Inhibition of heme oxygenase 1 alleviates thoracic aortic aneurysm via restoration of extracellular matrix.

BACKGROUND: Thoracic aortic aneurysm (TAA) is a silent but life-threatening cardiovascular disease. Heme oxygenase 1 (HO-1) plays an important role in the cardiovascular diseases but is poorly understood in TAA. This study aims at investigating the role of HO-1 in TAA. METHODS: Single-cell RNA sequencing, Western blot and histological assay were performed to identify specific cellular expression of HO-1 in both human and ß-aminopropionitrile (BAPN)-induced mice TAA. Zinc protoporphyrin (ZnPP), a pharmacological inhibitor of HO-1, was used to investigate whether inhibition of HO-1 could attenuate BAPN-induced TAA in rodent model. Histological assay, Western blot assay, and mRNA sequencing were further performed to explore the underlying mechanisms. RESULTS: Single-cell transcriptomic analyses of 113,800 thoracic aortic cells identified an increase of HO-1(+) macrophage in aneurysmal thoracic aorta from BAPN-induced TAA mice and TAA patients. Histological assay verified HO-1 overexpression in clinical TAA specimens, which was co-localized with CD68(+) macrophage. HO-1(+) macrophage was closely associated with pro-inflammatory response and immune activation. Inhibition of HO-1 through ZnPP significantly alleviated BAPN-induced TAA in mice and restored extracellular matrix (ECM) in vivo. Further experiments showed that ZnPP treatment suppressed the expression of matrix metalloproteinases (MMPs) in aneurysmal thoracic aortic tissues from BAPN-induced TAA mice, including MMP2 and MMP9. Macrophages from myeloid specific HO-1 knockout mice displayed weakened pro-inflammatory activity and ECM degradation capability. CONCLUSION: HO-1(+) macrophage subgroup is a typical hallmark of TAA. Inhibition of HO-1 through ZnPP alleviates BAPN-induced TAA in mice, which might work through restoration of ECM via suppressing MMP2 and MMP9 expression.

Single-cell transcriptome analysis identifies Versican(+) myofibroblast as a hallmark for thoracic aortic aneurysm marked by activation of PI3K-AKT signaling pathway.

BACKGROUND: Thoracic aortic aneurysm (TAA) is a silent but dangerous cardiovascular disease. Understanding molecular mechanisms of TAA on single-cell level might provide new strategies for preventing and treating TAA. METHODS: Single-cell RNA sequencing was performed on control and aneurysmal thoracic aorta to find out specific cell clusters and cell types. Western blot and histological staining were used to verify the findings of single-cell transcriptome analysis. Characteristics of Versican (VCAN) overexpressed myofibroblast was evaluated through bioinformatic methods and experimental validation. RESULTS: A total of 3 control and 8 TAA specimens were used for single-cell transcriptome analysis including 48,128 thoracic aortic cells. Among these cells, we found out a specific cell cluster containing both hallmarks of smooth muscle cell (SMC) and fibroblast. Thus, we defined these cells as myofibroblast. Further single-cell transcriptome analysis identified VCAN as a cellular marker of myofibroblast. Western blot and histological staining revealed that VCAN(+) myofibroblast was significantly increased in TAA specimens compared with control individuals. Differential analysis, functional, pathway enrichment analysis and cell-cell communication analysis demonstrated that VCAN(+) myofibroblast was closely associated with previous reported TAA associated pathological process including SMC proliferation, SMC migration and extracellular matrix (ECM) disruption. Pathway analysis found out significant activation of PI3K-AKT signaling pathway within VCAN(+) myofibroblast, which was further confirmed by experimental validation. CONCLUSIONS: Single-cell RNA sequencing identified VCAN(+) myofibroblast as a typical cellular hallmark of TAA. These cells might participate in the pathogenesis of TAA through activation of PI3K-AKT signaling pathway to link SMC proliferation, SMC migration and ECM disruption.

Macrophage in Sporadic Thoracic Aortic Aneurysm and Dissection: Potential Therapeutic and Preventing Target.

Thoracic aortic aneurysm and dissection (TAAD) is a life-threatening cardiovascular disorder lacking effective clinical pharmacological therapies. The underlying molecular mechanisms of TAAD still remain elusive with participation of versatile cell types and components including endothelial cells (ECs), smooth muscle cells (SMCs), fibroblasts, immune cells, and the extracellular matrix (ECM). The main pathological features of TAAD include SMC dysfunction, phenotypic switching, and ECM degradation, which is closely associated with inflammation and immune cell infiltration. Among various types of immune cells, macrophages are a distinct participator in the formation and progression of TAAD. In this review, we first highlight the important role of inflammation and immune cell infiltration in TAAD. Furthermore, we discuss the role of macrophages in TAAD from the aspects of macrophage origination, classification, and functions. On the basis of experimental and clinical studies, we summarize key regulators of macrophages in TAAD. Finally, we review how targeting macrophages can reduce TAAD in murine models. A better understanding of the molecular and cellular mechanisms of TAAD may provide novel insights into preventing and treating the condition.

Impact of body mass index on perioperative mortality of acute stanford type A aortic dissection: a systematic review and meta-analysis.

BACKGROUND: Obesity may increase perioperative mortality of acute Stanford type A aortic dissection (ATAAD). However, the available evidence was limited. This study aimed to systematically review published literatures about body mass index (BMI) and perioperative mortality of ATAAD. METHODS: Electronic literature search was conducted in PubMed, Medline, Embase and Cochrane Library databases. All observational studies that investigated BMI and perioperative mortality of ATAAD were included. Pooled odds ratio (OR) and 95% confidence interval (CI) were calculated using a random-effects model. Meta-regression analysis was performed to assess the effects of different clinical variables on BMI and perioperative mortality of ATAAD. Sensitivity analysis was performed to determine the sources of heterogeneity. Egger's linear regression method and funnel plot were used to determine the publication bias. RESULTS: A total of 12 studies with 5,522 patients were eligible and included in this meta-analysis. Pooled analysis showed that perioperative mortality of ATAAD increased by 22% for each 1 kg/m2 increase in BMI (OR = 1.22, 95% CI: 1.10-1.35). Univariable meta-regression analysis indicated that age and female gender significantly modified the association between BMI and perioperative mortality of ATAAD in a positive manner (meta-regression on age: coefficient = 0.04, P = 0.04; meta-regression on female gender: coefficient = 0.02, P = 0.03). Neither significant heterogeneity nor publication bias were found among included studies. CONCLUSIONS: BMI is closely associated with perioperative mortality of ATAAD. Optimal perioperative management needs to be further explored and individualized for obese patient with ATAAD, especially in elderly and female populations. TRIAL REGISTRATION: PROSPERO (CRD42022358619). BMI and perioperative mortality of ATAAD.

Oxidative stress drives vascular smooth muscle cell damage in acute Stanford type A aortic dissection through HIF-1α/HO-1 mediated ferroptosis.

Background: Acute Stanford type A aortic dissection (ATAAD) is characterized by intimal tearing and false lumen formation containing large amounts of erythrocytes with heme. Heme oxygenase 1 (HO-1) is the key enzyme to degrade heme for iron accumulation and further ferroptosis. The current study aimed at investigating the role of HO-1 in the dissection progression of ATAAD. Methods: Bioinformatic analyses and experimental validation were performed to reveal ferroptosis and HO-1 expression in ATAAD. Human aortic vascular smooth muscle cell (HA-VSMC) was used to explore underlying molecular mechanisms and the role of HO-1 overexpression in ATAAD. Results: Ferroptosis was identified as a critical manner of regulated cell death in ATAAD. HO-1 was screened as a key signature of ferroptosis in ATAAD, which was closely associated with oxidative stress. Single cell/nucleus transcriptomic analysis and histological staining revealed that HO-1 and HIF-1α were upregulated in vascular smooth muscle cell (VSMC) of ATAAD. Further in vitro experiments showed that H2O2-induced oxidative stress increased VSMC ferroptosis with the overexpression of HO-1, which could be suppressed by HIF-1α inhibitor PX-478. HIF-1α could transcriptionally regulate the expression of HO-1 through binding to its promoter region. Pharmacological inhibition of HO-1 by zinc protoporphyrin (ZnPP) did not reduce H2O2-induced HA-VSMC damage without heme co-incubation. However, H2O2-induced HA-VSMC damage was worsened when heme was added into the medium, and ZnPP could reduce HA-VSMC damage in this condition. Conclusion: HO-1 is a key signature of VSMC ferroptosis in ATAAD. HIF-1α/HO-1 mediated ferroptosis might participate in oxidative stress induced VSMC damage.