Vascular development in the zebrafish

Nuclear envelope components in vascular mechanotransduction: emerging roles in vascular health and disease

The vascular network, uniquely sensitive to mechanical changes, translates biophysical forces into biochemical signals for vessel function. This process relies on the cell's architectural integrity, enabling uniform responses to physical stimuli. Recently, the nuclear envelope (NE) has emerged as a key regulator of vascular cell function. Studies implicate nucleoskeletal elements (e.g. nuclear lamina) and the linker of nucleoskeleton and cytoskeleton (LINC) complex in force transmission, emphasizing nucleo-cytoskeletal communication in mechanotransduction. The nuclear pore complex (NPC) and its component proteins (i.e. nucleoporins) also play roles in cardiovascular disease (CVD) progression. We herein summarize evidence on the roles of nuclear lamina proteins, LINC complex members, and nucleoporins in endothelial and vascular cell mechanotransduction. Numerous studies attribute NE components in cytoskeletal-related cellular behaviors to insinuate dysregulation of nucleocytoskeletal feedback and nucleocytoplasmic transport as a mechanism of endothelial and vascular dysfunction, and hence implications for aging and vascular pathophysiology.

Small Black Phosphorus Disrupts Vascular Development and Hematopoiesis in Zebrafish Larvae

Black phosphorus (BP), a novel two-dimensional (2D) material, has shown promising applications in the optoelectronic, biological, and medical fields in recent years. However, its increasing use may lead to its inadvertent environmental release, creating potential ecological and health risks that remain poorly understood. In this study, wild-type and transgenic zebrafish were used to evaluate the potential developmental toxicity of small-size BP (S-BP), with a lateral particle size of 154.4 ± 34.6 nm, focusing specifically on vascular growth and hematopoiesis at relatively low concentrations of 0.025, 0.05, 0.1, and 0.2 mg/L. The results indicated that S-BP adhered to the chorion and induced developmental defects. The uninflated swim bladders and decreased heart rate were observed in S-BP-exposed larvae at 120 hpf. The angioarchitectural profiling using transgenic zebrafish showed that exposure to S-BP adversely impaired blood vessel development at 72 hpf, especially in the common cardinal vein (CCV). Moreover, erythropoiesis and the flow velocity of red blood cells (RBCs) were disturbed at 120 hpf in all of the S-BP-exposed groups. Transcriptomic analysis unveiled that S-BP exposure altered gene expression related to angiogenesis, hematopoiesis, ribosome function, and transport processes. Notably, the mRNA levels of vascular and hematopoietic markers, including clec14a, nme2b.1, klf2a, slc2a1a, csf1rb, atf3, scl, and scml4, were significantly downregulated following S-BP exposure. Our findings revealed that low concentrations of S-BP exposure caused vascular and hematologic toxicity and identified CCV and RBCs as sensitive targets. This work expands our understanding of the toxicity of 2D nanomaterials and provides critical data for environmental risk assessment.

Larval zebrafish burn wound infection model reveals conserved innate immune responses against diverse pathogenic fungi

Secondary fungal infections represent a major complication following thermal injuries. However, the mechanisms of fungal colonization of burn tissue and how the host subsequently responds to fungi within this niche remain unclear. We have previously reported a zebrafish model of thermal injury that recapitulates many of the features of human burn wounds. Here, we characterize host-fungal interaction dynamics within the burn wound niche using two of the most common fungal pathogens isolated from burn injuries, Aspergillus fumigatus and Candida albicans. Both A. fumigatus and C. albicans colonize burned tissue in zebrafish larvae and induce a largely conserved innate immune response following colonization. Using drug-induced cell-depletion strategies and transgenic zebrafish lines with impaired innate immune function, we found that macrophages control fungal burden, whereas neutrophils primarily control invasive hyphal growth at the early stages of infection. However, we also found that loss of either immune cell can be compensated by the other at the later stages of infection and that fish with both macrophage and neutrophil deficiencies show more invasive hyphal growth that is sustained throughout the infection process, suggesting redundancy in their antifungal activities. Finally, we demonstrate that C. albicans strains with increased β(1,3)-glucan exposure are cleared faster from the burn wound, demonstrating a need for shielding this immunogenic cell wall epitope for the successful fungal colonization of burn tissue. Together, our findings support the use of zebrafish larvae as a model to study host-fungal interaction dynamics within burn wounds.IMPORTANCESecondary fungal infections within burn wound injuries are a significant problem that delays wound healing and increases the risk of patient mortality. Currently, little is known about how fungi colonize and infect burn tissue or how the host responds to pathogen presence. In this report, we expand upon an existing thermal injury model using zebrafish larvae to begin elucidating both the host immune response to fungal burn colonization and fungal mechanisms for persistence within burn tissue. We found that both Aspergillus fumigatus and Candida albicans, common fungal burn wound isolates, successfully colonize burn tissue and are effectively cleared in immunocompetent zebrafish by both macrophages and neutrophils. We also find that C. albicans mutants harboring mutations that impact their ability to evade host immune system recognition are cleared more readily from burn tissue. Collectively, our work highlights the efficacy of using zebrafish to study host-fungal interaction dynamics within burn wounds.

DDX24 spatiotemporally orchestrates VEGF and Wnt signaling during developmental angiogenesis

Vascular development is a precisely controlled process, yet how it is spatiotemporally orchestrated remains enigmatic. We previously identified DEAD-box RNA helicase 24 (DDX24) as a pathogenic gene for multiorgan vascular anomalies. Here, we show that DDX24 is expressed in the endothelium during embryonic angiogenesis in zebrafish. DDX24 deficiency causes intersegmental vessel hyperbranching in the trunk, but inhibits central artery angiogenesis in the brain. Mechanistically, DDX24 deficiency enhances VEGFR2 expression by direct binding to its mRNA in nonbrain endothelial cells (ECs), while suppressing GPR124/RECK-mediated Wnt signaling in brain ECs. Additionally, spatial transcriptome analysis profiles DDX24-mediated crosstalk between ECs and neighboring cells. Finally, pharmacological targeting of these two pathways in a temporal manner can rescue the phenotypes induced by DDX24 deficiency. Overall, our findings highlight an essential role for DDX24 in the spatiotemporal regulation of developmental angiogenesis.

G protein-coupled receptor GPR182 negatively regulates sprouting angiogenesis via modulating CXCL12-CXCR4 axis signaling

Angiogenesis is a critical process for tumor progression, regulated by various signaling pathways. Although antiangiogenic therapies targeting the VEGF pathway have shown potential, their effectiveness is inconsistent across different tumor types. GPR182, an endothelial cell-specific G protein-coupled receptor, is frequently downregulated in hypervascular tumors, but its specific role in angiogenesis has not been well defined. Our study reveals that GPR182 expression is markedly reduced in hepatocellular carcinoma (HCC) and inversely correlates with CD31, a pan-endothelial marker. In zebrafish embryos, Gpr182 deficiency resulted in enhanced angiogenic sprouting and hypervascularization, and GPR182-deficient human umbilical vein endothelial cells (HUVECs) showed increased migration and proliferation. At the molecular level, GPR182 acts as a decoy receptor, binding CXCL12 and regulating its gradient, which in turn suppresses CXCR4-mediated angiogenesis. The pharmacological blockade of CXCR4 with AMD3100 corrected the abnormal angiogenic phenotype in Gpr182-deficient zebrafish embryos and in the livers of a zebrafish HCC model. This work uncovers GPR182 as a negative regulator of angiogenesis, a key process in tumor growth and metastasis, and proposes that targeting GPR182 may offer a novel therapeutic approach for antiangiogenic strategies in cancer treatment.

RAS Pathway Mutations and Therapeutics in Vascular Anomalies

Vascular anomalies (VAs) are a diverse group of vascular tumors and vascular malformations (VMs). VMs are characterized by abnormal vessel development, overgrowth, and dysfunction. Coagulopathy, edema, and effusions can cause severe morbidity and mortality in children and adults with these diseases. Germline or somatic mutations in the RAS/RAF/MAPK pathway have been identified in multiple types of VAs. RAS genes (KRAS, NRAS, and HRAS) are small GTPase proteins that play an important role in normal development and cell function. In healthy cells, RAS proteins cycle between GDP (inactive) and GTP (active) states that regulate important functions such as proliferation, migration, and survival. "Hot spot" mutations in codons 12, 13, or 61 of RAS genes are found in multiple tumor types and VAs. RAS mutations often cause excessive MAP kinase signaling, driving unchecked cell proliferation. In this review, we discuss the different RAS pathway mutations discovered in VAs and the role that these may play using insights from cell and animal models. Current therapies targeting RAS pathways are presented. In the future, a better understanding of the role of RAS pathway mutations may advance therapeutic strategies for people with VAs.

The sprouting angiogenesis and vascular dysfunction triggered by bisphenol S and tetrabromobisphenol S through disrupting vascular endothelial-cadherin in zebrafish

Exogenous chemical toxicants may be important inducers of pathological angiogenesis diseases. However, few studies have investigated the associations between pathological angiogenesis diseases and chemical toxicant exposures, and the specific mechanism by which chemical toxicants induce sprouting angiogenesis is unclear. In this study, zebrafish were exposed to bisphenol S (BPS, 1-100 μg/L) and tetrabromobisphenol S (TBBPS, 0.1 and 10 μg/L) from the embryonic stage to the larval stage to investigate how pollutants interfere with angiogenesis and the function of ectopic sprouting vessels. The results showed that BPS and TBBPS promoted ectopic sprouting angiogenesis in different types of vascular plexuses, including the posterior cardinal vein (PCV) and superficial choroidal vessels (SOVs), at different developmental time points. Proteomic analyses of eGFP-positive endothelial cells (ECs) isolated from Tg(flk1: eGFP) zebrafish revealed that both BPS and TBBPS induced ectopic angiogenesis by acting on vascular endothelial-cadherin (VE-cadherin) and activating downstream proangiogenic signaling. In ectopic sprouting vessels induced by BPS and TBBPS, increased endothelial permeability resulted in white blood cell recruitment. Human oxidized lipids also tended to deposit in these ectopic vessels following BPS and TBBPS exposure. These findings suggest that chemical toxicant-induced ectopic angiogenesis is an important cause of vascular dysfunction and related diseases.

Deletion of hepcidin disrupts iron homeostasis and hematopoiesis in zebrafish embryogenesis

Iron is essential for cell growth and hematopoiesis, which is regulated by hepcidin (hamp). However, the role of hamp in zebrafish hematopoiesis remains unclear. Here, we have created a stable hamp knockout zebrafish model using the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated nuclease 9 system (CRISPR/Cas9 system). Our study revealed that hamp deletion led to maternal iron overload in embryos, significantly downregulating hemoglobin genes and reducing hemoglobin content. Single-cell RNA sequencing identified abnormal expression patterns in blood progenitor cells, with a specific progenitor subtype showing increased ferroptosis and delayed development. By crossing hamp knockout zebrafish with a gata1+ line (blood cells labeled fish line), we confirmed ferroptosis in blood progenitor cells. These findings underscore the crucial role of hamp in iron regulation and hematopoiesis, offering novel insights into developmental biology and potential therapeutic targets for blood disorders.

Zebrafish as a Suitable Model for Utilizing the Bioactivity of Coumarins and Coumarin-Based Compounds

The aim of this review is to summarize the current knowledge on the use of coumarin-derived compounds in the zebrafish (Danio rerio) model. Coumarins, a class of naturally occurring compounds with diverse biological activities, including compounds such as coumarin, angelicin, and warfarin, have attracted considerable attention in the study of potential therapeutic agents for cancer, central nervous system disorders, and infectious diseases. The capabilities of coumarins as active compounds have led to synthesizing various derivatives with their own properties. While such variety is certainly promising, it is also cumbersome due to the large amount of research needed to find the most optimal compounds. The zebrafish model offers unique advantages for such studies, including high genetic and physiological homology to mammals, optical transparency of the embryos, and rapid developmental processes, facilitating the assessment of compound toxicity and underlying mechanisms of action. This review provides an in-depth analysis of the chemical properties of coumarins, their mechanisms of biological activity, and the results of previous studies evaluating the toxicity and efficacy of these compounds in zebrafish assays. The zebrafish model allows for a holistic assessment of the therapeutic potential of coumarin derivatives, offering valuable insights for advancing drug discovery and development.

Swimming motions evoke Ca2+ events in vascular endothelial cells of larval zebrafish via mechanical activation of Piezo1

Calcium signaling in blood vessels regulates their growth1,2, immune response3, and vascular tone4. Vascular endothelial cells are known to be mechanosensitive5-7, and it has been assumed that this mechanosensation mediates calcium responses to pulsatile blood flow8-10. Here we show that in larval zebrafish, the dominant trigger for vascular endothelial Ca2+ events comes from body motion, not heartbeat-driven blood flow. Through a series of pharmacological and mechanical perturbations, we showed that body motion is necessary and sufficient to induce endothelial Ca2+ events, while neither neural activity nor blood circulation is either necessary or sufficient. Knockout and temporally restricted knockdown of piezo1 eliminated the motion-induced Ca2+ events. Our results demonstrate that swimming-induced tissue motion is an important driver of endothelial Ca2+ dynamics in larval zebrafish.

Mechanistic insight into the neurodevelopmental toxicity of the novel pesticide pyrifluquinazon (PFQ) and its major metabolite in early-life stage zebrafish

Pyrifluquinazon (PFQ), a novel insecticide containing a heptafluoroisopropyl moiety, has seen increasing use. However, limited research has been conducted on the toxicological effects and mechanisms of PFQ in aquatic organisms. To investigate the toxicity and underlying mechanisms of PFQ and its primary metabolite dPFQ in aquatic organisms, morphological, behavioral, hormonal, multi-omics analyses, and molecular docking studies were conducted on zebrafish larvae after exposure. The results showed that both PFQ and dPFQ induced developmental abnormalities, behavioral impairment, hormonal disruptions, and alterations in neurologically related metabolites and gene expression in early-stage zebrafish. Notably, delayed retinal vascular development was observed, which is also likely linked to the neurodevelopmental toxicity. Subsequently, identification and relative quantification of PFQ metabolites suggested that its toxicity might be primarily attributed to dPFQ. Finally, an Adverse Outcome Pathway (AOP) was proposed, initiating with the binding of dPFQ to the TRPV4 protein and ultimately leading to neurodevelopmental toxicity. This study delineated the neurodevelopmental toxicity of PFQ and its toxicological mechanisms in zebrafish, emphasizing the hazards posed by pesticide metabolites to non-target organisms and highlighting inherent limitations of extrapolating in vitro toxicity experiments.

Exploring micro(nano)plastics toxicity from an environmental management perspective: Zebrafish as a vital bridge for assessing potential human health risks

The pollution stemming from the unwarranted utilization and inadequate disposal of plastic products is undergoing rapid escalation. The problem of micro(nano)plastics (MNPs) pollution has recently garnered significant attention, and the issue of human exposure to MNPs cannot be disregarded. However, the present state of research concerning human exposure to MNPs remains in its early stages. The inherent uncertainty and variability associated with MNPs pose significant obstacles to conducting related studies. In order to enhance comprehension of the potential health risks associated with human exposure to MNPs, the utilization of zebrafish as an assessment tool was deemed appropriate. Zebrafish, as one of the most effective toxicological models, assume a significant role in both environmental monitoring and health modeling. This study provides a review of the effects of exposure to MNPs on zebrafish. The findings demonstrate that such exposure can elicit behavioral and physiological alterations in zebrafish, subsequently resulting in a range of toxic consequences. Simultaneously, this study conducts a comparative analysis of the effects of human and zebrafish exposure to MNPs in physiology, exposure environment, and toxicokinetic/toxicodynamic, leveraging the shared characteristics between zebrafish and humans to augment comprehension regarding human exposure to MNPs. Zebrafish model plays a key role in exploring gene expression in human homologous pathways caused by MNPs exposure, and strengthens the understanding of the risk of MNPs exposure. However, physiological, metabolic, and exposure circumstances limit its extrapolation to humans. Furthermore, the reference value and challenge associated with employing zebrafish as a model to discern human health hazards linked to MNPs are assessed, accompanied by suggestions for future research endeavors.

How Tumors Affect Hemodynamics: A Diffusion Study on the Zebrafish Transplantable Model of Medullary Thyroid Carcinoma by Selective Plane Illumination Microscopy

Medullary thyroid carcinoma (MTC), a rare neuroendocrine tumor comprising 3-5% of thyroid cancers, arises from calcitonin-producing parafollicular C cells. Despite aggressive behavior, surgery remains the primary curative treatment, with limited efficacy reported for radiotherapy and chemotherapy. Recent efforts have explored the pathogenetic mechanisms of MTC, identifying it as a highly vascularized neoplasm overexpressing pro-angiogenic factors. Building on the established benefits of zebrafish embryos, we previously created an in vivo MTC xenograft platform that allows real-time observation of tumor-induced angiogenesis and evaluation of the anti-angiogenic effects of tyrosine kinase inhibitors. In this study, we present a method using selective plane illumination microscopy (SPIM) to characterize vascular permeability in these xenografted embryos. Taking advantage of dextran injections into the blood flow of zebrafish embryos, we found that the diffusion coefficient in embryos grafted with MTC cells was about tenfold lower compared with the same parameter in controls. The results demonstrate the potential of our approach to estimate diffusion parameters, providing valuable insights into vascular permeability changes in MTC-implanted zebrafish embryos compared with controls. Our study sheds light on the intricate vascular biology of MTC, offering a promising tool for future investigations into tumor-induced angiogenesis and therapeutic strategies in diverse neoplasms.

A conserved in vivo burn wound infection model for diverse pathogenic fungi

Secondary fungal infections represent a major complication following thermal injuries. However, the mechanisms of fungal colonization of burn tissue and how the host subsequently responds to fungi within this niche remain unclear. We have previously reported a zebrafish model of thermal injury that recapitulates many of the features of human burn wounds. Here, we characterize host-fungal interaction dynamics within the burn wound niche using two of the most common fungal pathogens isolated from burn injuries, Aspergillus fumigatus and Candida albicans . Both A. fumigatus and C. albicans colonize burned tissue in zebrafish larvae and induce a largely conserved innate immune response following colonization. Using drug-induced cell depletion strategies and transgenic zebrafish lines with impaired innate immune function, we found that macrophages control fungal burden while neutrophils primarily control invasive hyphal growth at the early stages of infection. However, we also found that loss of either immune cell can be compensated by the other at the later stages of infection, and that fish with both macrophage and neutrophil deficiencies show more invasive hyphal growth that is sustained throughout the infection process, suggesting redundancy in their antifungal activities. Finally, we demonstrate that C. albicans strains with increased β(1,3)-glucan exposure are cleared faster from the burn wound, demonstrating a need for shielding this immunogenic cell wall epitope for successful fungal colonization of burn tissue. Together, our findings support the use of zebrafish larvae as a model to study host-fungal interaction dynamics within burn wounds.

Importance

Secondary fungal infections within burn wound injuries are a significant problem that delay wound healing and increase the risk of patient mortality. Currently, little is known about how fungi colonize and infect burn tissue or how the host responds to pathogen presence. In this report, we expand upon an existing thermal injury model using zebrafish larvae to begin to elucidate both the host immune response to fungal burn colonization and fungal mechanisms for persistence within burn tissue. We found that both Aspergillus fumigatus and Candida albicans , common fungal burn wound isolates, successfully colonize burn tissue and are effectively cleared in immunocompetent zebrafish by both macrophages and neutrophils. We also find that C. albicans mutants harboring mutations that impact their ability to evade host immune system recognition are cleared more readily from burn tissue. Collectively, our work highlights the efficacy of using zebrafish to study host-fungal interaction dynamics within burn wounds.

Engineering next generation vascularized organoids

Organoids are self-organizing 3D cell culture models that are valuable for studying the mechanisms underlying both development and disease in multiple species, particularly, in humans. These 3D engineered tissues can mimic the structure and function of human organs in vitro. Methods to generate organoids have substantially improved to better resemble, in various ways, their in vivo counterpart. One of the major limitations in current organoid models is the lack of a functional vascular compartment. Here we discuss methodological approaches to generating perfusable blood vessel networks in organoid systems. Inclusion of perfused vascular compartments markedly enhances the physiological relevance of organoid systems and is a critical step in the establishment of next generation, higher-complexity in vitro systems for use in developmental, clinical, and drug-development settings.

Aspirin reduces Ponatinib-induced cardiovascular toxic phenotypes and death in zebrafish

BACKGROUND

Ponatinib (Iclusig) is an oral tyrosine kinase BCR-ABL inhibitor for treating patients with Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL) and chronic myeloid leukemia (CML) who are resistant to the therapies with other tyrosine kinase inhibitors. However, adverse cardiovascular events caused by Ponatinib are a serious issue that affects patients' survival rates. Thus, it is necessary to search for candidate drugs to reduce the cardiovascular toxicity of Ponatinib.

PURPOSE

To investigate the effects of Aspirin on Ponatinib-induced cardiovascular toxicity in zebrafish.

METHODS

AB strain of wild type zebrafish (Danio rerio), Tg (cmlc2: GFP) transgenic zebrafish, and Tg (gata1: dsRed) transgenic zebrafish were used as in vivo models to assess survival, blood flow, cardiac morphology, and function. Thrombus formation was detected using O-dianisidine staining. The transcriptome of zebrafish larvae treated with Ponatinib was assessed using RNA sequencing.

RESULTS

Ponatinib not only reduced survival rate but also caused cardiovascular toxic events such as pericardial edema, abnormal heart structure, low heart rate, and thrombosis. In addition, whole-body transcriptome analysis showed that Ponatinib up-regulated the expression of cyclooxygenase-1 (COX-1). Compared with other antithrombotic drugs, a COX-1 inhibitor Aspirin more effectively reduced ponatinib-induced cardiovascular toxicity events and improved the survival rate of zebrafish larvae.

CONCLUSION

Our findings suggest that Aspirin exhibits the potential to reduce Ponatinib-induced cardiovascular toxicity.

Generation of Zebrafish Models of Human Retinitis Pigmentosa Diseases Using CRISPR/Cas9-Mediated Gene Editing System

Generating animal models can explore the role of new candidate genes in causing diseases and the pathogenicity of a specific mutation in the underlying genes. These animals can be used to identify new pharmaceutical or genetic therapeutic methods. In the present experiment, we developed a rpe65a knock out (KO) zebrafish as a retinitis pigmentosa (RP) disease model. Using the CRISPR/Cas9 system, the rpe65a gene was KO in zebrafish. Two specific single-guide RNAs (sgRNAs) were designed for the zebrafish rpe65a gene. SgRNAs were cloned into the DR274 plasmid and synthesized using in vitro transcription method. The efficiency of Ribonucleoprotein (synthesized sgRNA and recombinant Cas9) was evaluated by in vitro digestion experiment. Ribonucleoprotein complexes were microinjected into one to four-celled eggs of the TU zebrafish strain. The effectiveness of sgRNAs in KO the target gene was determined using the Heteroduplex mobility assay (HMA) and Sanger sequencing. Online software was used to determine the percent of mosaicism in the sequenced samples. By examining the sequences of the larvae that showed a mobility shift in the HMA method, the presence of indels in the binding region of sgRNAs was confirmed, so the zebrafish model for RP disease established. Zebrafish is an ideal animal model for the functional study of various diseases involving different genes and mutations and used for evaluating different therapeutic approaches in human diseases. This study presents the production of rpe65a gene KO zebrafish models using CRISPR/Cas9 technology. This model can be used in RP pathophysiology studies and preclinical gene therapy experiments.

The anti-angiogenic and anti-vasculogenic mimicry effects of GN25 in endothelial and glioma cells

BACKGROUND AND PURPOSE

Scientists have been exploring anti-angiogenic strategies to inhibit angiogenesis and prevent tumor growth. Vasculogenic mimicry (VM) in glioblastoma multiforme (GBM) poses a challenge, complicating anti-angiogenesis therapy. A novel drug, GN25 (3-[{1,4-dihydro-5,8-dimethoxy-1,4-dioxo-2-naphthalenyl}thio]-propanoic acid), can inhibit tumor formation. This study aims to investigate the microenvironmental effects and molecular mechanisms of GN25 in anti-angiogenesis and anti-VM.

EXPERIMENTAL APPROACH

MTT (3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide) assay was used to evaluate the cell viability of different concentrations of GN25 in human umbilical vein endothelial cells (HUVEC) and Uppsala 87 malignant glioma (U87MG) cells. Functional assays were used to investigate the effects of GN25 on angiogenesis-related processes, whereas gelatin zymography, enzyme-linked immunosorbent assays, and Western blotting were utilized to assess the influence on matrix metalloproteinase (MMP)-2 and vascular endothelial growth factor (VEGF) secretion and related signaling pathways.

KEY RESULTS

GN25 suppressed migration, wound healing, and tube formation in HUVECs and disrupted angiogenesis in a rat aorta ring and zebrafish embryo model. GN25 dose-dependently reduced phosphatidylinositol 3-kinase/AKT and inhibited MMP-2/VEGF secretion in HUVECs. In U87MG cells, GN25 inhibited migration, wound healing, and VM, accompanied by a decrease in MMP-2 and VEGF secretion. The results indicate that GN25 effectively inhibits angiogenesis and VM formation in HUVECs and U87MG cells without affecting preexisting vascular structures.

CONCLUSION AND IMPLICATIONS

This study elaborated GN25's potential as an anti-angiogenic agent by elucidating its inhibitory effects on classical angiogenesis. VM provides valuable insights for developing novel therapeutic strategies against tumor progression and angiogenesis-related diseases. These results indicate the potential of GN25 as a promising candidate for angiogenesis-related diseases.

Craters on the melanoma surface facilitate tumor-immune interactions and demonstrate pathologic response to checkpoint blockade in humans

Immunotherapy leads to cancer eradication despite the tumor's immunosuppressive environment. Here, we used extended long-term in-vivo imaging and high-resolution spatial transcriptomics of endogenous melanoma in zebrafish, and multiplex imaging of human melanoma, to identify domains that facilitate immune response during immunotherapy. We identified crater-shaped pockets at the margins of zebrafish and human melanoma, rich with beta-2 microglobulin (B2M) and antigen recognition molecules. The craters harbor the highest density of CD8+ T cells in the tumor. In zebrafish, CD8+ T cells formed prolonged interactions with melanoma cells within craters, characteristic of antigen recognition. Following immunostimulatory treatment, the craters enlarged and became the major site of activated CD8+ T cell accumulation and tumor killing that was B2M dependent. In humans, craters predicted immune response to ICB therapy, showing response better than high T cell infiltration. This marks craters as potential new diagnostic tool for immunotherapy success and targets to enhance ICB response.

Antifungal activity of synthetic xanthenone against fluconazole-resistant Candida auris and its mechanism of action

Candida auris, an emerging multidrug-resistant fungal pathogen discovered in Japan in 2009, poses a significant global health threat, with infections reported in about 25 countries. The escalation of drug-resistant strains underscores the urgent need for new treatment options. This study aimed to investigate the antifungal potential of 2,3,4,4a-tetrahydro-1H-xanthen-1-one (XA1) against C. auris, as well as its mechanism of action and toxic profile. The antifungal activity of XA1 was first evaluated by determining the minimum inhibitory concentration (MIC), time-kill kinetics and biofilm inhibition. In addition, structural changes, membrane permeability, reactive oxygen species (ROS) production, and in vitro and in vivo toxicity of C. auris after exposure to XA1 were investigated. The results indicated that XA1 exhibited an MIC of 50 μg/mL against C. auris, with time-kill kinetics highlighting its efficacy. Field emission scanning electron microscopy (FE-SEM) showed structural damage in XA1-treated cells, supported by increased membrane permeability leading to cell death. Furthermore, XA1 induced ROS production and significantly inhibited biofilm formation. Importantly, XA1 exhibited low cytotoxicity in human epidermal keratinocytes (HaCaT), with a cell viability of over 90 % at 6.25 μg/mL. In addition, an LD50 of 17.68 μg/mL was determined in zebrafish embryos 24 h post fertilization (hpf), with developmental delay observed at prolonged exposure at 6.25 μg/mL (48-96 hpf). These findings position XA1 as a promising candidate for further research and development of an effective antifungal agent.

The natural compound sinometumine E derived from Corydalis decumbens promotes angiogenesis by regulating HIF-1/ VEGF pathway in vivo and in vitro

The rhizome of Corydalis decumbens is a traditional Chinese medicine commonly utilized in the clinical treatment of acute ischemic stroke. Numerous phytochemical and biological investigations have demonstrated that protoberberine alkaloids from C. decumbens exhibit diverse pharmaceutical activities against various diseases. Sinometumine E (SE), a protoberberine alkaloid isolated from C. decumbens for the first time, is characterized by a complex 6/6/6/6/6/6 hexacyclic skeleton. In the current study, we investigated the protective effects of SE on endothelial cell injury and its angiogenesis effects in zebrafish. The results suggested that SE showed significant anti-ischemic effects on OGD/R-induced HBEC-5i and HUVECs cell ischemia/reperfusion injury model. Furthermore, it promoted angiogenesis in PTK787-induced, MPTP-induced, and atorvastatin-induced vessel injury models of zebrafish, while also suppressing hypoxia-induced locomotor impairment in zebrafish. Transcriptome sequencing analysis provided a sign that SE likely to promotes angiogenesis through the HIF-1/VEGF signaling pathway to exert anti-ischemic effects. Consistently, SE modulated several genes related to HIF-1/VEGF signal pathway, such as hif-1, vegf, vegfr-2, pi3k, erk, akt and plcγ. Molecular docking analysis revealed that VEGFR-2 exhibited high binding affinity with SE, and western blot analysis confirmed that SE treatment enhanced the expression of VEGFR-2. In conclusion, our study profiled the angiogenic activities of SE in vitro and in vivo. The key targets and related pathways involved in anti-ischemic effects of SE, shedding light on the pharmacodynamic components and mechanisms of Corydalis decumbens, and provides valuable insights for identifying effective substances for the treatment of ischemic stroke.

Akt is a mediator of artery specification during zebrafish development

The dorsal aorta (DA) is the first major blood vessel to develop in the embryonic cardiovascular system. Its formation is governed by a coordinated process involving the migration, specification, and arrangement of angioblasts into arterial and venous lineages, a process conserved across species. Although vascular endothelial growth factor a (VEGF-A) is known to drive DA specification and formation, the kinases involved in this process remain ambiguous. Thus, we investigated the role of protein kinase B (Akt) in zebrafish by generating a quadruple mutant (aktΔ/Δ), in which expression and activity of all Akt genes - akt1, -2, -3a and -3b - are strongly decreased. Live imaging of developing aktΔ/Δ DA uncovers early arteriovenous malformations. Single-cell RNA-sequencing analysis of aktΔ/Δ endothelial cells corroborates the impairment of arterial, yet not venous, cell specification. Notably, endothelial specific expression of ligand-independent activation of Notch or constitutively active Akt1 were sufficient to re-establish normal arterial specification in aktΔ/Δ. The Akt loss-of-function mutant unveils that Akt kinase can act upstream of Notch in arterial endothelial cells, and is involved in proper embryonic artery specification. This sheds light on cardiovascular development, revealing a mechanism behind congenital malformations.

Zebrafish Congenital Heart Disease Models: Opportunities and Challenges

Congenital heart defects (CHDs) are common human birth defects. Genetic mutations potentially cause the exhibition of various pathological phenotypes associated with CHDs, occurring alone or as part of certain syndromes. Zebrafish, a model organism with a strong molecular conservation similar to humans, is commonly used in studies on cardiovascular diseases owing to its advantageous features, such as a similarity to human electrophysiology, transparent embryos and larvae for observation, and suitability for forward and reverse genetics technology, to create various economical and easily controlled zebrafish CHD models. In this review, we outline the pros and cons of zebrafish CHD models created by genetic mutations associated with single defects and syndromes and the underlying pathogenic mechanism of CHDs discovered in these models. The challenges of zebrafish CHD models generated through gene editing are also discussed, since the cardiac phenotypes resulting from a single-candidate pathological gene mutation in zebrafish might not mirror the corresponding human phenotypes. The comprehensive review of these zebrafish CHD models will facilitate the understanding of the pathogenic mechanisms of CHDs and offer new opportunities for their treatments and intervention strategies.

Preliminary insight on diarylpentanoids as potential antimalarials: In silico, in vitro pLDH and in vivo zebrafish toxicity assessment

Malaria remains a major public health problem worldwide, including in Southeast Asia. Chemotherapeutic agents such as chloroquine (CQ) are effective, but problems with drug resistance and toxicity have necessitated a continuous search for new effective antimalarial agents. Here we report on a virtual screening of ∼300 diarylpentanoids and derivatives, in search of potential Plasmodium falciparum lactate dehydrogenase (PfLDH) inhibitors with acceptable drug-like properties. Several molecules with binding affinities comparable to CQ were chosen for in vitro validation of antimalarial efficacy. Among them, MS33A, MS33C and MS34C are the most promising against CQ-sensitive (3D7) with EC50 values of 1.6, 2.5 and 3.1 μM, respectively. Meanwhile, MS87 (EC50 of 1.85 μM) shown the most active against the CQ-resistant Gombak A strain, and MS33A and MS33C the most effective P. knowlesi inhibitors (EC50 of 3.6 and 5.1 μM, respectively). The in vitro cytotoxicity of selected diarylpentanoids (MS33A, MS33C, MS34C and MS87) was tested on Vero mammalian cells to evaluate parasite selectivity (SI), showing moderate to low cytotoxicity (CC50 > 82 μM). In addition, MS87 exhibited a high SI and the lowest resistance index (RI), suggesting that MS87 may exert effective parasite inhibition with low resistance potential in the CQ-resistant P. falciparum strain. Furthermore, the in vivo toxicity of the molecules on early embryonic development, the cardiovascular system, heart rate, motor activity and apoptosis were assessed in a zebrafish animal model. The overall results indicate the preliminary potential of diarylpentanoids, which need further investigation for their development as new antimalarial agents.

Analysis of vascular disruption in zebrafish embryos as an endpoint to predict developmental toxicity

Inhibition of angiogenesis is an important mode of action for the teratogenic effect of chemicals and drugs. There is a gap in the availability of simple, experimental screening models for the detection of angiogenesis inhibition. The zebrafish embryo represents an alternative test system which offers the complexity of developmental differentiation of an entire organism while allowing for small-scale and high-throughput screening. Here we present a novel automated imaging-based method to detect the inhibition of angiogenesis in early life stage zebrafish. Video subtraction was used to identify the location and number of functional intersegmental vessels according to the detection of moving blood cells. By exposing embryos to multiple tyrosine kinase inhibitors including SU4312, SU5416, Sorafenib, or PTK787, we confirmed that this method can detect concentration-dependent inhibition of angiogenesis. Parallel assessment of arterial and venal aorta ruled out a potential bias by impaired heart or blood cell development. In contrast, the histone deacetylase inhibitor valproic acid did not affect ISV formation supporting the specificity of the angiogenic effects. The new test method showed higher sensitivity, i.e. lower effect concentrations, relative to a fluorescent reporter gene strain (Tg(KDR:EGFP)) exposed to the same tyrosine kinase inhibitors indicating that functional effects due to altered tubulogenesis or blood transport can be detected before structural changes of the endothelium are visible by fluorescence imaging. Comparison of exposure windows indicated higher specificity for angiogenesis when exposure started at later embryonic stages (24 h post-fertilization). One of the test compounds was showing particularly high specificity for angiogenesis effects (SU4312) and was, therefore, suggested as a model compound for the identification of molecular markers of angiogenic disruption. Our findings establish video imaging in wild-type strains as viable, non-invasive, high-throughput method for the detection of chemical-induced angiogenic disruption in zebrafish embryos.

Calotropis procera: A double edged sword against glioblastoma, inhibiting glioblastoma cell line growth by targeting histone deacetylases (HDAC) and angiogenesis

Despite substantial investments in anti-glioblastoma (GBM) drug discovery over the last decade, progress is limited to preclinical stages, with clinical studies frequently encountering obstacles. Angiogenic and histone deacetylase inhibitors (HDACi) have shown profound results in pre-clinical studies. Investigating a multicomponent anti-cancer remedy that disrupts the tumor angiogenic blood vessels and simultaneously disrupts HDACs, while inducing minimal side effects, is critically needed. The crude extracts derived from medicinal plants serve as a renewable reservoir of anti-tumor drugs, exhibiting reduced toxicity compared to chemically synthesized formulations. Calotropis procera is a traditional medicinal plant, and its anticancer potential against many cancer cell lines has been reported, however its antiangiogenic and HDAC inhibitory action is largely unknown. The anticancer activity of methanol leaf extract of C. procera was tested in three types of human glioblastoma cell lines. Wild-type and transgenic zebrafish embryos were used to evaluate developmental toxicity and angiogenic activity. A human angiogenic antibody array was used to profile angiogenic proteins in the U251 GM cell line. A real-time reverse transcriptase polymerase chain reaction (RT PCR) assay was used to detect the differential expression of eleven HDAC genes in U251 cells treated with C. procera extract. The extract significantly reduced the proliferation of all three types of GBM cell lines and the cytotoxicity was found to be more pronounced in U251 GM cells, with an IC50 value of 2.63 ± 0.23 μg/ml, possibly by arresting the cell cycle at the G2/M transition. The extract did not exhibit toxic effects in zebrafish embryos, even at concentrations as high as 1000 μg/ml. The extract also inhibited angiogenic blood vessel formation in the transgenic zebrafish model in a dose-dependent manner. The results from the angiogenic antibody array have suggested novel angiogenesis targets that can be utilized to treat GBM. Real-time RT PCR analysis has shown that C. procrea extract caused an upregulation of HDAC5, 7, and 10, while the mRNA of HDAC1, 2, 3 and 8 (Class I HDACs), and HDAC4, 6, and 9 (Class II) were downregulated in U251 GM cells. The cytotoxicity of the C. procera extract on GBM cell lines could be due to its dual action by regulation of both tumor angiogenesis and histone deacetylases enzymes. Through this study, the C. procera leaf extract has been suggested as an effective remedy to treat GBM with minimal toxicity. In addition, various novel angiogenic and HDAC targets has been identified which could be helpful in designing better therapeutic strategies to manage glioblastoma multiforme in human patients.

Moderate Elevation of Homocysteine Induces Endothelial Dysfunction through Adaptive UPR Activation and Metabolic Rewiring

Elevation of the intermediate amino acid metabolite Homocysteine (Hcy) causes Hyperhomocysteinemia (HHcy), a metabolic disorder frequently associated with mutations in the methionine-cysteine metabolic cycle as well as with nutritional deficiency and aging. The previous literature suggests that HHcy is a strong risk factor for cardiovascular diseases. Severe HHcy is well-established to correlate with vascular pathologies primarily via endothelial cell death. Though moderate HHcy is more prevalent and associated with an increased risk of cardiovascular abnormalities in later part of life, its precise role in endothelial physiology is largely unknown. In this study, we report that moderate elevation of Hcy causes endothelial dysfunction through impairment of their migration and proliferation. We established that unlike severe elevation of Hcy, moderate HHcy is not associated with suppression of endothelial VEGF/VEGFR transcripts and ROS induction. We further showed that moderate HHcy induces a sub-lethal ER stress that causes defective endothelial migration through abnormal actin cytoskeletal remodeling. We also found that sub-lethal increase in Hcy causes endothelial proliferation defect by suppressing mitochondrial respiration and concomitantly increases glycolysis to compensate the consequential ATP loss and maintain overall energy homeostasis. Finally, analyzing a previously published microarray dataset, we confirmed that these hallmarks of moderate HHcy are conserved in adult endothelial cells as well. Thus, we identified adaptive UPR and metabolic rewiring as two key mechanistic signatures in moderate HHcy-associated endothelial dysfunction. As HHcy is clinically associated with enhanced vascular inflammation and hypercoagulability, identifying these mechanistic pathways may serve as future targets to regulate endothelial function and health.

Angiogenesis Assay for Live and Fixed Zebrafish Embryos/Larvae

Angiogenesis is the process of new blood vessel formation from preexisting vasculature. It is an integral component in normal embryonic development and tissue repair. Dysregulation of angiogenesis might lead to tissue ischemia (resulting from reduced blood vessel formation) or major diseases such as cancer (abnormal vascular growth). This makes angiogenesis an excellent area of research for cancer therapeutics, and various animal models including zebrafish are used to study blood vessel development. As most of the techniques used to study angiogenesis are complex and cumbersome, in this chapter, we provide two simple assays to study angiogenesis with live and fixed zebrafish embryos/larvae.

Vessel Metrics: A software tool for automated analysis of vascular structure in confocal imaging

Images contain a wealth of information that is often under analyzed in biological studies. Developmental models of vascular disease are a powerful way to quantify developmentally regulated vessel phenotypes to identify the roots of the disease process. We present vessel Metrics, a software tool specifically designed to analyze developmental vascular microscopy images that will expedite the analysis of vascular images and provide consistency between research groups. We developed a segmentation algorithm that robustly quantifies different image types, developmental stages, organisms, and disease models at a similar accuracy level to a human observer. We validate the algorithm on confocal, lightsheet, and two photon microscopy data in a zebrafish model expressing fluorescent protein in the endothelial nuclei. The tool accurately segments data taken by multiple scientists on varying microscopes. We validate vascular parameters such as vessel density, network length, and diameter, across developmental stages, genetic mutations, and drug treatments, and show a favorable comparison to other freely available software tools. Additionally, we validate the tool in a mouse model. Vessel Metrics reduces the time to analyze experimental results, improves repeatability within and between institutions, and expands the percentage of a given vascular network analyzable in experiments.

Using Electroporation to Improve and Accelerate Zebrafish Embryo Toxicity Testing

Zebrafish have emerged as a useful model for biomedical research and have been used in environmental toxicology studies. However, the presence of the chorion during the embryo stage limits cellular exposure to toxic elements and creates the possibility of a false-negative or reduced sensitivity in fish embryo toxicity testing (FET). This paper presents the use of electroporation as a technique to improve the delivery of toxic elements inside the chorion, increasing the exposure level of the toxins at an early embryo stage (<3 h post-fertilization). A custom-made electroporation device with the required electrical circuitry has been developed to position embryos between electrodes that provide electrical pulses to expedite the entry of molecules inside the chorion. The optimized parameters facilitate material entering into the chorion without affecting the survival rate of the embryos. The effectiveness of the electroporation system is demonstrated using Trypan blue dye and gold nanoparticles (AuNPs, 20-40 nm). Our results demonstrate the feasibility of controlling the concentration of dye and nanoparticles delivered inside the chorion by optimizing the electrical parameters, including pulse width, pulse number, and amplitude. Next, we tested silver nanoparticles (AgNPs, 10 nm), a commonly used toxin that can lower mortality, affect heart rate, and cause phenotypic defects. We found that electroporation of AgNPs reduces the exposure time required for toxicity testing from 4 days to hours. Electroporation for FET can provide rapid entry of potential toxins into zebrafish embryos, reducing the time required for toxicity testing and drug delivery experiments.

Homemade: building the structure of the neurogenic niche

Neural stem/progenitor cells live in an intricate cellular environment, the neurogenic niche, which supports their function and enables neurogenesis. The niche is made of a diversity of cell types, including neurons, glia and the vasculature, which are able to signal to and are structurally organised around neural stem/progenitor cells. While the focus has been on how individual cell types signal to and influence the behaviour of neural stem/progenitor cells, very little is actually known on how the niche is assembled during development from multiple cellular origins, and on the role of the resulting topology on these cells. This review proposes to draw a state-of-the art picture of this emerging field of research, with the aim to expose our knowledge on niche architecture and formation from different animal models (mouse, zebrafish and fruit fly). We will span its multiple aspects, from the existence and importance of local, adhesive interactions to the potential emergence of larger-scale topological properties through the careful assembly of diverse cellular and acellular components.

Identification of side effects of COVID-19 drug candidates on embryogenesis using an integrated zebrafish screening platform

Drug repurposing is an important strategy in COVID-19 treatment, but many clinically approved compounds have not been extensively studied in the context of embryogenesis, thus limiting their administration during pregnancy. Here we used the zebrafish embryo model organism to test the effects of 162 marketed drugs on cardiovascular development. Among the compounds used in the clinic for COVD-19 treatment, we found that Remdesivir led to reduced body size and heart functionality at clinically relevant doses. Ritonavir and Baricitinib showed reduced heart functionality and Molnupiravir and Baricitinib showed effects on embryo activity. Sabizabulin was highly toxic at concentrations only 5 times higher than Cmax and led to a mean mortality of 20% at Cmax. Furthermore, we tested if zebrafish could be used as a model to study inflammatory response in response to spike protein treatment and found that Remdesivir, Ritonavir, Molnupiravir, Baricitinib as well as Sabizabulin counteracted the inflammatory response related gene expression upon SARS-CoV-2 spike protein treatment. Our results show that the zebrafish allows to study immune-modulating properties of COVID-19 compounds and highlights the need to rule out secondary defects of compound treatment on embryogenesis. All results are available on a user friendly web-interface https://share.streamlit.io/alernst/covasc_dataapp/main/CoVasc_DataApp.py that provides a comprehensive overview of all observed phenotypic effects and allows personalized search on specific compounds or group of compounds. Furthermore, the presented platform can be expanded for rapid detection of developmental side effects of new compounds for treatment of COVID-19 and further viral infectious diseases.

A SIRT6 Inhibitor, Marine-Derived Pyrrole-Pyridinimidazole Derivative 8a, Suppresses Angiogenesis

Angiogenesis refers to the process of growing new blood vessels from pre-existing capillaries or post-capillary veins. This process plays a critical role in promoting tumorigenesis and metastasis. As a result, developing antiangiogenic agents has become an attractive strategy for tumor treatment. Sirtuin6 (SIRT6), a member of nicotinamide adenine (NAD+)-dependent histone deacetylases, regulates various biological processes, including metabolism, oxidative stress, angiogenesis, and DNA damage and repair. Some SIRT6 inhibitors have been identified, but the effects of SIRT6 inhibitors on anti-angiogenesis have not been reported. We have identified a pyrrole-pyridinimidazole derivative 8a as a highly effective inhibitor of SIRT6 and clarified its anti-pancreatic-cancer roles. This study investigated the antiangiogenic roles of 8a. We found that 8a was able to inhibit the migration and tube formation of HUVECs and downregulate the expression of angiogenesis-related proteins, including VEGF, HIF-1α, p-VEGFR2, and N-cadherin, and suppress the activation of AKT and ERK pathways. Additionally, 8a significantly blocked angiogenesis in intersegmental vessels in zebrafish embryos. Notably, in a pancreatic cancer xenograft mouse model, 8a down-regulated the expression of CD31, a marker protein of angiogenesis. These findings suggest that 8a could be a promising antiangiogenic and cancer therapeutic agent.

Direct differentiation of human pluripotent stem cells into vascular network along with supporting mural cells

During embryonic development, endothelial cells (ECs) undergo vasculogenesis to form a primitive plexus and assemble into networks comprised of mural cell-stabilized vessels with molecularly distinct artery and vein signatures. This organized vasculature is established prior to the initiation of blood flow and depends on a sequence of complex signaling events elucidated primarily in animal models, but less studied and understood in humans. Here, we have developed a simple vascular differentiation protocol for human pluripotent stem cells that generates ECs, pericytes, and smooth muscle cells simultaneously. When this protocol is applied in a 3D hydrogel, we demonstrate that it recapitulates the dynamic processes of early human vessel formation, including acquisition of distinct arterial and venous fates, resulting in a vasculogenesis angiogenesis model plexus (VAMP). The VAMP captures the major stages of vasculogenesis, angiogenesis, and vascular network formation and is a simple, rapid, scalable model system for studying early human vascular development in vitro.

Functional characterization of stap2b in zebrafish vascular development

The genetic control and signaling pathways of vascular development are not comprehensively understood. Transcription factors Islet2 (Isl2) and nr2f1b are critical for vascular growth in zebrafish, and further transcriptome analysis has revealed potential targets regulated by isl2/nr2f1b. In this study, we focused on the potential activation gene signal-transducing adaptor protein 2b (stap2b) and revealed a novel role of stap2b in vascular development. stap2b mRNA was expressed in developing vessels, suggesting stap2b plays a role in vascularization. Knocking down stap2b expression by morpholino injection or Crispr-Cas9-generated stap2b mutants caused vascular defects, suggesting a role played by stap2b in controlling the patterning of intersegmental vessels (ISVs) and the caudal vein plexus (CVP). The vessel abnormalities associated with stap2b deficiency were found to be due to dysregulated cell migration and proliferation. The decreased expression of vascular-specific markers in stap2b morphants was consistent with the vascular defects observed. In contrast, overexpression of stap2b enhanced the growth of ISVs and reversed the vessel defects in stap2b morphants. These data suggest that stap2b is necessary and sufficient to promote vascular development. Finally, we examined the interaction between stap2b and multiple signaling. We showed that stap2b regulated ISV growth through the JAK-STAT pathway. Moreover, we found that stap2b was regulated by Notch signaling to control ISV growth, and stap2b interacted with bone morphogenetic protein signaling to contribute to CVP formation. Altogether, we demonstrated that stap2b acts downstream of the isl2/nr2f1b pathway to play a pivotal role in vascular development via interaction with multiple signaling pathways.

Mechanisms of skin vascular maturation and maintenance captured by longitudinal imaging of live mice

A functional network of blood vessels is essential for organ growth and homeostasis, yet how the vasculature matures and maintains homeostasis remains elusive in live mice. By longitudinally tracking the same neonatal endothelial cells (ECs) over days to weeks, we found that capillary plexus expansion is driven by vessel regression to optimize network perfusion. Neonatal ECs rearrange positions to evenly distribute throughout the developing plexus and become positionally stable in adulthood. Upon local ablation, adult ECs survive through a plasmalemmal self-repair response, while neonatal ECs are predisposed to die. Furthermore, adult ECs reactivate migration to assist vessel repair. Global ablation reveals coordinated maintenance of the adult vascular architecture that allows for eventual network recovery. Lastly, neonatal remodeling and adult maintenance of the skin vascular plexus are orchestrated by temporally restricted, neonatal VEGFR2 signaling. Our work sheds light on fundamental mechanisms that underlie both vascular maturation and adult homeostasis in vivo.

Exposure to the herbicide fluridone induces cardiovascular toxicity in early developmental stages of zebrafish

Fluridone is a systemic herbicide used to control a range of invasive aquatic plants in irrigation systems, lake, and reservoirs. Since aquatic herbicides are more likely to have a hazardous impact on ecosystems than terrestrially applied herbicides, a risk assessment is needed to determine whether to expand or limit their use. The aim of this study was to investigate the developmental toxicity of fluridone using zebrafish. Diverse toxicological results were observed for the sub-lethal endpoints, including lack of hatching, reduced heartbeat and disturbed blood circulation through dysmorphic heart, and edema formation. Abnormal apoptosis was observed in the brain and yolk sac of fluridone-exposed larvae. A computational analysis was used to predict chemical properties in non-target organisms and revealed that fluridone was highly relevant in the cardiovascular system. Double transgenic zebrafish (fli1a:EGFP;cmlc2:dsRed) were used to evaluate the effects of fluridone on the cardiovascular system during embryonic development. Ectopic growth of sub-intestinal vessels and sprouting angiogenesis in the hindbrain region were highly inhibited. Additionally, essential genes involved in the VEGF signaling and heart development were differentially expressed in dose-dependent manner. Collectively, our toxicological findings in fluridone exposure highlight defects in the cardiovascular development causing embryonic lethality that could damage aquatic communities and natural ecosystems.

Zebrafish as a Model of Cardiac Pathology and Toxicity: Spotlight on Uremic Toxins

Chronic kidney disease (CKD) is an increasing health care problem. About 10% of the general population is affected by CKD, representing the sixth cause of death in the world. Cardiovascular events are the main mortality cause in CKD, with a cardiovascular risk 10 times higher in these patients than the rate observed in healthy subjects. The gradual decline of the kidney leads to the accumulation of uremic solutes with a negative effect on every organ, especially on the cardiovascular system. Mammalian models, sharing structural and functional similarities with humans, have been widely used to study cardiovascular disease mechanisms and test new therapies, but many of them are rather expensive and difficult to manipulate. Over the last few decades, zebrafish has become a powerful non-mammalian model to study alterations associated with human disease. The high conservation of gene function, low cost, small size, rapid growth, and easiness of genetic manipulation are just some of the features of this experimental model. More specifically, embryonic cardiac development and physiological responses to exposure to numerous toxin substances are similar to those observed in mammals, making zebrafish an ideal model to study cardiac development, toxicity, and cardiovascular disease.

Antiangiogenic potential of Lepista nuda extract suppressing MAPK/p38 signaling-mediated developmental angiogenesis in zebrafish and HUVECs

The medicinal properties of natural/edible plant products and their use are popular in traditional practice owing to their nutritional contents with little to no side effects. Lepista nuda (L. nuda), an edible mushroom (Clitocybe nuda, commonly known as blewit), has attracted researchers to evaluate its contents and the mechanism of its activities. In the current study, we focused on evaluating the antiangiogenic effects of L. nuda water extract on zebrafish development and in vitro human umbilical vein endothelial cell (HUVEC) tube formation. Bioactive components such as ergothioneine, eritadenine, and adenosine were identified and quantified by HPLC analysis. The L. nuda extract showed antiangiogenic properties and inhibited intersegmental vessel (ISV), caudal vein plexus (CVP), hyaloid vessel (HV), and subintestinal vessel (SIV) development in Tg (fli1: EGFP) zebrafish embryos. The expression of angiogenesis-related genes (vegfaa, kdrl, vegfba, flt1, kdr) was affected following L. nuda extract treatment. L. nuda extract attenuated in vitro HUVEC tube formation, migration, and invasion. Furthermore, inhibition of MAPK/p38 signaling and depletion of proangiogenic genes, including growth factors (fgf, ang2, and vegfa); primary and accessory receptors (tie2, vegfr2, and eng); MMPs (mmp1 and mmp2); and cytokines (il-1α, il-1β, il-6, and tnf-α) was observed in HUVECs following L. nuda treatment. An in vivo zebrafish xenograft assay showed that L. nuda extract inhibited HuCCT1 cell-induced SIV sprouting in HuCCT1-injected embryos. Collectively, the results suggest that L. nuda could be a potential inhibitor of angiogenesis limiting cancer progression.

Analysis of Vascular Morphogenesis in Zebrafish

Analysis of cardiovascular development in zebrafish embryos has become a major driver of vascular research in recent years. Imaging-based analyses have allowed the discovery or verification of morphologically distinct processes and mechanisms of, e.g., endothelial cell migration, angiogenic sprouting, tip or stalk cell behavior, and vessel anastomosis. In this chapter, we describe the techniques and tools used for confocal imaging of zebrafish endothelial development in combination with general experimental approaches for molecular dissection of involved signaling pathways.

Macrophage NFATC2 mediates angiogenic signaling during mycobacterial infection

During mycobacterial infections, pathogenic mycobacteria manipulate both host immune and stromal cells to establish and maintain a productive infection. In humans, non-human primates, and zebrafish models of infection, pathogenic mycobacteria produce and modify the specialized lipid trehalose 6,6'-dimycolate (TDM) in the bacterial cell envelope to drive host angiogenesis toward the site of forming granulomas, leading to enhanced bacterial growth. Here, we use the zebrafish-Mycobacterium marinum infection model to define the signaling basis of the host angiogenic response. Through intravital imaging and cell-restricted peptide-mediated inhibition, we identify macrophage-specific activation of NFAT signaling as essential to TDM-mediated angiogenesis in vivo. Exposure of cultured human cells to Mycobacterium tuberculosis results in robust induction of VEGFA, which is dependent on a signaling pathway downstream of host TDM detection and culminates in NFATC2 activation. As granuloma-associated angiogenesis is known to serve bacterial-beneficial roles, these findings identify potential host targets to improve tuberculosis disease outcomes.

Characterization of glyphosate-induced cardiovascular toxicity and apoptosis in zebrafish

Glyphosate, the most widely used herbicide, presents new hazards to human health. The developmental toxicity of glyphosate, especially its cardiovascular toxicity, needs to be closely monitored. To understand how glyphosate affects development, we performed toxicity tests on zebrafish embryos that were continuously exposed to glyphosate. The results indicated that glyphosate affected the overall development of zebrafish embryos, including mortality, hatching abnormalities, and decreased body length. At the same time, zebrafish embryos exposed to glyphosate exhibited cardiac malformations, including enlarged chambers, thinned ventricular walls, and rhythm disturbances. In addition, defective intersegmental vasculature occurred after glyphosate exposure, indicating impaired angiogenesis. Mechanistically, apoptosis clustered in the heart and vascular regions and levels of ATP and apoptosis-related genes including caspase-3, caspase-9, bax, and bcl-2 were altered. In summary, the data showed that cardiovascular toxicity caused by glyphosate exposure may be related to apoptosis. Our study provides evidence for a link between glyphosate exposure and cardiovascular developmental toxicity. This raises concerns regarding the health risks of the glyphosate.

Spiromesifen contributes vascular developmental toxicity via disrupting endothelial cell proliferation and migration in zebrafish embryos

Spiromesifen (SPF) is a specific contact pesticide, which has been widely used to control the growth of sucking insects like mites and whiteflies on crops. Although its residues in crops and effects on organisms has been extensively reported, its impact on the vasculature is still not being reported. In the present study, using human umbilical vein endothelial cells (HUVECs) and zebrafish embryos, we investigated the effects of SPF on blood vessel development and its mechanism of action. SPF exposure triggered abnormal blood vessel development, including vascular deletions and malformations, inhibition of CCV remodeling, and decrease of SIV areas. SPF exposure also obstructed the migration of endothelial cell from caudal hematopoietic tissue in zebrafish embryos. SPF damaged cytoskeleton, caused cell cycle arrest, inhibited the viability and migration of HUVECs. In addition, SPF also inhibited the expression of the VEGF/VEGFR pathway-related genes (hif1a, vegfa, flt1, and kdrl), cell cycle-related genes (ccnd1, ccne1, cdk2, and pcna), and Rho/ROCK pathway-related genes (itgb1, rho, rock, mlc-1, and vim-1). Taken together, SPF may inhibit the proliferation and migration of vascular endothelial cells through disturbing cytoskeleton via the Rho/ ROCK pathway, resulting in vascular malformation. Our study contributes to potential insight into the mechanism of SPF toxicity in angiocardiopathy.

The N-Substituted-4-Methylbenzenesulphonyl Hydrazone Inhibits Angiogenesis in Zebrafish Tg(fli1: EGFP) Model

One of the most important therapies of malignant neoplasms, which are the second cause of death worldwide, is focused on the inhibition of pathological angiogenesis within the tumor. Therefore, the searching for the efficacious and relatively inexpensive small-molecule inhibitors of this process is essential. In this research, the anti-angiogenic potential of N-substituted-4-methylbenzenesulphonyl hydrazone, possessing antiproliferative activity against cancer cells, was tested. For this purpose, an intersegmental vessel (ISV) angiogenesis assay was performed using 6 hpf (hours post fertilization), 12 hpf and 24 hpf embryos of zebrafish transgenic strain, Tg(fli1: EGFP). They were incubated with different concentrations of tested molecule and after 24 h the development of intersegmental vessels of the trunk was analysed. In turn, the acute toxicity study in the zebrafish model was mainly conducted on strain AB, using the OECD-approved and recommended fish embryo acute toxicity test (FET) procedure. The results showed the moderate toxicity of N-[(3-chloro-4-methoxyphenyl)methylidene]-4-methylbenzenesulphonohydrazide in above-mentioned model with the LC₅₀ value calculated at 23.04 mg/L. Moreover, newly synthesized molecule demonstrated the anti-angiogenic potential proved in Tg(fli1: EGFP) zebrafish model, which may be promising for the therapy of neoplastic tumors as well as other diseases related to pathological angiogenesis, such as age-related macular degeneration and diabetic retinopathy.

Capturing membrane trafficking events during 3D angiogenic development in vitro

OBJECTIVES

Vesicular trafficking dictates protein localization, functional activity, and half-life, providing a critically important regulatory step in tissue development; however, there is little information detailing endothelial-specific trafficking signatures. This is due, in part, to limitations in visualizing trafficking events in endothelial tissues. Our aim in this investigation was to explore the use of a 3-dimensional (3D) in vitro sprouting model to image endothelial membrane trafficking events.

METHODS

Endothelial cells were challenged to grow sprouts in a fibrin bead assay. Thereafter, spouts were transfected with fluorescent proteins and stained for various cell markers. Sprouts were then imaged for trafficking events using live and fixed-cell microscopy.

RESULTS

Our results demonstrate that fibrin bead sprouts have a strong apicobasal polarity marked by apical localization of proteins moesin and podocalyxin. Comparison of trafficking mediators Rab27a and Rab35 between 3D sprouts and 2D culture showed that vesicular carriers can be imaged at high resolution, exhibiting proper membrane polarity solely in 3D sprouts. Lastly, we imaged exocytic events of von Willebrand Factor and demonstrated a distinct imaging advantage for monitoring secretion events in 3D sprouts as compared with 2D culture.

CONCLUSIONS

Our results establish that the fibrin bead sprouting assay is well-suited for imaging of trafficking events during angiogenic growth.

Involvement of transmembrane protein 184a during angiogenesis in zebrafish embryos

Angiogenesis, the outgrowth of new blood vessels from existing vasculature, is critical during development, tissue formation, and wound healing. In response to vascular endothelial growth factors (VEGFs), endothelial cells are activated to proliferate and move towards the signal, extending the vessel. These events are directed by VEGF-VEGF receptor (Vegfr2) signal transduction, which in turn is modulated by heparan sulfate proteoglycans (HSPGs). HSPGs are glycoproteins covalently attached to HS glycosaminoglycan chains. Transmembrane protein 184a (Tmem184a) has been recently identified as a heparin receptor, which is believed to bind heparan sulfate chains in vivo. Therefore, Tmem184a has the potential to fine-tune interactions between VEGF and HS, modulating Vegfr2-dependent angiogenesis. The function of Tmem184a has been investigated in the regenerating zebrafish caudal fin, but its role has yet to be evaluated during developmental angiogenesis. Here we provide insights into how Tmem184a contributes to the proper formation of the vasculature in zebrafish embryos. First, we find that knockdown of Tmem184a causes a reduction in the number of intact intersegmental vessels (ISVs) in the zebrafish embryo. This phenotype mimics that of vegfr2b knockout mutants, which have previously been shown to exhibit severe defects in ISV development. We then test the importance of HS interactions by removing the binding domain within the Tmem184a protein, which has a negative effect on angiogenesis. Tmem184a is found to act synergistically with Vegfr2b, indicating that the two gene products function in a common pathway to modulate angiogenesis. Moreover, we find that knockdown of Tmem184a leads to an increase in endothelial cell proliferation but a decrease in the amount of VE-cadherin present. Together, these findings suggest that Tmem184a is necessary for ISVs to organize into mature, complete vessels.

A systematic comparison of anti-angiogenesis efficacy and cardiotoxicity of receptor tyrosine kinase inhibitors in zebrafish model

Pathological angiogenesis is fundamental to progression of cancerous tumors and blinding eye diseases. Anti-angiogenic receptor tyrosine kinase inhibitors (TKIs) are in broad use for the treatment of these diseases. With more and more TKIs available, it is a challenge to make an optimal choice. It remains unclear whether TKIs demonstrate similar anti-angiogenesis activities in different tissues. Many TKIs have shown varying degrees of toxic effects that should also be considered in clinical use. This study investigates the anti-angiogenic effects of 13 FDA-approved TKIs on the intersegmental vessels (ISVs), subintestinal vessels (SIVs) and retinal vasculature in zebrafish embryos. The results show that vascular endothelial growth factor receptor TKIs (VEGFR-TKIs) exhibit anti-angiogenic abilities similarly on ISVs and SIVs, and their efficacy is consistent with their IC₅₀ values against VEGFR2. In addition, VEGFR-TKIs selectively induces the apoptosis of endothelial cells in immature vessels. Among all TKIs tested, axitinib demonstrates a strong inhibition on retinal neovascularization at a low dose that do not strongly affect ISVs and SIVs, supporting its potential application for retinal diseases. Zebrafish embryos demonstrate cardiotoxicity after VEGFR-TKIs treatment, and ponatinib and sorafenib show a narrow therapeutic window, suggesting that these two drugs may need to be dosed more carefully in patients. We propose that zebrafish is an ideal model for studying in vivo antiangiogenic efficacy and cardiotoxicity of TKIs.

In vivo dissection of Rhoa function in vascular development using zebrafish

The small monomeric GTPase RHOA acts as a master regulator of signal transduction cascades by activating effectors of cellular signaling, including the Rho-associated protein kinases ROCK1/2. Previous in vitro cell culture studies suggest that RHOA can regulate many critical aspects of vascular endothelial cell (EC) biology, including focal adhesion, stress fiber formation, and angiogenesis. However, the specific in vivo roles of RHOA during vascular development and homeostasis are still not well understood. In this study, we examine the in vivo functions of RHOA in regulating vascular development and integrity in zebrafish. We use zebrafish RHOA-ortholog (rhoaa) mutants, transgenic embryos expressing wild type, dominant negative, or constitutively active forms of rhoaa in ECs, pharmacological inhibitors of RHOA and ROCK1/2, and Rock1 and Rock2a/b dgRNP-injected zebrafish embryos to study the in vivo consequences of RHOA gain- and loss-of-function in the vascular endothelium. Our findings document roles for RHOA in vascular integrity, developmental angiogenesis, and vascular morphogenesis in vivo, showing that either too much or too little RHOA activity leads to vascular dysfunction.

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.