Vascular injury activates the ELK1/SND1/SRF pathway to promote vascular smooth muscle cell proliferative phenotype and neointimal hyperplasia.

BACKGROUND: Vascular smooth muscle cell (VSMC) proliferation is the leading cause of vascular stenosis or restenosis. Therefore, investigating the molecular mechanisms and pivotal regulators of the proliferative VSMC phenotype is imperative for precisely preventing neointimal hyperplasia in vascular disease. METHODS: Wire-induced vascular injury and aortic culture models were used to detect the expression of staphylococcal nuclease domain-containing protein 1 (SND1). SMC-specific Snd1 knockout mice were used to assess the potential roles of SND1 after vascular injury. Primary VSMCs were cultured to evaluate SND1 function on VSMC phenotype switching, as well as to investigate the mechanism by which SND1 regulates the VSMC proliferative phenotype. RESULTS: Phenotype-switched proliferative VSMCs exhibited higher SND1 protein expression compared to the differentiated VSMCs. This result was replicated in primary VSMCs treated with platelet-derived growth factor (PDGF). In the injury model, specific knockout of Snd1 in mouse VSMCs reduced neointimal hyperplasia. We then revealed that ETS transcription factor ELK1 (ELK1) exhibited upregulation and activation in proliferative VSMCs, and acted as a novel transcription factor to induce the gene transcriptional activation of Snd1. Subsequently, the upregulated SND1 is associated with serum response factor (SRF) by competing with myocardin (MYOCD). As a co-activator of SRF, SND1 recruited the lysine acetyltransferase 2B (KAT2B) to the promoter regions leading to the histone acetylation, consequently promoted SRF to recognize the specific CArG motif, and enhanced the proliferation- and migration-related gene transcriptional activation. CONCLUSIONS: The present study identifies ELK1/SND1/SRF as a novel pathway in promoting the proliferative VSMC phenotype and neointimal hyperplasia in vascular injury, predisposing the vessels to pathological remodeling. This provides a potential therapeutic target for vascular stenosis.

Identification of distinct vascular mural cell populations during zebrafish embryonic development.

BACKGROUND: Mural cells are an essential perivascular cell population that associate with blood vessels and contribute to vascular stabilization and tone. In the embryonic zebrafish vasculature, pdgfrb and tagln are commonly used as markers for identifying pericytes and vascular smooth muscle cells. However, the overlapping and distinct expression patterns of these markers in tandem have not been fully described. RESULTS: Here, we used the Tg(pdgfrb:Gal4FF; UAS:RFP) and Tg(tagln:NLS-EGFP) transgenic lines to identify single- and double-positive perivascular cell populations on the cranial, axial, and intersegmental vessels between 1 and 5 days postfertilization. From this comparative analysis, we discovered two novel regions of tagln-positive cell populations that have the potential to function as mural cell precursors. Specifically, we found that the hypochord-a reportedly transient structure-contributes to tagln-positive cells along the dorsal aorta. We also identified a unique mural cell progenitor population that resides along the midline between the neural tube and notochord and contributes to intersegmental vessel mural cell coverage. CONCLUSION: Together, our findings highlight the variability and versatility of tracking both pdgfrb and tagln expression in mural cells of the developing zebrafish embryo and reveal unexpected embryonic cell populations that express pdgfrb and tagln.

NEAT1 regulates VSMC differentiation and calcification in as long noncoding RNA NEAT1 enhances phenotypic and osteogenic switching of vascular smooth muscle cells in atherosclerosis via scaffolding EZH2.

Atherosclerosis (AS) is a significant contributor to cardio-cerebrovascular ischemia diseases, resulting in high mortality rates worldwide. During AS, vascular smooth muscle cells (VSMCs) play a crucial role in plaque formation by undergoing phenotypic and osteogenic switching. Long noncoding RNA nuclear paraspeckle assembly transcript 1 (NEAT1) has previously been identified as a nuclear regulator that promotes tumorigenesis and metastasis, but its role in regulating VSMCs in AS remains unclear. Our study aimed to investigate the biological functions and specific mechanisms of NEAT1 in regulating VSMCs in AS. We found that NEAT1 was upregulated in the aortas of AS mouse models and dedifferentiated primary VSMCs. Silencing NEAT1 in vitro attenuated the proliferation, migration, and osteogenic differentiation of VSMCs, while NEAT1 overexpression had the opposite effect. Furthermore, NEAT1 promoted VSMC osteogenic differentiation and vascular calcification in both in vivo and in vitro vascular calcification models. We also discovered that NEAT1 directly activates enhancer of zeste homolog 2 (EZH2), an epigenetic enzyme that suppresses the expression of senescence- and antimigration-related genes, by translocating it into the nucleus. CUT&Tag assay revealed that NEAT1 guides EZH2 to the promoters of senescence-related genes (P16, P21, and TIMP3), methylating local histones to reduce their transcription. Our findings suggest that NEAT1 functions in AS by modulating the epigenetic function of EZH2, which enhances the proliferation, migration, and osteogenic differentiation of VSMCs. This study provides new insights into the molecular mechanisms underlying the pathogenesis of AS and highlights the potential of NEAT1 as a therapeutic target of AS.NEW & NOTEWORTHY Our study demonstrates that the upregulation of long noncoding RNA nuclear paraspeckle assembly transcript 1 (NEAT1) promotes proliferation and migration during phenotypic switching of vascular smooth muscle cells in atherosclerosis. We also provide in vivo and in vitro evidence that NEAT1 accelerates vascular calcification. Our findings identified the direct interaction between enhancer of zeste homolog 2 (EZH2) and NEAT1 during atherosclerosis. NEAT1 is necessary for EZH2 to translocate from the cytoplasm to the nucleus, where EZH2 epigenetically inhibits the expression of genes related to senescence and antimigration.

Regulatory variants in TCF7L2 are associated with thoracic aortic aneurysm.

Thoracic aortic aneurysm (TAA) is characterized by dilation of the aortic root or ascending/descending aorta. TAA is a heritable disease that can be potentially life threatening. While 10%-20% of TAA cases are caused by rare, pathogenic variants in single genes, the origin of the majority of TAA cases remains unknown. A previous study implicated common variants in FBN1 with TAA disease risk. Here, we report a genome-wide scan of 1,351 TAA-affected individuals and 18,295 control individuals from the Cardiovascular Health Improvement Project and Michigan Genomics Initiative at the University of Michigan. We identified a genome-wide significant association with TAA for variants within the third intron of TCF7L2 following replication with meta-analysis of four additional independent cohorts. Common variants in this locus are the strongest known genetic risk factor for type 2 diabetes. Although evidence indicates the presence of different causal variants for TAA and type 2 diabetes at this locus, we observed an opposite direction of effect. The genetic association for TAA colocalizes with an aortic eQTL of TCF7L2, suggesting a functional relationship. These analyses predict an association of higher expression of TCF7L2 with TAA disease risk. In vitro, we show that upregulation of TCF7L2 is associated with BCL2 repression promoting vascular smooth muscle cell apoptosis, a key driver of TAA disease.

Microvascular smooth muscle cells exhibit divergent phenotypic switching responses to platelet-derived growth factor and insulin-like growth factor 1.

OBJECTIVE: Vascular smooth muscle cell (VSMC) phenotypic switching is critical for normal vessel formation, vascular stability, and healthy brain aging. Phenotypic switching is regulated by mediators including platelet derived growth factor (PDGF)-BB, insulin-like growth factor (IGF-1), as well as transforming growth factor-ß (TGF-ß) and endothelin-1 (ET-1), but much about the role of these factors in microvascular VSMCs remains unclear. METHODS: We used primary rat microvascular VSMCs to explore PDGF-BB- and IGF-1-induced phenotypic switching. RESULTS: PDGF-BB induced an early proliferative response, followed by formation of polarized leader cells and rapid, directionally coordinated migration. In contrast, IGF-1 induced cell hypertrophy, and only a small degree of migration by unpolarized cells. TGF-ß and ET-1 selectively inhibit PDGF-BB-induced VSMC migration primarily by repressing migratory polarization and formation of leader cells. Contractile genes were downregulated by both growth factors, while other genes were differentially regulated by PDGF-BB and IGF-1. CONCLUSIONS: These studies indicate that PDGF-BB and IGF-1 stimulate different types of microvascular VSMC phenotypic switching characterized by different modes of cell migration. Our studies are consistent with a chronic vasoprotective role for IGF-1 in VSMCs in the microvasculature while PDGF is more involved in VSMC proliferation and migration in response to acute activities such as neovascularization. Better understanding of the nuances of the phenotypic switching induced by these growth factors is important for our understanding of a variety of microvascular diseases.

Pyroptosis of Vascular Smooth Muscle Cells as a Potential New Target for Preventing Vascular Diseases.

Vascular remodeling is the adaptive response of the vessel wall to physiological and pathophysiological changes, closely linked to vascular diseases. Vascular smooth muscle cells (VSMCs) play a crucial role in this process. Pyroptosis, a form of programmed cell death characterized by excessive release of inflammatory factors, can cause phenotypic transformation of VSMCs, leading to their proliferation, migration, and calcification-all of which accelerate vascular remodeling. Inhibition of VSMC pyroptosis can delay this process. This review summarizes the impact of pyroptosis on VSMCs and the pathogenic role of VSMC pyroptosis in vascular remodeling. We also discuss inhibitors of key proteins in pyroptosis pathways and their effects on VSMC pyroptosis. These findings enhance our understanding of the pathogenesis of vascular remodeling and provide a foundation for the development of novel medications that target the control of VSMC pyroptosis as a potential treatment strategy for vascular diseases.

PUM2 regulates the formation of thoracic aortic dissection through EFEMP1.

Thoracic aortic dissection (TAD) is a severe cardiovascular disease attributed to the abnormal phenotypic switch of vascular smooth muscle cells (VSMCs). We found that the RNA-binding protein PUM2 and the fibulin protein EFEMP1 were significantly decreased at the TAD anatomical site. Therefore, we constructed expression and silencing vectors for PUM2 and EFEMP1 to analyze differential expression. Overexpression of PUM2 inhibited VSMC proliferation and migration. Western blot analysis indicated that PUM2 overexpression in VSMCs upregulated α-SMA and SM22α and downregulated OPN and MMP2. Immunofluorescence demonstrated that PUM2 and EFEMP1 were co-expressed in VSMCs. Immunoprecipitation confirmed that PUM2 bound to EFEMP1 mRNA to promote EFEMP1 expression. An Ang-II-induced aortic dissection mouse model showed that PUM2 impedes the development of aortic dissection in vivo. Our study demonstrates that PUM2 inhibits the VSMC phenotypic switch to prevent aortic dissection by targeting EFEMP1 mRNA. These findings could assist the development of targeted therapy for TAD.

Myeloid-derived growth factor suppresses VSMC dedifferentiation and attenuates postinjury neointimal formation in rats by activating S1PR2 and its downstream signaling.

Restenosis after angioplasty is caused usually by neointima formation characterized by aberrant vascular smooth muscle cell (VSMC) dedifferentiation. Myeloid-derived growth factor (MYDGF), secreted from bone marrow-derived monocytes and macrophages, has been found to have cardioprotective effects. In this study we investigated the effect of MYDGF to postinjury neointimal formation and the underlying mechanisms. Rat carotid arteries balloon-injured model was established. We found that plasma MYDGF content and the level of MYDGF in injured arteries were significantly decreased after balloon injury. Local application of exogenous MYDGF (50 µg/mL) around the injured vessel during balloon injury markedly ameliorated the development of neointimal formation evidenced by relieving the narrow endovascular diameter, improving hemodynamics, and reducing collagen deposition. In addition, local application of MYDGF inhibited VSMC dedifferentiation, which was proved by reversing the elevated levels of osteopontin (OPN) protein and decreased levels of α-smooth muscle actin (α-SMA) in the left carotid arteries. We showed that PDGF-BB (30 ng/mL) stimulated VSMC proliferation, migration and dedifferentiation in vitro; pretreatment with MYDGF (50-200 ng/mL) concentration-dependently eliminated PDGF-BB-induced cell proliferation, migration and dedifferentiation. Molecular docking revealed that MYDGF had the potential to bind with sphingosine-1-phosphate receptor 2 (S1PR2), which was confirmed by SPR assay and Co-IP analysis. Pretreatment with CCG-1423 (Rho signaling inhibitor), JTE-013 (S1PR2 antagonist) or Ripasudil (ROCK inhibitor) circumvented the inhibitory effects of MYDGF on VSMC phenotypic switching through inhibiting S1PR2 or its downstream RhoA-actin monomers (G-actin) /actin filaments (F-actin)-MRTF-A signaling. In summary, this study proves that MYDGF relieves neointimal formation of carotid arteries in response to balloon injury in rats, and suppresses VSMC dedifferentiation induced by PDGF-BB via S1PR2-RhoA-G/F-actin-MRTF-A signaling pathway. In addition, our results provide evidence for cross talk between bone marrow and vasculature.

MicroRNA regulation of phenotypic transformations in vascular smooth muscle: relevance to vascular remodeling.

Alterations in the vascular smooth muscle cells (VSMC) phenotype play a critical role in the pathogenesis of several cardiovascular diseases, including hypertension, atherosclerosis, and restenosis after angioplasty. MicroRNAs (miRNAs) are a class of endogenous noncoding RNAs (approximately 19-25 nucleotides in length) that function as regulators in various physiological and pathophysiological events. Recent studies have suggested that aberrant miRNAs' expression might underlie VSMC phenotypic transformation, appearing to regulate the phenotypic transformations of VSMCs by targeting specific genes that either participate in the maintenance of the contractile phenotype or contribute to the transformation to alternate phenotypes, and affecting atherosclerosis, hypertension, and coronary artery disease by altering VSMC proliferation, migration, differentiation, inflammation, calcification, oxidative stress, and apoptosis, suggesting an important regulatory role in vascular remodeling for maintaining vascular homeostasis. This review outlines recent progress in the discovery of miRNAs and elucidation of their mechanisms of action and functions in VSMC phenotypic regulation. Importantly, as the literature supports roles for miRNAs in modulating vascular remodeling and for maintaining vascular homeostasis, this area of research will likely provide new insights into clinical diagnosis and prognosis and ultimately facilitate the identification of novel therapeutic targets.

circACTA2 inhibits NLRP3 inflammasome-mediated inflammation via interacting with NF-κB in vascular smooth muscle cells.

circACTA2 derived from the smooth muscle α-actin gene plays an important role in the regulation of vascular smooth muscle cell (VSMC) phenotype. The activation of NLRP3 inflammasome is involved in VSMC phenotypic switching. However, the mechanistic relationship between circACTA2 and NLRP3 inflammasome during vascular remodeling remains poorly understood. Here, we showed that circACTA2 was down-regulated in human intimal hyperplasia. circACTA2 overexpression in circACTA2 transgenic mice significantly decreased the neointimal hyperplasia induced by vascular injury, which is concomitant with a decrease in IL-18, IL-1ß, TNF-α, and IL-6 levels. Gain- and loss-of-function studies revealed that circACTA2 alleviated VSMC inflammation by suppressing the activation of NLRP3 inflammasome. Mechanistically, circACTA2 inhibited the expression of NF-κB p65 and p50 subunits and interacted with p50, which impedes the formation of the p50/p65 heterodimer and nuclear translocation induced by TNF-α, thus resulting in the suppression of NLRP3 gene transcription and inflammasome activation. Furthermore, circACTA2 overexpression mitigated inflammation via repressing NLRP3 inflammasome-mediated VSMC pyroptosis. Importantly, employing a decoy oligonucleotide to compete with circACTA2 for binding to p50 could attenuate the expression of NLRP3, ASC, and caspase-1. These findings provide a novel insight into the functional roles of circACTA2 in VSMCs, and targeting the circACTA2-NF-κB-NLRP3 axis represents a promising therapeutic strategy for vascular remodeling.

Scutellarin inhibits oleic acid induced vascular smooth muscle foam cell formation via activating autophagy and inhibiting NLRP3 inflammasome activation.

Abnormalities in vascular smooth muscle cells (VSMCs) are pivotal in the pathogenesis of cardiovascular pathologies such as atherosclerosis and hypertension. Scutellarin (Scu), a flavonoid derived from marigold flowers, exhibits a spectrum of biological activities including anti-inflammatory, antioxidant, antitumor, immunomodulatory and antimicrobial effects. Notably, Scu has demonstrated the capacity to mitigate vascular endothelial damage and prevent atherosclerosis via its antioxidative properties. Nevertheless, the influence of Scu on the formation of VSMC-derived foam cells remains underexplored. In this study, Scu was evidenced to efficaciously attenuate oleic acid (OA)-induced lipid accumulation and the upregulation of adipose differentiation-associated protein Plin2 in a dose- and time-responsive manner. We elucidated that Scu effectively diminishes OA-provoked VSMC foam cell formation. Further, it was established that Scu pretreatment augments the protein expression of LC3B-II and the mRNA levels of Map1lc3b and Becn1, concurrently diminishing the protein levels of the NLRP3 inflammasome compared to the OA group. Activation of autophagy through rapamycin attenuated NLRP3 inflammasome protein expression, intracellular lipid droplet content and Plin2 mRNA levels. Scu also counteracted the OA-induced decrement of LC3B-II levels in the presence of bafilomycin-a1, facilitating the genesis of autophagosomes and autolysosomes. Complementarily, in vivo experiments revealed that Scu administration substantially reduced arterial wall thickness, vessel wall cross-sectional area, wall-to-lumen ratio and serum total cholesterol levels in comparison to the high-fat diet model group. Collectively, our findings suggest that Scu attenuates OA-induced VSMC foam cell formation through the induction of autophagy and the suppression of NLRP3 inflammasome activation.

Type-specific inflammatory responses of vascular cells activated by interaction with virgin and aged microplastics.

Microplastics (MPs) are recognized as a major environmental problem due to their ubiquitous presence in ecosystems and bioaccumulation in food chains. Not only humans are continuously exposed to these pollutants through ingestion and inhalation, but recent findings suggest they may trigger vascular inflammation and potentially worsen the clinical conditions of cardiovascular patients. Here we combine headspace analysis by needle trap microextraction-gas chromatography-mass spectrometry (HS-NTME-GC-MS) and biological assays to evaluate the effects of polystyrene, high- and low-density polyethylene MPs on phenotype, metabolic activity, and pro-inflammatory status of Vascular Smooth Muscle Cells (VSMCs) the most prominent cells in vascular walls. Virgin and artificially aged MPs (4 weeks at 40 °C and 750 W/m2 simulated solar irradiation) were comparatively tested at 1 mg/mL to simulate a realistic exposure scenario. Our results clearly show the activation of oxidative stress and inflammatory processes when VSMCs were cultured with aged polymers, with significant overexpression of IL-6 and TNF-α. In addition, volatile organic compounds (VOCs), including pentane, acrolein, propanal, and hexanal as the main components, were released by VSMCs into the headspace. Type-specific VOC response profiles were induced on vascular cells from different MPs.

Fluoride-induced hypertension by regulating RhoA/ROCK pathway and phenotypic transformation of vascular smooth muscle cells: In vitro and in vivo evidence.

Fluoride exposure has been implicated as a potential risk factor for hypertension, but the underlying mechanisms remain unclear. This study investigated the role of the RhoA/ROCK signaling pathway in fluoride-induced hypertension. Male Wistar rats were divided into different groups and exposed to varying concentrations of sodium fluoride (NaF) or sodium chloride (NaCl) via drinking water. The rats' blood pressure was measured, and their aortic tissue was utilized for high-throughput sequencing analysis. Additionally, rat and A7r5 cell models were established using NaF and/or Fasudil. The study evaluated the effects of fluoride exposure on blood pressure, pathological changes in the aorta, as well as the protein/mRNA expression levels of phenotypic transformation indicators (a-SMA, calp, OPN) in vascular smooth muscle cells (VSMCs), along with the RhoA/ROCK signaling pathway (RhoA, ROCK1, ROCK2, MLC/p-MLC). The results demonstrated that fluoride exposure in rats led to increased blood pressure. High-throughput sequencing analysis revealed differential gene expression associated with vascular smooth muscle contraction, with the RhoA/ROCK signaling pathway emerging as a key regulator. Pathological changes in the rat aorta, such as elastic membrane rupture and collagen fiber deposition, were observed following NaF exposure. However, fasudil, a ROCK inhibitor, mitigated these pathological changes. Both in vitro and in vivo models confirmed the activation of the RhoA/ROCK signaling pathway and the phenotypic transformation of VSMCs from a contractile to a synthetic state upon fluoride exposure. Fasudil effectively inhibited the activities of ROCK1 and ROCK2 and attenuated the phenotypic transformation of VSMCs. In conclusion, fluoride has the potential to induce hypertension through the activation of the RhoA/ROCK signaling pathway and phenotypic changes in vascular smooth muscle cells. These results provide new insights into the mechanism of fluoride-induced hypertension.

Molecular mechanisms and therapeutic perspectives of peroxisome proliferator-activated receptor α agonists in cardiovascular health and disease.

The prevalence of cardiovascular disease (CVD) has been rising due to sedentary lifestyles and unhealthy dietary patterns. Peroxisome proliferator-activated receptor α (PPARα) is a nuclear receptor regulating multiple biological processes, such as lipid metabolism and inflammatory response critical to cardiovascular homeostasis. Healthy endothelial cells (ECs) lining the lumen of blood vessels maintains vascular homeostasis, where endothelial dysfunction associated with increased oxidative stress and inflammation triggers the pathogenesis of CVD. PPARα activation decreases endothelial inflammation and senescence, contributing to improved vascular function and reduced risk of atherosclerosis. Phenotypic switch and inflammation of vascular smooth muscle cells (VSMCs) exacerbate vascular dysfunction and atherogenesis, in which PPARα activation improves VSMC homeostasis. Different immune cells participate in the progression of vascular inflammation and atherosclerosis. PPARα in immune cells plays a critical role in immunological events, such as monocyte/macrophage adhesion and infiltration, macrophage polarization, dendritic cell (DC) embedment, T cell activation, and B cell differentiation. Cardiomyocyte dysfunction, a major risk factor for heart failure, can also be alleviated by PPARα activation through maintaining cardiac mitochondrial stability and inhibiting cardiac lipid accumulation, oxidative stress, inflammation, and fibrosis. This review discusses the current understanding and future perspectives on the role of PPARα in the regulation of the cardiovascular system as well as the clinical application of PPARα ligands.

MicroRNA-499-5p promotes vascular smooth muscle cell proliferation and migration via inhibiting SOX6.

Atherosclerosis (AS) is the primary etiology of cardiovascular disease, which is considered the leading cause of death all over the world. MicroRNA miR-499-5p was involved in the functional regulation of myocardial and skeletal muscle, whereas its role in atherosclerosis, especially in vascular smooth muscle cells (VSMCs), remains unclear. Our study aims to investigate the effects of miR-499-5p in the proliferation and migration of VSMCs and potential mechanisms. We used mouse aortic vascular smooth muscle cells (MOVAS) and ApoE-/- mice to establish the models of AS in vitro and in vivo, respectively. RT-PCR was performed to detect the expression level of miR-499-5p. Subsequently, Cell Counting Kit-8 (CCK-8) assays, Transwell assays, and wound-healing assays were used to evaluate cell proliferation and migration. Dual-luciferase reporter assay was performed to validate the interaction between miR-499-5p and SOX6. miR-499-5p significantly increased in aorta tissues of mice in AS tissues and vascular smooth muscle cells treated with ox-LDL. miR-499-5p overexpression could promote the proliferation and migration of MOVAS. Bioinformatics analysis predicted and further experiments verified that miR-499-5p could directly bind to the 3'-untranslated region (UTR) region of SOX6. Further, miR-499-5p induced an increased expression of smooth muscle proliferation and migration-related genes, PCNA, cyclin D1, and matrix metalloproteinase (MMP2), as well as the decreased expression of proliferation inhibiting factor p21, which was significantly reversed by SOX6 overexpression. miR-499-5p boosts the proliferation and migration of smooth muscle cells by binding and inhibiting SOX6 expression. The miR-499-5p/SOX6 axis may present a promising therapeutic implication for the prevention and treatment of cardiovascular diseases.

Vascular calcification in CKD: New insights into its mechanisms.

Vascular calcification (VC) is a common complication of chronic kidney disease (CKD) and contributes to an increased risk of cardiovascular morbidity and mortality. However, effective therapies are still unavailable at present. It has been well established that VC associated with CKD is not a passive process of calcium phosphate deposition, but an actively regulated and cell-mediated process that shares many similarities with bone formation. Additionally, numerous studies have suggested that CKD patients have specific risk factors and contributors to the development of VC, such as hyperphosphatemia, uremic toxins, oxidative stress and inflammation. Although research efforts in the past decade have greatly improved our knowledge of the multiple factors and mechanisms involved in CKD-related VC, many questions remain unanswered. Moreover, studies from the past decade have demonstrated that epigenetic modifications abnormalities, such as DNA methylation, histone modifications and noncoding RNAs, play an important role in the regulation of VC. This review seeks to provide an overview of the pathophysiological and molecular mechanisms of VC associated with CKD, mainly focusing on the involvement of epigenetic modifications in the initiation and progression of uremic VC, with the aim to develop promising therapies for CKD-related cardiovascular events in the future.

HOXA1 participates in VSMC-to-macrophage-like cell transformation via regulation of NF-κB p65 and KLF4: a potential mechanism of atherosclerosis pathogenesis.

BACKGROUND: Macrophage-like transformation of vascular smooth muscle cells (VSMCs) is a risk factor of atherosclerosis (AS) progression. Transcription factor homeobox A1 (HOXA1) plays functional roles in differentiation and development. This study aims to explore the role of HOXA1 in VSMC transformation, thereby providing evidence for the potential mechanism of AS pathogenesis. METHODS: High fat diet (HFD)-fed apolipoprotein E knockout (ApoE-/-) mice were applied as an in vivo model to imitate AS, while 1-palmitoyl-2-(5-oxovaleroyl)-sn-glycero-3-phosphocholine (POV-PC)-treated VSMCs were applied as an in vitro model. Recombinant adeno-associated-virus-1 (AAV-1) vectors that express short-hairpin RNAs targeting HOXA1, herein referred as AAV1-shHOXA1, were generated for the loss-of-function experiments throughout the study. RESULTS: In the aortic root of AS mice, lipid deposition was severer and HOXA1 expression was higher than the wide-type mice fed with normal diet or HFD. Silencing of HOXA1 inhibited the AS-induced weight gain, inflammatory response, serum and liver lipid metabolism disorder and atherosclerotic plaque formation. Besides, lesions from AS mice with HOXA1 knockdown showed less trans-differentiation of VSMCs to macrophage-like cells, along with a suppression of krüppel-like factor 4 (KLF4) and nuclear factor (NF)-κB RelA (p65) expression. In vitro experiments consistently confirmed that HOXA1 knockdown suppressed lipid accumulation, VSMC-to-macrophage phenotypic switch and inflammation in POV-PC-treated VSMCs. Mechanism investigations further illustrated that HOXA1 transcriptionally activated RelA and KLF4 to participate in the pathological manifestations of VSMCs. CONCLUSIONS: HOXA1 participates in AS progression by regulating VSMCs plasticity via regulation of NF-κB p65 and KLF4. HOXA1 has the potential to be a biomarker or therapeutic target for AS.

Development of vascular regulation in the zebrafish embryo.

The thin endothelial wall of a newly formed vessel is under enormous stress at the onset of blood flow, rapidly acquiring support from mural cells (pericytes and vascular smooth muscle cells; vSMCs) during development. Mural cells then develop vasoactivity (contraction and relaxation) but we have little information as to when this first develops or the extent to which pericytes and vSMCs contribute. For the first time, we determine the dynamic developmental acquisition of vasoactivity in vivo in the cerebral vasculature of zebrafish. We show that pericyte-covered vessels constrict in response to α1-adrenergic receptor agonists and dilate in response to nitric oxide donors at 4 days postfertilization (dpf) but have heterogeneous responses later, at 6 dpf. In contrast, vSMC-covered vessels constrict at 6 dpf, and dilate at both stages. Using genetic ablation, we demonstrate that vascular constriction and dilation is an active response. Our data suggest that both pericyte- and vSMC-covered vessels regulate their diameter in early development, and that their relative contributions change over developmental time.

Vascular smooth muscle cells in intracranial aneurysms.

Intracranial aneurysm (IA) is a severe cerebrovascular disease characterized by abnormal bulging of cerebral vessels that may rupture and cause a stroke. The expansion of the aneurysm accompanies by the remodeling of vascular matrix. It is well-known that vascular remodeling is a process of synthesis and degradation of extracellular matrix (ECM), which is highly dependent on the phenotype of vascular smooth muscle cells (VSMCs). The phenotypic switching of VSMC is considered to be bidirectional, including the physiological contractile phenotype and alternative synthetic phenotype in response to injury. There is increasing evidence indicating that VSMCs have the ability to switch to various phenotypes, including pro-inflammatory, macrophagic, osteogenic, foamy and mesenchymal phenotypes. Although the mechanisms of VSMC phenotype switching are still being explored, it is becoming clear that phenotype switching of VSMCs plays an essential role in IA formation, progression, and rupture. This review summarized the various phenotypes and functions of VSMCs associated with IA pathology. The possible influencing factors and potential molecular mechanisms of the VSMC phenotype switching were further discussed. Understanding how phenotype switching of VSMC contributed to the pathogenesis of unruptured IAs can bring new preventative and therapeutic strategies for IA.

Circ_0090231 knockdown protects vascular smooth muscle cells from ox-LDL-induced proliferation, migration and invasion via miR-942-5p/PPM1B axis during atherosclerosis.

Atherosclerosis (AS) is a dominant pathological basis of cardiovascular disease. Circular RNAs (circRNAs) have been proposed to have crucial functions in regulating pathological progressions of AS. Hence, the aim of this study was to investigate the potential function of circ_0090231 in AS progression. Oxidized low densitylipoprotein (ox-LDL)-challenged vascular smooth muscle cells (VSMCs) were used for in vitro functional analysis. Levels of genes and proteins were measured by qRT-PCR and Western blot. The proliferation, migration and invasion were assessed using cell counting kit-8, 5-ethynyl-2'-deoxyuridine, and transwell assays. The interaction between miR-942-5p and circ_0090231 or PPM1B (Protein Phosphatase, Mg2+/Mn2+ Dependent 1B) was evaluated by dual-luciferase reporter and pull-down assays. Circ_0090231 is a stable circRNA, and was increased in the serum of AS patients and ox-LDL-challenged VSMCs. Functionally, silencing of circ_0090231 could reverse ox-LDL-induced proliferation, migration and invasion in VSMCs. Mechanistically, circ_0090231 directly targeted miR-942-5p, and PPM1B was a target of miR-942-5p. Besides, circ_0090231 sequestered miR-942-5p to release PPM1B expression, suggesting the circ_0090231/miR-942-5p/PPM1B axis. Further rescue experiments showed that miR-942-5p inhibition or ectopic overexpression of PPM1B dramatically attenuated the suppressing influences of circ_0090231 knockdown on VSMC proliferative, migratory and invasive abilities under ox-LDL treatment. Silencing of circ_0090231 could reverse ox-LDL-induced proliferation, migration and invasion in VSMCs via miR-942-5p/PPM1B axis, providing a theoretical basis for elucidating the mechanism of AS process.