Characterization of CD4+ T Cell Subsets in Patients with Abdominal Aortic Aneurysms

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.

T cells in abdominal aortic aneurysm: immunomodulation and clinical application

Abdominal aortic aneurysm (AAA) is characterized by inflammatory cell infiltration, extracellular matrix (ECM) degradation, and vascular smooth muscle cell (SMC) dysfunction. The inflammatory cells involved in AAA mainly include immune cells including macrophages, neutrophils, T-lymphocytes and B lymphocytes and endothelial cells. As the blood vessel wall expands, more and more lymphocytes infiltrate into the outer membrane. It was found that more than 50% of lymphocytes in AAA tissues were CD3+ T cells, including CD4+, CD8+T cells, γδ T cells and regulatory T cells (Tregs). Due to the important role of T cells in inflammatory response, an increasing number of researchers have paid attention to the role of T cells in AAA and dug into the relevant mechanism. Therefore, this paper focuses on reviewing the immunoregulatory role of T cells in AAA and their role in immunotherapy, seeking potential targets for immunotherapy and putting forward future research directions.

A review of current status of cell-based therapies for aortic aneurysms

An aortic aneurysm (AA) is defined as focal aortic dilation that occurs mainly with older age and with chronic inflammation associated with atherosclerosis. The aneurysmal wall is a complex inflammatory environment characterized by endothelial dysfunction, macrophage activation, vascular smooth muscle cell (VSMC) apoptosis, and the production of proinflammatory molecules and matrix metalloproteases (MMPs) secreted by infiltrated inflammatory cells such as macrophages, T and B cells, dendritic cells, neutrophils, mast cells, and natural killer cells. To date, a considerable number of studies have been conducted on stem cell research, and growing evidence indicates that inflammation and tissue repair can be controlled through the functions of stem/progenitor cells. This review summarizes current cell-based therapies for AA, involving mesenchymal stem cells, VSMCs, multilineage-differentiating stress-enduring cells, and anti-inflammatory M2 macrophages. These cells produce beneficial outcomes in AA treatment by modulating the inflammatory environment, including decreasing the activity of proinflammatory molecules and MMPs, increasing anti-inflammatory molecules, modulating VSMC phenotypes, and preserving elastin. This article also describes detailed studies on pathophysiological mechanisms and the current progress of clinical trials.

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.

Immune and inflammatory mechanisms of abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a life-threatening cardiovascular disease. Immune-mediated infiltration and a destruction of the aortic wall during AAA development plays significant role in the pathogenesis of this disease. While various immune cells had been found in AAA, the mechanisms of their activation and function are still far from being understood. A better understanding of mechanisms regulating the development of aberrant immune cell activation in AAA is essential for the development of novel preventive and therapeutic approaches. In this review we summarize current knowledge about the role of immune cells in AAA and discuss how pathogenic immune cell activation is regulated in this disease.

The role of phosphoinositide 3-kinases in immune-inflammatory responses: potential therapeutic targets for abdominal aortic aneurysm

The pathogenesis of abdominal aortic aneurysm (AAA) includes inflammatory responses, matrix metalloproteinases (MMPs) degradation, VSMC apoptosis, oxidative stress, and angiogenesis, among which the inflammatory response plays a key role. At present, surgery is the only curing treatment, and no effective drug can delay AAA progression in clinical practice. Therefore, searching for a signaling pathway related to the immune-inflammatory response is an essential direction for developing drugs targeting AAA. Recent studies have confirmed that the PI3K family plays an important role in many inflammatory diseases and is involved in regulating various cellular functions, especially in the immune-inflammatory response. This review focuses on the role of each isoform of PI3K in each stage of AAA immune-inflammatory response, making available explorations for a deeper understanding of the mechanism of inflammation and immune response during the formation and development of AAA.

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.

Interleukin-35 ameliorates cardiovascular disease by suppressing inflammatory responses and regulating immune homeostasis

The immune response is of great significance in the initiation and progression of a diversity of cardiovascular diseases involving pro-and anti-inflammatory cytokines. Interleukin-35 (IL-35), a cytokine of the interleukin-12 family, is a novel anti-inflammation and immunosuppressive cytokine, maintaining inflammatory suppression and regulating immune homeostasis. The role of IL-35 in cardiovascular diseases (CVDs) has aroused enthusiastic attention, a diversity of experimental or clinical evidence has indicated that IL-35 potentially has a pivot role in protecting against cardiovascular diseases, especially atherosclerosis and myocarditis. In this review, we initiate an overview of the relationship between Interleukin-35 and cardiovascular diseases, including atherosclerosis, acute coronary syndrome, pulmonary hypertension, abdominal aortic aneurysm, heart failure, myocardial ischemia-reperfusion, aortic dissection and myocarditis. Although the specific molecular mechanisms entailing the protective effects of IL-35 remain an unsolved issue, targeted therapies with IL-35 might provide a promising and effective solution to prevent and cure cardiovascular diseases.

AAA Revisited: A Comprehensive Review of Risk Factors, Management, and Hallmarks of Pathogenesis

Despite declining incidence and mortality rates in many countries, the abdominal aortic aneurysm (AAA) continues to represent a life-threatening cardiovascular condition with an overall prevalence of about 2-3% in the industrialized world. While the risk of AAA development is considerably higher for men of advanced age with a history of smoking, screening programs serve to detect the often asymptomatic condition and prevent aortic rupture with an associated death rate of up to 80%. This review summarizes the current knowledge on identified risk factors, the multifactorial process of pathogenesis, as well as the latest advances in medical treatment and surgical repair to provide a perspective for AAA management.

Reversal of elastase-induced abdominal aortic aneurysm following the delivery of nanoparticle-based pentagalloyl glucose (PGG) is associated with reduced inflammatory and immune markers

OBJECTIVE

An Abdominal aortic aneurysm (AAA), a deadly disease in elderly population, is featured by expansion of aortic diameter, degradation and weakening of vasculature. Its common and significant characteristics are disarray and inflammation in vasculature. We tested the hypothesis that the reversal of abdominal aortic aneurysm by pentagalloyl glucose-loaded nanoparticles (PGG-NPs) therapy that targets degraded elastin suppresses inflammatory and immune markers to ameliorate the pathophysiology of the disease in advance stage aneurysm in a porcine pancreatic elastase (PPE)-induced mouse model of AAA.

METHODS AND RESULTS

After induction of aneurysm in pathogen-free C57BL/6 male mice by applying PPE peri-adventitially to the abdominal aorta, once a week for two doses of intravenous injections of pentagalloyl glucose-loaded nanoparticles (PGG-NPs) conjugated with elastin targeted antibody were used to reverse the aneurysms. We showed that PGG-NPs therapy could suppress infiltration of macrophages, CD8 and CD4 subsets of T cells, matrix metalloproteinases (MMPs), inflammatory cytokines interferon (IFN-γ) and interleukin (IL)-6 at the local and systemic level. Moreover, such PGG-NPs therapy increases the induction of anti-inflammatory cytokines IL-13, IL-27 and IL-10 at the local and systemic level. The therapy also led to remodeling of elastic lamina at the aneurysm site.

CONCLUSION

Nanoparticles-loaded pentagalloyl glucose therapy can be an effective treatment option against advanced stage aneurysms to reverse the disease by ameliorating inflammation and restoring arterial homeostasis.

The elevated expression of TLR4 and MMP9 in human abdominal aortic aneurysm tissues and its implication

Background

Toll-like receptor 4 (TLR4) and matrix metalloproteinase 9 (MMP9) have been investigated to play significant roles in the formation of abdominal aortic aneurysm (AAA). But the reports on the expression pattern of TLR4 and MMP9 in human AAA specimens were relatively scant. The aim of this study was to make a detailed analysis of TLR4 and MMP9 expression in situ and their association with clinical parameters involved in human AAA.

Methods

40 AAA specimens were obtained from full-thickness aneurysmal tissues at the maximal dilation area during the open surgical repair, and 8 non-aneurysmal abdominal aortas from transplant donors served as controls. Expression of TLR4 and MMP9 protein was determined by immunohistochemistry.

Results

There were increased levels of TLR4 and MMP9 expression in human AAA tissues. Compared with macrophages or SMCs, lymphocytes showed a higher positive rate of TLR4 and MMP9 staining, and an elevated ratio of high MMP9 expression (all P < 0.05). There existed a significant association between TLR4 and MMP9 expression (r = 0.767, P < 0.001), and both TLR4 and MMP9 levels were statistically related to circulating CRP. Moreover, TLR4 expression in situ indicated a positive correlation with its serum level (r = 0.654, P = 0.006). Multiple analysis revealed that high TLR4 expression in situ was associated with the risk of large AAA (OR = 6.211, 95%CI = 1.226–31.480, P = 0.027), while high MMP9 expression was correlated to the presence of thrombus within AAA (OR = 5.494, 95%CI = 1.181–25.562, P = 0.030), separately compared with their low expression.

Conclusions

This study confirmed the overexpression of TLR4 and MMP9 in human AAA tissues, and their close relationship implying in the pathogenesis of AAA. We further provided evidence that TLR4 had a potential effect on AAA size and MMP9 could influence the occurrence of thrombus within AAA.

Inflammatory Gene Expression of Human Perivascular Adipose Tissue in Abdominal Aortic Aneurysms

OBJECTIVE

Perivascular adipose tissue (PVAT) contributes to vascular homeostasis and is increasingly linked to vascular pathology. PVAT density and volume were associated with abdominal aortic aneurysm (AAA) presence and dimensions on imaging. However, mechanisms underlying the role of PVAT in AAA have not been clarified. This study aimed to explore differences in PVAT from AAA using gene expression and functional tests.

METHODS

Human aortic PVAT and control subcutaneous adipose tissue were collected during open AAA surgery. Gene analyses and functional tests were performed. The control group consisted of healthy aorta from non-living renal transplant donors. Gene expression tests were performed to study genes potentially involved in various inflammatory processes and AAA related genes. Live PVAT and subcutaneous adipose tissue (SAT) from AAA were used for ex vivo co-culture with smooth muscle cells (SMCs) retrieved from non-pathological aortas.

RESULTS

Adipose tissue was harvested from 27 AAA patients (n [gene expression] = 22, n [functional tests] = 5) and five control patients. An increased inflammatory gene expression of PTPRC (p = .008), CXCL8 (p = .033), LCK (p = .003), CCL5 (p = .004) and an increase in extracellular matrix breakdown marker MMP9 (p = .016) were found in AAA compared with controls. Also, there was a decreased anti-inflammatory gene expression of PPARG in AAA compared with controls (p = .040). SMC co-cultures from non-pathological aortas with PVAT from AAA showed increased MMP9 (p = .033) and SMTN (p = .008) expression and SAT increased SMTN expression in these SMC.

CONCLUSION

The data revealed that PVAT from AAA shows an increased pro-inflammatory and matrix metallopeptidase gene expression and decreased anti-inflammatory gene expression. Furthermore, increased expression of genes involved in aneurysm formation was found in healthy SMC co-culture with PVAT of AAA patients. Therefore, PVAT from AAA might contribute to inflammation of the adjacent aortic wall and thereby plays a possible role in AAA pathophysiology. These proposed pathways of inflammatory induction could reveal new therapeutic targets in AAA treatment.

Interleukin 12p40 Deficiency Promotes Abdominal Aortic Aneurysm by Activating CCN2/MMP2 Pathways

Background Development of abdominal aortic aneurysm (AAA) is associated with proinflammatory cytokines including interleukin-12 (IL12). Deficiency of interleukin 12p40 (IL12p40) increases localized fibrotic events by promoting TGFβ2 (transforming growth factor β)-dependent anti-inflammatory response. Here, we determined whether IL12p40 deficiency in apolipoprotein E-/- mice attenuates the development of AAA by antagonizing proinflammatory response. Methods and Results Double knockout (DKO) mice were generated by crossbreeding IL12p40-/- mice with apolipoprotein E-/- mice (n=12). Aneurysmal studies were performed using angiotensin II (1 µg/kg/min; subcutaneous). Surprisingly, DKO mice did not prevent the development of AAA with angiotensin II infusion. Immunohistological analysis, however, showed distinct pathological features between apolipoprotein E-/- and DKO mice. Polymerase chain reaction (7 day) and cytokine arrays (28 day) of the aortic tissues from DKO mice showed significantly increased expression of cytokines related to anti-inflammatory response (interleukin 5 and interleukin 13), synthetic vascular smooth muscle cell phenotype (Activin receptor-like kinase-1 (ALK-1), artemin, and betacellulin) and T helper 17-associated response (4-1BB, interleukin-17e (Il17e) and Cd40 ligand (Cd-40L)). Indeed, DKO mice exhibited increased expression of the fibro-proteolytic pathway in the medial layer of aortae induced by cellular communication network factor 2 (CCN2) and Cd3+IL17+ cells compared with apolipoprotein E-/- mice. Laser capture microdissection showed predominant expression of CCN2/TGFβ2 in the medial layer of human AAA. Finally, Ccn2 haploinsufficiency in the mice showed decreased AAA incidence in response to elastase infusion, associated with decreased matrix metalloproteinase-2 expression. Conclusions Our study reveals novel roles for IL12p40 deficiency in inducing fibro-proteolytic activities in the aneurysmal mouse model. Mechanistically, these effects of IL12p40 deficiency are mediated by CCN2/matrix metalloproteinase-2 crosstalk in the medial layer of aneurysmal aortae.

Dilatation of Aortic Neck and Common Iliac Arteries after Open Repair of Abdominal Aortic Aneurysms: Long-Term Follow-Up According to Aortic Reconstruction Configuration

BACKGROUND

Several studies in the literature report continued proximal aorta and distal iliac artery dilatation after surgical correction of an abdominal aortic aneurysm (AAA). The purpose of this study is to evaluate these findings, in a South American population, and relate them to the type of configuration of the open procedure aortic reconstruction.

METHODS

This is a retrospective review of ultrasonographic follow-up of patients submitted to open repair of AAA from 1989 to 2013, reporting proximal aorta dilatation (≥3 cm) and distal iliac artery dilatation (≥1.5 cm).

RESULTS

A total of 155 patients were included. Life-table freedom at the intervals 11 < 15 years and ≥15 years were 47% and 23% for proximal dilatation and 63% and 38% for distal iliac arteries dilatation, respectively. There were more proximal and distal dilatations in patients submitted to more extensive aortic reconstructions (aorto-aortic 13% and 22% vs aorto-bilateral common iliacs 27% and 8% vs aorto-unilateral or bilateral external iliacs 27% and 32% and aorto-femoral 67% and 0%) P < 0.0001. Juxtarenal anastomosis was also correlated with more proximal dilatations (42% vs 21%, P = 0,046). There were two proximal and three distal anastomosis pseudoaneurysms.

CONCLUSIONS

The presence of more extensive degenerative disease at the time of operation, requiring juxtarenal or more distal iliac reconstructions, may pose an increased risk of proximal aorta and iliac artery dilatation during follow-up. This study corroborates that significant changes are found after 7 to 10 years of the operation, reinforcing the need for long-term monitoring.

Pathogenic mechanisms and the potential of drug therapies for aortic aneurysm

Aortic aneurysm is a permanent focal dilation of the aorta. It is usually an asymptomatic disease but can lead to sudden death due to aortic rupture. Aortic aneurysm-related mortalities are estimated at ∼200,000 deaths per year worldwide. Because no pharmacological treatment has been found to be effective so far, surgical repair remains the only treatment for aortic aneurysm. Aortic aneurysm results from changes in the aortic wall structure due to loss of smooth muscle cells and degradation of the extracellular matrix and can form in different regions of the aorta. Research over the past decade has identified novel contributors to aneurysm formation and progression. The present review provides an overview of cellular and noncellular factors as well as enzymes that process extracellular matrix and regulate cellular functions (e.g., matrix metalloproteinases, granzymes, and cathepsins) in the context of aneurysm pathogenesis. An update of clinical trials focusing on therapeutic strategies to slow abdominal aortic aneurysm growth and efforts underway to develop effective pharmacological treatments is also provided.

T Cells Are Dominant Population in Human Abdominal Aortic Aneurysms and Their Infiltration in the Perivascular Tissue Correlates With Disease Severity

Abdominal Aortic Aneurysm (AAA) is a major cause of cardiovascular mortality. Adverse changes in vascular phenotype act in concert with chronic inflammation to promote AAA progression. Perivascular adipose tissue (PVAT) helps maintain vascular homeostasis but when inflamed and dysfunctional, can also promote vascular pathology. Previous studies suggested that PVAT may be an important site of vascular inflammation in AAA; however, a detailed assessment of leukocyte populations in human AAA, their anatomic location in the vessel wall and correlation to AAA size remain undefined. Accordingly, we performed in depth immunophenotyping of cells infiltrating the pathologically altered perivascular tissue (PVT) and vessel wall in AAA samples at the site of maximal dilatation (n = 51 patients). Flow cytometry revealed that T cells, rather than macrophages, are the major leukocyte subset in AAA and that their greatest accumulations occur in PVT. Both CD4⁺ and CD8⁺ T cell populations are highly activated in both compartments, with CD4⁺ T cells displaying the highest activation status within the AAA wall. Finally, we observed a positive relationship between T cell infiltration in PVT and AAA wall. Interestingly, only PVT T cell infiltration was strongly related to tertiles of AAA size. In summary, this study highlights an important role for PVT as a reservoir of T lymphocytes and potentially as a key site in modulating the underlying inflammation in AAA.