Contractile Phenotype Research Articles

Abstract 18753: Dynamic Phenotypic Transition of Smooth Muscle Cells During Human Ascending Thoracic Aortic Disease Progression: From Compensation in Aortic Aneurysm to Decompensation in Aortic Dissection

Introduction: Although ascending thoracic aortic aneurysm (ATAA) and ascending thoracic aortic dissection (ATAD) share common pathologic features of aortic degeneration, the specific elements that lead to rapid disease progression in ATAD remain poorly understood. We examined the molecular and cellular dynamics in smooth muscle cells (SMCs) of aortic tissues from ATAA and ATAD patients and further examined mechanisms in a mouse model. Methods: Single-cell RNA sequencing (scRNA-seq) analyses were performed in ascending aortic tissues from individuals without aortic disease (n=8), patients with ATAA without dissection (n=9), and patients with acute ATAD (n=9). Further, scRNA-seq and scATAC-seq were performed in ascending aortic tissues from mice infused with angiotensin II (AngII) or control mice; scRNA-seq analyses were performed on SMC-specific Tgfbr2 -/- mice. Results: Six SMC subtypes were identified in human aortic tissues. Cluster proportion and trajectory analyses indicated a profound SMC transition from contractile in control to extracellular matrix (ECM)-contractile phenotype in ATAA, however, was reduced in ATAD tissues. Instead, ATAD showed significant SMC transition to inflammatory phenotype. Consistently, many genes in ECM organization and muscle contraction, collectively termed compensatory response, were upregulated in ATAA but downregulated in ATAD tissues compared with controls, whereas inflammatory response and cell death pathway genes were significantly upregulated in ATAD compared with control and ATAA tissues. Cell-cell interaction, regulatory network, and motif analysis suggested that TGF-beta-MEF2C signaling contributed to the induction of the ECM-contractile SMC phenotype. MEF2C + SMCs exhibited the capacity of transition towards ECM-producing SMCs in both mouse and human aorta. SMC-specific Tgfbr2 -/- mice showed compromised SMC transition to ECM-producing phenotype. Conclusions: Our study reveals SMC phenotypic transitions to ECM-producing SMCs in ATAA and to inflammatory and pro-death SMCs in ATAD, which represent a compensatory response in ATAA and a decompensatory status in ATAD. TGF-beta-MEF2C, a novel regulatory axis, promoted the compensatory response in SMCs of the ascending aorta.

Abstract 13229: Coiled-Coil Domain-Containing Protein 80 Protects Against Aortic Dissection by Maintaining the Contractile Smooth Muscle Cell Phenotype

Background: Aortic dissection (AD) is a life-threatening medical emergency characterized by adverse vascular remodeling. Effective prevention and treatment options are lacking for AD. Coiled-coil domain-containing protein 80 (CCDC80) plays an essential role in regulating vascular remodeling. In the present study, we aimed to define the role of CCDC80 in the formation and development of AD. Methods: The expression and subcellular localization of CCDC80 were determined in human and mouse AD. CCDC80 knockout mice (CCDC80 –/– ) and vascular smooth muscle cell (VSMC)-specific CCDC80 knockout mice (CCDC80 fl/fl SM22α Cre + ) were treated with angiotensin II (Ang II) or Ang II combined with β-aminopropionitrile monofumarate (BAPN) to induce AD models. RNA-Seq analysis combined with immunoprecipitation and blockage of the JAK2/STAT3 signaling pathway in CCDC80 –/– mice were used to evaluate the effect of CCDC80 deficiency on this pathway. Results: CCDC80 was downregulated in VSMCs in human and mouse AD. CCDC80 – / – mice challenged with Ang II and BAPN developed AD with higher frequency and severity compared with their littermate controls (66.7% vs. 100%, p < 0.05). Remarkably, compared with littermate controls treated with Ang II, CCDC80 –/– mice (8.3% vs. 87.5%, p < 0.05) and CCDC80 fl/fl SM22α Cre + mice (12.5% vs. 80%, p < 0.05) frequently developed AD with severe elastin fragmentation and collagen deposition. CCDC80 interacted with JAK2; CCDC80 deficiency could promote VSMC phenotype switching, proliferation, and migration as well as matrix metalloproteinase production by activating the JAK2/STAT3 signaling pathway. The JAK2/STAT3 pathway-specific inhibitor ameliorated adverse vascular remodeling and reduced AD formation (90% vs. 55%, p < 0.05) in CCDC80 knockout mice. Conclusion: CCDC80 deficiency exacerbates the progression of AD by activating the JAK2/STAT3 pathway involved in regulating the phenotype switching and function of VSMCs. Our findings suggest that CCDC80 is a potential target for the prevention and treatment of AD.

Abstract 12710: The Role of Cellular Senescence in Aortic Dissection

Background: Aortic dissection (AD) is a catastrophic disease with high mortality and serious complications, and its molecular pathogenesis is largely unknown. The importance of inflammation in AD has been reported. Recently we found that cell proliferation precedes the inflammatory response in AD. Cell proliferation causes cellular senescence that induces inflammatory response, however, role of cellular senescence in AD has not been elucidated. Objective: We investigated if cellular senescence contributes to AD pathogenesis in mouse AD model. Methods and Results: A mouse AD model was created by continuous infusion of beta-aminopropionitrile and angiotensin II (BAPN+AngII) for 14days. BAPN+AngII infusion induced senescence markers from day 3, before AD onset, and persisted until day14. Senescent cells, as demonstrated by the expression of senescence-associated beta-galactosidase, were evident in intimal endothelial cells, medial smooth muscle cells, adventitial macrophages, and fibroblasts. To examine role of cellular senescence in AD, we orally administrated ABT263 known as “senolytics” that eliminates senescent cells. ABT263 treatment reduced the expression of the senescence markers. The AD mortality of ABT263 group was 35%, which was lower than that of vehicle group(66.7%, P < 0.05 by log-rank test). The severity of AD, as assessed by the lesion length in vehicle group was 33.2 ± 3.1mm, whereas that in ABT263 group was 24.6 ± 1.8mm (P < 0.05). Transcriptome analysis revealed that ABT263 treatment suppressed the immune and inflammatory response in the aorta before AD onset. Quantitative RT-PCR confirmed that ABT263 treatment prevented the induction of p21Cip1, interleukin-6 and several chemokines. Bioplex analysis of mice’s serum showed that ABT263 decreased inflammatory molecules in mice’s serum compared to vehicle group. Moreover, aortic smooth muscle cells(SMCs)remained contractile phenotype in ABT263 group, whereas BAPN+AngII reduced the phenotype in vehicle group. Conclusions: Elimination of senescent cells prevented AD progression and death in mice. ABT263 suppressed the inflammatory response and contributed to retain the SMCs phenotype. Cellular senescence represents a potential predictor and a therapeutic target for AD.

Abstract 18578: BMP9 Regulates Endothelial Expression of Mediators of Pulmonary Vascular Remodeling

Background: Loss-of-function mutations in GDF2 /BMP9 are found in heritable pulmonary arterial hypertension (PAH), suggesting a protective role, while protective or pathogenic effects are found in experimental PAH studies depending on context. The net contribution of BMP9 in PAH thus remains controversial. Hypothesis: BMP9 regulates the secretome of pulmonary microvascular endothelium (PMVEC) to contribute to pulmonary artery smooth muscle cell (PASMC) phenotype modulation. Methods: We tested recombinant BMP9, BMP9/BMP10 trap ALK1-Fc, and BMP9 neutralizing antibody before and after development of pulmonary hypertension (PH) in distinct experimental models. We analyzed the impact of BMP9 on the PMVEC transcriptome, intersection with human and experimental PAH lung transcriptomes, and tested the impact of EC-derived genes on PASMC phenotype and growth. Results: ALK1-Fc and anti-BMP9 prevented or reversed experimental PH administered before or after onset of experimental PH. Recombinant disulfide-linked BMP9 was not protective in SUGEN/Hypoxia (SU-Hx)- or monocrotaline (MCT)-induced experimental PH, in contrast to previous studies using incompletely disulfide-linked BMP9, suggesting dissociated monomers might function as competitive BMP9 antagonists. Consistent with this interpretation, BMP9 upregulated PMVEC genes associated with pulmonary vascular remodeling in experimental and human PAH including CXCL12, IGFBP4, ET-1, VEGF-A, and PDGF-BB. Stimulation of PMVEC with BMP9 induced a contractile phenotype ( CNN1;TAGLN ) in co-cultured PASMC. Administration of ALK1-Fc or anti-BMP9 attenuated expression of several of these growth factors in SU-Hx PH. In experimental PH ALK1-Fc and ACTRIIA-Fc elicited peripheral edema, a phenotype associated with use of ALK1-Fc in human trials. Conclusions: BMP9 contributes to experimental PH by regulating expression of EC-derived molecules modulating PASMC growth and phenotype. In contrast to broad strategies that inhibit BMP9 and BMP10 associated with HHT mimicry in clinical trials and rodent PH models, treatment with anti-BMP9 was well-tolerated. Selective antagonism of BMP9 represents a potential therapeutic strategy for human PAH.

Abstract 13204: Single-Nucleus Multiomic Analyses Identifies Gene Regulatory Dynamics of Phenotypic Modulation in Human Aneurysmal Aortic Root

Introduction: Aortic root aneurysm is a potentially life-threatening condition because it may lead to aortic rupture. However, a single-nucleus transcriptomic and epigenomic landscape in the aortic root tissue of humans is lacking, and the regulatory mechanism of pathogenesis in aneurysmal aortic root remains elusive. We sought to identify molecular triggers for aortic root aneurysm in Marfan syndrome patients. Methods: Aneurysmal aortic root tissues from MFS patients (n=6) and normal aortic root tissues from age-matched, heart transplantation recipients (n=6) were collected. Samples from four subjects of each group were individually subjected to single-nucleus multiomic sequencing (gene expression and chromatin accessibility). Spatial transcriptomic assays were applied to aortic root tissue sections from two subjects of each group. Results: The single-nucleus dataset revealed three subclusters for the vascular smooth muscle cells (VSMCs) lineage including contractile VSMC1 (expressed a high level of RYR2 ), modulated VSMC2 and VSMC3(expressed a high level of CFH ). Statistically significant expansion of the modulated VSMCs was observed in MFS patients. In addition, the modulated VSMCs are not only associated with the diseased states but also associated with the spatial location. The modulated VSMCs are preferentially located in the inner layer of the tunica media close to the intima in both healthy and diseased conditions. Based on the evidence from comparative analyses, we obtained 11 candidate key regulators (such as FOXN3, TEAD1, and BACH1) that potentially drive the phenotypic modulation of VSMCs and the pathogenesis of aortic root aneurysms. The experimental evidence supporting that the forkhead transcription factor FOXN3 may function as a key regulator for maintaining the contractile phenotype of human aortic VSMCs, whose expression decreased during phenotypic modulation and was downregulated in MFS VSMCs. Conclusions: We present the first atlas of gene expression and chromatin accessibility in human aortic root tissue at single-nucleus and spatial resolution. FOXN3 was identified as a novel key regulator for maintaining the contractile phenotype of human aortic VSMCs, which may serve as a potential therapeutic target.

Phenotype and function of smooth muscle cells derived from the human normal great saphenous vein in response to hypoxia.

The contribution of hypoxia to the pathophysiology of vascular smooth muscle cells (VSMCs) has not yet been fully elucidated. This study evaluated the effect of hypoxia on the phenotype and function of SMCs derived from the human normal great saphenous veins (NGSVs). Fifteen NGSV tissue samples were collected. SMCs were isolated and cultured. Proliferation, migration, adhesion, senescence, and the structure of cytoskeletal filaments in SMCs were observed. mRNA and protein expression of Bax, Bcl-2, caspase-3, matrix metalloproteinases (MMP)-2, MMP-9, tissue inhibitor of metalloproteinases (TIMP)-1, and TIMP-2 was detected by fluorescent quantitative polymerase chain reaction and immunoblotting in the cobalt chloride (CoCl2) and the control groups. A decrease in the number of cytoskeletal filaments was observed. mRNA and protein expression of Bas and caspase-3 was significantly decreased, while the quantity of proliferation, migration, adhesion, senescence, and mRNA and protein expression of Bcl-2, MMP-2, MMP-9, TIMP-1, and TIMP-2 in SMCs in the CoCl2 group were significantly increased compared with the control group. Under hypoxic conditions, the phenotype and function of SMCs derived from the human NGSVs were dysregulated, suggesting that VSMCs switch from the contractile phenotype to the secretory or synthetic phenotype, and more dedifferentiate, resulting in extracellular matrix deposition and apoptotic decrease through the intrinsic pathway.

Purification, structural characteristics and anti-atherosclerosis activity of a novel green tea polysaccharide

A new homogeneous polysaccharide (TPS3A) was isolated and purified from Tianzhu Xianyue fried green tea by DEAE-52 cellulose and Sephacryl S-500 column chromatography. Structural characterization indicated that TPS3A mainly consisted of arabinose, galactose, galacturonic acid and rhamnose in a molar ratio of 5.84: 4.15: 2.06: 1, with an average molecular weight of 1.596 × 104 kDa. The structure of TPS3A was characterized as a repeating unit consisting of 1,3-Galp, 1,4-Galp, 1,3,6-Galp, 1,3-Araf, 1,5-Araf, 1,2,4-Rhap and 1-GalpA, with two branches on the C6 of 1,3,6-Galp and C2 of 1,2,4-Rhap, respectively. To investigate the preventive effects of TPS3A on atherosclerosis, TPS3A was administered orally to ApoE-deficient (ApoE−/−) mice. Results revealed that TPS3A intervention could effectively delay the atherosclerotic plaque progression, modulate dyslipidemia, and reduce the transformation of vascular smooth muscle cells (VSMCs) from contractile phenotype to synthetic phenotype by activating the expression of contractile marker alpha-smooth muscle actin (α-SMA) and inhibiting the expression of synthetic marker osteopontin (OPN) in high-fat diet-induced ApoE−/− mice. Our findings suggested that TPS3A markedly alleviated atherosclerosis by regulating dyslipidemia and phenotypic transition of VSMCs, and might be used as a novel functional ingredient to promote cardiovascular health.

Shenlian extract improves atherosclerosis by relieving adventitial inflammation

Ethnopharmacological relevanceShenlian (SL) extract, a Chinese medicinal compound mainly pointing at inflammation response of atherosclerosis, is composed of Salvia miltiorrhizae Bunge and Andrographis paniculata (Burm.f.) Nees. Salvia miltiorrhizae Bunge has been reported to activate blood to remove stasis, while another herb, Andrographis paniculata (Burm.f.) Nees, has been revealed to clear endogenous heat toxins. The anti-atherosclerotic effects of these two herbs have been reported closely relating to inflammation. However, from the point of view of adventitial inflammation, the in-depth study of SL extract in anti-atherosclerotic effects by relieving adventitial inflammation is still unknown. Aim of the studyTo explore the effects of adventitial inflammation in atherosclerosis progression and if SL extract could reverse the process. Materials and methodsA novel atherosclerosis model based on adventitial inflammation was established. High-fat diet-fed ApoE-/- mice were implanted a cotton thread soaked with LPS on the right common carotid artery (RCCA). Meanwhile, three time points were set (week 2, 4, and 12) to accurately evaluate the effect of SL extract on the whole process of atherosclerosis with adventitial inflammation. The pathological changes of phenotype transformation of VAFs, vascular cell proliferation and collagen synthesis were observed dynamically by immunohistochemistry (IHC), BrdU method and sirius red staining. Then primary VAFs were stimulated by LPS to mirror the process of adventitial inflammation in vitro. The VAFS phenotype conversion and its function alterations including proliferation, migration, inflammatory secretion was assessed. Finally, we established a co-culture model of activated VAFs and vascular smooth muscle cells (VSMCs) to observe the impacts of activated VAFs on phenotype transformation and migration of VSMCs. ResultsSL extract improved atherosclerosis progression by reducing lipid content, adventitial inflammation and plaque formation. HE results showed sham-operated group (Sham) appeared light infiltrated inflammation only in adventitia at week 2, and the degree of inflammation infiltrated in model was more severe than that in Sham at week 2, 4, and 12. At week 12, the sham and model group showed evidently thickened media and intima. The phenotypic transformation, proliferation and migration of vascular adventitial fibroblasts (VAFs) as well as inflammatory secretion enhanced remarkably in vivo and vitro, but SL extract reversed these changes. Moreover, SL extract downregulated JAK2-STAT3-MMP2 signal pathway. The VSMCs transformed from contractile phenotype into synthetic phenotype and the migration of VSMCs increased after co-culture with activated VAFs. In contrast, SL extract could suppress theses effects. ConclusionsTaken together, atherosclerotic inflammation could be a “outside-in” signaling. Adventitial inflammation not only accelerated intimal plaque formation in atherosclerosis, but also worsened the degree of vascular lesion. And SL extract improved atherosclerosis by relieving adventitial inflammation, and the underlying mechanisms could be associated with curbing phenotypic transformation, proliferation and migration of VAFs and VSMCs.

Transcriptional impact of EGFR activation in human female vascular smooth muscle cells

Vascular smooth muscle cells (VSMC) are critical for the vascular tone, but they can also drive the development of vascular diseases when they lose their contractile phenotype and de-differentiate. Previous studies showed that the epidermal growth factor receptor (EGFR) of VSMC is critical for vascular health, but most of the underlying mechanisms by which VSMC-EGFR controls vascular fate have remained unknown. We combined RNA-sequencing and bioinformatics analysis to characterize the effect of EGFR-activation on the transcriptome of human primary VSMC (from different female donors) and to identify potentially affected cellular processes. Our results indicate that the activation of human VSMC-EGFR is sufficient to trigger a phenotypical switch toward a proliferative and inflammatory phenotype. The extent of this effect is nonetheless partly donor-dependent. Our hypothesis-generating study thus provides a first insight into mechanisms that could partly explain variable susceptibilities to vascular diseases in between individuals.

AKT Mediates Adiponectin-Dependent Regulation of VSMC Phenotype.

Adiponectin (adipoq), the most abundant hormone in circulation, has many beneficial effects on the cardiovascular system, in part by preserving the contractile phenotype of vascular smooth muscle cells (VSMCs). However, the lack of adiponectin or its receptor and treatment with recombinant adiponectin have shown contradictory effects on plaque in mice. RNA sequence of Adipoq+/+ and adipoq-/- VSMCs from male aortas identified a critical role for adiponectin in AKT signaling, the extracellular matrix (ECM), and TGF-β signaling. Upregulation of AKT activity mediated proliferation and migration of adipoq-/- cells. Activation of AMPK with metformin or AdipoRon reduced AKT-dependent proliferation and migration of adipoq-/- cells but did not improve the expression of contractile genes. Adiponectin deficiency impaired oxidative phosphorylation (OXPHOS), increased expression of glycolytic enzymes, and elevated mitochondrial reactive oxygen species (ROS) (superoxide, and hydrogen peroxide). Anti-atherogenic mechanisms targeted the ECM in adipoq-/- cells, downregulating MMP2 and 9 and upregulating decorin (DCN) and elastin (ELN). In vivo, the main sex differences in protein expression in aortas involved a more robust upregulation of MMP3 in females than males. Females also showed a reduction in DCN, which was not affected in males. Our study uncovered the AKT/MAPK/TGF-β network as a central regulator of VSMC phenotype.

Anti-fouling plus: Engineered stent coating with inflammation-regulation capability enables enhanced tissue healing

Coagulation, inflammation, and hyperplasia frequently restrict the effectiveness of cardiovascular stents. It is critical to modify stent surfaces to allow for in situ tissue healing. Interrelated coagulation and inflammation can impede endothelialization and are critical to the long-term performance of cardiovascular implants. This study proposes a relatively bio-inert “Anti-fouling plus” coating that is effective in anti-coagulation and anti-inflammation at the early stage of implantation and provides mild inflammatory responses during tissue remodeling process. The phosphorylcholine (PC)-based polymer PM(PCLA) is reacted onto a polydopamine-treated polylactic acid (PLA) surface. PC-based polymers that mimic cell membranes present remarkable antiinflammation and anticoagulation properties. The composite of epigallocatechin gallate (EGCG) and tempol is loaded on the PM(PCLA) coating to achieve “anti-fouling plus” which can mediate inflammatory responses by scavenging reactive oxygen species. In vitro hemocompatibility and cell tests demonstrate the effectiveness of coatings in inhibiting thrombus and inflammation. Interestingly, this study originally reveals a novel strategy that the anti-fouling plus coating can direct vascular tissue healing on stent via promoted endothelialization and mediated contractile smooth muscle cell phenotype by switching inflammatory cells to a pro-repair phenotype during tissue healing process, even if the coating is relatively bio-inert.

Phenotypic Switching of Vascular Smooth Muscle Cells in Atherosclerosis.

The medial layer of the arterial wall is composed mainly of vascular smooth muscle cells (VSMCs). Under physiological conditions, VSMCs assume a contractile phenotype, and their primary function is to regulate vascular tone. In contrast with terminally differentiated cells, VSMCs possess phenotypic plasticity, capable of transitioning into other cellular phenotypes in response to changes in the vascular environment. Recent research has shown that VSMC phenotypic switching participates in the pathogenesis of atherosclerosis, where the various types of dedifferentiated VSMCs accumulate in the atherosclerotic lesion and participate in the associated vascular remodeling by secreting extracellular matrix proteins and proteases. This review article discusses the 9 VSMC phenotypes that have been reported in atherosclerotic lesions and classifies them into differentiated VSMCs, intermediately dedifferentiated VSMCs, and dedifferentiated VSMCs. It also provides an overview of several methodologies that have been developed for studying VSMC phenotypic switching and discusses their respective advantages and limitations.

Characterisation of Lipoma-Preferred Partner as a Novel Mechanotransducer in Vascular Smooth Muscle Cells.

In arteries and arterioles, a chronic increase in blood pressure raises wall tension. This continuous biomechanical strain causes a change in gene expression in vascular smooth muscle cells (VSMCs) that may lead to pathological changes. Here we have characterised the functional properties of lipoma-preferred partner (LPP), a Lin11-Isl1-Mec3 (LIM)-domain protein, which is most closely related to the mechanotransducer zyxin but selectively expressed by smooth muscle cells, including VSMCs in adult mice. VSMCs isolated from the aorta of LPP knockout (LPP-KO) mice displayed a higher rate of proliferation than their wildtype (WT) counterparts, and when cultured as three-dimensional spheroids, they revealed a higher expression of the proliferation marker Ki 67 and showed greater invasion into a collagen gel. Accordingly, the gelatinase activity was increased in LPP-KO but not WT spheroids. The LPP-KO spheroids adhering to the collagen gel responded with decreased contraction to potassium chloride. The relaxation response to caffeine and norepinephrine was also smaller in the LPP-KO spheroids than in their WT counterparts. The overexpression of zyxin in LPP-KO VSMCs resulted in a reversal to a more quiescent differentiated phenotype. In native VSMCs, i.e., in isolated perfused segments of the mesenteric artery (MA), the contractile responses of LPP-KO segments to potassium chloride, phenylephrine or endothelin-1 did not vary from those in isolated perfused WT segments. In contrast, the myogenic response of LPP-KO MA segments was significantly attenuated while zyxin-deficient MA segments displayed a normal myogenic response. We propose that LPP, which we found to be expressed solely in the medial layer of different arteries from adult mice, may play an important role in controlling the quiescent contractile phenotype of VSMCs.

Reprogramming endothelial and vascular smooth muscle cells to prevent and treat hypertension

The major pathophysiological characteristic of hypertension is the occurrence of small artery remodeling and endothelial dysfunction. There is also solid evidence showing that microcirculation abnormalities occur prior to the onset of hypertension. However, the mechanism(s) that trigger these changes prior to the elevation of blood pressure are unknown, and this may limit our ability to identify the cause of this disease and effectively treat it. In hypertension, as with aging, the vasculature becomes less susceptible to repair. One of the reasons is because endothelial cells start to deteriorate and present with exacerbated endothelial-to-mesenchymal transition (EndMT). Likewise, vascular smooth muscle cells (VSMC) also dedifferentiate into a synthetic phenotype, whereby they start to produce and secrete extracellular vesicles with a high migration and proliferation capacity for repairing vascular injury. Uncontrolled EndMT and/or VSMC phenotype switching contributes to vascular diseases, but the initial trigger for these conditions is unidentified. Importantly, EndMT and synthetic VSMC exhibit plasticity and can return to adopt an endothelial cell-like fate and present contractile phenotype again, respectively. Therefore, in this hypothesis we will take advantage of this plasticity, and we propose to manipulate this fate by inducing partial cellular reprogramming without passing through the pluripotent state. Specifically, we suggest that activation of the three master transcription factors, Oct-4, Sox-2, and Klf-4 (collectively termed OSK) will reprogram endothelial cells and prevent and reduce EndMT and VSMC synthetic phenotype. It was recently shown that activation of OSK was able to restore lost vision in old mice, and cancer risk was reduced by excluding c-Myc. Therefore, OSK treatment could provide new possibilities for vascular rejuvenation and treatment of hypertension.

Dexamethasone Treatment Preserves the Structure of Adult Cardiac Explants and Supports Their Long-Term Contractility In Vitro

Normal contractile function of the myocardium is essential for optimal cardiovascular health. Evaluating drug effects on cardiomyocyte function at the cellular level is difficult for long-term studies. Present culture systems rely on isolated, cardiomyocyte preparations or cardiomyocytes derived from pluripotent stem cells (PSCs), all of which have limitations. Isolated, endogenous cardiomyocytes do not remain contractile in culture long term. While PSC-derived cardiomyocytes show contractile activity for longer periods of time, their phenotype is more embryonic than adult. Here we report that dexamethasone (DEX) treatment of adult mouse atrial tissue can extend its functionality in culture. Normally, cardiac explants cease their capacity as a contractile tissue within the first month, as the tissue flattens and spreads out on the culture substrate, while the cells dedifferentiate and lose their myocardial phenotype. However, with DEX treatment, cardiac explants maintain their contractile function, 3D morphology, and myocyte phenotype for up to 6 months. Moreover, DEX also preserved the contractile phenotype of isolated rat cardiomyocytes. These data with DEX suggest that simple modifications in culture conditions can greatly improve the long-term utility of in vitro model systems for screening drugs and agents that could be employed to alleviate human cardiac disease.

MiR-590-3p Promotes the Phenotypic Switching of Vascular Smooth Muscle Cells by Targeting Lysyl Oxidase.

We investigated the clinical characteristics of patients with acute aortic dissection (AAD) and miR-590-3p levels in serum, tissue, and vascular smooth muscle cells. The effect of miR-590-3p on the vascular smooth muscle cell phenotype was assessed, and the regulation of lysyl oxidase by miR-5903p was determined. C57BL/6 mice were used to investigate the incidence of AAD and effects of miR-5903p on AAD. The miR-590-3p levels were measured in the aortae of mice, and hematoxylin and eosin staining and Masson staining were performed to identify the morphological features of the aorta. Comparative analysis revealed significant differences in clinical characteristics between patients with AAD and healthy control subjects, with most patients with AAD exhibiting concomitant hypertension and nearly 50% having atherosclerosis. Lysyl oxidase was a direct target of miR-590-3p. Lysyl oxidase overexpression inhibited switching of the vascular smooth muscle cell phenotype from contractile to synthetic, but miR-590-3p overexpression significantly reversed this change. In the mouse model, miR-590-3p upregulation increased the incidence of AAD to 93.3%, and its incidence decreased to 13.3% after miR-590-3p inhibition. Hematoxylin and eosin and Masson staining revealed that the miR-590-3p agomiR group had a greater loss of the contractile phenotype in the dissected aortic wall and an increased number of muscle fibers in the aortic wall, which contributed to thickening of the aortic wall and the formation of a false lumen in aortic dissection. miR-590-3p might be pivotal in the pathogenesis of AAD. Thus, targeting miR-590-3p or its downstream pathways could represent a therapeutic approach for AAD.

Speckle-Tracking Strain Analysis for Mapping Spatiotemporal Contractility of Induced Pluripotent Stem Cell (iPSC)-Derived Cardiomyocytes.

Human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes (hiPSC-CMs) hold tremendous potential for cardiovascular disease modeling, drug screening, personalized medicine, and pathophysiology studies. The availability of a robust protocol and functional assay for studying phenotypic behavior of hiPSC-CMs is essential for establishing an in vitro disease model. Many heart diseases manifest due to changes in the mechanical strain of cardiac tissue. Therefore, non-invasive evaluation of the contractility properties of hiPSC-CMs remains crucial to gain an insight into the pathogenesis of cardiac diseases. Speckle tracking-based strain analysis is an efficient non-invasive method that uses video microscopy and image analysis of beating hiPSC-CMs for quantitative evaluation of mechanical contractility properties. This article presents step-by-step protocols for extracting quantitative contractility properties of an hiPSC-CM system obtained from five members of a family, of whom three were affected by DiGeorge syndrome, using speckle tracking-based strain analysis. The hiPSCs from the family members were differentiated and purified into hiPSC-CMs using metabolic selection. Time-lapse images of hiPSC-CMs were acquired using high-spatial-resolution and high-time-resolution phase-contrast video microscopy. Speckled images were characterized by evaluating the cross-correlation coefficient, speckle size, speckle contrast, and speckle quality of the images. The optimum parameters of the speckle tracking algorithm were determined by performing sensitivity analysis concerning computation time, effective mapping area, average contraction velocity, and strain. Furthermore, the hiPSC-CM response to adrenaline was evaluated to validate the sensitivity of the strain analysis algorithm. Then, we applied speckle tracking-based strain analysis to characterize the dynamic behavior of patient-specific hiPSC-CMs from the family members affected/unaffected by DiGeorge syndrome. Here, we report an efficient and manipulation-free method to analyze the contraction displacement vector and velocity field, contraction-relaxation strain rate, and contractile cycles. Implementation of this method allows for quantitative analysis of the contractile phenotype characteristics of hiPSC-CMs to distinguish possible cardiac manifestation of DiGeorge syndrome. © 2023 Wiley Periodicals LLC. Basic Protocol 1: Differentiation of iPSCs into iPSC-derived cardiomyocytes (iPSC-CMs) and metabolic selection of differentiated iPSC-CMs Support Protocol 1: Culture, maintenance, and expansion of human iPSCs Support Protocol 2: Immunohistochemistry of iPSC-CMs Basic Protocol 2: Time-lapse speckle imaging of iPSC-CMs and speckle quality characterization Support Protocol 3: Enhancement of local contrast of videos by applying contrast limited adaptive histogram equalization (CLAHE) to all frames Support Protocol 4: Evaluation of average speckle size Support Protocol 5: Evaluation of average speckle contrast Support Protocol 6: Determination of relative peak height, Pc(x), of consecutive images acquired from video microscopy of iPSC-CMs Basic Protocol 3: Speckle tracking-based analysis of beating iPSC-CMs Support Protocol 7: Validation of sensitivity of the speckle tracking analysis for mapping the contractility of iPSC-CMs Basic Protocol 4: Data extraction, visualization, and mapping of contractile cycles of iPSC-CMs.

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.

SMYD2 regulates vascular smooth muscle cell phenotypic switching and intimal hyperplasia via interaction with myocardin.

The SET and MYND domain-containing protein 2 (SMYD2) is a histone lysine methyltransferase that has been reported to regulate carcinogenesis and inflammation. However, its role in vascular smooth muscle cell (VSMC) homeostasis and vascular diseases has not been determined. Here, we investigated the role of SMYD2 in VSMC phenotypic modulation and vascular intimal hyperplasia and elucidated the underlying mechanism. We observed that SMYD2 expression was downregulated in injured carotid arteries in mice and phenotypically modulated VSMCs in vitro. Using an SMC-specific SMYD2 knockout mouse model, we found that SMYD2 ablation in VSMCs exacerbated neointima formation after vascular injury in vivo. Conversely, SMYD2 overexpression inhibited VSMC proliferation and migration in vitro and attenuated arterial narrowing in injured vessels in mice. SMYD2 downregulation promoted VSMC phenotypic switching accompanied with enhanced proliferation and migration. Mechanistically, genome-wide transcriptome analysis and loss/gain-of-function studies revealed that SMYD2 up-regulated VSMC contractile gene expression and suppressed VSMC proliferation and migration, in part, by promoting expression and transactivation of the master transcription cofactor myocardin. In addition, myocardin directly interacted with SMYD2, thereby facilitating SMYD2 recruitment to the CArG regions of SMC contractile gene promoters and leading to an open chromatin status around SMC contractile gene promoters via SMYD2-mediated H3K4 methylation. Hence, we conclude that SMYD2 is a novel regulator of VSMC contractile phenotype and intimal hyperplasia via a myocardin-dependent epigenetic regulatory mechanism.

Functional reserve and contractile phenotype of atrial myocardium from patients with atrial remodeling without and with atrial fibrillation.

Atrial contractility and functional reserve in atrial remodeling (AR) without (AR/-AF) or with atrial fibrillation (AR/+AF) are not well characterized. In this study, functional measurements were performed in right atrial muscle strips (n = 71) obtained from patients (N = 22) undergoing routine cardiac surgery with either no AR [left atrial (LA) diameter < 40 mm and no history of AF (hAF)], AR/-AF (LA diameter ≥ 40 mm, no hAF), or AR/+AF (hAF and LA diameter ≥ 40 mm or LAEF < 45%). AR/-AF and AR/+AF were associated with a prolongation of half-time-to-peak (HTTP, P < 0.001) and time-to-peak (TTP) contraction (P < 0.01) when compared with no AR. This effect was seen at baseline and during β-adrenergic stimulation with isoproterenol (Iso). Early relaxation assessed by half-relaxation time (HRT) was prolonged in AR/-AF (P = 0.03) but not in AR/+AF when compared with no AR at baseline, but this delay in relaxation in AR/-AF was attenuated with Iso. Late relaxation (τ) did not differ between AR/-AF and no AR but was consistently shorter in AR/+AF than no AR before (P = 0.04) and during Iso (P = 0.01), indicating accelerated late relaxation in AR/+AF. Relative force increase during Iso was higher (P = 0.01) and more dispersed (P = 0.047) in patients with AR/+AF. Relative adrenergic response was unaltered in the myocardium of patients with AR/-AF and AR/+AF. In conclusion, AR/-AF and AR/+AF are associated with changes in myocardial inotropic reserve and contractility. The changes are particularly pronounced in patients with AR/+AF, suggesting that the progression from AR/-AF to AR/+AF is associated with progressive alterations in atrial function that may contribute to arrhythmogenesis.NEW & NOTEWORTHY Mechanical alterations in atrial remodeling without (AR/-AF) and with atrial fibrillation (AR/+AF) have not been studied in detail in human atrial tissue preparations. To our knowledge, this is the first study to compare the mechanical phenotype and inotropic reserve in human atrial myocardial preparations from patients with no atrial remodeling, AR/-AF, and AR/+AF. We identify specific patterns of contractile dysfunction and heterogeneity for both, AR/-AF and AR/+AF, indicating the progression of atrial disease.