Lysyl hydroxylase 1 (LH1) deficiency promotes angiotensin II (Ang II)-induced dissecting abdominal aortic aneurysm

Dimethyl fumarate is repurposed to ameliorate aortic aneurysm and dissection in mice

Aortic aneurysm and dissection pose fatal threats but no effective drug therapies are available. Previous work has been directed to reduce risk factors or target key pathological events, but none of the translational efforts succeeds. Here, we attempt to repurpose dimethyl fumarate (DMF), an FDA-approved immunomodulatory drug for multiple sclerosis, for the treatment of aortic aneurysm and dissection. In three preclinical mouse models of abdominal aortic aneurysm (porcine pancreatic elastase perfusion or CaCl2 incubation) and thoracic aortic aneurysm and dissection (β-Aminopropionitrile feeding), DMF invariably protected mice from aneurysm growth, aortic dissection, rupture and death. Histological H&E and EVG staining demonstrated aortic architecture-preserving effects of DMF. Through transcriptome profiling and the connectivity map (CMap), we showed that DMF restored SRC-FAK signaling in aortic smooth muscle cells and increased collagen I turnover in the tunica media. Our work suggests the potential of DMF being repurposed for aortic aneurysm and dissection, and highlights the importance of SRC-FAK signaling in aortic homeostasis.

Decellularized adipose matrix hydrogel-based in situ delivery of antagomiR-150-5p for rat abdominal aortic aneurysm therapy

Abdominal aortic aneurysm (AAA) is a progressive aortic disease featured by inflammation, vascular smooth muscle cells (VSMCs) depletion, and elastin degradation. MicroRNAs were related to AAA formation, which bring the approach for precise and targeted drug therapy for AAA. We developed a new strategy based on decellularized adipose matrix (DAM) hydrogel immobilized on the adventitia to release antagomiR-150-5p for preventing the AAA development. In this study, Cacl2-induced and elastase-induced rat AAA models were established. We found that miR-150-5p was upregulated while Notch3 was downregulated in two rat AAA models. Then a mold was designed for shaping hydrogel for miR-150-5p delivery around the abdominal aorta. Interestingly, inhibition of miR-150-5p in AAA by local release of antagomiR-150-5p with DAM hydrogel significantly prevented aortic dilation and elastin degradation. Moreover, inflammatory cell infiltration, the expression of inflammatory cytokines (MCP-1, TNF-α, and NF-κB (p65)), and matrix metalloproteinases (MMP-2, MMP-9) were increased while Notch3 and α-SMA were decreased in rat AAA, which can be attenuated by antagomiR-150-5p treatment. In VSMCs with TNF-α stimulation, we further demonstrated that inhibition of miR-150-5p downregulated NF-κB (p65), MMP-2, and MMP-9 and upregulated elastin via Notch3. This work presents a translational potential strategy for AAA repair via DAM hydrogel sustained release of antagomiR-150-5p, and highlights the mechanism of miR-150-5p during AAA progression by regulating Notch3.

FGF21 promotes angiotensin II-induced abdominal aortic aneurysm via PI3K/AKT/mTOR pathway

BACKGROUND

Abdominal aortic aneurysm (AAA) is a potentially fatal vascular disorder with a high mortality rate. It was previously reported that fibroblast growth factor 21 (FGF21) was highly expressed in AAA patients. Nonetheless, its underlying mechanism in AAA progression is unclarified.

METHODS

Angiotensin II (Ang-II) was used to induce AAA in human aortic vascular smooth muscle cells (HASMCs) and mouse models. Western blotting and RT-qPCR were utilized for measuring protein and RNA levels. Immunofluorescence staining was utilized for detecting LC3B expression in HASMCs. Elastica van Gieson staining was conducted for histological analysis of the abdominal aortas of mice.

RESULTS

FGF21 displayed a high level in Ang-II-stimulated HASMCs and AAA mice. FGF21 depletion ameliorated abdominal aorta dilation and Ang-II-triggered pathological changes in mice. FGF21 silencing hindered autophagy and PI3K/AKT/mTOR pathway.

CONCLUSIONS

FGF21 contributes to AAA progression by enhancing autophagy and activating PI3K/AKT/mTOR pathway.

Enhanced expression of miR-20a driven by nanog exacerbated the degradation of extracellular matrix in thoracic aortic dissection

Thoracic aortic dissection (TAD) is a life-threatening vascular disease manifested as intramural bleeding in the medial layers of the thoracic aorta. The key histopathologic feature of TAD is medial degeneration, characterized by depletion of vascular smooth muscle cells (VSMCs) and degradation of extracellular matrix (ECM). MicroRNA, as essential epigenetic regulators, can inhibit the protein expression of target genes without modifying the sequences. This study aimed to elucidate the role and underlying mechanism of miR-20a, a member of the miR-17-92 cluster, in regulating ECM degradation during the pathogenesis of TAD. The expression of the miR-17-92 cluster was significantly increased in synthetic VSMCs derived from TAD lesions compared to contractile VSMCs isolated from normal thoracic aortas. Notably, the expression of miR-20a was increased in VSMCs in response to serum exposure and various stimuli. In TAD lesions, the expression of miR-20a was significantly negatively correlated with that of elastin. Elevated expression of miR-20a was also observed in thoracic aortas of TAD mice induced by β-aminopropionitrile fumarate and angiotensin II. Overexpression of miR-20a via mimic transfection enhanced the growth and invasive capabilities of VSMCs, with no significant impact on their migratory activity or the expression of phenotypic markers (α-SMA, SM22, and OPN). Silencing of miR-20a with inhibitor transfection mitigated the hyperactivation of MMP2 in VSMCs stimulated by PDGF-bb, as evidenced by reduced levels of active-MMP2 and increased levels of pro-MMP2. Subsequently, TIMP2 was identified as a novel target gene of miR-20a. The role of miR-20a in promoting the activation of MMP2 was mediated by the suppression of TIMP2 expression in VSMCs. In addition, the elevated expression of miR-20a was found to be directly driven by Nanog in VSMCs. Collectively, these findings indicate that miR-20a plays a crucial role in maintaining the homeostasis of the thoracic aortic wall during TAD pathogenesis and may represent a potential therapeutic target for TAD.

Macrophage ILF3 promotes abdominal aortic aneurysm by inducing inflammatory imbalance in male mice

Imbalance of proinflammatory and anti-inflammatory responses plays a crucial role in the progression of abdominal aortic aneurysms. ILF3, a known modulator of the innate immune response, is involved in cardiovascular diseases. This study aims to investigate the role of ILF3 in abdominal aortic aneurysm formation. Here, we use multi-omics analyzes, transgenic male mice, and multiplex immunohistochemistry to unravel the underlying involvement of ILF3 in abdominal aortic aneurysms. The results show that macrophage ILF3 deficiency attenuates abdominal aortic aneurysm progression, while elevated macrophage ILF3 exacerbates abdominal aortic aneurysm lesions. Mechanistically, we reveal that macrophagic ILF3 increases NF-κB activity by hastening the decay of p105 mRNA, leading to amplified inflammation in macrophages. Meanwhile, ILF3 represses the anti-inflammatory action by inhibiting the Keap1-Nrf2 signaling pathway through facilitating the ILF3/eIF4A1 complex-mediated enhancement of Keap1 translational efficiency. Moreover, Bardoxolone Methyl treatment alleviates the severity of abdominal aortic aneurysm lesions in the context of elevated ILF3 expression. Together, our findings underscore the significance of macrophage ILF3 in abdominal aortic aneurysm development and suggest its potential as a promising therapeutic target for abdominal aortic aneurysms.

Identification and Validation of Diagnostic Model Based on Angiogenesis- and Epithelial Mesenchymal Transition-Related Genes in Myocardial Infarction

Background

Myocardial infarction (MI) is a chronic cardiovascular disease. This study aims to discern potentially angiogenesis- and epithelial mesenchymal transition (EMT)-related genes as biomarkers for MI diagnosis through bioinformatics.

Methods

All datasets and angiogenesis- and EMT-related genes were collected from the public database. The differentially expressed genes (DEGs) of MI and MI-related genes were acquired. DEGs, MI-related genes, and angiogenesis- and EMT-related genes were intersected to obtain hub genes. Functional enrichment, immune microenvironment, and transcription factors (TFs)-hub genes regulatory network analysis were performed. The diagnostic markers and models were developed and validated. Drug prediction and molecular docking were performed. Finally, diagnostic markers expressions were validated using RT-qPCR.

Results

A total of 224 angiogenesis- and EMT-related genes, 2,897 DEGs, 1,217 MI-related genes, and 9 hub genes were acquired. The immune infiltration levels of plasma cells, T cells CD4 memory activated, monocytes, macrophages M0, mast cells resting, and neutrophils were higher in patients with MI. LRPAP1, COLGALT1, QSOX1, THBD, VCAN, PLOD1, and PLAUR as the diagnostic markers were identified and used to construct diagnostic models, which can distinguish MI from controls well. Then, 9 drugs were screened, and the binding energies ranged from -7.08 to -5.21 kcal/mol. RT-qPCR results showed that the expression of LRPAP1, PLAUR, and PLOD1 was significantly increased in the MI group.

Conclusion

The 7 diagnostic markers may play potential roles in MI and could contribute to improved future diagnostics.

Advances and challenges in regenerative therapies for abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a significant source of mortality worldwide and carries a mortality of greater than 80% after rupture. Despite extensive efforts to develop pharmacological treatments, there is currently no effective agent to prevent aneurysm growth and rupture. Current treatment paradigms only rely on the identification and surveillance of small aneurysms, prior to ultimate open surgical or endovascular repair. Recently, regenerative therapies have emerged as promising avenues to address the degenerative changes observed in AAA. This review briefly outlines current clinical management principles, characteristics, and pharmaceutical targets of AAA. Subsequently, a thorough discussion of regenerative approaches is provided. These include cellular approaches (vascular smooth muscle cells, endothelial cells, and mesenchymal stem cells) as well as the delivery of therapeutic molecules, gene therapies, and regenerative biomaterials. Lastly, additional barriers and considerations for clinical translation are provided. In conclusion, regenerative approaches hold significant promise for in situ reversal of tissue damages in AAA, necessitating sustained research and innovation to achieve successful and translatable therapies in a new era in AAA management.

An Active Site Tyr Residue Guides the Regioselectivity of Lysine Hydroxylation by Nonheme Iron Lysine-4-hydroxylase Enzymes through Proton-Coupled Electron Transfer

Lysine dioxygenase (KDO) is an important enzyme in human physiology involved in bioprocesses that trigger collagen cross-linking and blood pressure control. There are several KDOs in nature; however, little is known about the factors that govern the regio- and stereoselectivity of these enzymes. To understand how KDOs can selectively hydroxylate their substrate, we did a comprehensive computational study into the mechanisms and features of 4-lysine dioxygenase. In particular, we selected a snapshot from the MD simulation on KDO5 and created large QM cluster models (A, B, and C) containing 297, 312, and 407 atoms, respectively. The largest model predicts regioselectivity that matches experimental observation with rate-determining hydrogen atom abstraction from the C4-H position, followed by fast OH rebound to form 4-hydroxylysine products. The calculations show that in model C, the dipole moment is positioned along the C4-H bond of the substrate and, therefore, the electrostatic and electric field perturbations of the protein assist the enzyme in creating C4-H hydroxylation selectivity. Furthermore, an active site Tyr233 residue is identified that reacts through proton-coupled electron transfer akin to the axial Trp residue in cytochrome c peroxidase. Thus, upon formation of the iron(IV)-oxo species in the catalytic cycle, the Tyr233 phenol loses a proton to the nearby Asp179 residue, while at the same time, an electron is transferred to the iron to create an iron(III)-oxo active species. This charged tyrosyl residue directs the dipole moment along the C4-H bond of the substrate and guides the selectivity to the C4-hydroxylation of the substrate.

Ang-1 and VEGF: central regulators of angiogenesis

Angiopoietin-1 (Ang-1) and Vascular Endothelial Growth Factor (VEGF) are central regulators of angiogenesis and are often inactivated in various cardiovascular diseases. VEGF forms complexes with ETS transcription factor family and exerts its action by downregulating multiple genes. Among the target genes of the VEGF-ETS complex, there are a significant number encoding key angiogenic regulators. Phosphorylation of the VEGF-ETS complex releases transcriptional repression on these angiogenic regulators, thereby promoting their expression. Ang-1 interacts with TEK, and this phosphorylation release can be modulated by the Ang-1-TEK signaling pathway. The Ang-1-TEK pathway participates in the transcriptional activation of VEGF genes. In summary, these elements constitute the Ang-1-TEK-VEGF signaling pathway. Additionally, Ang-1 is activated under hypoxic and inflammatory conditions, leading to an upregulation in the expression of TEK. Elevated TEK levels result in the formation of the VEGF-ETS complex, which, in turn, downregulates the expression of numerous angiogenic genes. Hence, the Ang-1-dependent transcriptional repression is indirect. Reduced expression of many target genes can lead to aberrant angiogenesis. A significant overlap exists between the target genes regulated by Ang-1-TEK-VEGF and those under the control of the Ang-1-TEK-TSP-1 signaling pathway. Mechanistically, this can be explained by the replacement of the VEGF-ETS complex with the TSP-1 transcriptional repression complex at the ETS sites on target gene promoters. Furthermore, VEGF possesses non-classical functions unrelated to ETS and DNA binding. Its supportive role in TSP-1 formation may be exerted through the VEGF-CRL5-VHL-HIF-1α-VH032-TGF-β-TSP-1 axis. This review assesses the regulatory mechanisms of the Ang-1-TEK-VEGF signaling pathway and explores its significant overlap with the Ang-1-TEK-TSP-1 signaling pathway.

Cellular, Molecular and Clinical Aspects of Aortic Aneurysm-Vascular Physiology and Pathophysiology

A disturbance of the structure of the aortic wall results in the formation of aortic aneurysm, which is characterized by a significant bulge on the vessel surface that may have consequences, such as distention and finally rupture. Abdominal aortic aneurysm (AAA) is a major pathological condition because it affects approximately 8% of elderly men and 1.5% of elderly women. The pathogenesis of AAA involves multiple interlocking mechanisms, including inflammation, immune cell activation, protein degradation and cellular malalignments. The expression of inflammatory factors, such as cytokines and chemokines, induce the infiltration of inflammatory cells into the wall of the aorta, including macrophages, natural killer cells (NK cells) and T and B lymphocytes. Protein degradation occurs with a high expression not only of matrix metalloproteinases (MMPs) but also of neutrophil gelatinase-associated lipocalin (NGAL), interferon gamma (IFN-γ) and chymases. The loss of extracellular matrix (ECM) due to cell apoptosis and phenotype switching reduces tissue density and may contribute to AAA. It is important to consider the key mechanisms of initiating and promoting AAA to achieve better preventative and therapeutic outcomes.

Disulfiram protects against abdominal aortic aneurysm by ameliorating vascular smooth muscle cells pyroptosis

PURPOSE

Recent studies demonstrated that pyroptosis is involved in abdominal aortic aneurysm (AAA) progression, suggesting a potential target for AAA treatment. This study aimed to identify if disulfiram could inhibit angiotensin II (Ang II)-induced vascular smooth muscle cells (VSMCs) damage, thereby exerting protective effects on AAA.

METHODS

The AAA mouse model was established by continuous subcutaneous Ang II infusion for 28 days. Then aortic tissue of the mice was isolated and subjected to RNA sequencing, qRT-PCR, Western blotting, and immunofluorescence staining. To explore the therapeutic effect of disulfiram, mice were orally administered disulfiram (50 mg/kg/day) or vehicle for 28 days accompanied with Ang II infusion. Pathological changes in aortic tissues were measured using microultrasound imaging analysis and histopathological analysis. In addition, inflammatory response, pyroptosis, and oxidative stress damage were examined in mouse aortic vascular smooth muscle (MOVAS) cells stimulated with Ang II in vitro.

RESULTS

The RNA sequencing and bioinformatic analysis results suggested that pyroptosis- and inflammation-related genes were significantly upregulated in AAA, consistent with the results of qRT-PCR and Western blotting. Most importantly, the therapeutic effect of disulfiram on AAA was identified in our study. First, disulfiram administration significantly attenuated Ang II-induced inflammation, pyroptosis, and oxidative stress in VSMCs, which is associated with the inhibition of the NF-κB-NLRP3 pathway. Second, in-vivo studies revealed that disulfiram treatment reduced AAA formation and significantly ameliorated collagen deposition and elastin degradation in the aortic wall.

CONCLUSION

Our findings suggest that disulfiram has a novel protective effect against AAA by inhibiting Ang II-induced VSMCs pyroptosis.

Early Progression of Abdominal Aortic Aneurysm is Decelerated by Improved Endothelial Barrier Function via ALDH2-LIN28B-ELK3 Signaling

The involvement of endothelial barrier function in abdominal aortic aneurysm (AAA) and its upstream regulators remains unknown. Single-cell RNA sequencing shows that disrupted endothelial focal junction is an early (3 days) and persistent (28 days) event during Angiotensin II (Ang II)-induced AAA progression. Consistently, mRNA sequencing on human aortic dissection tissues confirmed downregulated expression of endothelial barrier-related genes. Aldehyde dehydrogenase 2 (ALDH2), a negative regulator of AAA, is found to be upregulated in the intimal media of AAA samples, leading to testing its role in early-stage AAA. ALDH2 knockdown/knockout specifically in endothelial cells (ECs) significantly increases expression of EC barrier markers related to focal adhesion and tight junction, restores endothelial barrier integrity, and suppresses early aortic dilation of AAA (7 and 14 days post-Ang II). Mechanically, ELK3 acts as an ALDH2 downstream regulator for endothelial barrier function preservation. At the molecular level, ALDH2 directly binds to LIN28B, a regulator of ELK3 mRNA stability, hindering LIN28B binding to ELK3 mRNA, thereby depressing ELK3 expression and impairing endothelial barrier function. Therefore, preserving vascular endothelial barrier integrity via ALDH2-specific knockdown in ECs holds therapeutic potential in the early management of AAAs.

The risk factors of postoperative hypoxemia in patients with Stanford type A acute aortic dissection

Hypoxemia is one of the most common complications in patients after Stanford type A acute aortic dissection surgery. The aim of this study was to investigate the association of circulating ANG II level with postoperative hypoxemia and to identify the risk factors for postoperative hypoxemia in Stanford type A acute aortic dissection patients. In this study, 88 patients who underwent Stanford type A acute aortic dissection surgery were enrolled. Postoperative hypoxemia is defined by the oxygenation index (OI). Perioperative clinical data were collected and the serum ANG II and sACE2 levels were measured. The differences in the basic characteristics, intraoperative details, biochemical parameters, laboratory test data and clinical outcomes were compared between the hypoxemia group and the non-hypoxemia group by univariate analysis. Multivariate logistic regression analysis was performed on the variables with P < .1 in univariate analysis or that were considered clinically important to identify risk factors for postoperative hypoxemia. Twenty-five patients (28.4%) were considered to have postoperative hypoxemia (OI ≤ 200 mm Hg). The ANG II concentration remained a risk factor associated with postoperative hypoxemia [OR = 1.018, 95% CI (1.003-1.034), P = .022]. The other risk factors remaining in the logistic regression model were BMI [OR = 1.417, 95% CI (1.159-1.733), P = .001] and cTnI [OR = 1.003, 95% CI (1.000-1.005), P = .032]. Elevated levels of ANG II, BMI and cTnI are risk factors for postoperative hypoxemia in patients with Stanford type A acute aortic dissection.

Anti-CD47 immunotherapy as a therapeutic strategy for the treatment of breast cancer brain metastasis

The presence of cell surface protein CD47 allows cancer cells to evade innate and adaptive immune surveillance resulting in metastatic spread. CD47 binds to and activates SIRPα on the surface of myeloid cells, inhibiting their phagocytic activity. On the other hand, CD47 binds the matricellular protein Thrombospondin-1, limiting T-cell activation. Thus, blocking CD47 is a potential therapeutic strategy for preventing brain metastasis. To test this hypothesis, breast cancer patient biopsies were stained with antibodies against CD47 to determine differences in protein expression. An anti-CD47 antibody was used in a syngeneic orthotopic triple-negative breast cancer model, and CD47 null mice were used in a breast cancer brain metastasis model by intracardiac injection of the E0771-Br-Luc cell line. Immunohistochemical staining of patient biopsies revealed an 89% increase in CD47 expression in metastatic brain tumors compared to normal adjacent tissue (p ≤ 0.05). Anti-CD47 treatment in mice bearing brain metastatic 4T1br3 orthotopic tumors reduced tumor volume and tumor weight by over 50% compared to control mice (p ≤ 0.05) and increased IBA1 macrophage/microglia marker 5-fold in tumors compared to control (p ≤ 0.05). Additionally, CD47 blockade increased the M1/M2 macrophage ratio in tumors 2.5-fold (p ≤ 0.05). CD47 null mice had an 89% decrease in metastatic brain burden (p ≤ 0.05) compared to control mice in a brain metastasis model. Additionally, RNA sequencing revealed several uniquely expressed genes and significantly enriched genes related to tissue development, cell death, and cell migration tumors treated with anti-CD47 antibodies. Thus, demonstrating that CD47 blockade affects cancer cell and tumor microenvironment signaling to limit metastatic spread and may be an effective therapeutic for triple-negative breast cancer brain metastasis.

Smooth Muscle Heterogeneity and Plasticity in Health and Aortic Aneurysmal Disease

Vascular smooth muscle cells (VSMCs) are the predominant cell type in the medial layer of the aorta, which plays a critical role in the maintenance of aortic wall integrity. VSMCs have been suggested to have contractile and synthetic phenotypes and undergo phenotypic switching to contribute to the deteriorating aortic wall structure. Recently, the unprecedented heterogeneity and diversity of VSMCs and their complex relationship to aortic aneurysms (AAs) have been revealed by high-resolution research methods, such as lineage tracing and single-cell RNA sequencing. The aortic wall consists of VSMCs from different embryonic origins that respond unevenly to genetic defects that directly or indirectly regulate VSMC contractile phenotype. This difference predisposes to hereditary AAs in the aortic root and ascending aorta. Several VSMC phenotypes with different functions, for example, secreting VSMCs, proliferative VSMCs, mesenchymal stem cell-like VSMCs, immune-related VSMCs, proinflammatory VSMCs, senescent VSMCs, and stressed VSMCs are identified in non-hereditary AAs. The transformation of VSMCs into different phenotypes is an adaptive response to deleterious stimuli but can also trigger pathological remodeling that exacerbates the pathogenesis and development of AAs. This review is intended to contribute to the understanding of VSMC diversity in health and aneurysmal diseases. Papers that give an update on VSMC phenotype diversity in health and aneurysmal disease are summarized and recent insights on the role of VSMCs in AAs are discussed.

Molecular and Cellular Mechanisms Involved in Aortic Wall Aneurysm Development

Aortic aneurysms represent a very common pathology that can affect any segment of the aorta. These types of aneurysms can be localized on the thoracic segment or on the abdominal portion, with the latter being more frequent. Though there are similarities between thoracic and abdominal aortic aneurysms, these pathologies are distinct entities. In this article, we undertook a review regarding the different mechanisms that can lead to the development of aortic aneurysm, and we tried to identify the different manners of treatment. For a long time, aortic wall aneurysms may evolve in an asymptomatic manner, but this progressive dilatation of the aneurysm can lead to a potentially fatal complication consisting in aortic rupture. Because there are limited therapies that may delay or prevent the development of acute aortic syndromes, surgical management remains the most common manner of treatment. Even though, surgical management has improved much in the last years, thus becoming less invasive and sophisticated, the morbi-mortality linked to these therapies remains increased. The identification of the cellular and molecular networks triggering the formation of aneurysm would permit the discovery of modern therapeutic targets. Molecular and cellular mechanisms are gaining a bigger importance in the complex pathogenesis of aortic aneurysms. Future studies must be developed to compare the findings seen in human tissue and animal models of aortic aneurysm, so that clinically relevant conclusions about the aortic aneurysm formation and the pharmacological possibility of pathogenic pathways blockage can be drawn.

Research progress on the pathogenesis of aortic dissection

Aortic dissection (AD) is a critical cardiovascular disease due to the separation of media and adventitia caused by the rupture of vascular wall intima. The disease has a high mortality rate of about 1% to 3% for each additional hour, since the adventitia of the aorta can rupture and bleed to death at any time. Although great progress has been made in clinical treatment of aortic dissection, and the mortality rate has been significantly reduced, the pathogenesis is still not very clear. At present, related studies have confirmed that inflammation of aortic wall promotes the occurrence and development of AD. Although the mechanism of aortic dissection is more complicated, some studies have shown that the infiltration of monocytes/macrophages into the aortic wall is the main pathogenic mechanism of the disease. This review introduces the latest research results on the mechanism of macrophage infiltration and plasticity in aortic dissection.

Genome-Wide Identification of Immune-Related Alternative Splicing and Splicing Regulators Involved in Abdominal Aortic Aneurysm

The molecular mechanism of AAA formation is still poorly understood and has not been fully elucidated. The study was designed to identify the immune-related genes, immune-RAS in AAA using bioinformatics methods. The GSE175683 datasets were downloaded from the GEO database. The DEseq2 software was used to identify differentially expressed genes (DEGs). SUVA pipeline was used to quantify AS events and RAS events. KOBAS 2.0 server was used to identify GO terms and KEGG pathways to sort out functional categories of DEGs. The CIBERSORT algorithm was used with the default parameter for estimating immune cell fractions. Nine samples from GSE175683 were used to construct the co-disturbed network between expression of SFs and splicing ratio of RAS events. PCA analysis was performed by R package factoextra to show the clustering of samples, and the pheatmap package in R was used to perform the clustering based on Euclidean distance. The results showed that there were 3,541 genes significantly differentially expressed, of which 177 immune-related genes were upregulated and 48 immune-related genes were downregulated between the WT and WTA group. Immune-RAS events were mainly alt5P and IR events, and about 60% of it was complex splicing events in AAA. The WT group and the WTA group can be clearly distinguished in the first principal component by using the splicing ratio of immune-RAS events. Two downregulated genes, Nr4a1 and Nr4a2, and eight upregulated genes, Adipor2, Akt2, Bcl3, Dhx58, Pparg, Ptgds, Sytl1, and Vegfa were identified among the immune-related genes with RAS and DEGs. Eighteen differentially expressed SFs were identified and displayed by heatmap. The proportion of different types of cells and ratio of the average ratio of different cells were quite different. Both M1 and M2 types of macrophages and plasma cells were upregulated, while M0 type was downregulated in AAA. The proportion of plasma cells in the WTA group had sharply increased. There is a correlation between SF expression and immune cells/immune-RAS. Sf3b1, a splicing factor with significantly different expression, was selected to bind on a mass of immune-related genes. In conclusion, our results showed that immune-related genes, immune-RAS, and SFs by genome-wide identification were involved in AAA.