Induction Of Endothelial-to-mesenchymal Transition Research Articles

Abstract 4122717: An Epigenetic Drug, GSK126 Mitigates Endothelial to Mesenchymal Transition Attenuating Atherosclerosis in Diabetes

Background: Endothelial to mesenchymal transition (EndMT) involves transformation of an endothelial to mesenchymal like cellular state. Recent studies implicate EndMT in atherosclerosis development. Diabetes is associated with both EndMT as well as accelerated atherosclerosis. Experimental evidence supports the use of epigenetic drugs that act on relevant epigenetic mechanisms to attenuate atherosclerosis. Recently, inhibition of a histone methyltransferase Enhancer of zest homolog 2 (EZH2) with GSK-126 attenuated atherosclerosis development. However, the role of EZH2 in induction of EndMT in diabetes induced atherosclerosis is not known. Methods: An in-vitro model of EndMT was generated using high glucose (HG) and TNF-α in human aortic endothelial cells (HAECs). EZH2 methyltransferase activity was inhibited using EZH2 specific inhibitor GSK-126. RNA sequencing was performed in this setting. EZH2 genetic knockdown (shRNA) in HAECs was also performed to validate role of EZH2 in EndMT. In addition, EZH2 mediated H3K27me3 and EndMT was assessed in atheroprone diabetic mouse model. Results: In HAECs, morphological changes as well as gene and protein expression confirmed TNF-α+HG induced EndMT, which was blunted by GSK-126. Elevated EZH2 mediated H3K27me3 activity by the TNF-α + HG stimulation was blunted with GSK-126 treatment. Furthermore, RNA sequencing identified several enriched pathways including AGE-RAGE signaling pathway in diabetic complications, focal adhesion, and leukocyte trans-endothelial migration directly relevant to EndMT and commonly deregulated in diabetic complications, which were rescued by EZH2 inhibition. Transcriptomic analysis showed that 242 genes including MMP2, NOS3 linked to EndMT were dysregulated. Interestingly, expression of 76 dysregulated genes in EndMT were rescued by GSK-126. EZH2 knockdown studies in HAECs also validated the role of EZH2 in EndMT. Furthermore, immunofluorescence staining identified elevated levels of H3K27me3 in the aortic endothelial layer of diabetic Apoe -/- mice. Co-localization of EndMT markers was observed in the endothelial layer of aortic sinus of diabetic Apoe -/- mice which was blunted with GSK-126 treatment. Conclusion: The study identified EZH2 inhibition as a novel therapeutic target in diabetes induced EndMT in atherosclerosis. These findings highlighted ongoing efforts to develop targeted therapies for diabetic patients who are at risk to develop cardiovascular disease.

Study on the mechanism of OSM participating in myocardial fibrosis by inhibiting TGFβ-induced EndMT of cardiac microvascular endothelial cells through SPARC/SMAD signaling.

Cardiac fibrosis constitutes a crucial element in the progression of diverse chronic cardiac conditions. Notably, a significant correlation has been observed between the endothelial-to-mesenchymal transition (EndMT) and the emergence of cardiac fibrosis. To investigate mechanisms, we employed immunofluorescence for α-SMA and CD31 analysis, Western blotting for CD34, vimentin, and SPARC overexpression. CCK8, wound healing, and transwell assay-assessed cell viability, invasion, and migration. SPARC overexpression plasmid was constructed and validated by Western blotting. Fibrosis levels were quantified via Masson staining, and collagen 1 and 3 expressions were measured using ELISA assays. Notably, in TGF-β-induced H5V cells, the downregulation of CD31 and CD34 expression, along with the upregulation of α-SMA and vimentin, suggests the induction of EndMT in cardiac fibrosis. Interestingly, OSM treatment mitigated EndMT progression, cell invasion, migration, and the expression of p-SMAD2, p-SMAD3, and SPARC in TGF-β-treated H5V cells. Further analysis revealed that OSM alleviated TGFβ-induced EndMT, invasion, and migration of cardiac microvascular endothelial cells by suppressing SPARC/SMAD signaling. Moreover, OSM therapy notably mitigated myocardial tissue fibrosis, along with a reduction in the expression of collagen 1, collagen 3, α-SMA, and CD34, while augmenting CD31 and vimentin expression in ISO-induced myocardial tissue. Additionally, OSM exhibited the ability to suppress myocardial tissue fibrosis and the expression of EndMT markers as well as SPARC/SMAD signals in ISO-induced myocardial tissue. Our comprehensive analysis unveiled that OSM contributes significantly to myocardial fibrosis modulation by inhibiting TGFβ-mediated EndMT in myocardial microvascular endothelial cells via SPARC/SMAD signaling.

Blockade of endothelial to mesenchymal transition (EndMT) by an inhibitor of histone methyltransferase EZH2 attenuates atherosclerosis in diabetes

Abstract Background Atherosclerosis is a major contributor to cardiovascular disease (CVD) related deaths in individuals with diabetes. Persistent endothelial cell activation caused by factors such as hyperglycaemia induces endothelial to mesenchymal transition (EndMT), which promotes both initiation as well as progression of atherosclerosis. Gene expression changes that occur during EndMT, are regulated by multiple factors including epigenetic modifiers such as the histone methyltransferase EZH2 (Enhancer of zest homolog 2). Recent studies have implicated the role of EndMT in cardiovascular complications of diabetes including atherosclerosis. However, the role of EZH2 in induction of EndMT in diabetes associated atherosclerosis is not known. Methods Aortae of atheroprone diabetic Apoe-/- mice were subjected to single cell RNA sequencing (scRNA-seq) analysis using 10X Genomics platform. In vitro model mimicking diabetes-induced EndMT was established in human aortic endothelial cells (HAECs) using high glucose (25mM) and TNF-α containing media for 72 hrs ± a small molecule inhibitor of EZH2, GSK126. RNA and Chromatin Immunoprecipitation (ChIP) sequencing was performed to identify EZH2-mediated epigenomic and corresponding transcriptomic changes in this setting. Complementary in vitro EZH2 knockdown experiments using shRNA were also performed. Moreover, Apoe-/- mice made diabetic with streptozotocin, were treated with GSK126 (50 mg/kg BW daily for 5 weeks) in an intervention study design. Aortic sections from treated and control mice were subjected to immunofluorescent staining specific for the EndMT pathway. Results scRNA-seq analysis identified an EndMT+ve endothelial cell sub-population with a diabetes specific proatherogenic transcriptomic profile. Comparison with the ENCODE dataset for EZH2 target genes using Harmonizome showed that indeed multiple repressed genes in diabetes were targets of EZH2. Methyltransferase activity of EZH2 was elevated in in vitro settings of EndMT. Interestingly, EZH2 inhibition by GSK126 attenuated EndMT. Gene expression analysis showed that GSK126 treatment rescued 76 of 242 differentially expressed genes in HAECs exposed to EndMT conditions. Several differentially expressed genes including COL1A2, MMP2, NOS3, COL4A1, and TGFB2 (FDR <0.05, Log2 fold change (2x)) were targets of EZH2 validating integrated analysis of our scRNA-seq with the ENCODE dataset. EZH2 knockdown experiments validated experimental findings of EZH2 inhibition studies using GSK126 in HAECs. Importantly, GSK126 treatment blocked EndMT resulting in reduced atherosclerosis in diabetic Apoe-/- mice in intervention studies. Conclusion This study showed that the inhibition of EZH2 with GSK126 is a potential vasculoprotective treatment for the diabetes induced EndMT and associated atherosclerosis.

Integrated single-cell RNA-seq analysis reveals mitochondrial calcium signaling as a modulator of endothelial-to-mesenchymal transition.

Endothelial cells (ECs) are highly plastic, capable of differentiating into various cell types. Endothelial-to-mesenchymal transition (EndMT) is crucial during embryonic development and contributes substantially to vascular dysfunction in many cardiovascular diseases (CVDs). While targeting EndMT holds therapeutic promise, understanding its mechanisms and modulating its pathways remain challenging. Using single-cell RNA sequencing on three in vitro EndMT models, we identified conserved gene signatures. We validated original regulators in vitro and in vivo during embryonic heart development and peripheral artery disease. EndMT induction led to global expression changes in all EC subtypes rather than in mesenchymal clusters. We identified mitochondrial calcium uptake as a key driver of EndMT; inhibiting mitochondrial calcium uniporter (MCU) prevented EndMT in vitro, and conditional Mcu deletion in ECs blocked mesenchymal activation in a hind limb ischemia model. Tissues from patients with critical limb ischemia with EndMT features exhibited significantly elevated endothelial MCU. These findings highlight MCU as a regulator of EndMT and a potential therapeutic target.

CD163+ Macrophages Induce Endothelial-to-Mesenchymal Transition in Atheroma.

Cell phenotype switching is increasingly being recognized in atherosclerosis. However, our understanding of the exact stimuli for such cellular transformations and their significance for human atherosclerosis is still evolving. Intraplaque hemorrhage is thought to be a major contributor to plaque progression in part by stimulating the influx of CD163+ macrophages. Here, we explored the hypothesis that CD163+ macrophages cause plaque progression through the induction of proapoptotic endothelial-to-mesenchymal transition (EndMT) within the fibrous cap. Human coronary artery sections from CVPath's autopsy registry were selected for pathological analysis. Athero-prone ApoE-/- and ApoE-/-/CD163-/- mice were used for in vivo studies. Human peripheral blood mononuclear cell-induced macrophages and human aortic endothelial cells were used for in vitro experiments. In 107 lesions with acute coronary plaque rupture, 55% had pathological evidence of intraplaque hemorrhage in nonculprit vessels/lesions. Thinner fibrous cap, greater CD163+ macrophage accumulation, and a larger number of CD31/FSP-1 (fibroblast specific protein-1) double-positive cells and TUNEL (terminal deoxynucleotidyl transferase-dUTP nick end labeling) positive cells in the fibrous cap were observed in nonculprit intraplaque hemorrhage lesions, as well as in culprit rupture sections versus nonculprit fibroatheroma sections. Human aortic endothelial cells cultured with supernatants from hemoglobin/haptoglobin-exposed macrophages showed that increased mesenchymal marker proteins (transgelin and FSP-1) while endothelial markers (VE-cadherin and CD31) were reduced, suggesting EndMT induction. Activation of NF-κB (nuclear factor kappa β) signaling by proinflammatory cytokines released from CD163+ macrophages directly regulated the expression of Snail, a critical transcription factor during EndMT induction. Western blot analysis for cleaved caspase-3 and microarray analysis of human aortic endothelial cells indicated that apoptosis was stimulated during CD163+ macrophage-induced EndMT. Additionally, CD163 deletion in athero-prone mice suggested that CD163 is required for EndMT and plaque progression. Using single-cell RNA sequencing from human carotid endarterectomy lesions, a population of EndMT was detected, which demonstrated significant upregulation of apoptosis-related genes. CD163+ macrophages provoke EndMT, which may promote plaque progression through fibrous cap thinning.

Midkine promotes renal fibrosis by stabilizing C/EBPβ to facilitate endothelial-mesenchymal transition

Numerous myofibroblasts are arisen from endothelial cells (ECs) through endothelial to mesenchymal transition (EndMT) triggered by TGF-β. However, the mechanism of ECs transforms to a different subtype, or whether there exists an intermediate state of ECs remains unclear. In present study, we demonstrate Midkine (MDK) mainly expressed by CD31 + ACTA2+ECs going through partial EndMT contribute greatly to myofibroblasts by spatial and single-cell transcriptomics. MDK is induced in TGF-β treated ECs, which upregulates C/EBPβ and increases EndMT genes, and these effects could be reversed by siMDK. Mechanistically, MDK promotes the binding ability of C/EBPβ with ACTA2 promoter by stabilizing the C/EBPβ protein. In vivo, knockout of Mdk or conditional knockout of Mdk in ECs reduces EndMT markers and significantly reverses fibrogenesis. In conclusion, our study provides a mechanistic link between the induction of EndMT by TGF-β and MDK, which suggests that blocking MDK provides potential therapeutic strategies for renal fibrosis.

H3K27Me3 abundance increases fibrogenesis during endothelial-to-mesenchymal transition via the silencing of microRNA-29c.

Endothelial-to-mesenchymal transition (EndMT) is a transdifferentiation process in which endothelial cells (ECs) adopt a mesenchymal-like phenotype. Over the past few years, it became clear that EndMT can contribute to several cardiovascular pathologies. However, the molecular pathways underlying the development of EndMT remain incompletely understood. Since the epigenetic enzyme Enhancer of Zeste Homolog 2 (EZH2) and its concomitant mark H3K27Me3 have been shown to be elevated in many cardiovascular diseases that associate with EndMT, we hypothesized that H3K27Me3 is a determinant for the susceptibility of EndMT. To study the association between H3K27Me3 and EndMT, a knockdown model of EZH2 in human endothelial cells (HUVEC) was utilized to reduce H3K27Me3 abundance, followed by induction of EndMT using TGFβ1. The expression of molecular markers of EndMT and fibrogenesis were analysed. In cultured HUVECs, a reduction of H3K27Me3 abundance facilitates EndMT but mitigates fibrogenesis as shown by a decreased expression of collagen I and III. In HUVEC, H3K27Me3 abundance directly affects the expression of miR29c, a collagen-targeting miRNA. Additionally, knockdown of miR-29c in HUVEC with low H3K27Me3 abundance partly restored the expression of collagen I and III. Expectedly, in rats with perivascular fibrosis an increased abundance of H3K27Me3 associated with a decreased expression of miR-29c. our data shows that endothelial fibrogenesis underlies an epigenetic regulatory pathway and we demonstrate that a decreased abundance of H3K27Me3 in ECs blunts fibrogenesis in part in a miR-29c dependent manner. Therefore, a reduction of H3K27Me3 could serve as a novel therapeutical strategy to mitigate fibrogenesis and may prove to be beneficial in fibrogenic diseases including atherosclerosis, cardiac fibrosis, and PAH.

Maternal exposure to nano-titanium dioxide impedes fetal development via endothelial-to-mesenchymal transition in the placental labyrinth in mice

BackgroundExtensive production and usage of commercially available products containing TiO2 NPs have led to accumulation in the human body. The deposition of TiO2 NPs has even been detected in the human placenta, which raises concerns regarding fetal health. Previous studies regarding developmental toxicity have frequently focused on TiO2 NPs < 50 nm, whereas the potential adverse effects of large-sized TiO2 NPs received less attention. Placental vasculature is essential for maternal–fetal circulatory exchange and ensuring fetal growth. This study explores the impacts of TiO2 NPs (100 nm in size) on the placenta and fetal development and elucidates the underlying mechanism from the perspective of placental vasculature. Pregnant C57BL/6 mice were exposed to TiO2 NPs by gavage at daily dosages of 10, 50, and 250 mg/kg from gestational day 0.5–16.5.ResultsTiO2 NPs penetrated the placenta and accumulated in the fetal mice. The fetuses in the TiO2 NP-exposed groups exhibited a dose-dependent decrease in body weight and length, as well as in placental weight and diameter. In vivo imaging showed an impaired placental barrier, and pathological examinations revealed a disrupted vascular network of the labyrinth upon TiO2 NP exposure. We also found an increase in gene expression related to the transforming growth factor-β (TGF-β) -SNAIL pathway and the upregulation of mesenchymal markers, accompanied by a reduction in endothelial markers. In addition, TiO2 NPs enhanced the gene expression responsible for the endothelial-to-mesenchymal transition (EndMT) in cultured human umbilical vein endothelial cells, whereas SNAIL knockdown attenuated the induction of EndMT phenotypes.ConclusionOur study revealed that maternal exposure to 100 nm TiO2 NPs disrupts placental vascular development and fetal mice growth through aberrant activation of EndMT in the placental labyrinth. These data provide novel insight into the mechanisms of developmental toxicity posed by NPs.

Unlocking the Role of Endothelial MPL Receptor and JAK2V617F Mutation: Insights into Cardiovascular Dysfunction in MPNs and Chip

Introduction Patients with JAK2V617F-positive myeloproliferative neoplasms (MPNs) and clonal hematopoiesis of indeterminate potential (CHIP) are at a significantly higher risk of cardiovascular diseases (CVDs). Vascular endothelial cells (ECs) carrying the JAK2V617F mutation can be detected in many MPN patients. The thrombopoietin receptor MPL is expressed on vascular ECs, though its role in endothelial function is unclear. In this study, we investigated the mechanisms through which the JAK2V617F mutation induces endothelial dysfunction to accelerate CVDs, shedding light on endothelial MPL as a potential therapeutic target for preventing or mitigating cardiovascular complications in JAK2V617F-positive MPNs. Methods JAK2V617F Flip-Flop mice (FF1; provided by Dr. Radek Skoda) were crossed with VEcadherin-creERT2 mice (CDH5) to generate CDH5 +/-FF1 +/- mice, which can be induced by tamoxifen to express human JAK2V617F specifically in vascular ECs but not in blood cells. MPL fl mice (provided by Dr. Warren Alexander) were crossed with CDH5 +FF1 + mice to generate CDH5 +FF1 +MPL fl/fl mice. To validate findings in transgenic murine models in human cells, we utilized a pair of isogenic induced pluripotent stem (iPS) cell lines derived from the same MPN patient, one carrying the JAK2V617F mutation (PVB1.4) and the other being JAK2 wild-type (PVB1.11). These iPS cell lines were differentiated into human ECs using a modified iPS differentiation protocol. Results CDH5 +FF1 + mice exhibited mild thrombocytosis but no cardiac dysfunction. However, when challenged with a high-fat diet, these mice developed dilated cardiomyopathy with significant decreases in LV ejection fraction and increases in LV end-diastolic and end-systolic volumes. Pathological evaluation revealed the presence of thromboses in segment pulmonary arteries and scattered coronary capillaries. There was intimal thickening, smooth muscle cell thickening, and perivascular fibrosis of scattered coronary arterioles in CDH5 +FF1 + mice compared to control mice. These findings, along with impaired cardiac EC function (measured by angiogenesis in vitro) and loss of EC markers, as well as significant enrichment of gene expression signatures associated with inflammatory response and epithelial-mesenchymal transition in JAK2V617F mutant cardiac ECs, suggest that the JAK2V617F mutation induces endothelial-to-mesenchymal transition (EndMT) in cardiac ECs from the CDH5 +FF1 + mice. Similarly, JAK2 wild-type ECs derived from PVB1.11 iPS cell line maintained the expression of EC markers and the characteristic cobblestone endothelial morphology throughout serial passages in vitro; in contrast, JAK2V617F mutant ECs derived from PVB1.4 exhibited a gradual loss of EC marker expression, decreased EC function, and underwent a phenotypical transition toward a fibroblastoid morphology, providing compelling evidence of EndMT induction by the JAK2V617F mutation in human ECs. We noticed that the thrombopoietin receptor MPL is abundantly expressed in the heart's vascular endothelium, compared to other tissues (e.g., lung, marrow, spleen). MPL expression is upregulated in JAK2V617F mutant ECs compared to wild-type ECs, and Inhibiting JAK-STAT signaling using Ruxolitinib abolished this MPL upregulation. To investigate the role of endothelial TPO/MPL signaling in JAK2V617F-induced cardiovascular dysfunction, we generated CDH5 +FF1 +MPL fl/fl mice to knock down MPL in JAK2V617F-bearing vascular ECs. The CDH5 +FF1 +MPL fl/fl mice maintained normal blood counts and cardiac function even after a high-fat diet challenge. In JAK2V617F mutant human ECs derived from PVB1.4 iPS cell line, treatment with AMM2, an anti-MPL neutralizing antibody, preserved EC markers and endothelial morphology compared to untreated mutant ECs. These results demonstrated that inhibiting the endothelial MPL can suppress JAK2V617F-induced EndMT and prevent cardiovascular dysfunction caused by mutant ECs. Notably, the endothelial MPL receptor is not indispensable for the normal physiological regulation of blood cell counts and cardiac function. Conclusion Our study provides valuable insights into the increased risk of CVDs observed in patients with JAK2V617F-positive CHIP and MPNs. Further investigations into the role of EndMT in other CHIP-associated mutations may shed light on the diverse CVD risks associated with different CHIP mutations.

RNA elongation contributes to gene expression regulation during early endothelial-to-mesenchymal transition

Abstract Background Endothelial dysfunction is characterized by endothelial-to-mesenchymal transition (EndMT), a process in which endothelial cells (EC) transform into mesenchymal cells and lose part of their endothelial identity. EndMT-positive cells are present in vulnerable atherosclerotic plaques. EndMT is triggered by stress stimuli such as inflammation or hypoxia that require an adaptive change in gene expression mediated at the level of RNA elongation. RNA elongation is controlled by the super elongation complex (SEC), which is built around scaffolding proteins of the AF family (AFF1-AFF4). The SEC controls the pausing of RNA Polymerase II (RNAPII). We hypothesized that RNA elongation plays a regulatory role in EndMT. Methods and Results Single cell sequencing data revealed that the SEC scaffold proteins AFF1 and AFF4 are ubiquitously expressed in human carotid artery plaques. AFF1 and AFF4 are higher expressed in EC compared to AFF2 and AFF3. In an in vitro EndMT model, AFF1 and AFF4 were upregulated compared to controls (AFF1: 1.9-fold; AFF4: 2.6-fold). SEC inhibition using chemical compounds reduced the protein levels of AFF1 (-67.4%) and AFF4 (-46.5%). EndMT induction was reduced by SEC inhibition, as measured by mesenchymal marker gene expression (SM22: -88.8%; CNN1: -94.0%). The rapid induction of gene expression depends on the release of paused RNAPII present at the promoter site. ChIP-sequencing revealed a reduced occupancy of RNAPII at promoter sites in EndMT as early as 2 h compared to controls, suggesting a rapid pause release of RNAPII during EndMT. Indeed, transcriptome-wide RNA elongation rates were increased by 20.2% as early as 10 min after induction of EndMT, as determined by analysis of newly synthesized 4sU-labelled RNA. SEC inhibition reduced transcriptome-wide RNA elongation rates (-26.8%). These data suggest a regulatory contribution of RNA elongation in early EndMT. Among the genes that were immediately and prominently upregulated after the induction of EndMT was the SPARC mRNA. RNA initiation and elongation of SPARC mRNA was increased 10 min after EndMT induction, which was reduced by SEC inhibition. 72 hours after EndMT induction, inhibition of SEC resulted in a reduction in SPARC mRNA (-72.2%), protein concentration (-97.2%) and reduced SPARC delivery to the supernatant (-43.9%). Knockdown of SPARC enhanced EndMT induction (SM22: 1.6-fold; CNN1: 3.6-fold), which was attenuated by treatment with recombinant SPARC. Conclusions We observed increased RNA elongation rates during EndMT associated with decreased pausing of RNA Polymerase II. The RNA elongation mediated specific gene expression such as the upregulation of SPARC. Taken together, our results indicate that RNA elongation plays a regulatory role in EndMT.

Growth differentiation factor 15 (GDF15) is elevated in human plaques and promotes endothelial-to-mesenchymal transition (EndMT)

Abstract Introduction and Purpose Growth Differentiation Factor 15 (GDF15) is a member of the TGF-β superfamily and is upregulated under conditions of injury and stress such as hypoxia. GDF15 serum concentrations correlate with inflammation, cardiac fibrosis and unfavorable prognosis in cardiovascular diseases. The functional role of GDF15 in endothelial cells is largely unknown. Here, we investigate a possible role of GDF15 in the transdifferentiation of endothelial cells (EC) into mesenchymal cells (EndMT). Methods and Results GDF15 is expressed at mRNA and protein level in primary human ECs and is secreted as determined by qPCR, single cell sequencing (scRNA-seq) and enzyme-linked immunosorbent assay (mean ± SEM, 743.8±39.3 pg/ml, n=3). Analysis of vascular sections from Ldlr-/- mice fed a high-fat diet using spatial transcriptomics revealed increased GDF15 expression. ScRNA-seq analysis of human plaques and normal vessel sections from the same individuals revealed a 22-fold ± 5.48 (p&amp;lt;0.05) increase in GDF15 in ECs located in plaques compared to ECs in control vessel regions. Experiments in cultured human endothelial cells showed increased GDF15 mRNA expression qPCR (+1.7-fold control, p&amp;lt;0.05) and scRNA-seq analysis after EndMT induction. Treatment with increasing levels of recombinant GDF15 (10, 50 and 150 ng/ml) induced EndMT as measured by expression of the EndMT marker calponin (+3.36, 7.99 and 9.53-fold, all p&amp;lt;0.05). Interestingly, EndMT induction decreased extracellular GDF15 levels (-54.6%, p&amp;lt;0.05), whereas intracellular levels in EC were increased (+1.9-fold control, p&amp;lt;0.05). The use of GDF15 neutralising antibodies (1 µg/ml) reduced soluble GDF15 levels by 97.7% as measured by ELISA (p&amp;lt;0.001). Treatment with neutralising antibodies against GDF15 reduced EndMT induction by 54% as measured by the EndMT marker calponin (p&amp;lt;0.05). Conclusion In conclusion, GDF15 is elevated in mouse and human plaques, and in EndMT. Treatment with GDF15 induces EndMT, whereas inhibition by neutralising antibodies reduces EndMT induction. These data are consistent with a functional role of GDF15 in endothelial dysfunction and atherogenesis.

Abstract 15796: Akt1 Y350f Mutation: A Protective Mechanism Against Pulmonary Hypertension, Suppressing Endothelial-to-Mesenchymal Transition in vivo and in vitro

Background: Pulmonary hypertension (PH) is a life-threatening condition characterized by elevated blood pressure in the lungs due to narrowed arteries. Endothelial-to-mesenchymal transition (EndMT) contributes to enhanced proliferation and metabolic changes in the pulmonary arteries of PH patients. Our previous reports have highlighted the role of Akt nitration at tyrosine 350 (Y350) residue in promoting proliferation and metabolic switch in PH models. To investigate the protective potential of inhibiting Akt nitration, we developed a mouse model with a mutation of Akt Y350 to phenylalanine (Y350F), preventing nitration and activation of Akt. Hypothesis: We hypothesized that Akt1 Y350F mutant mice would be protected in preclinical PH models due to inhibited EndMT. Methods: Both mutant Y350F and wild-type Akt1 mice were treated with Sugen5416 (20mg/kg/week i.p.)/hypoxia (10% O2) (Su/Hx) for four weeks to explore pathological mechanisms. Endothelial cells were isolated for in vitro evaluation under EndMT inducers, including Sin-1 chloride and TGF-β1. Results: The wild-type Su/Hx model exhibited vascular remodeling, increased right ventricular systolic pressure (RVSP) (p&lt;0.001), and right ventricular hypertrophy. In contrast, the Akt Y350F mutant model displayed significant protection, with reduced vascular remodeling, pulmonary pressure, and right heart hypertrophy. Akt nitration-induced EndMT markers, TGF-β1 (p&lt;0.05) and TWIST1 (p&lt;0.01), were elevated in wild-type Su/Hx lung tissue. However, the Akt Y350F mutation prevented Akt activation and diminished EndMT markers in the Akt1 Y350F Su/Hx lungs. In isolated cells and lung tissue, induction of EndMT resulted in a progressive PH phenotype, while Akt inhibition exhibited a protective role against PH progression in the Akt Y350F mutant model. Conclusion: Inhibition of Akt nitration through the Y350F mutation restricts vascular remodeling and halts EndMT both in vivo and in vitro. Our findings suggest that strategies targeting Akt nitration could be effective in controlling PH.

Abstract P1134: RNA Elongation Mediates Rapid Induction Of Gene Expression During Endothelial-to-mesenchymal Transition

Endothelial-to-mesenchymal transition (EndMT) is triggered by stress stimuli and characterized by the conversion of endothelial cells (EC) into mesenchymal cells. Stress stimuli such as hypoxia or inflammation depend on rapid gene expression mediated by RNA elongation. RNA elongation is controlled by the super elongation complex (SEC) through transient pausing of RNA Polymerase II (RNAPII). We aimed to analyze the regulatory role of RNA elongation on rapid gene expression during the onset of EndMT. In an in vitro EndMT model, SEC scaffolds AFF1 and AFF4 were upregulated compared to controls. SEC inhibition using chemical compounds reduced the protein levels of AFF1 and AFF4. EndMT was reduced by SEC inhibition, whereas overexpression of AFF4 increased EndMT as measured by mesenchymal marker gene expression. Rapid gene expression depends on the release of paused RNAPII at promoter sites. ChIP-sequencing revealed a reduction of RNAPII occupancy at promoter sites in EndMT compared to controls, suggesting the release of RNAPII during EndMT. Transcriptome-wide RNA elongation rates were increased as early as 10 min after induction of EndMT, as determined by analysis of nascent 4sU-labeled RNA. SEC inhibition reduced global RNA elongation rates, suggesting a regulatory contribution of RNA elongation in EndMT. Among the genes that were immediately upregulated after the induction of EndMT was the SPARC mRNA. RNA initiation and elongation of SPARC mRNA were increased 10 min after EndMT induction, which was reduced by SEC inhibition. At 72 h after EndMT induction, inhibition of SEC decreased SPARC mRNA, protein concentration and SPARC delivery to the supernatant. Silencing of SPARC reduced the angiogenic potential of EC and enhanced EndMT induction, which was attenuated by treatment with recombinant SPARC. Treatment with recombinant SPARC also improved endothelial impedance under EndMT conditions. Spatial transcriptomics revealed increased SPARC expression in brachiocephalic artery plaques from LDLR-/- mice. In conclusion, we observed increased RNA elongation rates associated with reduced RNAPII pausing during EndMT that mediate rapid gene expression of target genes such as SPARC. Our results suggest that RNA elongation plays a regulatory role in EndMT.

Human and porcine aortic valve endothelial and interstitial cell isolation and characterization.

Calcific aortic valve stenosis (AVS) is defined by pathological changes in the aortic valve (AV) and their predominant cell types: valvular interstitial (VICs) and endothelial cells (VECs). Understanding the cellular and molecular mechanisms of this disease is a prerequisite to identify potential pharmacological treatment strategies. In this study, we present a unique aortic valve cell isolation technique to acquire specific human and porcine cell populations and compared VICs and VECs of these species with each other for the first time. AV cells were isolated from tissue obtained from human patients undergoing surgical aortic valve replacement (SAVR) or from porcine hearts. Functional analysis and in vitro experiments revealed that endothelial-to-mesenchymal transition (EndMT) can be induced in hVECs, leading to a significant increase in mesenchymal markers. In vitro calcification experiments of VICs demonstrated pronounced expression of calcification markers and visible calcific deposits in Alizarin Red staining in both species after incubation with pro-calcific media. Cells isolated from patient-derived AVs showed mesenchymal and endothelial-specific gene signatures (VIC and VEC, respectively). For instance, von Willebrand factor (vWF) and platelet endothelial adhesion molecule-1 (PECAM1) were upregulated in VECs, while the myofibroblastic markers alpha-smooth muscle actin (α-SMA) and vimentin (VIM) were downregulated in VECs compared to VICs. Analysis of cell function by migration revealed that VECs are more migratory than VICs. Induction of EndMT in vitro in VECs displayed increased expression of EndMT markers and decreased expression of endothelial markers, confirming their mesenchymal transdifferentiation ability. In vitro calcification of VICs revealed upregulation of alkaline phosphatase (ALPL), a hallmark of calcification. In addition, other calcification-related genes such as osteocalcin (BGLAP) and runt-related factor 2 (RUNX2) were upregulated. Alizarin red staining of calcified cells provided a further layer of confirmation that the isolated cells were VICs with osteoblastic differentiation capacity. This study aims to take a first step towards standardizing a reproducible isolation technique for specific human and porcine VEC and VIC populations. A comparison of human and porcine aortic valve cells demonstrated that porcine cells may serve as an alternative cellular model system in settings where human tissue is difficult to obtain.

Acetate controls endothelial-to-mesenchymal transition

Endothelial-to-mesenchymal transition (EndMT), a process initiated by activation of endothelial TGF-β signaling, underlies numerous chronic vascular diseases and fibrotic states. Once induced, EndMT leads to a further increase in TGF-β signaling, thus establishing a positive-feedback loop with EndMT leading to more EndMT. Although EndMT is understood at the cellular level, the molecular basis of TGF-β-driven EndMT induction and persistence remains largely unknown. Here, we show that metabolic modulation of the endothelium, triggered by atypical production of acetate from glucose, underlies TGF-β-driven EndMT. Induction of EndMT suppresses the expression of the enzyme PDK4, which leads to an increase in ACSS2-dependent Ac-CoA synthesis from pyruvate-derived acetate. This increased Ac-CoA production results in acetylation of the TGF-β receptor ALK5 and SMADs 2 and 4 leading to activation and long-term stabilizationof TGF-β signaling. Our results establish the metabolic basis of EndMT persistence and unveil novel targets, such as ACSS2, for the potential treatment of chronic vascular diseases.

Abstract 12021: Investigation of the Role of Long Non-Coding RNA H19 on Endothelial to Mesenchymal Transition in Aortic Valve Stenosis

Background: Endothelial to mesenchymal transition (EndMT) is a transdifferentiation process of cells that is associated with the development of aortic valve stenosis (AVS) in adulthood. It was shown that long non-coding RNAs are dysregulated in this process and might play a crucial role in EndMT-mediated AVS. Here we aim to elucidate the role of long non-coding RNA H19 (LncRNA H19) in the pathogenesis of EndMT-related AVS. Methods and Results: RNA sequencing of aortic valve tissue explanted from AVS-patients with coronary artery disease (CAD) revealed that H19 was significantly dysregulated. EndMT was induced in vitro in vascular and valvular endothelial cells (VECs) via TNFα and TGFß+IL1ß stimulation and expression of endothelial marker genes vWF and eNOS and mesenchymal marker genes αSMA , SM22 , Vimentin and SNAI2 was confirmed by RT-qPCR. Loss of function of H19 followed by EndMT induction demonstrated distinct changes in gene expression profile and protein levels which were detected by qRT-PCR, immunoblotting, and immunofluorescence. Further experiments indicate that loss of H19 may promote EndMT. Functional assays in vascular and valvular endothelial cells suggested that H19 is a critical regulator of angiogenic sprouting and migration. To unveil the specific molecular signature in angiogenesis a RT 2 profiler array was performed to identify the regulation of angiogenesis with 84 angiogenesis-related genes. Our assay revealed JAG1 as a potential dysregulated candidate with a 4.43-fold regulation. Further molecular mechanism will be investigated via identification of binding partners and downstream targets of H19 in EndMT by using primary cells and VECs. Conclusion: Our data suggests that H19 might play a role in EndMT in context of AVS. Further investigation by using a murine model of AVS should confirm the H19-mediated of EndMT in the development of AVS.

Leptin treatment has vasculo-protective effects in lipodystrophic mice

Lipodystrophy syndromes (LDs) are characterized by loss of adipose tissue, metabolic complications such as dyslipidemia, insulin resistance, and fatty liver disease, as well as accelerated atherosclerosis. As a result of adipose tissue deficiency, the systemic concentration of the adipokine leptin is reduced. A current promising therapeutic option for patients with LD is treatment with recombinant leptin (metreleptin), resulting in reduced risk of mortality. Here, we investigate the effects of leptin on endothelial to mesenchymal transition (EndMT), which impair the functional properties of endothelial cells and promotes atherogenesis in LD. Leptin treatment reduced inflammation and TGF-β2-induced expression of mesenchymal genes and prevented impairment of endothelial barrier function. Treatment of lipodystrophic- and atherosclerosis-prone animals (Ldlr-/-; aP2-nSrebp1c-Tg) with leptin reduced macrophage accumulation in atherosclerotic lesions, vascular plaque protrusion, and the number of endothelial cells with mesenchymal gene expression, confirming a reduction in EndMT in LD after leptin treatment. Treatment with leptin inhibited LD-mediated induction of the proatherosclerotic cytokine growth/differentiation factor 15 (GDF15). Inhibition of GDF15 reduced EndMT induction triggered by plasma from patients with LD. Our study reveals that in addition to the effects on adipose tissue function, leptin treatment exerts beneficial effects protecting endothelial function and identity in LD by reducing GDF15.

Integrin-Linked Kinase Expression in Human Valve Endothelial Cells Plays a Protective Role in Calcific Aortic Valve Disease.

Calcific aortic valve disease (CAVD) is highly prevalent during aging. CAVD initiates with endothelial dysfunction, leading to lipid accumulation, inflammation, and osteogenic transformation. Integrin-linked kinase (ILK) participates in the progression of cardiovascular diseases, such as endothelial dysfunction and atherosclerosis. However, ILK role in CAVD is unknown. First, we determined that ILK expression is downregulated in aortic valves from patients with CAVD compared to non-CAVD, especially at the valve endothelium, and negatively correlated with calcification markers. Silencing ILK expression in human valve endothelial cells (siILK-hVECs) induced endothelial-to-mesenchymal transition (EndMT) and promoted a switch to an osteoblastic phenotype; SiILK-hVECs expressed increased RUNX2 and developed calcified nodules. siILK-hVECs exhibited decreased NO production and increased nitrosative stress, suggesting valvular endothelial dysfunction. NO treatment of siILK-hVECs prevented VEC transdifferentiation, while treatment with an eNOS inhibitor mimicked ILK-silencing induction of EndMT. Accordingly, NO treatment inhibited VEC calcification. Mechanistically, siILK-hVECs showed increased Smad2 phosphorylation, suggesting a TGF-β-dependent mechanism, and NO treatment decreased Smad2 activation and RUNX2. Experiments performed in eNOS KO mice confirmed the involvement of the ILK-eNOS signaling pathway in valve calcification, since aortic valves from these animals showed decreased ILK expression, increased RUNX2, and calcification. Our study demonstrated that ILK endothelial expression participates in human CAVD development by preventing endothelial osteogenic transformation.

Effect of Eribulin on Angiogenesis and the Expression of Endothelial Adhesion Molecules.

Tumor vasculature is an important component of the tumor microenvironment and deeply affects anticancer immune response. Eribulin is a non-taxane inhibitor of the mitotic spindle. However, off-target effects interfering with the tumor vasculature have been reported. The mechanisms responsible of this effect are still unclear. We designed an in vitro study to investigate the effect of eribulin, with or without TGF-β, on neo-angiogenesis, and on the expression of the adhesion molecules ICAM-1 and VCAM-1. We also investigated the effects of paclitaxel and vinorelbine under the same experimental conditions. Eribulin up-regulated the epithelial markers VE-cadherin and CD-31 in HUVEC and inhibited tube formation in HUVEC cells cultured in Matrigel. The drug effectively arrested tube formation even in the presence of TGF-β and counteracted the TGF-β-induced change in cell shape from the endothelial cobblestone-like morphology to an elongated spindle-shaped morphology. We also observed that eribulin was able to upregulate ICAM-1 and to counteract its down-regulation induced by TGF-β. Eribulin exerts different off-label effects: increases vascular remodeling, counteracts the endothelial-to-mesenchymal transition (EndMT) mediated by TGF-β and promotes tumor infiltration by immune cells via increasing the expression of ICAM-1 and transcription of CD31 and VE-cadherin. Moreover, eribulin was able to inhibit vasculature remodeling and the induction of EndMT mediated by TGF-β better than vinorelbine and paclitaxel. The effects observed in this study might have important therapeutic consequence if the drug is combined with immunotherapy.

Abstract 11611: The Wnt Inhibitor Secreted Frizzled-Related Protein 3 Protects Mitral Valve Endothelium from Mi-Induced Endothelial to Mesenchymal Transition

Introduction: There are changes in the mitral valve (MV) leaflets seen within 2-6 months post-myocardial infarction (MI) that include endothelial to mesenchymal transition (EndMT) and fibrosis. Early modulation of EndMT and fibrosis in MV leaflets may limit ischemic mitral regurgitation and heart failure. The onset of EndMT and fibrosis in MV leaflets and the mechanism of their instigation are not known. Hypothesis: We hypothesized that circulating molecules present in plasma within days after MI incite EndMT and fibrotic processes in MV leaflets. Methods: Using flow cytometric analysis and immunofluorescence staining, we examined the onset of EndMT in 20 adult sheep: 8 sheep with IMI, 8 with sham surgery, and 4 naïve controls with immediate excision of hearts under general anesthesia. The effect of plasma on EndMT induction in primary MV endothelial cells (VECs) was assessed by qPCR, migration assays, and immunofluorescence staining. Plasma cytokine levels were assessed using a cytokine array. Immunoblotting, immunofluorescence staining, RNA sequencing and bioinformatic analysis were used to identify biochemical changes by post-MI plasma. Results: Ovine MVs harvested 8-10 days after inferior MI revealed an onset of EndMT, shown by increased CD31/α-SMA-positive cells in post-MI MV leaflets. In contract to sham plasma, post-MI plasma induced EndMT and pro-fibrotic markers and enhanced migration of primary mitral VECs. Analysis of sham versus post-MI plasma revealed a significant drop in the Wnt antagonist sFRP3 in post-MI plasma. Addition of recombinant sFRP3 to post-MI plasma reversed its EndMT-inducing effect on mitral VECs, measured by restored VE-cadherin, reduced α-SMA, and reduced TGFβ1-3 expression. RNA-seq analysis of mitral VECs exposed to post-MI showed upregulated FOXM1. Blocking FOXM1 with Siomycin A reduced EndMT and pro-fibrotic transcripts in mitral VECs treated with post-MI plasma. Finally, FOXM1 induced by post-MI plasma was downregulated by sFRP3. Conclusions: Reduced sFRP3 in post-MI plasma facilitates EndMT and fibrosis in mitral VECs by increasing the transcription factor FOXM1. Restoring sFRP3 levels and/or inhibiting FOXM1 may provide new strategies to minimize MI-induced maladaptive changes that occur in the MV.