Transgenic fluorescent zebrafish lines that have revolutionized biomedical research

Insights into Craniofacial Development and Anomalies: Exploring Fgf Signaling in Zebrafish Models

PURPOSE OF REVIEW

To illustrate the value of using zebrafish to understand the role of the Fgf signaling pathway during craniofacial skeletal development under normal and pathological conditions.

RECENT FINDINGS

Recent data obtained from studies on zebrafish have demonstrated the genetic redundancy of Fgf signaling pathway and have identified new molecular partners of this signaling during the early stages of craniofacial skeletal development. Studies on zebrafish models demonstrate the involvement of the Fgf signaling pathway at every stage of craniofacial development. They particularly emphasize the central role of Fgf signaling pathway during the early stages of the development, which significantly impacts the formation of the various structures making up the craniofacial skeleton. This partly explains the craniofacial abnormalities observed in disorders associated with FGF signaling. Future research efforts should focus on investigating zebrafish Fgf signaling during more advanced stages, notably by establishing zebrafish models expressing mutations responsible for diseases such as craniosynostoses.

Live Imaging of Cutaneous Wound Healing after Rotary Tool Injury in Zebrafish

Cutaneous wounds are common afflictions that follow a stereotypical healing process involving hemostasis, inflammation, proliferation, and remodeling phases. In the elderly and those suffering from vascular or metabolic diseases, poor healing after cutaneous injuries can lead to open chronic wounds susceptible to infection. The discovery of new therapeutic strategies to improve this defective wound healing requires a better understanding of the cellular behaviors and molecular mechanisms that drive the different phases of wound healing and how these are altered with age or disease. The zebrafish provides an ideal model for visualization and experimental manipulation of the cellular and molecular events during wound healing in the context of an intact, living vertebrate. To facilitate studies of cutaneous wound healing in zebrafish, we have developed an inexpensive, simple, and effective method for generating reproducible cutaneous injuries in adult zebrafish using a rotary tool. We demonstrate that our injury system can be used in combination with high-resolution live imaging to monitor skin re-epithelialization, immune cell recruitment and activation, and vessel regrowth in the same animal over time. This injury system provides a valuable experimental platform to study key cellular and molecular events during wound healing in vivo with unprecedented resolution.

High species homology potentiates quantitative inflammation profiling in zebrafish using immunofluorescence

Due to substantial homology between the human and zebrafish genome and a high level of conservation of the innate immune system across species, zebrafish larvae have become an invaluable research tool for studying inflammation and modelling inflammatory disease. However, further microscopy techniques need to be developed for better profiling of inflammation and in particular, integrated cytokine responses to different stimuli - approaches are currently largely limited to assessment of changes in cytokine gene transcription and in vivo visualisation using transgenics, which is limited in terms of the number of cytokines that may be assessed at once. In this study, after confirming substantial homology of human vs zebrafish cytokine amino acid sequences, immunofluorescence staining using antibodies directed at human cytokines was performed. Inflammatory cytokine signalling responses to experimental tailfin transection was assessed over 24 h (1 hpi (hours post injury), 2 hpi, 4 hpi, 24 hpi) in zebrafish larvae, with experimental end point at 120 h post fertilization (hpf). When immunofluorescence results were compared to responses observed in rodent and human literature, it is clear that the cytokines follow a similar response, albeit with a condensed total time course. Notably, tumor necrosis factor-α and monocyte chemoattractant protein-1 increased and remained elevated over the 24-h period. In contrast, interleukin-1β and interleukin-6 peaked at 4 hpi and 2 hpi respectively but had both returned to baseline levels by 24 hpi. Macrophage migration inhibitory factor was lowest at 1 hpi, potentially encouraging macrophage movement into the site of injury, followed by a sharp increase. This protocol provides valuable insight into inflammation over a time course and more so, provides an affordable and accessible method to comprehensively assess inflammation in zebrafish disease models.

Isolation of Tissue Macrophages in Adult Zebrafish

Tissue macrophages are essential components of the immune system that also play key roles in vertebrate development and homeostasis, including in zebrafish, which has gained popularity over the years as a translational model for human disease. Commonly, zebrafish macrophages are identified based on expression of fluorescent transgenic reporters, allowing for real-time imaging in living animals. Several of these lines have also proven instrumental to isolate pure populations of macrophages in the developing embryo and larvae using fluorescence-activated cell sorting (FACS). However, the identification of tissue macrophages in adult fish is not as clear, and robust protocols are needed that would take into account changes in reporter specificity as well as the heterogeneity of mononuclear phagocytes as fish reach adulthood. In this chapter, we describe the methodology for analyzing macrophages in various tissues in the adult zebrafish by flow cytometry. Coupled with FACS, these protocols further allow for the prospective isolation of enriched populations of tissue-specific mononuclear phagocytes that can be used in downstream transcriptomic and/or epigenomic analyses. Overall, we aim at providing a guide for the zebrafish community based on our expertise investigating the adult mononuclear phagocyte system.

Uveal melanoma modeling in mice and zebrafish

Despite extensive research and refined therapeutic options, the survival for metastasized uveal melanoma (UM) patients has not improved significantly. UM, a malignant tumor originating from melanocytes in the uveal tract, can be asymptomatic and small tumors may be detected only during routine ophthalmic exams; making early detection and treatment difficult. UM is the result of a number of characteristic somatic alterations which are associated with prognosis. Although UM morphology and biology have been extensively studied, there are significant gaps in our understanding of the early stages of UM tumor evolution and effective treatment to prevent metastatic disease remain elusive. A better understanding of the mechanisms that enable UM cells to thrive and successfully metastasize is crucial to improve treatment efficacy and survival rates. For more than forty years, animal models have been used to investigate the biology of UM. This has led to a number of essential mechanisms and pathways involved in UM aetiology. These models have also been used to evaluate the effectiveness of various drugs and treatment protocols. Here, we provide an overview of the molecular mechanisms and pharmacological studies using mouse and zebrafish UM models. Finally, we highlight promising therapeutics and discuss future considerations using UM models such as optimal inoculation sites, use of BAP1mut-cell lines and the rise of zebrafish models.

Neurotoxicity of the Cu(OH)2 Nanopesticide through Perturbing Multiple Neurotransmitter Pathways in Developing Zebrafish

The copper hydroxide [Cu(OH)2] nanopesticide is an emerging agricultural chemical that can negatively impact aquatic organisms. This study evaluated the behavioral changes of zebrafish larvae exposed to the Cu(OH)2 nanopesticide and assessed its potential to induce neurotoxicity. Metabolomic and transcriptomic profiling was also conducted to uncover the molecular mechanisms related to potential neurotoxicity. The Cu(OH)2 nanopesticide at 100 μg/L induced zebrafish hypoactivity, dark avoidance, and response to the light stimulus, suggestive of neurotoxic effects. Altered neurotransmitter-related pathways (serotoninergic, dopaminergic, glutamatergic, GABAergic) and reduction of serotonin (5-HT), dopamine (DA), glutamate (GLU), γ-aminobutyric acid (GABA), and several of their precursors and metabolites were noted following metabolomic and transcriptomic analyses. Differentially expressed genes (DEGs) were associated with the synthesis, transport, receptor binding, and metabolism of 5-HT, DA, GLU, and GABA. Transcripts (or protein levels) related to neurotransmitter receptors for 5-HT, DA, GLU, and GABA and enzymes for the synthesis of GLU and GABA were downregulated. Effects on both the glutamatergic and GABAergic pathways in zebrafish were specific to the nanopesticide and differed from those in fish exposed to copper ions. Taken together, the Cu(OH)2 nanopesticide induced developmental neurotoxicity in zebrafish by inhibiting several neurotransmitter-related pathways. This study presented a model for Cu(OH)2 nanopesticide-induced neurotoxicity in developing zebrafish that can inform ecological risk assessments.

Evidence for Adverse Effects on Liver Development and Regeneration in Zebrafish by Decabromodiphenyl Ethane

Decabromodiphenyl ethane (DBDPE), a ubiquitous emerging pollutant, could be enriched in the liver of organisms, but its effects and mechanisms on liver development and regeneration remain largely unknown. In the present study, we first investigated the adverse effects on liver development and found decreased area and intensity of fluorescence in transgenic zebrafish larvae exposed to DBDPE; further results in wild-type zebrafish larvae revealed a possible mechanism involving disturbed MAPK/Fox O signaling pathways and cell cycle arrest as indicated by decreased transcription of growth arrest and DNA-damage-inducible beta a (gadd45ba). Subsequently, an obstructed recovery process of liver tissue after partial hepatectomy was characterized by the changing profiles of ventral lobe-to-intestine ratio in transgenic female adults upon DBDPE exposure; further results confirmed the adverse effects on liver regeneration by the alterations of the hepatic somatic index and proliferating cell nuclear antigen expression in wild-type female adults and also pointed out a potential role of a disturbed signaling pathway involving cell cycles and glycerolipid metabolism. Our results not only provided novel evidence for the hepatotoxicity and underlying mechanism of DBDPE but also were indicative of subsequent ecological and health risk assessment.

Red Fluorescent Protein Variant with a Dual-Peak Emission of Fluorescence

The marine environment is a rich reservoir of diverse biological entities, many of which possess unique properties that are of immense value to biotechnological applications. One such example is the red fluorescent protein derived from the coral Discosoma sp. This protein, encoded by the DsRed gene, has been the subject of extensive research due to its potential applications in various fields. In the study, a variant of the red fluorescent protein was generated through random mutagenesis using the DsRed2 gene as a template. The process employed error-prone PCR (epPCR) to introduce random mutations, leading to the isolation of twelve gene variants. Among these, one variant stood out due to its unique spectral properties, exhibiting dual fluorescence emission at both 480 nm (green) and 550 nm (red). This novel variant was expressed in both Escherichia coli and zebrafish (Danio rerio) muscle, confirming the dual fluorescence emission in both model systems. One of the immediate applications of this novel protein variant is in ornamental aquaculture. The dual fluorescence can serve as a unique marker or trait, enhancing the aesthetic appeal of aquatic species in ornamental settings.

Dopaminergic and serotoninergic neurotoxicity of lanthanide phosphate (TbPO4) in developing zebrafish

Rare earth elements (REEs) are exploited for global use in manufacturing. Such activities result in their release into the environment and the transformation into more stable phosphate deposition. The objective of this study was to evaluate molecular and behavioral changes of zebrafish exposed to the synthesized terbium phosphate (TbPO4) at concentrations of 10, 20, and 50 mg/L and to determine its potential for neurotoxicity. Metabolomics related to neurotransmitters, and assessment of transcripts and proteins were conducted to uncover the molecular mechanisms underlying TbPO4 with emphasis on neurotransmitter systems. Exposure to 20 mg/L TbPO4 induced larval hyperactivity and perturbed the cholinergic system in zebrafish. Based on metabolomics related to neurotransmitters, dopamine (DA), serotonin (5-HT), and many of their precursors and metabolites were decreased in abundance by TbPO4. In addition, the expression levels of transcripts related to the synthesis, transport, receptor binding, and metabolism of DA and 5-HT were analyzed at the mRNA and protein levels. Transcript and protein levels for tyrosine hydroxylase (TH), the rate-limiting enzyme for DA synthesis, were down-regulated in larval fish. Monoamine oxidase (MAO), an enzyme that catabolizes monoamines DA and 5-HT, was also reduced in mRNA abundance. We hypothesize that DA synthesis and monoamine metabolism are associated with behavioral alterations. This study elucidates putative mechanisms and exposure risks to wildlife and humans by characterizing phosphatic REE-induced neurotoxicity in developing zebrafish.

Differential Neuroprotective Effects of N-Acetylcysteine against Dithianon Toxicity in Glutamatergic, Dopaminergic, and GABAergic Neurons: Assessment Using Zebrafish

Despite the widespread agricultural use of dithianon as an antifungal agent, its neurotoxic implications for humans and wildlife have not been comprehensively explored. Using zebrafish embryonic development as our model, we found that dithianon treatment induced behavioral alterations in zebrafish larvae that appeared normal. Detailed quantitative analyses showed that dithianon at ≥0.0001 µgmL-1 induced cytoplasmic and mitochondrial antioxidant responses sequentially, followed by the disruption of mitochondrial and cellular homeostasis. Additionally, dithianon at 0.01 and 0.1 µgmL-1 downregulated the expressions of glutamatergic (slc17a6b), GABAergic (gad1b), and dopaminergic (th) neuronal markers. Contrarily, dithianon upregulated the expression of the oligodendrocyte marker (olig2) at concentrations of 0.001 and 0.01 µgmL-1, concurrently suppressing the gene expression of the glucose transporter slc2a1a/glut1. Particularly, dithianon-induced increase in reactive oxygen species (ROS) production was reduced by both N-acetylcysteine (NAC) and betaine; however, only NAC prevented dithianon-induced mortality of zebrafish embryos. Moreover, NAC specifically prevented dithianon-induced alterations in glutamatergic and dopaminergic neurons while leaving GABAergic neurons unaffected, demonstrating that the major neurotransmission systems in the central nervous system differentially respond to the protective effects. Our findings contribute to a better understanding of the neurotoxic potential of dithianon and to developing preventive strategies.

Animal models of silicosis: fishing for new therapeutic targets and treatments

Silicosis as an occupational lung disease has been present in our lives for centuries. Research studies have already developed and implemented many animal models to study the pathogenesis and molecular basis of the disease and enabled the search for treatments. As all experimental animal models used to date have their advantages and disadvantages, there is a continuous search for a better model, which will not only accelerate basic research, but also contribute to clinical aspects and drug development. We review here, for the first time, the main animal models developed to date to study silicosis and the unique advantages of the zebrafish model that make it an optimal complement to other models. Among the main advantages of zebrafish for modelling human diseases are its ease of husbandry, low maintenance cost, external fertilisation and development, its transparency from early life, and its amenability to chemical and genetic screening. We discuss the use of zebrafish as a model of silicosis, its similarities to other animal models and the characteristics of patients at molecular and clinical levels, and show the current state of the art of inflammatory and fibrotic zebrafish models that could be used in silicosis research.

Comparison of Efavirenz and Doravirine Developmental Toxicity in an Embryo Animal Model

In the past, one of the most widely used non-nucleoside reverse transcriptase inhibitors (NNRTI) in first-line antiretroviral therapy (ART) of HIV infection was efavirenz (EFV), which is already used as a cost-effective treatment in developing countries due to its efficacy, tolerability, and availability. However, EFV also demonstrates several adverse effects, like hepatotoxicity, altered lipid profile, neuropsychological symptoms, and behavioral effects in children after in utero exposure. In 2018, another NNRTI, doravirine (DOR), was approved due to its similar efficacy but better safety profile. Preclinical safety studies demonstrated that DOR is not genotoxic and exhibits no developmental toxicity or effects on fertility in rats. Zebrafish (Danio rerio) embryos have been widely accepted as a vertebrate model for pharmacological and developmental studies. We used zebrafish embryos as an in vivo model to investigate the developmental toxicity of DOR compared to EFV. After exposure of the embryos to the drugs from the gastrula stage up to different developmental stages (30 embryos for each arm, in three independent experiments), we assessed their survival, morphology, hatching rate, apoptosis in the developing head, locomotion behavior, vasculature development, and neutral lipid distribution. Overall, DOR showed a better safety profile than EFV in our model. Therapeutic and supra-therapeutic doses of DOR induced very low mortality [survival rates: 92, 90, 88, 88, and 81% at 1, 5, 10, 25, and 50 μM, respectively, at 24 h post fecundation (hpf), and 88, 85, 88, 89, and 75% at the same doses, respectively, at 48 hpf] and mild morphological alterations compared to EFV exposure also in the sub-therapeutic ranges (survival rates: 80, 77, 69, 63, and 44% at 1, 5, 10, 25, and 50 μM, respectively, at 24 hpf and 72, 70, 63, 52, and 0% at the same doses, respectively, at 48 hpf). Further, DOR only slightly affected the hatching rate at supra-therapeutic doses (97, 98, 96, 87, and 83% at 1, 5, 10, 25, and 50 μM, respectively, at 72 hpf), while EFV already strongly reduced hatching at sub-therapeutic doses (83, 49, 11, 0, and 0% at 1, 5, 10, 25, and 50 μM, respectively, at the same time endpoint). Both DOR at therapeutic doses and most severely EFV at sub-therapeutic doses enhanced apoptosis in the developing head during crucial phases of embryo neurodevelopment and perturbed the locomotor behavior. Furthermore, EFV strongly affected angiogenesis and disturbed neutral lipid homeostasis even at sub-therapeutic doses compared to DOR at therapeutic concentrations. Our findings in zebrafish embryos add further data confirming the higher safety of DOR with respect to EFV regarding embryo development, neurogenesis, angiogenesis, and lipid metabolism. Further studies are needed to explore the molecular mechanisms underlying the better pharmacological safety profile of DOR, and further human studies are required to confirm these results in the zebrafish animal model.

Imaging Approaches to Investigate Pathophysiological Mechanisms of Brain Disease in Zebrafish

Zebrafish has become an essential model organism in modern biomedical research. Owing to its distinctive features and high grade of genomic homology with humans, it is increasingly employed to model diverse neurological disorders, both through genetic and pharmacological intervention. The use of this vertebrate model has recently enhanced research efforts, both in the optical technology and in the bioengineering fields, aiming at developing novel tools for high spatiotemporal resolution imaging. Indeed, the ever-increasing use of imaging methods, often combined with fluorescent reporters or tags, enable a unique chance for translational neuroscience research at different levels, ranging from behavior (whole-organism) to functional aspects (whole-brain) and down to structural features (cellular and subcellular). In this work, we present a review of the imaging approaches employed to investigate pathophysiological mechanisms underlying functional, structural, and behavioral alterations of human neurological diseases modeled in zebrafish.

Application of Zebrafish as a Model for Anti-Cancer Activity Evaluation and Toxicity Testing of Natural Products

Developing natural product-based anti-cancer drugs/agents is a promising way to overcome the serious side effects and toxicity of traditional chemotherapeutics for cancer treatment. However, rapid assessment of the in vivo anti-cancer activities of natural products is a challenge. Alternatively, zebrafish are useful model organisms and perform well in addressing this challenging issue. Nowadays, a growing number of studies have utilized zebrafish models to evaluate the in vivo activities of natural compounds. Herein, we reviewed the application of zebrafish models for evaluating the anti-cancer activity and toxicity of natural products over the past years, summarized its process and benefits, and provided future outlooks for the development of natural product-based anti-cancer drugs.

A p21-GFP zebrafish model of senescence for rapid testing of senolytics in vivo

Senescence drives the onset and severity of multiple ageing-associated diseases and frailty. As a result, there has been an increased interest in mechanistic studies and in the search for compounds targeting senescent cells, known as senolytics. Mammalian models are commonly used to test senolytics and generate functional and toxicity data at the level of organs and systems, yet this is expensive and time consuming. Zebrafish share high homology in genes associated with human ageing and disease. They can be genetically modified relatively easily. In larvae, most organs develop within 5 days of fertilisation and are transparent, which allows tracking of fluorescent cells in vivo in real time, testing drug off-target toxicity and assessment of cellular and phenotypic changes. Here, we have generated a transgenic zebrafish line that expresses green fluorescent protein (GFP) under the promoter of a key senescence marker, p21. We show an increase in p21:GFP+ cells in larvae following exposure to ionising radiation and with natural ageing. p21:GFP+ cells display other markers of senescence, including senescence-associated β-galactosidase and IL6. The observed increase in senescent cells following irradiation is associated with a reduction in the thickness of muscle fibres and mobility, two important ageing phenotypes. We also show that quercetin and dasatinib, two senolytics currently in clinical trials, reduce the number of p21:GFP+ cells, in a rapid 5-day assay. This model provides an important tool to study senescence in a living organism, allowing the rapid selection of senolytics before moving to more expensive and time-consuming mammalian systems.

Preclinical models for drug discovery for metastatic disease

Despite many advances, metastatic disease remains essentially uncurable. Thus, there is an urgent need to better understand mechanisms that promote metastasis, drive tumor evolution, and underlie innate and acquired drug resistance. Sophisticated preclinical models that recapitulate the complex tumor ecosystem are key to this process. We begin with syngeneic and patient-derived mouse models that are the backbone of most preclinical studies. Second, we present some unique advantages of fish and fly models. Third, we consider the strengths of 3D culture models for resolving remaining knowledge gaps. Finally, we provide vignettes on multiplexed technologies to advance our understanding of metastatic disease.

Three-dimensional cerebral vasculature topological parameter extraction of transgenic zebrafish embryos with a filling-enhancement deep learning network

Quantitative analysis of zebrafish cerebral vasculature is essential for the study of vascular development and disease. We developed a method to accurately extract the cerebral vasculature topological parameters of transgenic zebrafish embryos. The intermittent and hollow vascular structures of transgenic zebrafish embryos, obtained from 3D light-sheet imaging, were transformed into continuous solid structures with a filling-enhancement deep learning network. The enhancement enables the extraction of 8 vascular topological parameters accurately. Quantitation of the zebrafish cerebral vasculature vessels with the topological parameters show a developmental pattern transition from 2.5 to 5.5 dpf.

Ipconazole Disrupts Mitochondrial Homeostasis and Alters GABAergic Neuronal Development in Zebrafish

Ipconazole, a demethylation inhibitor of fungal ergosterol biosynthesis, is widely used in modern agriculture for foliar and seed treatment, and is authorized for use in livestock feed. Waste from ipconazole treatment enters rivers and groundwater through disposal and rain, posing potential toxicity to humans and other organisms. Its metabolites remain stable under standard hydrolysis conditions; however, their neurodevelopmental toxicity is unknown. We investigated the potential neurodevelopmental toxicity of ipconazole pesticides in zebrafish (Danio rerio). Our behavioral monitoring demonstrated that the locomotive activity of ipconazole-exposed zebrafish larvae was reduced during early development, even when morphological abnormalities were undetected. Molecular profiling demonstrated that the mitochondrial-specific antioxidants, superoxide dismutases 1 and 2, and the genes essential for mitochondrial genome maintenance and functions were specifically reduced in ipconazole-treated (0.02 μg/mL) embryos, suggesting underlying ipconazole-driven oxidative stress. Consistently, ipconazole treatment substantially reduced hsp70 expression and increased ERK1/2 phosphorylation in a dose-dependent manner. Interrupted gad1b expression confirmed that GABAergic inhibitory neurons were dysregulated at 0.02 μg/mL ipconazole, whereas glutamatergic excitatory and dopaminergic neurons remained unaffected, resulting in an uncoordinated neural network. Additionally, ipconazole-treated (2 μg/mL) embryos exhibited caspase-independent cell death. This suggests that ipconazole has the potential to alter neurodevelopment by dysregulating mitochondrial homeostasis.

Cardiac Neural Crest and Cardiac Regeneration

Neural crest cells (NCCs) are a vertebrate-specific, multipotent stem cell population that have the ability to migrate and differentiate into various cell populations throughout the embryo during embryogenesis. The heart is a muscular and complex organ whose primary function is to pump blood and nutrients throughout the body. Mammalian hearts, such as those of humans, lose their regenerative ability shortly after birth. However, a few vertebrate species, such as zebrafish, have the ability to self-repair/regenerate after cardiac damage. Recent research has discovered the potential functional ability and contribution of cardiac NCCs to cardiac regeneration through the use of various vertebrate species and pluripotent stem cell-derived NCCs. Here, we review the neural crest's regenerative capacity in various tissues and organs, and in particular, we summarize the characteristics of cardiac NCCs between species and their roles in cardiac regeneration. We further discuss emerging and future work to determine the potential contributions of NCCs for disease treatment.

Longitudinal in vivo imaging of adult Danionella cerebrum using standard confocal microscopy

Danionella cerebrum is a new vertebrate model that offers an exciting opportunity to visualize dynamic biological processes in intact adult animals. Key advantages of this model include its small size, life-long optical transparency, genetic amenability and short generation time. Establishing a reliable method for longitudinal in vivo imaging of adult D. cerebrum while maintaining viability will allow in-depth image-based studies of various processes involved in development, disease onset and progression, wound healing, and aging in an intact live animal. Here, a method for both prolonged and longitudinal confocal live imaging of adult D. cerebrum using custom-designed and 3D-printed imaging chambers is described. Two transgenic D. cerebrum lines were created to test the imaging system, i.e. Tg(mpeg1:dendra2) and Tg(kdrl:mCherry-caax). The first line was used to visualize macrophages and microglia, and the second for spatial registration. By using this approach, differences in immune cell morphology and behavior during homeostasis as well as in response to a stab wound or two-photon-induced brain injury were observed in intact adult fish over the course of several days.

Therapeutic Potential of Deflamin against Colorectal Cancer Development and Progression

Matrix metalloproteinases (MMPs) are proteolytic enzymes that play a crucial role in tumor microenvironment remodeling, contributing to inflammatory and angiogenic processes, and ultimately promoting tumor maintenance and progression. Several studies on bioactive polypeptides isolated from legumes have shown anti-migratory, anti-MMPs, and anti-tumor effects, potentially constituting novel strategies for both the prevention and progression of cancer. In this work, we investigated the anti-tumor role of deflamin, a protein oligomer isolated from white lupine seeds (Lupinus albus) reported to inhibit MMP-9 and cell migration in colorectal cancer (CRC) cell lines. We found that deflamin exerts an inhibitory effect on tumor growth and metastasis formation, contributing to increased tumor apoptosis in the xenotransplanted zebrafish larvae model. Furthermore, deflamin resulted not only in a significant reduction in MMP-2 and MMP-9 activity but also in impaired cancer cell migration and invasion in vitro. Using the xenograft zebrafish model, we observed that deflamin inhibits collagen degradation and angiogenesis in the tumor microenvironment in vivo. Overall, our work reveals the potential of deflamin as an agent against CRC development and progression.

Zebrafish Models of Paediatric Brain Tumours

Paediatric brain cancer is the second most common childhood cancer and is the leading cause of cancer-related deaths in children. Despite significant advancements in the treatment modalities and improvements in the 5-year survival rate, it leaves long-term therapy-associated side effects in paediatric patients. Addressing these impairments demands further understanding of the molecularity and heterogeneity of these brain tumours, which can be demonstrated using different animal models of paediatric brain cancer. Here we review the use of zebrafish as potential in vivo models for paediatric brain tumour modelling, as well as catalogue the currently available zebrafish models used to study paediatric brain cancer pathophysiology, and discuss key findings, the unique attributes that these models add, current challenges and therapeutic significance.

Pro-Angiogenetic Effects of Purified Extracts from Helix aspersa during Zebrafish Development

Helix aspersa is a species of land snail belonging to the Helicidae family, widespread in the Mediterranean and continental area up to Northern Europe. In some areas it is appreciated as a food, but is mostly considered a parasite of gardens and cultivated fields. The mucus of Helix aspersa has found multiple applications in the cosmetic and health fields. In the present study, we investigated for the first time the angiogenetic properties of purified extracts from Helix aspersa using a transgenic zebrafish line Tg (kdrl:EGFP). The angiogenesis induced by purified snail extracts was demonstrated by their capability to increase the three well-established parameters of angiogenesis: generation of intersegmental vessels, modeling of caudal venous plexus, and formation of sub-intestinal venous plexus. The effects appeared to be mediated by the vascular endothelial growth factor (VEGF) pathway, being prevented by pretreatment of embryos with the selective VEGF receptor antagonist SU5416, and supported by the increased VEGF mRNA levels found in snail-extract-treated embryos. Insufficient vascular supply is underlined by low VEGF signaling, primarily because of its indispensable role in preventing capillary loss. Our findings might have a pharmacological impact by counteracting VEGF hypofunction and promoting angiogenesis to maintain adequate microvascular and vascular density in normal and suffering tissues and organs.

A Rapid and Noninvasive Method That Extracts Polymerase Chain Reaction-Ready Genomic DNA from Adult Zebrafish

Genotyping usually entails analysis of the products of polymerase chain reaction (PCR) carried out with genomic DNA (gDNA) as template, and is employed for validation of mutant or transgenic organisms. For genotyping of adult zebrafish, gDNA is often extracted from clipped caudal fin or skin mucus through either alkaline lysis using NaOH or proteinase K (PK) treatment. Further purification of the gDNA using ethanol precipitation was optional. To develop a rapid and noninvasive method that extracts PCR-ready gDNA from adult zebrafish, we combined skin swabbing with PK treatment and demonstrated its efficiency. This method could be applied to a wide range of fish.

ZeBraInspector, a platform for the automated segmentation and analysis of body and brain volumes in whole 5 days post-fertilization zebrafish following simultaneous visualization with identical orientations

In recent years, the zebrafish has become a well-established laboratory model. We describe here the ZeBraInspector (ZBI) platform for high-content 3D imaging (HCI) of 5 days post-fertilization zebrafish eleuthero-embryos (EEs). This platform includes a mounting method based on 3D-printed stamps to create a grid of wells in an agarose cast, facilitating batch acquisitions with a fast-confocal laser scanning microscope. We describe reference labeling in cleared fish with a fluorescent lipophilic dye. Based on this labeling, the ZBI software registers. EE 3D images, making it possible to visualize numerous identically oriented EEs on a single screen, and to compare their morphologies and any fluorescent patterns at a glance. High-resolution 2D snapshots can be extracted. ZBI software is therefore useful for diverse high-content analyses (HCAs). Following automated segmentation of the lipophilic dye signal, the ZBI software performs volumetric analyses on whole EEs and their nervous system white matter. Through two examples, we illustrate the power of these analyses for obtaining statistically significant results from a small number of samples: the characterization of a phenotype associated with a neurodevelopmental mutation, and of the defects caused by treatments with a toxic anti-cancer compound.

Transgenic zebrafish larvae as a non-rodent alternative model to assess pro-inflammatory (neutrophil) responses to nanomaterials

Hazard studies for nanomaterials (NMs) commonly assess whether they activate an inflammatory response. Such assessments often rely on rodents, but alternative models are needed to support the implementation of the 3Rs principles. Zebrafish (Danio rerio) offer a viable alternative for screening NM toxicity by investigating inflammatory responses. Here, we used non-protected life stages of transgenic zebrafish (Tg(mpx:GFP)ⁱ¹¹⁴) with fluorescently-labeled neutrophils to assess inflammatory responses to silver (Ag) and zinc oxide (ZnO) NMs using two approaches. Zebrafish were exposed to NMs via water following a tail fin injury, or NMs were microinjected into the otic vesicle. Zebrafish were exposed to NMs at 3 days post-fertilization (dpf) and neutrophil accumulation at the injury or injection site was quantified at 0, 4, 6, 8, 24, and 48 h post-exposure. Zebrafish larvae were also exposed to fMLF, LTB₄, CXCL-8, C5a, and LPS to identify a suitable positive control for inflammation induction. Aqueous exposure to Ag and ZnO NMs stimulated an enhanced and sustained neutrophilic inflammatory response in injured zebrafish larvae, with a greater response observed for Ag NMs. Following microinjection, Ag NMs stimulated a time-dependent neutrophil accumulation in the otic vesicle which peaked at 48 h. LTB₄ was identified as a positive control for studies investigating inflammatory responses in injured zebrafish following aqueous exposure, and CXCL-8 for microinjection studies that assess responses in the otic vesicle. Our findings support the use of transgenic zebrafish to rapidly screen the pro-inflammatory effects of NMs, with potential for wider application in assessing chemical safety (e.g. pharmaceuticals).