Toward functional screening of cardioactive and cardiotoxic drugs with zebrafish in vivo using pseudodynamic three-dimensional imaging

Longitudinal and quantitative assessment platform for concurrent analysis of anti-tumor efficacy and cardiotoxicity of nano-formulated medication in vivo

Increasing nanomedicinal approaches have been developed to effectively inhibit tumor growth; however, critical questions such as whether a nanomedicinal approach can mitigate latent side effects are barely addressed. To this end, we established a zebrafish xenograft tumor model, combining pseudodynamic three-dimensional cardiac imaging and image analysis to enable simultaneous and quantitative determination of the change of tumor volume and cardiac function of zebrafish upon specific nanoformulation treatment. Doxorubicin (DOX), a well-known chemotherapeutic agent with cardiotoxicity, and a recently developed DOX-loaded nanocomposite were employed as two model drugs to demonstrate the effectiveness to utilize the proposed evaluation platform for rapid validation. The nanoformulation significantly mitigated DOX-associated cardiotoxicity, while retaining the efficacy of DOX in inhibiting tumor growth compared to administration of carrier-free DOX at the same dose. We anticipate that this platform possesses the potential as an efficient assessment system for nanoformulated cancer therapeutics with suspected toxicity and side effects to vital organs such as the heart.

Streamlining drug discovery assays for cardiovascular disease using zebrafish

Introduction: In the last decade, our armamentarium of cardiovascular drug therapy has expanded significantly. Using innovative functional genomics strategies such as genome editing by CRISPR/Cas9 as well as high-throughput assays to identify bioactive small chemical compounds has significantly facilitated elaboration of the underlying pathomechanism in various cardiovascular diseases. However, despite scientific progress approvals for cardiovascular drugs has stagnated significantly compared to other fields of drug discovery and therapy during the past years.Areas covered: In this review, the authors discuss the aspects and pitfalls during the early phase of cardiovascular drug discovery and describe the advantages of zebrafish as an in vivo organism to model human cardiovascular diseases (CVD) as well as an in vivo platform for high-throughput chemical compound screening. They also highlight the emerging, promising techniques of automated read-out systems during high-throughput screening (HTS) for the evaluation of important cardiac functional parameters in zebrafish with the potential to streamline CVD drug discovery.Expert opinion: The successful identification of novel drugs to treat CVD is a major challenge in modern biomedical and clinical research. In this context, the definition of the etiologic fundamentals of human cardiovascular diseases is the prerequisite for an efficient and straightforward drug discovery.

Zebrafish VCAP1X2 regulates cardiac contractility and proliferation of cardiomyocytes and epicardial cells

Sarcomeric signaling complexes are important to sustain proper sarcomere structure and function, however, the mechanisms underlying these processes are not fully elucidated. In a gene trap experiment, we found that vascular cell adhesion protein 1 isoform X2 (VCAP1X2) mutant embryos displayed a dilated cardiomyopathy phenotype, including reduced cardiac contractility, enlarged ventricular chamber and thinned ventricular compact layer. Cardiomyocyte and epicardial cell proliferation was decreased in the mutant heart ventricle, as was the expression of pAKT and pERK. Contractile dysfunction in the mutant was caused by sarcomeric disorganization, including sparse myofilament, blurred Z-disc, and decreased gene expression for sarcomere modulators (smyd1b, mypn and fhl2a), sarcomeric proteins (myh6, myh7, vmhcl and tnnt2a) and calcium regulators (ryr2b and slc8a1a). Treatment of PI3K activator restored Z-disc alignment while injection of smyd1b mRNA restored Z-disc alignment, contractile function and cardiomyocyte proliferation in ventricles of VCAP1X2 mutant embryos. Furthermore, injection of VCAP1X2 variant mRNA rescued all phenotypes, so long as two cytosolic tyrosines were left intact. Our results reveal two tyrosine residues located in the VCAP1X2 cytoplasmic domain are essential to regulate cardiac contractility and the proliferation of ventricular cardiomyocytes and epicardial cells through modulating pAKT and pERK expression levels.

Breakthroughs in modern cancer therapy and elusive cardiotoxicity: Critical research-practice gaps, challenges, and insights

To date, five cancer treatment modalities have been defined. The three traditional modalities of cancer treatment are surgery, radiotherapy, and conventional chemotherapy, and the two modern modalities include molecularly targeted therapy (the fourth modality) and immunotherapy (the fifth modality). The cardiotoxicity associated with conventional chemotherapy and radiotherapy is well known. Similar adverse cardiac events are resurging with the fourth modality. Aside from the conventional and newer targeted agents, even the most newly developed, immune‐based therapeutic modalities of anticancer treatment (the fifth modality), e.g., immune checkpoint inhibitors and chimeric antigen receptor (CAR) T‐cell therapy, have unfortunately led to potentially lethal cardiotoxicity in patients. Cardiac complications represent unresolved and potentially life‐threatening conditions in cancer survivors, while effective clinical management remains quite challenging. As a consequence, morbidity and mortality related to cardiac complications now threaten to offset some favorable benefits of modern cancer treatments in cancer‐related survival, regardless of the oncologic prognosis. This review focuses on identifying critical research‐practice gaps, addressing real‐world challenges and pinpointing real‐time insights in general terms under the context of clinical cardiotoxicity induced by the fourth and fifth modalities of cancer treatment. The information ranges from basic science to clinical management in the field of cardio‐oncology and crosses the interface between oncology and onco‐pharmacology. The complexity of the ongoing clinical problem is addressed at different levels. A better understanding of these research‐practice gaps may advance research initiatives on the development of mechanism‐based diagnoses and treatments for the effective clinical management of cardiotoxicity.

Zebrafish models for functional and toxicological screening of nanoscale drug delivery systems: promoting preclinical applications

Preclinical screening with animal models is an important initial step in clinical translation of new drug delivery systems. However, establishing efficacy, biodistribution, and biotoxicity of complex, multicomponent systems in small animal models can be expensive and time-consuming. Zebrafish models represent an alternative for preclinical studies for nanoscale drug delivery systems. These models allow easy optical imaging, large sample size, and organ-specific studies, and hence an increasing number of preclinical studies are employing zebrafish models. In this review, we introduce various models and discuss recent studies of nanoscale drug delivery systems in zebrafish models. Also in the end, we proposed a guideline for the preclinical trials to accelerate the progress in this field.

Zebrafish model of photochemical thrombosis for translational research and thrombolytic screening in vivo

Acute thromboembolic diseases remain the major global cause of death or disability. Although an array of thrombolytic and antithrombotic drugs has been approved to treat or prevent thromboembolic diseases, many more drugs that target specific clotting mechanisms are under development. Here a novel zebrafish model of photochemical thrombosis is reported and its prospective application for the screening and preclinical testing of thrombolytic agents in vivo is demonstrated. Through photochemical excitation, a thrombus was induced to form at a selected section of the dorsal aorta of larval zebrafish, which had been injected with photosensitizers. Such photochemical thrombosis can be consistently controlled to occlude partially or completely the targeted blood vessel. Detailed mechanistic tests indicate that the zebrafish model of photochemical thrombosis exhibits essential features of classical coagulation and a thrombolytic pathway. For demonstration, tissue plasminogen activator (tPA), a clinically feasible thrombolytic agent, was shown to effectively dissolve photochemically induced blood clots. In light of the numerous unique advantages of zebrafish as a model organism, our approach is expected to benefit not only the development of novel thrombolytic and antithrombotic strategies but also the fundamental or translational research targeting hereditary thrombotic or coagulation disorders.

Advances in the Study of Heart Development and Disease Using Zebrafish

Animal models of cardiovascular disease are key players in the translational medicine pipeline used to define the conserved genetic and molecular basis of disease. Congenital heart diseases (CHDs) are the most common type of human birth defect and feature structural abnormalities that arise during cardiac development and maturation. The zebrafish, Danio rerio, is a valuable vertebrate model organism, offering advantages over traditional mammalian models. These advantages include the rapid, stereotyped and external development of transparent embryos produced in large numbers from inexpensively housed adults, vast capacity for genetic manipulation, and amenability to high-throughput screening. With the help of modern genetics and a sequenced genome, zebrafish have led to insights in cardiovascular diseases ranging from CHDs to arrhythmia and cardiomyopathy. Here, we discuss the utility of zebrafish as a model system and summarize zebrafish cardiac morphogenesis with emphasis on parallels to human heart diseases. Additionally, we discuss the specific tools and experimental platforms utilized in the zebrafish model including forward screens, functional characterization of candidate genes, and high throughput applications.

Biothiol-triggered, self-disassembled silica nanobeads for intracellular drug delivery

Silica-based nanomaterials have demonstrated great potential in biomedical applications due to their chemical inertness. However, the degradability and endosomal trapping issues remain as rate-limiting barriers during their innovation. In this study, we provide a simple yet novel sol-gel approach to construct the redox-responsive silica nanobeads (ReSiNs), which could be rapidly disassembled upon redox gradient for intracellular drug delivery. The disulfide-linked scaffold of the nanobead was synthesized by employing the dithiobis-(succinimidyl propionate) to bridge (3-aminopropyl)-trimethoxysilane. Such silica matrix could be efficiently disrupted in response to intracellular glutathione, resulting in drug release and collapse of entire nanocarrier. Moreover, the ReSiNs exhibited insignificant cytotoxicity before and after the degradation. These results indicated the potential of using ReSiNs as a novel silica-based, biothiol-degradable nanoplatform for future drug delivery.

Animal and in silico models for the study of sarcomeric cardiomyopathies

Over the past decade, our understanding of cardiomyopathies has improved dramatically, due to improvements in screening and detection of gene defects in the human genome as well as a variety of novel animal models (mouse, zebrafish, and drosophila) and in silico computational models. These novel experimental tools have created a platform that is highly complementary to the naturally occurring cardiomyopathies in cats and dogs that had been available for some time. A fully integrative approach, which incorporates all these modalities, is likely required for significant steps forward in understanding the molecular underpinnings and pathogenesis of cardiomyopathies. Finally, novel technologies, including CRISPR/Cas9, which have already been proved to work in zebrafish, are currently being employed to engineer sarcomeric cardiomyopathy in larger animals, including pigs and non-human primates. In the mouse, the increased speed with which these techniques can be employed to engineer precise 'knock-in' models that previously took years to make via multiple rounds of homologous recombination-based gene targeting promises multiple and precise models of human cardiac disease for future study. Such novel genetically engineered animal models recapitulating human sarcomeric protein defects will help bridging the gap to translate therapeutic targets from small animal and in silico models to the human patient with sarcomeric cardiomyopathy.

Optically gated beating-heart imaging

The constant motion of the beating heart presents an obstacle to clear optical imaging, especially 3D imaging, in small animals where direct optical imaging would otherwise be possible. Gating techniques exploit the periodic motion of the heart to computationally "freeze" this movement and overcome motion artifacts. Optically gated imaging represents a recent development of this, where image analysis is used to synchronize acquisition with the heartbeat in a completely non-invasive manner. This article will explain the concept of optical gating, discuss a range of different implementation strategies and their strengths and weaknesses. Finally we will illustrate the usefulness of the technique by discussing applications where optical gating has facilitated novel biological findings by allowing 3D in vivo imaging of cardiac myocytes in their natural environment of the beating heart.