Ex vivo expansion of regulatory T cells from abdominal aortic aneurysm patients inhibits aneurysm in humanized murine model

Unravelling CD4+ T cell diversity and tissue adaptation of Tregs in abdominal aortic aneurysms through single-cell sequencing

Immune cell infiltration is a significant pathological process in abdominal aortic aneurysms (AAA). T cells, particularly CD4+ T cells, are essential immune cells responsible for substantial infiltration of the aorta. Regulatory T cells (Tregs) in AAA have been identified as tissue-specific; however, the time, location, and mechanism of acquiring the tissue-specific phenotype are still unknown. Using single-cell RNA sequencing (scRNA-seq) on CD4+ T cells from the AAA aorta and spleen, we discovered heterogeneity among CD4+ T cells and identified activated, proliferating and developed aorta Tregs. These Tregs originate in the peripheral tissues and acquire the tissue-specific phenotype in the aorta. The identification of precursors for Tregs in AAA provides new insight into the pathogenesis of AAA.

Overview of multifunctional Tregs in cardiovascular disease: From insights into cellular functions to clinical implications

Regulatory T cells (Tregs) are crucial in regulating T-cell-mediated immune responses. Numerous studies have shown that dysfunction or decreased numbers of Tregs may be involved in inflammatory cardiovascular diseases (CVDs) such as atherosclerosis, hypertension, myocardial infarction, myocarditis, cardiomyopathy, valvular heart diseases, heart failure, and abdominal aortic aneurysm. Tregs can help to ameliorate CVDs by suppressing excessive inflammation through various mechanisms, including inhibition of T cells and B cells, inhibition of macrophage-induced inflammation, inhibition of dendritic cells and foam cell formation, and induction of anti-inflammatory macrophages. Enhancing or restoring the immunosuppressive activity of Tregs may thus serve as a fundamental immunotherapy to treat hypertension and CVDs. However, the precise molecular mechanisms underlying the Tregs-induced protection against hypertension and CVDs remain to be investigated. This review focuses on recent advances in our understanding of Tregs subsets and function in CVDs. In addition, we discuss promising strategies for using Tregs through various pharmacological approaches to treat hypertension and CVDs.

Deciphering Abdominal Aortic Diseases Through T-Cell Clonal Repertoire of Perivascular Adipose Tissue

BACKGROUND

Recent studies suggest that immune-mediated inflammation of perivascular adipose tissue of abdominal aortic aneurysms (AAAs) contributes to disease development and progression. Whether the perivascular adipose tissue of AAA is characterized by a specific adaptive immune signature remains unknown.

METHODS AND RESULTS

To investigate this hypothesis, we sequenced the T-cell receptor β-chain in the perivascular adipose tissue of patients with AAA and compared it with patients with aortic occlusive disease, who share the former anatomical site of the lesion and risk factors but differ in pathogenic mechanisms. Our results demonstrate that patients with AAA have a lower repertoire diversity than those with aortic occlusive disease and significant differences in variable/joining gene segment usage. Furthermore, we identified a set of 7 public T-cell receptor β-chain clonotypes that distinguished AAA and aortic occlusive disease with very high accuracy. We also found that the T-cell receptor β-chain repertoire differentially characterizes small and large AAAs (aortic diameter<55 mm and ≥55 mm, respectively).

CONCLUSIONS

This work supports the hypothesis that T cell-mediated immunity is fundamental in AAA pathogenesis and opens up new clinical perspectives.

Dysfunctional regulatory T cell: May be an obstacle to immunotherapy in cardiovascular diseases

Inflammatory responses are linked to cardiovascular diseases (CVDs) in various forms. Tregs, members of CD4+ T cells, play important roles in regulating immune system and suppressing inflammatory response, thus contributing to maintaining immune homeostasis. However, Tregs exert their powerful suppressive function relying on the stable phenotype and function. The stability of Tregs primarily depends on the FOXP3 (Forkhead box P3) expression and epigenetic regulation. Although Tregs are quite stable under physiological conditions, prolonged exposure to inflammatory cues, Tregs may lose suppressive function and require proinflammatory phenotype, namely plastic Tregs or ex-Tregs. There are extensive researches have established the beneficial role of Tregs in CVDs. Nevertheless, the potential risks of dysfunctional Tregs lack deep research. Anti-inflammatory and immunological modulation have been hotspots in the treatment of CVDs. Tregs are appealing because of their crucial role in resolving inflammation and promoting tissue repair. If alleviating inflammatory response through modulating Tregs could be a new therapeutic strategy for CVDs, the next step to consider is how to prevent the formation of dysfunctional Tregs or reverse detrimental Tregs to normal phenotype.

Regulatory T cells and cardiovascular diseases

ABSTRACT

Inflammation is a major underlying mechanism in the progression of numerous cardiovascular diseases (CVDs). Regulatory T cells (Tregs) are typical immune regulatory cells with recognized immunosuppressive properties. Despite the immunosuppressive properties, researchers have acknowledged the significance of Tregs in maintaining tissue homeostasis and facilitating repair/regeneration. Previous studies unveiled the heterogeneity of Tregs in the heart and aorta, which expanded in CVDs with unique transcriptional phenotypes and reparative/regenerative function. This review briefly summarizes the functional principles of Tregs, also including the synergistic effect of Tregs and other immune cells in CVDs. We discriminate the roles and therapeutic potential of Tregs in CVDs such as atherosclerosis, hypertension, abdominal arterial aneurysm, pulmonary arterial hypertension, Kawasaki disease, myocarditis, myocardial infarction, and heart failure. Tregs not only exert anti-inflammatory effects but also actively promote myocardial regeneration and vascular repair, maintaining the stability of the local microenvironment. Given that the specific mechanism of Tregs functioning in CVDs remains unclear, we reviewed previous clinical and basic studies and the latest findings on the function and mechanism of Tregs in CVDs.

Blood immunological profile of abdominal aortic aneurysm based on autoimmune injury

Abdominal aortic aneurysm (AAA) occupies a large part of aorta aneurysm, and if there's no timely intervention or treatment, the risks of rupture and death would rise sharply. With the depth of research in AAA, more and more evidence showed correlations between AAA and autoimmune injury. Currently, a variety of bioactive peptides and cells have been confirmed to be related with AAA progression. Despite the tremendous progress, more than half researches were sampling from lesion tissues, which would be difficult to obtain. Given that the intrusiveness and convenience, serological test take advantages in initial diagnosis. Here we review blood biomarkers associated with autoimmune injury work in AAA evolution, aiming to make a profile on blood immune substances of AAA and provide a thought for potential clinical practice.

Key ferroptosis-related genes in abdominal aortic aneurysm formation and rupture as determined by combining bioinformatics techniques

Objectives

Abdominal aortic aneurysm (AAA) is a cardiovascular disease with high mortality and pathogenesis closely related to various cell death types, e.g., autophagy, apoptosis and pyroptosis. However, the association between AAA and ferroptosis is unknown.

Methods

GSE57691 and GSE98278 dataset were obtained from the Gene Expression Omnibus database, and a ferroptosis-related gene (FRG) set was downloaded from the FerrDb database. These data were normalized, and ferroptosis-related differentially expressed genes (FDEGs, AAA vs. normal samples) were identified using the limma package in R. FRGs expression was analyzed by Gene Set Expression Analysis (GSEA), and FDEGs were analyzed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes (KEGG) pathway enrichment analyses using the clusterProfiler package in R and ClueGO in Cytoscape. Protein–protein interaction networks were assembled using Cytoscape, and crucial FDEGs were identified using CytoHubba. Critical FDEG transcription factors (TFs) were predicted with iRegulon. FDEGs were verified in GSE98278 set, and key FDEGs in AAA (compared with normal samples) and ruptured AAA (RAAA; compared with AAA samples) were identified. Ferroptosis-related immune cell infiltration and correlations with key genes were analyzed by CIBERSORT. Key FEDGs were reverified in Ang II-induced AAA models of ApoE^–/– and CD57B/6J mice by immunofluorescence assay.

Results

In AAA and normal samples, 40 FDEGs were identified, and the expression of suppressive FRGs was significantly downregulated with GSEA. For FDEGs, the GO terms were response to oxidative stress and cellular response to external stimulus, and the KEGG pathways were the TNF and NOD-like receptor signaling pathways. IL6, ALB, CAV1, PTGS2, NOX4, PRDX6, GPX4, HSPA5, HSPB1, and NCF2 were the most enriched genes in the crucial gene cluster. CEBPG, NFAT5, SOX10, GTF2IRD1, STAT1, and RELA were potential TFs affecting these crucial genes. Ferroptosis-related immune cells involved in AAA formation were CD8+ T, naive CD4+ T, and regulatory T cells (Tregs); M0 and M2 macrophages; and eosinophils. Tregs were also involved in RAAA. GPX4, SLC2A1, and PEBP1 expression was downregulated in both the RAAA and AAA samples. GPX4 and PEBP1 were more important in AAA because they influenced ferroptosis-related immune cell infiltration, and SLC2A1 was more important in RAAA.

Conclusions

This is the first study to show that ferroptosis is crucial to AAA/RAAA formation. The TNF and NOD-like signaling pathways and ferroptosis-related immune cell infiltration play key roles in AAA/RAAA. GPX4 is a key ferroptosis-related gene in AAA. Ferroptosis and related genes might be promising targets in the treatment of AAA/RAAA.

Statin therapy protects against abdominal aortic aneurysms by inducing the accumulation of regulatory T cells in ApoE-/- mice

CD4⁺CD25⁺ regulatory T cells (Tregs) have been shown to protect against abdominal aortic aneurysm (AAA) progression. Statins have immunomodulatory properties, and their effect on AAA partly depends on immune-related mechanisms. In this study, we aimed to explore whether there is an association between statins and Tregs in AAA progression. Sixty ApoE^-/- mice were randomly divided into four groups (n = 15 per group): A, saline group; B, control group; C, simvastatin group (intragastric administration of simvastatin); and D, PC61 group (simvastatin combined with an intraperitoneal injection of 100 μg CD25-depleting antibody PC61). After 2 weeks of simvastatin treatment, the mice received a continuous subcutaneous infusion of angiotensin II (Ang II; B, C, and D groups) or saline (A group) for 28 days. Simvastatin therapy for 6 weeks significantly decreased the incidence and severity of AAA and inhibited the apoptosis of smooth muscle cells and generation of reactive oxygen species, which was partly abolished after the injection of PC61 antibody. Importantly, simvastatin increased the number of Tregs and the levels of Treg-associated cytokines (TGF-β and IL-10) and decreased the level of IL-17 both in aortic tissues and serum. Interestingly, simvastatin attenuated Ang II-induced gut microbial dysbiosis, which might be associated with the accumulation of Tregs. In conclusion, simvastatin therapy prevented the development of AAA induced by Ang II in ApoE^-/- mice, which might be partly due to the induction of Treg accumulation. In addition, simvastatin regulated gut microbial dysbiosis, which might also be associated with Treg generation.

Trained Immunity in Perivascular Adipose Tissue of Abdominal Aortic Aneurysm—A Novel Concept for a Still Elusive Disease

Abdominal aortic aneurysm (AAA) is a chronic, life-threatening vascular disease whose only therapeutic option is a surgical repair to prevent vessel rupture. The lack of medical therapy results from an inadequate understanding of the etiopathogenesis of AAA. Many studies in animal and human models indicate a ‘short-circuiting’ of the regulation of the inflammatory-immune response as a major player in the AAA chronic process. In this regard, perivascular adipose tissue (PVAT) has received increasing interest because its dysfunction affects large arteries primarily through immune cell infiltration. Consistently, we have recently produced evidence that innate and adaptive immune cells present in the PVAT of AAAs contribute to sustaining a damaging inflammatory loop. However, it is still unclear how the complex crosstalk between adaptive and innate immunity can be self-sustaining. From our perspective, trained immunity may play a role in this crosstalk. Trained immunity is defined as a form of innate immune memory resulting in enhanced responsiveness to repeated triggers. Specific innate stimuli and epigenetic and metabolic reprogramming events induce and shape trained immunity in myeloid progenitor cells improving host defense, but also contributing to the progression of immune-mediated and chronic inflammatory diseases. Here we present this hypothesis with data from the literature and our observations to support it.

Mechanisms of abdominal aortic aneurysm progression: A review

Abdominal aortic aneurysm (AAA) is a common disease associated with significant cardiovascular morbidity and mortality. Up to now, there is still controversy on the choice of treatment method of AAA. Even so, the mechanisms of AAA progression are poorly defined, making targeting new therapies problematic. Current evidence favors an interaction of the hemodynamic microenvironment with local and systemic immune responses. In this review, we aim to provide an update of mechanisms in AAA progression, involving hemodynamics, perivascular adipose tissue, adventitial fibroblasts, vasa vasorum remodeling, intraluminal thrombus, and distribution of macrophage subtypes.

Abdominal Aortic Aneurysm: Roles of Inflammatory Cells

Abdominal aortic aneurysms (AAAs) are local dilations of infrarenal segment of aortas. Molecular mechanisms underlying the pathogenesis of AAA remain not fully clear. However, inflammation has been considered as a central player in the development of AAA. In the past few decades, studies demonstrated a host of inflammatory cells, including T cells, macrophages, dendritic cells, neutrophils, B cells, and mast cells, etc. infiltrating into aortic walls, which implicated their crucial roles. In addition to direct cell contacts and cytokine or protease secretions, special structures like inflammasomes and neutrophil extracellular traps have been investigated to explore their functions in aneurysm formation. The above-mentioned inflammatory cells and associated structures may initiate and promote AAA expansion. Understanding their impacts and interaction networks formation is meaningful to develop new strategies of screening and pharmacological interventions for AAA. In this review, we aim to discuss the roles and mechanisms of these inflammatory cells in AAA pathogenesis.

Mouse models for abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) rupture is estimated to cause 200,000 deaths each year. Currently, the only treatment for AAA is surgical repair; however, this is only indicated for large asymptomatic, symptomatic or ruptured aneurysms, is not always durable, and is associated with a risk of serious perioperative complications. As a result, patients with small asymptomatic aneurysms or who are otherwise unfit for surgery are treated conservatively, but up to 70% of small aneurysms continue to grow, increasing the risk of rupture. There is thus an urgent need to develop drug therapies effective at slowing AAA growth. This review describes the commonly used mouse models for AAA. Recent research in these models highlights key roles for pathways involved in inflammation and cell turnover in AAA pathogenesis. There is also evidence for long non-coding RNAs and thrombosis in aneurysm pathology. Further well-designed research in clinically relevant models is expected to be translated into effective AAA drugs.

Patterns of immune infiltration in stable and raptured abdominal aortic aneurysms: A gene-expression-based retrospective study

BACKGROUND

Abdominal aortic aneurysm (AAA) is a disease characterized by weakening arterial wall and permanent expansion with high mortality once rupture, which was involved with immune system activation. However, owing to technical difficulties, previous research has limited the impact of one or limited immune cells on AAA.

METHODS

We analyzed the composition of immune cells using the CIBERSORT algorithm through transcriptome sequencing data from patients with stable (eAAA) and ruptured aneurysms (rAAA). The whole transcriptome sequencing data, including 17 patients with ruptured AAA and 31 patients with stable AAA were downloaded from Gene Expression Omnibus (GEO, GSE98278). After normalizing and data processing, five rAAA and seventeen eAAA patients entered the follow-up analysis. We performed Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis to identify several pathways that were significantly enriched in rAAA compared to eAAA tissues.

RESULTS

We demonstrated that the compositions of infiltrative immune cell in eAAA and rAAA were different. Naïve B cells, both resting and activated CD4+ memory T cells were found significantly higher in ruptured AAA, while memory B cells and activated mast cells were much less in ruptured AAA than that in stable AAA. Besides, PTX3 was significantly highly expressed in rAAA, which might be associated with the complement system and polarization of macrophages. Finally, differentially expressed genes and the related immune cells were mapped in a network to reveal the relationship between gene expression and infiltrative immune cells.

CONCLUSION

We identified the infiltrated immune cell profile of eAAA and rAAA patients, which might be the potential target of AAA treatment.

Pathophysiology of Aortic Aneurysms: Insights from Animal Studies

Aortic aneurysms are defined as dilations of the aorta greater than 50 percent. Currently, the only effective treatment for aortic aneurysms is surgical repair, which is recommended only to those that meet criteria. There is no available pharmaceutical therapy to slow aneurysm growth and thus prevent lethal rupture. The development of a number of murine models has allowed in depth studies of various cellular and extracellular components of aneurysm pathophysiology. The identification of key therapeutic targets has resulted in several clinical trials evaluating pharmaceutical candidates to treat aneurysm progression. In this review, we focus on providing recent updates on developments in murine models of aortic aneurysm. In addition, we discuss recent studies of the various cellular and extracellular components of the aorta along with the abutting aortic structures that contribute to aneurysm development and progression.