KLF4-dependent phenotypic modulation of smooth muscle cells has a key role in atherosclerotic plaque pathogenesis

Bioinformatic Analysis Revealed the Essential Regulatory Genes and Pathways of Early and Advanced Atherosclerotic Plaque in Humans

Atherosclerosis (AS) is a lipid-induced, chronic inflammatory, autoimmune disease affecting multiple arteries. Although much effort has been put into AS research in the past decades, it is still the leading cause of death worldwide. The complex genetic network regulation underlying the pathogenesis of AS still needs further investigation to provide effective targeted therapy for AS. We performed a bioinformatic microarray data analysis at different atherosclerotic plaque stages from the Gene Expression Omnibus database with accession numbers GSE43292 and GSE28829. Using gene set enrichment analysis, we further confirmed the immune-related pathways that play an important role in the development of AS. We are reporting, for the first time, that the metabolism of the three branched-chain amino acids (BCAAs; leucine, isoleucine, and valine) and short-chain fatty acids (SCFA; propanoate, and butanoate) are involved in the progression of AS using microarray data of atherosclerotic plaque tissue. Immune and muscle system-related pathways were further confirmed as highly regulated pathways during the development of AS using gene expression pattern analysis. Furthermore, we also identified four modules mainly involved in histone modification, immune-related processes, macroautophagy, and B cell activation with modular differential connectivity in the dataset of GSE43292, and three modules related to immune-related processes, B cell activation, and nuclear division in the dataset of GSE28829 also display modular differential connectivity based on the weighted gene co-expression network analysis. Finally, we identified eight key genes related to the pathways of immune and muscle system function as potential therapeutic biomarkers to distinguish patients with early or advanced stages in AS, and two of the eight genes were validated using the gene expression dataset from gene-deficient mice. The results of the current study will improve our understanding of the molecular mechanisms in the progression of AS. The key genes and pathways identified could be potential biomarkers or new drug targets for AS management.

Extracellular traps from activated vascular smooth muscle cells drive the progression of atherosclerosis

Extracellular DNA traps (ETs) represent an immune response by which cells release essential materials like chromatin and granular proteins. Previous studies have demonstrated that the transdifferentiation of vascular smooth muscle cells (VSMCs) plays a crucial role in atherosclerosis. This study seeks to investigate the interaction between CD68⁺ VSMCs and the formation of ETs and highlight its function in atherosclerosis. Here we show that ETs are inhibited, and atherosclerotic plaque formation is alleviated in male Myh11^CrePad4^flox/flox mice undergoing an adeno-associated-virus-8 (AAV8) mediating overexpression of proprotein convertase subtilisin/kexin type 9 mutation (PCSK9) injection and being challenged with a high-fat diet. Obvious ETs generated from CD68⁺ VSMCs are inhibited by Cl-amidine and DNase I in vitro. By utilizing VSMCs-lineage tracing technology and single-cell RNA sequencing (scRNA-seq), we demonstrate that the ETs from CD68⁺ VSMCs influence the progress of atherosclerosis by regulating the direction of VSMCs' transdifferentiation through STING-SOCS1 or TLR4 signaling pathway.

Long non-coding RNAs at the crossroad of vascular smooth muscle cell phenotypic modulation in atherosclerosis and neointimal formation

Despite extraordinary advances in the comprehension of the pathophysiology of atherosclerosis and the employment of very effective treatments, cardiovascular diseases are still a major cause of mortality and represent a large share of health expenditure worldwide. Atherosclerosis is a disease affecting the medium and large arteries, which consists of a progressive accumulation of fatty substances, cellular waste products and fibrous elements, which culminates in the buildup of a plaque obstructing the blood flow. Endothelial dysfunction represents an early pathological event, favoring immune cells recruitment and triggering local inflammation. The release of inflammatory cytokines and other signaling molecules stimulates phenotypic modifications in the underlying vascular smooth muscle cells, which, in physiological conditions, are responsible for the maintenance of vessels architecture while regulating vascular tone. Vascular smooth muscle cells are highly plastic and may respond to disease stimuli by de-differentiating and losing their contractility, while increasing their synthetic, proliferative, and migratory capacity. This phenotypic switching is considered a pathological hallmark of atherogenesis and is ruled by the activation of selective gene programs. The advent of genomics and the improvement of sequencing technologies deepened our knowledge of the complex gene expression regulatory networks mediated by non-coding RNAs, and favored the rise of innovative therapeutic approaches targeting the non-coding transcriptome. In the context of atherosclerosis, long non-coding RNAs have received increasing attention as potential translational targets, due to their contribution to the molecular dynamics modulating the expression of vascular smooth muscle cells contractile/synthetic gene programs. In this review, we will focus on the most well-characterized long non-coding RNAs contributing to atherosclerosis by controlling expression of the contractile apparatus and genes activated in perturbed vascular smooth muscle cells.

Smooth muscle cell fate decisions decipher a high-resolution heterogeneity within atherosclerosis molecular subtypes

BACKGROUND

Mounting evidence has revealed the dynamic variations in the cellular status and phenotype of the smooth muscle cell (SMC) are vital for shaping the atherosclerotic plaque microenvironment and ultimately mapping onto heterogeneous clinical outcomes in coronary artery disease. Currently, the underlying clinical significance of SMC evolutions remains unexplored in atherosclerosis.

METHODS

The dissociated cells from diseased segments within the right coronary artery of four cardiac transplant recipients and 1070 bulk samples with atherosclerosis from six bulk cohorts were retrieved. Following the SMC fate trajectory reconstruction, the MOVICS algorithm integrating the nearest template prediction was used to develop a stable and robust molecular classification. Subsequently, multi-dimensional potential biological implications, molecular features, and cell landscape heterogeneity among distinct clusters were decoded.

RESULTS

We proposed an SMC cell fate decision signature (SCFDS)-based atherosclerosis stratification system and identified three SCFDS subtypes (C1-C3) with distinguishing features: (i) C1 (DNA-damage repair type), elevated base excision repair (BER), DNA replication, as well as oxidative phosphorylation status. (ii) C2 (immune-activated type), stronger immune activation, hyper-inflammatory state, the complex as well as varied lesion microenvironment, advanced stage, the most severe degree of coronary stenosis severity. (iii) C3 (stromal-rich type), abundant fibrous content, stronger ECM metabolism, immune-suppressed microenvironment.

CONCLUSIONS

This study uncovered atherosclerosis complex cellular heterogeneity and a differentiated hierarchy of cell populations underlying SMC. The novel high-resolution stratification system could improve clinical outcomes and facilitate individualized management.

KLF4-PFKFB3-driven glycolysis is essential for phenotypic switching of vascular smooth muscle cells

Vascular smooth muscle cells (VSMCs) within atherosclerotic lesions undergo a phenotypic switching in a KLF4-dependent manner. Glycolysis plays important roles in transdifferentiation of somatic cells, however, it is unclear whether and how KLF4 mediates the link between glycolytic switch and VSMCs phenotypic transitions. Here, we show that KLF4 upregulation accompanies VSMCs phenotypic switching in atherosclerotic lesions. KLF4 enhances the metabolic switch to glycolysis through increasing PFKFB3 expression. Inhibiting glycolysis suppresses KLF4-induced VSMCs phenotypic switching, demonstrating that glycolytic shift is required for VSMCs phenotypic switching. Mechanistically, KLF4 upregulates expression of circCTDP1 and eEF1A2, both of which cooperatively promote PFKFB3 expression. TMAO induces glycolytic shift and VSMCs phenotypic switching by upregulating KLF4. Our study indicates that KLF4 mediates the link between glycolytic switch and VSMCs phenotypic transitions, suggesting that a previously unrecognized KLF4-eEF1A2/circCTDP1-PFKFB3 axis plays crucial roles in VSMCs phenotypic switching.

Chaetocin attenuates atherosclerosis progression and inhibits vascular smooth muscle cell phenotype switching

We aimed to explore the effect of chaetocin on atherosclerosis and its possible mechanism. In vitro, we observed that chaetocin treatment significantly inhibited the proliferation of VSMCs in concentration- and time-dependent manner. We also found that chaetocin suppressed the migration of VSMCs. Moreover, chaetocin treatment induced a contractile phenotype in VSMCs by increasing α-SMA and SM22α expression. In addition, chaetocin treatment attenuated the accumulation of H3K9me3 on VSMCs contractile gene promoters, which promoted the expression of α-SMA and SM22α. In vivo, chaetocin treatment decreased the H3K9me3 expression, diminished atherosclerotic plaque formation, and increased plaque stability by decreasing necrotic core area and lipid accumulation and increasing collagen content and contractile VSMC phenotype. We demonstrated a new function of chaetocin in inhibiting atherosclerosis progression and increasing plaque stability partly by inhibiting pathological phenotypic switching of VSMCs. These newly identified roles of chaetocin might provide a novel therapeutic target in atherosclerosis.

Smooth muscle cell specific NEMO deficiency inhibits atherosclerosis in ApoE−/− mice

The development of atherosclerotic plaques is the result of a chronic inflammatory response coordinated by stromal and immune cellular components of the vascular wall. While endothelial cells and leukocytes are well-recognised mediators of inflammation in atherosclerosis, the role of smooth muscle cells (SMCs) remains incompletely understood. Here we aimed to address the role of canonical NF-κB signalling in SMCs in the development of atherosclerosis. We investigated the role of NF-κB signalling in SMCs in atherosclerosis by employing SMC-specific ablation of NEMO, an IKK complex subunit that is essential for canonical NF-κB activation, in ApoE^−/− mice. We show that SMC-specific ablation of NEMO (NEMO^SMCiKO) inhibited high fat diet induced atherosclerosis in ApoE^−/− mice. NEMO^SMCiKO/ApoE^−/− mice developed less and smaller atherosclerotic plaques, which contained fewer macrophages, decreased numbers of apoptotic cells and smaller necrotic areas and showed reduced inflammation compared to the plaques of ApoE^−/− mice. In addition, the plaques of NEMO^SMCiKO/ApoE^−/− mice showed higher expression of α-SMA and lower expression of the transcriptional factor KLF4 compared to those of ApoE^−/− mice. Consistently, in vitro, NEMO-deficient SMCs exhibited reduced proliferation and migration, as well as decreased KLF4 expression and lower production of IL-6 and MCP-1 upon inflammatory stimulus (TNF or LPS) compared to NEMO-expressing SMCs. In conclusion, NEMO-dependent activation of NF-κB signalling in SMCs critically contributes to the pathogenesis of atherosclerosis by regulating SMC proliferation, migration and phenotype switching in response to inflammatory stimuli.

Smooth muscle cell FTO regulates contractile function

The fat mass and obesity gene (FTO) is a N6-methyladenosine RNA demethylase that was initially linked by Genome-wide association studies to increased rates of obesity. Subsequent studies have revealed multiple mass-independent effects of the gene, including cardiac myocyte contractility. We created a mouse with a conditional and inducible smooth muscle cell deletion of Fto (Myh11 Cre+ Ftofl/fl) and did not observe any changes in mouse body mass or mitochondrial metabolism. However, the mice had significantly decreased blood pressure (hypotensive), despite increased heart rate and sodium, and significantly increased plasma renin. Remarkably, the third-order mesenteric arteries from these mice had almost no myogenic tone or capacity to constrict to smooth muscle depolarization or phenylephrine. Microarray analysis from Fto-/--isolated smooth muscle cells demonstrated a significant decrease in serum response factor (Srf) and the downstream effectors Acta2, Myocd, and Tagln; this was confirmed in cultured human coronary arteries with FTO siRNA. We conclude Fto is an important component to the contractility of smooth muscle cells.NEW & NOTEWORTHY We show a key role for the fat mass obesity (FTO) gene in regulating smooth muscle contractility, possibly by methylation of serum response factor (Srf).

Single-Cell RNA-Seq Reveals a Population of Smooth Muscle Cells Responsible for Atherogenesis

Understanding the regional propensity differences of atherosclerosis (AS) development is hindered by the lack of animal models suitable for the study of the disease process. In this paper, we used 3S-ASCVD dogs, an ideal large animal human-like models for AS, to interrogate the heterogeneity of AS-prone and AS-resistant arteries; and at the single-cell level, identify the dominant cells involved in AS development. Here we present data from 3S-ASCVD dogs which reliably mimic human AS pathophysiology, predilection for lesion sites, and endpoint events. Our analysis combined bulk RNA-seq with single-cell RNA-seq to depict the transcriptomic profiles and cellular atlas of AS-prone and AS-resistant arteries in 3S-ASCVD dogs. Our results revealed the integral role of smooth muscle cells (SMCs) in regional propensity for AS. Notably, TNC+ SMCs were major contributors to AS development in 3S-ASCVD dogs, indicating enhanced extracellular matrix remodeling and transition to myofibroblasts during the AS process. Moreover, TNC+ SMCs were also present in human AS-prone carotid plaques, suggesting a potential origin of myofibroblasts and supporting the relevance of our findings. Our study provides a promising large animal model for pre-clinical studies of ASCVD and add novel insights surrounding the regional propensity of AS development in humans, which may lead to interventions that delay or prevent lesion progression and adverse clinical events.

Extracellular Matrix Profiling and Disease Modelling in Engineered Vascular Smooth Muscle Cell Tissues

Aortic smooth muscle cells (SMCs) have an intrinsic role in regulating vessel homeostasis and pathological remodelling. In two-dimensional (2D) cell culture formats, however, SMCs are not embedded in their physiological extracellular matrix (ECM) environment. To overcome the limitations of conventional 2D SMC cultures, we established a 3D in vitro model of engineered vascular smooth muscle cell tissues (EVTs). EVTs were casted from primary murine aortic SMCs by suspending a SMC-fibrin master mix between two flexible silicon-posts at day 0 before prolonged culture up to 14 days. Immunohistochemical analysis of EVT longitudinal sections demonstrated that SMCs were aligned, viable and secretory. Mass spectrometry-based proteomics analysis of murine EVT lysates was performed and identified 135 matrisome proteins. Proteoglycans, including the large aggregating proteoglycan versican, accumulated within EVTs by day 7 of culture. This was followed by the deposition of collagens, elastin-binding proteins and matrix regulators up to day 14 of culture. In contrast to 2D SMC controls, accumulation of versican occurred in parallel to an increase in versikine, a cleavage product mediated by proteases of the A Disintegrin and Metalloproteinase with Thrombospondin motifs (ADAMTS) family. Next, we tested the response of EVTs to stimulation with transforming growth factor beta-1 (TGFβ-1). EVTs contracted in response to TGFβ-1 stimulation with altered ECM composition. In contrast, treatment with the pharmacological activin-like kinase inhibitor (ALKi) SB 431542 suppressed ECM secretion. As a disease stimulus, we performed calcification assays. The ECM acts as a nidus for calcium phosphate deposition in the arterial wall. We compared the onset and extent of calcification in EVTs and 2D SMCs cultured under high calcium and phosphate conditions for 7 days. Calcified EVTs displayed increased tissue stiffness by up to 30 % compared to non-calcified controls. Unlike the rapid calcification of SMCs in 2D cultures, EVTs sustained expression of the calcification inhibitor matrix Gla protein and allowed for better discrimination of the calcification propensity between independent biological replicates. In summary, EVTs are an intuitive and versatile model to investigate ECM synthesis and turnover by SMCs in a 3D environment. Unlike conventional 2D cultures, EVTs provide a more relevant pathophysiological model for retention of the nascent ECM produced by SMCs.

Macrophages regulate vascular smooth muscle cell function during atherosclerosis progression through IL-1β/STAT3 signaling

Vascular smooth muscle cells (VSMCs) play a central role in atherosclerosis progression, but the functional changes in VSMCs and the associated cellular crosstalk during atherosclerosis progression remain unknown. Here we show that scRNA-seq analysis of proximal adjacent (PA) and atherosclerotic core (AC) regions of human carotid artery plaques identifies functional alterations in macrophage-like VSMCs, elucidating the main state differences between PA and AC VSMCs. And, IL-1β mediates macrophage-macrophage-like VSMC crosstalk through regulating key transcription factors involved in macrophage-like VSMCs functional alterations during atherosclerosis progression. In vitro assays reveal VSMCs trans-differentiated into a macrophage-like phenotype and then functional alterations in response to macrophage-derived stimuli. IL-1β promots the adhesion, inflammation, and apoptosis of macrophage-like VSMCs in a STAT3 dependent manner. The current findings provide interesting insight into the macrophages-macrophage-like VSMC crosstalk, which would drive functional alterations in the latter cell type through IL-1β/STAT3 axis during atherosclerosis progression.

The Role of Hydrogen Sulfide in Plaque Stability

Atherosclerosis is the greatest contributor to cardiovascular events and is involved in the majority of deaths worldwide. Plaque rapture or erosion precipitates life-threatening thrombi, resulting in the obstruction blood flow to the heart (acute coronary syndrome), brain (ischemic stroke) or low extremities (peripheral vascular diseases). Among these events, major causation dues to the plaque rupture. Although the initiation, procession, and precise time of controlling plaque rupture are unclear, foam cell formation and apoptosis, cell death, extracellular matrix components, protease expression and activity, local inflammation, intraplaque hemorrhage, and calcification contribute to the plaque instability. These alterations tightly associate with the function regulation of intraplaque various cell populations. Hydrogen sulfide (H₂S) is gasotransmitter derived from methionine metabolism and exerts a protective role in the genesis of atherosclerosis. Recent progress also showed H₂S mediated the plaque stability. In this review, we discuss the progress of endogenous H₂S modulation on functions of vascular smooth muscle cells, monocytes/macrophages, and T cells, and the molecular mechanism in plaque stability.

How vascular smooth muscle cell phenotype switching contributes to vascular disease

Vascular smooth muscle cells (VSMCs) are the most abundant cell in vessels. Earlier experiments have found that VSMCs possess high plasticity. Vascular injury stimulates VSMCs to switch into a dedifferentiated type, also known as synthetic VSMCs, with a high migration and proliferation capacity for repairing vascular injury. In recent years, largely owing to rapid technological advances in single-cell sequencing and cell-lineage tracing techniques, multiple VSMCs phenotypes have been uncovered in vascular aging, atherosclerosis (AS), aortic aneurysm (AA), etc. These VSMCs all down-regulate contractile proteins such as α-SMA and calponin1, and obtain specific markers and similar cellular functions of osteoblast, fibroblast, macrophage, and mesenchymal cells. This highly plastic phenotype transformation is regulated by a complex network consisting of circulating plasma substances, transcription factors, growth factors, inflammatory factors, non-coding RNAs, integrin family, and Notch pathway. This review focuses on phenotypic characteristics, molecular profile and the functional role of VSMCs phenotype landscape; the molecular mechanism regulating VSMCs phenotype switching; and the contribution of VSMCs phenotype switching to vascular aging, AS, and AA. Video Abstract.

Macrophage-, Dendritic-, Smooth Muscle-, Endothelium-, and Stem Cells-Derived Foam Cells in Atherosclerosis

Atherosclerosis is an inflammatory disease depending on the buildup, called plaque, of lipoproteins, cholesterol, extracellular matrix elements, and various types of immune and non-immune cells on the artery walls. Plaque development and growth lead to the narrowing of the blood vessel lumen, blocking blood flow, and eventually may lead to plaque burst and a blood clot. The prominent cellular components of atherosclerotic plaque are the foam cells, which, by trying to remove lipoprotein and cholesterol surplus, also participate in plaque development and rupture. Although the common knowledge is that the foam cells derive from macrophages, studies of the last decade clearly showed that macrophages are not the only cells able to form foam cells in atherosclerotic plaque. These findings give a new perspective on atherosclerotic plaque formation and composition and define new targets for anti-foam cell therapies for atherosclerosis prevention. This review gives a concise description of foam cells of different pedigrees and describes the main mechanisms participating in their formation and function.

Lycopene Scavenges Cellular ROS, Modulates Autophagy and Improves Survival through 7SK snRNA Interaction in Smooth Muscle Cells

The chance of survival rate and autophagy of smooth muscle cells under calcium stress were drastically improved with a prolonged inclusion of Lycopene in the media. The results showed an improved viability from 41% to 69% and a reduction in overall autophagic bodies from 7% to 3%, which was well in agreement with the LC3II and III mRNA levels. However, the proliferation was slow compared to the controls. The fall in the major inflammatory marker TNF-α and improved antioxidant enzyme GPx were regarded as significant restoration markers of cell survival. The reactive oxygen species (ROS) were reduced from 8 fold to 3 fold post addition of lycopene for 24 h. Further, the docking studies revealed binding of lycopene molecules with 7SK snRNA at 7.6 kcal/mol docking energy with 300 ns stability under physiological conditions. Together, these results suggest that Lycopene administration during ischemic heart disease might improve the functions of the smooth muscle cells and 7SK snRNA might be involved in the binding of lycopene and its antioxidant protective effects.

Global trends and Frontier topics about vascular smooth muscle cells phenotype switch: A bibliometric analysis from 1999 to 2021

Objective: Vascular smooth muscle cell phenotype switch (VSMCPS) plays a significant role in vascular remodeling. This study aimed to conduct a bibliometric analysis and visualize the knowledge map of research on VSMCPS. Methods: We retrieved publications focusing on VSMCPS from the Web of Science Core Collection database (SCI-EXPANDED) from 1999 to 2021. Using bibliometric tools, VOSviewer and CiteSpace, we identified the most productive researchers, journals, institutions, and countries. At the same time, the trends, hot topics, and knowledge networks were analyzed and visualized. Results: A total of 2213 publications were included in this analysis. The number of annual publications in the VSMCPS field exhibited an upward trend and could be roughly divided into three phases. Until 2006, the most prolific authors were from the United States. As of 2008, the number of articles published in China increased dramatically to reach 126 papers in 2020. As of 2014, China was the most productive country in this field. The United States ranked first in the number of highly-influential authors, institutions, and literature from 1999 to 2022. Owens GK, Hata, Akiko, and Wen, jin-kun were the most prolific authors. Arteriosclerosis Thrombosis and Vascular Biology, Circulation Research, and Cardiovascular Research were the top-ranked journals in this field. "Vascular remodeling," "atherosclerosis," "neointima," "hypertension", and "inflammation" were the main researched topics. New diseases, new mechanisms, and new phenotype (e.g., micro RNA, macrophage-like-cell, hypoxia, autophagy, long noncoding RNA, oxidative stress, endoplasmic reticulum stress, senescence, aging, abdominal aortic aneurysm, and aortic dissection) represent the trending topics in recent years. Conclusion: This study systematically analyzed and visualized the knowledge map of VSMCPS over the past 2 decades. Our findings provide a comprehensive overview for scholars who want to understand current trends and new research frontiers in this area.

Trypanosoma cruzi Infection Promotes Vascular Remodeling and Coexpression of α-Smooth Muscle Actin and Macrophage Markers in Cells of the Aorta

Chagas disease is an emerging global health problem; however, it remains neglected. Increased aortic stiffness (IAS), a predictor of cardiovascular events, has recently been reported in asymptomatic chronic Chagas patients. After vascular injury, smooth muscle cells (SMCs) can undergo alterations associated with phenotypic switch and transdifferentiation, promoting vascular remodeling and IAS. By studying different mouse aortic segments, we tested the hypothesis that Trypanosoma cruzi infection promotes vascular remodeling. Interestingly, the thoracic aorta was the most affected by the infection. Decreased expression of SMC markers and increased expression of proliferative markers were observed in the arteries of acutely infected mice. In acutely and chronically infected mice, we observed cells coexpressing SMC and macrophage (Mo) markers in the media and adventitia layers of the aorta, indicating that T. cruzi might induce cellular processes associated with SMC transdifferentiation into Mo-like cells or vice versa. In the adventitia, the Mo cell functional polarization was associated with an M2-like CD206+arginase-1+ phenotype despite the T. cruzi presence in the tissue. Only Mo-like cells in inflammatory foci were CD206+iNOS+. In addition to the disorganization of elastic fibers, we found thickening of the aortic layers during the acute and chronic phases of the disease. Our findings indicate that T. cruzi infection induces a vascular remodeling with SMC dedifferentiation and increased cell populations coexpressing α-SMA and Mo markers that could be associated with IAS promotion. These data highlight the importance of studying large vessel homeostasis in Chagas disease.

Phosphorylation of the smooth muscle master splicing regulator RBPMS regulates its splicing activity

We previously identified RBPMS as a master regulator of alternative splicing in differentiated smooth muscle cells (SMCs). RBPMS is transcriptionally downregulated during SMC dedifferentiation, but we hypothesized that RBPMS protein activity might be acutely downregulated by post-translational modifications. Publicly available phosphoproteomic datasets reveal that Thr113 and Thr118 immediately adjacent to the RRM domain are commonly both phosphorylated. An RBPMS T113/118 phosphomimetic T/E mutant showed decreased splicing regulatory activity both in transfected cells and in a cell-free in vitro assay, while a non-phosphorylatable T/A mutant retained full activity. Loss of splicing activity was associated with a modest reduction in RNA affinity but significantly reduced RNA binding in nuclear extract. A lower degree of oligomerization of the T/E mutant might cause lower avidity of multivalent RNA binding. However, NMR analysis also revealed that the T113/118E peptide acts as an RNA mimic which can loop back and antagonize RNA-binding by the RRM domain. Finally, we identified ERK2 as the most likely kinase responsible for phosphorylation at Thr113 and Thr118. Collectively, our data identify a potential mechanism for rapid modulation of the SMC splicing program in response to external signals during the vascular injury response and atherogenesis.

Critical Role of Inflammation and Specialized Pro-Resolving Mediators in the Pathogenesis of Atherosclerosis

Recent research on how the body resolves this inflammation is gaining traction and has shed light on new avenues for future management of cardiovascular diseases. In this narrative review, we discuss the pathophysiological mechanisms of atherosclerosis, the recent development in the understanding of a new class of molecules called Specialized Pro-resolving Mediators (SPMs), and the impact of such findings in the realm of cardiovascular treatment options. We searched the MEDLINE database restricting ourselves to original research articles as much as possible on the complex pathophysiology of atherosclerosis and the role of SPMs. We expect to see further research in translating these findings to bedside clinical trials in treating conditions with a pathophysiological basis of inflammation, such as coronary artery disease, asthma, and periodontal disease.

Exploring the difference in the mechanics of vascular smooth muscle cells from wild-type and apolipoprotein-E knockout mice

Atherosclerosis-related cardiovascular diseases are a leading cause of mortality worldwide. Vascular smooth muscle cells (VSMCs) comprise the medial layer of the arterial wall and undergo phenotypic switching during atherosclerosis to a synthetic phenotype capable of proliferation and migration. The surrounding environment undergoes alterations in extracellular matrix (ECM) stiffness and composition and an increase in cholesterol content. Using an atherosclerotic murine model, we analyzed how the mechanics of VSMCs isolated from Western diet-fed apolipoprotein-E knockout (ApoE-/-) and wild-type (WT) mice were altered during atherosclerosis. Increased stiffness of ApoE-/- VSMCs correlated with a greater degree of stress fiber alignment, as evidenced by atomic force microscopy (AFM)-generated force maps and stress fiber topography images. On type-1 collagen (COL1)-coated polyacrylamide (PA) gels (referred to as substrate) of varying stiffness, ApoE-/- VSMCs had lower adhesion forces to COL1 and N-cadherin (N-Cad) compared with WT cells. ApoE-/- VSMC stiffness was significantly greater than that of WT cells. Cell stiffness increased with increasing substrate stiffness for both ApoE-/- and WT VSMCs. In addition, ApoE-/- VSMCs showed an enhanced migration capability on COL1-coated substrates and a general decreasing trend in migration capacity with increasing substrate stiffness, correlating with lowered adhesion forces as compared with WT VSMCs. Altogether, these results demonstrate the potential contribution of the alteration in VSMC mechanics in the development of atherosclerosis.

Aortic Cellular Diversity and Quantitative Genome-Wide Association Study Trait Prioritization Through Single-Nuclear RNA Sequencing of the Aneurysmal Human Aorta

BACKGROUND

Mural cells in ascending aortic aneurysms undergo phenotypic changes that promote extracellular matrix destruction and structural weakening. To explore this biology, we analyzed the transcriptional features of thoracic aortic tissue.

METHODS

Single-nuclear RNA sequencing was performed on 13 samples from human donors, 6 with thoracic aortic aneurysm, and 7 without aneurysm. Individual transcriptomes were then clustered based on transcriptional profiles. Clusters were used for between-disease differential gene expression analyses, subcluster analysis, and analyzed for intersection with genetic aortic trait data.

RESULTS

We sequenced 71 689 nuclei from human thoracic aortas and identified 14 clusters, aligning with 11 cell types, predominantly vascular smooth muscle cells (VSMCs) consistent with aortic histology. With unbiased methodology, we found 7 vascular smooth muscle cell and 6 fibroblast subclusters. Differentially expressed genes analysis revealed a vascular smooth muscle cell group accounting for the majority of differential gene expression. Fibroblast populations in aneurysm exhibit distinct behavior with almost complete disappearance of quiescent fibroblasts. Differentially expressed genes were used to prioritize genes at aortic diameter and distensibility genome-wide association study loci highlighting the genes JUN, LTBP4 (latent transforming growth factor beta-binding protein 1), and IL34 (interleukin 34) in fibroblasts, ENTPD1, PDLIM5 (PDZ and LIM domain 5), ACTN4 (alpha-actinin-4), and GLRX in vascular smooth muscle cells, as well as LRP1 in macrophage populations.

CONCLUSIONS

Using nuclear RNA sequencing, we describe the cellular diversity of healthy and aneurysmal human ascending aorta. Sporadic aortic aneurysm is characterized by differential gene expression within known cellular classes rather than by the appearance of novel cellular forms. Single-nuclear RNA sequencing of aortic tissue can be used to prioritize genes at aortic trait loci.

Distinct patterns of responses in endothelial cells and smooth muscle cells following vascular injury

Vascular smooth muscle cells (SMCs) are heterogeneous, and their differential responses to vascular injury are not well understood. To address this question, we performed single-cell analysis of vascular cells to a ligation injury in mouse carotid arteries after 3 days. While endothelial cells had a homogeneous activation of mesenchymal genes, less than 30% of SMCs responded to the injury and generated 2 distinct clusters - i.e., proinflammatory SMCs and stress-responsive SMCs. Proinflammatory SMCs were enriched with high levels of inflammatory markers such as vascular cell adhesion molecule-1 while stress-responsive SMCs overexpressed heat shock proteins. Trajectory analysis suggested that proinflammatory SMCs were potentially derived from a specific subpopulation of SMCs. Ligand-receptor pair analysis showed that the interaction between macrophages and proinflammatory SMCs was the major cell-cell communication among all cell types in the injured arteries. In vitro coculture demonstrated that VCAM1+ SMCs had a stronger chemotactic effect on macrophage recruitment than VCAM1- SMCs. Consistently, the number of VCAM1+ SMCs significantly increased in injured arteries and atherosclerotic lesions of ApoE-/- mice and human arteries. These findings provide insights at the single-cell level on the distinct patterns of endothelial cells and SMC responses to vascular injury.

Botanical Antcin K Alleviates High-Fat Damage in Palm Acid Oil-Treated Vascular Endothelial Cells and Macrophages

Lipid metabolism disorder is the most critical risk factor for atherosclerosis, and the process involves lipid deposition in the arterial intima. In Taiwan, antcin K, an active triterpenoid from the fruiting bodies of Antrodia camphorata, has been considered a potential lipid-lowering agent. Despite this, the possible therapeutic mechanisms of antcin K remain unclear. To explore the crucial role of botanical antcin K in reducing atherosclerotic plaque, we used SVEC4-10 vascular endothelial cells and RAW264.7 macrophages with palm acid oil-induced high-fat damage as our cell models. Our results showed through using the DPPH assay that antcin K had excellent free radical scavenging ability. Antcin K treatment can significantly alleviate the high-fat damage and reduce the levels of inflammatory factors of TNF-α and IL-1β in vascular endothelial cells and macrophages, as shown through MTT assay and ELISA. Furthermore, antcin K treatment can effectively enhance migration ability and clear lipid deposition in macrophages, as shown by using cell migration assay and oil red O staining. When stained with immunofluorescence, antcin K was shown to significantly decrease the expression of adhesion molecules of vascular cell adhesion molecule 1 (VCAM-1) in vascular endothelial cells involved in monocyte migration and inflammation. Antcin K not only reduced the expression of the CD36 scavenger receptor but also augmented the expression of Kruppel-like factor 4 (KLF4) transcription factor in macrophages, which inhibits the transformation of macrophages into foam cells underlying the pathological process of atherosclerosis. Taking our findings into account, we suggested that botanical antcin K could have therapeutic potential for the treatment of atherosclerosis.

Dynamic changes in chromatin accessibility are associated with the atherogenic transitioning of vascular smooth muscle cells

AIMS

De-differentiation and activation of pro-inflammatory pathways are key transitions vascular smooth muscle cells (SMCs) make during atherogenesis. Here, we explored the upstream regulators of this 'atherogenic transition'.

METHODS AND RESULTS

Genome-wide sequencing studies, including Assay for Transposase-Accessible Chromatin using sequencing and RNA-seq, were performed on cells isolated from both murine SMC-lineage-tracing models of atherosclerosis and human atherosclerotic lesions. At the bulk level, alterations in chromatin accessibility were associated with the atherogenic transitioning of lesional SMCs, especially in relation to genes that govern differentiation status and complement-dependent inflammation. Using computational biology, we observed that a transcription factor previously related to coronary artery disease, Activating transcription factor 3 (ATF3), was predicted to be an upstream regulator of genes altered during the transition. At the single-cell level, our results indicated that ATF3 is a key repressor of SMC transitioning towards the subset of cells that promote vascular inflammation by activating the complement cascade. The expression of ATF3 and complement component C3 was negatively correlated in SMCs from human atherosclerotic lesions, suggesting translational relevance. Phenome-wide association studies indicated that genetic variation that results in reduced expression of ATF3 is correlated with an increased risk for atherosclerosis, and the expression of ATF3 was significantly down-regulated in humans with advanced vascular disease.

CONCLUSION

Our study indicates that the plasticity of atherosclerotic SMCs may in part be explained by dynamic changes in their chromatin architecture, which in turn may contribute to their maladaptive response to inflammation-induced stress.

Decoding the transcriptome of calcified atherosclerotic plaque at single-cell resolution

Atherogenesis involves an interplay of inflammation, tissue remodeling and cellular transdifferentiation (CTD), making it especially difficult to precisely delineate its pathophysiology. Here we use single-cell RNA sequencing and systems-biology approaches to analyze the transcriptional profiles of vascular smooth muscle cells (VSMCs) and endothelial cells (ECs) in calcified atherosclerotic core (AC) plaques and patient-matched proximal adjacent (PA) portions of carotid artery tissue from patients undergoing carotid endarterectomy. Our results reveal an anatomic distinction whereby PA cells express inflammatory mediators, while cells expressing matrix-secreting genes occupy a majority of the AC region. Systems biology analysis indicates that inflammation in PA ECs and VSMCs may be driven by TNFa signaling. Furthermore, we identify POSTN, SPP1 and IBSP in AC VSMCs, and ITLN1, SCX and S100A4 in AC ECs as possible candidate drivers of CTD in the atherosclerotic core. These results establish an anatomic framework for atherogenesis which forms the basis for exploration of a site-specific strategy for disruption of disease progression.

Single-cell RNA sequencing and systems biology are used to profile the human vascular cell populations in calcified atherosclerotic core plaques from carotid endarterectomy samples, showing an anatomic distinction between gene expression of inflammatory versus matrix-secreting factors.

Identification of immune cell infiltration and diagnostic biomarkers in unstable atherosclerotic plaques by integrated bioinformatics analysis and machine learning

Objective

The decreased stability of atherosclerotic plaques increases the risk of ischemic stroke. However, the specific characteristics of dysregulated immune cells and effective diagnostic biomarkers associated with stability in atherosclerotic plaques are poorly characterized. This research aims to investigate the role of immune cells and explore diagnostic biomarkers in the formation of unstable plaques for the sake of gaining new insights into the underlying molecular mechanisms and providing new perspectives for disease detection and therapy.

Method

Using the CIBERSORT method, 22 types of immune cells between stable and unstable carotid atherosclerotic plaques from RNA-sequencing and microarray data in the public GEO database were quantitated. Differentially expressed genes (DEGs) were further calculated and were analyzed for enrichment of GO Biological Process and KEGG pathways. Important cell types and hub genes were screened using machine learning methods including least absolute shrinkage and selection operator (LASSO) regression and random forest. Single-cell RNA sequencing and clinical samples were further used to validate critical cell types and hub genes. Finally, the DGIdb database of gene–drug interaction data was utilized to find possible therapeutic medicines and show how pharmaceuticals, genes, and immune cells interacted.

Results

A significant difference in immune cell infiltration was observed between unstable and stable plaques. The proportions of M0, M1, and M2 macrophages were significantly higher and that of CD8⁺ T cells and NK cells were significantly lower in unstable plaques than that in stable plaques. With respect to DEGs, antigen presentation genes (CD74, B2M, and HLA-DRA), inflammation-related genes (MMP9, CTSL, and IFI30), and fatty acid-binding proteins (CD36 and APOE) were elevated in unstable plaques, while the expression of smooth muscle contraction genes (TAGLN, ACAT2, MYH10, and MYH11) was decreased in unstable plaques. M1 macrophages had the highest instability score and contributed to atherosclerotic plaque instability. CD68, PAM, and IGFBP6 genes were identified as the effective diagnostic markers of unstable plaques, which were validated by validation datasets and clinical samples. In addition, insulin, nivolumab, indomethacin, and α-mangostin were predicted to be potential therapeutic agents for unstable plaques.

Conclusion

M1 macrophages is an important cause of unstable plaque formation, and CD68, PAM, and IGFBP6 could be used as diagnostic markers to identify unstable plaques effectively.

The adventitia in arterial development, remodeling, and hypertension

The adventitia receives input signals from the vessel wall, the immune system, perivascular nerves and from surrounding tissues to generate effector responses that regulate structural and mechanical properties of blood vessels. It is a complex and dynamic tissue that orchestrates multiple functions for vascular development, homeostasis, repair, and disease. The purpose of this review is to highlight recent advances in our understanding of the origins, phenotypes, and functions of adventitial and perivascular cells with particular emphasis on hypertensive vascular remodeling.

Lysosomal acid lipase deficiency: A rare inherited dyslipidemia but potential ubiquitous factor in the development of atherosclerosis and fatty liver disease

Lysosomal acid lipase (LAL), encoded by the gene LIPA, is the sole neutral lipid hydrolase in lysosomes, responsible for cleavage of cholesteryl esters and triglycerides into their component parts. Inherited forms of complete (Wolman Disease, WD) or partial LAL deficiency (cholesteryl ester storage disease, CESD) are fortunately rare. Recently, LAL has been identified as a cardiovascular risk gene in genome-wide association studies, though the directionality of risk conferred remains controversial. It has also been proposed that the low expression and activity of LAL in arterial smooth muscle cells (SMCs) that occurs inherently in nature is a likely determinant of the propensity of SMCs to form the majority of foam cells in atherosclerotic plaque. LAL also likely plays a potential role in fatty liver disease. This review highlights the nature of LAL gene mutations in WD and CESD, the association of LAL with prediction of cardiovascular risk from genome-wide association studies, the importance of relative LAL deficiency in SMC foam cells, and the need to further interrogate the pathophysiological impact and cell type-specific role of enhancing LAL activity as a novel treatment strategy to reduce the development and induce the regression of ischemic cardiovascular disease and fatty liver.

Vascular homeostasis in atherosclerosis: A holistic overview

Atherosclerosis refers to the deposition of lipids and the co-existence of inflammation and impaired inflammation resolution in pan-vasculature, which causes lumen narrowing, hardening, plaque formation, and the manifestation of acute cardiovascular events. Emerging evidence has suggested that vascular circulation can be viewed as a complex homeostatic system analogous to a mini-ecosystem which consists of the vascular microenvironment (niche) and the crosstalk among phenotypically and functionally diverse vascular cell types. Here, we elucidate how cell components in the vascular wall affect vascular homeostasis, structure, function, and atherosclerosis in a holistic perspective. Finally, we discuss the potential role of vascular-stabilizing strategies including pharmacotherapies, natural substances and lifestyle modifications, in preventing cardiovascular diseases by preserving vascular integrity and homeostasis.

Protein Tyrosine Phosphatase 1B Deficiency in Vascular Smooth Muscle Cells Promotes Perivascular Fibrosis following Arterial Injury

Background  Smooth muscle cell (SMC) phenotype switching plays a central role during vascular remodeling. Growth factor receptors are negatively regulated by protein tyrosine phosphatases (PTPs), including its prototype PTP1B. Here, we examine how reduction of PTP1B in SMCs affects the vascular remodeling response to injury.

Methods  Mice with inducible PTP1B deletion in SMCs (SMC.PTP1B-KO) were generated by crossing mice expressing Cre.ER ^T2 recombinase under the Myh11 promoter with PTP1B ^flox/flox mice and subjected to FeCl ₃ carotid artery injury.

Results  Genetic deletion of PTP1B in SMCs resulted in adventitia enlargement, perivascular SMA ⁺ and PDGFRβ ⁺ myofibroblast expansion, and collagen accumulation following vascular injury. Lineage tracing confirmed the appearance of Myh11 -Cre reporter cells in the remodeling adventitia, and SCA1 ⁺ CD45 ^- vascular progenitor cells increased. Elevated mRNA expression of transforming growth factor β (TGFβ) signaling components or enzymes involved in extracellular matrix remodeling and TGFβ liberation was seen in injured SMC.PTP1B-KO mouse carotid arteries, and mRNA transcript levels of contractile SMC marker genes were reduced already at baseline. Mechanistically, Cre recombinase (mice) or siRNA (cells)-mediated downregulation of PTP1B or inhibition of ERK1/2 signaling in SMCs resulted in nuclear accumulation of KLF4, a central transcriptional repressor of SMC differentiation, whereas phosphorylation and nuclear translocation of SMAD2 and SMAD3 were reduced. SMAD2 siRNA transfection increased protein levels of PDGFRβ and MYH10 while reducing ERK1/2 phosphorylation, thus phenocopying genetic PTP1B deletion.

Conclusion  Chronic reduction of PTP1B in SMCs promotes dedifferentiation, perivascular fibrosis, and adverse remodeling following vascular injury by mechanisms involving an ERK1/2 phosphorylation-driven shift from SMAD2 to KLF4-regulated gene transcription.

BMAL1 modulates smooth muscle cells phenotypic switch towards fibroblast-like cells and stabilizes atherosclerotic plaques by upregulating YAP1

BACKGROUND

Ischemic heart diseases and ischemic stroke are closely related to circadian clock and unstable atherosclerotic plaques. Vascular smooth muscle cells (VSMCs) can stabilize or destabilize an atherosclerotic lesion through phenotypic switch. BMAL1 is not only an indispensable core component in circadian clock but also an important regulator in atherosclerosis and VSMCs proliferation. However, little is known about the modulation mechanisms of BMAL1 in VSMCs phenotypic switch and atherosclerotic plaque stability.

METHODS

We integrated histological analysis of human plaques, in vivo experiments of VSMC-specific Bmal1-/- mice, in vitro experiments, and gene set enrichment analysis (GSEA) of public datasets of human plaques to explore the function of BMAL1 in VSMCs phonotypic switch and plaque stability.

FINDINGS

Comparing to human unstable plaques, BMAL1 was higher in stable plaques, accompanied by elevated YAP1 and fibroblast maker FSP1 which were positively correlated with BMAL1. In response to Methyl-β-cyclodextrin-cholesterol, oxidized-low-density-lipoprotein and platelet-derived-growth-factor-BB, VSMCs embarked on phenotypic switch and upregulated BMAL, YAP1 and FSP1. Besides, BMAL1 overexpression promoted VSMCs phonotypic switch towards fibroblast-like cells by transcriptionally upregulating the expression of YAP1. BMAL1 or YAP1 knock-down inhibited VSMCs phonotypic switch and downregulated FSP1. Furthermore, VSMC-specific Bmal1-/- mice exhibited VSMCs with lower YAP1 and FSP1 levels, and more vulnerable plaques with less collagen content. In addition, BMAL1 suppressed the migration of VSMCs. The GSEA results of public datasets were consistent with our laboratory findings.

INTERPRETATION

Our results highlight the importance of BMAL1 as a major regulator in VSMCs phenotypic switch towards fibroblast-like cells which stabilize an atherosclerotic plaque.

Global research trends in atherosclerosis: A bibliometric and visualized study

Background

Increasing evidence has spurred a considerable evolution of concepts related to atherosclerosis, prompting the need to provide a comprehensive view of the growing literature. By retrieving publications in the Web of Science Core Collection (WoSCC) of Clarivate Analytics, we conducted a bibliometric analysis of the scientific literature on atherosclerosis to describe the research landscape.

Methods

A search was conducted of the WoSCC for articles and reviews serving exclusively as a source of information on atherosclerosis published between 2012 and 2022. Microsoft Excel 2019 was used to chart the annual productivity of research relevant to atherosclerosis. Through CiteSpace and VOSviewer, the most prolific countries or regions, authors, journals, and resource-, intellectual-, and knowledge-sharing in atherosclerosis research, as well as co-citation analysis of references and keywords, were analyzed.

Results

A total of 20,014 publications were retrieved. In terms of publications, the United States remains the most productive country (6,390, 31,93%). The most publications have been contributed by Johns Hopkins Univ (730, 3.65%). ALVARO ALONSO produced the most published works (171, 0.85%). With a betweenness centrality of 0.17, ERIN D MICHOS was the most influential author. The most prolific journal was identified as Atherosclerosis (893, 4.46%). Circulation received the most co-citations (14,939, 2.79%). Keywords with the ongoing strong citation bursts were “nucleotide-binding oligomerization (NOD), Leucine-rich repeat (LRR)-containing protein (NLRP3) inflammasome,” “short-chain fatty acids (SCFAs),” “exosome,” and “homeostasis,” etc.

Conclusion

The research on atherosclerosis is driven mostly by North America and Europe. Intensive research has focused on the link between inflammation and atherosclerosis, as well as its complications. Specifically, the NLRP3 inflammasome, interleukin-1β, gut microbiota and SCFAs, exosome, long non-coding RNAs, autophagy, and cellular senescence were described to be hot issues in the field.

Understanding the role of alternative macrophage phenotypes in human atherosclerosis

INTRODUCTION

Atherosclerosis-based ischemic heart disease is still the primary cause of death throughout the world. Over the past decades there has been no significant changes in the therapeutic approaches to atherosclerosis, which are mainly based on lipid lowering therapies and management of comorbid conditions such as diabetes and hypertension. The involvement of macrophages in atherosclerosis has been recognized for decades. More recently, a more detailed and sophisticated understanding of their various phenotypes and roles in the atherosclerotic process has been recognized. This new data is revealing how specific subtypes of macrophage-induced inflammation may have distinct effects on atherosclerosis progression and may provide new approaches for treatment, based upon targeting of specific macrophage subtypes.

AREAS COVERED

We will comprehensively review the spectrum of macrophage phenotypes and how they contribute to atherosclerotic plaque development and progression.

EXPERT OPINION

Various signals derived from atherosclerotic lesions drive macrophages into complex subsets with different gene expression profiles, phenotypes, and functions, not all of which are understood. Macrophage phenotypes include those that enhance, heal, and regress the atherosclerotic lesions though various mechanisms. Targeting of specific macrophage phenotypes may provide a promising and novel approach to prevent atherosclerosis progression.

New insights into macrophage subsets in atherosclerosis

Macrophages in atherosclerotic patients are notably plastic and heterogeneous. Single-cell RNA sequencing (Sc RNA-seq) can provide information about all the RNAs in individual cells, and it is used to identify cell subpopulations in atherosclerosis (AS) and reveal the heterogeneity of these cells. Recently, some findings from Sc RNA-seq experiments have suggested the existence of multiple macrophage subsets in atherosclerotic plaque lesions, and these subsets exhibit significant differences in their gene expression levels and functions. These cells affect various aspects of plaque lesion development, stabilization, and regression, as well as plaque rupture. This article aims to review the content and results of current studies that used RNA-seq to explore the different types of macrophages in AS and the related molecular mechanisms as well as to identify the potential roles of these macrophage types in the pathogenesis of atherosclerotic plaques. Also, this review listed some new therapeutic targets for delaying atherosclerotic lesion progression and treatment based on the experimental results.

Integrating multiplex immunofluorescent and mass spectrometry imaging to map myeloid heterogeneity in its metabolic and cellular context

Cells often adopt different phenotypes, dictated by tissue-specific or local signals such as cell-cell and cell-matrix contacts or molecular micro-environment. This holds in extremis for macrophages with their high phenotypic plasticity. Their broad range of functions, some even opposing, reflects their heterogeneity, and a multitude of subsets has been described in different tissues and diseases. Such micro-environmental imprint cannot be adequately studied by single-cell applications, as cells are detached from their context, while histology-based assessment lacks the phenotypic depth due to limitations in marker combination. Here, we present a novel, integrative approach in which 15-color multispectral imaging allows comprehensive cell classification based on multi-marker expression patterns, followed by downstream analysis pipelines to link their phenotypes to contextual, micro-environmental cues, such as their cellular ("community") and metabolic ("local lipidome") niches in complex tissue. The power of this approach is illustrated for myeloid subsets and associated lipid signatures in murine atherosclerotic plaque.

Preventing Cholesterol-Induced Perk (Protein Kinase RNA-Like Endoplasmic Reticulum Kinase) Signaling in Smooth Muscle Cells Blocks Atherosclerotic Plaque Formation

BACKGROUND

Vascular smooth muscle cells (SMCs) undergo complex phenotypic modulation with atherosclerotic plaque formation in hyperlipidemic mice, which is characterized by de-differentiation and heterogeneous increases in the expression of macrophage, fibroblast, osteogenic, and stem cell markers. An increase of cellular cholesterol in SMCs triggers similar phenotypic changes in vitro with exposure to free cholesterol due to cholesterol entering the endoplasmic reticulum, triggering endoplasmic reticulum stress and activating Perk (protein kinase RNA-like endoplasmic reticulum kinase) signaling.

METHODS

We generated an SMC-specific Perk knockout mouse model, induced hyperlipidemia in the mice by AAV-PCSK9DY injection, and subjected them to a high-fat diet. We then assessed atherosclerotic plaque formation and performed single-cell transcriptomic studies using aortic tissue from these mice.

RESULTS

SMC-specific deletion of Perk reduces atherosclerotic plaque formation in male hyperlipidemic mice by 80%. Single-cell transcriptomic data identify 2 clusters of modulated SMCs in hyperlipidemic mice, one of which is absent when Perk is deleted in SMCs. The 2 modulated SMC clusters have significant overlap of transcriptional changes, but the Perk-dependent cluster uniquely shows a global decrease in the number of transcripts. SMC-specific Perk deletion also prevents migration of both contractile and modulated SMCs from the medial layer of the aorta.

CONCLUSIONS

Our results indicate that hypercholesterolemia drives both Perk-dependent and Perk-independent SMC modulation and that deficiency of Perk significantly blocks atherosclerotic plaque formation.

Dichotomous Roles of Smooth Muscle Cell-Derived MCP1 (Monocyte Chemoattractant Protein 1) in Development of Atherosclerosis

BACKGROUND

Smooth muscle cells (SMCs) in atherosclerotic plaque take on multiple nonclassical phenotypes that may affect plaque stability and, therefore, the likelihood of myocardial infarction or stroke. However, the mechanisms by which these cells affect stability are only beginning to be explored.

METHODS

In this study, we investigated the contribution of inflammatory MCP1 (monocyte chemoattractant protein 1) produced by both classical Myh11 (myosin heavy chain 11)⁺ SMCs and SMCs that have transitioned through an Lgals3 (galectin 3)⁺ state in atherosclerosis using smooth muscle lineage tracing mice that label all Myh11⁺ cells and a dual lineage tracing system that targets Lgals3-transitioned SMC only.

RESULTS

We show that loss of MCP1 in all Myh11⁺ smooth muscle results in a paradoxical increase in plaque size and macrophage content, driven by a baseline systemic monocytosis early in atherosclerosis pathogenesis. In contrast, knockout of MCP1 in Lgals3-transitioned SMCs using a complex dual lineage tracing system resulted in lesions with an increased Acta2 (actin alpha 2, smooth muscle)⁺ fibrous cap and decreased investment of Lgals3-transitioned SMCs, consistent with increased plaque stability. Finally, using flow cytometry and single-cell RNA sequencing, we show that MCP1 produced by Lgals3-transitioned SMCs influences multiple populations of inflammatory cells in late-stage plaques.

CONCLUSIONS

MCP1 produced by classical SMCs influences monocyte levels beginning early in disease and was atheroprotective, while MCP1 produced by the Lgals3-transitioned subset of SMCs exacerbated plaque pathogenesis in late-stage disease. Results are the first to determine the function of Lgals3-transitioned inflammatory SMCs in atherosclerosis and highlight the need for caution when considering therapeutic interventions involving MCP1.

Sphingosine 1-phosphate receptor 2 promotes erythrocyte clearance by vascular smooth muscle cells in intraplaque hemorrhage through MFG-E8 production

Intraplaque hemorrhage (IPH) accelerates atherosclerosis progression. To scavenge excessive red blood cells (RBCs), vascular smooth muscle cells (VSMCs) with great plasticity may function as phagocytes. Here, we investigated the erythrophagocytosis function of VSMCs and possible regulations involved. Based on transcriptional microarray analysis, Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis showed that genes up-regulated in human carotid atheroma with IPH were enriched in functions of phagocytic activities, while those down-regulated were enriched in VSMCs contraction function. Transcriptional expression of Milk fat globule-epidermal growth factor 8 (MFG-E8) was also down-regulated in atheroma with IPH. In high-fat diet-fed apolipoprotein E-deficient mice, erythrocytes were present in cells expressing VSMC markers αSMA in the brachiocephalic artery, suggesting VSMCs play a role in erythrophagocytosis. Using immunofluorescence and flow cytometry, we also found that eryptotic RBCs were bound to and internalized by VSMCs in a phosphatidylserine/MFG-E8/integrin α_Vβ₃ dependent manner in vitro. Inhibiting S1PR2 signaling with specific inhibitor JTE-013 or siRNA decreased Mfge8 expression and impaired the erythrophagocytosis of VSMCs in vitro. Partial ligation was performed in the left common carotid artery (LCA) followed by intra-intimal injection of isolated erythrocytes to observe their clearance in vivo. Interfering S1PR2 expression in VSMCs with Adeno-associated virus 9 inhibited MFG-E8 expression inside LCA plaques receiving RBCs injection and attenuated erythrocytes clearance. Erythrophagocytosis by VSMCs increased vascular endothelial growth factor-a secretion and promoted angiogenesis. The present study revealed that VSMCs act as phagocytes for RBC clearance through S1PR2 activation induced MFG-E8 release.

Transcriptional regulation of vascular smooth muscle cell proliferation, differentiation and senescence: Novel targets for therapy

Vascular smooth muscle cells (SMC) possess a unique cytoplasticity, regulated by transcriptional, translational and phenotypic transformation in response to a diverse range of extrinsic and intrinsic pathogenic factors. The mature, differentiated SMC phenotype is physiologically typified transcriptionally by expression of genes encoding "contractile" proteins, such as SMα-actin (ACTA2), SM-MHC (myosin-11) and SM22α (transgelin). When exposed to various pathological conditions (e.g., pro-atherogenic risk factors, hypertension), SMC undergo phenotypic modulation, a bioprocess enabling SMC to de-differentiate in immature stages or trans-differentiate into other cell phenotypes. As recent studies suggest, the process of SMC phenotypic transformation involves five distinct states characterized by different patterns of cell growth, differentiation, migration, matrix protein expression and declined contractility. These changes are mediated via the action of several transcriptional regulators, including myocardin and serum response factor. Conversely, other factors, including Kruppel-like factor 4 and nuclear factor-κB, can inhibit SMC differentiation and growth arrest, while factors such as yin yang-1, can promote SMC differentiation whilst inhibiting proliferation. This article reviews recent advances in our understanding of regulatory mechanisms governing SMC phenotypic modulation. We propose the concept that transcription factors mediating this switching are important biomarkers and potential pharmacological targets for therapeutic intervention in cardiovascular disease.

Phenotypic modulation of vascular smooth muscle cells in the corpus spongiosum surrounding the urethral plate in hypospadias

Hypospadias is an abnormal ventral development of the penis caused by incomplete virilization of the male genital tubercle. This study investigated the phenotypic modulation of vascular smooth muscle cells (VSMCs) in the corpus spongiosum surrounding the urethral plate in hypospadias. The urethral corpus spongiosum tissue was collected for HE, Masson and α-SMA immunohistochemical staining. Spongiosum VSMCs were cultured and identified by α-SMA fluorescence. qRT-PCR and Western blotting and fluorescence were performed. The results showed that the vascular lumen of the corpus spongiosum around the urethral plate was larger and that the vascular smooth muscle layer was thicker in hypospadias. The expression of the contractile markers α-SMA and Calponin 1 in VSMCs was decreased, the expression of the synthetic marker OPN was increased, and the transcription of the phenotypic switching factors SRF and MYOCD was decreased. The expression of Ki67, PCNA and BAX was increased, and the expression of Bcl-2 was decreased. The phenotype of corpus spongiosum VSMCs in hypospadias changed from the contractional type to the synthetic type. This phenotypic modulation was associated with increased proliferation and apoptosis rates. SRF and MYOCD may be the main factors mediating the phenotypic modulation of urethral corpus spongiosum VSMCs.

ATF4 promotes brain vascular smooth muscle cells proliferation, invasion and migration by targeting miR-552-SKI axis

Background

Studies have indicated vascular smooth muscle cells (VSMCs) played a crucial role in atherosclerosis and microRNAs (miRNAs) played key roles in biological functions of VSMCs. Whereas, the potential function and mechanism of miR-552 in VSMCs remains unclear. Our aim was to explore the role of miR-552 on VSMCs and underlying mechanism.

Material/Methods

MTT assay and transwell assay were used to measure the proliferation, invasion, and migration of human brain VSMCs (HBVSMCs) and mice VSMCs (mVSMCs), respectively. Bioinformatics tools and luciferase assay were adopted to verify the association between miR-552 and SKI. Rescue experiments were employed to assess the interaction of miR-552 and SKI in modulating biological functions in HBVSMCs and mVSMCs. The expression level of transcription factors (TFs)was measured via qRT-PCR assay. The effect of ATF4 on miR-552 and SKI expression was tested by qRT-PCR or western blot assay. Finally, chromatin immunoprecipitation (ChIP) assay and JASPAR databases were used to analyze the regulatory linkage between ATF4 and miR-552.

Results

We found that miR-552 was upregulated in HBVSMCs treated with PDGF-bb and miR-552 overexpression could promote proliferation, invasion, and migration of HBVSMCs and mVSMCs, whereas, miR-552 knockdown had the opposite impact. In addition, we also found that SKI was a direct target of miR-552, which reversed miR-552-mediated proliferation, invasion, and migration in HBVSMCs and mVSMCs. Furthermore, we also discovered that miR-552 overexpression promoted the effects of ATF4 elevation on proliferation, migration and invasion of HBVSMCs and mVSMCs, but, miR-552 decline had the opposite impact.

Conclusions

ATF4-miR-552-SKI axis played critical roles in the proliferation and migration of HBVSMCs and mVSMCs, which were closely involved in atherosclerosis (AS). Therefore, our findings might offer a novel therapeutic target for AS.

Extracellular vesicles carrying proinflammatory factors may spread atherosclerosis to remote locations

Most cells involved in atherosclerosis release extracellular vesicles (EVs), which can carry bioactive substances to downstream tissues via circulation. We hypothesized that EVs derived from atherosclerotic plaques could promote atherogenesis in remote locations, a mechanism that mimics the blood metastasis of cancer. Ldlr gene knockout (Ldlr KO) rats were fed on a high cholesterol diet and underwent partial carotid ligation to induce local atherosclerosis. EVs were separated from carotid artery tissues and downstream blood of carotid ligation by centrifugation. MiRNA sequencing and qPCR were then performed to detect miRNA differences in EVs from rats with and without induced carotid atherosclerosis. Biochemical analyses demonstrated that EVs derived from atherosclerosis could increase the expression of ICAM-1, VCAM-1, and E-selectin in endothelial cells in vitro. EVs derived from atherosclerosis contained a higher level of miR-23a-3p than those derived from controls. MiR-23a-3p could promote endothelial inflammation by targeting Dusp5 and maintaining ERK1/2 phosphorylation in vitro. Inhibiting EV release could attenuate atherogenesis and reduce macrophage infiltration in vivo. Intravenously administrating atherosclerotic plaque-derived EVs could induce intimal inflammation, arterial wall thickening and lumen narrowing in the carotids of Ldlr KO rats, while simultaneous injection of miR-23a-3p antagomir could reverse this reaction. The results suggested that EVs may transfer atherosclerosis to remote locations by carrying proinflammatory factors, particularly miR-23a-3p.

New Insights into Cerebral Vessel Disease Landscapes at Single-Cell Resolution: Pathogenetic and Therapeutic Perspectives

Cerebrovascular diseases are a leading cause of death and disability globally. The development of new therapeutic targets for cerebrovascular diseases (e.g., ischemic, and hemorrhagic stroke, vascular dementia) is limited by a lack of knowledge of the cellular and molecular biology of health and disease conditions and the factors that cause injury to cerebrovascular structures. Here, we describe the role of advances in omics technology, particularly RNA sequencing, in studying high-dimensional, multifaceted profiles of thousands of individual blood and vessel cells at single-cell resolution. This analysis enables the dissection of the heterogeneity of diseased cerebral vessels and their atherosclerotic plaques, including the microenvironment, cell evolutionary trajectory, and immune response pathway. In animal models, RNA sequencing permits the tracking of individual cells (including immunological, endothelial, and vascular smooth muscle cells) that compose atherosclerotic plaques and their alteration under experimental settings such as phenotypic transition. We describe how single-cell RNA transcriptomics in humans allows mapping to the molecular and cellular levels of atherosclerotic plaques in cerebral arteries, tracking individual lymphocytes and macrophages, and how these data can aid in identifying novel immune mechanisms that could be exploited as therapeutic targets for cerebrovascular diseases. Single-cell multi-omics approaches will likely provide the unprecedented resolution and depth of data needed to generate clinically relevant cellular and molecular signatures for the precise treatment of cerebrovascular diseases.

TNFα activation and TGFβ blockage act synergistically for smooth muscle cell calcification in patients with venous thrombosis via TGFβ/ERK pathway

Venous calcification has been observed in post‐thrombotic syndrome (PTS) patients; yet, the cell types and possible mechanisms regulating this process are still unclear. We evaluated the calcium deposition within the venous wall, the cell type involved in the calcified remodelling of the venous wall after thrombosis and explored possible mechanisms in vitro. Calcium deposition was found in human specimens of superficial thrombotic veins and was co‐localized with VSMCs markers αSMA and TAGLN (also known as SM22α). Besides, the expression of osteogenesis‐related genes was dramatically changed in superficial thrombotic veins. Moreover, the inhibition of the TGFβ signalling pathway after TNFα treatment effectively induced the expression of osteogenic phenotype markers, the calcium salt deposits and the obvious phosphorylation of ERK1/2 and JNK2 in the VSMCs calcification model. Supplementing TGFβ2 or blocking the activation of the ERK/MAPK signalling pathway prevented the transformation of VSMCs into osteoblast‐like cells in vitro. Taken together, VSMCs have an important role in venous calcification after thrombosis. Supplementing TGFβ2 or inhibiting the ERK/MAPK signalling pathway can reduce the appearance of VSMCs osteogenic phenotype. Our findings may present a novel therapeutic approach to prevent of vascular calcification after venous thrombosis.

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.

Non-Invasive Modalities in the Assessment of Vulnerable Coronary Atherosclerotic Plaques

Coronary atherosclerosis is a complex, multistep process that may lead to critical complications upon progression, revolving around plaque disruption through either rupture or erosion. Several high-risk features are associated with plaque vulnerability and may add incremental prognostic information. Although invasive imaging modalities such as optical coherence tomography or intravascular ultrasound are considered to be the gold standard in the assessment of vulnerable coronary atherosclerotic plaques (VCAPs), contemporary evidence suggests a potential role for non-invasive methods in this context. Biomarkers associated with deleterious pathophysiologic pathways, including inflammation and extracellular matrix degradation, have been correlated with VCAP characteristics and adverse prognosis. However, coronary computed tomography (CT) angiography has been the most extensively investigated technique, significantly correlating with invasive method-derived VCAP features. The estimation of perivascular fat attenuation as well as radiomic-based approaches represent additional concepts that may add incremental information. Cardiac magnetic resonance imaging (MRI) has also been evaluated in clinical studies, with promising results through the various image sequences that have been tested. As far as nuclear cardiology is concerned, the implementation of positron emission tomography in the VCAP assessment currently faces several limitations with the myocardial uptake of the radiotracer in cases of fluorodeoxyglucose use, as well as with motion correction. Moreover, the search for the ideal radiotracer and the most adequate combination (CT or MRI) is still ongoing. With a look to the future, the possible combination of imaging and circulating inflammatory and extracellular matrix degradation biomarkers in diagnostic and prognostic algorithms may represent the essential next step for the assessment of high-risk individuals.

ROLE OF HYALURONAN IN PATHOPHYSIOLOGY OF VASCULAR1 ENDOTHELIAL AND SMOOTH MUSCLE CELLS

One of the main components of the extracellular matrix (ECM) of the blood vessel is hyaluronic acid or hyaluronan (HA). It is a ubiquitous polysaccharide belonging to the family of glycosaminoglycans, but, differently from other proteoglycan-associated glycosaminoglycans, it is synthesized on the plasma membrane by a family of three HA synthases (HAS). HA can be released as a free polymer in the extracellular space or remain associated with the membrane in the pericellular space via HAS or via binding proteins. In fact, several cell surface proteins can interact with HA working as HA receptors like CD44, RHAMM, and LYVE-1. In physiological conditions, HA is localized in the glycocalyx and in the adventitia and is responsible for the loose and hydrated vascular structure favoring flexibility and allowing the stretching of vessels in response to mechanical forces. During atherogenesis, ECM undergoes dramatic alterations which have a crucial role in lipoprotein retention and in triggering multiple signaling cascades that wake up cells from their quiescent status. HA becomes highly present in the media and neointima favoring smooth muscle cells dedifferentiation, migration, and proliferation that strongly contribute to vessel wall thickening. Further, HA is able to modulate immune cell recruitment both within the vessel wall and on the endothelial cell layer. This review is focused on the effects of HA on vascular cell behavior.