFS) remain poorly understood. In this study, we examined the changes of aortic cell populations and gene expression in MFS by performing single-cell RNA sequencing (scRNA seq) on ascending aortic aneurysm tissues from patients with MFS (n = 3) and age-matched non-aneurysmal control tissues from cardiac donors and recipients (n = 4). The expression of key molecules was confirmed by immunostaining. We detected diverse populations of smooth muscle cells (SMCs), fibroblasts, and endothelial cells (ECs) in the aortic wall. Aortic tissues from MFS showed alterations of cell populations with increased de-differentiated proliferative SMCs compared to controls. Furthermore, there was a downregulation of MYOCD and MYH11 in SMCs, and an upregulation of COL1A1/2 in fibroblasts in MFS samples compared to controls. We also examined TGF-β signaling, an important pathway in aortic homeostasis. We found that TGFB1 was significantly upregulated in two fibroblast clusters in MFS tissues. However, TGF-β receptor genes (predominantly TGFBR2) and SMAD genes were downregulated in SMCs, fibroblasts, and ECs in MFS, indicating impairment in TGF-β signaling. In conclusion, despite upregulation of TGFB1, the rest of the canonical TGF-β pathway and mature SMCs were consistently downregulated in MFS, indicating a potential compromise of TGF-β signaling and lack of stimulus for SMC differentiation.

Staged Repair of Extensive Aneurysms of the Thoracic Aorta by Using the Elephant Trunk Technique

BACKGROUND

Staged open repair of extensive aortic aneurysm by using the elephant trunk (ET) technique has facilitated the treatment of aortic aneurysms that affect the entire thoracic aorta. We describe our nearly 3-decade experience with classic ET repairs.

METHODS

From 1990 through 2021, we performed 363 stage-1 ET repairs to replace the transverse aortic arch in patients with a median age of 65 years [interquartile range: 56-71]. Fifty-six patients (15.4%) presented with acute symptoms, and 182 (50.1%) underwent redo sternotomy. After a median interval of 3.2 months [IQR: 2.0-7.3], 203 (55.9%) patients underwent stage-2 ET completion; few (n=16; 7.9%) had acute symptoms. Stage-2 repairs comprised 162 (80.6%) extent I or II thoracoabdominal aortic replacements. We examined postoperative outcomes including operative mortality, adverse event (a composite end point), survival, and repair failure.

RESULTS

Operative mortality was 12.4% (45/363) after stage-1 and 10.3% (21/203) after stage-2. The rates of adverse event were 18.5% (67/363) for stage-1 and 18.4% (38/203) for stage-2. Acute symptoms independently predicted operative mortality and adverse event for both stage-1 and stage-2 repairs; additional predictors for stage-2 repairs were older age and extent II repair. Survival was significantly worse for patients who did not receive their stage-2 completion repair than for those who did (p <0.001).

CONCLUSIONS

Treating extensive aortic aneurysms by using the ET technique for staged repair is associated with substantial morbidity and mortality. Patients who present with acute symptoms are at greater risk of operative mortality and adverse event. Diligent surveillance is needed between stages.

Molecular and Cellular Dynamics of Aortic Aneurysms Revealed by Single-Cell Transcriptomics

The aorta is highly heterogeneous, containing many different types of cells that perform sophisticated functions to maintain aortic homeostasis. Recently, single-cell RNA sequencing studies have provided substantial new insight into the heterogeneity of vascular cell types, the comprehensive molecular features of each cell type, and the phenotypic interrelationship between these cell populations. This new information has significantly improved our understanding of aortic biology and aneurysms at the molecular and cellular level. Here, we summarize these findings, with a focus on what single-cell RNA sequencing analysis has revealed about cellular heterogeneity, cellular transitions, communications among cell populations, and critical transcription factors in the vascular wall. We also review the information learned from single-cell RNA sequencing that has contributed to our understanding of the pathogenesis of vascular disease, such as the identification of cell types in which aneurysm-related genes and genetic variants function. Finally, we discuss the challenges and future directions of single-cell RNA sequencing applications in studies of aortic biology and diseases.

Open Repair of Acute Type A Intramural Hematoma in 3 Patients

Acute aortic syndrome encompasses classic aortic dissection and less common aortic phenomena, including intramural hematoma (IMH), a hemorrhage within the aortic media that occurs without a discrete intimal tear. We reviewed our experience with treating acute type A IMH to better understand this acute aortic syndrome. A review of our clinical database identified 1,902 proximal aortic repairs that were performed from January 2006 through December 2018; of these, 266 were for acute aortic syndrome, including 3 (1.1%) for acute type A IMH. Operative technique varied considerably. All IMH repairs involved hemiarch or total arch replacement. In all 3 patients, the IMH extended distally into the descending thoracic aorta. There were no operative deaths or major adverse events (stroke, paraplegia, paraparesis, or renal failure necessitating dialysis) that persisted to hospital discharge. Length of hospitalization ranged from 5 to 20 days. All 3 patients were alive at follow-up (range, 2-6 yr) and needed no aortic reintervention after their index or staged repairs. In our experience, repair of acute type A IMH was infrequent and could be either simple or complex. Despite our limited experience with this disease, we found that it can be repaired successfully in urgent and emergency cases. Following treatment guidelines for aortic dissection appears to be a reasonable strategy for treating IMH.

New Technologies With Increased Precision Improve Understanding of Endothelial Cell Heterogeneity in Cardiovascular Health and Disease

Endothelial cells (ECs) are vital for blood vessel integrity and have roles in maintaining normal vascular function, healing after injury, and vascular dysfunction. Extensive phenotypic heterogeneity has been observed among ECs of different types of blood vessels in the normal and diseased vascular wall. Although ECs with different phenotypes can share common functions, each has unique features that may dictate a fine-tuned role in vascular health and disease. Recent studies performed with single-cell technology have generated powerful information that has significantly improved our understanding of EC biology. Here, we summarize a variety of EC types, states, and phenotypes recently identified by using new, increasingly precise techniques in transcriptome analysis.

Effect of sarcopenia on survival and spinal cord deficit outcomes after thoracoabdominal aortic aneurysm repair in patients 60 years of age and older

OBJECTIVE

Sarcopenia (core muscle loss) has been used as a surrogate marker of frailty. We investigated whether sarcopenia would adversely affect survival after thoracoabdominal aortic aneurysm repair.

METHODS

We retrospectively reviewed prospectively collected data from patients aged 60 years or older who underwent thoracoabdominal aortic aneurysm repairs from 2006 to 2016. Imaging was reviewed by 2 radiologists blinded to clinical outcomes. The total psoas index was derived from total psoas muscle cross-sectional area (cm²) at the mid-L4 level, normalized for height (m²). Patients were divided by sex-specific total psoas index values into sarcopenia (lower third) and nonsarcopenia (upper two-thirds) groups. Multivariable modeling identified operative mortality and spinal cord injury predictors. Unadjusted and adjusted survival curves were analyzed.

RESULTS

Of 392 patients identified, those with sarcopenia (n = 131) were older than nonsarcopenic patients (n = 261) (70.0 years vs 68.0 years; P = .02) and more frequently presented with aortic rupture or required urgent/emergency operations. Operative mortality was comparable (sarcopenia 13.7% vs nonsarcopenia 10.0%; P = .3); sarcopenia was not associated with operative mortality in the multivariable model (odds ratio, 1.40; 95% confidence interval, 0.73-2.77; P = .3). Sarcopenic patients experienced more frequent delayed (13.0% vs 4.6%; P = .005) and persistent (10.7% vs 3.4%; P = .008) paraplegia. Sarcopenia independently predicted delayed paraplegia (odds ratio, 3.17; 95% confidence interval, 1.42-7.08; P = .005) and persistent paraplegia (odds ratio, 3.29; 95% confidence interval, 1.33-8.13; P = .01) in the multivariable model. Adjusted for preoperative/operative covariates, midterm survival was similar for sarcopenic and nonsarcopenic patients (P = .3).

CONCLUSIONS

Sarcopenia did not influence early mortality or midterm survival after thoracoabdominal aortic aneurysm repair but was associated with greater risk for delayed and persistent paraplegia.

Sex Differences in Ascending Aortic and Arch Surgery: A Propensity-matched Comparison of 1153 Pairs

BACKGROUND

We investigated the relationship of sex with clinical outcomes after proximal aortic (ascending and arch) operations, and whether sex-specific preoperative factors are associated with mortality.

METHODS

Of 3745 patients who underwent elective, urgent, and emergency proximal aortic operations over a 20-year period, 1153 pairs of men and women were propensity-matched, and their early and long-term outcomes were compared. Kaplan-Meier survival analysis was used to estimate late survival.

RESULTS

Women and men had similar operative mortality (9.1% vs 8.8%, P=0.8), stroke (5.7% vs 5.6%, P=0.9), and renal failure rates (7.0% vs 6.6%, P=0.7). Thirty-day mortality was 7.5% versus 5.6% (P=0.06), respectively. Results were less favorable for women than for men regarding respiratory failure (34.3% vs 29.2%, P=0.008) and intensive care unit length of stay (9.11±11.9 vs 7.87±12.48 days; P=0.023). Long-term survival was not significantly different between women and men: 66.3% (95%CI 62.8-69.5) versus 67.1% (95%CI 63.6-70.4) at 5 years, and 45.9% (95%CI 41.76-50.0) versus 46.2% (95%CI 41.7-50.6) at 10 years (P=0.4). Preoperative factors including diabetes, prior stroke, prior renal insufficiency, and peripheral vascular disease were associated with operative mortality in men, whereas chronic obstructive pulmonary disease was the main risk factor in women.

CONCLUSIONS

No differences were seen between the sexes in life-changing adverse outcomes after ascending aortic and arch procedures, although specific preoperative variables were associated with specific adverse events. Recognizing differences in preoperative risk factors for mortality between the sexes may facilitate targeted preoperative assessment, preparation, and counseling.

Early Detection of Aortic Degeneration in a Mouse Model of Sporadic Aortic Aneurysm and Dissection Using Nanoparticle Contrast-Enhanced Computed Tomography

[Figure: see text].

Monosomy X in Female Mice Influences the Regional Formation and Augments the Severity of Angiotensin II-Induced Aortopathies

OBJECTIVE

Turner syndrome women (monosomy X) have high risk of aortopathies consistent with a role for sex chromosomes in disease development. We demonstrated that sex chromosomes influence regional development of Ang II (angiotensin II)-induced aortopathies in mice. In this study, we determined if the number of X chromosomes regulates regional development of Ang II-induced aortopathies. Approach and Results: We used females with varying numbers of X chromosomes (XX female mice [XXF] or XO female mice [XOF]) on an C57BL/6J (ascending aortopathies) or low-density lipoprotein receptor deficient (Ldlr-/-) background (descending and abdominal aortopathies) compared with XY males (XYM). To induce aortopathies, mice were infused with Ang II. XOF (C57BL/6J) exhibited larger percent increases in ascending aortic lumen diameters than Ang II-infused XXF or XYM. Ang II-infused XOF (Ldlr-/-) exhibited similar incidences of thoracic (XOF, 50%; XYM, 71%) and abdominal aortopathies (XOF, 83%; XYM, 71%) as XYM, which were greater than XXF (XXF, 0%). Abdominal aortic lumen diameters and maximal external diameters were similar between XOF and XYM but greater than XXF, and these effects persisted with extended Ang II infusions. Larger aortic lumen diameters, abdominal aortopathy incidence (XXF, 20%; XOF, 75%), and maximal aneurysm diameters (XXF, 1.02±0.17; XOF, 1.96±0.32 mm; P=0.027) persisted in ovariectomized Ang II-infused XOF mice. Data from RNA-seq demonstrated that X chromosome genes that escape X-inactivation (histone lysine demethylases Kdm5c and Kdm6a) exhibited lower mRNA abundance in aortas of XOF than XXF (P=0.033 and 0.024, respectively). Conversely, DNA methylation was higher in aortas of XOF than XXF (P=0.038).

CONCLUSIONS

The absence of a second X chromosome promotes diffuse Ang II-induced aortopathies in females.

Cholesterol-Induced Phenotypic Modulation of Smooth Muscle Cells to Macrophage/Fibroblast-like Cells Is Driven by an Unfolded Protein Response

OBJECTIVE

Vascular smooth muscle cells (SMCs) dedifferentiate and initiate expression of macrophage markers with cholesterol exposure. This phenotypic switching is dependent on the transcription factor Klf4 (Krüppel-like factor 4). We investigated the molecular pathway by which cholesterol induces SMC phenotypic switching. Approach and Results: With exposure to free cholesterol, SMCs decrease expression of contractile markers, activate Klf4, and upregulate a subset of macrophage and fibroblast markers characteristic of modulated SMCs that appear with atherosclerotic plaque formation. These phenotypic changes are associated with activation of all 3 pathways of the endoplasmic reticulum unfolded protein response (UPR), Perk (protein kinase RNA-like endoplasmic reticulum kinase), Ire (inositol-requiring enzyme) 1α, and Atf (activating transcription factor) 6. Blocking the movement of cholesterol from the plasma membrane to the endoplasmic reticulum prevents free cholesterol-induced UPR, Klf4 activation, and upregulation of the majority of macrophage and fibroblast markers. Cholesterol-induced phenotypic switching is also prevented by global UPR inhibition or specific inhibition of Perk signaling. Exposure to chemical UPR inducers, tunicamycin and thapsigargin, is sufficient to induce these same phenotypic transitions. Finally, analysis of published single-cell RNA sequencing data during atherosclerotic plaque formation in hyperlipidemic mice provides preliminary in vivo evidence of a role of UPR activation in modulated SMCs.

CONCLUSIONS

Our data demonstrate that UPR is necessary and sufficient to drive phenotypic switching of SMCs to cells that resemble modulated SMCs found in atherosclerotic plaques. Preventing a UPR in hyperlipidemic mice diminishes atherosclerotic burden, and our data suggest that preventing SMC transition to dedifferentiated cells expressing macrophage and fibroblast markers contributes to this decreased plaque burden.

Propensity score analysis in patients with and without previous isolated coronary artery bypass grafting who require proximal aortic and arch surgery

OBJECTIVE

The risk posed by previous isolated coronary artery bypass grafting (CABG) in patients who require proximal aortic or aortic arch surgery is unclear. We compared outcomes of ascending aortic and arch procedures in patients with and without previous CABG.

METHODS

Using propensity scores, we created 2 matched groups of patients who underwent proximal aortic surgery, including total arch repairs, at our institution: 126 patients who underwent isolated CABG before the index operation and 126 without previous CABG. Forty-four percent of aortic operations were emergency procedures. Eighty-six patients had a patent previous left internal mammary graft. We compared outcomes between the 2 groups and calculated Kaplan-Meier survival curves.

RESULTS

The following outcomes were recorded for the patients with previous isolated CABG versus no CABG: operative mortality, 15.9% versus 11.1% (P = .3); 30-day mortality, 13.5% versus 7.1% (P = .1); persistent stroke, 6.3% versus 4.8% (P = .6); and renal failure necessitating hemodialysis at discharge, 7.9% versus 4.0% (P = .2). Previous CABG did not independently predict any adverse outcome, even though patients who underwent previous CABG more frequently needed intra-aortic balloon support (P < .01). The P value for the overall intergroup difference in long-term survival was .06.

CONCLUSIONS

This is one of the largest studies yet reported to examine the impact of previous isolated CABG on proximal aortic or arch surgery outcomes. Although these results may be specific to aortic centers of excellence, in this complicated patient cohort, previous isolated CABG did not independently predict any adverse outcome. These results could serve as a benchmark for assessing future endovascular therapies.

A 23-year experience with the reversed elephant trunk technique for staged repair of extensive thoracic aortic aneurysm

OBJECTIVE

The reversed elephant trunk technique permits staged repair of extensive thoracic aortic aneurysm in patients whose distal (ie, descending thoracic and thoracoabdominal) aorta is symptomatic or disproportionately large compared with their proximal aorta (ie, ascending aorta and transverse aortic arch). We present our 23-year experience with the reversed elephant trunk approach.

METHODS

Between 1994 and 2017, 94 patients (median age 62 [46-69] years) underwent stage 1 reversed elephant trunk repair of the distal aorta. Fifty-three patients (56%) had aortic dissection, and 31 patients (33%) had heritable thoracic aortic disease. Eighty-eight operations (94%) were Crawford extent I or II thoracoabdominal aortic repairs. Twenty-seven patients (29%) underwent subsequent stage 2 repair of the proximal aorta; 14 patients (52%) required redo median sternotomy. The median time between the stage 1 and 2 operations was 18.8 (4.8-69.3) months.

RESULTS

The operative mortality was 10% (9/94) for stage 1 repairs and 4% (1/27) for stage 2 repairs; 1 patient with heritable thoracic aortic disease died after stage 1 repair (1/31, 3%), and 1 patient died after stage 2 repair (1/13, 8%). Two patients (2%) had ruptures after stage 1 repair; 1 resulted in death, and 1 precipitated emergency stage 2 repair. In total, 36 patients (38%) who survived stage 1 repair died before stage 2 reversed elephant trunk completion repair could be performed.

CONCLUSIONS

Managing extensive aortic aneurysm with the 2-stage reversed elephant trunk technique yields acceptable short-term outcomes. This technique is useful for the reversed elephant trunk in patients who require distal aortic repair before proximal repair and is particularly effective in patients with heritable thoracic aortic disease. The low number of patients returning for completion repair is concerning. Rigorous surveillance is needed.

Early Gastrointestinal Complications After Open Thoracoabdominal Aortic Aneurysm Repair

BACKGROUND

The present study was done to examine the incidence, predictors, and impact of early gastrointestinal (GI) complications after open thoracoabdominal aortic aneurysm repair.

METHODS

We retrospectively analyzed data from 3587 open thoracoabdominal aortic aneurysm repairs performed at our center from 1986 to 2019. We used univariate analyses and multivariable logistic regression to identify risk factors associated with GI complications, including bleeding, ischemia, obstruction, and acute pancreatitis. Adverse event was defined as operative death or persistent stroke, paraplegia, paraparesis, or renal failure necessitating dialysis.

RESULTS

Gastrointestinal complications developed after 213 repairs (5.9%). Gastrointestinal complications less often developed after extent I repair than after repairs that involved infrarenal abdominal aortic segments (ie, extent II to IV repairs; P = .003). Patients who had GI complications more often underwent endarterectomy, stenting, or bypass of visceral arteries (51.2% vs 42.2%; P = .01). Use of selective visceral perfusion did not differ between groups. Patients who had GI complications had higher rates of operative mortality (34.3% vs 6.6%) and adverse events (44.1% vs 13.2%) and had longer hospitalization (29 vs 11 days; P < .001 for all). Independent predictors of GI complications included incidental splenectomy, rupture, non-extent I repair, older age, and longer aortic cross-clamp time. Short-term, midterm, and long-term survival were poorer for patients who had GI complications (P < .001).

CONCLUSIONS

Although uncommon, early GI complications after open thoracoabdominal aortic aneurysm repair are associated with significant early and late morbidity and mortality. Development of perioperative strategies to mitigate these complications is warranted.

Single-Cell Transcriptome Analysis Reveals Dynamic Cell Populations and Differential Gene Expression Patterns in Control and Aneurysmal Human Aortic Tissue

BACKGROUND

Ascending thoracic aortic aneurysm (ATAA) is caused by the progressive weakening and dilatation of the aortic wall and can lead to aortic dissection, rupture, and other life-threatening complications. To improve our understanding of ATAA pathogenesis, we aimed to comprehensively characterize the cellular composition of the ascending aortic wall and to identify molecular alterations in each cell population of human ATAA tissues.

METHODS

We performed single-cell RNA sequencing analysis of ascending aortic tissues from 11 study participants, including 8 patients with ATAA (4 women and 4 men) and 3 control subjects (2 women and 1 man). Cells extracted from aortic tissue were analyzed and categorized with single-cell RNA sequencing data to perform cluster identification. ATAA-related changes were then examined by comparing the proportions of each cell type and the gene expression profiles between ATAA and control tissues. We also examined which genes may be critical for ATAA by performing the integrative analysis of our single-cell RNA sequencing data with publicly available data from genome-wide association studies.

RESULTS

We identified 11 major cell types in human ascending aortic tissue; the high-resolution reclustering of these cells further divided them into 40 subtypes. Multiple subtypes were observed for smooth muscle cells, macrophages, and T lymphocytes, suggesting that these cells have multiple functional populations in the aortic wall. In general, ATAA tissues had fewer nonimmune cells and more immune cells, especially T lymphocytes, than control tissues did. Differential gene expression data suggested the presence of extensive mitochondrial dysfunction in ATAA tissues. In addition, integrative analysis of our single-cell RNA sequencing data with public genome-wide association study data and promoter capture Hi-C data suggested that the erythroblast transformation-specific related gene(ERG) exerts an important role in maintaining normal aortic wall function.

CONCLUSIONS

Our study provides a comprehensive evaluation of the cellular composition of the ascending aortic wall and reveals how the gene expression landscape is altered in human ATAA tissue. The information from this study makes important contributions to our understanding of ATAA formation and progression.