Extracellular Environment-Controlled Angiogenesis, and Potential Application for Peripheral Nerve Regeneration.

Endothelial cells acquire different phenotypes to establish functional vascular networks. Vascular endothelial growth factor (VEGF) signaling induces endothelial proliferation, migration, and survival to regulate vascular development, which leads to the construction of a vascular plexuses with a regular morphology. The spatiotemporal localization of angiogenic factors and the extracellular matrix play fundamental roles in ensuring the proper regulation of angiogenesis. This review article highlights how and what kinds of extracellular environmental molecules regulate angiogenesis. Close interactions between the vascular and neural systems involve shared molecular mechanisms to coordinate developmental and regenerative processes. This review article focuses on current knowledge about the roles of angiogenesis in peripheral nerve regeneration and the latest therapeutic strategies for the treatment of peripheral nerve injury.

Sprouting Angiogenesis: A Numerical Approach with Experimental Validation.

A functional vascular network is essential to the correct wound healing. In sprouting angiogenesis, vascular endothelial growth factor (VEGF) regulates the formation of new capillaries from pre-existing vessels. This is a very complex process and mathematical formulation permits to study angiogenesis using less time-consuming, reproducible and cheaper methodologies. This study aimed to mimic the chemoattractant effect of VEGF in stimulating sprouting angiogenesis. We developed a numerical model in which endothelial cells migrate according to a diffusion-reaction equation for VEGF. A chick chorioallantoic membrane (CAM) bioassay was used to obtain some important parameters to implement in the model and also to validate the numerical results. We verified that endothelial cells migrate following the highest VEGF concentration. We compared the parameters-total branching number, total vessel length and branching angle-that were obtained in the in silico and the in vivo methodologies and similar results were achieved (p-value smaller than 0.5; n = 6). For the difference between the total capillary volume fractions assessed using both methodologies values smaller than 15% were obtained. In this study we simulated, for the first time, the capillary network obtained during the CAM assay with a realistic morphology and structure.

VEGF in Signaling and Disease: Beyond Discovery and Development.

The discovery of vascular endothelial-derived growth factor (VEGF) has revolutionized our understanding of vasculogenesis and angiogenesis during development and physiological homeostasis. Over a short span of two decades, our understanding of the molecular mechanisms by which VEGF coordinates neurovascular homeostasis has become more sophisticated. The central role of VEGF in the pathogenesis of diverse cancers and blinding eye diseases has also become evident. Elucidation of the molecular regulation of VEGF and the transformative development of multiple therapeutic pathways targeting VEGF directly or indirectly is a powerful case study of how fundamental research can guide innovation and translation. It is also an elegant example of how agnostic discovery and can transform our understanding of human disease. This review will highlight critical nodal points in VEGF biology, including recent developments in immunotherapy for cancer and multitarget approaches in neovascular eye disease.

The role of placental growth factor (PlGF) and its receptor system in retinal vascular diseases.

Placental growth factor (PlGF) is a member of the vascular endothelial growth factor (VEGF) family. Upon binding to VEGF- and neuropilin-receptor sub-types, PlGF modulates a range of neural, glial and vascular cell responses that are distinct from VEGF-A. As PlGF expression is selectively associated with pathological angiogenesis and inflammation, its blockade does not affect the healthy vasculature. PlGF actions have been extensively described in tumor biology but more recently there has been accumulating preclinical evidence that indicates that this growth factor could have an important role in retinal diseases. High levels of PlGF have been found in aqueous humor, vitreous and/or retina of patients exhibiting retinopathies, especially those with diabetic retinopathy (DR) and neovascular age-related macular degeneration (nvAMD). Expression of this growth factor seems to correlate closely with many of the key pathogenic features of early and late retinopathy in preclinical models. For example, studies using genetic modification and/or pharmacological treatment to block PlGF in the laser-induced choroidal neovascularization (CNV) model, oxygen-induced retinopathy model, as well as various murine diabetic models, have shown that PlGF deletion or inhibition can reduce neovascularization, retinal leakage, inflammation and gliosis, without affecting vascular development or inducing neuronal degeneration. Moreover, an inhibitory effect of PlGF blockade on retinal scarring in the mouse CNV model has also been recently demonstrated and was found to be unique for PlGF inhibition, as compared to various VEGF inhibition strategies. Together, these preclinical results suggest that anti-PlGF therapy might have advantages over anti-VEGF treatment, and that it may have clinical applications as a standalone treatment or in combination with anti-VEGF. Additional clinical studies are clearly needed to further elucidate the role of PlGF and its potential as a therapeutic target in ocular diseases.

Mathematical Modeling of Cellular Cross-Talk Between Endothelial and Tumor Cells Highlights Counterintuitive Effects of VEGF-Targeted Therapies.

Tumor growth and progression are critically dependent on the establishment of a vascular support system. This is often accomplished via the expression of pro-angiogenic growth factors, including members of the vascular endothelial growth factor (VEGF) family of ligands. VEGF ligands are overexpressed in a wide variety of solid tumors and therefore have inspired optimism that inhibition of the different axes of the VEGF pathway-alone or in combination-would represent powerful anti-angiogenic therapies for most cancer types. When considering treatments that target VEGF and its receptors, it is difficult to tease out the differential anti-angiogenic and anti-tumor effects of all combinations experimentally because tumor cells and vascular endothelial cells are engaged in a dynamic cross-talk that impacts key aspects of tumorigenesis, independent of angiogenesis. Here we develop a mathematical model that connects intracellular signaling responsible for both endothelial and tumor cell proliferation and death to population-level cancer growth and angiogenesis. We use this model to investigate the effect of bidirectional communication between endothelial cells and tumor cells on treatments targeting VEGF and its receptors both in vitro and in vivo. Our results underscore the fact that in vitro therapeutic outcomes do not always translate to the in vivo situation. For example, our model predicts that certain therapeutic combinations result in antagonism in vivo that is not observed in vitro. Mathematical modeling in this direction can shed light on the mechanisms behind experimental observations that manipulating VEGF and its receptors is successful in some cases but disappointing in others.

Vascular endothelial growth factor gene variations as a risk predictor in disc degeneration / Variação do gene fator de crescimento endotelial vascular como preditor de risco para a degeneração discal

ABSTRACT Objective: To evaluate the frequency of polymorphisms in the vascular endothelial growth factor (VEGF) gene, as well as to identify a potential risk haplotype among the polymorphic regions in this gene in patients with disc degeneration and in the Control Group. Methods: This study analyzed a total of 217 individuals distributed into the Disc Degeneration and Control Groups. Peripheral blood was collected from all patients to detect VEGF gene polymorphisms identified by qPCR (rs699947, rs1570360, rs2010963, rs833061 and rs3025039). All patients presenting disc degeneration had the confirmation by nuclear magnetic resonance test and were rated according to disc degeneration level. Results: All polymorphisms were in Hardy- Weinberg equilibrium (p>0.05) in the studied population. The genotypic frequency for Disc Degeneration and Control Group were rs699947 p = 0.475, rs1570360 p = 0.862, rs2010963 p = 0.823, rs833061 p=0.596 and rs3025039 p=0.230. In haplotype analysis, the compositions CAGGC (p=0.094) and CCGGC (p=0.054) stood out. Conclusion: The correlation between VEGF gene polymorphism as a risk predictor for disc degeneration was negative in the studied population. However, the VEGF gene has a large polymorphic region, and it is activated by various catabolic and metabolic factors in the disc degeneration process, which has not been fully elucidated.

RESUMO Objetivo: Avaliar a frequência dos polimorfismos no gene fator de crescimento endotelial vascular (VEGF), bem como identificar potencial haplótipo de risco entre as regiões polimórficas deste gene em pacientes com degeneração discal e em Grupo Controle. Métodos: Este estudo analisou 217 pacientes distribuídos nos Grupos Degeneração Discal e Grupo Controle. Foi coletado sangue periférico de todos os pacientes para a detecção dos polimorfismos do gene VEGF identificados por qPCR (rs699947, rs1570360, rs2010963, rs833061 e rs3025039). Todos os pacientes que apresentaram degeneração discal tiveram a confirmação por meio de ressonância magnética nuclear e avaliação do nível de degeneração do disco. Resultados: Todos os polimorfismos foram encontrados no equilíbrio de Hardy-Weinberg (p>0,05) na população estudada. A frequência genotípica para o Grupo Degeneração de Disco e do Grupo Controle foi rs699947 p=0,475, rs1570360 p=0,862, rs2010963 p=0,823, rs833061 p=0,596 e rs3025039 p=0,230. Para a análise do haplótipo, destacaram-se as composições CAGGC (p=0,094) e CCGGC (p=0,054). Conclusão: A correlação entre os polimorfismos do gene VEGF como preditor de risco para degeneração discal foi negativa na população estudada. No entanto, o VEGF possui grande região polimórfica, ativada por vários fatores catabólicos e metabólicos no processo de degeneração discal, que não está completamente elucidado.

Angiogenesis in Dermatology - Insights of Molecular Mechanisms and Latest Developments / Angiogénesis en Dermatología - Nuevos aspectos en mecanismos moleculares y últimos avances

Angiogenesis is the growth of new blood vessels from pre-existing vessels. It is a biological process essential in physiological wound healing or pathological inflammation and tumor growth, which underlies a complex interplay of stimulating and inhibiting signals. Extracellular matrix, cells of innate and adaptive immunity and endothelial cells itself are a major source of angiogenic factors that activate or inhibit specific receptors and consequently influence intracellular signaling pathways. Most inflammatory and neoplastic diseases in dermatology are characterized by excessive angiogenesis, such as psoriasis, atopic dermatitis, as well as melanoma, non-melanoma skin cancer, but also benign vascular neoplasia. In this article we describe current knowledge of angiogenesis and its most relevant mechanisms in different dermatological disorders with particular emphasis on the angiogenic factors (vascular endothelial growth factor) and angiopoietins as a target of current and future directions of anti-angiogenic therapy (AU)

La angiogénesis es el desarrollo de nuevos vasos a partir de estructuras vasculares preexistentes. Es un proceso biológico esencial en la cicatrización de las heridas, pero también en la inflamación y el crecimiento tumoral y es controlado por una compleja red de factores inhibitorios y estimulantes. La matriz extracelular, las células del sistema inmune innato y adaptativo así como las células endoteliales son fuente de factores angiogénicos que pueden estimular o inhibir receptores específicos y modificar la respuesta de distintas vías de señalización intracelular. La mayoría de las enfermedades inflamatorias y neoplásicas dermatológicas se caracterizan en general por un exceso de angiogénesis, como por ejemplo en la psoriasis, la dermatitis atópica, o el melanoma, así como en el cáncer cutáneo no melanocítico pero también en las neoplasias vasculares benignas. En este artículo de revisión describimos los conocimientos actuales del proceso de angiogénesis y sus mecanismos más relevantes en las diferentes enfermedades dermatológicas haciendo especial énfasis en los factores proangiogénicos como el factor de crecimiento vascular endotelial y las angiopoietinas como potenciales dianas terapéuticas (AU)

Mural lymphatic endothelial cells regulate meningeal angiogenesis in the zebrafish.

Mural cells of the vertebrate brain maintain vascular integrity and function, play roles in stroke and are involved in maintenance of neural stem cells. However, the origins, diversity and roles of mural cells remain to be fully understood. Using transgenic zebrafish, we identified a population of isolated mural lymphatic endothelial cells surrounding meningeal blood vessels. These meningeal mural lymphatic endothelial cells (muLECs) express lymphatic endothelial cell markers and form by sprouting from blood vessels. In larvae, muLECs develop from a lymphatic endothelial loop in the midbrain into a dispersed, nonlumenized mural lineage. muLEC development requires normal signaling through the Vegfc-Vegfd-Ccbe1-Vegfr3 pathway. Mature muLECs produce vascular growth factors and accumulate low-density lipoproteins from the bloodstream. We find that muLECs are essential for normal meningeal vascularization. Together, these data identify an unexpected lymphatic lineage and developmental mechanism necessary for establishing normal meningeal blood vasculature.

Vascular endothelial growth factor control mechanisms in skeletal growth and repair.

Vascular endothelial growth factor A (VEGF) is a critical regulator of vascular development and postnatal angiogenesis and homeostasis, and it is essential for bone development and repair. Blood vessels serve both as structural templates for bone formation and they provide essential cells, growth factors and minerals needed for synthesis and mineralization, as well as turnover, of the extracellular matrix in bone. Through its regulation of angiogenesis, VEGF contributes to coupling of osteogenesis to angiogenesis, and it directly controls the differentiation and function of osteoblasts and osteoclasts. In this review, we summarize the properties of VEGF and its receptors that are relevant to bone formation and repair; the roles of VEGF during development of endochondral and membranous bones; and the contributions of VEGF to bone healing during different phases of bone repair. Finally, we discuss contributions of altered VEGF function in inherited disorders with bone defects as part of their phenotypes, and we speculate on what will be required before therapeutic strategies based on VEGF modulation can be developed for clinical use to treat patients with bone growth disorders and/or compromised bone repair. Developmental Dynamics 246:227-234, 2017. © 2016 Wiley Periodicals, Inc.

Vascular endothelial growth factor gene variations as a risk predictor in disc degeneration.

OBJECTIVE: To evaluate the frequency of polymorphisms in the vascular endothelial growth factor (VEGF) gene, as well as to identify a potential risk haplotype among the polymorphic regions in this gene in patients with disc degeneration and in the Control Group. METHODS: This study analyzed a total of 217 individuals distributed into the Disc Degeneration and Control Groups. Peripheral blood was collected from all patients to detect VEGF gene polymorphisms identified by qPCR (rs699947, rs1570360, rs2010963, rs833061 and rs3025039). All patients presenting disc degeneration had the confirmation by nuclear magnetic resonance test and were rated according to disc degeneration level. RESULTS: All polymorphisms were in Hardy- Weinberg equilibrium (p>0.05) in the studied population. The genotypic frequency for Disc Degeneration and Control Group were rs699947 p = 0.475, rs1570360 p = 0.862, rs2010963 p = 0.823, rs833061 p=0.596 and rs3025039 p=0.230. In haplotype analysis, the compositions CAGGC (p=0.094) and CCGGC (p=0.054) stood out. CONCLUSION: The correlation between VEGF gene polymorphism as a risk predictor for disc degeneration was negative in the studied population. However, the VEGF gene has a large polymorphic region, and it is activated by various catabolic and metabolic factors in the disc degeneration process, which has not been fully elucidated.

Therapeutic angiogenesis: angiogenic growth factors for ischemic heart disease.

Stem cells encode vascular endothelial growth factors (VEGFs), fibroblastic growth factors (FGFs), stem cell factor, stromal cell-derived factor, platelet growth factor and angiopoietin that can contribute to myocardial vascularization. VEGFs and FGFs are the most investigated growth factors. VEGFs regulate angiogenesis and vasculogenesis. FGFs stimulate vessel cell proliferation and differentiation and are regulators of endothelial cell migration, proliferation and survival. Clinical trials of VEGF or FGF for myocardial angiogenesis have produced disparate results. The efficacy of therapeutic angiogenesis can be improved by: (1) identifying the most optimal patients; (2) increased knowledge of angiogenic factor pharmacokinetics and proper dose; (3) prolonging contact of angiogenic factors with the myocardium; (4) increasing the efficiency of VEGF or FGF gene transduction; and (5) utilizing PET or MRI to measure myocardial perfusion and perfusion reserve.

Mechanisms and regulation of endothelial VEGF receptor signalling.

Vascular endothelial growth factors (VEGFs) and their receptors (VEGFRs) are uniquely required to balance the formation of new blood vessels with the maintenance and remodelling of existing ones, during development and in adult tissues. Recent advances have greatly expanded our understanding of the tight and multi-level regulation of VEGFR2 signalling, which is the primary focus of this Review. Important insights have been gained into the regulatory roles of VEGFR-interacting proteins (such as neuropilins, proteoglycans, integrins and protein tyrosine phosphatases); the dynamics of VEGFR2 endocytosis, trafficking and signalling; and the crosstalk between VEGF-induced signalling and other endothelial signalling cascades. A clear understanding of this multifaceted signalling web is key to successful therapeutic suppression or stimulation of vascular growth.

Exploring the various aspects of the pathological role of vascular endothelial growth factor (VEGF) in diabetic retinopathy.

Diabetic retinopathy, a sight-threatening microvascular complication of diabetes mellitus, is initiated by retinal endothelial dysfunction and succeeded by various pathological events, eventually resulting in vision-loss. These events are regulated by numerous mediators, including vascular endothelial growth factor (VEGF), which induces the progression of various events characterizing diabetic retinopathy, such as neovascularization and macular edema. VEGF is physiologically required for regulating proliferation and assembling of endothelial cells, during vasculogenesis, as well as for their maintenance and survival throughout the lifetime of blood vessels. However, various pathological conditions are induced in the body during diabetes (such as ischemia, oxidative stress and overactivation of protein kinase C), which upregulate the expression of VEGF, thereby deviating it from its physiological role and leading to various pathological demonstrations such as angiogenesis, increased permeability of endothelium, decreased inhibition of pro-apoptotic proteins and activation of various other inflammatory mediators. Such events disrupt vascular homeostasis and play key roles in the pathophysiology of diabetic retinopathy. Hence, acknowledging various VEGF-mediated pathways helps in understanding the deeper aspects related to progression of this disorder. Targeting and inhibiting VEGF-mediated disease progression might provide an effective alternative therapy and hence prove beneficial in the treatment of diabetic retinopathy.

The vascular endothelial growth factors and receptors family: Up to now the only target for anti-angiogenesis therapy.

Angiogenesis is a complex biological phenomenon essential for a correct embryonic development and for post-natal growth. In adult life, it is a tightly regulated process but in several pathological conditions, angiogenesis results abnormal with either excessive or insufficient proliferation of blood vessels. The pro-angiogenic members of VEGF family, VEGF-A, VEGF-B and placental growth factor (PlGF), and the related receptors, VEGFR-1 and VEGFR-2, have a central and decisive role in pathological angiogenesis. Indeed, they are the targets for anti-angiogenic drugs currently approved: bevacizumab and ranibizumab, that specifically inhibit VEGF-A; aflibercept, that is able to prevent the activity of VEGF-A, VEGF-B and PlGF; several multirtarget tyrosine kinase inhibitors that are able to prevent VEGFR-1 and/or VEGFR-2 signaling. The anti-angiogenesis therapy has represented one of the most active fields of drug discovery of last decade and promises to be further expanded due the wide number of diseases for which it may by applied.

Switching between humoral and cellular immune responses in Drosophila is guided by the cytokine GBP.

Insects combat infection through carefully measured cellular (for example, phagocytosis) and humoral (for example, secretion of antimicrobial peptides (AMPs)) innate immune responses. Little is known concerning how these different defense mechanisms are coordinated. Here, we use insect plasmatocytes and hemocyte-like Drosophila S2 cells to characterize mechanisms of immunity that operate in the haemocoel. We demonstrate that a Drosophila cytokine, growth-blocking peptides (GBP), acts through the phospholipase C (PLC)/Ca(2+) signalling cascade to mediate the secretion of Pvf, a ligand for platelet-derived growth factor- and vascular endothelial growth factor-receptor (Pvr) homologue. Activated Pvr recruits extracellular signal-regulated protein kinase to inhibit humoral immune responses, while stimulating cell 'spreading', an initiating event in cellular immunity. The double-stranded RNA (dsRNA)-targeted knockdown of either Pvf2 or Pvr inhibits GBP-mediated cell spreading and activates AMP expression. Conversely, Pvf2 overexpression enhances cell spreading but inhibits AMP expression. Thus, we describe mechanisms to initiate immune programs that are either humoral or cellular in nature, but not both; such immunophysiological polarization may minimize homeostatic imbalance during infection.

The role of angiogenic factors in fibroid pathogenesis: potential implications for future therapy.

BACKGROUND: It is well established that tumors are dependent on angiogenesis for their growth and survival. Although uterine fibroids are known to be benign tumors with reduced vascularization, recent work demonstrates that the vasculature of fibroids is grossly and microscopically abnormal. Accumulating evidence suggests that angiogenic growth factor dysregulation may be implicated in these vascular and other features of fibroid pathophysiology. METHODS: Literature searches were performed in PubMed and Google Scholar for articles with content related to angiogenic growth factors and myometrium/leiomyoma. The findings are hereby reviewed and discussed. RESULTS: Multiple growth factors involved in angiogenesis are differentially expressed in leiomyoma compared with myometrium. These include epidermal growth factor (EGF), heparin-binding-EGF, vascular endothelial growth factor, basic fibroblast growth factor, platelet-derived growth factor, transforming growth factor-ß and adrenomedullin. An important paradox is that although leiomyoma tissues are hypoxic, leiomyoma feature down-regulation of key molecular regulators of the hypoxia response. Furthermore, the hypoxic milieu of leiomyoma may contribute to fibroid development and growth. Notably, common treatments for fibroids such as GnRH agonists and uterine artery embolization (UAE) are shown to work at least partly via anti-angiogenic mechanisms. CONCLUSIONS: Angiogenic growth factors play an important role in mechanisms of fibroid pathophysiology, including abnormal vasculature and fibroid growth and survival. Moreover, the fibroid's abnormal vasculature together with its aberrant hypoxic and angiogenic response may make it especially vulnerable to disruption of its vascular supply, a feature which could be exploited for treatment. Further experimental studies are required in order to gain a better understanding of the growth factors that are involved in normal and pathological myometrial angiogenesis, and to assess the potential of anti-angiogenic treatment strategies for uterine fibroids.

Aplicaciones de la inyección de grasa en Cirugía Plástica Reparadora y Estética. Nuestra evolución y estado actual / Lipofilling applications in Reconstructive and Aesthetic Plastic Surgery. Our evolution and current situation

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Antiangiogenic therapy for glioblastoma: the challenge of translating response rate into efficacy.

Glioblastoma are one of the mostly vascularized tumors and are histologically characterized by abundant endothelial cell proliferation. Vascular endothelial growth factor (VEGF) is responsible for a degree of vascular proliferation and vessel permeability leading to symptomatic cerebral edema. Initial excitement generated from the impressive radiographic response rates has waned due to concerns of limited long-term efficacy and the promotion of a treatment-resistant phenotype. Reasons for the discrepancy between high radiographic response rates and lack of survival benefit have led to a focus on identifying potential mechanisms of resistance to antiangiogenic therapy. However, equally important is the need to focus on identification of basic mechanisms of action of this class of drugs, determining the optimal biologic dose for each agent and identify the effect of antiangiogenic therapy on oxygen and drug delivery to tumor to optimize drug combinations. Finally, alternatives to overall survival (OS) need to be pursued using the application of validated parameters to reliably assess neurologic function and quality of life.

Emerging roles of immune cells in luteal angiogenesis.

In the mammalian ovary, the corpus luteum (CL) is a unique transient endocrine organ displaying rapid angiogenesis and time-dependent accumulation of immune cells. The CL closely resembles 'transitory tumours', and the rate of luteal growth equals that of the fastest growing tumours. Recently, attention has focused on multiple roles of immune cells in luteal function, not only in luteolysis (CL disruption by immune responses involving T lymphocytes and macrophages), but also in CL development (CL remodelling by different immune responses involving neutrophils and macrophages). Neutrophils and macrophages regulate angiogenesis, lymphangiogenesis, and steroidogenesis by releasing cytokines in the CL. In addition, functional polarisation of neutrophils (proinflammatory N1 vs anti-inflammatory N2) and macrophages (proinflammatory M1 vs anti-inflammatory M2) has been demonstrated. This new concept concurs with the phenomenon of immune function within the luteal microenvironment: active development of the CL infiltrating anti-inflammatory N2 and M2 versus luteal regression together with proinflammatory N1 and M1. Conversely, excessive angiogenic factors and leucocyte infiltration result in indefinite disordered tumour development. However, the negative feedback regulator vasohibin-1 in the CL prevents excessive tumour-like vasculogenesis, suggesting that CL development has well coordinated time-dependent mechanisms. In this review, we discuss the physiological roles of immune cells involved in innate immunity (e.g. neutrophils and macrophages) in the local regulation of CL development with a primary focus on the cow.