Eva Van Rooij

MicroRNA mimicry blocks pulmonary fibrosis

Over the last decade, great enthusiasm has evolved for microRNA (miRNA) therapeutics. Part of the excitement stems from the fact that a miRNA often regulates numerous related mRNAs. As such, modulation of a single miRNA allows for parallel regulation of multiple genes involved in a particular disease. While many studies have shown therapeutic efficacy using miRNA inhibitors, efforts to restore or increase the function of a miRNA have been lagging behind. The miR‐29 family has gained a lot of attention for its clear function in tissue fibrosis. This fibroblast‐enriched miRNA family is downregulated in fibrotic diseases which induces a coordinate increase of many extracellular matrix genes. Here, we show that intravenous injection of synthetic RNA duplexes can increase miR‐29 levels in vivo for several days. Moreover, therapeutic delivery of these miR‐29 mimics during bleomycin‐induced pulmonary fibrosis restores endogenous miR‐29 function whereby decreasing collagen expression and blocking and reversing pulmonary fibrosis. Our data support the feasibility of using miRNA mimics to therapeutically increase miRNAs and indicate miR‐29 to be a potent therapeutic miRNA for treating pulmonary fibrosis.

Exosomal MicroRNA Clusters Are Important for the Therapeutic Effect of Cardiac Progenitor Cells

Although current evidence indicates that cardiac progenitor cells (CPCs) may improve cardiac repair after ischemic injury, the exact mechanism for this cardioprotective effect to date remains undefined. In this issue of Circulation Research , Gray et al1 report on the use of systems biology to link the change in exosomal microRNAs (miRNA) to the beneficial effects of CPCs during ischemic injury in mice. Expression analysis showed that exosomes from hypoxic CPCs contain a higher level of a subset of miRNAs than exosomes coming from normoxic CPCs. To connect the relevance of the change in miRNA levels to the biological effect of exosomes, the authors performed a principle component analysis of the miRNA expression profiles in exosomes, which identified 4 unique miRNA clusters, which after further mathematical modeling seemed to correlate to a biological effect related to the therapeutic benefit. Instead of studying the biological function of a single miRNA, computational modeling can be applied to integrate multiple variants to gain more insight into the overall relationship and interaction between the different datasets. Gray et al1 show that especially for miRNA biology, where a miRNA can target up to hundreds of genes in a parallel, systems biology could turn out to be a suitable approach for predicting a biological outcome or therapeutic benefit.nnArticle, see p 255nnCells communicate with each other via direct cell–cell contact and secretion of soluble factors. Soluble factors that are gaining an increasing amount of attention are extracellular membrane vesicles. The ability of vesicles to transport different molecules, such as proteins, peptides, mRNA, and microRNAs, from one cell to the other and their general body-wide distribution make them attractive candidates for horizontal information transfer between cells.2 Although the release of vesicles to influence other cells seems to be straightforward, multiple mechanisms, size distributions, …

Tomo-Seq Identifies SOX9 as a Key Regulator of Cardiac Fibrosis During Ischemic Injury

Background: Cardiac ischemic injury induces a pathological remodeling response, which can ultimately lead to heart failure. Detailed mechanistic insights into molecular signaling pathways relevant for different aspects of cardiac remodeling will support the identification of novel therapeutic targets. Methods: Although genome-wide transcriptome analysis on diseased tissues has greatly advanced our understanding of the regulatory networks that drive pathological changes in the heart, this approach has been disadvantaged by the fact that the signals are derived from tissue homogenates. Here we used tomo-seq to obtain a genome-wide gene expression signature with high spatial resolution spanning from the infarcted area to the remote to identify new regulators of cardiac remodeling. Cardiac tissue samples from patients suffering from ischemic heart disease were used to validate our findings. Results: Tracing transcriptional differences with a high spatial resolution across the infarcted heart enabled us to identify gene clusters that share a comparable expression profile. The spatial distribution patterns indicated a separation of expressional changes for genes involved in specific aspects of cardiac remodeling, such as fibrosis, cardiomyocyte hypertrophy, and calcium handling (Col1a2, Nppa, and Serca2). Subsequent correlation analysis allowed for the identification of novel factors that share a comparable transcriptional regulation pattern across the infarcted tissue. The strong correlation between the expression levels of these known marker genes and the expression of the coregulated genes could be confirmed in human ischemic cardiac tissue samples. Follow-up analysis identified SOX9 as common transcriptional regulator of a large portion of the fibrosis-related genes that become activated under conditions of ischemic injury. Lineage-tracing experiments indicated that the majority of COL1-positive fibroblasts stem from a pool of SOX9-expressing cells, and in vivo loss of Sox9 blunted the cardiac fibrotic response on ischemic injury. The colocalization between SOX9 and COL1 could also be confirmed in patients suffering from ischemic heart disease. Conclusions: Based on the exact local expression cues, tomo-seq can serve to reveal novel genes and key transcription factors involved in specific aspects of cardiac remodeling. Using tomo-seq, we were able to unveil the unknown relevance of SOX9 as a key regulator of cardiac fibrosis, pointing to SOX9 as a potential therapeutic target for cardiac fibrosis.

The Efficacy of Cardiac Anti-miR-208a Therapy Is Stress Dependent

MicroRNAs (miRNAs) are important regulators of biology and disease. Recent animal efficacy studies validate the therapeutic benefit of miRNA modulation and underscore the therapeutic value of miRNA-targeting oligonucleotides. However, whether disease conditions (stress) influence the pharmacological effects of an anti-miR is currently unknown. To study the effect of disease on target regulation after anti-miR treatment, we injected animals with anti-miR-208a, a synthetic oligonucleotide that inhibits the cardiomyocyte-specific miR-208a. Our data indicate that the presence of stress increases the number of regulated miR-208a targets, and that higher stress levels correlate with stronger target derepression. Additionally, the type of stress also influences which targets are regulated upon miR-208a inhibition. Studies in a large animal model indicate a similar stress-dependent anti-miR effect. Subsequent in vitro studies suggest that the influence of stress on anti-miR efficacy depends at least in part on increased cellular anti-miR uptake. These data indicate that the pharmacological effect of anti-miRs is stronger under disease conditions, and that both the type and severity of disease determine the therapeutic outcome. These facts will be important for assessing the therapeutic dose and predicting the therapeutic outcome when applying anti-miRs in a clinical setting.

Meeting highlights from the 2013 European Society of Cardiology Heart Failure Association Winter Meeting on Translational Heart Failure Research

Meeting highlights from the 2013 European Society of Cardiology Heart Failure Association Winter Meeting on Translational Heart Failure Research

Controlled Release of RNAi Molecules by Tunable Supramolecular Hydrogel Carriers

Local, sustained release and presentation of RNAi therapeutics can be achieved with hydrogel delivery systems. Here we show the development of a supramolecular hydrogel into a local RNAi delivery system. By careful material design, two simple but effective strategies are introduced to obtain controlled release of two classes of RNAi therapeutics, that is, microRNA and antimiR. It was shown that the release of microRNA could be regulated using cholesterol-modification for interaction with the supramolecular hydrogel. Non-modified antimiR release could be controlled via supramolecular introduction of positively charged additive molecules into the supramolecular hydrogel. In this way, either the cholesterol-modification on the drug or the charge introduction into the hydrogel provides handles for controlled RNAi therapy.