Age-Dependent RGS5 Loss in Pericytes Induces Cardiac Dysfunction and Fibrosis

BACKGROUND

Pericytes are capillary-associated mural cells involved in the maintenance and stability of the vascular network. Although aging is one of the main risk factors for cardiovascular disease, the consequences of aging on cardiac pericytes are unknown.

METHODS

In this study, we have combined single-nucleus RNA sequencing and histological analysis to determine the effects of aging on cardiac pericytes. Furthermore, we have conducted in vivo and in vitro analysis of RGS5 (regulator of G-protein signaling 5) loss of function and finally have performed pericytes-fibroblasts coculture studies to understand the effect of RGS5 deletion in pericytes on the neighboring fibroblasts.

RESULTS

Aging reduced the pericyte area and capillary coverage in the murine heart. Single-nucleus RNA sequencing analysis further revealed that the expression of Rgs5 was reduced in cardiac pericytes from aged mice. In vivo and in vitro studies showed that the deletion of RGS5 impaired cardiac function, induced fibrosis, and morphological changes in pericytes characterized by a profibrotic gene expression signature and the expression of different ECM (extracellular matrix) components and growth factors, for example, TGFB2 and PDGFB. Indeed, culturing fibroblasts with the supernatant of RGS5-deficient pericytes induced their activation as evidenced by the increased expression of αSMA (alpha smooth muscle actin) in a TGFβ (transforming growth factor beta)2-dependent mechanism.

CONCLUSIONS

Our results have identified RGS5 as a crucial regulator of pericyte function during cardiac aging. The deletion of RGS5 causes cardiac dysfunction and induces myocardial fibrosis, one of the hallmarks of cardiac aging.

Determination of the absolute intensity of the 1205 keV γ-ray emission from 91Y

A radiochemically pure solution of 91Y was produced by the thermal neutron fission of 235U followed by successive chemical separations to remove fission product impurities. The gamma emission rate of the 91Y 1205 keV gamma was measured using multiple high purity germanium gamma spectrometers previously calibrated for counting efficiency using a certificated mixed nuclide gamma standard. The activity concentration of the 91Y was subsequently standardised by liquid scintillation counting. From the combination the activity concentration and gamma emission intensity, the absolute intensity of the 1205 keV gamma emission was derived as 0.2297(39)%. This data agrees within the quoted uncertainties with the absolute intensity of 0.26(4)% published in nuclear data sheets A=91 (Baglin, 2013), but reduces the uncertainty by an order of magnitude.

DNMT3A clonal hematopoiesis-driver mutations induce cardiac fibrosis by paracrine activation of fibroblasts

Hematopoietic mutations in epigenetic regulators like DNA methyltransferase 3 alpha (DNMT3A), play a pivotal role in driving clonal hematopoiesis of indeterminate potential (CHIP), and are associated with unfavorable outcomes in patients suffering from heart failure (HF). However, the precise interactions between CHIP-mutated cells and other cardiac cell types remain unknown. Here, we identify fibroblasts as potential partners in interactions with CHIP-mutated monocytes. We used combined transcriptomic data derived from peripheral blood mononuclear cells of HF patients, both with and without CHIP, and cardiac tissue. We demonstrate that inactivation of DNMT3A in macrophages intensifies interactions with cardiac fibroblasts and increases cardiac fibrosis. DNMT3A inactivation amplifies the release of heparin-binding epidermal growth factor-like growth factor, thereby facilitating activation of cardiac fibroblasts. These findings identify a potential pathway of DNMT3A CHIP-driver mutations to the initiation and progression of HF and may also provide a compelling basis for the development of innovative anti-fibrotic strategies.

Improved integration of single-cell transcriptome data demonstrates common and unique signatures of heart failure in mice and humans

BACKGROUND

Cardiovascular research heavily relies on mouse (Mus musculus) models to study disease mechanisms and to test novel biomarkers and medications. Yet, applying these results to patients remains a major challenge and often results in noneffective drugs. Therefore, it is an open challenge of translational science to develop models with high similarities and predictive value. This requires a comparison of disease models in mice with diseased tissue derived from humans.

RESULTS

To compare the transcriptional signatures at single-cell resolution, we implemented an integration pipeline called OrthoIntegrate, which uniquely assigns orthologs and therewith merges single-cell RNA sequencing (scRNA-seq) RNA of different species. The pipeline has been designed to be as easy to use and is fully integrable in the standard Seurat workflow.We applied OrthoIntegrate on scRNA-seq from cardiac tissue of heart failure patients with reduced ejection fraction (HFrEF) and scRNA-seq from the mice after chronic infarction, which is a commonly used mouse model to mimic HFrEF. We discovered shared and distinct regulatory pathways between human HFrEF patients and the corresponding mouse model. Overall, 54% of genes were commonly regulated, including major changes in cardiomyocyte energy metabolism. However, several regulatory pathways (e.g., angiogenesis) were specifically regulated in humans.

CONCLUSIONS

The demonstration of unique pathways occurring in humans indicates limitations on the comparability between mice models and human HFrEF and shows that results from the mice model should be validated carefully. OrthoIntegrate is publicly accessible (https://github.com/MarianoRuzJurado/OrthoIntegrate) and can be used to integrate other large datasets to provide a general comparison of models with patient data.

Single-nuclear transcriptome profiling identifies persistent fibroblast activation in hypertrophic and failing human hearts of patients with longstanding disease

AIMS

Cardiac fibrosis drives the progression of heart failure in ischaemic and hypertrophic cardiomyopathy. Therefore, the development of specific anti-fibrotic treatment regimens to counteract cardiac fibrosis is of high clinical relevance. Hence, this study examined the presence of persistent fibroblast activation during longstanding human heart disease at a single-cell resolution to identify putative therapeutic targets to counteract pathological cardiac fibrosis in patients.

METHODS AND RESULTS

We used single-nuclei RNA sequencing with human tissues from two samples of one healthy donor, and five hypertrophic and two failing hearts. Unsupervised sub-clustering of 7110 nuclei led to the identification of 7 distinct fibroblast clusters. De-convolution of cardiac fibroblast heterogeneity revealed a distinct population of human cardiac fibroblasts with a molecular signature of persistent fibroblast activation and a transcriptional switch towards a pro-fibrotic extra-cellular matrix composition in patients with established cardiac hypertrophy and heart failure. This sub-cluster was characterized by high expression of POSTN, RUNX1, CILP, and a target gene adipocyte enhancer-binding protein 1 (AEBP1) (all P < 0.001). Strikingly, elevated circulating AEBP1 blood level were also detected in a validation cohort of patients with confirmed cardiac fibrosis and hypertrophic cardiomyopathy by cardiac magnetic resonance imaging (P < 0.01). Since endogenous AEBP1 expression was increased in patients with established cardiac hypertrophy and heart failure, we assessed the functional consequence of siRNA-mediated AEBP1 silencing in human cardiac fibroblasts. Indeed, AEBP1 silencing reduced proliferation, migration, and fibroblast contractile capacity and α-SMA gene expression, which is a hallmark of fibroblast activation (all P < 0.05). Mechanistically, the anti-fibrotic effects of AEBP1 silencing were linked to transforming growth factor-beta pathway modulation.

CONCLUSION

Together, this study identifies persistent fibroblast activation in patients with longstanding heart disease, which might be detected by circulating AEBP1 and therapeutically modulated by its targeted silencing in human cardiac fibroblasts.

Disrupted Binding of Cystathionine γ-Lyase to p53 Promotes Endothelial Senescence

BACKGROUND

Advanced age is unequivocally linked to the development of cardiovascular disease; however, the mechanisms resulting in reduced endothelial cell regeneration remain poorly understood. Here, we investigated novel mechanisms involved in endothelial cell senescence that impact endothelial cell transcription and vascular repair after injury.

METHODS

Native endothelial cells were isolated from young (20±3.4 years) and aged (80±2.3 years) individuals and subjected to molecular analyses to assess global transcriptional and metabolic changes. In vitro studies were conducted using primary human and murine endothelial cells. A murine aortic re-endothelialization model was used to examine endothelial cell regenerative capacity in vivo.

RESULTS

RNA sequencing of native endothelial cells revealed that aging resulted in p53-mediated reprogramming to express senescence-associated genes and suppress glycolysis. Reduced glucose uptake and ATP contributed to attenuated assembly of the telomerase complex, which was required for endothelial cell proliferation. Enhanced p53 activity in aging was linked to its acetylation on K120 due to enhanced activity of the acetyltransferase MOZ (monocytic leukemic zinc finger). Mechanistically, p53 acetylation and translocation were, at least partially, attributed to the loss of the vasoprotective enzyme, CSE (cystathionine γ-lyase). CSE physically anchored p53 in the cytosol to prevent its nuclear translocation and CSE absence inhibited AKT (Protein kinase B)-mediated MOZ phosphorylation, which in turn increased MOZ activity and subsequently p53 acetylation. In mice, the endothelial cell-specific deletion of CSE activated p53, induced premature endothelial senescence, and arrested vascular repair after injury. In contrast, the adeno-associated virus 9-mediated re-expression of an active CSE mutant retained p53 in the cytosol, maintained endothelial glucose metabolism and proliferation, and prevented endothelial cell senescence. Adenoviral overexpression of CSE in native endothelial cells from aged individuals maintained low p53 activity and reactivated telomerase to revert endothelial cell senescence.

CONCLUSIONS

Aging-associated impairment of vascular repair is partly determined by the vasoprotective enzyme CSE.

Circular RNA circPLOD2 regulates pericyte function by targeting the transcription factor KLF4

Circular RNAs are generated by backsplicing and control cellular signaling and phenotypes. Pericytes stabilize capillary structures and play important roles in the formation and maintenance of blood vessels. Here, we characterize hypoxia-regulated circular RNAs (circRNAs) in human pericytes and show that the circular RNA of procollagen-lysine,2-oxoglutarate 5-dioxygenase-2 (circPLOD2) is induced by hypoxia and regulates pericyte functions. Silencing of circPLOD2 affects pericytes and increases proliferation, migration, and secretion of soluble angiogenic proteins, thereby enhancing endothelial migration and network capability. Transcriptional and epigenomic profiling of circPLOD2-depleted cells reveals widespread changes in gene expression and identifies the transcription factor krüppel-like factor 4 (KLF4) as a key effector of the circPLOD2-mediated changes. KLF4 depletion mimics circPLOD2 silencing, whereas KLF4 overexpression reverses the effects of circPLOD2 depletion on proliferation and endothelial-pericyte interactions. Together, these data reveal an important function of circPLOD2 in controlling pericyte proliferation and capillary formation and show that the circPLOD2-mediated regulation of KLF4 significantly contributes to the transcriptional response to hypoxia.

Aging impairs the neurovascular interface in the heart

Aging is a major risk factor for impaired cardiovascular health. Because the aging myocardium is characterized by microcirculatory dysfunction, and because nerves align with vessels, we assessed the impact of aging on the cardiac neurovascular interface. We report that aging reduces nerve density in the ventricle and dysregulates vascular-derived neuroregulatory genes. Aging down-regulates microRNA 145 (miR-145) and derepresses the neurorepulsive factor semaphorin-3A. miR-145 deletion, which increased Sema3a expression or endothelial Sema3a overexpression, reduced axon density, mimicking the aged-heart phenotype. Removal of senescent cells, which accumulated with chronological age in parallel to the decline in nerve density, rescued age-induced denervation, reversed Sema3a expression, preserved heart rate patterns, and reduced electrical instability. These data suggest that senescence-mediated regulation of nerve density contributes to age-associated cardiac dysfunction.

3Rs implementation in veterinary vaccine batch-release testing: Current state-of-the-art and future opportunities. A webinar and workshop report

Regulatory authorities require veterinary batch-release testing to confirm vaccine potency and safety, but these tests have traditionally relied on large numbers of laboratory animals. Advances in vaccine research and development offer increasing opportunities to replace in vivo testing, and some stakeholders have made significant progress in incorporating 3Rs elements in quality control strategies. A three-part event series entitled "3Rs Implementation in Veterinary Vaccine Batch-Release Testing: Current state-of-the-art and future opportunities" was jointly organized by the Animal-Free Safety Assessment Collaboration, HealthforAnimals, and the International Alliance of Biological Standardization. Two webinars and a workshop aimed to outline the state-of-the-art non-animal approaches for veterinary batch-release testing. The events included information on the state of the deletion of obsolete safety testing and the current initiatives implemented by European, North American, and Asian-Pacific stakeholders on 3Rs implementation and regulatory acceptance. The events contributed to a better understanding of the barriers to 3Rs implementation. Participants highlighted the need for open communication, continued collaboration between stakeholders, and international harmonization of regulatory requirements to help accelerate acceptance. Despite the challenges, the countries represented at this three-part event have shared their commitments to advancing the acceptance of alternative methods.

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

BACKGROUND

Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres.

METHODS

This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low-middle-income countries.

RESULTS

In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of 'single-use' consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low-middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia.

CONCLUSION

This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high- and low-middle-income countries.

The gastrointestinal status of healthy adults: a post hoc assessment of the impact of three distinct probiotics

There is a growing awareness that supplementation with probiotic bacteria can impart beneficial effects during gastrointestinal disease, but less is known about the impact of probiotics on healthy subjects. Here, we report the outcomes of a post hoc analysis of recorded daily gastrointestinal events and bowel habits completed by healthy adults participating in a placebo-controlled, single-centre, randomised, double-blind, quadruple-arm probiotic tolerability study. Extensive screening ensured the healthy status of subjects entering the study and during a 2-week pre-intervention run-in period, a burden of gastrointestinal events (stomach pains, indigestion, acid reflux, stomach tightening, nausea and vomiting, stomach rumbling, bloating, belching and flatulence) was identified suggesting GI discomfort within the population. In the subsequent 12-week intervention period with 3 distinct probiotic formulations and a matched-placebo, reductions in the incidence rates of bloating, borborygmus, stomach pains, slow faecal transit and incomplete defecations were observed in the probiotic groups compared to the placebo. These results highlighted differing responses among the probiotic formulations tested and indicated potential anti-constipation effects. Product specific modulations in circulating interleukin-6 levels and in the composition of the gut microbiota were also detected. Together, these data suggest a role for probiotic supplementation to exert beneficial effects on the gastrointestinal functioning of healthy subjects and highlight the need for further longer-term studies in healthy populations to gain a greater understanding of the impact of probiotics.

Cardiomyocyte hyperplasia and immaturity but not hypertrophy are characteristic features of patients with RASopathies

AIMS

RASopathies are caused by mutations in genes that alter the MAP kinase pathway and are marked by several malformations with cardiovascular disorders as the predominant cause of mortality. Mechanistic insights in the underlying pathogenesis in affected cardiac tissue are rare. The aim of the study was to assess the impact of RASopathy causing mutations on the human heart.

METHODS AND RESULTS

Using single cell approaches and histopathology we analyzed cardiac tissue from children with different RASopathy-associated mutations compared to age-matched dilated cardiomyopathy (DCM) and control hearts. The volume of cardiomyocytes was reduced in RASopathy conditions compared to controls and DCM patients, and the estimated number of cardiomyocytes per heart was ~4-10 times higher. Single nuclei RNA sequencing of a 13-year-old RASopathy patient (carrying a PTPN11 c.1528C > G mutation) revealed that myocardial cell composition and transcriptional patterns were similar to <1 year old DCM hearts. Additionally, immaturity of cardiomyocytes is shown by an increased MYH6/MYH7 expression ratio and reduced expression of genes associated with fatty acid metabolism. In the patient with the PTPN11 mutation activation of the MAP kinase pathway was not evident in cardiomyocytes, whereas increased phosphorylation of PDK1 and its downstream kinase Akt was detected.

CONCLUSION

In conclusion, an immature cardiomyocyte differentiation status appears to be preserved in juvenile RASopathy patients. The increased mass of the heart in such patients is due to an increase in cardiomyocyte number (hyperplasia) but not an enlargement of individual cardiomyocytes (hypertrophy).

Acute injury to the mouse carotid artery provokes a distinct healing response

Treatment of vascular stenosis with angioplasty results in acute vascular damage, which may lead to restenosis. Owing to the highly complex cellularity of blood vessels, the healing response following this damage is incompletely understood. To gain further insight into this process, scRNA-seq of mouse carotid tissue after wire injury was performed. Stages of acute inflammation, resolution and remodeling were recapitulated in these data. To identify cell types which give rise to neointima, analyses focused on smooth muscle cell and fibroblast populations, and included data integration with scRNA-seq data from myocardial infarction and atherosclerosis datasets. Following carotid injury, a subpopulation of smooth muscle cells which also arises during atherosclerosis and myocardial infarction was identified. So-called stem cell/endothelial cell/monocyte (SEM) cells are candidates for repopulating injured vessels, and were amongst the most proliferative cell clusters following wire-injury of the carotid artery. Importantly, SEM cells exhibit specific transcriptional profiles which could be therapeutically targeted. SEM cell gene expression patterns could also be detected in bulk RNA-sequencing of neointimal tissue isolated from injured carotid vessels by laser capture microdissection. These data indicate that phenotypic plasticity of smooth muscle cells is highly important to the progression of lumen loss following acute carotid injury. Interference with SEM cell formation could be an innovative approach to combat development of restenosis.

Decrease of RNA editing in the failing heart leads to induction of circRNAs

Background and purpose

Adenosine-to-Inosine (A-to-I) RNA editing is a post-transcriptional modification process that affects the secondary structure of RNAs. Changes in RNA editing have been associated with human diseases. We therefore aimed to analyze editing in the healthy and failing human heart.

Methods and results

Transcriptome sequencing of human heart samples of heart failure (HF) patients (n=20) and controls (n=10) revealed A-to-I editing as the major type of editing (&gt;80%). In HF patients, RNA editing was reduced, which was primarily attributable to Alu elements in introns of protein-coding genes. We identified 166 upregulated circRNAs in HF, with the majority showing reduced RNA editing in their parental host gene (88.3%). CircRNA expression did not correlate with their corresponding host gene (R=0.07, P&lt;0.05), suggesting that an alternative splicing mechanism gives rise to the elevated circRNA levels in HF. The RNA editing enzyme ADAR2, which binds to RNA regions that are edited from adenosine to inosine, was decreased in failing human hearts (−68.2%). In vitro, reduction of ADAR2 increased circRNA levels suggesting a causal effect of reduced ADAR2 levels on increased circRNAs in the failing human heart. To gain mechanistic insight, we examined the formation of circRNAs on one exemplary candidate. AKAP13 was among the top edited mRNAs in the human heart and gave rise to a circular transcript, which was elevated in HF. ADAR2 reduced the formation of double-stranded structures in AKAP13 pre-mRNA, thereby reducing the stability of Alu elements and the circularization of the resulting circRNA. Overexpression of circAKAP13 impaired the sarcomere regularity of human induced pluripotent stem cell-derived cardiomyocytes (−31.0%).

Conclusion

Our study shows that ADAR2 mediates A-to-I RNA editing in the human heart. We describe an alternative splicing mechanism of circRNAs in the human heart. In the healthy human heart, A-to-I RNA editing represses the formation of dsRNA structures of Alu elements thereby favoring linear mRNA splicing. Our results contribute to a better mechanistic understanding into the human-specific regulation of circRNA formation and are relevant to diseases with reduced RNA editing and increased circRNA levels.

Funding Acknowledgement

Type of funding sources: None.

Atherosclerosis licenses for an exceeding immune response in COVID-19 disease

Background

COVID-19 is characterized by emergency hematopoiesis with a dysregulated myeloid compartment, comprising proinflammatory and immunosuppressive immune cells. Preexisting cardiovascular disease (CVD) is a major risk factor for severe and fatal COVID-19 outcomes. Individuals with atherosclerosis are known to have a proinflammatory immune cell phenotype. However, the mechanisms of how CVD causes worse outcomes during SARS-Cov2 infection remain unknown.

Purpose

To investigate the mechanisms of how immune cells link atherosclerosis to worse COVID-19 outcomes

Methods

Single-cell RNA sequencing (scRNA-seq) of peripheral blood mononuclear cells (PBMCs) derived from hospitalized SARS-Cov2 infected patients in an uncomplicated phase of the disease not requiring intensive-care treatment with (n=5) and without (n=6) preexisting atherosclerosis was performed.

Results

Baseline characteristics between the two groups were similar (atherosclerosis vs. no atherosclerosis: mean age 75 vs. 70 years, oxygen requirement 2.2 vs. 3.2 l/min, CRP 10.7 vs. 6.6 mg/dl, IL-6 61.6 vs. 60.6 pg/ml, all p>0.05). In accordance with previous COVID-19 scRNA-seq studies, we found low-density neutrophils, immature neutrophils, neutrophil like plasmablasts and mostly classical monocytes in the myeloid compartment. Low-density neutrophils from patients with atherosclerosis demonstrated an increased expression of proinflammatory (IL18R1 fold change (fc) = 3.3, IL18RAP fc=1.9, HMGB2 fc=1.8, S100A12 fc=1.7, TLR2 fc=1.5, S100A9 fc=1.4 C3AR1 fc=1.8, TLR4 fc= 1.4, all adjusted p-values <1.3x10^–98) and immunosuppressive genes (IL1R2 fc=2.6, ARG1 fc=1.7, ANXA1 fc= 1.6, all adjusted p-values <4.1x10^–67). Interestingly, we found an enrichment of proinflammatory COVID-19 specific neutrophil like plasmablasts in patients with atherosclerosis (p=0.049) with an increased expression of inflammatory genes (S100A12 fc=2.5, S100A9 fc=2.5, S100A8 fc=1.8, HMGB2 fc=2.8, IL18R1 fc=3.9 S100A10 fc=2, all adjusted p-values <1.1x10^–54). In accordance, monocytes from patients with atherosclerosis showed an enrichment of inflammatory (S100A9 fc=1.6, NEAT1 fc=1.8, C3AR1 fc= 1.5, TLR2 fc= 1.5, IL13RA1 q=1.3, CCR2 fc=1.2, all p-values <1.3x10^–60) and immunomodulatory genes (IL1R2 fc=3.5, CD163 fc=2.2, all adjusted p-values <2.7x10^–87).

Conclusions

Our data show for the first time that patients with atherosclerosis have a dysregulated myeloid immune response already in the uncomplicated phase of SARS-CoV-2 infection. Upregulated genes and cell populations found in this study have previously been associated with severe COVID-19. Therefore, the enhanced inflammatory response may contribute to the worse outcome of patients with CVD and might be addressed by antiinflammatory drugs. Further efforts are needed to understand how atherosclerosis may control chromatin accessibility to predispose for an enhanced inflammatory response.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): German Heart Foundation

The role of pericytes in cardiac ageing and disease

Introduction

Cardiac disease induces remodelling which can include fibrosis, cardiomyocyte hypertrophy, cardiac dilation, and finally can lead to heart failure. Age is one of the main risk factors of cardiovascular disease and induces heart remodelling, in particular, it has profound effects on the microcirculation. Pericytes are microvascular mural cells involved in the maintenance of stability and homeostasis of the vascular network. Although the phenotypes that arise from cardiac remodelling have been well studied in cardiomyocytes, endothelial cells and fibroblasts, the effect of aging on pericytes remain largely unknown.

Purpose

The purpose of this study is to characterise pericyte responses to cardiac ageing and disease in order to determine the therapeutic potential of these mural cells to reverse, or at least reduce, structural remodelling.

Methods

We have studied 12-week-old and 18-month-old mice. We have performed histological analysis and single-nucleus-RNA-sequencing (snRNAseq). For our in vitro experiments we have used primary human pericytes.

Results

Age affects the structure of the microcirculation in the heart. Pericyte coverage is reduced and capillary diameter is increased. Gene ontology analysis of differentially expressed genes in pericytes revealed an upregulation of genes related to filopodia and actin cytoskeleton, while a reduction of genes related to focal adhesion in the pericytes of the aged heart. Interestingly, we detected a downregulation of Regulator of G-protein signalling 5 (RGS5), a repressor of GPCRs signalling. RGS5 knockdown induces a contractile, pro-inflammatory and pro-fibrotic gene expression profile reducing pericytes proliferation and migration. Mechanistically, we show that RGS5 post-transcriptionally regulates PDGFRβ, a crucial tyrosine kinase receptor for pericyte-endothelial cell interaction. RGS5 knockdown reduces the expression of the receptor at the protein level, but not at the gene expression level and furthermore reduces the phosphorylation of AKT, a downstream signal of PDGFRβ activity. Furthermore, we have identified that T-Box Transcription Factor 20 (Tbx20), a cardiogenic transcription factor, is enriched in aged pericytes. Silencing and upregulation studies have revealed that Tbx20 is a repressor of PDGFRB, the gene that encodes for PDGFRβ, and that it controls pericyte adhesion.

Conclusions

Together, these observations have identified RGS5 and Tbx20 as crucial key players maintaining pericyte function in the aged heart. We propose that RGS5 and Tbx20 regulate pericyte function by controlling PDGFRβ signalling and cellular proliferation, adhesion and migration. Given the importance of pericytes in keeping vessel homeostasis, maintaining or recovering pericyte function in context of cardiac stress would be a potential approach to reduce the malignant effects of cardiac remodelling in the aged heart.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): SFB1366 (DFG)

MODELLING GLOBAL CARBON AND RADIOCARBON CYCLES

Carbon cycle receives growing attention, in particular in connection with the climate change. Radiocarbon (14C) serves not only as the well-known basis of a dating technique but also as a tracer of the global carbon cycle, enabling one to assess the sizes of diverse compartments, fluxes between them and the related characteristic times. Mathematical modelling of the carbon cycle helps integrate the measurements, estimate the roles of underpinning processes and provide predictions, for instance on future CO2 concentrations in the atmosphere for various emission scenarios. We present a model based on a single-box atmosphere, ocean surface layer, one-dimensional diffusive ocean and two-box biota. We discuss its validation against measured data, predictions on future CO2 levels and interpretation of past events on the radiocarbon calibration curve.

Reduction of A-to-I RNA editing in the failing human heart regulates formation of circular RNAs

Alterations of RNA editing that affect the secondary structure of RNAs can cause human diseases. We therefore studied RNA editing in failing human hearts. Transcriptome sequencing showed that adenosine-to-inosine (A-to-I) RNA editing was responsible for 80% of the editing events in the myocardium. Failing human hearts were characterized by reduced RNA editing. This was primarily attributable to Alu elements in introns of protein-coding genes. In the failing left ventricle, 166 circRNAs were upregulated and 7 circRNAs were downregulated compared to non-failing controls. Most of the upregulated circRNAs were associated with reduced RNA editing in the host gene. ADAR2, which binds to RNA regions that are edited from A-to-I, was decreased in failing human hearts. In vitro, reduction of ADAR2 increased circRNA levels suggesting a causal effect of reduced ADAR2 levels on increased circRNAs in the failing human heart. To gain mechanistic insight, one of the identified upregulated circRNAs with a high reduction of editing in heart failure, AKAP13, was further characterized. ADAR2 reduced the formation of double-stranded structures in AKAP13 pre-mRNA, thereby reducing the stability of Alu elements and the circularization of the resulting circRNA. Overexpression of circAKAP13 impaired the sarcomere regularity of human induced pluripotent stem cell-derived cardiomyocytes. These data show that ADAR2 mediates A-to-I RNA editing in the human heart. A-to-I RNA editing represses the formation of dsRNA structures of Alu elements favoring canonical linear mRNA splicing and inhibiting the formation of circRNAs. The findings are relevant to diseases with reduced RNA editing and increased circRNA levels and provide insights into the human-specific regulation of circRNA formation.

The splicing-regulatory lncRNA NTRAS sustains vascular integrity

Vascular integrity is essential for organ homeostasis to prevent edema formation and infiltration of inflammatory cells. Long non‐coding RNAs (lncRNAs) are important regulators of gene expression and often expressed in a cell type‐specific manner. By screening for endothelial‐enriched lncRNAs, we identified the undescribed lncRNA NTRAS to control endothelial cell functions. Silencing of NTRAS induces endothelial cell dysfunction in vitro and increases vascular permeability and lethality in mice. Biochemical analysis revealed that NTRAS, through its CA‐dinucleotide repeat motif, sequesters the splicing regulator hnRNPL to control alternative splicing of tight junction protein 1 (TJP1; also named zona occludens 1, ZO‐1) pre‐mRNA. Deletion of the hnRNPL binding motif in mice (Ntras^∆CA/∆CA) significantly repressed TJP1 exon 20 usage, favoring expression of the TJP1α‐ isoform, which augments permeability of the endothelial monolayer. Ntras^∆CA/∆CA mice further showed reduced retinal vessel growth and increased vascular permeability and myocarditis. In summary, this study demonstrates that NTRAS is an essential gatekeeper of vascular integrity.

A review of brain stimulation and neuromodulation therapies as a treatment of depression as a behavioural and psychological symptom of vascular dementia

Introduction

Vascular dementia (VaD) accounts for approximately 15% of all cases of dementia. While there are many different definitions of vascular dementia, it is generally understood to refer to “disease with a cognitive impairment resulting from cerebrovascular disease and ischaemic or haemorrhagic brain injury”. Research suggests that 30% of patients with VaD also suffer from depression. The treatment of depression in VaD with pharmacological therapy is relatively well-established, with the first line drug being a selective serotonin reuptake inhibitor (SSRI). However, a relatively under-researched area is the use of brain stimulation and neuromodulation therapies for the treatment of depression in VaD.

Objectives

This review aims to provide a critical analysis on the efficacy and safety of brain stimulation therapies in treating depression in VaD to determine whether it is an appropriate treatment option.

Methods

The databases used were PubMed and WebofScience. The available literature was analysed which resulted in three papers which met the inclusion criteria and were critically appraised.

Results

In all three studies, depressive symptoms improved after ECT was administered, regardless of the specific tool used to measure the severity of depression. The side effects experienced were also only temporary and resolved independently which speaks to the safety of ECT as a treatment option.

Conclusions

The results of the study prove that ECT is a safe and effective option in treating depression in VaD. However, more research is needed for the medical community to fully understand the different treatment options and say with certainty which is the safest and most effective.

Disclosure

No significant relationships.

Abstract 384: Regulation Of The Smooth Muscle Cell Phenotypic Switch In Resolution Of Vascular Injury

Background: The modulation of vascular smooth muscle cells (VSMC) phenotypes is a highly important process in the formation of neointima and in resolution of inflammation after vascular injury. Underlying genetic mechanisms that control the phenotypic switch of VSMC in disease are not completely understood. On this basis, the phenotypic regulation of VSMC in restenosis development was examined in the mouse carotid artery injury model.

Methods and Results: Wire-induced injury, an established mouse-model to study restenosis, was applied to induce vascular injury in C57BL/6 mice. Time-resolved single-cell RNA-sequencing (scRNAseq) and massive-analysis-of-cDNA-ends (MACE)-RNAseq of neointima obtained by laser capture microdissection were performed to detect genetic changes in neointima development. Single-cell RNA-sequencing of C57BL/6 mice at different time points after wire-induced injury revealed an expanding, highly proliferative activated VSMC cluster, which exhibited low expression of SMC marker genes. Analysis for differentially regulated genes (DEG) and pseudotime clustering identified a unique marker gene signature, including high expression of TIMP Metallopeptidase Inhibitor 1 (Timp1), which was identified as main ordering gene of the modulation processes′ pseudo temporal states. MACEseq confirmed upregulation of Timp1 selectively in neointima forming VSMCs. Integration with atherosclerosis scRNAseq data indicated differences in gene signatures of activated VSMC populations. Transcription factor analysis of modulated VSMC identified BACH1, a factor involved in reactive oxidative stress response and proliferation of SMCs, as potential regulatory target for re-differentiation of VSMCs after vascular injury.

Conclusion: ScRNAseq identified a unique cell cluster responsible for neointima formation. Targeting the transcription factors driving the cluster (like BACH1) can be exploited to combat neointima development.

Perception of Employees Regarding the Quality Management System Implemented at a Tertiary Care Eye Hospital in North India: A Mixed-Methods Study

Background:

Quality management in healthcare is critical for hospitals and everyone in the loop —from physicians to support staff—needs to be aware of and involved in this process.

Objectives:

To assess the perception of employees about the quality management system (QMS) implemented at a tertiary care eye hospital in north India and to use it to identify scope for further improvement.

Methods:

This cross-sectional mixed-method study involved both questionnaire-based survey and an in-depth interview by a third party. The questionnaire had 12 questions to assess the changes in culture, infrastructure, environment, system, operation theatre and outpatient department. Employees shared their opinion about improvements brought by the QMS in eight years. Respondents were divided into five groups based on their job description: (i) doctors, (ii) technical staff (nursing/operation theatre/laboratory), (iii) optometrists/opticians/audiologists, (iv) patient care executives and (v) human resources/administration/others.

Results:

Of the 73 employees interviewed, 94.5% perceived an improved treatment and care process and 91.8% perceived improved treatment results. According to 83.6% of the employees, they were encouraged to report patient safety concerns and 71.2% saw improved incidence and adverse event management. The QMS has increased patient satisfaction according to 83%, while 91.8% felt it improved the profile of the hospital. The employees stated no negative effects of the QMS except a long waiting time of the patients and the duplication of paperwork.

Conclusion:

QMS has brought many positive changes across the hospital. Still, there is scope to reduce the patient waiting time and paperwork duplication.

Comparative analysis of common alignment tools for single-cell RNA sequencing

BACKGROUND

With the rise of single-cell RNA sequencing new bioinformatic tools have been developed to handle specific demands, such as quantifying unique molecular identifiers and correcting cell barcodes. Here, we benchmarked several datasets with the most common alignment tools for single-cell RNA sequencing data. We evaluated differences in the whitelisting, gene quantification, overall performance, and potential variations in clustering or detection of differentially expressed genes. We compared the tools Cell Ranger version 6, STARsolo, Kallisto, Alevin, and Alevin-fry on 3 published datasets for human and mouse, sequenced with different versions of the 10X sequencing protocol.

RESULTS

Striking differences were observed in the overall runtime of the mappers. Besides that, Kallisto and Alevin showed variances in the number of valid cells and detected genes per cell. Kallisto reported the highest number of cells; however, we observed an overrepresentation of cells with low gene content and unknown cell type. Conversely, Alevin rarely reported such low-content cells. Further variations were detected in the set of expressed genes. While STARsolo, Cell Ranger 6, Alevin-fry, and Alevin produced similar gene sets, Kallisto detected additional genes from the Vmn and Olfr gene family, which are likely mapping artefacts. We also observed differences in the mitochondrial content of the resulting cells when comparing a prefiltered annotation set to the full annotation set that includes pseudogenes and other biotypes.

CONCLUSION

Overall, this study provides a detailed comparison of common single-cell RNA sequencing mappers and shows their specific properties on 10X Genomics data.

Reduced RNA editing in the failing human heart mediates alternative circular RNA splicing

Background and purpose

Post-transcriptional RNA editing is an important mechanism in the development of human diseases. RNA editing can affect RNA stability and alternative splicing. The aim of our study was to characterize RNA editing and its impact on alternative RNA splicing in the healthy and failing human heart.

Methods and results

Human heart samples of heart failure (HF) patients (n=20) and controls (n=10) were analyzed using RNA sequencing with subsequent analysis of RNA editing. We identified adenosine-to-inosine (A-to-I) editing as the major form of RNA editing in human hearts, being reduced in HF patients. Consistently, we found the editing enzyme ADAR2 reduced in HF patients. A-to-I RNA editing predominantly occurred in intronic regions of protein-coding genes, specifically in repetitive, primate-specific Alu elements which can affect RNA splicing. Indeed, we found 173 circular RNAs (circRNAs) regulated by alternative mRNA splicing in the failing heart.

Loss of ADAR2 led to reduced RNA editing concomitant with an increase of circRNA, while overexpression reduced circRNA expression and enhanced RNA editing.

Conclusion

A-to-I editing is the major type of RNA editing in the human heart, being reduced in HF. We demonstrate a primate-specific alternative RNA splicing mechanism mediated by RNA editing in human hearts. The findings may be relevant to diseases with reduced RNA editing such as cancer, neurological and cardiac diseases.

Funding Acknowledgement

Type of funding sources: None.

The human cell atlas of the hypertrophic heart reveals impaired inter-cellular cross-talks

Introduction

The pathophysiology of cardiac hypertrophy is multifactorial and is accompanied by the dysregulation of various signaling pathways contributing to cardiac dysfunction and heart failure. While the hypertrophic response of cardiomyocytes (CM) has been extensively studied, the interplay of CMs with the non-parenchymal cells in the heart is less explored. Here, we apply high-resolution transcriptomic analysis on single cell level allowing the identification of cellular responses and communication in the hypertrophic human heart.

Results

We analyzed single nuclei RNA sequencing data of cardiac tissues from five patients with aortic stenosis and cardiac hypertrophy and 13 matched healthy subjects. Bioinformatic data analysis of 88,536 nuclei followed by clustering led to the identification of specific heterogenic cell type signatures. Analyzing cell type specific gene expression signatures, we found the expected up-regulation of the cardiac stress MYH7 (4.15-fold), CMYA5 (4.89-fold) and XIRP2 (6.13-fold) in cardiomyocytes (CM) (all p&lt;0.0001). Fibroblasts showed increased expression of genes associated with fibrosis and activation markers such as periostin (POSTN; 6.84-fold, p&lt;0.0001). In-silico analysis of intercellular communication pathways revealed a striking downregulation of ligand-receptor interactions between CMs and other cells in hypertrophic compared to healthy controls indicating that CMs are less responsive to signals from fibroblasts and endothelial cells (ECs) in the hypertrophied heart. Particularly, CM showed reduced expression of receptor tyrosine kinases of the Ephrin family and FGF-family members. Specifically, Ephrin-B1 was significantly downregulated in CMs of the hypertrophic hearts (0.01-fold, p&lt;0.0001). The down-regulation of Ephrin-B1 was additionally validated on protein level using histological sections of hypertrophic cardiomyopathy patients (n=6) versus healthy controls (n=5) (0.66-fold, p=0.02). In-vitro studies in neonatal cardiomyocytes further demonstrated that activation of the Ephrin-B1 receptor by the agonist Ephrin-B2 induced cardioprotective effects. Thus, Ephrin-B2 inhibited phenylephrine (PE) induced Nppb expression by 0.775-fold (vs. PE) and hypertrophic growth (0.774-fold reduction of cell size vs. PE). Similar findings were observed in PE-stimulated human cardiac organoids, which showed a 0.58-fold reduction of size in response to Ephrin-B2 treatments compared to PE alone.

Conclusion

Investigating the cross-talk in cardiac hypertrophy reveals novel disturbed communication signatures, with a striking reduction in the intercellular communication pathways of CMs. Reduced expression of receptors of the Ephrin family, particularly Ephrin-B1, in CM may prevent cardioprotective signaling by the agonist Ephrin-B2, which is highly expressed in ECs, leading to inhibition of cardioprotective cross-talk between ECs and CMs in the hypertrophic heart.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): Dr. Rolf M. Schwiete StiftungDie Deutsche ForschungsgemeinschaftGerman Center for Cardiovascular Research

Post-myocardial infarction heart failure dysregulates the bone vascular niche

The regulation of bone vasculature by chronic diseases, such as heart failure is unknown. Here, we describe the effects of myocardial infarction and post-infarction heart failure on the bone vascular cell composition. We demonstrate an age-independent loss of type H endothelium in heart failure after myocardial infarction in both mice and humans. Using single-cell RNA sequencing, we delineate the transcriptional heterogeneity of human bone marrow endothelium, showing increased expression of inflammatory genes, including IL1B and MYC, in ischemic heart failure. Endothelial-specific overexpression of MYC was sufficient to induce type H bone endothelial cells, whereas inhibition of NLRP3-dependent IL-1β production partially prevented the post-myocardial infarction loss of type H vasculature in mice. These results provide a rationale for using anti-inflammatory therapies to prevent or reverse the deterioration of bone vascular function in ischemic heart disease.

The hydrogen-peroxide producing NADPH oxidase 4 does not limit neointima development after vascular injury in mice

Objective

The NADPH oxidase Nox4 is an important source of H₂O₂. Nox4-derived H₂O₂ limits vascular inflammation and promotes smooth muscle differentiation. On this basis, the role of Nox4 for restenosis development was determined in the mouse carotid artery injury model.

Methods and results

Genetic deletion of Nox4 by a tamoxifen-activated Cre-Lox-system did not impact on neointima formation in the carotid artery wire injury model. To understand this unexpected finding, time-resolved single-cell RNA-sequencing (scRNAseq) from injured carotid arteries of control mice and massive-analysis-of-cDNA-ends (MACE)-RNAseq from the neointima harvested by laser capture microdissection of control and Nox4 knockout mice was performed. This revealed that resting smooth muscle cells (SMCs) and fibroblasts exhibit high Nox4 expression, but that the proliferating de-differentiated SMCs, which give rise to the neointima, have low Nox4 expression. In line with this, the first weeks after injury, gene expression was unchanged between the carotid artery neointimas of control and Nox4 knockout mice.

Conclusion

Upon vascular injury, Nox4 expression is transiently lost in the cells which comprise the neointima. NADPH oxidase 4 therefore does not interfere with restenosis development after wire-induced vascular injury.

Association of Clonal Hematopoiesis of Indeterminate Potential With Inflammatory Gene Expression in Patients With Severe Degenerative Aortic Valve Stenosis or Chronic Postischemic Heart Failure

Importance

Cytokine release syndrome is a complication of coronavirus disease 2019. Clinically, advanced age and cardiovascular comorbidities are the most important risk factors.

Objective

To determine whether clonal hematopoiesis of indeterminate potential (CHIP), an age-associated condition with excess cardiovascular risk defined as the presence of an expanded, mutated somatic blood cell clone in persons without other hematological abnormalities, may be associated with an inflammatory gene expression sensitizing monocytes to aggravated immune responses.

Design, Setting, and Participants

This hypothesis-generating diagnostic study examined a cohort of patients with severe degenerative aortic valve stenosis or chronic postinfarction heart failure, as well as age-matched healthy control participants. Single-cell RNA sequencing and analyses of circulating peripheral monocytes was done between 2017 and 2019 to assess the transcriptome of circulating monocytes.

Exposures

Severe degenerative aortic valve stenosis or chronic postinfarction heart failure.

Main Outcomes and Measures

CHIP-driver sequence variations in monocytes with a proinflammatory signature of genes involved in cytokine release syndrome.

Results

The study included 8 patients with severe degenerative aortic valve stenosis, 6 with chronic postinfarction heart failure, and 3 healthy control participants. Their mean age was 75.7 (range, 54-89) years, and 6 were women. Mean CHIP-driver gene variant allele frequency was 4.2% (range, 2.5%-6.9%) for DNMT3A and 14.3% (range, 2.6%-37.4%) for TET2. Participants with DNMT3A or TET2 CHIP-driver sequence variations displayed increased expression of interleukin 1β (no CHIP-driver sequence variations, 1.6217 normalized Unique Molecular Identifiers [nUMI]; DNMT3A, 5.3956 nUMI; P < .001; TET2, 10.8216 nUMI; P < .001), the interleukin 6 receptor (no CHIP-driver sequence variations, 0.5386 nUMI; DNMT3A, 0.9162 nUMI; P < .001;TET2, 0.5738 nUMI; P < .001), as well as the NLRP3 inflammasome complex (no CHIP-driver sequence variations, 0.4797 nUMI; DNMT3A, 0.9961 nUMI; P < .001; TET2, 1.2189 nUMI; P < .001), plus upregulation of CD163 (no CHIP-driver sequence variations, 0.5239 nUMI; DNMT3A, 1.4722 nUMI; P < .001; TET2, 1.0684 nUMI; P < .001), a cellular receptor capable of mediating infection, macrophage activation syndrome, and other genes involved in cytokine response syndrome. Gene ontology term analyses of regulated genes revealed that the most significantly upregulated genes encode for leukocyte-activation and interleukin-signaling pathways in monocytes of individuals with DNMT3A (myeloid leukocyte activation: log[Q value], -50.1986; log P value, -54.5177; regulation of cytokine production: log[Q value], -21.0264; log P value, -24.1993; signaling by interleukins: log[Q value], -18.0710: log P value, -21.1597) or TET2 CHIP-driver sequence variations (immune response: log[Q value], -36.3673; log P value, -40.6864; regulation of cytokine production: log[Q value], -13.1733; log P value, -16.3463; signaling by interleukins: log[Q value], -12.6547: log P value, -15.7977).

Conclusions and Relevance

Monocytes of individuals who carry CHIP-driver sequence variations and have cardiovascular disease appear to be primed for excessive inflammatory responses. Further studies are warranted to address potential adverse outcomes of coronavirus disease 2019 in patients with CHIP-driver sequence variations.

Impact of MRI/US fusion‐guided prostate biopsy on biopsy‐naïve patients: A single urologist’s experience

Objectives

To report our experience with imaging‐guided targeted prostate biopsy (IGTpBx) for patients undergoing initial prostate biopsy in a clinical setting.

Materials and methods

From July 2014 to February 2020, 305 men who had IGTpBx performed as their first prostate biopsy were enrolled. Two dedicated magnetic resonance imaging (MRI) radiologists segmented at least 1 region of interest (ROI) for each of these men using screening 1.5T MRI images. A single urologist employed the robotic‐assisted Artemis MRI/ultrasonography (US) fusion platform to obtain 2‐3 targeted samples from each ROI and additional random samples from the zones of the prostate outside the ROIs (a total of 12 zonal samples). Biopsy outcomes were categorized based on the Gleason score (GS) grade group (GG) as no cancer, favorable (GG < 3 or GS < 4 + 3), or clinically significant (GG ≥ 3 or GS ≥ 4 + 3) cancer.

Results

The overall cancer detection rate was 75%:31% clinically significant, 44% favorable, and 25% no cancer. These findings triggered active interventions in 176 (58%) patients. A prostate‐specific antigen (PSA) level of 0–4 ng/mL was detected in 39 (66%) of 59 patients (32 favorable, 7 significant), 4–10 ng/mL in 147 (77%) of 190 patients (85 favorable, 62 significant), and 10 ng/mL and over in 44 (80%) of 55 patients (17 favorable, 27 significant).

Conclusions

The tumor detection rate was 75% with IGTpBx in patients without a previous biopsy. In addition, about 42% of detected cancers were deemed clinically significant and led to active interventions. IGTpBx as a patient’s first prostate biopsy improves the detection of clinically significant prostate cancer when compared with historical data for random systematic prostate biopsy.

Single Nuclei Sequencing Reveals Novel Insights Into the Regulation of Cellular Signatures in Children With Dilated Cardiomyopathy

BACKGROUND

Dilated cardiomyopathy (DCM) is a leading cause of death in children with heart failure. The outcome of pediatric heart failure treatment is inconsistent, and large cohort studies are lacking. Progress may be achieved through personalized therapy that takes age- and disease-related pathophysiology, pathology, and molecular fingerprints into account. We present single nuclei RNA sequencing from pediatric patients with DCM as the next step in identifying cellular signatures.

METHODS

We performed single nuclei RNA sequencing with heart tissues from 6 children with DCM with an age of 0.5, 0.75, 5, 6, 12, and 13 years. Unsupervised clustering of 18 211 nuclei led to the identification of 14 distinct clusters with 6 major cell types.

RESULTS

The number of nuclei in fibroblast clusters increased with age in patients with DCM, a finding that was confirmed by histological analysis and was consistent with an age-related increase in cardiac fibrosis quantified by cardiac magnetic resonance imaging. Fibroblasts of patients with DCM >6 years of age showed a profoundly altered gene expression pattern with enrichment of genes encoding fibrillary collagens, modulation of proteoglycans, switch in thrombospondin isoforms, and signatures of fibroblast activation. In addition, a population of cardiomyocytes with a high proregenerative profile was identified in infant patients with DCM but was absent in children >6 years of age. This cluster showed high expression of cell cycle activators such as cyclin D family members, increased glycolytic metabolism and antioxidative genes, and alterations in ß-adrenergic signaling genes.

CONCLUSIONS

Novel insights into the cellular transcriptomes of hearts from pediatric patients with DCM provide remarkable age-dependent changes in the expression patterns of fibroblast and cardiomyocyte genes with less fibrotic but enriched proregenerative signatures in infants.

EVL regulates VEGF receptor-2 internalization and signaling in developmental angiogenesis

Endothelial tip cells are essential for VEGF‐induced angiogenesis, but underlying mechanisms are elusive. The Ena/VASP protein family, consisting of EVL, VASP, and Mena, plays a pivotal role in axon guidance. Given that axonal growth cones and endothelial tip cells share many common features, from the morphological to the molecular level, we investigated the role of Ena/VASP proteins in angiogenesis. EVL and VASP, but not Mena, are expressed in endothelial cells of the postnatal mouse retina. Global deletion of EVL (but not VASP) compromises the radial sprouting of the vascular plexus in mice. Similarly, endothelial‐specific EVL deletion compromises the radial sprouting of the vascular plexus and reduces the endothelial tip cell density and filopodia formation. Gene sets involved in blood vessel development and angiogenesis are down‐regulated in EVL‐deficient P5‐retinal endothelial cells. Consistently, EVL deletion impairs VEGF‐induced endothelial cell proliferation and sprouting, and reduces the internalization and phosphorylation of VEGF receptor 2 and its downstream signaling via the MAPK/ERK pathway. Together, we show that endothelial EVL regulates sprouting angiogenesis via VEGF receptor‐2 internalization and signaling.

Single nuclei sequencing reveals novel insights into cardiac cell signatures in human pediatric dilated cardiopathy

 

The mechanism underlying dilated cardiomyopathy (DCM) in children without a known genetic disorder are unclear. In contrast to adult DCM patients, there is an unmet need for therapeutic options that improve survival in pediatric DCM. Therefore, we performed single nuclei RNA sequencing (snRNA-seq) from heart tissue obtained from children undergoing heart transplantation due to severe heart failure.

We processed heart tissue from 6 children with DCM (EF: 18.67±2.11%) of an age of 0.5, 0.75, 5, 6, 12 and 13 years (y). After snRNA-seq, unsupervised clustering was performed identifying 8 major cell types, including cardiomyocytes (CM), fibroblasts (FB), endothelial cells, leukocytes, pericytes, smooth muscle cells, neuronal-like cells and an endothelial-fibroblast-like cluster. Relative numbers of FB clusters correlated with increasing age of the children which was clinically validated by measuring late enhancement (LE) with cardiac magnetic resonance imaging in 68 pediatric DCM patients. The mean age of patients with LE was 5.86±0.53y vs. 2.36±0.53y in patients without LE (p&lt;0.05). Further analysis of unique highly expressed genes (DEGs) between the 3 age groups identified a profound alteration of gene expression in FB clusters. FBs of explants of &lt;1y old patients showed high expression of anti-fibrotic, development and remodeling associated genes. In contrast, FBs of 12–13y old children highly expressed pro-fibrotic and FB activation associated genes as transforming growth factor beta binding protein (6.63 fold), cytochrome P450 1B1 (3.79 fold), and periostin (7.67 fold) (all p&lt;0.05). Moreover, we observed a switch in collagen expression patterns and in thrombospondin isoforms (from THBS1 to THBS4). Furthermore, our analysis revealed most profound transcriptional changes in CMs. We identified a cluster of CMs with a pro-regenerative profile in &lt;1y old patients, which could not be detected during adolescence. This CM cluster showed high expression of genes associated with proliferation (e.g. cyclin D2), glycolytic metabolism and anti-oxidant markers. Increased cyclin D2 was confirmed by immunostaining (1.43 fold higher in &lt;1y vs. 12–13y). Since all of these gene expression patterns might be affected by the underlying disease of the pediatric heart recipients, we explored their expression in FBs and CMs of postnatal vs. adult mice. Importantly, we could recapitulate the vast majority of the findings from humans in the mice experiments.

Together, these data demonstrate an age-dependent decrease in CM numbers concomitant with increased FBs in pediatric DCM. FBs of &lt;1y old pediatric patients revealed a distinct collagen expression profile and showed lower levels of pro-fibrotic genes. CMs of &lt;1y old donors where characterized with a regeneration enabling gene expression profile, which include pro-proliferative genes. The expression patterns of the CMs indicates, that regeneration might also occur in humans during the firs year of life.

Funding Acknowledgement

Type of funding source: Public grant(s) – EU funding. Main funding source(s): Dr. Rolf M. Schwiete Stiftung, DZHK

Long Noncoding RNA TYKRIL Plays a Role in Pulmonary Hypertension via the p53-mediated Regulation of PDGFRβ

Rationale: Long noncoding RNAs (lncRNAs) are emerging as important regulators of diverse biological functions. Their role in pulmonary arterial hypertension (PAH) remains to be explored.Objectives: To elucidate the role of TYKRIL (tyrosine kinase receptor-inducing lncRNA) as a regulator of p53/ PDGFRβ (platelet-derived growth factor receptor β) signaling pathway and to investigate its role in PAH.Methods: Pericytes and pulmonary arterial smooth muscle cells exposed to hypoxia and derived from patients with idiopathic PAH were analyzed with RNA sequencing. TYKRIL knockdown was performed in above-mentioned human primary cells and in precision-cut lung slices derived from patients with PAH.Measurements and Main Results: Using RNA sequencing data, TYKRIL was identified to be consistently upregulated in pericytes and pulmonary arterial smooth muscles cells exposed to hypoxia and derived from patients with idiopathic PAH. TYKRIL knockdown reversed the proproliferative (n = 3) and antiapoptotic (n = 3) phenotype induced under hypoxic and idiopathic PAH conditions. Owing to the poor species conservation of TYKRIL, ex vivo studies were performed in precision-cut lung slices from patients with PAH. Knockdown of TYKRIL in precision-cut lung slices decreased the vascular remodeling (n = 5). The number of proliferating cell nuclear antigen-positive cells in the vessels was decreased and the number of terminal deoxynucleotide transferase-mediated dUTP nick end label-positive cells in the vessels was increased in the LNA (locked nucleic acid)-treated group compared with control. Expression of PDGFRβ, a key player in PAH, was found to strongly correlate with TYKRIL expression in the patient samples (n = 12), and TYKRIL knockdown decreased PDGFRβ expression (n = 3). From the transcription factor-screening array, it was observed that TYKRIL knockdown increased the p53 activity, a known repressor of PDGFRβ. RNA immunoprecipitation using various p53 mutants demonstrated that TYKRIL binds to the N-terminal of p53 (an important region for p300 interaction with p53). The proximity ligation assay revealed that TYKRIL interferes with the p53-p300 interaction (n = 3) and regulates p53 nuclear translocation.Conclusions: TYKRIL plays an important role in PAH by regulating the p53/PDGFRβ axis.

Clonal Hematopoiesis-Driver DNMT3A Mutations Alter Immune Cells in Heart Failure

RATIONALE

Clonal hematopoiesis driven by mutations of DNMT3A (DNA methyltransferase 3a) is associated with increased incidence of cardiovascular disease and poor prognosis of patients with chronic heart failure (HF) and aortic stenosis. Although experimental studies suggest that DNMT3A clonal hematopoiesis-driver mutations may enhance inflammation, specific signatures of inflammatory cells in humans are missing.

OBJECTIVE

To define subsets of immune cells mediating inflammation in humans using single-cell RNA sequencing.

METHODS AND RESULTS

Transcriptomic profiles of peripheral blood mononuclear cells were analyzed in n=6 patients with HF harboring DNMT3A clonal hematopoiesis-driver mutations and n=4 patients with HF and no DNMT3A mutations by single-cell RNA sequencing. Monocytes of patients with HF carrying DNMT3A mutations demonstrated a significantly increased expression of inflammatory genes compared with monocytes derived from patients with HF without DNMT3A mutations. Among the specific upregulated genes were the prototypic inflammatory IL (interleukin) IL1B (interleukin 1B), IL6, IL8, the inflammasome NLRP3, and the macrophage inflammatory proteins CCL3 and CCL4 as well as resistin, which augments monocyte-endothelial adhesion. Silencing of DNMT3A in monocytes induced a paracrine proinflammatory activation and increased adhesion to endothelial cells. Furthermore, the classical monocyte subset of DNMT3A mutation carriers showed increased expression of T-cell stimulating immunoglobulin superfamily members CD300LB, CD83, SIGLEC12, as well as the CD2 ligand and cell adhesion molecule CD58, all of which may be involved in monocyte-T-cell interactions. DNMT3A mutation carriers were further characterized by increased expression of the T-cell alpha receptor constant chain and changes in T helper cell 1, T helper cell 2, T helper cell 17, CD8+ effector, CD4+ memory, and regulatory T-cell-specific signatures.

CONCLUSIONS

This study demonstrates that circulating monocytes and T cells of patients with HF harboring clonal hematopoiesis-driver mutations in DNMT3A exhibit a highly inflamed transcriptome, which may contribute to the aggravation of chronic HF.

Identification and functional characterization of circular RNAs in pericytes

Background

Circular RNAs (circRNAs) are generated by back-splicing. They are known to be robustly expressed in a variety of mammalian cell types and organism and have been reported to influence cell biology by acting e.g. as microRNA sponges or regulating host gene expression. Recently, our group reported functionally relevant circRNA expression in endothelial cells. Despite their important role in the cardiovascular system, the expression and function of circRNAs in pericytes is not well studied. Pericytes are perivascular mural cells, important for vessel maturation and endothelial barrier function. Their recruitment towards endothelial cells is mainly meditated by platelet-derived growth factor (PDGF) signaling. However, a more precise understanding of the regulation of pericyte differentiation and survival is necessary.

Objective

Here, we analyse circRNA expression in pericytes and demonstrate biological relevance of the hypoxia regulated circular RNA PLOD2 (cPLOD2).

Methods and results

Using RNA Sequencing in ribosomal depleted RNA we characterized the expression of circRNAs in human pericytes under normoxic and hypoxic (1% O2, 48h) conditions. We identified several circular RNAs being regulated upon hypoxia. The identified circular RNAs demonstrated resistance towards RNase-R digestion and lacking of poly-adenylation. Some of them were found to be localized and in the cytosol, whereas others also occur in the nucleus of the cells. Especially cPLOD2 raised our attention since it is significantly upregulated and robustly expressed upon hypoxia. Silencing cPLOD2 by siRNA resulted in significant de-differentiation of pericytes that went along with a loss of cell viability. Mechanistically, transcription factor screening assays revealed that silencing of cPLOD2 enhances the activity of the transcription factors ELK1/SRF, which have been documented to result in de-differentiation of smooth muscle cells.

Conclusion

Here we characterize the expression pattern of circRNAs in human primary pericytes. Among others, cPLOD2 significantly regulates pericyte function. Our results indicate hypoxia as a major regulator of circRNA expression in pericytes and show that circRNAs are capable of regulating pericyte function by modulating activity of transcription factors.

Funding Acknowledgement

Type of funding source: Foundation. Main funding source(s): Deutsche Forschungsgesellschaft (DFG) - SFB834; Deutsche Gesellschaft für Herz-Kreislaufforschung (DZHK)

Single cell sequencing reveals endothelial plasticity with transient mesenchymal activation after myocardial infarction

 

After myocardial infarct (MI), followed by ischemia and scar formation, interstitial cells play key roles in the adaptation to injury. Endothelial cells (ECs), for instance, can clonally expand, migrate into the infarct area and facilitate crucial functions promoting revascularization, reestablishment of oxygen supply and secretion of paracrine factors. Moreover, ECs can transiently undergo changes towards a mesenchymal phenotype (Endothelial-to-mesenchymal transition; EndMT). Whether this process contributes to long-term cardiac fibrosis or helps to facilitate post-ischemic vessel growth remains controversial. Here, we aim to delineate kinetics and characteristics of phenotypic changes in ECs with single cell RNA-sequencing (scRNA-seq).

We performed a time course (homeostasis or 0 day (d), 1d, 3d, 5d, 7d, 14d, 28d post-MI) in mice and isolated the non-cardiomyocyte fraction for scRNA-seq (n=35,312 cells). Pecam1/Cdh5 double positive ECs showed expression of apoptosis, hypoxia and inflammation markers at 3d. Bioinformatic cell cycle analysis predicted high association with proliferative capacities at 3d, indicative of EC turnover post-MI. Metabolism, recently linked to regulate EndMT, was altered. We found genes of the glycolysis and the TCA-cycle pathway upregulated at 1d to 3d, and a decrease of fatty acid signaling genes. At 3d, mesenchymal markers Fn1, Vim, S100a4, Serpine1 transiently increased compared to homeostasis (&gt;1.6-fold, p&lt;0.05) together with a reduction of EC genes such as Pecam1. Interestingly, mesenchymal transition was transient and returned to baseline levels at 28d after MI. Cell fate trajectory analysis confirmed these findings by identifying an EC state characterized by high proliferation and mesenchymal but low EC properties. At 3d to 7d the majority of the ECs were assigned to this state, based on their transcriptomic profile.

We additionally used Cdh5-CreERT2; R26-mT/mG mice followed by scRNA-seq to trace the fate of ECs. Bioinformatic analysis of GFP-positive ECs confirmed the gain in mesenchymal marker but revealed no full transition to the mesenchymal state at later timepoints. This suggests a transient mesenchymal activation of ECs rather than a complete lineage transition. We further induced EndMT with TGF-β2 in ECs in vitro and observed reversibility of the phenotype after withdrawal of the stimulus. After treatment, ECs upregulated various mesenchymal marker genes. Withdrawal of TGF-β2 at 3d or 7d, reverted expression to baseline levels. We further determined DNA methylation of EndMT gene loci to assess if TGF-β2 leads to a true fate change but did not observe changes after TGF-β2 stimulation and withdrawal. Taken together, our data suggests that ECs undergo a transient mesenchymal activation concomitant with a metabolic adaptation early after MI but do not acquire a long-term mesenchymal fate. This activation may facilitate EC migration and clonal expansion to regenerate the vascular network.

Funding Acknowledgement

Type of funding source: Foundation. Main funding source(s): German Center of Cardiovascular Research (DZHK), Deutsche Forschungsgemeinschaft (DFG) CRC1366 Project B4

DNMT3A clonal hematopoiesis-driver mutations are associated with profound changes in monocyte and T cell signatures in humans with heart failure

Background

Clonal hematopoiesis (CH) driven by mutations of DNA methyltransferase 3a (DNMT3A) is associated with increased incidence of cardiovascular disease and poor prognosis of patients with chronic heart failure (HF) and aortic stenosis. Although experimental studies suggest that DNMT3A CH-driver mutations may enhance inflammation, specific signatures of inflammatory cells in humans are missing. Single-cell RNA-sequencing provides a novel opportunity to define subsets of immune cells mediating inflammation in humans.

Methods

Transcriptomic profiles of peripheral blood mononuclear cells were analysed in N=6 HF patients harboring DNMT3A CH-drived mutations and with HF and N=5 patients with HF and DNMT3A mutations by single-cell RNA-sequencing.

Results

Monocytes of HF patients carrying DNMT3A mutations demonstrated a significantly increased expression of inflammatory genes compared to monocytes derived from patients with HF without DNMT3A mutations. Among the specific up-regulated genes were the prototypic inflammatory interleukins (IL) IL1B, IL6, and IL8, the macrophage inflammatory proteins CCL3 and CCL4 as well as restin, which augments monocyte-endothelial adhesion. The classical monocyte subset of DNMT3A mutation carriers showed increased expression of immunoglobulin superfamily members CD80, CD300LB, and SIGLEC12, as well as the cell adhesion molecule CD58, all of which may be involved in monocyte-T cell interactions. DNMT3A mutation carriers were further characterized by increased expression of T cell receptor chains and Th1, Th17, CD8+ and Treg specific signatures.

Conclusions

This study demonstrates that circulating monocytes and T cells of HF patients harboring CHIP-driver mutations in DNMT3A exhibit a highly inflamed transcriptome, which may contribute to the aggravation of chronic heart failure.

Funding Acknowledgement

Type of funding source: Public Institution(s). Main funding source(s): The German Research Foundation (SFB834, Project B1), and the German Center for Cardiovascular Research (DZHK).

Cost Needed to Treat (CNT) and Number Needed to Treat (NNT) analysis of drugs for treatment of heart failure in India

Background

Only little attention has been paid to treatment strategies of chronic disease conditions that require long term treatment and repeated hospitalizations

Purpose

Our aim was to review cost-effectiveness of guideline directed medical therapy of heart failure in India and identify drugs that can be made available free of cost or at subsidized rates to the patient population.

Methods

Data extracted from ten landmark trials in heart failure was used to compute Number Needed to Treat (NNT) and Cost Needed to Treat (CNT) of drugs used in heart failure, to prevent cardiovascular mortality and heart failure re-hospitalization using HDS Plotter- Incremental Cost Effectiveness Calculator. Since various brands (i.e. trade names) with wide cost range are available in Indian market, the average retail price in Indian Rupees for year 2019 was considered and converted to US dollars and used for the analysis.NNT and CNT of each drug was computed and the cost-effectiveness was analyzed. WHO recommendation of three times per capita GDP was used as the cost effectiveness threshold.

Results

Medications that were labeled as class I for the treatment of heart failure, were included in our analysis. Ivabradine, Valsartan and Angiotensin Receptor Neprilysin inhibitor (ARNi) did not meet the cost effectiveness criteria for preventing cardio-vascular mortality. For prevention of heart failure re-hospitalization, all drugs except ARNi, met the cost effectiveness threshold.

Conclusion

Any future research would need to consider compliance factor along with Willingness to Pay (WTP) to understand the real acceptance of these drugs on the ground in India.

Log prices (in US$) of various HF drugs

Funding Acknowledgement

Type of funding source: None

IDH1/2 mutations in acute myeloid leukemia patients and risk of coronary artery disease and cardiac dysfunction-a retrospective propensity score analysis

Clonal hematopoiesis of indeterminate potential (CHIP) is linked to leukemia gene mutations and associates with an increased risk for coronary artery disease and poor prognosis in ischemic cardiomyopathy. Two recurrently mutated genes in CHIP and adult acute myeloid leukemia (AML) encode for isocitrate dehydrogenases 1 and 2 (IDH1 and IDH2). Global expression of mutant IDH2 in transgenic mice-induced dilated cardiomyopathy and muscular dystrophy. In this retrospective observational study, we investigated whether mutant IDH1/2 predisposes to cardiovascular disease in AML patients. Among 363 AML patients, IDH1 and IDH2 mutations were detected in 26 (7.2%) and 39 patients (10.7%), respectively. Mutant IDH1 patients exhibited a significantly higher prevalence of coronary artery disease (26.1% vs. 6.4%, p = 0.002). Applying inverse probability-weighting analysis, patients with IDH1/2 mutations had a higher risk for a declining cardiac function during AML treatment compared to IDH1/2 wild type patients [left ventricular ejection fraction pretreatment compared to 10 months after diagnosis: 59.2% to 41.9% (p < 0.001) vs 58.5% to 55.4% (p = 0.27), respectively]. Mechanistically, RNA sequencing and immunostaining in hiPS-derived cardiomyocytes indicated that the oncometabolite R-2HG exacerbated doxorubicin mediated cardiotoxicity. Evaluation of IDH1/2 mutation status may therefore help identifying AML patients at risk for cardiovascular complications during cytotoxic treatment.

Descriptive epidemiology of coronavirus disease 2019 in Nigeria, 27 February-6 June 2020

The objective of this study was to describe the epidemiology of COVID-19 in Nigeria with a view of generating evidence to enhance planning and response strategies. A national surveillance dataset between 27 February and 6 June 2020 was retrospectively analysed, with confirmatory testing for COVID-19 done by real-time polymerase chain reaction (RT-PCR). The primary outcomes were cumulative incidence (CI) and case fatality (CF). A total of 40 926 persons (67% of total 60 839) had complete records of RT-PCR test across 35 states and the Federal Capital Territory, 12 289 (30.0%) of whom were confirmed COVID-19 cases. Of those confirmed cases, 3467 (28.2%) had complete records of clinical outcome (alive or dead), 342 (9.9%) of which died. The overall CI and CF were 5.6 per 100 000 population and 2.8%, respectively. The highest proportion of COVID-19 cases and deaths were recorded in persons aged 31-40 years (25.5%) and 61-70 years (26.6%), respectively; and males accounted for a higher proportion of confirmed cases (65.8%) and deaths (79.0%). Sixty-six per cent of confirmed COVID-19 cases were asymptomatic at diagnosis. In conclusion, this paper has provided an insight into the early epidemiology of COVID-19 in Nigeria, which could be useful for contextualising public health planning.

Efficiency and Target Derepression of Anti-miR-92a: Results of a First in Human Study

MicroRNA (miRNA) inhibition is a promising therapeutic strategy in several disease indications. MRG-110 is a locked nucleic acid-based antisense oligonucleotide that targets miR-92a-3p and experimentally was shown to have documented therapeutic effects on cardiovascular disease and wound healing. To gain first insights into the activity of anti-miR-92a in humans, we investigated miR-92a-3p expression in several blood compartments and assessed the effect of MRG-110 on target derepression. Healthy adults were randomly assigned (5:2) to receive a single intravenous dose of MRG-110 or placebo in one of seven sequential ascending intravenous dose cohorts ranging from 0.01 to 1.5 mg/kg body weight. MiR-92a-3p whole blood levels were time and dose dependently decreased with half-maximal inhibition of 0.27 and 0.31 mg/kg at 24 and 72 h after dosing, respectively. In the high-dose groups, >95% inhibition was detected at 24-72 h postinfusion and significant inhibition was observed for 2 weeks. Similar inhibitory effects were detected in isolated CD31⁺ cells, and miR-92a-3p expression was also inhibited in extracellular vesicles in the high-dose group. Target derepression was measured in whole blood and showed that ITGA5 and CD93 were increased at a dose of 1.5 mg/kg. Single-cell RNA sequencing of peripheral blood cells revealed a cell type-specific derepression of miR-92a targets. Together this study demonstrates that systemic infusion of anti-miR-92a efficiently inhibits miR-92a in the peripheral blood compartment and derepresses miR-92a targets in humans.

Single-cell RNA-sequencing reveals profound changes in circulating immune cells in patients with heart failure

AIMS

Identification of signatures of immune cells at single-cell level may provide novel insights into changes of immune-related disorders. Therefore, we used single-cell RNA-sequencing to determine the impact of heart failure on circulating immune cells.

METHODS AND RESULTS

We demonstrate a significant change in monocyte to T-cell ratio in patients with heart failure, compared to healthy subjects, which were validated by flow cytometry analysis. Subclustering of monocytes and stratification of the clusters according to relative CD14 and FCGR3A (CD16) expression allowed annotation of classical, intermediate, and non-classical monocytes. Heart failure had a specific impact on the gene expression patterns in these subpopulations. Metabolically active genes such as FABP5 were highly enriched in classical monocytes of heart failure patients, whereas β-catenin expression was significantly higher in intermediate monocytes. The selective regulation of signatures in the monocyte subpopulations was validated by classical and multifactor dimensionality reduction flow cytometry analyses.

CONCLUSION

Together this study shows that circulating cells derived from patients with heart failure have altered phenotypes. These data provide a rich source for identification of signatures of immune cells in heart failure compared to healthy subjects. The observed increase in FABP5 and signatures of Wnt signalling may contribute to enhanced monocyte activation.

Investigation of RNA Editing Sites within Bound Regions of RNA-Binding Proteins

Studies in epitranscriptomics indicate that RNA is modified by a variety of enzymes. Among these RNA modifications, adenosine to inosine (A-to-I) RNA editing occurs frequently in the mammalian transcriptome. These RNA editing sites can be detected directly from RNA sequencing (RNA-seq) data by examining nucleotide changes from adenosine (A) to guanine (G), which substitutes for inosine (I). However, a careful investigation of such nucleotide changes must be conducted to distinguish sequencing errors and genomic mutations from the genuine editing sites. Building upon our recent introduction of an easy-to-use bioinformatics tool, RNA Editor, to detect RNA editing events from RNA-seq data, we examined the extent by which RNA editing events affect the binding of RNA-binding proteins (RBP). Through employing bioinformatic techniques, we uncovered that RNA editing sites occur frequently in RBP-bound regions. Moreover, the presence of RNA editing sites are more frequent when RNA editing islands were examined, which are regions in which RNA editing sites are present in clusters. When the binding of one RBP, human antigen R [HuR; encoded by ELAV-like protein 1 (ELAV1)], was quantified experimentally, its binding was reduced upon silencing of the RNA editing enzyme adenosine deaminases acting on RNA (ADAR) compared to the control-suggesting that the presence of RNA editing islands influence HuR binding to its target regions. These data indicate RNA editing as an important mediator of RBP-RNA interactions-a mechanism which likely constitutes an additional mode of post-transcription gene regulation in biological systems.

Transcriptional heterogeneity of fibroblasts is a hallmark of the aging heart

Aging is a major risk factor for cardiovascular disease. Although the impact of aging has been extensively studied, little is known regarding the aging processes in cells of the heart. Here we analyzed the transcriptomes of hearts of 12-week-old and 18-month-old mice by single-nucleus RNA-sequencing. Among all cell types, aged fibroblasts showed most significant differential gene expression, increased RNA dynamics, and network entropy. Aged fibroblasts exhibited significantly changed expression patterns of inflammatory, extracellular matrix organization angiogenesis, and osteogenic genes. Functional analyses indicated deterioration of paracrine signatures between fibroblasts and endothelial cells in old hearts. Aged heart-derived fibroblasts had impaired endothelial cell angiogenesis and autophagy and augmented proinflammatory response. In particular, expression of Serpine1 and Serpine2 were significantly increased and secreted by old fibroblasts to exert antiangiogenic effects on endothelial cells, an effect that could be significantly prevented by using neutralizing antibodies. Moreover, we found an enlarged subpopulation of aged fibroblasts expressing osteoblast genes in the epicardial layer associated with increased calcification. Taken together this study provides system-wide insights and identifies molecular changes of aging cardiac fibroblasts, which may contribute to declined heart function.

1437Single cell RNA sequencing reveals profound changes in monocytic cell clusters in patients with mutations associated with clonal hematopoiesis

Background

Monocytes and macrophages have distinct roles in cardiovascular health where they may contribute to beneficial processes like wound healing and cardiac conductance or to pathological processes like inflammation, remodeling and fibrosis. Despite their importance, the specific signatures of circulating monocytes are missing. Single cell RNA sequencing (scRNA-seq) provides a novel opportunity to define subsets of monocytes mediating inflammation in humans.

Purpose

To detect and study the inflammatory burden driven by subsets of monocytes in healthy individuals and subjects with chronic ischemic heart failure (CHF) using scRNA-seq.

Methods and results

Circulating CD31+ cells of CHF patients (n=11) along with aged matched (n=3) and young healthy controls (n=5) were sorted and scRNA-seq then performed. Unsupervised clustering of present sequencing data revealed these cells to be comprised of 19 subpopulations (primarily monocytes). Many subpopulations of cells were comprised chiefly or solely by CHF subjects. Dysregulated genes in CHF subjects, relative to healthy controls included interleukin-1b, thrombospondin-1, S100A8 and matrix metalloprotease-1, which were confirmed by FACS and qRT-PCR in a validation cohort. Given the expanded, divergent and highly inflammatory transcriptional populations of monocytes in patients with CHF, we assessed whether occurrence of somatic mutations associated with clonal hematopoiesis of indeterminate potential (CHIP), recently shown to be increased in subjects with atherosclerosis and heart failure, might occur in these subjects. Indeed, we identified patients who revealed mutations in the DNA methyltransferase DNMT3A and other CHIP-driver genes. DNMT3A mutations were associated with changes in known DNMT3A target genes such as the pro-inflammatory genes CXCL1, CXCL2 and IL6 in circulating monocytic cells. Moreover, cell fate trajectory analysis showed shared fates of cells driven by pseudotime-dependent variables from subjects harboring DNMT3A mutations. Regulated genes in this fate were associated with cell survival, migration and inflammation, appropriate for this disease phenotype.

Conclusions

This is the first study to show scRNA-seq profiles of monocytes in patients with CHF. Healthy subjects displayed remarkable homogeneity in their transcriptional profiles. CHF subjects show changes in inflammatory gene expression. CHF subjects with clonal hematopoiesis share signature gene expression profiles driving similar cell fates. Subjects with CHF of ischemic origin harboring DNMT3A mutations have a worse prognosis than non-CHIP carrier CHF controls. Identification of early alterations in immune cell subsets recognized by single cell sequencing and genetic testing of CHIP mutations may detect subjects with a high risk and allow for a precision treatment of the immune disorders.

Acknowledgement/Funding

SFB834

Analysis of Cell Type-Specific Effects of MicroRNA-92a Provides Novel Insights Into Target Regulation and Mechanism of Action

BACKGROUND

MicroRNAs (miRs) regulate nearly all biological pathways. Because the dysregulation of miRs can lead to disease progression, they are being explored as novel therapeutic targets. However, the cell type-specific effects of miRs in the heart are poorly understood. Thus, we assessed miR target regulation using miR-92a-3p as an example. Inhibition of miR-92a is known to improve endothelial cell function and recovery after acute myocardial infarction.

METHODS

miR-92a-3p was inhibited by locked nucleic acid (LNA)-based antimiR (LNA-92a) in mice after myocardial infarction. Expression of regulated genes was evaluated 3 days after myocardial infarction by RNA sequencing of isolated endothelial cells, cardiomyocytes, fibroblasts, and CD45⁺ hematopoietic cells.

RESULTS

LNA-92a depleted miR-92a-3p expression in all cell types and derepressed predicted miR-92a-3p targets in a cell type-specific manner. RNAseq showed endothelial cell-specific regulation of autophagy-related genes. Imaging confirmed increased endothelial cell autophagy in LNA-92a treated relative to control animals. In vitro inhibition of miR-92a-3p augmented EC autophagy, derepressed autophagy-related gene 4a, and increased luciferase activity in autophagy-related gene 4a 3'UTR containing reporters, whereas miR-92a-3p overexpression had the opposite effect. In cardiomyocytes, LNA-92a derepressed metabolism-related genes, notably, the high-density lipoprotein transporter Abca8b. LNA-92a further increased fatty acid uptake and mitochondrial function in cardiomyocytes in vitro.

CONCLUSIONS

Our data show that miRs have cell type-specific effects in vivo. Analysis of miR targets in cell subsets disclosed a novel function of miR-92a-3p in endothelial cell autophagy and cardiomyocyte metabolism. Because autophagy is upregulated during ischemia to supply nutrients and cardiomyocyte metabolic-switching improves available substrate utilization, these prosurvival mechanisms may diminish tissue damage.

A novel long non-coding RNA Myolinc regulates myogenesis through TDP-43 and Filip1

Myogenesis is a complex process required for skeletal muscle formation during embryonic development and for regeneration and growth of myofibers in adults. Accumulating evidence suggests that long non-coding RNAs (lncRNAs) play key roles in regulating cell fate decision and function in various tissues. However, the role of lncRNAs in the regulation of myogenesis remains poorly understood. In this study, we identified a novel muscle-enriched lncRNA called 'Myolinc (AK142388)', which we functionally characterized in the C2C12 myoblast cell line. Myolinc is predominately localized in the nucleus, and its levels increase upon induction of the differentiation. Knockdown of Myolinc impairs the expression of myogenic regulatory factors and formation of multi-nucleated myotubes in cultured myoblasts. Myolinc also regulates the expression of Filip1 in a cis-manner. Similar to Myolinc, knockdown of Filip1 inhibits myogenic differentiation. Furthermore, Myolinc binds to TAR DNA-binding protein 43 (TDP-43), a DNA/RNA-binding protein that regulates the expression of muscle genes (e.g. Acta1 and MyoD). Knockdown of TDP-43 inhibits myogenic differentiation. We also show that Myolinc-TDP-43 interaction is essential for the binding of TDP-43 to the promoter regions of muscle marker genes. Finally, we show that silencing of Myolinc inhibits skeletal muscle regeneration in adult mice. Altogether, our study identifies a novel lncRNA that controls key regulatory networks of myogenesis.