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Angiogenesis, the growth of blood vessels from an existing vasculature, can occur by sprouting from preexisting vessels or by vessel splitting (intussusception). Pathological angiogenesis drives choroidal neovascularization (CNV) in age related macular degeneration (AMD) which is commonly restricted under the retinal pigment epithelium (RPE), called occult CNV, but may also involve vessels penetrating through the RPE into the sub-retinal space. Pathological vessels are poorly developed, insufficiently perfused and highly leaky, phenotypes that are considered to drive disease progression and lead to poor prognosis. Currently, a number of anti-angiogenic drugs exists, the majority of which target vascular endothelial factor (VEGF), but although they often are highly beneficial for treating eye diseases in the short-term, they are generally of limited efficacy in other diseases such as cancer, and also have poorer efficacy when used for treatment of eye diseases in the long-term. A better understanding of the mechanisms underlying pathological angiogenesis can generate new targets for treatment leading to development of better drugs for cancer and retinopathies, but perhaps also other angiogenesis-dependent diseases, in the future. In this thesis mechanisms involved in developmental angiogenesis or pathological angiogenesis in the choroid, cornea or melanoma was identified. These findings highlight the need to further elaborate our knowledge related to angiogenesis in different tissues/conditions for a more targeted, and potentially effective treatment of diseases in the future. In paper I, we for the first time identified the choriocapillaries (CCs) in adult zebrafish and found that occult CNV could be induced by exposing the fish to severe hypoxia. Interestingly, we found that occult CNV relied on intussusception, involving not only de novo generation of intussusceptive pillars but also a previously poorly understood mechanism called pillar splitting. This involved HIF-VEGF-VEGFR2 signaling and evidence that this also occurred in both rats and humans suffering from AMD suggested that the mechanism was conserved and clinically relevant. In contrast, we found in paper II that the development of CCs in the zebrafish relies on sprouting angiogenesis, involve continuous remodeling, and delayed maturation of the vasculature in 2D. The initial development was found to occur by a unique process of tissuewide synchronized vasculogenesis. As expected, VEGFA via VEGFR2 was also critical for the development of these vessels in the zebrafish embryo, but surprisingly this was independent on hypoxia-inducible factor (HIF)-1. Inflammatory nuclear factor-kB (NF-kB) signaling is involved in the progression of angiogenesis, but this signaling pathway has mainly been studied in the inflammatory cells and the role of NF-kB in the endothelial cells during angiogenesis is poorly understood. In paper III, we found that blocking NF-kB signaling using a specific IKK2 blocker IMD0354, specifically blocks pathological as well as developmental angiogenesis by targeting endothelial cell NF-kB signaling in the endothelial cells. Using a rat model for suture-induced corneal neovascularization, IMD0354 treatment lead to reduced production of inflammatory C-C motif chemokine ligand 2 (CCL2), C-X-C motif chemokine ligand 5 (CXCL5) and VEGF, and thereby reduced pathological corneal angiogenesis in this model. Using the zebrafish tumor xenograft model in paper IV, we found an association between Microphthalmia associated transcription factor (MITF) and pigment epithelium derived factor (PEDF), which was involved in pathological tumor angiogenesis and metastasis. Similarly, in paper V we used zebrafish transplantation models to study and investigate the use of biocompatible polymers for the delivery of pro-angiogenic FGF-2 as a potential treatment strategy for ischemic diseases such as myocardial infarction (MI). Conclusively, this thesis provides new insights into diverse fields of angiogenic assays using zebrafish, and reveals new mechanisms of angiogenesis in health and disease. This work will hopefully provide a foundation for further studies into occult CNV related to AMD, a process that has not been possible to study previously in pre-clinical models. In addition, zebrafish xenograft or other transplantation models used in this work will likely be important to study cancer biology and to develop more attractive pharmaceutical preparations based on biocompatible hydrogels formulated as microspheres in the future.
Angiogenesis, the development of new blood vessels from the existing vasculature, is essential for physiological growth and over 18,000 research articles have been published describing the role of angiogenesis in over 70 different diseases, including cancer, diabetic retinopathy, rheumatoid arthritis and psoriasis. One of the most important technical challenges in such studies has been finding suitable methods for assessing the effects of regulators of eh angiogenic response. While increasing numbers of angiogenesis assays are being described both in vitro and in vivo, it is often still necessary to use a combination of assays to identify the cellular and molecular events in angiogenesis and the full range of effects of a given test protein. Although the endothelial cell - its migration, proliferation, differentiation and structural rearrangement - is central to the angiogenic process, it is not the only cell type involved. the supporting cells, the extracellular matrix and the circulating blood with its cellular and humoral components also contribute. In this book, experts in the use of a diverse range of assays outline key components of these and give a critical appraisal of their strengths and weaknesses. Examples include assays for the proliferation, migration and differentiation of endothelial cells in vitro, vessel outgrowth from organ cultures, assessment of endothelial and mural cell interactions, and such in vivo assays as the chick chorioallantoic membrane, zebrafish, corneal, chamber and tumour angiogenesis models. These are followed by a critical analysis of the biological end-points currently being used in clinical trials to assess the clinical efficacy of anti-angiogenic drugs, which leads into a discussion of the direction future studies should take. This valuable book is of interest to research scientists currently working on angiogenesis in both the academic community and in the biotechnology and pharmaceutical industries. Relevant disciplines include cell and molecular biology, oncology, cardiovascular research, biotechnology, pharmacology, pathology and physiology.
Scientific Frontiers in Developmental Toxicology and Risk Assessment reviews advances made during the last 10-15 years in fields such as developmental biology, molecular biology, and genetics. It describes a novel approach for how these advances might be used in combination with existing methodologies to further the understanding of mechanisms of developmental toxicity, to improve the assessment of chemicals for their ability to cause developmental toxicity, and to improve risk assessment for developmental defects. For example, based on the recent advances, even the smallest, simplest laboratory animals such as the fruit fly, roundworm, and zebrafish might be able to serve as developmental toxicological models for human biological systems. Use of such organisms might allow for rapid and inexpensive testing of large numbers of chemicals for their potential to cause developmental toxicity; presently, there are little or no developmental toxicity data available for the majority of natural and manufactured chemicals in use. This new approach to developmental toxicology and risk assessment will require simultaneous research on several fronts by experts from multiple scientific disciplines, including developmental toxicologists, developmental biologists, geneticists, epidemiologists, and biostatisticians.
Angiogenesis has recently played a critical role in regulation of adipose tissue expansion and regression. Like most other tissues in the body, adipose expansion and regression is accompanied by alteration of blood vessel density and structures. The vascular alteration plays an active role in regulation of adipose tissue size and functions. Targeting blood vessels in the adipose tissue have demonstrated to be a novel approach for possibly treatment of cancer, obesity and other metabolic diseases. This book provides the most updated information on this type research and discusses future opportunities for therapy..
Angiogenesis is essential for physiological processes including embryonic development, tissue regeneration, and reproduction. Under various pathological conditions the same angiogenic process contribute to the onset, development, and progression of many human diseases including cancer, diabetic complications, ocular disease, chronic inflammation and cardiovascular disease. Vascular endothelial growth factor (VEGF) is a key angiogenic factor for physiological and pathological angiogenesis. In addition to its strong angiogenic activity, VEGF also potently induces vascular permeability, often causing tissue edema in various pathological tissues. VEGF transduces its vascular signal through two tyrosine kinase receptors-VEGFR1 and VEGFR2, the latter being a functional receptor that mediates both angiogenic and vascular permeability effects. To study physiological and pathological functions of VEGF, we developed novel zebrafish disease models that permit us to study hypoxia-induced retinopathy and cancer metastasis processes. We have also administered anti-VEGF and anti-VEGFR specific antibodies to healthy mice to study the homeostatic role of VEGF in the maintenance of vascular integrity and its functions in various tissues and organs. Finally, using a zebrafish model, we evaluated if VEGF expression is regulated by circadian clock genes. In paper I, we developed protocols that create hypoxia-induced retinopathy in adult zebrafish. Adult fli1:EGFP zebrafish were placed in hypoxic water for 3-10 days with retinal neovascularization being analyzed using confocal microscopy. This model provides a unique opportunity to kinetically study the development of retinopathy in adult animals using non-invasive protocols and to assess the therapeutic efficacy of orally administered anti-angiogenic drugs. In paper II, we developed a zebrafish metastasis model to dissect the complex events of hypoxia-induced tumor cell invasion and metastasis in association with angiogenesis at the single-cell level. In this model, fluorescent DiI-labeled human or mouse tumor cells were implanted into the perivitelline cavity of 48-hour-old zebrafish embryos, which were subsequently placed in hypoxic water for 3 days. Tumor cell invasion, metastasis and pathological angiogenesis were analyzed using fluorescent microscopy in the living fish. The average experimental time for this model is 7 days. Our protocol offers an opportunity to study molecular mechanisms of hypoxia-induced cancer metastasis. In paper III, we show that systemic delivery of an anti-VEGF or an anti-VEGF receptor (VEGFR)-2 neutralizing antibody cause global vascular regression in mice. Among all examined tissues, the vasculature in endocrine glands, intestinal villi, and the uterus are most affected in response to VEGF or VEGFR-2 blockades. Pro-longed anti-VEGF treatment resulted in a significant decrease in the circulating levels of the predominant thyroid hormone, free thyroxine, but not the minimal isoform of triiodothyronine, suggesting that chronic anti-VEGF treatment impairs thyroid function. These findings provide structural and functional bases of anti-VEGF-specific druginduced side effects in relation to vascular changes in healthy tissues. In paper IV, we show that disruption of the circadian clock by constant exposure to light coupled with genetic manipulation of key genes in the zebrafish led to impaired developmental angiogenesis. A bmal1-specific morpholino inhibited developmental angiogenesis in zebrafish embryos without causing obvious nonvascular phenotypes. Conversely, a period2 morpholino accelerated angiogenic vessel growth, suggesting that Bmal1 and Period2 display opposing angiogenic effects. These results offer mechanistic insights into the role of the circadian clock in regulation of developmental angiogenesis, and our findings may be reasonably extended to other types of physiological or pathological angiogenesis. Overall, the results in this thesis provide further insight to angiogenic mechanistic properties in tissues and suggest possible novel therapeutic targets for the treatment of various angiogenesis-dependent diseases.
The volume includes 75 papers which were presented at the Third International Conference on Intracerebral Hemorrhage, held in Rancho Mirage, California, in March 2010. The topics treated include animal models, pathophysiology of cerebral hemorrhage, experimental treatment for cerebral hemorrhage, cerebral hemorrhage clinical manifestations, prognosis of cerebral hemorrhage, and clinical management. The articles represent the recent advances in hemorrhagic brain injury research presented by highly respected laboratories around the world.
The increasing demand for innovative techniques arises from the lack of safe, effective, and patient-friendly therapies for neurodegenerative disorders. With this objective in mind, the chapters of the book are structured to offer a thorough insight into recent advancements in utilizing the zebrafish (ZF) as a model for studying Parkinson’s disease (PD). This book aims to present readers with a comprehensive understanding of the clinical application of the ZF model in treating PD, encompassing the latest developments, challenges, safety considerations, toxicity issues, regulatory aspects, future potential, and limitations. Individuals in academia, the scientific community, business, and education seeking a more effective approach to target the brain stand to benefit from this resource. Key Features Provides a comparative perspective of the zebrafish–Parkinson’s disease model Highlights the restrictions of available medicines Describes biochemical and histopathological characteristics, advantages, and disadvantages of this model Emphasizes distinct facets of histopathology Presents advances and developments of the future potential perspectives
The way a cell undergoes malignant transformation should meet their capacity of surviving in the microenvironment of the organ where the cancer will develop. Metabolic adaptation is for sure one of the criteria that must be accomplished, driven by metabolic plasticity that allows the adaptation of cancer cells to the availability of energy and biomass sources that will sustain cell survival and proliferation. Each human organ has a particular microenvironment which depends on several cell types and in some cases also on symbiotic microorganisms. These biological partners are constantly sharing organic compounds and signaling molecules that will control mitogenesis, cell death and differentiation, accounting for the organ's function. Nevertheless, cancer cells are capable of taking advantage of this metabolic and signaling microenvironmental dynamics. In this book, we intend to present the different components of the microenvironment driving the metabolic fitness of cancer cells. The metabolic changes required for establishing a tumor in a given microenvironment and how these metabolic changes limit the response to drugs will generally be the major items addressed. It is important to mention not only aspects of the microenvironment that stimulate metabolic changes and that select better adapted tumor cells, but also how this regulation of cell plasticity is made. Thus, the signaling pathways that orchestrate and are orchestrated throughout this panoply of metabolic rearrangements will also be addressed in this book. The subjects will be presented from the conceptual point of view of the cross-cancer mechanisms and also particularizing some models that can be examples and enlightening within the different areas.
The formation of blood vessels is an essential aspect of embryogenesis in vertebrates. It is a central feature of numerous post-embryonic processes, including tissue and organ growth and regeneration. It is also part of the pathology of tumour formation and certain inflammatory conditions. In recent years, comprehension of the molecular genetics of blood vessel formation has progressed enormously and studies in vertebrate model systems, especially the mouse and the zebrafish, have identified a common set of molecules and processes that are conserved throughout vertebrate embryogenesis while, in addition, highlighting aspects that may differ between different animal groups. The discovery in the past decade of the crucial role of new blood vessel formation for the development of cancers has generated great interest in angiogenesis (the formation of new blood vessels from pre-existing ones), with its major implications for potential cancer-control strategies. In addition, there are numerous situations where therapeutic treatments either require or would be assisted by vasculogenesis (the de novo formation of blood vessels). In particular, post-stroke therapies could include treatments that stimulate neovascularization of the affected tissues. The development of such treatments, however, requires thoroughly understanding the developmental properties of endothelial cells and the basic biology of blood vessel formation. While there are many books on angiogenesis, this unique book focuses on exactly this basic biology and explores blood vessel formation in connection with tissue development in a range of animal models. It includes detailed discussions of relevant cell biology, genetics and embryogenesis of blood vessel formation and presents insights into the cross-talk between developing blood vessels and other tissues. With contributions from vascular biologists, cell biologists and developmental biologists, a comprehensive and highly interdisciplinary volume is the outcome.