Integrative gene regulatory network analysis discloses key driver genes of fibromuscular dysplasia.

Fibromuscular dysplasia (FMD) is a poorly understood disease affecting 3-5% of adult females. The pathobiology of FMD involves arterial lesions of stenosis, dissection, tortuosity, dilation and aneurysm, which can lead to hypertension, stroke, myocardial infarction and even death. Currently, there are no animal models for FMD and few insights as to its pathobiology. In this study, by integrating DNA genotype and RNA sequence data from primary fibroblasts of 83 patients with FMD and 71 matched healthy controls, we inferred 18 gene regulatory co-expression networks, four of which were found to act together as an FMD-associated supernetwork in the arterial wall. After in vivo perturbation of this co-expression supernetwork by selective knockout of a top network key driver, mice developed arterial dilation, a hallmark of FMD. Molecular studies indicated that this supernetwork governs multiple aspects of vascular cell physiology and functionality, including collagen/matrix production. These studies illuminate the complex causal mechanisms of FMD and suggest a potential therapeutic avenue for this challenging disease.

Delayed CCL23 response is associated with poor outcomes after cardiac arrest.

Chemokines, a family of chemotactic cytokines, mediate leukocyte migration to and entrance into inflamed tissue, contributing to the intensity of local inflammation. We performed an analysis of chemokine and immune cell responses to cardiac arrest (CA). Forty-two patients resuscitated from cardiac arrest were analyzed, and twenty-two patients who underwent coronary artery bypass grafting (CABG) surgery were enrolled. Quantitative antibody array, chemokines, and endotoxin quantification were performed using the patients blood. Analysis of CCL23 production in neutrophils obtained from CA patients and injected into immunodeficient mice after CA and cardiopulmonary resuscitation (CPR) were done using flow cytometry. The levels of CCL2, CCL4, and CCL23 are increased in CA patients. Temporal dynamics were different for each chemokine, with early increases in CCL2 and CCL4, followed by a delayed elevation in CCL23 at forty-eight hours after CA. A high level of CCL23 was associated with an increased number of neutrophils, neuron-specific enolase (NSE), worse cerebral performance category (CPC) score, and higher mortality. To investigate the role of neutrophil activation locally in injured brain tissue, we used a mouse model of CA/CPR. CCL23 production was increased in human neutrophils that infiltrated mouse brains compared to those in the peripheral circulation. It is known that an early intense inflammatory response (within hours) is associated with poor outcomes after CA. Our data indicate that late activation of neutrophils in brain tissue may also promote ongoing injury via the production of CCL23 and impair recovery after cardiac arrest.

Lifetime evaluation of left ventricular structure and function in male ApoE null mice after gamma and space-type radiation exposure.

The space radiation (IR) environment contains high charge and energy (HZE) nuclei emitted from galactic cosmic rays with the ability to overcome current shielding strategies, posing increased IR-induced cardiovascular disease risks for astronauts on prolonged space missions. Little is known about the effect of 5-ion simplified galactic cosmic ray simulation (simGCRsim) exposure on left ventricular (LV) function. Three-month-old, age-matched male Apolipoprotein E (ApoE) null mice were irradiated with 137Cs gamma (γ; 100, 200, and 400 cGy) and simGCRsim (50, 100, 150 cGy all at 500 MeV/nucleon (n)). LV function was assessed using transthoracic echocardiography at early/acute (14 and 28 days) and late/degenerative (365, 440, and 660 days) times post-irradiation. As early as 14 and 28-days post IR, LV systolic function was reduced in both IR groups across all doses. At 14 days post-IR, 150 cGy simGCRsim-IR mice had decreased diastolic wall strain (DWS), suggesting increased myocardial stiffness. This was also observed later in 100 cGy γ-IR mice at 28 days. At later stages, a significant decrease in LV systolic function was observed in the 400 cGy γ-IR mice. Otherwise, there was no difference in the LV systolic function or structure at the remaining time points across the IR groups. We evaluated the expression of genes involved in hemodynamic stress, cardiac remodeling, inflammation, and calcium handling in LVs harvested 28 days post-IR. At 28 days post-IR, there is increased expression of Bnp and Ncx in both IR groups at the lowest doses, suggesting impaired function contributes to hemodynamic stress and altered calcium handling. The expression of Gals3 and ß-Mhc were increased in simGCRsim and γ-IR mice respectively, suggesting there may be IR-specific cardiac remodeling. IR groups were modeled to calculate the Relative Biological Effectiveness (RBE) and Radiation Effects Ratio (RER). No lower threshold was determined using the observed dose-response curves. These findings do not exclude the possibility of the existence of a lower IR threshold or the presence of IR-induced cardiovascular disease (CVD) when combined with additional space travel stressors, e.g., microgravity.

Extracellular Vesicle-Encapsulated Adeno-Associated Viruses for Therapeutic Gene Delivery to the Heart.

BACKGROUND: Adeno-associated virus (AAV) has emerged as one of the best tools for cardiac gene delivery due to its cardiotropism, long-term expression, and safety. However, a significant challenge to its successful clinical use is preexisting neutralizing antibodies (NAbs), which bind to free AAVs, prevent efficient gene transduction, and reduce or negate therapeutic effects. Here we describe extracellular vesicle-encapsulated AAVs (EV-AAVs), secreted naturally by AAV-producing cells, as a superior cardiac gene delivery vector that delivers more genes and offers higher NAb resistance. METHODS: We developed a 2-step density-gradient ultracentrifugation method to isolate highly purified EV-AAVs. We compared the gene delivery and therapeutic efficacy of EV-AAVs with an equal titer of free AAVs in the presence of NAbs, both in vitro and in vivo. In addition, we investigated the mechanism of EV-AAV uptake in human left ventricular and human induced pluripotent stem cell-derived cardiomyocytes in vitro and mouse models in vivo using a combination of biochemical techniques, flow cytometry, and immunofluorescence imaging. RESULTS: Using cardiotropic AAV serotypes 6 and 9 and several reporter constructs, we demonstrated that EV-AAVs deliver significantly higher quantities of genes than AAVs in the presence of NAbs, both to human left ventricular and human induced pluripotent stem cell-derived cardiomyocytes in vitro and to mouse hearts in vivo. Intramyocardial delivery of EV-AAV9-sarcoplasmic reticulum calcium ATPase 2a to infarcted hearts in preimmunized mice significantly improved ejection fraction and fractional shortening compared with AAV9-sarcoplasmic reticulum calcium ATPase 2a delivery. These data validated NAb evasion by and therapeutic efficacy of EV-AAV9 vectors. Trafficking studies using human induced pluripotent stem cell-derived cells in vitro and mouse hearts in vivo showed significantly higher expression of EV-AAV6/9-delivered genes in cardiomyocytes compared with noncardiomyocytes, even with comparable cellular uptake. Using cellular subfraction analyses and pH-sensitive dyes, we discovered that EV-AAVs were internalized into acidic endosomal compartments of cardiomyocytes for releasing and acidifying AAVs for their nuclear uptake. CONCLUSIONS: Together, using 5 different in vitro and in vivo model systems, we demonstrate significantly higher potency and therapeutic efficacy of EV-AAV vectors compared with free AAVs in the presence of NAbs. These results establish the potential of EV-AAV vectors as a gene delivery tool to treat heart failure.

Lifetime Evaluation of Left Ventricular Structure and Function in Male C57BL/6J Mice after Gamma and Space-Type Radiation Exposure.

The lifetime effects of space irradiation (IR) on left ventricular (LV) function are unknown. The cardiac effects induced by space-type IR, specifically 5-ion simplified galactic cosmic ray simulation (simGCRsim), are yet to be discovered. Three-month-old, age-matched, male C57BL/6J mice were irradiated with 137Cs gamma (γ; 100, 200 cGy) and simGCRsim (50 and 100 cGy). LV function was assessed via transthoracic echocardiography at 14 and 28 days (early), and at 365, 440, and 660 (late) days post IR. We measured the endothelial function marker brain natriuretic peptide in plasma at three late timepoints. We assessed the mRNA expression of the genes involved in cardiac remodeling, fibrosis, inflammation, and calcium handling in LVs harvested at 660 days post IR. All IR groups had impaired global LV systolic function at 14, 28, and 365 days. At 660 days, 50 cGy simGCRsim-IR mice exhibited preserved LV systolic function with altered LV size and mass. At this timepoint, the simGCRsim-IR mice had elevated levels of cardiac fibrosis, inflammation, and hypertrophy markers Tgfß1, Mcp1, Mmp9, and ßmhc, suggesting that space-type IR may induce the cardiac remodeling processes that are commonly associated with diastolic dysfunction. IR groups showing statistical significance were modeled to calculate the Relative Biological Effectiveness (RBE) and Radiation Effects Ratio (RER). The observed dose-response shape did not indicate a lower threshold at these IR doses. A single full-body IR at doses of 100-200 cGy for γ-IR, and 50-100 cGy for simGCRsim-IR decreases the global LV systolic function in WT mice as early as 14 and 28 days after exposure, and at 660 days post IR. Interestingly, there is an intermediate time point (365 days) where the impairment in LV function is observed. These findings do not exclude the possibility of increased acute or degenerative cardiovascular disease risks at lower doses of space-type IR, and/or when combined with other space travel-associated stressors such as microgravity.

AAV1.SERCA2a Gene Therapy Reverses Pulmonary Fibrosis by Blocking the STAT3/FOXM1 Pathway and Promoting the SNON/SKI Axis.

Inhibition of pulmonary fibrosis (PF) by restoring sarco/endoplasmic reticulum calcium ATPase 2a isoform (SERCA2a) expression using targeted gene therapy may be a potentially powerful new treatment approach for PF. Here, we found that SERCA2a expression was significantly decreased in lung samples from patients with PF and in the bleomycin (BLM) mouse model of PF. In the BLM-induced PF model, intratracheal aerosolized adeno-associated virus serotype 1 (AAV1) encoding for human SERCA2a (AAV1.hSERCA2a) reduces lung fibrosis and associated vascular remodeling. SERCA2a gene therapy also decreases right ventricular pressure and hypertrophy in both prevention and curative protocols. In vitro, we observed that SERCA2a overexpression inhibits fibroblast proliferation, migration, and fibroblast-to-myofibroblast transition induced by transforming growth factor ß (TGF-ß1). Thus, pro-fibrotic gene expression is prevented by blocking nuclear factor κB (NF-κB)/interleukin-6 (IL-6)-induced signal transducer and activator of transcription 3 (STAT3) activation. This effect is signaled toward an inhibitory mechanism of small mother against decapentaplegic (SMAD)/TGF-ß signaling through the repression of OTU deubiquitinase, ubiquitin aldehyde binding 1 (OTUB1) and Forkhead box M1 (FOXM1). Interestingly, this cross-inhibition leads to an increase of SKI and SnoN expression, an auto-inhibitory feedback loop of TGF-ß signaling. Collectively, our results demonstrate that SERCA2a gene transfer attenuates bleomycin (BLM)-induced PF by blocking the STAT3/FOXM1 pathway and promoting the SNON/SKI Axis. Thus, SERCA2a gene therapy may be a potential therapeutic target for PF.

FTO-Dependent N6-Methyladenosine Regulates Cardiac Function During Remodeling and Repair.

BACKGROUND: Despite its functional importance in various fundamental bioprocesses, studies of N6-methyladenosine (m6A) in the heart are lacking. Here, we show that the FTO (fat mass and obesity-associated protein), an m6A demethylase, plays a critical role in cardiac contractile function during homeostasis, remodeling, and regeneration. METHODS: We used clinical human samples, preclinical pig and mouse models, and primary cardiomyocyte cell cultures to study the functional role of m6A and FTO in the heart and in cardiomyocytes. We modulated expression of FTO by using adeno-associated virus serotype 9 (in vivo), adenovirus (both in vivo and in vitro), and small interfering RNAs (in vitro) to study its function in regulating cardiomyocyte m6A, calcium dynamics and contractility, and cardiac function postischemia. We performed methylated (m6A) RNA immunoprecipitation sequencing to map transcriptome-wide m6A, and methylated (m6A) RNA immunoprecipitation quantitative polymerase chain reaction assays to map and validate m6A in individual transcripts, in healthy and failing hearts, and in myocytes. RESULTS: We discovered that FTO has decreased expression in failing mammalian hearts and hypoxic cardiomyocytes, thereby increasing m6A in RNA and decreasing cardiomyocyte contractile function. Improving expression of FTO in failing mouse hearts attenuated the ischemia-induced increase in m6A and decrease in cardiac contractile function. This is performed by the demethylation activity of FTO, which selectively demethylates cardiac contractile transcripts, thus preventing their degradation and improving their protein expression under ischemia. In addition, we demonstrate that FTO overexpression in mouse models of myocardial infarction decreased fibrosis and enhanced angiogenesis. CONCLUSIONS: Collectively, our study demonstrates the functional importance of the FTO-dependent cardiac m6A methylome in cardiac contraction during heart failure and provides a novel mechanistic insight into the therapeutic mechanisms of FTO.

Cardiac Sca-1+ Cells Are Not Intrinsic Stem Cells for Myocardial Development, Renewal, and Repair.

BACKGROUND: For more than a decade, Sca-1+ cells within the mouse heart have been widely recognized as a stem cell population with multipotency that can give rise to cardiomyocytes, endothelial cells, and smooth muscle cells in vitro and after cardiac grafting. However, the developmental origin and authentic nature of these cells remain elusive. METHODS: Here, we used a series of high-fidelity genetic mouse models to characterize the identity and regenerative potential of cardiac resident Sca-1+ cells. RESULTS: With these novel genetic tools, we found that Sca-1 does not label cardiac precursor cells during early embryonic heart formation. Postnatal cardiac resident Sca-1+ cells are in fact a pure endothelial cell population. They retain endothelial properties and exhibit minimal cardiomyogenic potential during development, normal aging and upon ischemic injury. CONCLUSIONS: Our study provides definitive insights into the nature of cardiac resident Sca-1+ cells. The observations challenge the current dogma that cardiac resident Sca-1+ cells are intrinsic stem cells for myocardial development, renewal, and repair, and suggest that the mechanisms of transplanted Sca-1+ cells in heart repair need to be reassessed.

Insulin-Like Growth Factor 1 Receptor-Dependent Pathway Drives Epicardial Adipose Tissue Formation After Myocardial Injury.

BACKGROUND: Epicardial adipose tissue volume and coronary artery disease are strongly associated, even after accounting for overall body mass. Despite its pathophysiological significance, the origin and paracrine signaling pathways that regulate epicardial adipose tissue's formation and expansion are unclear. METHODS: We used a novel modified mRNA-based screening approach to probe the effect of individual paracrine factors on epicardial progenitors in the adult heart. RESULTS: Using 2 independent lineage-tracing strategies in murine models, we show that cells originating from the Wt1+ mesothelial lineage, which includes epicardial cells, differentiate into epicardial adipose tissue after myocardial infarction. This differentiation process required Wt1 expression in this lineage and was stimulated by insulin-like growth factor 1 receptor (IGF1R) activation. IGF1R inhibition within this lineage significantly reduced its adipogenic differentiation in the context of exogenous, IGF1-modified mRNA stimulation. Moreover, IGF1R inhibition significantly reduced Wt1 lineage cell differentiation into adipocytes after myocardial infarction. CONCLUSIONS: Our results establish IGF1R signaling as a key pathway that governs epicardial adipose tissue formation in the context of myocardial injury by redirecting the fate of Wt1+ lineage cells. Our study also demonstrates the power of modified mRNA -based paracrine factor library screening to dissect signaling pathways that govern progenitor cell activity in homeostasis and disease.

Impact of cardiac-specific expression of CD39 on myocardial infarct size in mice.

AIMS: Prior work suggests that ischemic preconditioning increases the level of CD39 in the heart and contributes to cardiac protection. Therefore, we examined if targeted cardiac expression of CD39 protects against myocardial injury. MAIN METHODS: Mice with cardiac-specific expression of human CD39 (αMHC/hCD39-Tg) were generated, characterized and subjected to left coronary artery ischemia-reperfusion injury and infarct size at 24h following injury quantified. KEY FINDINGS: αMHC/hCD39-Tg mice have increased in cardiac ATPase and ADPase activity compared to WT littermates. The increased activity in αMHC/hCD39-mice was inhibited by the CD39 antagonist sodium polyoxotungstate (POM-1). Measurement of basal cardiac function by echocardiography revealed that αMHC/hCD39-Tg mice have a lower resting heart rate and increased stroke volume. In response to myocardial ischemia, systolic and diastolic function was better preserved in αMHC/hCD39-Tg compared to WT mice. Comparison of Tau also revealed preserved cardiac relaxation during ischemia in αMHC/hCD39-Tg hearts. Assessment of myocardial infarct size in response to 60min of ischemia and 24h of reperfusion demonstrated a significant reduction in infarct size in αMHC/hCD39-Tg hearts. Analysis of isolated cardiomyocytes revealed no basal difference in calcium transients between WT and αMHC/hCD39-Tg cardiomyocytes. However, in response to isoproterenol stimulation, there was a trend toward lower calcium transients in αMHC/hCD39 cardiomyocytes suggesting less calcium accumulation in response to metabolic stress. SIGNIFICANCE: Cardiac-specific expression of CD39 reduces myocardial dysfunction and infarct size following ischemia-reperfusion injury. Increasing nucleotidase expression in the heart may be a novel approach to protect the heart from ischemic injury.

Role of the CD39/CD73 Purinergic Pathway in Modulating Arterial Thrombosis in Mice.

OBJECTIVE: Circulating blood cells and endothelial cells express ectonucleoside triphosphate diphosphohydrolase-1 (CD39) and ecto-5'-nucleotidase (CD73). CD39 hydrolyzes extracellular ATP or ADP to AMP. CD73 hydrolyzes AMP to adenosine. The goal of this study was to examine the interplay between CD39 and CD73 cascade in arterial thrombosis. APPROACH AND RESULTS: To determine how CD73 activity influences in vivo thrombosis, the time to ferric chloride-induced arterial thrombosis was measured in CD73-null mice. In response to 5% FeCl3, but not to 10% FeCl3, there was a significant decrease in the time to thrombosis in CD73-null mice compared with wild-type mice. In mice overexpressing CD39, ablation of CD73 did not inhibit the prolongation in the time to thrombosis conveyed by CD39 overexpression. However, the CD73 inhibitor α-ß-methylene-ADP nullified the prolongation in the time to thrombosis in human CD39 transgenic (hC39-Tg)/CD73-null mice. To determine whether hematopoietic-derived cells or endothelial cell CD39 activity regulates in vivo arterial thrombus, bone marrow transplant studies were conducted. FeCl3-induced arterial thrombosis in chimeric mice revealed a significant prolongation in the time to thrombosis in hCD39-Tg reconstituted wild-type mice, but not on wild-type reconstituted hCD39-Tg mice. Monocyte depletion with clodronate-loaded liposomes normalized the time to thrombosis in hCD39-Tg mice compared with hCD39-Tg mice treated with control liposomes, demonstrating that increased CD39 expression on monocytes protects against thrombosis. CONCLUSIONS: These data demonstrate that ablation of CD73 minimally effects in vivo thrombosis, but increased CD39 expression on hematopoietic-derived cells, especially monocytes, attenuates in vivo arterial thrombosis.

Extracellular nucleotide regulation and signaling in cardiac fibrosis.

Following myocardial infarction, purinergic nucleotides and nucleosides are released via non-specific and specific mechanisms in response to cellular activation, stress, or injury. These extracellular nucleotides are potent mediators of physiologic and pathologic responses, contributing to the inflammatory and fibrotic milieu within the injured myocardium. Via autocrine or paracrine signaling, cell-specific effects occur through differentially expressed purinergic receptors of the P2X, P2Y, and P1 families. Nucleotide activation of the ionotropic (ligand-gated) purine receptors (P2X) and several of the metabotropic (G-protein-coupled) purine receptors (P2Y) or adenosine activation of the P1 receptors can have profound effects on inflammatory cell function, fibroblast function, and cardiomyocyte function. Extracellular nucleotidases that hydrolyze released nucleotides regulate the magnitude and duration of purinergic signaling. While there are numerous studies on the role of the purinergic signaling pathway in cardiovascular disease, the extent to which the purinergic signaling pathway modulates cardiac fibrosis is incompletely understood. Here we provide an overview of the current understanding of how the purinergic signaling pathway modulates cardiac fibroblast function and myocardial fibrosis.

The association between let-7, RAS and HIF-1α in Ewing Sarcoma tumor growth.

Ewing Sarcoma (ES) is the second most common primary malignant bone tumor in children and adolescents. microRNAs (miRNAs) are involved in cancer as tumor suppressors or oncogenes. We studied the involvement of miRNAs located on chromosomes 11q and 22q that participate in the most common translocation in ES. Of these, we focused on 3 that belong to the let-7 family.We studied the expression levels of let-7a, and let-7b and detected a significant correlation between low expression of let-7b and increased risk of relapse. let-7 is known to be a negative regulator of the RAS oncogene. Indeed, we detected an inverse association between the expression of let-7 and RAS protein levels and its downstream target p-ERK, following transfection of let-7 mimics and inhibitors. Furthermore, we identified let-7 as a negative regulator of HIF-1α and EWS-FLI-1. Moreover, we were able to show that HIF-1α directly binds to the EWS-FLI-1 promoter. Salirasib treatment in-vitro resulted in the reduction of cell viability, migration ability, and in the decrease of cells in S-phase. A significant reduction in tumor burden and in the expression levels of both HIF-1α and EWS-FLI-1 proteins were observed in mice after treatment.Our results support the hypothesis that let-7 is a tumor suppressor that negatively regulates RAS, also in ES, and that HIF-1α may contribute to the aggressive metastatic behavior of ES. Moreover, the reduction in the tumor burden in a mouse model of ES following Salirasib treatment, suggests therapeutic potential for this RAS inhibitor in ES.

Glucagon-like peptide-1 reduces hepatic lipogenesis via activation of AMP-activated protein kinase.

BACKGROUND & AIMS: Glucagon-like peptide-1 (GLP-1), a gut-derived peptide degraded by dipeptidyl peptidase-4 (DPP4), stimulates insulin secretion in response to nutrients, yet its direct effect on the liver is controversial. We investigated the effects of GLP-1 on hepatic fat and glucose metabolism and elucidated its mechanism of action. METHODS: Hepatic fat metabolism, including lipogenic enzymes and signal transduction regulators, was assessed in livers of DPP4-deficient rats (DPP4-) with chronically elevated GLP-1 and in GLP-1-treated primary hepatocytes. The effect of chronic elevated GLP-1 on insulin sensitivity was measured using the hyperinsulinemic-euglycemic clamp. RESULTS: Normal and high fat diet fed DPP4-rats displayed reduced hepatic triglycerides, accompanied by down-regulation of lipogenesis enzymes and parallel up-regulation of carnitine palmitoyltransferase-1, a key enzyme in fatty acid ß-oxidation. In vitro studies demonstrated that these effects were directly induced by GLP-1. Mechanistically, GLP-1 increased cAMP in hepatocytes, resulting in the phosphorylation of cAMP-activated protein kinase (AMPK), a suppressor of lipogenesis. Indeed, hepatocytes expressing a dominant negative Ad-DN-AMPK displayed attenuated GLP-1 effects on AMPK phosphorylation and its downstream lipogenic targets. Importantly, normoglycemic DPP4-rats did not display improved hepatic insulin sensitivity in vivo, suggesting a direct effect of GLP-1 on fat metabolism. Finally, DPP4-rats expressed lower levels of hepatic proinflammatory and profibrotic cytokines in response to nutrient stimuli. CONCLUSIONS: GLP-1 suppresses hepatic lipogenesis via activation of the AMPK pathway. GLP-1 inhibitory effects on hepatic fat accumulation and nutrient-induced hepatic proinflammatory response suggest GLP-1 analogs as novel therapies for non-alcoholic fatty liver diseases.