Smooth Muscle Cell Phenotype Research Articles

Stress, Vascular Smooth Muscle Cell Phenotype and Atherosclerosis: Novel Insight into Smooth Muscle Cell Phenotypic Transition in Atherosclerosis.

Our work is to establish more distinct association between specific stress and vascular smooth muscle cells (VSMCs) phenotypes to alleviate atherosclerotic plaque burden and delay atherosclerosis (AS) progression. In recent years, VSMCs phenotypic transition has received significant interests. Different stresses were found to be associated with VSMCs phenotypic transition. However, the explicit correlation between VSMCs phenotype and specific stress has not been elucidated clearly yet. We discover that VSMCs phenotypic transition, which is widely involved in the progression of AS, is associated with specific stress. We discuss approaches targeting stresses to intervene VSMCs phenotypic transition, which may contribute to develop innovative therapies for AS.

A comparative study of smooth muscle cell characteristics and myofibroblasts in processus vaginalis of pediatric inguinal hernia, hydrocele and undescended testis

BackgroundCongenital inguinal hernia, hydrocele and undescended testis (UDT) are associated with patent processus vaginalis. The smooth muscles present in the processus vaginalis aid in the descent of the testis and undergo programmed cell death after testicular descent leading to obliteration. The persisting amount of smooth muscle in the processus vaginalis influences the clinical outcome as inguinal hernia, hydrocele or UDT. Therefore, a study was conducted to evaluate the processus vaginalis in these three conditions to observe the presence and phenotype of smooth muscle cells and the presence of myofibroblasts.Materials and methodsThe processus vaginalis sacs in patients with inguinal hernia, hydrocele and UDT were examined using light microscopy for the presence and distribution of smooth muscle cells and immunohistochemical staining for vimentin, desmin, and α-smooth muscle actin (SMA) to identify the smooth muscle phenotype. Transmission electron microscopy was also performed in all the sacs to observe the presence of myofibroblasts.ResultsSeventy-eight specimens of processus vaginalis (from seventy-four patients), distributed as 47%, 27%, and 26% as inguinal hernia, hydrocele and UDT respectively, were included in the study. The sacs from inguinal hernia and hydrocele had significantly more presence of smooth muscles distributed as multiple smooth muscle bundles (p < 0.001). Desmin and SMA staining of smooth muscle cells was observed in significantly more sacs from hydrocele, followed by inguinal hernia and UDT (p < 0.001). The sacs from UDT had a significant presence of striated muscles (p = 0.028). The sacs from inguinal hernia had a significant presence of myofibroblasts, followed by hydrocele and UDT (p < 0.001) and this significantly correlated with the light microscopy and immunohistochemical features. The processus vaginalis sacs from four female patients did not differ statistically from the male inguinal hernia sacs in any of the above parameters.ConclusionThe processus vaginalis sacs in pediatric inguinal hernia, hydrocele and undescended testis differ in the presence, distribution and phenotype of smooth muscles and the presence of myofibroblasts. The clinical presentations in these entities reflect these differences.

Smooth muscle cell-specific deletion of S100A4 modifies smooth muscle cell fate and inflammation in murine atherosclerotic lesions

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Swiss National Science Foundation (SNSF) S100A4, a calcium-binding protein, is crucial in smooth muscle cell (SMC) phenotypic switch, yet its role in atherosclerotic plaque development and SMC plasticity remains unclear. Our previous experiments using an S100A4 neutralizing antibody approach in ApoE-/- atherosclerotic-prone mice showed reduced atherosclerotic burden but did not establish a direct link between the various S100A4-expressing cells and atherosclerosis. Herein, we show that aortic Oil RedO staining in ApoE-/-; S100A4-/- mice subjected to a 12-week high-cholesterol-diet (HCD) revealed reduced lesion areas compared to ApoE-/- mice (Figure 1, from 21.29% of the total aorta in ApoE-/-; S100A4+/+ mice to 13.27% in ApoE-/-; S100A4-/- mice), highlighting a pivotal role for S100A4 in atherosclerotic plaque development. We then used a lineage tracing ApoE-/- mouse model, in which we induced an SMC-specific deletion of S100A4 (SMC-S100A4Δ/Δ). After 12 weeks of HCD, SMC-S100A4Δ/Δ and control mice (SMC-S100A4wt/wt) were sacrificed, and aortas were processed for en face Oil Red O staining, immunohistochemistry, and single-cell RNA sequencing (scRNA-seq). SMC-specific deletion of S100A4 reduced the necrotic core area (from 29.75% of total plaque area in SMC-S100A4wt/wt to 18.23% in SMC-S100A4Δ/Δ mice) without affecting total atherosclerotic plaque size suggesting a more potent impact on plaque composition. ScRNA-seq analysis from SMC-S100A4Δ/Δ and SMC-S100A4wt/wt mice showed that the inflammatory macrophage-like SMC phenotype was highly suppressed in the plaque and associated with increased SMC repair phenotypes as well as a global reduction of myeloid inflammatory cells. SMCs also retained specific contractile SMC markers, namely Acta2 and Myh11 (fold change of 2.285 and 2.492, respectively) hinting towards a more stable fibrous cap. Immunofluorescence staining on aortic roots plaque (Figure 2) confirmed those results with an increase of SMCs (from 11.02% to 16.18%) as well as a-smooth muscle actin (a-SMA, Acta2)-positive SMCs (from 3.25% to 5.1%) in SMC-S100A4 Δ/Δ mice. Furthermore, the Gene Set Enrichment Analysis (GSEA) of scRNAseq data revealed that, in SMC-S100A4Δ/Δ mice, genes related to mitochondrial metabolism and oxidative respiration were highly downregulated in all SMC clusters. We investigated SMC mitochondrial fitness in vitro and showed that S100A4-/- SMCs have an increased basal oxygen consumption rate and an increased proton leak (fold change of 1.37 and 1.96 respectively) suggestive of differences in cellular metabolic adaptability. In conclusion, our research emphasizes the significant role of S100A4 in plaque development, demonstrating how SMC-derived S100A4 knockdown affects plaque evolution, reducing inflammation, and promoting stability likely through influencing SMC phenotypic switch through metabolic pathways.

#2052 Reciprocal interplay between miR-155-5p and SOCS1 in the development of renal and vascular damage in experimental diabetes

Abstract Background and Aims Chronic kidney disease and atherosclerosis are common vascular complication of diabetes and a global health issue. Hyperglycemia, dyslipidemia, and cytokines activate Janus kinase/signal transducers and activators of transcription (JAK/STAT) signaling pathway to induce mediators of inflammation and oxidative stress, which are critical events in the progression of renal and vascular damage in diabetic patients. MicroRNAs are small, non-coding molecules and key regulators of gene expression. There is evidence of microRNA-155 (miR-155) involvement in diabetes complications, but the underlying mechanisms are unclear. In this study, gain- and loss-of-function experiments were applied to investigate the interplay between miR-155-5p and suppressor of cytokine signaling 1 (SOCS1) in the regulation of JAK/STAT pathway during renal and vascular injury in diabetes. Method Mesangial, tubuloepithelial, and vascular smooth muscle cells were transfected with miR-155-5p mimic or inhibitor, SOCS1 expression plasmid or siRNA, before stimulation with cytokines or high-glucose. Apolipoprotein E deficient mice with streptozotocin-induced diabetes were treated with either SOCS1-encoding adenovirus or miR-155-5p inhibitor. Samples were analyzed for the expression of miR-155-5p, SOCS1, and mediators of renal and vascular damage. Results In diabetic mice, the expression of miR-155-5p correlated inversely with SOCS1 levels and positively with markers of renal dysfunction, atherosclerosis, inflammation and oxidative stress. In renal cells, transfection with miR-155-5p mimic downregulated SOCS1, activated STAT1 and cytokine expression, and stimulated cell proliferation and migration. Mimic transfection also promoted the transition from contractile to synthetic phenotype in vascular smooth muscle cells. Conversely, both miR-155-5p antagonism and SOCS1 overexpression protected cells from inflammatory damage. In vivo SOCS1 gene delivery in diabetic mice decreased miR-155-5p and prevented kidney and vascular injury. Finally, therapeutic inhibition of miR-155-5p alleviates albuminuria, renal inflammation and fibrosis in diabetic mice, and also reduced atherosclerosis burden and improved plaque stability. Conclusion The modulation of miR-155/SOCS1 axis protects against diabetic renal and vascular damage in mice, thus highlighting its potential as therapeutic target for chronic complications of diabetes.

#1514 Elevated FGF23 increases systolic, and diastolic blood pressure, and pulse pressure in non-dialysis CKD patients

Abstract Background and Aims Arterial stiffness is associated with high blood pressure. Elevated fibroblast growth factor 23 (FGF23) has been shown to produce changes in the phenotype of vascular smooth muscle cells that may cause an increase in arterial stiffness and an impairment of vascular function. Thus, we aimed to evaluate whether, in g5 non-dialysis CKD patients, higher concentration FGF23 is associated with elevated systolic (SBP), diastolic blood pressure (DBP), and pulse pressure (PP). Method We included 159 g5 non-dialysis CKD patients. Generalized additive models analyzed the association between intact FGF23, SBP, DBP, and PP. The body composition measurement was used to evaluate overhydration (OH). Given the potential non-linear relationship between iFGF23, with the other variables, iFGF23 was categorized into tertiles (T1 ≤ 389 pg/ml, T2 = 389—517 pg/ml, and T3 = &amp;gt;517 pg/ml). Results The mean age was 65.2 ± 14.7 years. 46% (n = 73) were female. The mean values of SBP and DBP were 158.8 ± 21.3 mmHg, and 87.2 ± 12.3 mmHg respectively, and the PP was 76.6 ± 20 mmHg. The median concentration of iFGF23 was 468.3 (268.8—904.9) pg/ml. It was observed a positive correlation between iFGF23 tertiles and SBP (p &amp;lt; 0.001), DBP (&amp;lt;0.01), PP (p = 0.02), and OH (p &amp;lt; 0.01) (Fig. 1). Multivariate generalized additive models showed an independent association of iFGF23 with SBP (Beta 5.16, CI 34-68), DBP (Beta 38.7, CI 24-53), and PP (Beta 36.3, CI 22.2-50.4). This association was not influenced by OH (%). Residual diuresis did not attenuate the association of iFGF23 with SBP, DBP, and PP. Conclusion Elevated FGF23 was associated with higher SBP, DBP, and PP in g5 non-dialysis CKD patients. This association was not modified by OH and residual diuresis.

#1624 The association between serum beclin 1 level and the presence of aortic valve calcification among individuals on hemodialysis

Abstract Background and Aims The autophagy pathway, a crucial regulator of cellular health and metabolism, plays a fundamental role in maintaining healthy blood vessel function. Studies have established its critical involvement in endothelial cell stability, vascular smooth muscle cell (VSMC) phenotype control, and VSMC calcium balance. Recent evidence, further, underlines autophagy's direct protective role against vascular calcification. It has been shown that autophagy can modulate different cardiovascular pathologies, including valvular calcification. We aimed to explore the potential link between the protein beclin 1 and heart valve calcification in dialysis patients. Method We compared two groups of 51 haemodialysis patients each, defined by the presence (Group 1) or absence of valve calcification (Group 2) on echocardiograms. Both groups underwent beclin 1 level measurements and other assessments (lipid profile). Cardiac valve calcification was diagnosed through echocardiography by identifying dense echoes exceeding 1 millimeter in thickness on one or more aortic valve cusps. The severity of calcification was then classified into three stages: Mild: Calcification thickness ranged from 1 to 3 millimeters and involved less than 50% of the valve leaflet. Moderate: Calcification thickness exceeded 3 millimeters but still affected less than half of the valve leaflet. Severe: Calcification thickness surpassed 3 millimeters and encompassed more than 50% of the valve leaflet. Results Our analysis demonstrated a statistically significant increase in beclin 1 levels in Group 2 compared to Group 1 (p&amp;lt;0.001), a striking relationship between lower beclin 1 levels and more severe valve calcification. Interestingly, a specific beclin 1 cutoff below 35.5 ng/ml offered the highest accuracy (98% sensitivity and 92% specificity) in predicting valve calcification. Notably, significant differences were found in lipid profiles (Analysis of the lipid profile revealed a striking trend in Group I, with significant elevations in cholesterol, triglycerides, and LDL. Conversely, HDL levels were significantly higher in Group II). and prevalence of heart disease between the groups. Analysis of IHD prevalence across the two groups yielded a striking result. Group 1 displayed a significantly higher proportion of individuals with IHD (17 cases) compared to group 2 (3 cases), with a statistically significant difference (p&amp;lt;0.001). Conclusion Based on these results, it appears promising to integrate serum Beclin 1 measurements into a risk assessment model for the development of heart valve calcification in dialysis patients.

The Histone Demethylase JMJD3 Regulates Smooth Muscle Cell Phenotype during Macrophage-mediated Inflammation

The Histone Demethylase JMJD3 Regulates Smooth Muscle Cell Phenotype during Macrophage-mediated Inflammation

Reduction of Abdominal Aortic Aneurysm Rupture by Modulating Smooth Muscle Cell Phenotype Switching

Reduction of Abdominal Aortic Aneurysm Rupture by Modulating Smooth Muscle Cell Phenotype Switching

Somatic PDGFRB activating variants promote smooth muscle cell phenotype modulation in intracranial fusiform aneurysm

BackgroundThe fusiform aneurysm is a nonsaccular dilatation affecting the entire vessel wall over a short distance. Although PDGFRB somatic variants have been identified in fusiform intracranial aneurysms, the molecular and cellular mechanisms driving fusiform intracranial aneurysms due to PDGFRB somatic variants remain poorly understood.MethodsIn this study, single-cell sequencing and immunofluorescence were employed to investigate the phenotypic changes in smooth muscle cells within fusiform intracranial aneurysms. Whole-exome sequencing revealed the presence of PDGFRB gene mutations in fusiform intracranial aneurysms. Subsequent immunoprecipitation experiments further explored the functional alterations of these mutated PDGFRB proteins. For the common c.1684 mutation site of PDGFRβ, we established mutant smooth muscle cell lines and zebrafish models. These models allowed us to simulate the effects of PDGFRB mutations. We explored the major downstream cellular pathways affected by PDGFRBY562D mutations and evaluated the potential therapeutic effects of Ruxolitinib.ResultsSingle-cell sequencing of two fusiform intracranial aneurysms sample revealed downregulated smooth muscle cell markers and overexpression of inflammation-related markers in vascular smooth muscle cells, which was validated by immunofluorescence staining, indicating smooth muscle cell phenotype modulation is involved in fusiform aneurysm. Whole-exome sequencing was performed on seven intracranial aneurysms (six fusiform and one saccular) and PDGFRB somatic mutations were detected in four fusiform aneurysms. Laser microdissection and Sanger sequencing results indicated that the PDGFRB mutations were present in smooth muscle layer. For the c.1684 (chr5: 149505131) site mutation reported many times, further cell experiments showed that PDGFRBY562D mutations promoted inflammatory-related vascular smooth muscle cell phenotype and JAK-STAT pathway played a crucial role in the process. Notably, transfection of PDGFRBY562D in zebrafish embryos resulted in cerebral vascular anomalies. Ruxolitinib, the JAK inhibitor, could reversed the smooth muscle cells phenotype modulation in vitro and inhibit the vascular anomalies in zebrafish induced by PDGFRB mutation.ConclusionOur findings suggested that PDGFRB somatic variants played a role in regulating smooth muscle cells phenotype modulation in fusiform aneurysms and offered a potential therapeutic option for fusiform aneurysms.

Defining the miRnome of Saphenous Vein Smooth Muscle Cells from Patients with Type 2 Diabetes Mellitus

Type 2 diabetes mellitus (T2DM) patients suffer premature development of cardiovascular disease and commonly require cardiac revascularization using the autologous saphenous vein (SV). Smooth muscle cells (SMCs) are the principal cell type within the vascular wall and are dysfunctional in T2DM SV-SMCs, yet the mechanisms underpinning this are incompletely understood. The purpose of this study was to interrogate differential microRNA (miRNA) expression in SV-SMCs to enhance our understanding of T2DM SV-SMC phenotypic change. miRNA expression in primary human SV-SMCs from T2DM and non-diabetic (ND) donors was determined using an array (n = 6 each of ND and T2DM SV-SMCs). Differentially expressed miRNAs were ranked, and functional annotation of the 30 most differentially expressed miRNAs using DAVID and KEGG analysis revealed pathways related to SMC phenotype, including proliferation, migration, cytokine production and cell signaling. After selecting miRNAs known to be involved in SMC phenotypic regulation, miR-17, miR-29b-2, miR-31, miR-130b and miR-491 were further validated using qRT-PCR (n = 5 each of ND and T2DM SV-SMC), with miR-29b-2 subsequently being removed from further investigation. Potential mRNA targets were identified using mirDIP. Predicted target analysis highlighted likely dysregulation in transcription, epigenetic regulation, cell survival, intracellular signaling and cytoskeletal regulation, all of which are known to be dysfunctional in T2DM SV-SMCs. In conclusion, this paper identified four miRNAs that are dysregulated in T2DM SV-SMCs and are implicated in functional changes in the behavior of these cells. This provides a step forward in our understanding of the molecular and epigenetic regulation of vascular dysfunction in T2DM.

Intracranial aneurysm circulating exosome-derived LncRNA ATP1A1-AS1 promotes smooth muscle cells phenotype switching and apoptosis.

Exosomal long non-coding RNAs (LncRNAs) play a crucial role in the pathogenesis of cerebrovascular diseases. However, the expression profiles and functional significance of exosomal LncRNAs in intracranial aneurysms (IAs) remain poorly understood. Through high-throughput sequencing, we identified 1303 differentially expressed LncRNAs in the plasma exosomes of patients with IAs and healthy controls. Quantitative real-time polymerase chain reaction (qRT-PCR) verification confirmed the differential expression of LncRNAs, the majority of which aligned with the sequencing results. ATP1A1-AS1 showed the most significant upregulation in the disease group. Importantly, subsequent in vitro experiments validated that ATP1A1-AS1 overexpression induced a phenotype switching in vascular smooth muscle cells, along with promoting apoptosis and upregulating MMP-9 expression, potentially contributing to IAs formation. Furthermore, expanded-sample validation affirmed the high diagnostic value of ATP1A1-AS1. These findings suggest that ATP1A1-AS1 is a potential therapeutic target for inhibiting IAs progression and serves as a valuable clinical diagnostic marker.

Early matrix softening contributes to vascular smooth muscle cell phenotype switching and aortic dissection through down-regulation of microRNA-143/145

Thoracic aortic dissection (TAD) is characterized by extracellular matrix (ECM) dysregulation. Aberrations in the ECM stiffness can lead to changes in cellular functions. However, the mechanism by which ECM softening regulates vascular smooth muscle cell (VSMCs) phenotype switching remains unclear. To understand this mechanism, we cultured VSMCs in a soft extracellular matrix and discovered that the expression of microRNA (miR)-143/145, mediated by activation of the AKT signalling pathway, decreased significantly. Furthermore, overexpression of miR-143/145 reduced BAPN-induced aortic softening, switching the VSMC synthetic phenotype and the incidence of TAD in mice. Additionally, high-throughput sequencing of immunoprecipitated RNA indicated that the TEA domain transcription factor 1 (TEAD1) is a common target gene of miR-143/145, which was subsequently verified using a luciferase reporter assay. TEAD1 is upregulated in soft ECM hydrogels in vitro, whereas the switch to a synthetic phenotype in VSMCs decreases after TEAD1 knockdown. Finally, we verified that miR-143/145 levels are associated with disease severity and prognosis in patients with thoracic aortic dissection. ECM softening, as a result of promoting the VSMCs switch to a synthetic phenotype by downregulating miR-143/145, is an early trigger of TAD and provides a therapeutic target for this fatal disease. miR-143/145 plays a role in the early detection of aortic dissection and its severity and prognosis, which can offer information for future risk stratification of patients with dissection.

Use of iPSC-Derived Smooth Muscle Cells to Model Physiology and Pathology.

The implementation of human induced pluripotent stem cell (hiPSC) models has introduced an additional tool for identifying molecular mechanisms of disease that complement animal models. Patient-derived or CRISPR/Cas9-edited induced pluripotent stem cells differentiated into smooth muscle cells (SMCs) have been leveraged to discover novel mechanisms, screen potential therapeutic strategies, and model in vivo development. The field has evolved over almost 15 years of research using hiPSC-SMCs and has made significant strides toward overcoming initial challenges such as the lineage specificity of SMC phenotypes. However, challenges both specific (eg, the lack of specific markers to thoroughly validate hiPSC-SMCs) and general (eg, a lack of transparency and consensus around methodology in the field) remain. In this review, we highlight the recent successes and remaining challenges of the hiPSC-SMC model.

Abstract 103: Acly Inhibition As A Novel Therapeutic Approach For Vascular Remodeling In Coronary Artery Disease

Coronary artery (CoA) disease (CAD) is characterized by neointimal hyperplasia (NH), which is driven by a cancer-like pro-proliferative phenotype of smooth muscle cells (SMCs). A metabolic shift towards glycolysis and changes in the epigenetic landscape contribute to this abnormal phenotype. ATP Citrate Lyase (ACLY) is an enzyme that plays a role in promoting the Warburg effect, lipid synthesis, and chromatin remodeling in cancer. However, its role in CAD remains unknown. We hypothesized that ACLY is upregulated in CAD and supports the abnormal phenotype of CAD-CoASMCs. To investigate this hypothesis, we measured ACLY expression in human distal coronary arteries and isolated CoASMCs from CAD patients. We found increased expression and activation of ACLY in CAD-CoASMCs, with preferential localization in the nucleus. Inhibition of ACLY using BMS-303141 or siACLY decreased CAD-CoASMCs proliferation and survival. ACLY inhibition also reduced glycolysis markers and increased mitochondrial respiration. Additionally, ACLY inhibition lowered cholesterol levels and lipid droplet accumulation in CAD-CoASMCs. Further analysis showed that ACLY promotes nuclear acetyl-CoA production, leading to acetylation of specific histone proteins and GCN5-mediated transcriptional activation of genes involved in cell cycle progression. The transcription factor FOXM1 appeared to mediate this genetic signature. In vivo , pharmacological inhibition of ACLY using BMS-303141 attenuated NH in a rat model of carotid injury (CI). SMC-specific Acly K.O mice were protected against CI-induced NH. Consistently, tamoxifen-induced SMC-specific Acly deletion mitigated NH in mice subjected to CI. The therapeutic effects were associated with reduced histone acetylation. To assess the translational potential of our findings, we tested the effects of ACLY inhibition on ex vivo human coronary artery and saphenous vein explants stimulated with growth factors cocktail. We found that ACLY inhibition prevent NH development, supporting the potential of ACLY as a therapeutic target. In conclusion, our study reveals that ACLY plays a critical role in vascular remodeling in CAD and its pharmacological inhibition may represent a novel avenue as therapeutic treatment.

Abstract 2150: PTEN Protects Against Vascular Smooth Muscle Cell Pro-inflammatory Dedifferentiation Through Metabolic Re-wiring

Vascular smooth muscle cells (SMCs) play a critical role in intimal hyperplasia in atherosclerosis and restenosis. SMCs in diseased arteries exhibit a modulated phenotype with reduced contractile gene expression, elevated proliferation, and a proinflammatory/profibrotic phenotype. Metabolic reprogramming accompanies and is essential for SMC phenotypic modulation. Our group previously demonstrated that the tumor suppressor gene, PTEN, contributes to the maintenance of the SMC contractile phenotype. Analysis of human GTEx project data established a negative correlation between expression of PTEN and inflammatory genes in human arterial tissues. As a metabolic regulator, the function of PTEN in SMC metabolism has not been examined. We subjected SMC lineage tracing mice with systemic (sPTEN) and inducible, SMC-specific (iPTEN) PTEN overexpression to disease models of atherosclerosis and carotid artery (CA) injury. Compared to control mice, sPTEN and iPTEN mice are protected from atherosclerotic lesion formation and ligation-induced neointima formation. The observed vascular protection effect of PTEN was associated with reduced inflammation and reduced expression of key regulators of glycolysis, including GLUT1, HIF1a and PKM2, which were up-regulated in dedifferentiated SMCs. Consistently, unbiased metabolomics analysis confirmed that CA injury induced a SMC metabolic phenotype, including accumulation of pyruvate, reduction of OXPHOS, and increased fatty acid synthesis, which was rescued in iPTEN mice. Through high throughput screening, we previously identified and validated 5-azacytidine (5-aza) as potent transcriptional activator of PTEN expression. 5-aza reversed injury-induced SMC dedifferentiation in WT, but not PTEN inducible KO (PTEN iKO) mice. Our new scRNA-seq data further suggest that 5-aza inhibited injury-induced SMC metabolic reprogramming and dedifferentiation in a PTEN-dependent manner. Altogether, the data support that PTEN antagonizes the metabolic changes in SMC dedifferentiation and thereby maintains a contractile SMC phenotype. Pharmacological induction of PTEN by 5-aza can serve as a viable approach to rescue SMC metabolic reprogramming and phenotypic modulation in vascular disease.

Piezo1 mediated calcium-calcineurin signaling pathway regulates gastrointestinal smooth muscle cell phenotype in a stiffness dependent manner

Background: Gastrointestinal (GI) disorders like chronic constipation are more prevalent with aging. Aging GI tract becomes stiffer and exhibits delayed GI transit. Smooth muscle cells (SMCs) are involved in controlling GI transit and show reduced contractility with age. Piezo1 is a mechanically activated ion channel that responds to membrane tension by opening its pore to allow flow of ions such as calcium (Ca2+) and regulates various cellular processes through Ca2+-calcineurin signaling pathway. We wondered GI stiffness changes might control SMC contractile to non-contractile phenotype through Piezo1. Objective: To determine how substrate stiffness regulates GI SMC contractile phenotype through Piezo1. Hypothesis: SMC Piezo1 senses GI tissue stiffness changes and alters SMC phenotype. Methods: Pathway analysis on human colon single cell sequencing data was performed using Gene Set Enrichment Analysis (GSEA) pre-ranked module with publicly available gene-sets from Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Immortalized human jejunal SMCs (HuSMCs) and freshly dissociated SMCs from control (CTRL, Myh11-creERT2) and SMC specific Piezo1 knockout [Myh11-creERT2xPiezo1 Flox (Piezo1-KO)] mouse colons (primary SMCs) were cultured on soft (1kPa) and stiff (50kPa) substrates to model age-dependent shifts in intestinal stiffness for 48 hours either in the presence/absence of Piezo1 siRNA, Piezo1 agonist (Yoda1, 1μM), and calcineurin blocker (Cyclosporin A, CsA, 1μM) and used for Ca2+ imaging, RT-qPCR and immunostaining. Results: GSEA showed Piezo1+ve SMCs were significantly enriched in pathways involved in the regulation of Ca2+ signaling compared to Piezo1−ve SMCs (p&lt;0.05). HuSMCs and primary SMCs showed increased Piezo1 expression (HuSMCs:1.1±0.2-fold, n=8, p&lt;0.05; primary SMCs:2.1±0.1-fold, n=3, p&lt;0.05) and cytoplasmic Ca2+ (3.6-fold, n=10, p&lt;0.05) in response to Yoda1 on stiff substrates compared to soft. HuSMCs on stiff substrate showed decreased expression of contractile SMC markers smoothelin ( SMTN:0.7±0.2-fold, n=7, p&lt;0.05) and transgelin ( TAGLN:0.6±0.1-fold, n=7, p&lt;0.05) which was rescued by Piezo1 siRNA treatment ( SMTN:1.2±0.1-fold, n=2-7, p&lt;0.05; TAGLN:1.15±0.02-fold, n=2-7, p&lt;0.05) (Piezo1 is necessary). Stimulation by Yoda1 of HuSMCs on the soft substrate resulted in decreased expression of SMTN (0.7±0.3-fold, n=2-7, p&lt;0.05) and TAGLN (0.7±0.1-fold, n=2-7, p&lt;0.05) (Piezo1 is suffcient). CTRL primary SMCs on stiff substrate showed decreased expression of Smtn (0.4±0.1-fold, n=3, p&lt;0.05) and Tagln (0.3±0.2-fold, n=3, p&lt;0.05) compared to SMCs on soft substrate which was reversed when SMCs from Piezo1-KO mice were cultured on these substrates ( Smtn:1.8±0.5-fold, n=3, p&lt;0.05; Tagln:2.4±0.07-fold, n=3, p&lt;0.05). Treatment of CsA in HuSMCs cultured on stiff substrate also rescued from loss of SMTN (1.3±0.1-fold, n=3, p&lt;0.05) and TAGLN (1.7±0.3-fold, n=3, p&lt;0.05) expression and prevented nuclear factor of activated T cells (NFAT) nuclear translocation. Summary and Conclusion: GI SMC Piezo1 senses stiffness changes and regulates SMC phenotype through Ca2+-calcineurin signaling pathway. Targeting Piezo1 might be protective from age induced reduced GI SMC contractility. NIH DK052766, DK123549. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Abstract 1054: Toll-like Receptor 4 Is A New Regulator Of Smooth Muscle Cell Phenotypic Transitions

Objectives: There is growing evidence that smooth muscle cell ( SMC ) phenotypic transitions have a critical role in cardiovascular pathologies, including atherosclerosis. However, molecular mechanisms regulating different aspects of these transitions are still not fully elucidated. We previously found that the pluripotency factor OCT4 plays a protective role in SMC in atherogenesis and neointioma formation after vascular injury. Using a bioinformatics approach, we identified Toll-like receptor 4 ( TLR4 ), an integral component of the innate immune system, pivotal in eliciting inflammatory responses, as an indirect target of OCT4 in SMC. However, it is not yet elucidated whether OCT4/TLR4 axis has a role in SMC transitions. Methods and Results: First, we used blocking siRNA against Oct4 and different downstream targets of the TLR4 signaling ( Trif , Irf3 ), as well as a TLR4 inhibitor TAK242 (Resatorvid) in cultured mouse aortic SMC treated with the oxidized phospholipid, POVPC. These experiments demonstrated that blocking TLR4 signaling in wild-type SMC resulted in suppression of SMC contractile genes and up-regulation of LGALS3 (SMC transition marker). In contrast, TAK242 treatment decreased LGALS3 levels in OCT4 deficient SMC, indicating that TLR4, at least in part, is responsible for the SMC phenotype in OCT4 deficient SMC. Next, using the bioinformatics approach and Chromatin Immunoprecipitation assays, we identified the EST Proto-oncogene 1 ( ETS1 ) transcriptional factor as a target of OCT4 that directly regulates TLR4. Interestingly, on the other hand, we found that overexpression of TLR4 led to OCT4 activation in SMC, and, oppositely, the inhibition of TLR4 signaling by TAK242 resulted in significant decreases in the POVPC-induced OCT4 activation, indicating that TLR4 signaling is critical for OCT4 activation in SMC. Using an SMC-lineage tracing mouse model combined with a TLR4-IRES-YFP reporter, we demonstrated that TLR4 is highly expressed in the healthy arteries of young mice but not in the phenotypically modulated SMC within the atherosclerotic plaques. Conclusions: These results suggest a negative feedback loop between TLR4 and OCT4 regulating SMC phenotypic transitions.

Abstract 126: Reduction Of Abdominal Aortic Aneurysm Rupture By Modulating Smooth Muscle Cell Phenotype Switching

Background: Vascular smooth muscle cell (SMC) loss and phenotype switch promote abdominal aortic aneurysm (AAA) development, yet whether strategically enhancing positive aortic wall remodeling can reduce AAA rupture is unknown. We hypothesize inhibiting necroptosis signaling in SMCs may drive differentiation into resilient and regenerative phenotypes, thus reinforcing AAA wall integrity and rupture resistance. Methods: We developed Cre-loxP transgenic mice with SMC-specific loss-of-function mutation of the necroptosis regulatory gene, Ripk3 ( Ripk3 Δ). AAAs were induced using the topical elastase plus β-aminopropionitrile murine model. Results: Rupture-free survival at 56-days post-AAA induction was drastically improved with both homozygous and heterozygous loss of SMC RIPK3 function ( Ripk3 Δ HO : 100%, Ripk3 Δ Het : 92.3% versus Ripk3 Δ WT : 47.1%). Ripk3 mutant aortas demonstrated rupture-resistance despite substantial aneurysmal dilations ranging 127-527%, and morphologically displayed significant medial thickening with SMC expansion. Bulk RNA-sequencing revealed stark transcriptional changes between 14-day Ripk3 Δ HO and Ripk3 Δ WT aortas. Both genotypes showed typical aneurysmal processes, however, Ripk3 depletion greatly reduced aneurysm-induced inflammatory responses. We identified 54 uniquely altered transcripts in mutant tissues, coding for cell cycle regulators and extracellular matrix proteins. Ongoing tissue analysis will determine whether regenerative, matrix-producing SMCs vary among human AAAs and healthy aortas. Conclusions: AAA rupture is significantly reduced by inhibiting RIPK3 in SMCs, likely by promoting positive structural adaptations and down-regulating classic pathways of aneurysmal degeneration. We postulate pharmacologically inhibiting RIPK3-mediated SMC modulation could be a novel approach in AAA patient management, to reduce rupture risk from diagnosis to optimal timing of surgical repair.

Abstract 2141: An IL12/IL23 Positive Feedback Loop Modulates Smooth Muscle Differentiation Via Setd4 During Macrophage-mediated Inflammation

Diabetic patients have increased risk of vascular disease (e.g., atherosclerosis), which is driven by macrophage-mediated inflammation. In diseases such as atherosclerosis, smooth muscle cells (SMC) undergo phenotypic modulation from a mature, contractile to a synthetic phenotype, thus leading to increased neointima formation. We hypothesize that pro-inflammatory macrophages as in the setting of diabetes epigenetically pattern SMC during vascular disease. In this study, we use single cell-RNA sequencing (scRNA-seq) of human arteries, loss of function experiments, and mouse models of disease to identify epigenetic mechanisms that regulate SMC phenotype. We identified the H3K4 and H3K9 histone lysine methyltransferase Setd4, which was increased in aortic SMC from diabetic mice and in our scRNA-seq dataset from human atherosclerotic arteries. siRNA mediated knockdown of Setd4 in mouse aortic SMC increased expression of the early SMC differentiation markers, Acta2 and Tagln (p&lt;0.05). To model the pro-inflammatory environment in vitro, supernatant from LPS-stimulated macrophages increased Setd4 expression and inhibited smooth muscle gene expression ( Acta2, Tagln, Cnn1, Myh11 ), which was reversed by siRNA-mediated knockdown of Setd4 in SMC (p&lt;0.05). IL23 increased Setd4 expression in SMC and enrichment at smooth muscle gene promoters, while deceasing SMC-specific gene expression (p&lt;0.05). Treatment of SMC with an IL23 receptor neutralizing antibody prevented downregulation of SMC gene expression by macrophage supernatant (p&lt;0.05). Intriguingly, ELISA of mouse aortic SMC supernatant revealed that IL23 increased SMC secretion of IL12, which also inhibited SMC gene expression via Setd4 (p&lt;0.05). In conclusion, we demonstrate that pro-inflammatory macrophage IL23 represses smooth muscle gene expression via SETD4, thereby shifting the SMC to a synthetic, diseased phenotype. IL23 also stimulates vascular SMC secretion of IL12, which further increases production of inflammatory cytokines from macrophages and leads to additional repression of smooth muscle gene expression. Thus, targeting the IL23-SETD4 axis in SMC may be a potential therapy for the treatment of atherosclerosis, especially in patients who also have diabetes.

Abstract 1124: Sympathetic Denervation Models In Murine Femoral Arteries: Acute To Chronic Effects Of 6-hydroxydopamine

Introduction: The autonomic nervous system (ANS) drives blood flow regulation in peripheral arteries. This study aims to develop novel models of sympathetic denervation in peripheral arteries and to characterize subsequent vascular remodeling. We hypothesize that sympathetic denervation of murine femoral arteries can be achieved through local administration of neurotoxin 6-hydroxydopamine (6-OHDA). Methods: BALB/c mice underwent local administration of 6-OHDA to the left femoral artery, while the contralateral artery received vehicle solution. Two approaches were tested: (1) Acute: a one-time topical application following surgical exposure of femoral arteries (N=8, male, Fig. A ), and (2) Chronic: weekly subcutaneous injections near the femoral arteries (N=11, male and female, Fig. B ). Hindlimb perfusion was assessed with laser Doppler imaging, and arterial structure and remodeling were evaluated with histology and immunohistochemistry at one, two, or four weeks. Results: One-time 6-OHDA application (Acute) led to temporary femoral artery denervation (reduction in tyrosine hydroxylase) for one week ( Fig. C – D ), with inflammation observed in both 6-OHDA and vehicle-treated arteries. No vascular wall remodeling was observed after temporary denervation. Weekly subcutaneous 6-OHDA injections (Chronic) resulted in persistent denervation throughout the four-week period in male mice, while female mice displayed variable outcomes ( Fig. E – F ). Sustained sympathetic denervation in the chronic model led to reduced hindlimb blood perfusion at low core temperatures ( Fig. G – H ), though no significant differences were detected in vascular smooth muscle cell phenotype or extracellular matrix composition. Conclusions: Local administration of 6-OHDA is an effective means of peripheral artery sympathetic denervation with controllable duration. This innovative approach of targeting the ANS unveils new prospects for advancing vascular therapies.