Development and characterization of anti-fibrotic natural compound similars with improved effectivity.

Cardiac fibroblasts constitute the major cell type of the murine and human heart. Once activated, they contribute to an excessive deposition of extracellular matrix (ECM) leading to cardiac fibrosis and subsequently organ dysfunction. With the exception of the pulmonary drugs, nintedanib and pirfenidone, drugs specifically targeting anti-fibrotic pathways are scarce. We recently performed large library screenings of natural occurring compounds and identified first lead structures with anti-fibrotic properties in vitro and in vivo. In line, we now aimed to improve efficacy of these anti-fibrotic lead structures by combining in vitro validation studies and in silico prediction. Next to this combined approach, we performed large OMICs-multi-panel-based mechanistic studies. Applying human cardiac fibroblasts (HCF), we analysed 26 similars of the initially identified anti-fibrotic lead molecules bufalin and lycorine and determined anti-proliferative activity and potential toxicity in an array of in vitro and ex vivo studies. Of note, even at lower concentrations, certain similars were more effective at inhibiting HCF proliferation than nintedanib and pirfenidone. Additionally, selected similars showed low cytotoxicity on human iPS-derived cardiomyocytes and anti-fibrotic gene regulation in human ex vivo living myocardial slices. Further, array and RNA sequencing studies of coding and non-coding RNAs in treated HCFs revealed strong anti-fibrotic properties, especially with the lycorine similar lyco-s (also known as homoharringtonine), that led to a nearly complete shutdown of ECM production at concentrations 100-fold lower than the previously identified anti-fibrotic compound lycorine without inducing cellular toxicity. We thus identified a new natural compound similar with strong anti-fibrotic properties in human cardiac fibroblasts and human living heart tissue potentially opening new anti-fibrotic treatment strategies.

Combined high-throughput library screening and next generation RNA sequencing uncover microRNAs controlling human cardiac fibroblast biology.

BACKGROUND: Myocardial fibrosis is a hallmark of the failing heart, contributing to the most common causes of deaths worldwide. Several microRNAs (miRNAs, miRs) controlling cardiac fibrosis were identified in recent years; however, a more global approach to identify miRNAs involved in fibrosis is missing. METHODS AND RESULTS: Functional miRNA mimic library screens were applied in human cardiac fibroblasts (HCFs) to identify annotated miRNAs inducing proliferation. In parallel, miRNA deep sequencing was performed after subjecting HCFs to proliferating and resting stimuli, additionally enabling discovery of novel miRNAs. In-depth in vitro analysis confirmed the pro-fibrotic nature of selected, highly conserved miRNAs miR-20a-5p and miR-132-3p. To determine downstream cellular pathways and their role in the fibrotic response, targets of the annotated miRNA candidates were modulated by synthetic siRNA. We here provide evidence that repression of autophagy and detoxification of reactive oxygen species by miR-20a-5p and miR-132-3p explain some of their pro-fibrotic nature on a mechanistic level. CONCLUSION: We here identified both miR-20a-5p and miR-132-3p as crucial regulators of fibrotic pathways in an in vitro model of human cardiac fibroblast biology.

Cardiac endurance training alters plasma profiles of circular RNA MBOAT2.

Marathon running is an extreme physical activity, which determines cardiopulmonary adaption of athletes. Circular RNAs (circRNAs) as potential biomarkers in the blood stream have so far not been tested after such strenuous activities. In silico approaches were performed to identify the potential candidate circRNA MBOAT2. Next, we demonstrated high stability and conservation of circRNA MBOAT2 as well as its abundancy in human plasma. In addition to Sanger sequencing of the circRNA specific head-to-tail junction, or back-splice site, we established a synthetic plasmid standard which allowed exact copy number calculations of circRNA MBOAT2. We then analyzed plasmatic circRNA MBOAT2 and observed a significantly lower level 24 h after the marathon. Such alterations were correlated to physical exercise parameters confirming the role of circRNA MBOAT2 as a promising noncoding RNA biomarker detecting cardiopulmonary adaption.NEW & NOTEWORTHY In brief, we herein report a timeline of circulating circular RNA (circRNA) MBOAT2 in a cohort of marathon runners. Time-course analysis of plasmatic circRNA MBOAT2 demonstrated a significantly lowered level 24 h after the marathon. Abundancy of circRNA was correlated to physical exercise parameters highlighting the role of circRNA MBOAT2 as a valuable noncoding RNA biomarker detecting and following up cardiopulmonary adaption.

Integrative Bioinformatic Analyses of Global Transcriptome Data Decipher Novel Molecular Insights into Cardiac Anti-Fibrotic Therapies.

Integrative bioinformatics is an emerging field in the big data era, offering a steadily increasing number of algorithms and analysis tools. However, for researchers in experimental life sciences it is often difficult to follow and properly apply the bioinformatical methods in order to unravel the complexity and systemic effects of omics data. Here, we present an integrative bioinformatics pipeline to decipher crucial biological insights from global transcriptome profiling data to validate innovative therapeutics. It is available as a web application for an interactive and simplified analysis without the need for programming skills or deep bioinformatics background. The approach was applied to an ex vivo cardiac model treated with natural anti-fibrotic compounds and we obtained new mechanistic insights into their anti-fibrotic action and molecular interplay with miRNAs in cardiac fibrosis. Several gene pathways associated with proliferation, extracellular matrix processes and wound healing were altered, and we could identify micro (mi) RNA-21-5p and miRNA-223-3p as key molecular components related to the anti-fibrotic treatment. Importantly, our pipeline is not restricted to a specific cell type or disease and can be broadly applied to better understand the unprecedented level of complexity in big data research.

Modelling IRF8 Deficient Human Hematopoiesis and Dendritic Cell Development with Engineered iPS Cells.

Human induced pluripotent stem (iPS) cells can differentiate into cells of all three germ layers, including hematopoietic stem cells and their progeny. Interferon regulatory factor 8 (IRF8) is a transcription factor, which acts in hematopoiesis as lineage determining factor for myeloid cells, including dendritic cells (DC). Autosomal recessive or dominant IRF8 mutations occurring in patients cause severe monocytic and DC immunodeficiency. To study IRF8 in human hematopoiesis we generated human IRF8-/- iPS cells and IRF8-/- embryonic stem (ES) cells using RNA guided CRISPR/Cas9n genome editing. Upon induction of hematopoietic differentiation, we demonstrate that IRF8 is dispensable for iPS cell and ES cell differentiation into hemogenic endothelium and for endothelial-to-hematopoietic transition, and thus development of hematopoietic progenitors. We differentiated iPS cell and ES cell derived progenitors into CD141+ cross-presenting cDC1 and CD1c+ classical cDC2 and CD303+ plasmacytoid DC (pDC). We found that IRF8 deficiency compromised cDC1 and pDC development, while cDC2 development was largely unaffected. Additionally, in an unrestricted differentiation regimen, IRF8-/- iPS cells and ES cells exhibited a clear bias toward granulocytes at the expense of monocytes. IRF8-/- DC showed reduced MHC class II expression and were impaired in cytokine responses, migration, and antigen presentation. Taken together, we engineered a human IRF8 knockout model that allows studying molecular mechanisms of human immunodeficiencies in vitro, including the pathophysiology of IRF8 deficient DC. Stem Cells 2017;35:898-908.

Epigenetic program and transcription factor circuitry of dendritic cell development.

Dendritic cells (DC) are professional antigen presenting cells that develop from hematopoietic stem cells through successive steps of lineage commitment and differentiation. Multipotent progenitors (MPP) are committed to DC restricted common DC progenitors (CDP), which differentiate into specific DC subsets, classical DC (cDC) and plasmacytoid DC (pDC). To determine epigenetic states and regulatory circuitries during DC differentiation, we measured consecutive changes of genome-wide gene expression, histone modification and transcription factor occupancy during the sequel MPP-CDP-cDC/pDC. Specific histone marks in CDP reveal a DC-primed epigenetic signature, which is maintained and reinforced during DC differentiation. Epigenetic marks and transcription factor PU.1 occupancy increasingly coincide upon DC differentiation. By integrating PU.1 occupancy and gene expression we devised a transcription factor regulatory circuitry for DC commitment and subset specification. The circuitry provides the transcription factor hierarchy that drives the sequel MPP-CDP-cDC/pDC, including Irf4, Irf8, Tcf4, Spib and Stat factors. The circuitry also includes feedback loops inferred for individual or multiple factors, which stabilize distinct stages of DC development and DC subsets. In summary, here we describe the basic regulatory circuitry of transcription factors that drives DC development.

Dendritic cell development requires histone deacetylase activity.

DCs develop from multipotent progenitors (MPPs), which commit into DC-restricted common dendritic cell progenitors (CDPs). CDPs further differentiate into classical DCs (cDCs) and plasmacytoid DCs (pDCs). Here, we studied the impact of histone acetylation on DC development in C57BL/6 mice by interfering with histone acetylation and deacetylation, employing histone deacetylase (HDAC) inhibitors. We observed that commitment of MPPs into CDPs was attenuated by HDAC inhibition and that pDC development was specifically blocked. Gene expression profiling revealed that HDAC inhibition prevents establishment of a DC-specific gene expression repertoire. Importantly, protein levels of the core DC transcription factor PU.1 were reduced in HDAC inhibitor-treated cells and consequently PU.1 recruitment at PU.1 target genes Fms-like tyrosine kinase 3 (Flt3), interferon regulatory factor 8 (IRF8), and PU.1 itself was impaired. Thus, our results demonstrate that attenuation of PU.1 expression by HDAC inhibition causes reduced expression of key DC regulators, which results in attenuation of DC development. We propose that chromatin modifiers, such as HDACs, are required for establishing a DC gene network, where Flt3/STAT3 signaling drives PU.1 and IRF8 expression and DC development. Taken together, our study identifies HDACs as critical regulators of DC lineage commitment and development.

Remodelling of adult cardiac tissue subjected to physiological and pathological mechanical load in vitro.

AIMS: Cardiac remodelling is the process by which the heart adapts to its environment. Mechanical load is a major driver of remodelling. Cardiac tissue culture has been frequently employed for in vitro studies of load-induced remodelling; however, current in vitro protocols (e.g. cyclic stretch, isometric load, and auxotonic load) are oversimplified and do not accurately capture the dynamic sequence of mechanical conformational changes experienced by the heart in vivo. This limits translational scope and relevance of findings. METHODS AND RESULTS: We developed a novel methodology to study chronic load in vitro. We first developed a bioreactor that can recreate the electromechanical events of in vivo pressure-volume loops as in vitro force-length loops. We then used the bioreactor to culture rat living myocardial slices (LMS) for 3 days. The bioreactor operated based on a 3-Element Windkessel circulatory model enabling tissue mechanical loading based on physiologically relevant parameters of afterload and preload. LMS were continuously stretched/relaxed during culture simulating conditions of physiological load (normal preload and afterload), pressure-overload (normal preload and high afterload), or volume-overload (high preload & normal afterload). At the end of culture, functional, structural, and molecular assays were performed to determine load-induced remodelling. Both pressure- and volume-overloaded LMS showed significantly decreased contractility that was more pronounced in the latter compared with physiological load (P < 0.0001). Overloaded groups also showed cardiomyocyte hypertrophy; RNAseq identified shared and unique genes expressed in each overload group. The PI3K-Akt pathway was dysregulated in volume-overload while inflammatory pathways were mostly associated with remodelling in pressure-overloaded LMS. CONCLUSION: We have developed a proof-of-concept platform and methodology to recreate remodelling under pathophysiological load in vitro. We show that LMS cultured in our bioreactor remodel as a function of the type of mechanical load applied to them.

Therapeutic modulation of RNA-binding protein Rbm38 facilitates re-endothelialization after arterial injury.

AIMS: Delayed re-endothelialization after balloon angioplasty in patients with coronary or peripheral artery disease impairs vascular healing and leads to neointimal proliferation. In the present study, we examined the effect of RNA-binding motif protein 38 (Rbm38) during re-endothelialization in a murine model of experimental vascular injury. METHODS AND RESULTS: Left common carotid arteries of C57BL/6 mice were electrically denudated and endothelial regeneration was evaluated. Profiling of RNA-binding proteins revealed dysregulated expression of Rbm38 in the denudated and regenerated areas. We next tested the importance of Rbm38 in human umbilical vein endothelial cells (HUVECS) and analysed its effects on cellular proliferation, migration and apoptosis. Rbm38 silencing in vitro demonstrated important beneficial functional effects on migratory capacity and proliferation of endothelial cells. In vivo, local silencing of Rbm38 also improved re-endothelialization of denuded carotid arteries. Luciferase reporter assay identified miR-98 and let-7f to regulate Rbm38 and the positive proliferative properties of Rbm38 silencing in vitro and in vivo were mimicked by therapeutic overexpression of these miRNAs. CONCLUSION: The present data identified Rbm38 as an important factor of the regulation of various endothelial cell functions. Local inhibition of Rbm38 as well as overexpression of the upstream regulators miR-98 and let-7f improved endothelial regeneration in vivo and thus may be a novel therapeutic entry point to avoid endothelial damage after balloon angioplasty.

Identification of miR-143 as a Major Contributor for Human Stenotic Aortic Valve Disease.

Calcification of aortic valves leads to aortic stenosis mainly in elderly individuals, but the underlying molecular mechanisms are still not understood. Here, we studied microRNA (miR, miRNA) expression and function in healthy and stenotic human aortic valves. We identified miR-21, miR-24, and miR-143 to be highly upregulated in stenotic aortic valves. Using luciferase reporter systems, we found direct binding of miR-143 to the 3'UTR region of the matrix gla protein (MGP), which in turn is a key factor to sustain homeostasis in aortic valves. In subsequent experiments, we demonstrated a therapeutic potential of miRNA regulation during calcification in cardiac valvular interstitial cells. Collectively, our data provide evidence that deregulated miR expression contributes to the development of stenotic valve disease and thus form novel therapeutic opportunities of this severe cardiovascular disease.

Cell fusion enhances mesendodermal differentiation of human induced pluripotent stem cells.

Human induced pluripotent stem cells (iPS cells) resemble embryonic stem cells and can differentiate into cell derivatives of all three germ layers. However, frequently the differentiation efficiency of iPS cells into some lineages is rather poor. Here, we found that fusion of iPS cells with human hematopoietic stem cells (HSCs) enhances iPS cell differentiation. Such iPS hybrids showed a prominent differentiation bias toward hematopoietic lineages but also toward other mesendodermal lineages. Additionally, during differentiation of iPS hybrids, expression of early mesendodermal markers-Brachyury (T), MIX1 Homeobox-Like Protein 1 (MIXL1), and Goosecoid (GSC)-appeared with faster kinetics than in parental iPS cells. Following iPS hybrid differentiation there was a prominent induction of NODAL and inhibition of NODAL signaling blunted mesendodermal differentiation. This indicates that NODAL signaling is critically involved in mesendodermal bias of iPS hybrid differentiation. In summary, we demonstrate that iPS cell fusion with HSCs prominently enhances iPS cell differentiation.