Chemical modulation of receptor signaling inhibits regenerative angiogenesis in adult zebrafish

Ethyl butyrate inhibits caudal fin regeneration in adult zebrafish by disrupting extracellular matrix remodeling

Wound healing and tissue regeneration are influenced by a variety of factors. Adverse lifestyle habits, such as excessive alcohol consumption, delay wound healing and increase the risk of secondary infections. Ethyl butyrate is a common food additive widely used to enhance the aroma of alcoholic beverages. This additive is generally considered harmless to human health in both industrial and domestic settings. However, the ecotoxicity and its effects on wound healing have not been elucidated. In this study, we used zebrafish as the experimental animal, and the caudal fins were amputated to explore the effects of ethyl butyrate on wound healing and tissue regeneration. The effect of ethyl butyrate on blastema and bone regeneration and its impact on the transcriptional levels of regeneration-related genes and inflammation-related genes were evaluated. RNA-seq was conducted to determine the differentially expressed genes (DEGs) between the treatment and the control groups. KEGG and GO analysis was conducted to explore the functions of DEGs. Significantly enriched GO terms and KEGG pathways were identified to explore the molecular mechanism underlying the inhibition of zebrafish caudal fin regeneration by ethyl butyrate. The results demonstrated that ethyl butyrate significantly inhibited the regeneration of zebrafish caudal fins, including blastema and bone regeneration. Ethyl butyrate exposure significantly downregulated the expression of genes associated with bone and blastema regeneration and inflammation response. KEGG and GO functional analyses revealed that the DEGs were associated with significant enrichment of extracellular matrix-receptor interactions. Ethyl butyrate treatment downregulated the expression of most extracellular matrix-related genes. These findings indicate that ethyl butyrate potentially modulates pathways associated with the structure, adhesion, modification, and degradation of the extracellular matrix, thereby disrupting extracellular matrix remodeling, inhibiting wound inflammation, impairing blastema and bone regeneration and ultimately hindering caudal fin regeneration. In summary, the findings demonstrate that ethyl butyrate disrupts extracellular matrix remodeling and inhibits the regeneration of zebrafish caudal fins. These results provide valuable insights into the rational use of ethyl butyrate and further investigation of wound healing mechanisms.

Disruption of the creb3l1 gene causes defects in caudal fin regeneration and patterning in zebrafish Danio rerio

BACKGROUND

The gene cAMP-Responsive Element Binding protein 3-like-1 (CREB3L1) has been implicated in bone development in mice, with CREB3L1 knock-out mice exhibiting fragile bones, and in humans, with CREB3L1 mutations linked to osteogenesis imperfecta. However, the mechanism through which Creb3l1 regulates bone development is not fully understood.

RESULTS

To probe the role of Creb3l1 in organismal physiology, we used CRISPR-Cas9 genome editing to generate a Danio rerio (zebrafish) model of Creb3l1 deficiency. In contrast to mammalian phenotypes, the Creb3l1 deficient fish do not display abnormalities in osteogenesis, except for a decrease in the bifurcation pattern of caudal fin. Both, skeletal morphology and overall bone density appear normal in the mutant fish. However, the regeneration of caudal fin postamputation is significantly affected, with decreased overall regenerate and mineralized bone area. Moreover, the mutant fish exhibit a severe patterning defect during regeneration, with a significant decrease in bifurcation complexity of the fin rays and distalization of the bifurcation sites. Analysis of genes implicated in bone development showed aberrant patterning of shha and ptch2 in Creb3l1 deficient fish, linking Creb3l1 with Sonic Hedgehog signaling during fin regeneration.

CONCLUSIONS

Our results uncover a novel role for Creb3l1 in regulating tissue growth and patterning during regeneration.

Apela promotes blood vessel regeneration and remodeling in zebrafish

In contrast to adult mammals, zebrafish display a high capacity to heal injuries and repair damage to various organs. One of the earliest responses to injury in adult zebrafish is revascularization, followed by tissue morphogenesis. Tissue vascularization entails the formation of a blood vessel plexus that remodels into arteries and veins. The mechanisms that coordinate these processes during vessel regeneration are poorly understood. Hence, investigating and identifying the factors that promote revascularization and vessel remodeling have great therapeutic potential. Here, we revealed that fin vessel remodeling critically depends on Apela peptide. We found that Apela selectively accumulated in newly formed zebrafish fin tissue and vessels. The temporal expression of Apela, Apln, and their receptor Aplnr is different during the regenerative process. While morpholino-mediated knockdown of Apela (Mo-Apela) prevented vessel remodeling, exogenous Apela peptide mediated plexus repression and the development of arteries in regenerated fins. In contrast, Apela enhanced subintestinal venous plexus formation (SIVP). The use of sunitinib completely inhibited vascular plexus formation in zebrafish, which was not prevented by exogenous application. Furthermore, Apela regulates the expression of vessel remolding-related genes including VWF, IGFPB3, ESM1, VEGFR2, Apln, and Aplnr, thereby linking Apela to the vascular plexus factor network as generated by the STRING online database. Together, our findings reveal a new role for Apela in vessel regeneration and remodeling in fin zebrafish and provide a framework for further understanding the cellular and molecular mechanisms involved in vessel regeneration.

Exposure to Intermittent Environmental Hypoxia Promotes Vascular Remodeling through Angiogenesis in the Liver of Largemouth Bass (Micropterus salmoides)

In this study, we explored the effects of 4 weeks of intermittent hypoxic exposure (IHE) on liver angiogenesis and related regulatory mechanisms in largemouth bass (Micropterus salmoides). The results indicated that the O2 tension for loss of equilibrium (LOE) decreased from 1.17 to 0.66 mg/L after 4 weeks of IHE. Meanwhile, the red blood cell (RBC) and hemoglobin concentrations significantly increased during IHE. Our investigation also found that the observed increase in angiogenesis was correlated with a high expression of related regulators, such as Jagged, phosphoinositide-3-kinase (PI3K), and mitogen-activated protein kinase (MAPK). After 4 weeks of IHE, the overexpression of factors related to angiogenesis processes mediated by HIF-independent pathways (such as nuclear factor kappa-B (NF-κB), NADPH oxidase 1 (NOX1), and interleukin 8 (IL8)) was correlated with the accumulation of lactic acid (LA) in the liver. The addition of cabozantinib, a specific inhibitor of VEGFR2, blocked the phosphorylation of VEGFR2 and downregulated the expression of downstream angiogenesis regulators in largemouth bass hepatocytes exposed to hypoxia for 4 h. These results suggested that IHE promoted liver vascular remodeling by the regulation of angiogenesis factors, presenting a potential mechanism for the improvement of hypoxia tolerance in largemouth bass.

Understanding the process of angiogenesis in regenerating earthworm

Developing blood vessels from the existing vasculature is vital for the growth of the organism, as well as for systematic wound healing and the repair process. In this study, we investigated the role of angiogenesis during the regeneration process in the earthworm, Eudrilus eugeniae, animal model. Briefly, the morphological examination of blood vessels in juvenile and mature worms is documented, along with the development of new blood vessels in regenerating blastema. However, in vivo and in vitro experiments with juvenile worms revealed that geraniol retards blastemal regeneration growth with undeveloped blood vessels, as compared to the control. The results of qRT-PCR, western blotting, and immunohistochemistry confirmed a reduced expression of VEGFR2 and WNT5A in the day 3 regenerating blastema of geraniol-treated worms, as compared to the control. We conclude that geraniol acts as a potent natural inhibitor of angiogenesis, thereby retarding the regeneration process in earthworms. In addition, for studying angiogenesis and screening effective angiogenesis inhibitors as drug candidates, the earthworm is an ambient animal model system.

Temporally and regionally distinct morphogenetic processes govern zebrafish caudal fin blood vessel network expansion

Blood vessels form elaborate networks that depend on tissue-specific signalling pathways and anatomical structures to guide their growth. However, it is not clear which morphogenetic principles organize the stepwise assembly of the vasculature. We therefore performed a longitudinal analysis of zebrafish caudal fin vascular assembly, revealing the existence of temporally and spatially distinct morphogenetic processes. Initially, vein-derived endothelial cells (ECs) generated arteries in a reiterative process requiring vascular endothelial growth factor (Vegf), Notch and cxcr4a signalling. Subsequently, veins produced veins in more proximal fin regions, transforming pre-existing artery-vein loops into a three-vessel pattern consisting of an artery and two veins. A distinct set of vascular plexuses formed at the base of the fin. They differed in their diameter, flow magnitude and marker gene expression. At later stages, intussusceptive angiogenesis occurred from veins in distal fin regions. In proximal fin regions, we observed new vein sprouts crossing the inter-ray tissue through sprouting angiogenesis. Together, our results reveal a surprising diversity among the mechanisms generating the mature fin vasculature and suggest that these might be driven by separate local cues.

Promoting Angiogenesis Effect and Molecular Mechanism of Isopropyl Caffeate (KYZ), a Novel Metabolism-Derived Candidate Drug, Based on Integrated Network Pharmacology and Transgenic Zebrafish Models

AIM OF THE STUDY

Ischemic diseases have a huge impact on people's health, which can cause blood supply blockage or restriction in specific tissues. Researchers must develop novel drugs with great efficacy and low toxicity for the prevention and treatment of such diseases. Isopropyl caffeic acid (KYZ) was one of the metabolites of caffeic acid in vivo. This study is to explore the protective effect and mechanism of KYZ on ischemic disease from the perspective of angiogenesis in vivo and in vitro, providing support for the treatment of ischemic diseases and the discovery of a new candidate drug.

METHODS

The network pharmacology and molecular docking were used to predict the targets of KYZ. In addition, the effects of KYZ on damaged and normal blood vessels were evaluated using the Tg (fli1: EGFP) transgenic zebrafish. The HUVECs model was used to study the effects of KYZ on proliferation, migration, and tube formation. The same dosage of caffeic acid (CA) was also administered in vitro and in vivo at the same time to assess the pharmacodynamic difference between the two compounds. Western Blot and ELISA methods were used to detect the expression of related target proteins.

RESULTS

The result from the network pharmacology indicated that the targets of KYZ were related to angiogenesis. It was also found that KYZ could repair the vascular damage induced by the PTK787 and promote the growth of subintestinal vessels in normal zebrafish. The result also indicated that KYZ's angiogenic ability is better than the precursor compound CA. In HUVECs, KYZ could promote cell proliferation, migration, and tube formation. Further mechanistic study suggested that the KYZ could induce the release of VEGF factor in HUVECs, up-regulate the expression of VEGFR2, and activate the PI3K/AKT and MEK/ERK signaling pathways.

CONCLUSIONS

These data show that KYZ may promote angiogenesis through VEGF, PI3K/AKT, and MEK/ERK signaling pathways, suggesting that KYZ exhibited great potential in the treatment of ischemic cardio-cerebrovascular diseases.

Osteoblasts pattern endothelium and somatosensory axons during zebrafish caudal fin organogenesis

Skeletal elements frequently associate with vasculature and somatosensory nerves, which regulate bone development and homeostasis. However, the deep, internal location of bones in many vertebrates has limited in vivo exploration of the neurovascular-bone relationship. Here, we use the zebrafish caudal fin, an optically accessible organ formed of repeating bony ray skeletal units, to determine the cellular relationship between nerves, bones and endothelium. In adult zebrafish, we establish the presence of somatosensory axons running through the inside of the bony fin rays, juxtaposed with osteoblasts on the inner hemiray surface. During development we show that the caudal fin progresses through sequential stages of endothelial plexus formation, bony ray addition, ray innervation and endothelial remodeling. Surprisingly, the initial stages of fin morphogenesis proceed normally in animals lacking either fin endothelium or somatosensory nerves. Instead, we find that sp7+ osteoblasts are required for endothelial remodeling and somatosensory axon innervation in the developing fin. Overall, this study demonstrates that the proximal neurovascular-bone relationship in the adult caudal fin is established during fin organogenesis and suggests that ray-associated osteoblasts pattern axons and endothelium.

Microscopical observations on the regenerating tail of tsinling dwarf skink (Scincella tsinlingensis)

Although the key steps of tail regeneration in lizards are well understood, further investigations involving skinks can provide the field of regeneration research with additional information. In order to characterize the cytoarchitecture of tail regeneration in Scincella tsinlingensis, an endemic species in China, its histological events and growth trends are investigated. The rate of tail regeneration varies with the season: it proceeds faster in summer and autumn than it does in winter and spring. Tail regeneration of S. tsinlingensis is summarized as wound healing, blastema formation, cell differentiation and tail growth, which can be subdivided into seven stages. Wound healing following tail loss, begins with an obvious outgrowth undergoing re-epithelialization. Numerous proliferating mesenchymal-like cells aggregate near the distal end of the severed spinal cord to form the blastema. The expanding blastema is invaded by blood vessels, nerves and ependyma. A cartilaginous skeleton is formed around the ependymal tube and the muscle starts to differentiate. The keratinization of epidermis coincides with scale formation. Pigmentation eventually occurs in the regenerated tail. Tail regeneration in S. tsinlingensis is an epimorphic kind of regeneration that is also known as blastema-mediated. Structure and composition of the regenerated tail, including its cytoarchitecture, represent a conserved pattern of regeneration also known from other lizards.

Modulation of VEGFA Signaling During Heart Regeneration in Zebrafish

Over the last decades, myocardial infarction and heart failure have accounted every year for millions of deaths worldwide. After a coronary occlusion, the lack of blood supply to downstream muscle leads to cell death and scarring. To date, several pro-angiogenic factors have been tested to stimulate reperfusion of the affected myocardium, VEGFA being one of the most extensively studied. Given the unsuccessful outcomes of clinical trials, understanding how cardiac revascularization takes place in models with endogenous regenerative capacity holds the key to devising more efficient therapies. Here, we summarize the main findings on VEGFA's role during cardiac repair and regeneration, with a particular focus on zebrafish as a regenerative model. Moreover, we provide a comprehensive overview of available tools to modulate Vegfa expression and action in zebrafish regeneration studies. Understanding the role of Vegfa during zebrafish heart regeneration may help devise efficient therapies and circumvent current limitations in using VEGFA for therapeutic angiogenesis approaches.

A comparative perspective on lung and gill regeneration

The ability to continuously grow and regenerate the gills throughout life is a remarkable property of fish and amphibians. Considering that gill regeneration was first described over one century ago, it is surprising that the underlying mechanisms of cell and tissue replacement in the gills remain poorly understood. By contrast, the mammalian lung is a largely quiescent organ in adults but is capable of facultative regeneration following injury. In the course of the past decade, it has been recognized that lungs contain a population of stem or progenitor cells with an extensive ability to restore tissue; however, despite recent advances in regenerative biology of the lung, the signaling pathways that underlie regeneration are poorly understood. In this Review, we discuss the common evolutionary and embryological origins shared by gills and mammalian lungs. These are evident in homologies in tissue structure, cell populations, cellular function and genetic pathways. An integration of the literature on gill and lung regeneration in vertebrates is presented using a comparative approach in order to outline the challenges that remain in these areas, and to highlight the importance of using aquatic vertebrates as model organisms. The study of gill regeneration in fish and amphibians, which have a high regenerative potential and for which genetic tools are widely available, represents a unique opportunity to uncover common signaling mechanisms that may be important for regeneration of respiratory organs in all vertebrates. This may lead to new advances in tissue repair following lung disease.

Low doses of ionizing radiation enhance angiogenesis and consequently accelerate post-embryonic development but not regeneration in zebrafish

Low doses of ionizing radiation (LDIR) activate endothelial cells inducing angiogenesis. In zebrafish, LDIR induce vessel formation in the sub-intestinal vessels during post-embryonic development and enhance the inter-ray vessel density in adult fin regeneration. Since angiogenesis is a crucial process involved in both post-embryonic development and regeneration, herein we aimed to understand whether LDIR accelerate these physiological conditions. Our data show that LDIR upregulate the gene expression of several pro-angiogenic molecules, such as flt1, kdr, angpt2a, tgfb2, fgf2 and cyr61in sorted endothelial cells from zebrafish larvae and this effect was abrogated by using a vascular endothelial growth factor receptor (VEGFR)-2 tyrosine kinase inhibitor. Irradiated zebrafish present normal indicators of developmental progress but, importantly LDIR accelerate post-embryonic development in a VEGFR-2 dependent signaling. Furthermore, our data show that LDIR do not accelerate regeneration after caudal fin amputation and the gene expression of the early stages markers of regeneration are not modulated by LDIR. Even though regeneration is considered as a recapitulation of embryonic development and LDIR induce angiogenesis in both conditions, our findings show that LDIR accelerate post-embryonic development but not regeneration. This highlights the importance of the physiological context for a specific phenotype promoted by LDIR.

Parallels between wound healing, epimorphic regeneration and solid tumors

Striking similarities between wound healing, epimorphic regeneration and the progression of solid tumors have been uncovered by recent studies. In this Review, we discuss systemic effects of tumorigenesis that are now being appreciated in epimorphic regeneration, including genetic, cellular and metabolic heterogeneity, changes in circulating factors, and the complex roles of immune cells and immune modulation at systemic and local levels. We suggest that certain mechanisms enabling regeneration may be co-opted by cancer to promote growth at primary and metastatic sites. Finally, we advocate that working with a unified approach could complement research in both fields.

Tanshinol borneol ester, a novel synthetic small molecule angiogenesis stimulator inspired by botanical formulations for angina pectoris

BACKGROUND AND PURPOSE

Tanshinol borneol ester (DBZ) is a novel synthetic compound derived from Dantonic^® , a botanical drug approved in 26 countries outside the United States for angina pectoris and currently undergoing FDA Phase III clinical trial. Here, we investigated the angiogenic effects of (S)-DBZ and (R)-DBZ isomers in vitro and in vivo.

EXPERIMENTAL APPROACH

A network pharmacology approach was used to predict molecular targets of DBZ. The effects of DBZ isomers on proliferation, migration, and tube formation of human endothelial cells were assessed. For in vivo approaches, the transgenic Tg (vegfr2:GFP) zebrafish and C57BL/6 mouse Matrigel plug models were used. ELISA and western blots were used to quantitate the release and expression of relevant target molecules and signalling pathways.

KEY RESULTS

DBZ produced a biphasic modulation on proliferation and migration of three types of human endothelial cells. Both DBZ isomers induced tube formation in Matrigel assay and a 12-day co-culture model in vitro. Moreover, DBZ promoted Matrigel neovascularization in mice and partially reversed the vascular disruption in zebrafish induced by PTK787. Mechanistically, DBZ enhanced the cellular levels of VEGF, VEGFR2, and MMP-9, as well as activating Akt and MAPK signalling in endothelial cells. Selective inhibition of PI3K and MEK significantly attenuated its angiogenic effects.

CONCLUSIONS AND IMPLICATIONS

These data reveal, for the first time, that DBZ promotes multiple key steps of angiogenesis, at least in part through Akt and MAPK signalling pathways, and suggest it may be potentially developed further for treating myocardial infarction and other cardiovascular diseases.

A Reliable Preclinical Model to Study the Impact of Cigarette Smoke in Development and Disease

The World Health Organization has estimated that, worldwide, cigarette smoking has caused more than 100 million deaths in the last century, a number that is expected to increase in the future. Understanding cigarette smoke toxicity is key for research and development of proper public health policies. The current challenge is to establish a reliable preclinical model to evaluate the effects of cigarette smoke. In this work, we describe a simple method that allows for quantifying the toxic effects of cigarette smoke using zebrafish. Here, viability of larvae and adult fish, as well as the effects of cigarette smoke extracts on vascular development and tissue regeneration, can be easily assayed. © 2019 by John Wiley & Sons, Inc.

Sinus Membrane Elevation with Heterologous Cortical Lamina: A Randomized Study of a New Surgical Technique for Maxillary Sinus Floor Augmentation without Bone Graft

Background: The aim of this randomized controlled clinical trial was to compare the efficacy of two different techniques for maxillary sinus augmentation using a lateral window approach: Heterologous cortical lamina without any grafting material versus 100% collagenated granular collagen porcine bone. Methods: Twenty-three healthy patients with not relevant past medical history (14 women and 9 men, non-smokers, mean age 52 years, range 48–65 years) were included. In Group I, the sinus was filled with collagen porcine bone (Geno-os, OsteoBiol, Turin, Italy) and a collagen membrane (Evolution, OsteoBiol, Turin, Italy) was used to close the lateral window of the sinus. In Group II, the sinus was treated with heterologous cortical lamina only (Lamina, OsteoBiol, Turin, Italy). Results: There was a statistically significant difference in the surgical time required to complete the augmentation procedures: 18.3 ± 2.1 min for lamina treated sites versus 12.5 ± 3.1 min for porcine bone treated sites. In Group I, the mean volume of the graft was 3101 ± 321 mm³ in the immediate postoperative examination (5–7 days), while after a six-month healing period it was 2716.7 ± 432 mm³. Conclusion: This study demonstrates that the use of heterologous cortical lamina is a valid technique for the mechanical support of sinus membranes resulting in only bone tissue formation and not mixed with the graft. The graft material was biocompatible and not completely resorbed after six months, although the remains were integrated into the bone.

A Novel In Vivo Model to Study Impaired Tissue Regeneration Mediated by Cigarette Smoke

Cigarette smoke is associated with several pathologies including chronic respiratory diseases and cancer. In addition, exposure to cigarette smoke is correlated with impaired wound healing, where a significant decrease in the regenerative capacity of smokers is well documented and broadly considered a negative risk factor after trauma or surgery. So far, some in vitro and in vivo models have been described to study how exposure to cigarette smoke diminishes the regenerative potential in different organisms. However, although useful, many of these models are difficult and expensive to implement and do not allow high-throughput screening approaches. In order to establish a reliable and accessible model, we have evaluated the effects of cigarette smoke extract (CSE) on zebrafish development and regeneration. In this work, zebrafish embryos and larvae were exposed to low doses of aqueous CSE showing severe developmental abnormalities in a dose-dependent manner. Furthermore, when adult zebrafish were subjected to caudal fin amputation, we observed a significant decrease in the regenerative capacity of animals exposed to CSE. The effect was exacerbated in male and aged fish compared to female or young organisms. The establishment of a zebrafish model to assess the consequences of cigarette smoke and its effects on animal physiology could provide a new tool to study the underlying mechanisms involved in impaired tissue regeneration, and aid the development of novel approaches to treat complications associated with cigarette smoke toxicity.

Fish Scales Dictate the Pattern of Adult Skin Innervation and Vascularization

As animals mature from embryonic to adult stages, the skin grows and acquires specialized appendages, like hairs, feathers, and scales. How cutaneous blood vessels and sensory axons adapt to these dramatic changes is poorly understood. By characterizing skin maturation in zebrafish, we discovered that sensory axons are delivered to the adult epidermis in organized nerves patterned by features in bony scales. These nerves associate with blood vessels and osteoblasts above scales. Osteoblasts create paths in scales that independently guide nerves and blood vessels during both development and regeneration. By preventing scale regeneration and examining mutants lacking scales, we found that scales recruit, organize, and polarize axons and blood vessels to evenly distribute them in the skin. These studies uncover mechanisms for achieving comprehensive innervation and vascularization of the adult skin and suggest that scales coordinate a metamorphosis-like transformation of the skin with sensory axon and vascular remodeling.

Three-Dimensional Architecture and Mechanical Properties of Bovine Bone Mixed with Autologous Platelet Liquid, Blood, or Physiological Water: An In Vitro Study

In recent years, several techniques and material options have been investigated and developed for bone defect repair and regeneration. The progress in studies of composite graft materials and autologous platelet-derived growth factors for bone regeneration in dentistry and their biological and biomechanical properties has improved clinical strategies and results. The aim of this study was to evaluate the three-dimensional architecture and mechanical properties of three different combinations of composite bovine graft, adding autologous platelet liquid (APL), blood, or physiological water. One experimental group for each combination of biomaterials was created. In particular, in Group I, the bovine graft was mixed with APL; in Group II, it was mixed with blood, and in Group III, the biomaterial graft was combined with physiological water. Then, the composite biomaterials were evaluated by scanning electron microscopy (SEM), and a compression-loading test was conducted. The evaluation showed a statistical significance (p < 0.01) of the elastic regime of deformation resistance, in which the combination of APL with bone graft resulted in an 875% increase in the mechanical resistance. The protocol of APL mixed with bovine bone graft produced a composite sticky graft block that was capable of increasing the mechanical properties in order to improve its clinical use in the treatment of the maxillary bone defects.

Comparative regenerative mechanisms across different mammalian tissues

Stimulating regeneration of complex tissues and organs after injury to effect complete structural and functional repair, is an attractive therapeutic option that would revolutionize clinical medicine. Compared to many metazoan phyla that show extraordinary regenerative capacity, which in some instances persists throughout life, regeneration in mammalians, particularly humans, is limited or absent. Here we consider recent insights in the elucidation of molecular mechanisms of regeneration that have come from studies of tissue homeostasis and injury repair in mammalian tissues that span the spectrum from little or no self-renewal, to those showing active cell turnover throughout life. These studies highlight the diversity of factors that constrain regeneration, including immune responses, extracellular matrix composition, age, injury type, physiological adaptation, and angiogenic and neurogenic capacity. Despite these constraints, much progress has been made in elucidating key molecular mechanisms that may provide therapeutic targets for the development of future regenerative therapies, as well as previously unidentified developmental paradigms and windows-of-opportunity for improved regenerative repair.

Widening control of fin inter-rays in zebrafish and inferences about actinopterygian fins

The amputation of a teleost fin rapidly triggers an intricate maze of hierarchically regulated signalling processes which ultimately reconstruct the diverse tissues of the appendage. Whereas the generation of the fin pattern along the proximodistal axis brings with it several well-known developmental regulators, the mechanisms by which the fin widens along its dorsoventral axis remain poorly understood. Utilizing the zebrafish as an experimental model of fin regeneration and studying more than 1000 actinopterygian species, we hypothesized a connection between specific inter-ray regulatory mechanisms and the morphological variability of inter-ray membranes found in nature. To tackle these issues, both cellular and molecular approaches have been adopted and our results suggest the existence of two distinguishable inter-ray areas in the zebrafish caudal fin, a marginal and a central region. The present work associates the activity of the cell membrane potassium channel kcnk5b, the fibroblast growth factor receptor 1 and the sonic hedgehog pathway to the control of several cell functions involved in inter-ray wound healing or dorsoventral regeneration of the zebrafish caudal fin. This ray-dependent regulation controls cell migration, cell-type patterning and gene expression. The possibility that modifications of these mechanisms are responsible for phenotypic variations found in euteleostean species, is discussed.

Optimal occlusion uniformly partitions red blood cells fluxes within a microvascular network

In animals, gas exchange between blood and tissues occurs in narrow vessels, whose diameter is comparable to that of a red blood cell. Red blood cells must deform to squeeze through these narrow vessels, transiently blocking or occluding the vessels they pass through. Although the dynamics of vessel occlusion have been studied extensively, it remains an open question why microvessels need to be so narrow. We study occlusive dynamics within a model microvascular network: the embryonic zebrafish trunk. We show that pressure feedbacks created when red blood cells enter the finest vessels of the trunk act together to uniformly partition red blood cells through the microvasculature. Using mathematical models as well as direct observation, we show that these occlusive feedbacks are tuned throughout the trunk network to prevent the vessels closest to the heart from short-circuiting the network. Thus occlusion is linked with another open question of microvascular function: how are red blood cells delivered at the same rate to each micro-vessel? Our analysis shows that tuning of occlusive feedbacks increase the total dissipation within the network by a factor of 11, showing that uniformity of flows rather than minimization of transport costs may be prioritized by the microvascular network.

Arterial trees shuttle red blood cells from the heart to billions of capillaries distributed throughout the body. These trees have long been thought to be organized to minimize transport costs. Yet red blood cells are tightly squeezed within the finest vessels, meaning that these vessels account for as much as half of the total transport costs within the arterial network. It is unclear why vessel diameters and red blood cell diameters are so closely matched in a network that is presumed to optimize transport. Here, we use mathematical modeling and direct observations of red blood cell movements in embryonic zebrafish to show that occlusive feedbacks—the pressure feedbacks that alter the flows into a vessel when it is nearly blocked by a red blood cell—can optimally distribute red blood cells through microvessels. In addition to revealing an adaptive function for the matching of vessel and red blood cell diameters, this work shows that uniformity of red blood cell fluxes can be a unifying principle for understanding the elegant hydraulic organization of microvascular networks.

Fishing anti(lymph)angiogenic drugs with zebrafish

Zebrafish, an amenable small teleost fish with a complex mammal-like circulatory system, is being increasingly used for drug screening and toxicity studies. It combines the biological complexity of in vivo models with a higher-throughput screening capability compared with other available animal models. Externally growing, transparent embryos, displaying well-defined blood and lymphatic vessels, allow the inexpensive, rapid, and automatable evaluation of drug candidates that are able to inhibit neovascularisation. Here, we briefly review zebrafish as a model for the screening of anti(lymph)angiogenic drugs, with emphasis on the advantages and limitations of the different zebrafish-based in vivo assays.

Inhibition of Vascular Endothelial Growth Factor Receptor Decreases Regenerative Angiogenesis in Axolotls

Angiogenesis is crucial for tissue growth and repair in mammals, and is chiefly regulated by vascular endothelial growth factor (VEGF) signaling. We evaluated the effect of chemical inhibition of VEGF receptor signaling in animals with superior regenerative ability, axolotl salamanders, to determine the impact on vascularization and regenerative outgrowth. Following tail amputation, treated animals (100 nM PTK787) and controls were examined microscopically and measured over the month-long period of regeneration. Treatment with VEGFR inhibitor decreased regenerative angiogenesis; drug-treated animals had lower vascular densities in the regenerating tail than untreated animals. This decrease in neovascularization, however, was not associated with a decrease in regenerative outgrowth or with morphological abnormalities in the regrown tail. Avascular but otherwise anatomically normal regenerative outgrowth over 1 mm beyond the amputation plane was observed. The results suggest that in this highly regenerative species, significant early tissue regeneration is possible in the absence of a well-developed vasculature. This research sets the groundwork for establishing a system for the chemical manipulation of angiogenesis within the highly regenerative axolotl model, contributing to a better understanding of the role of the microvasculature within strongly proliferative yet well-regulated environments. Anat Rec, 300:2273-2280, 2017. © 2017 Wiley Periodicals, Inc.

Novel Heparin Receptor Transmembrane Protein 184a Regulates Angiogenesis in the Adult Zebrafish Caudal Fin

Transmembrane protein 184A (TMEM184A) was recently identified as the heparin receptor in vascular cells. Heparin binds specifically to TMEM184A and induces anti-proliferative signaling in vitro. Though it is highly conserved, the physiological function of TMEM184A remains unknown. The objective of this study was to investigate the expression and effects on vascular regeneration of TMEM184A using the adult zebrafish regenerating caudal fin as an in vivo model. Here, we show that Tmem184a is expressed in vascular endothelial cells (ECs) of mature and regenerating zebrafish fins. Transient morpholino (MO)-mediated knockdown of Tmem184a using two validated MOs results in tangled regenerating vessels that do not grow outward and limit normal overall fin regeneration. A significant increase in EC proliferation is observed. Consistent with in vitro work with tissue culture vascular cells, heparin has the opposite effect and decreases EC proliferation which also hinders overall fin regeneration. Collectively, our study suggests that Tmem184a is a novel regulator of angiogenesis.

Oncometabolite succinate promotes angiogenesis by upregulating VEGF expression through GPR91-mediated STAT3 and ERK activation

Altered cellular metabolism is now generally acknowledged as a hallmark of cancer cells, the resultant abnormal oncometabolites cause both metabolic and nonmetabolic dysregulation and potential transformation to malignancy. A subset of cancers have been found to be associated with mutations in succinate dehydrogenase genes which result in the accumulation of succinate. However, the function of succinate in tumorigenesis remains unclear. In the present study, we aim to investigate the role of oncometabolite succinate in tumor angiogenesis. Our data demonstrated the accumulation of markedly elevated succinate in gastric cancer tissues compared with that in paracancerous tissues. Moreover, succinate was able to increase the chemotactic motility, tube-like structure formation and proliferation of primary human umbilical vascular endothelial cells (pHUVECs) in vitro, as well as promoting the blood vessel formation in transgenic zebrafish. Our mechanistic studies reveal that succinate upregulates vascular endothelial growth factor (VEGF) expression by activation of signal transducer and activator of transcription 3 (STAT3) and extracellular regulated kinase (ERK)1/2 via its receptor GPR91 in a HIF-1α independent mechanism. Taken together, these data indicate an important role of the succinate-GPR91 axis in tumor angiogenesis, which may enable development of a novel therapeutic strategy that targets cancer metabolism.

Theoretical and practical aspects of using fetal fibroblasts for skin regeneration

Cutaneous wounding in late-gestational fetal or postnatal humans results in scar formation without any skin appendages. Early or mid- gestational skin healing in humans is characterized by the absence of scaring in a process resembling regeneration. Tremendous cellular and molecular mechanisms contribute to this distinction, and fibroblasts play critical roles in scar or scarless wound healing. This review discussed the different repair mechanisms involved in wound healing of fibroblasts at different developmental stages and further confirmed that fetal fibroblast transplantation resulted in reduced scar healing in vivo. We also discussed the possible problem in fetal fibroblast transplantation for wound repair. We proposed the use of small molecules to improve the regenerative potential of repairing cells in the wound given that remodeling of the wound microenvironment into a regenerative microenvironment in adults might improve skin regeneration.

Antiangiogenic effects of oridonin

Background

Oridonin, the major terpene found in Rabdosia rubescens (Henmsl.) Hara, is widely used as a dietary supplement and therapeutic drug. Oridonin has been proven to possess good anti-tumour activity, but little is known about its effect on angiogenesis. The aim of this study was to investigate the antiangiogenic effects of oridonin in vivo and in vitro and prove that oridonin anti-tumour activity is based on suppressing angiogenesis.

Methods

In vitro, the antiangiogenesis effect was studied by proliferation, apoptosis, migration, invasion, and tube formation experiments on human umbilical vascular endothelial cells (HUVECs). In vivo, using the Tg (fli1: GFP) zebrafish model, the embryonic vasculogenesis and postnatal regeneration were evaluated. The vascular endothelial growth factor (VEGF) signalling pathway gene expressions were assessed by reverse transcription-polymerase chain reaction (RT-PCR). Furthermore, the inhibition effects on tumour growth and metastasis were observed using a xenograft zebrafish tumour model and xenograft nude mouse tumour model. Angiogenesis was assayed by immunostaining with cluster of differentiation 31. Importantly, the proteins were identified as being differentially expressed in an in vivo model by two-dimensional electrophoresis-mass spectrometry (2D–MS) and western blot (WB).

Results

The results indicated that oridonin inhibited HUVEC proliferation, migration, invasion, and tube formation and induced cell apoptosis. Oridonin inhibited zebrafish angiogenesis during embryonic development and tail fin regeneration. RT-PCR showed that oridonin decreased the VEGFA, VEGFR2, and VEGFR3 expressions in zebrafish, while the TP53 expression increased. Moreover, oridonin had strong effects on tumour growth and metastasis in vivo. 2D–MS identified a total of 50 proteins differentially expressed (17 up-expressed, 28 down-expressed). Lastly, WB showed that Claudin 1, Claudin 4, and Claudin 7 were closely related to tumour growth and metastasis.

Conclusion

This study demonstrated that oridonin could inhibit tumour growth and metastasis, which mainly based on oridonin antiangiogenic effects. Claudin 1, Claudin 4, and Claudin 7 were the main contributors to the mechanism.

High-throughput identification of small molecules that affect human embryonic vascular development

Birth defects, which are in part caused by exposure to environmental chemicals and pharmaceutical drugs, affect 1 in every 33 babies born in the United States each year. The current standard to screen drugs that affect embryonic development is based on prenatal animal testing; however, this approach yields low-throughput and limited mechanistic information regarding the biological pathways and potential adverse consequences in humans. To develop a screening platform for molecules that affect human embryonic development based on endothelial cells (ECs) derived from human pluripotent stem cells, we differentiated human pluripotent stem cells into embryonic ECs and induced their maturation under arterial flow conditions. These cells were then used to screen compounds that specifically affect embryonic vasculature. Using this platform, we have identified two compounds that have higher inhibitory effect in embryonic than postnatal ECs. One of them was fluphenazine (an antipsychotic), which inhibits calmodulin kinase II. The other compound was pyrrolopyrimidine (an antiinflammatory agent), which inhibits vascular endothelial growth factor receptor 2 (VEGFR2), decreases EC viability, induces an inflammatory response, and disrupts preformed vascular networks. The vascular effect of the pyrrolopyrimidine was further validated in prenatal vs. adult mouse ECs and in embryonic and adult zebrafish. We developed a platform based on human pluripotent stem cell-derived ECs for drug screening, which may open new avenues of research for the study and modulation of embryonic vasculature.

Blood vessel formation during tail regeneration in the leopard gecko (Eublepharis macularius): The blastema is not avascular

Unique among amniotes, many lizards are able to self-detach (autotomize) their tail and then regenerate a replacement. Tail regeneration involves the formation of a blastema, an accumulation of proliferating cells at the site of autotomy. Over time, cells of the blastema give rise to most of the tissues in the replacement tail. In non-amniotes capable of regenerating (such as urodeles and some teleost fish), the blastema is reported to be essentially avascular until tissue differentiation takes place. For tail regenerating lizards less is known. Here, we investigate neovascularization during tail regeneration in the leopard gecko (Eublepharis macularius). We demonstrate that the gecko tail blastema is not an avascular structure. Beginning with the onset of regenerative outgrowth, structurally mature (mural cell supported) blood vessels are found within the blastema. Although the pattern of blood vessel distribution in the regenerate tail differs from that of the original, a hierarchical network is established, with vessels of varying luminal diameters and wall thicknesses. Using immunostaining, we determine that blastema outgrowth and tissue differentiation is characterized by a dynamic interplay between the pro-angiogenic protein vascular endothelial growth factor (VEGF) and the anti-angiogenic protein thrombospondin-1 (TSP-1). VEGF-expression is initially widespread, but diminishes as tissues differentiate. In contrast, TSP-1 expression is initially restricted but becomes more abundant as VEGF-expression wanes. We predict that variation in the neovascular response observed between different regeneration-competent species likely relates to the volume of the blastema. J. Morphol. 278:380-389, 2017. © 2017 Wiley Periodicals, Inc.

Axitinib blocks Wnt/β-catenin signaling and directs asymmetric cell division in cancer

Oncogenic mutations of the Wnt (wingless)/β-catenin pathway are frequently observed in major cancer types. Thus far, however, no therapeutic agent targeting Wnt/β-catenin signaling is available for clinical use. Here we demonstrate that axitinib, a clinically approved drug, strikingly blocks Wnt/β-catenin signaling in cancer cells, zebrafish, and Apc(min/+) mice. Notably, axitinib dramatically induces Wnt asymmetry and nonrandom DNA segregation in cancer cells by promoting nuclear β-catenin degradation independent of the GSK3β (glycogen synthase kinase3β)/APC (adenomatous polyposis coli) complex. Using a DARTS (drug affinity-responsive target stability) assay coupled to 2D-DIGE (2D difference in gel electrophoresis) and mass spectrometry, we have identified the E3 ubiquitin ligase SHPRH (SNF2, histone-linker, PHD and RING finger domain-containing helicase) as the direct target of axitinib in blocking Wnt/β-catenin signaling. Treatment with axitinib stabilizes SHPRH and thereby increases the ubiquitination and degradation of β-catenin. Our findings suggest a previously unreported mechanism of nuclear β-catenin regulation and indicate that axitinib, a clinically approved drug, would provide therapeutic benefits for cancer patients with aberrant nuclear β-catenin activation.

Dental implants combined with sinus augmentation: What is the merit of bone grafting? A systematic review

PURPOSE

The aim of the present study was to systematically assess the current evidence on the effect of nongrafted compared to graft-assisted maxillary sinus floor elevation on implant survival/failure, endosinus bone gain, crestal bone loss, and bone density around dental implants.

MATERIALS AND METHODS

MEDLINE-PubMed, Cochrane-CENTRAL, and EMBASE databases were searched up to November 2015 for randomized controlled trials (RCTs) and controlled clinical trials-(CCTs), evaluating dental implants placed in combination with maxillary sinus elevation without and with bone grafting. Implant survival/failure served as the primary outcome, whereas endosinus bone gain, crestal bone loss, and bone density around dental implants were secondary outcomes. To assess possible bias, the Cochrane risk of bias tool was used. Data were extracted and a meta-analysis performed where appropriate.

RESULTS

Independent screening of 3180 papers resulted in six eligible experiments. Heterogeneity was observed among experiments. One experiment showed low, three unclear, and two a high risk of bias. The assessed outcomes showed no significant long-term differences between groups.

CONCLUSION

Within the limit of the current systematic review, nongrafted maxillary sinus floor elevation seems to be characterized by new bone formation and high implant survival rate comparable to bone-graft-assisted maxillary sinus floor augmentation. Further long-term studies are needed before definitive conclusions can be made.

Identification of apoptosis and macrophage migration events in paraquat-induced oxidative stress using a zebrafish model

AIMS

Paraquat (PQ) is a pesticide highly toxic to human beings, and a well-known trigger of oxidative stress. Although several animal models of PQ poisoning have been developed, some disadvantages limit their application in vivo. A zebrafish model was used in the present study to better define mechanisms of oxidative stress injury induced by PQ.

MAIN METHODS

The toxicity of PQ was evaluated in the AB strain of zebrafish, and apoptosis was assessed by acridine orange staining. Macrophage migration was identified using the TG (zlyz:EGFP) transgenic strain, and angiogenesis was observed using the fli1a-EGFP casper strain. Following the validation of gene changes by zebrafish-based in vivo quantitative real-time PCR, network analysis was performed using the Ingenuity Pathway Analysis software.

KEY FINDINGS

We first established the LC50 of PQ in the zebrafish model, and then found that robust oxidative stress and antioxidant genes were activated after PQ exposure. Moreover, apoptosis and distinct macrophage activation and migration were identified for the first time in PQ-exposed zebrafish. Utilizing this model, both extrinsic and intrinsic pathways involved in PQ-induced apoptosis were elucidated. We further demonstrated that macrophage migration was specifically induced by PQ, and that Rho family members and JNK-MMP13 signaling participated in this process.

SIGNIFICANCE

Zebrafish is a promising tool for investigating the mechanisms of oxidative stress injury induced by PQ, and for screening effective anti-oxidant drugs.

Zebrafish as an Emerging Model Organism to Study Angiogenesis in Development and Regeneration

Angiogenesis is the process through which new blood vessels are formed from preexisting ones and plays a critical role in several conditions including embryonic development, tissue repair and disease. Moreover, enhanced therapeutic angiogenesis is a major goal in the field of regenerative medicine and efficient vascularization of artificial tissues and organs is one of the main hindrances in the implementation of tissue engineering approaches, while, on the other hand, inhibition of angiogenesis is a key therapeutic target to inhibit for instance tumor growth. During the last decades, the understanding of cellular and molecular mechanisms involved in this process has been matter of intense research. In this regard, several in vitro and in vivo models have been established to visualize and study migration of endothelial progenitor cells, formation of endothelial tubules and the generation of new vascular networks, while assessing the conditions and treatments that either promote or inhibit such processes. In this review, we address and compare the most commonly used experimental models to study angiogenesis in vitro and in vivo. In particular, we focus on the implementation of the zebrafish (Danio rerio) as a model to study angiogenesis and discuss the advantages and not yet explored possibilities of its use as model organism.

Zebrafish Caudal Fin Angiogenesis Assay-Advanced Quantitative Assessment Including 3-Way Correlative Microscopy

Background

Researchers evaluating angiomodulating compounds as a part of scientific projects or pre-clinical studies are often confronted with limitations of applied animal models. The rough and insufficient early-stage compound assessment without reliable quantification of the vascular response counts, at least partially, to the low transition rate to clinics.

Objective

To establish an advanced, rapid and cost-effective angiogenesis assay for the precise and sensitive assessment of angiomodulating compounds using zebrafish caudal fin regeneration. It should provide information regarding the angiogenic mechanisms involved and should include qualitative and quantitative data of drug effects in a non-biased and time-efficient way.

Approach & Results

Basic vascular parameters (total regenerated area, vascular projection area, contour length, vessel area density) were extracted from in vivo fluorescence microscopy images using a stereological approach. Skeletonization of the vasculature by our custom-made software Skelios provided additional parameters including “graph energy” and “distance to farthest node”. The latter gave important insights into the complexity, connectivity and maturation status of the regenerating vascular network. The employment of a reference point (vascular parameters prior amputation) is unique for the model and crucial for a proper assessment. Additionally, the assay provides exceptional possibilities for correlative microscopy by combining in vivo-imaging and morphological investigation of the area of interest. The 3-way correlative microscopy links the dynamic changes in vivo with their structural substrate at the subcellular level.

Conclusions

The improved zebrafish fin regeneration model with advanced quantitative analysis and optional 3-way correlative morphology is a promising in vivo angiogenesis assay, well-suitable for basic research and preclinical investigations.

Inhibition of poly-ADP ribose polymerase enzyme activity prevents hyperglycemia-induced impairment of angiogenesis during wound healing

We previously reported a zebrafish model of type I diabetes mellitus (DM) that can be used to study the hyperglycemic (HG) and metabolic memory (MM) states within the same fish. Clinically, MM is defined as the persistence of diabetic complications even after glycemic control is pharmacologically achieved. In our zebrafish model, MM occurs following β-cell regeneration, which returns fish to euglycemia. During HG, fish acquire tissue deficits reflective of the complications seen in patients with DM and these deficits persist after fish return to euglycemia (MM). The unifying mechanism for the induction of diabetic complications involves a cascade of events that is initiated by the HG stimulation of poly-ADP ribose polymerase enzyme (Parp) activity. Additionally, recent evidence shows that the HG induction of Parp activity stimulates changes in epigenetic mechanisms that correlate with the MM state and the persistence of complications. Here we report that wound-induced angiogenesis is impaired in DM and remains impaired when fish return to a euglycemic state. Additionally, inhibition of Parp activity prevented the HG-induced wound angiogenesis deficiency observed. This approach can identify molecular targets that will provide potential new avenues for therapeutic discovery as angiogenesis imbalances are associated with all HG-damaged tissues.

The art of fin regeneration in zebrafish

The zebrafish fin provides a valuable model to study the epimorphic type of regeneration, whereby the amputated part of the appendage is nearly perfectly replaced. To accomplish fin regeneration, two reciprocally interacting domains need to be established at the injury site, namely a wound epithelium and a blastema. The wound epithelium provides a supporting niche for the blastema, which contains mesenchyme-derived progenitor cells for the regenerate. The fate of blastemal daughter cells depends on their relative position with respect to the fin margin. The apical compartment of the outgrowth maintains its undifferentiated character, whereas the proximal descendants of the blastema progressively switch from the proliferation program to the morphogenesis program. A delicate balance between self-renewal and differentiation has to be continuously adjusted during the course of regeneration. This review summarizes the current knowledge about the cellular and molecular mechanisms of blastema formation, and discusses several studies related to the regulation of growth and morphogenesis during fin regeneration. A wide range of canonical signaling pathways has been implicated during the establishment and maintenance of the blastema. Epigenetic mechanisms play a crucial role in the regulation of cellular plasticity during the transition between differentiation states. Ion fluxes, gap-junctional communication and protein phosphatase activity have been shown to coordinate proliferation and tissue patterning in the caudal fin. The identification of the downstream targets of the fin regeneration signals and the discovery of mechanisms integrating the variety of input pathways represent exciting future aims in this fascinating field of research.

Notch signaling regulates venous arterialization during zebrafish fin regeneration

To protect against blood pressure, a mature artery is supported by mural cells which include vascular smooth muscle cells and pericytes. To regenerate a functional vascular system, arteries should be properly reconstructed with mural cells although the mechanisms underlying artery reconstruction remain unclear. In this study, we examined the process of artery reconstruction during regeneration of the zebrafish caudal fin as a model to study arterial formation in an adult setting. During fin regeneration, the arteries and veins form a net-like vasculature called the vascular plexus, and this plexus undergoes remodeling to form a new artery and two flanking veins. We found that the new vascular plexus originates mainly from venous cells in the stump but very rarely from the arterial cells. Interestingly, these vein-derived cells contributed to the reconstructed arteries. This arterialization was dependent on Notch signaling, and further analysis showed that Notch signaling was required for the initiation of arterial gene expression. In contrast, venous remodeling did not require Notch signaling. These results provide new insights toward understanding mechanisms of vascular regeneration and illustrate the utility of the adult zebrafish fin to study this process.

Raddeanin A, a triterpenoid saponin isolated from Anemone raddeana, suppresses the angiogenesis and growth of human colorectal tumor by inhibiting VEGFR2 signaling

Raddeanin A (RA) is an active triterpenoid saponin from a traditional Chinese medicinal herb, Anemone raddeana Regel. It was previously reported that RA possessed attractive antitumor activity through inhibiting proliferation and inducing apoptosis of multiple cancer cells. However, whether RA can inhibit angiogenesis, an essential step in cancer development, remains unknown. In this study, we found that RA could significantly inhibit human umbilical vein endothelial cell (HUVEC) proliferation, motility, migration, and tube formation. RA also dramatically reduced angiogenesis in chick embryo chorioallantoic membrane (CAM), restrained the trunk angiogenesis in zebrafish, and suppressed angiogenesis and growth of human HCT-15 colorectal cancer xenograft in mice. Western blot assay showed that RA suppressed VEGF-induced phosphorylation of VEGFR2 and its downstream protein kinases including PLCγ1, JAK2, FAK, Src, and Akt. Molecular docking simulation indicated that RA formed hydrogen bonds and hydrophobic interactions within the ATP binding pocket of VEGFR2 kinase domain. Our study firstly provides the evidence that RA has high antiangiogenic potency and explores its molecular basis, demonstrating that RA is a potential agent or lead candidate for antiangiogenic cancer therapy.

Arteries are formed by vein-derived endothelial tip cells

Tissue vascularization entails the formation of a blood vessel plexus, which remodels into arteries and veins. Here we show, by using time-lapse imaging of zebrafish fin regeneration and genetic lineage tracing of endothelial cells in the mouse retina, that vein-derived endothelial tip cells contribute to emerging arteries. Our movies uncover that arterial-fated tip cells change migration direction and migrate backwards within the expanding vascular plexus. This behaviour critically depends on chemokine receptor cxcr4a function. We show that the relevant Cxcr4a ligand Cxcl12a selectively accumulates in newly forming bone tissue even when ubiquitously overexpressed, pointing towards a tissue-intrinsic mode of chemokine gradient formation. Furthermore, we find that cxcr4a mutant cells can contribute to developing arteries when in association with wild-type cells, suggesting collective migration of endothelial cells. Together, our findings reveal specific cell migratory behaviours in the developing blood vessel plexus and uncover a conserved mode of artery formation.

Sprouting of new blood vessels depends on the migration of endothelial tip cells into surrounding tissue. Here the authors reveal the existence of a distinct migratory signalling circuit that guides endothelial cells from developing veins to the leading tip position in developing arteries.

Docetaxel in cationic lipid nanocapsules for enhanced in vivo activity

The usefulness of Docetaxel (DT) as an anti-cancer agent is limited to parenteral route owing to its very poor oral bioavailability. Thus, to improve its oral efficacy, DT was loaded in novel cationic lipid nanocapsules (DT CLNC). The DT CLNC possessed size of 130-150 nm, zeta potential of +72mV, adequate DT loading and over 95% encapsulation efficiency. TEM revealed capsular structure of DT CLNC. Lipolysis study indicated improved solubilization of DT by nanocapsules in comparison to DT solution. DT CLNC exhibited significantly higher release of DT in comparison to DT solution during in vitro permeation studies employing non-reverted rat-intestinal sac. Superior uptake of DT in zebra fishes exposed to DT CLNC resulted in greater apoptosis-based cell death as compared to those exposed to DT solution. This correlated well with the significantly superior (p < 0.05) anti-angiogenic activity of DT CLNC system over DT solution, in zebra fish model. DT CLNC also inhibited tumor growth in melanoma cell line induced tumors in C57BL/6 mice significantly, as compared to DT solution (p < 0.05). The DT CLNC system demonstrated adequate stability, with tremendous potential to improve oral efficacy of DT and can serve as an alternative to existing DT formulations available commercially for parenteral use.

Fibroblast growth factor signaling affects vascular outgrowth and is required for the maintenance of blood vessel integrity

Angiogenesis contributes to the development of numerous disorders. Even though fibroblast growth factors (FGFs) were discovered as mediators of angiogenesis more than 30 years ago, their role in developmental angiogenesis still remains elusive. We use a recently described chemical probe, SSR128129E (SSR), that selectively inhibits the action of multiple FGF receptors (FGFRs), in combination with the zebrafish model to examine the role of FGF signaling in vascular development. We observe that while FGFR signaling is less important for vessel guidance, it affects vascular outgrowth and is especially required for the maintenance of blood vessel integrity by ensuring proper cell-cell junctions between endothelial cells. In conclusion, our work illustrates the power of a small molecule probe to reveal insights into blood vessel formation and stabilization and thus of broad interest to the vascular biology community.

Marine compound catunaregin inhibits angiogenesis through the modulation of phosphorylation of akt and eNOS in vivo and in vitro

Angiogenesis is the formation of blood vessels from pre-existing vasculature. Excessive or uncontrolled angiogenesis is a major contributor to many pathological conditions whereas inhibition of aberrant angiogenesis is beneficial to patients with pathological angiogenesis. Catunaregin is a core of novel marine compound isolated from mangrove associate. The potential anti-angiogenesis of catunaregin was investigated in human umbilical vein endothelial cells (HUVECs) and zebrafish. HUVECs were treated with different concentrations of catunaregin in the presence or absence of VEGF. The angiogenic phenotypes including cell invasion cell migration and tube formation were evaluated following catunaregin treatment in HUVECs. The possible involvement of AKT, eNOS and ERK1/2 in catunaregin-induced anti-angiogenesis was explored using Western blotting. The anti-angiogenesis of catunaregin was further tested in the zebrafish embryo neovascularization and caudal fin regeneration assays. We found that catunaregin dose-dependently inhibited angiogenesis in both HUVECs and zebrafish embryo neovascularization and zebrafish caudal fin regeneration assays. In addition, catunaregin significantly decreased the phosphorylation of Akt and eNOS, but not the phosphorylation of ERK1/2. The present work demonstrates that catunaregin exerts the anti-angiogenic activity at least in part through the regulation of the Akt and eNOS signaling pathways.

Developmental processes regulated by the 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) pathway: highlights from animal studies

The 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR) is the rate-limiting enzyme in the biosynthesis of cholesterol and isoprenoids, which are substrates required for post-translational modification of signalling proteins that can potentially regulate various aspects of embryonic development. The HMGCR transcripts are detectable during early embryogenesis in both invertebrates and vertebrates, which suggests a conserved developmental requirement for mevalonate derivatives. Consistently, recent animal and in vitro studies have yielded valuable insights into potential morphogenic parameters that are modulated by HMGCR activity. These developmental end-points include brain and craniofacial morphogenesis, PGC migration and survival, myocardial epithelial migration and fusion, EC migration and survival, and vascular stabilization. By providing a synthesis of these studies, we hope that this review will highlight the need to comprehensively examine the entire suite of developmental processes regulated by HMGCR.