Mustn1 is a smooth muscle cell-secreted microprotein that modulates skeletal muscle extracellular matrix composition.

OBJECTIVE: Skeletal muscle plasticity and remodeling are critical for adapting tissue function to use, disuse, and regeneration. The aim of this study was to identify genes and molecular pathways that regulate the transition from atrophy to compensatory hypertrophy or recovery from injury. Here, we have used a mouse model of hindlimb unloading and reloading, which causes skeletal muscle atrophy, and compensatory regeneration and hypertrophy, respectively. METHODS: We analyzed mouse skeletal muscle at the transition from hindlimb unloading to reloading for changes in transcriptome and extracellular fluid proteome. We then used qRT-PCR, immunohistochemistry, and bulk and single-cell RNA sequencing data to determine Mustn1 gene and protein expression, including changes in gene expression in mouse and human skeletal muscle with different challenges such as exercise and muscle injury. We generated Mustn1-deficient genetic mouse models and characterized them in vivo and ex vivo with regard to muscle function and whole-body metabolism. We isolated smooth muscle cells and functionally characterized them, and performed transcriptomics and proteomics analysis of skeletal muscle and aorta of Mustn1-deficient mice. RESULTS: We show that Mustn1 (Musculoskeletal embryonic nuclear protein 1, also known as Mustang) is highly expressed in skeletal muscle during the early stages of hindlimb reloading. Mustn1 expression is transiently elevated in mouse and human skeletal muscle in response to intense exercise, resistance exercise, or injury. We find that Mustn1 expression is highest in smooth muscle-rich tissues, followed by skeletal muscle fibers. Muscle from heterozygous Mustn1-deficient mice exhibit differences in gene expression related to extracellular matrix and cell adhesion, compared to wild-type littermates. Mustn1-deficient mice have normal muscle and aorta function and whole-body glucose metabolism. We show that Mustn1 is secreted from smooth muscle cells, and that it is present in arterioles of the muscle microvasculature and in muscle extracellular fluid, particularly during the hindlimb reloading phase. Proteomics analysis of muscle from Mustn1-deficient mice confirms differences in extracellular matrix composition, and female mice display higher collagen content after chemically induced muscle injury compared to wild-type littermates. CONCLUSIONS: We show that, in addition to its previously reported intracellular localization, Mustn1 is a microprotein secreted from smooth muscle cells into the muscle extracellular space. We explore its role in muscle ECM deposition and remodeling in homeostasis and upon muscle injury. The role of Mustn1 in fibrosis and immune infiltration upon muscle injury and dystrophies remains to be investigated, as does its potential for therapeutic interventions.

Utilization of an Artery-on-a-Chip to Unravel Novel Regulators and Therapeutic Targets in Vascular Diseases.

In this study, organ-on-chip technology is used to develop an in vitro model of medium-to-large size arteries, the artery-on-a-chip (AoC), with the objective to recapitulate the structure of the arterial wall and the relevant hemodynamic forces affecting luminal cells. AoCs exposed either to in vivo-like shear stress values or kept in static conditions are assessed to generate a panel of novel genes modulated by shear stress. Considering the crucial role played by shear stress alterations in carotid arteries affected by atherosclerosis (CAD) and abdominal aortic aneurysms (AAA) disease development/progression, a patient cohort of hemodynamically relevant specimens is utilized, consisting of diseased and non-diseased (internal control) vessel regions from the same patient. Genes activated by shear stress follow the same expression pattern in non-diseased segments of human vessels. Single cell RNA sequencing (scRNA-seq) enables to discriminate the unique cell subpopulations between non-diseased and diseased vessel portions, revealing an enrichment of flow activated genes in structural cells originating from non-diseased specimens. Furthermore, the AoC served as a platform for drug-testing. It reproduced the effects of a therapeutic agent (lenvatinib) previously used in preclinical AAA studies, therefore extending the understanding of its therapeutic effect through a multicellular structure.

Apolipoprotein E (ApoE) Rescues the Contractile Smooth Muscle Cell Phenotype in Popliteal Artery Aneurysm Disease.

Popliteal artery aneurysm (PAA) is the most frequent peripheral aneurysm, primarily seen in male smokers with a prevalence below 1%. This exploratory study aims to shed light on cellular mechanisms involved in PAA progression. Sixteen human PAA and eight non-aneurysmatic popliteal artery samples, partially from the same patients, were analyzed by immunohistochemistry, fluorescence imaging, Affymetrix mRNA expression profiling, qPCR and OLink proteomics, and compared to atherosclerotic (n = 6) and abdominal aortic aneurysm (AAA) tissue (n = 19). Additionally, primary cell culture of PAA-derived vascular smooth muscle cells (VSMC) was established for modulation and growth analysis. Compared to non-aneurysmatic popliteal arteries, VSMCs lose the contractile phenotype and the cell proliferation rate increases significantly in PAA. Array analysis identified APOE higher expressed in PAA samples, co-localizing with VSMCs. APOE stimulation of primary human PAA VSMCs significantly reduced cell proliferation. Accordingly, contractile VSMC markers were significantly upregulated. A single case of osseous mechanically induced PAA with a non-diseased VSMC profile emphasizes these findings. Carefully concluded, PAA pathogenesis shows similar features to AAA, yet the mechanisms involved might differ. APOE is specifically higher expressed in PAA tissue and could be involved in VSMC phenotype rescue.

Targeting long non-coding RNA NUDT6 enhances smooth muscle cell survival and limits vascular disease progression.

Long non-coding RNAs (lncRNAs) orchestrate various biological processes and regulate the development of cardiovascular diseases. Their potential therapeutic benefit to tackle disease progression has recently been extensively explored. Our study investigates the role of lncRNA Nudix Hydrolase 6 (NUDT6) and its antisense target fibroblast growth factor 2 (FGF2) in two vascular pathologies: abdominal aortic aneurysms (AAA) and carotid artery disease. Using tissue samples from both diseases, we detected a substantial increase of NUDT6, whereas FGF2 was downregulated. Targeting Nudt6 in vivo with antisense oligonucleotides in three murine and one porcine animal model of carotid artery disease and AAA limited disease progression. Restoration of FGF2 upon Nudt6 knockdown improved vessel wall morphology and fibrous cap stability. Overexpression of NUDT6 in vitro impaired smooth muscle cell (SMC) migration, while limiting their proliferation and augmenting apoptosis. By employing RNA pulldown followed by mass spectrometry as well as RNA immunoprecipitation, we identified Cysteine and Glycine Rich Protein 1 (CSRP1) as another direct NUDT6 interaction partner, regulating cell motility and SMC differentiation. Overall, the present study identifies NUDT6 as a well-conserved antisense transcript of FGF2. NUDT6 silencing triggers SMC survival and migration and could serve as a novel RNA-based therapeutic strategy in vascular diseases.

Downregulation of Erythrocyte miR-210 Induces Endothelial Dysfunction in Type 2 Diabetes.

Red blood cells (RBC) act as mediators of vascular injury in type 2 diabetes mellitus (T2DM). miR-210 plays a protective role in cardiovascular homeostasis and is decreased in whole blood of T2DM mice. We hypothesized that downregulation of RBC miR-210 induces endothelial dysfunction in T2DM. RBC were coincubated with arteries and endothelial cells ex vivo and transfused in vivo to identify the role of miR-210 and its target protein tyrosine phosphatase 1B (PTP1B) in endothelial dysfunction. RBC from patients with T2DM and diabetic rodents induced endothelial dysfunction ex vivo and in vivo. miR-210 levels were lower in human RBC from patients with T2DM (T2DM RBC) than in RBC from healthy subjects. Transfection of miR-210 in human T2DM RBC rescued endothelial function, whereas miR-210 inhibition in healthy subjects RBC or RBC from miR-210 knockout mice impaired endothelial function. Human T2DM RBC decreased miR-210 expression in endothelial cells. miR-210 expression in carotid artery plaques was lower in T2DM patients than in patients without diabetes. Endothelial dysfunction induced by downregulated RBC miR-210 involved PTP1B and reactive oxygen species. miR-210 mimic attenuated endothelial dysfunction induced by RBC via downregulating vascular PTP1B and oxidative stress in diabetic mice in vivo. These data reveal that the downregulation of RBC miR-210 is a novel mechanism driving the development of endothelial dysfunction in T2DM.

Long Noncoding RNA MIAT Controls Advanced Atherosclerotic Lesion Formation and Plaque Destabilization.

BACKGROUND: Long noncoding RNAs (lncRNAs) are important regulators of biological processes involved in vascular tissue homeostasis and disease development. The present study assessed the functional contribution of the lncRNA myocardial infarction-associated transcript (MIAT) to atherosclerosis and carotid artery disease. METHODS: We profiled differences in RNA transcript expression in patients with advanced carotid artery atherosclerotic lesions from the Biobank of Karolinska Endarterectomies. The lncRNA MIAT was identified as the most upregulated noncoding RNA transcript in carotid plaques compared with nonatherosclerotic control arteries, which was confirmed by quantitative real-time polymerase chain reaction and in situ hybridization. RESULTS: Experimental knockdown of MIAT, using site-specific antisense oligonucleotides (LNA-GapmeRs) not only markedly decreased proliferation and migration rates of cultured human carotid artery smooth muscle cells (SMCs) but also increased their apoptosis. MIAT mechanistically regulated SMC proliferation through the EGR1 (Early Growth Response 1)-ELK1 (ETS Transcription Factor ELK1)-ERK (Extracellular Signal-Regulated Kinase) pathway. MIAT is further involved in SMC phenotypic transition to proinflammatory macrophage-like cells through binding to the promoter region of KLF4 and enhancing its transcription. Studies using Miat-/- and Miat-/-ApoE-/- mice, and Yucatan LDLR-/- mini-pigs, as well, confirmed the regulatory role of this lncRNA in SMC de- and transdifferentiation and advanced atherosclerotic lesion formation. CONCLUSIONS: The lncRNA MIAT is a novel regulator of cellular processes in advanced atherosclerosis that controls proliferation, apoptosis, and phenotypic transition of SMCs, and the proinflammatory properties of macrophages, as well.

Lenvatinib halts aortic aneurysm growth by restoring smooth muscle cell contractility.

Abdominal aortic aneurysm (AAA) is a disease with high morbidity and mortality, especially when ruptured. The rationale of this study was to evaluate the repurposing of lenvatinib, a multi-tyrosine kinase inhibitor, in limiting experimental AAA growth targeting vascular smooth muscle cells (VSMCs) and angiogenesis. We applied systemic and local lenvatinib treatment to elastase-induced murine aortic aneurysms, and RNA profiling identified myosin heavy chain 11 (Myh11) as the most deregulated transcript. Daily oral treatment substantially reduced aneurysm formation in 2 independent mouse models. In addition, a large animal aneurysm model in hypercholesterolemic low-density lipoprotein receptor-knockout (LDLR-/-) Yucatan minipigs was applied to endovascularly deliver lenvatinib via drug-eluting balloons (DEBs). Here, a single local endovascular delivery blocked AAA progression successfully compared with a DEB-delivered control treatment. Reduced VSMC proliferation and a restored contractile phenotype were observed in animal tissues (murine and porcine), as well as AAA patient-derived cells. Apart from increasing MYH11 levels, lenvatinib reduced downstream ERK signaling. Hence, lenvatinib is a promising therapy to limit aortic aneurysm expansion upon local endovascular delivery. The tyrosine kinase inhibitor was able to positively affect pathways of key relevance to human AAA disease, even in a potentially new local delivery using DEBs.

The one-carbon pool controls mitochondrial energy metabolism via complex I and iron-sulfur clusters.

Induction of the one-carbon cycle is an early hallmark of mitochondrial dysfunction and cancer metabolism. Vital intermediary steps are localized to mitochondria, but it remains unclear how one-carbon availability connects to mitochondrial function. Here, we show that the one-carbon metabolite and methyl group donor S-adenosylmethionine (SAM) is pivotal for energy metabolism. A gradual decline in mitochondrial SAM (mitoSAM) causes hierarchical defects in fly and mouse, comprising loss of mitoSAM-dependent metabolites and impaired assembly of the oxidative phosphorylation system. Complex I stability and iron-sulfur cluster biosynthesis are directly controlled by mitoSAM levels, while other protein targets are predominantly methylated outside of the organelle before import. The mitoSAM pool follows its cytosolic production, establishing mitochondria as responsive receivers of one-carbon units. Thus, we demonstrate that cellular methylation potential is required for energy metabolism, with direct relevance for pathophysiology, aging, and cancer.

The long noncoding RNA CHROME regulates cholesterol homeostasis in primate.

The human genome encodes thousands of long non-coding RNAs (lncRNAs), the majority of which are poorly conserved and uncharacterized. Here we identify a primate-specific lncRNA (CHROME), elevated in the plasma and atherosclerotic plaques of individuals with coronary artery disease, that regulates cellular and systemic cholesterol homeostasis. LncRNA CHROME expression is influenced by dietary and cellular cholesterol via the sterol-activated liver X receptor transcription factors, which control genes mediating responses to cholesterol overload. Using gain- and loss-of-function approaches, we show that CHROME promotes cholesterol efflux and HDL biogenesis by curbing the actions of a set of functionally related microRNAs that repress genes in those pathways. CHROME knockdown in human hepatocytes and macrophages increases levels of miR-27b, miR-33a, miR-33b and miR-128, thereby reducing expression of their overlapping target gene networks and associated biologic functions. In particular, cells lacking CHROME show reduced expression of ABCA1, which regulates cholesterol efflux and nascent HDL particle formation. Collectively, our findings identify CHROME as a central component of the non-coding RNA circuitry controlling cholesterol homeostasis in humans.

The Role of MicroRNA-21 in Venous Neointimal Hyperplasia: Implications for Targeting miR-21 for VNH Treatment.

The molecular mechanism of hemodialysis access arteriovenous fistula (AVF) failure due to venous neointimal hyperplasia (VNH) is not known. The role of microRNA-21 (miR-21) in VNH associated with AVF failure was investigated by performing in vivo and in vitro experiments. In situ hybridization results revealed that miR-21 expression increased and was associated with fibroblasts in failed AVFs from patients. In a murine AVF model, qRT-PCR gene expression results showed a significant increase in miR-21 and a decrease in miR-21 target genes in graft veins (GVs) compared to contralateral veins in mouse AVF. miR-21 knockdown in GVs was performed using a lentivirus-mediated small hairpin RNA (shRNA), and this improved AVF patency with a decrease in neointima compared to control GVs. Moreover, loss of miR-21 in GVs significantly decreased the Tgfß1, Col-Ia, and Col-Iva genes. Immunohistochemistry demonstrated a significant decrease in myofibroblasts and proliferation with an increase in terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining in miR-21-knockdown vessels, along with a decrease in hypoxia-inducible factor-1 alpha (HIF-1α) and phospho-SMAD2 (pSMAD-2) and phospho-SMAD3 (pSMAD-3) and an increase in phosphatase and tensin homolog (PTEN) staining. Hypoxic fibroblast knockdown for miR-21 showed a significant decrease in Tgfß-1 expression and pSMAD-2 and -3 levels and a decrease in myofibroblasts. These results indicate that miR-21 upregulation causes VNH formation by fibroblast-to-myofibroblast differentiation.

miR-29b Mediates the Chronic Inflammatory Response in Radiotherapy-Induced Vascular Disease.

As a consequence of the success of present-day cancer treatment, radiotherapy-induced vascular disease is emerging. This disease is caused by chronic inflammatory activation and is likely orchestrated in part by microRNAs. In irradiated versus nonirradiated conduit arteries from patients receiving microvascular free tissue transfer reconstructions, irradiation resulted in down-regulation of miR-29b and up-regulation of miR-146b. miR-29b affected inflammation and adverse wound healing through its targets pentraxin-3 and dipeptidyl-peptidase 4. In vitro and in vivo, we showed that miR-29b overexpression therapy, through inhibition of pentraxin-3 and dipeptidyl-peptidase 4, could dampen the vascular inflammatory response.

The structural atrophy of the aneurysm wall in secondary expanding aortic aneurysms with endoleak type II.

BACKGROUND: Abdominal aortic aneurysm (AAA) has an age-dependent prevalence of 2% to 11% and is a leading cause of death in men aged >65 years if not treated surgically. Today, endovascular aneurysm repair (EVAR) is performed in up to 80% of elective cases and 60% of ruptured cases. Although EVAR improves perioperative, early, and midterm outcomes, it is associated with specific complications, especially endoleaks (ELs). Type II EL occurs in up to 30% of procedures; however, aneurysm sac expansion and rupture are rare, and currently nothing is known about the morphologic changes in this condition. In this study, we investigate the aneurysm wall morphology in secondary expanding human AAA samples after EVAR with persistent type II EL in comparison to nonaneurysmatic control aortic and AAA samples. METHODS: Samples were acquired from the aneurysm sac during retroperitoneal feeder vessel ligation in a cohort of 10 patients with secondary expansion after EVAR and type II EL diagnosed by computed tomography and contrast-enhanced ultrasound. Control tissues included 42 AAAs and 13 control aortae published previously. Hematoxylin and eosin staining and immunohistochemistry for CD3/4/31/68 and Ki67 were performed for morphologic analysis. Terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick end labeling (TUNEL) assays allowed quantification of apoptosis. Reverse transcription-polymerase chain reaction was used to quantify gene expression and Western blot to quantify collagen expression. RESULTS: Secondary expansion of 33.8% ± 30% during 5 years was seen after EVAR before reoperation. The aneurysm wall after expansion shows significant thinning of the intima-media layer accompanied by a scarcity of cells, with only a little chronic inflammation left compared with AAA samples. Macrophages are seen in abundance, and matrix metalloproteinase expression is significantly upregulated. Relevant apoptosis is not noticed. Fibrous tissue is reduced, and a collagen turnover to different subtypes is noted in comparison to nonaneurysmatic control aorta and AAA. In addition, the transcription factors vascular endothelial growth factor, Kruppel-like factor 4, and BCL2, elevated in AAA, are significantly reduced after secondary expansion. CONCLUSIONS: The aneurysm sac morphology after EVAR with persistent type II EL is characterized by atrophy and proteolysis suggestive of structural weakening. These results should be considered for the follow-up schedule as well as for the potential treatment of this most frequent EVAR complication.

Four Surgical Modifications to the Classic Elastase Perfusion Aneurysm Model Enable Haemodynamic Alterations and Extended Elastase Perfusion.

OBJECTIVE/BACKGROUND: Abdominal aortic aneurysm (AAA) is an individual and socioeconomic burden in today's ageing society. Treatment relies on surgical exclusion of the dilated aorta by open or endovascular repair. For research purposes, animal models are necessary and the elastase induced aneurysm model closely mimics end stage human aneurysm disease. To improve the translational value of this model, four modifications to the classic elastase perfusion procedure (PPE) in relation to human aneurysm morphology were conducted. METHODS: In ten week old male C57BL/6J wild type mice the PPE procedure was modified in four ways using two different techniques. Flow alteration was simulated by partial ligation of the common iliac artery or the distal aorta. Additionally, careful exploration of the abdominal aortic branches allowed PPE induction at the suprarenal and iliac level. Molecular biology, ultrasound, and immunohistochemistry were used to evaluate these pilot results. RESULTS: Two aortic outflow obstructions simulating distal aortic or iliac stenosis significantly increase murine AAA diameter (p = .046), and affect local vascular wall remodelling. Suprarenal aortic dissection allows a juxtarenal aneurysm to be induced, similar to the angiotensin II induced aneurysm model. A separate investigation for canonical activation of transforming growth factor ß in the two embryonically distinct juxtarenal and infrarenal segments showed no distinct difference. Creating an aortoiliac bifurcated aneurysm completes the mimicry of human aneurysm morphology. CONCLUSION: The alteration of the classic PPE aneurysm by outflow modulation and further elastase perfusion to the juxtarenal and aortoiliac segment modifies morphology and diameter, and thus increases the translational value in future research.

H19 Induces Abdominal Aortic Aneurysm Development and Progression.

BACKGROUND: Long noncoding RNAs have emerged as critical molecular regulators in various biological processes and diseases. Here we sought to identify and functionally characterize long noncoding RNAs as potential mediators in abdominal aortic aneurysm development. METHODS: We profiled RNA transcript expression in 2 murine abdominal aortic aneurysm models, Angiotensin II (ANGII) infusion in apolipoprotein E-deficient ( ApoE-/-) mice (n=8) and porcine pancreatic elastase instillation in C57BL/6 wild-type mice (n=12). The long noncoding RNA H19 was identified as 1 of the most highly upregulated transcripts in both mouse aneurysm models compared with sham-operated controls. This was confirmed by quantitative reverse transcription-polymerase chain reaction and in situ hybridization. RESULTS: Experimental knock-down of H19, utilizing site-specific antisense oligonucleotides (LNA-GapmeRs) in vivo, significantly limited aneurysm growth in both models. Upregulated H19 correlated with smooth muscle cell (SMC) content and SMC apoptosis in progressing aneurysms. Importantly, a similar pattern could be observed in human abdominal aortic aneurysm tissue samples, and in a novel preclinical LDLR-/- (low-density lipoprotein receptor) Yucatan mini-pig aneurysm model. In vitro knock-down of H19 markedly decreased apoptotic rates of cultured human aortic SMCs, whereas overexpression of H19 had the opposite effect. Notably, H19-dependent apoptosis mechanisms in SMCs appeared to be independent of miR-675, which is embedded in the first exon of the H19 gene. A customized transcription factor array identified hypoxia-inducible factor 1α as the main downstream effector. Increased SMC apoptosis was associated with cytoplasmic interaction between H19 and hypoxia-inducible factor 1α and sequential p53 stabilization. Additionally, H19 induced transcription of hypoxia-inducible factor 1α via recruiting the transcription factor specificity protein 1 to the promoter region. CONCLUSIONS: The long noncoding RNA H19 is a novel regulator of SMC survival in abdominal aortic aneurysm development and progression. Inhibition of H19 expression might serve as a novel molecular therapeutic target for aortic aneurysm disease.

Local Delivery of miR-21 Stabilizes Fibrous Caps in Vulnerable Atherosclerotic Lesions.

miRNAs are potential regulators of carotid artery stenosis and concordant vulnerable atherosclerotic plaques. Hence, we analyzed miRNA expression in laser captured micro-dissected fibrous caps of either ruptured or stable plaques (n = 10 each), discovering that miR-21 was significantly downregulated in unstable lesions. To functionally evaluate miR-21 in plaque vulnerability, miR-21 and miR-21/apolipoprotein-E double-deficient mice (Apoe-/-miR-21-/-) were assessed. miR-21-/- mice lacked sufficient smooth muscle cell proliferation in response to carotid ligation injury. When exposing Apoe-/-miR-21-/- mice to an inducible plaque rupture model, they presented with more atherothrombotic events (93%) compared with miR-21+/+Apoe-/- mice (57%). We discovered that smooth muscle cell fate in experimentally induced advanced lesions is steered via a REST-miR-21-REST feedback signaling pathway. Furthermore, Apoe-/-miR-21-/- mice presented with more pronounced atherosclerotic lesions, greater foam cell formation, and substantially higher levels of arterial macrophage infiltration. Local delivery of a miR-21 mimic using ultrasound-targeted microbubbles into carotid plaques rescued the vulnerable plaque rupture phenotype. In the present study, we identify miR-21 as a key modulator of pathologic processes in advanced atherosclerosis. Targeted, lesion site-specific overexpression of miR-21 can stabilize vulnerable plaques.

MicroRNA-210 Enhances Fibrous Cap Stability in Advanced Atherosclerotic Lesions.

RATIONALE: In the search for markers and modulators of vascular disease, microRNAs (miRNAs) have emerged as potent therapeutic targets. OBJECTIVE: To investigate miRNAs of clinical interest in patients with unstable carotid stenosis at risk of stroke. METHODS AND RESULTS: Using patient material from the BiKE (Biobank of Karolinska Endarterectomies), we profiled miRNA expression in patients with stable versus unstable carotid plaque. A polymerase chain reaction-based miRNA array of plasma, sampled at the carotid lesion site, identified 8 deregulated miRNAs (miR-15b, miR-29c, miR-30c/d, miR-150, miR-191, miR-210, and miR-500). miR-210 was the most significantly downregulated miRNA in local plasma material. Laser capture microdissection and in situ hybridization revealed a distinct localization of miR-210 in fibrous caps. We confirmed that miR-210 directly targets the tumor suppressor gene APC (adenomatous polyposis coli), thereby affecting Wnt (Wingless-related integration site) signaling and regulating smooth muscle cell survival, as well as differentiation in advanced atherosclerotic lesions. Substantial changes in arterial miR-210 were detectable in 2 rodent models of vascular remodeling and plaque rupture. Modulating miR-210 in vitro and in vivo improved fibrous cap stability with implications for vascular disease. CONCLUSIONS: An unstable carotid plaque at risk of stroke is characterized by low expression of miR-210. miR-210 contributes to stabilizing carotid plaques through inhibition of APC, ensuring smooth muscle cell survival. We present local delivery of miR-210 as a therapeutic approach for prevention of atherothrombotic vascular events.

Aneurysm miRNA Signature Differs, Depending on Disease Localization and Morphology.

Limited comprehension of aneurysm pathology has led to inconclusive results from clinical trials. miRNAs are key regulators of post-translational gene modification and are useful tools in elucidating key features of aneurysm pathogenesis in distinct entities of abdominal and popliteal aneurysms. Here, surgically harvested specimens from 19 abdominal aortic aneurysm (AAA) and 8 popliteal artery aneurysm (PAA) patients were analyzed for miRNA expression and histologically classified regarding extracellular matrix (ECM) remodeling and inflammation. DIANA-based computational target prediction and pathway enrichment analysis verified our results, as well as previous ones. miRNA-362, -19b-1, -194, -769, -21 and -550 were significantly down-regulated in AAA samples depending on degree of inflammation. Similar or inverse regulation was found for miR-769, 19b-1 and miR-550, -21, whereas miR-194 and -362 were unaltered in PAA. In situ hybridization verified higher expression of miR-550 and -21 in PAA compared to AAA and computational analysis for target genes and pathway enrichment affirmed signal transduction, cell-cell-interaction and cell degradation pathways, in line with previous results. Despite the vague role of miRNAs for potential diagnostic and treatment purposes, the number of candidates from tissue signature studies is increasing. Tissue morphology influences subsequent research, yet comparison of distinct entities of aneurysm disease can unravel core pathways.

Local MicroRNA Modulation Using a Novel Anti-miR-21-Eluting Stent Effectively Prevents Experimental In-Stent Restenosis.

OBJECTIVE: Despite advances in stent technology for vascular interventions, in-stent restenosis (ISR) because of myointimal hyperplasia remains a major complication. APPROACH AND RESULTS: We investigated the regulatory role of microRNAs in myointimal hyperplasia/ISR, using a humanized animal model in which balloon-injured human internal mammary arteries with or without stenting were transplanted into Rowett nude rats, followed by microRNA profiling. miR-21 was the only significantly upregulated candidate. In addition, miR-21 expression was increased in human tissue samples from patients with ISR compared with coronary artery disease specimen. We systemically repressed miR-21 via intravenous fluorescein-tagged-locked nucleic acid-anti-miR-21 (anti-21) in our humanized myointimal hyperplasia model. As expected, suppression of vascular miR-21 correlated dose dependently with reduced luminal obliteration. Furthermore, anti-21 did not impede reendothelialization. However, systemic anti-miR-21 had substantial off-target effects, lowering miR-21 expression in liver, heart, lung, and kidney with concomitant increase in serum creatinine levels. We therefore assessed the feasibility of local miR-21 suppression using anti-21-coated stents. Compared with bare-metal stents, anti-21-coated stents effectively reduced ISR, whereas no significant off-target effects could be observed. CONCLUSION: This study demonstrates the efficacy of an anti-miR-coated stent for the reduction of ISR.

Transcription Factor Runx2 Promotes Aortic Fibrosis and Stiffness in Type 2 Diabetes Mellitus.

RATIONALE: Accelerated arterial stiffening is a major complication of diabetes mellitus with no specific therapy available to date. OBJECTIVE: The present study investigates the role of the osteogenic transcription factor runt-related transcription factor 2 (Runx2) as a potential mediator and therapeutic target of aortic fibrosis and aortic stiffening in diabetes mellitus. METHODS AND RESULTS: Using a murine model of type 2 diabetes mellitus (db/db mice), we identify progressive structural aortic stiffening that precedes the onset of arterial hypertension. At the same time, Runx2 is aberrantly upregulated in the medial layer of db/db aortae, as well as in thoracic aortic samples from patients with type 2 diabetes mellitus. Vascular smooth muscle cell-specific overexpression of Runx2 in transgenic mice increases expression of its target genes, Col1a1 and Col1a2, leading to medial fibrosis and aortic stiffening. Interestingly, increased Runx2 expression per se is not sufficient to induce aortic calcification. Using in vivo and in vitro approaches, we further demonstrate that expression of Runx2 in diabetes mellitus is regulated via a redox-sensitive pathway that involves a direct interaction of NF-κB with the Runx2 promoter. CONCLUSIONS: In conclusion, this study highlights Runx2 as a previously unrecognized inducer of vascular fibrosis in the setting of diabetes mellitus, promoting arterial stiffness irrespective of calcification.