Search

Diabetic retinopathy (DR) has been regarded as a sight-threatening vascular complication of diabetes mellitus. Accumulating evidence has identified the involvement of long non-coding RNAs (lncRNAs) in DR pathogenesis. We aim to investigate the role and underlying mechanism of linc00174 in the DR process. Samples of human vitreous humour from proliferative DR and non-diabetic individuals were collected to examine the levels of linc00174. Human retinal microvascular endothelial cells (HRMECs) exposed with high glucose (HG) were employed to simulate the pathological statues of DR. Short hairpin RNA specifically targeting linc00174 was applied. CCK-8, transwell, and matrigel tube formation were performed to evaluate cell proliferation, migration, and angiogenesis. Bioinformatics analysis and luciferase reporter assay were conducted to verify the linc00174/miR-150-5p/vascular endothelial growth factor A (VEGFA) regulatory network. Western blotting was employed to determine the expression of VEGFA. Linc00174 was significantly elevated in patients with DR, as well as HG-stimulated HRMECs, of which knockdown repressed HG-induced proliferation, migration, and angiogenesis. miR-150-5p was identified as a downstream effector to be involved in linc00174-mediated protective effects. miR-150-5p directly bound to the 3′ untranslated region of VEGFA. The linc00174/miR-150-5p/VEGFA axis was confirmed in retinal vascular dysfunction. The linc00174 deteriorates diabetic retinal microangiopathy via regulating miR-150-5p/VEGFA pathway, indicating a novel therapeutic target for DR treatment.

G protein-coupled receptor (GPCR) kinase 2 (GRK2) is an integrative node in many signaling network cascades. Emerging evidence indicates that GRK2 can interact with a large number of GPCRs and non-GPCR substrates in both kinase-dependent and -independent modes. Some of these pathways are associated with endothelial cell (EC) activity. The active state of ECs is a pivotal factor in angiogenesis. The occurrence and development of some inflammation-related diseases are accompanied by pathological angiogenesis, but there remains a lack of effective targeted treatments. Alterations in the expression and/or localization of GRK2 have been identified in several types of diseases and have been demonstrated to regulate the angiogenesis process in these diseases. GRK2 as a target may be a promising candidate for anti-angiogenesis therapy.

Semaphorins, the neuronal guidance cues, were shown to have broad influences on pathophysiological processes such as bone remodeling, immune responses, and angiogenesis. In particular, Class-3 Semaphorins (SEMA3) is considered a vital regulator involved in angiogenesis. Scientific evidence has pointed to the role of angiogenesis in many diseases, and numerous efforts have been made to explore the possibilities of curing those diseases by targeting angiogenesis. Nevertheless, the efficacies are limited owing to the complex mechanisms of angiogenesis. Hence, investigating the mechanisms of SEMA3 in angiogenesis may contribute to novel therapeutics for diseases. Previous reviews mainly focused on the various functions of semaphorins in one particular disease, and the specific angiogenesis mechanism of SEMA3 in diverse diseases has not been well elucidated. Additionally, the role of SEMA3 in angiogenesis remains elusive, as contradicting results have been found in different disease types. Some evidence from recent studies implies that, while most SEMA3 molecules inhibit pathological angiogenesis in different diseases, occasionally SEMA3 may also promote angiogenesis. This review summarizes the specific role of SEMA3 in a variety of angiogenesis-associated diseases, and documents SEMA3 may be a promising therapeutic target for treating angiogenesis-associated diseases.

Objective: VEGFA (Vascular endothelial growth factor A) and its receptor VEGFR2 (vascular endothelial growth factor receptor 2) drive angiogenesis in several pathologies, including diabetic retinopathy, wet age-related macular degeneration, and cancer. Studies suggest roles for HSPGs (heparan sulfate proteoglycans) in this process, although the nature of this involvement remains elusive. Here, we set to establish the role of the HSPG SDC4 (syndecan-4) in pathological angiogenesis. Approach and Results: We report that angiogenesis is impaired in mice null for SDC4 in models of neovascular eye disease and tumor development. Our work demonstrates that SDC4 is the only SDC whose gene expression is upregulated during pathological angiogenesis and is selectively enriched on immature vessels in retinas from diabetic retinopathy patients. Combining in vivo and tissue culture models, we identified SDC4 as a downstream mediator of functional angiogenic responses to VEGFA. We found that SDC4 resides at endothelial cell junctions, interacts with vascular endothelial cadherin, and is required for its internalization in response to VEGFA. Finally, we show that pathological angiogenic responses are inhibited in a model of wet age-related macular degeneration by targeting SDC4. Conclusions: We show that SDC4 is a downstream mediator of VEGFA-induced vascular endothelial cadherin internalization during pathological angiogenesis and a potential target for antiangiogenic therapies.

Pathological angiogenesis is a hallmark of cancer; accordingly, a number of anticancer FDA-approved drugs act by inhibiting angiogenesis via different mechanisms. However, the development process of the most potent anti-angiogenics has met various hurdles including redundancy, multiplicity, and development of compensatory mechanisms by which blood vessels are remodeled. Moreover, identification of broad-spectrum anti-angiogenesis targets is proved to be required to enhance the efficacy of the anti-angiogenesis drugs. In this perspective, a proper understanding of the structure activity relationship (SAR) of the recent anti-angiogenics is required. Various anti-angiogenic classes have been developed over the years; among them, the heterocyclic organic compounds come to the fore as the most promising, with several drugs approved by the FDA. In this review, we discuss the structure–activity relationship of some promising potent heterocyclic anti-angiogenic leads. For each lead, a molecular modelling was also carried out in order to correlate its SAR and specificity to the active site. Furthermore, an in silico pharmacokinetics study for some representative leads was presented. Summarizing, new insights for further improvement for each lead have been reviewed.

Increased subchondral bone angiogenesis with blood vessels breaching the tidemark into the avascular cartilage is a diagnostic feature of human osteoarthritis. However, the mechanisms that initiate subchondral bone angiogenesis remain unclear. We show that abnormally increased platelet-derived growth factor–BB (PDGF-BB) secretion by mononuclear preosteoclasts induces subchondral bone angiogenesis, contributing to osteoarthritis development. In mice after destabilization of the medial meniscus (DMM), aberrant joint subchondral bone angiogenesis developed during an early stage of osteoarthritis, before articular cartilage damage occurred. Mononuclear preosteoclasts in subchondral bone secrete excessive amounts of PDGF-BB, which activates platelet-derived growth factor receptor–β (PDGFR-β) signaling in pericytes for neo-vessel formation. Selective knockout of PDGF-BB in preosteoclasts attenuates subchondral bone angiogenesis and abrogates joint degeneration and subchondral innervation induced by DMM. Transgenic mice that express PDGF-BB in preosteoclasts recapitulate pathological subchondral bone angiogenesis and develop joint degeneration and subchondral innervation spontaneously. Our study provides the first evidence to our knowledge that PDGF-BB derived from preosteoclasts is a key driver of pathological subchondral bone angiogenesis during osteoarthritis development and offers a new avenue for developing early treatments for this disease.

Magnetic Resonance Imaging (MRI) enables to provide anatomical, functional and molecular information of pathological angiogenesis when used with properly tailored imaging probes. Functional studies have been the domain of Dynamic Contrast Enhancement (DCE) -MRI protocols from which it is possible to extract quantitative estimations on key parameters such as the volumes of vascular and extracellular compartments and the rates of the bidirectional exchange of the imaging reporters across the endothelial barrier. Whereas paramagnetic Gd-complexes able to reversibly bind to serum albumin act better than the clinically used small-sized, hydrophilic species, new findings suggest that an accurate assessment of the vascular volume is possible by analyzing images acquired upon the i.v. administration of Gd-labelled Red Blood Cells (RBCs). As far as it concerns molecular MRI, among the many available biomarkers, αvβ3 integrins are the most investigated ones. The low expression of these targets makes mandatory the use of nano-sized systems endowed with the proper signal enhancing capabilities. A number of targeted nano-particles have been investigated including micelles, liposomes, iron oxides and perfluorocarbon containing systems. Finally, a growing attention is devoted to the design and testing of "theranostic" agents based on the exploitation of MRI to monitor drug delivery processes and therapeutic outcome.

The endothelium is crucially important for the delivery of oxygen and nutrients throughout the body under homeostatic conditions. However, it also contributes to pathology, including the initiation and perpetuation of inflammation. Understanding the function of endothelial cells (ECs) in inflammatory diseases and molecular mechanisms involved may lead to novel approaches to dampen inflammation and restore homeostasis. In this article, we discuss the various functions of ECs in inflammation with a focus on pathological angiogenesis, attraction of immune cells, antigen presentation, immunoregulatory properties and endothelial-to-mesenchymal transition (EndMT). We also review the current literature on approaches to target these processes in ECs to modulate immune responses and advance anti-inflammatory therapies.

Apelin is the endogenous ligand of the G protein-coupled receptor APJ. Both Apelin and APJ receptor are widely distributed in various tissues such as heart, brain, limbs, retina and liver. Recent research indicates that the Apelin/APJ system plays an important role in pathological angiogenesis which is a progress of new blood branches developing from preexisting vessels via sprouting. In this paper, we review the important role of the Apelin/APJ system in pathological angiogenesis. The Apelin/APJ system promotes angiogenesis in myocardial infarction, ischemic stroke, critical limb ischemia, tumor, retinal angiogenesis diseases, cirrhosis, obesity, diabetes and other related diseases. Furthermore, we illustrate the detailed mechanism of pathological angiogenesis induced by the Apelin/APJ system. In conclusion, the Apelin/APJ system would be a promising therapeutic target for angiogenesis-related diseases.

Background We recently discovered a small endogenous peptide, peptide Lv, with the ability to activate vascular endothelial growth factor receptor 2 and its downstream signaling. As vascular endothelial growth factor through vascular endothelial growth factor receptor 2 contributes to normal development, vasodilation, angiogenesis, and pathogenesis of various diseases, we investigated the role of peptide Lv in vasodilation and developmental and pathological angiogenesis in this study. Methods and Results The endothelial cell proliferation, migration, and 3‐dimensional sprouting assays were used to test the abilities of peptide Lv in angiogenesis in vitro. The chick chorioallantoic membranes and early postnatal mice were used to examine its impact on developmental angiogenesis. The oxygen‐induced retinopathy and laser‐induced choroidal neovascularization mouse models were used for in vivo pathological angiogenesis. The isolated porcine retinal and coronary arterioles were used for vasodilation assays. Peptide Lv elicited angiogenesis in vitro and in vivo. Peptide Lv and vascular endothelial growth factor acted synergistically in promoting endothelial cell proliferation. Peptide Lv–elicited vasodilation was not completely dependent on nitric oxide, indicating that peptide Lv had vascular endothelial growth factor receptor 2/nitric oxide–independent targets. An antibody against peptide Lv, anti‐Lv, dampened vascular endothelial growth factor–elicited endothelial proliferation and laser‐induced vascular leakage and choroidal neovascularization. While the pathological angiogenesis in mouse eyes with oxygen‐induced retinopathy was enhanced by exogenous peptide Lv, anti‐Lv dampened this process. Furthermore, deletion of peptide Lv in mice significantly decreased pathological neovascularization compared with their wild‐type littermates. Conclusions These results demonstrate that peptide Lv plays a significant role in pathological angiogenesis but may be less critical during development. Peptide Lv is involved in pathological angiogenesis through vascular endothelial growth factor receptor 2–dependent and –independent pathways. As anti‐Lv dampened the pathological angiogenesis in the eye, anti‐Lv may have a therapeutic potential to treat pathological angiogenesis.

Diabetic retinopathy (DR) is a devastating complication of diabetes. The aim of the present study is to investigate the exact role and mechanism of long noncoding RNA MALAT1 (MALAT1) in the progress of DR. An oxygen-induced retinopathy (OIR) mouse model and high glucose (HG) stimulated human retinal microvascular endothelial cells (HRMECs) were employed to mimic the pathological statues of DR. Quantitative real-time PCR (qRT-PCR) and Western blot results showed that MALAT1, VEGFA, and HIF-1α levels were increased in DR retinal tissues and HG-stimulated HRMECs, whereas the expression of miR-203a-3p was decreased. Knockdown of MALAT1 or upregulation of miR-203a-3p both suppressed HG-induced proliferation, migration, and tube formation of HRMECs. A dual-luciferase reporter assay showed that miR-203a-3p could bind to the predicted seed regions of MALAT1 as evidenced by the reduced luciferase activity. Furthermore, enforced downregulation of miR-203a-3p abolished the suppressive effect of MALAT1 silencing on HRMEC cell migration and tube formation. In conclusion, these data demonstrated that MALAT1 may affect angiogenesis by sponging miR-203a-3p in DR, suggesting that MALAT1 may act as a novel therapeutic target for the treatment of DR.

Macrophages are involved in angiogenesis, an essential process for organ growth and tissue repair, and could contribute to the pathogenesis of angiogenesis-related diseases such as malignant tumors and diabetic retinopathy. Recently, long noncoding RNAs (lncRNAs) have been proved to be important in cell differentiation, organismal development, and various diseases of pathological angiogenesis. Moreover, it has been indicated that numerous lncRNAs exhibit different functions in macrophage infiltration and polarization and regulate the secretion of inflammatory cytokines released by macrophages. Therefore, the focus of macrophage-related lncRNAs could be considered to be a potential method in therapeutic targeting angiogenesis-related diseases. This review mainly summarizes the roles played by lncRNAs which associated with macrophages in angiogenesis. The possible mechanisms of the regulatory link between lncRNAs and macrophages in various angiogenesis-related diseases were also discussed.

Neovascular and inflammatory retinal diseases including wet age‐related macular degeneration ( AMD ) can cause severe vision loss among the elderly. Simultaneous neutralization of vascular endothelial growth factor‐A ( VEGF ‐A) and angiopoietin 2 ( ANG 2) is envisioned as a novel candidate approach to treat wet AMD with better efficacy. However, earlier published data from a genetic mouse model showed data aberrations (Regula et al, 2016). In this issue of EMBO Molecular Medicine, Foxton et al (2019) have provided compelling evidence replicating the data and confirming the overall concept that VEGF ‐A/ ANG 2 combotherapy is effective in suppressing retinal neovascularization.

Aptamers are single-stranded DNA or RNA oligonucleotides that are currently used in clinical trials due to their selectivity and specificity to bind small molecules such as proteins, peptides, viral particles, vitamins, metal ions and even whole cells. Aptamers are highly specific to their targets, they are smaller than antibodies and fragment antibodies, they can be easily conjugated to multiple surfaces and ions and controllable post-production modifications can be performed. Aptamers have been therapeutically used for age-related macular degeneration, cancer, thrombosis and inflammatory diseases. The aim of this review is to highlight the therapeutic, diagnostic and prognostic possibilities associated with aptamers, focusing on eye pathological angiogenesis.

Retinopathy of prematurity (ROP) is an ocular vascular disease affecting premature infants, characterized by pathological retinal neovascularization (RNV), dilated and tortuous retinal blood vessels, and retinal or vitreous hemorrhages that may lead to retinal detachment, vision impairment and blindness. Compared with other neovascular diseases, ROP is unique because of ongoing and concurrent physiological and pathological angiogenesis in the developing retina. While the disease is currently treated by laser or cryotherapy, anti-vascular endothelial growth factor (VEGF) agents have been extensively investigated but are not approved in the U.S. because of safety concerns that they negatively interfere with physiological angiogenesis of the developing retina. An ideal therapeutic strategy would selectively inhibit pathological but not physiological angiogenesis. Our group recently described a novel strategy that selectively and safely alleviates pathological RNV in animal models of ROP by targeting secretogranin III (Scg3), a disease-restricted angiogenic factor. The preclinical profile of anti-Scg3 therapy presents a high potential for next-generation disease-targeted anti-angiogenic therapy for the ROP indication. This review focuses on retinal vessel development in neonates, the pathogenesis of ROP and its underlying molecular mechanisms, including different animal models, and provides a summary of current and emerging therapies.

Liver pathological angiogenesis is considered to be one of the key events in the development of liver fibrosis. Autophagy is a defense and stress regulation mechanism. However, whether autophagy regulates pathological angiogenesis in liver fibrosis is still questionable. Here, we aimed to study how curcumol regulated liver sinusoidal endothelial cells (LSECs) angiogenesis through autophagy. We found that curcumol (10, 20 and 40 μM) could inhibit the expression of angiogenesis markers in the LSECs. Importantly, we showed that curcumol might influence LSEC pathological angiogenesis by regulating autophagy level. Furthermore, we indicated that the transcription factor Krüppel-like factor 5 (KLF5) was considered as a key target for curcumol to regulate LSEC angiogenesis. Interestingly, we also suggested that autophagy was as a potential mechanism for curcumol to restrain KLF5 expression. Increased autophagy level could impair the suppression effect of curcumol on KLF5. Fascinatingly, our results indicated that curcumol inhibited autophagy and led to p62 accumulation, which might be a regulation mechanism of KLF5 degradation. Finally, in mice liver fibrosis model, we unanimously showed that curcumol (30 mg/kg) inhibited pathological angiogenesis by reducing LSEC autophagy level and suppressing KLF5 expression. Collectively, these results provided a deeper insight into the molecular mechanism of curcumol to inhibit LSEC pathological angiogenesis during liver fibrosis.

// Lei Zheng 1, 2, * , Chen Zhao 3, * , Yuxiang Du 2 , Xianchai Lin 2 , Yida Jiang 2 , Chunsik Lee 2 , Geng Tian 1 , Jia Mi 1 , Xianglin Li 1 , Qishan Chen 2 , Zhimin Ye 2 , Lijuan Huang 2 , Shasha Wang 2 , Xiangrong Ren 2 , Liying Xing 2 , Wei Chen 2 , Delong Huang 1, 2 , Zhiqin Gao 4 , Shuping Zhang 1 , Weisi Lu 2 , Zhongshu Tang 2 , Bin Wang 5 , Rong Ju 2 , Xuri Li 1, 2 1 Center for Medical and Pharmaceutical Research, Binzhou Medical University, Yantai, Shandong, 264003, P. R. China 2 State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou 510060, P. R. China 3 Department of Ophthalmology, the First Affiliated Hospital of Nanjing Medical University and State Key Laboratory of Reproductive Medicine, Nanjing Medical University, Nanjing 210029, P. R. China 4 Department of Cell Biology, Weifang Medical University, Weifang, 261053 P. R. China 5 Medical Imaging Institute, Shandong Province Characteristical Key Subject, Medical Imaging and Nuclear Medicine, Binzhou Medical University, Yantai, 264003 P. R. China * Equal first authors Correspondence to: Xuri Li, email: lixr6@mail.sysu.edu.cn Rong Ju, email: jurong@mail.sysu.edu.cn Bin Wang, email: binwang001@aliyun.com Keywords: angiogenesis, PDGF-CC, VEGF-A, drug resistance Received: May 11, 2016 Accepted: October 14, 2016 Published: October 24, 2016 ABSTRACT Anti-VEGF-A therapy has proven to be effective for many neovascular diseases. However, drug resistance to anti-VEGF-A treatment can develop. Also, not all patients with neovascular diseases are responsive to anti-VEGF-A treatment. The mechanisms underlying these important issues remain unclear. In this study, using different model systems, we found that inhibition of VEGF-A directly upregulated PDGF-CC and its receptors in multiple cell types in pathological angiogenesis in vitro and in vivo . Importantly, we further revealed that combinatorial targeting of VEGF-A and PDGF-CC suppressed pathological angiogenesis more efficiently than monotherapy. Given the potent angiogenic activity of PDGF-CC, our findings suggest that the development of resistance to anti-VEGF-A treatment may be caused by the compensatory upregulation of PDGF-CC, and combined inhibition of VEGF-A and PDGF-CC may have therapeutic advantages in treating neovascular diseases.

Accumulative evidences have underpinned the nature candidates from Chinese medicine (CM), particularly CM served as blood activating and stasis resolving (BASR, Huoxue Huayu in Chinese) by targeting tumor-associated angiogenesis. However, recent experiment research on the therapeutic angiogenesis by BASR-CM attracts wide attention and discussion. This opinion review focused on the underlying link between two indications and anticipated that (1) BASR-CM might emphasize on a balanced multi-cytokines network interaction; (2) BASR-CM might address on the nature of diseases prior to differently affecting physiological and pathological angiogenesis; (3) BASR-CM might mainly act on perivascular cells, either promotes arteriogenesis by increasing arteriogenic factors in ischemic diseases, or simultaneously keep a quiescent vasculature to impede angiogenesis in tumor context.

Angiogenesis is a complex physiological process. However, over the past couple of decades, abnormally accelerated or pathological angiogenesis has garnered greater attention from researchers the world over. Studies have shown that this abnormal and uncontrolled angiogenesis not only promotes inflammatory responses but also plays a role in various malignant and cardiovascular diseases. These include solid tumors, atherosclerosis, blinding retinopathy, and other diseases. Furthermore, there is mounting evidence that noncoding RNAs, especially lncRNAs and microRNAs, play important roles in the regulation of angiogenesis. In recent years, numerous studies have found that lncRNA may serve as an endogenous sponge to regulate the expression and function of miRNA, which in turn bind to lncRNA, regulating their stability. Therefore, this review focuses on the mechanisms of lncRNA/microRNA interactions in angiogenesis. A better understanding of such lncRNA/microRNA interactions may provide helpful insights and shed new light on areas of research for identifying diagnostic markers and therapeutic approaches for treating angiogenesis-related diseases.

Angiogenesis is defined as the growth of new capillaries sprouting from pre-existing vasculature. Pathological angiogenesis signals can lead to dysregulated development of new vessels. Inflammation is accompanied by pathological angiogenesis. During an inflammatory process, newly formed blood vessels provide oxygen and nutrients to the inflamed tissue, facilitating the transport of inflammatory cells. Therefore, angiogenesis is closely related to pathogenesis of inflammatory autoimmune diseases. As a member of the angiopoietin family, Angiopoietin-2 (Ang-2) plays an irreplaceable role in angiogenesis. This review will narrate the expression of Ang-2 and its role in inflammatory autoimmune diseases. Collecting this information may improve the acquaintance of Ang-2 and provide a theoretical foundation for clinical trials and drug development in the future.

Angiogenesis is the natural and physiologic process of growing blood vessels from pre-existing ones. Pathological angiogenesis occurs when the precise balance of all the molecular pathways that regulate angiogenesis is disrupted, and this process is a critical step in many diseases, including cancer. A limited number of antiangiogenic synthetic drugs have been developed. However, due to toxicity and side effects issues, the search for alternative to existing drugs is ongoing. In this sense, natural molecules obtained from plants or macrofungi, have demonstrated extraordinary potential in the treatment of angiogenesis-related pathologies, specially taking into consideration its absence or very low toxicity, when compared to synthetic drugs. Using natural compounds as potential angiogenesis modulators is thus a promising field of research, supporting the creation of novel therapies able to reduce the use of drugs and associated side effects. In this review, the current status of antiangiogenic drugs and the wide variety of natural extracts and molecules with antiangiogenic capacities, as well as the angiogenesis molecular pathways and therapeutic targets, are presented. Finally, the challenges that need to be overcome in order to increase the use of natural compounds for clinical purposes are discussed. POCI-01-0145-FEDER-006984 (LA LSRE-LCM), funded by FEDER, through POCI-COMPETE2020 and FCT; Project NORTE-01-0145- FEDER-000006, funded by NORTE2020 under the PT2020, through ERDF; FCT and ERDF under PT2020 for financial support to CIMO (UID/AGR/00690/2013). Andreia Ribeiro acknowledges her PhD fellowship funded by Project NORTE-08-5369-FSE-000028, supported by N2020, under PT2020, through ESF. info:eu-repo/semantics/publishedVersion

Chronic vascular diseases such as atherosclerosis, aneurysms, diabetic angiopathy/retinopathy as well as fibrotic and proliferative vascular diseases are generally complicated by the progression of degenerative insults, which are characterized by endothelial dysfunction, apoptotic/necrotic cell death in vascular/immune cells, remodeling of extracellular matrix or breakdown of elastic lamella. Increasing evidence suggests that dysfunctional calpain proteolytic systems and defective calpain protein metabolism in blood vessels contribute to degenerative disorders. In vascular endothelial cells, the overactivation of conventional calpains consisting of calpain-1 and -2 isozymes can lead to the disorganization of cell-cell junctions, dysfunction of nitric oxide synthase, sensitization of Janus kinase/signal transducer and activator of transcription cascades and depletion of prostaglandin I2, which contributes to degenerative disorders. In addition to endothelial cell dysfunctions, calpain overactivation results in inflammatory insults in macrophages and excessive fibrogenic/proliferative signaling in vascular smooth muscle cells. Moreover, calpain-6, a non-proteolytic unconventional calpain, is involved in the conversion of macrophages to a pro-atherogenic phenotype, leading to the pinocytotic deposition of low-density lipoprotein cholesterol in the cells. Here, we discuss the recent progress that has been made in our understanding of how calpain contributes to degenerative vascular disorders.

For three different types of angiogenesis models with variable delays, we consider either continuous or impulse therapy that eradicates tumor cells and suppresses angiogenesis. For the cancer-free solution, explicit conditions of global stability for the continuous and impulsive systems are obtained, together with delay-dependent estimates for the rates of decay for the tumor volume and pathological angiogenesis.

The extracellular matrix (ECM) is the central element of a pericellular network of bioactive molecules. It orchestrates molecular interactions, availability and activity, acting as a key regulator of cell functions and complex biological processes, including physiological and pathological angiogenesis. The ECM serves as a source of both stimulatory and inhibitory angiogenesis regulatory factors. The observation that several endogenous inhibitors of angiogenesis derive from the ECM proves its importance in physiological angiogenesis, and point to the ECM as a precious source of therapeutic agents for angiogenesis-driven diseases, including cancer growth and metastatic dissemination. This review focuses on the different approaches to exploit ECM molecules for designing tools for therapeutic inhibition or monitoring of pathological angiogenesis, with particular focus on antineoplastic therapy, and emphasis on peptides of ECM moieties and mimetic small molecules.

The vascular and nervous systems are organized with well defined and accurate networks, which represent the anatomical structure enabling their functions. In recent years, it has been clearly demonstrated that these two systems share in common several mechanisms and specificities. For instance, the networking properties of the nervous and vascular systems are governed by common cues that in the brain regulate axon connections and in the vasculature remodel the primitive plexus towards the vascular tree. Here, we summarize the role of semaphorins as a paradigmatic example of the role of axon guidance molecules in physiological and pathological angiogenesis. Finally, we discuss the presence in blood vessels of neurexin and neuroligin, two proteins that finely modulate synaptic activity in the brain. This observation is suggestive of an intriguing new class of molecular and functional parallels between neurons and vascular cells.

To unravel the normal vasculature transcriptome and determine how it is altered by neighbouring malignant cells, we compared gene expression patterns of endothelial cells derived from the blood vessels of eight normal resting tissues, five tumors and regenerating liver. Organ-specific endothelial genes were readily identified, including 27 from brain. We also identified 25 transcripts overexpressed in tumor versus normal endothelium, including 13 that were not found in the angiogenic endothelium of regenerating liver. Most of the shared angiogenesis genes have expected roles in cell cycle control, but those specific for tumor endothelium were primarily cell surface molecules of uncertain function. These studies reveal striking differences between physiological and pathological angiogenesis potentially important for the development of tumor-specific vascular targeted therapies.

ICS-283 was developed within Intradigm Corporation as a system that is designed for the systemic delivery of therapeutic small interfering (siRNA) to sites of pathological angiogenesis. The non-viral siRNA delivery system is based on synthetic nanoparticles, known as TargeTran™ (Intradigm Corporation), which functions as a broad-platform technology to deliver siRNA to specific target cells in diseased tissues. The system is constructed to incorporate different functionalities that address critical needs for successful nucleic acid delivery. The TargeTran synthetic vector is a self-assembling, layered nanoparticle that protects and targets siRNA to specific cell types in pathological tissues. At present, ICS-283 is the only antiangiogenic siRNA delivery system that is designed for intravenous administration to treat angiogenesis-driven diseases.

The first angiogenesis inhibitors for cancer have now been approved by the F.D.A. in the U.S. and in 28 other countries, including China. The majority of these are monotherapies that block VEGF. However, mutant tumor cells may over time produce redundant angiogenic factors. Therefore, for long-term use in cancer, combinations of angiogenesis inhibitors or broad spectrum angiogenesis inhibitors will be needed. The two most broad spectrum and least toxic angiogenesis inhibitors are Caplostatin and endostatin. Endostatin inhibits 65 different tumor types and modifies 12% of the human genome to downregulate pathological angiogenesis without side-effects. The recent discovery that small increases in circulating endostatin can suppress tumor growth and that orally available small molecules can increase endostatin in the plasma suggests the possible development of a new pharmaceutical field.

Inhibition of alphavbeta3 or alphavbeta5 integrin function has been reported to suppress neovascularization and tumor growth, suggesting that these integrins are critical modulators of angiogenesis. Here we report that mice lacking beta3 integrins or both beta3 and beta5 integrins not only support tumorigenesis, but have enhanced tumor growth as well. Moreover, the tumors in these integrin-deficient mice display enhanced angiogenesis, strongly suggesting that neither beta3 nor beta5 integrins are essential for neovascularization. We also observed that angiogenic responses to hypoxia and vascular endothelial growth factor (VEGF) are augmented significantly in the absence of beta3 integrins. We found no evidence that the expression or functions of other integrins were altered as a consequence of the beta3 deficiency, but we did observe elevated levels of VEGF receptor-2 (also called Flk-1) in beta3-null endothelial cells. These data indicate that alphavbeta3 and alphavbeta5 integrins are not essential for vascular development or pathological angiogenesis and highlight the need for further evaluation of the mechanisms of action of alphav-integrin antagonists in anti-angiogenic therapeutics.

Embryo establishes contact with the endometrium during implantation. Proper endometrial vascular development and maintenance at the time of embryo implantation is crucial for successful pregnancy. Vascular development at the maternal-embryo interface can be regulated by various cell types, of which uterine natural killer (uNK) cells play an important role. Abnormal angiogenesis and uNK cell number/function may lead to reproductive failure, particularly in women with recurrent miscarriage (RM) and women with recurrent implantation failure (RIF) after IVF-ET treatment, which are the important clinical hurdles in reproductive medicine to overcome. In this review, we aim to discuss the current knowledge of physiological angiogenic processes and the pathological angiogenesis at the time of implantation, as well as the possible mechanism and potential treatment.

Pathological angiogenesis is a hallmark of cancer and various ischaemic and inflammatory diseases. Concentrated efforts in this area of research are leading to the discovery of a growing number of pro- and anti-angiogenic molecules, some of which are already in clinical trials. The complex interactions among these molecules and how they affect vascular structure and function in different environments are now beginning to be elucidated. This integrated understanding is leading to the development of a number of exciting and bold approaches to treat cancer and other diseases. But owing to several unanswered questions, caution is needed.

The proangiogenic members of the vascular endothelial growth factor (VEGF) family and related receptors play a central role in the modulation of pathological angiogenesis. In order to identify plant compounds able to interfere in the VEGFs/VEGFR-1 (Flt-1) recognition by VEGF family members, the extracts of the aerial parts of Campsiandra guayanensis and Feretia apodanthera were screened by a competitive ELISA-based assay. By using this bioassay-oriented approach five proanthocyanindins, including the new natural compounds (2S)-4',5,7-trihydroxyflavan-(4?->8)-afzelechin (1) and (2S)-4',5,7-trihydroxyflavan-(4?->8)-epiafzelechin (2) and the known geranin B (3), proanthocyanidin A2 (4), and proanthocyanidin A1 (5), were isolated. The study of the antiangiogenic activities of compounds 1-5 using ELISA and SPR assays showed compound 1 as being the most active. The antiangiogenic activity of 1 was also confirmed in vivo by the chicken chorioallantoic membrane assay. Our results indicated 1 as a new antiangiogenic compound inhibiting the interaction between VEGF-A or PlGF and their receptor VEGRF-1.

Curcumin has long been used as an antioxidative, antiinflammatory, and modulator of pathological angiogenesis, whereas naringenin is a well-known immunomodulator. In this report, we investigated the effect of curcumin and naringenin on the growth of Ehrlich ascites carcinoma tumor model. To achieve this, Swiss albino mice were implanted intraperitoneally with 1 × 10⁶ Ehrlich ascites carcinoma cells followed by the administration of oral doses of naringenin and curcumin either individually (50 mg/kg body weight) or in combination (20 mg/kg body weight each). A marked reduction has been seen in the total number of cells (80%) and accumulation of ascetic fluid (55%) when these drugs were administered together. These drugs proved to be an effective angio-inhibitory compound and confirmed by different in vivo assay systems, viz. peritoneal/skin angiogenesis and chorioallantoic membrane assay. Antiangiogenic and antiproliferative effect of these compounds alone or in combination was further corroborated with immunoblot results where we confirmed the downregulation of vascular endothelial growth factor, Hif1α, heat shock protein 90, and p-Akt. Furthermore, treatment with naringenin and curcumin alone or in combination substantially improved hepatocellular architecture and no noticeable neoplastic lesions or cellular alteration were reported. These outcomes put forward a plausible clinical application of these diet-derived compounds, as both angioinhibitory and antitumor in association with conventional therapy.

Clinically detectable metastases represent an ultimate consequence of the metastatic cascade that consists of distinct processes including tumor cell invasion, dissemination, metastatic niche formation, and re-growth into a detectable metastatic mass. Although angiogenesis is known to promote tumor growth, its role in facilitating early events of the metastatic cascade remains poorly understood. We have recently developed a zebrafish tumor model that enables us to study involvement of pathological angiogenesis in tumor invasion, dissemination and metastasis. This non-invasive in vivo model allows detection of single malignant cell dissemination under both normoxia and hypoxia. Further, hypoxia-induced VEGF significantly facilitates tumor cell invasion and dissemination. These findings demonstrate that VEGF-induced pathological angiogenesis is essential for tumor dissemination and further corroborates potentially beneficial effects of clinically ongoing anti-VEGF drugs for the treatment of various malignancies.

Endothelial cell migration is an essential aspect of tumor angiogenesis. Rac1 activity is needed for cell migration in vitro implying a requirement for this molecule in angiogenesis in vivo. However, a precise role for Rac1 in tumor angiogenesis has never been addressed. Here we show that depletion of endothelial Rac1 expression in adult mice, unexpectedly, has no effect on tumor growth or tumor angiogenesis. In addition, repression of Rac1 expression does not inhibit VEGF-mediated angiogenesis in vivo or ex vivo, nor does it affect chemotactic migratory responses to VEGF in 3-dimensions. In contrast, the requirement for Rac1 in tumor growth and angiogenesis becomes important when endothelial beta3-integrin levels are reduced or absent: the enhanced tumor growth, tumor angiogenesis and VEGF-mediated responses in beta3-null mice are all Rac1-dependent. These data indicate that in the presence of alphavbeta3-integrin Rac1 is not required for tumor angiogenesis.

Angiogenesis is a physiologic process characterized by the sprouting of a new blood vessel from a pre-existing one. In mammalians the angiogenesis process is dormant, except for few physiological conditions such as wound healing and ovulation. In healthy individuals angiogenesis is finely tuned by pro- and anti-angiogenic factors. The shift from this equilibrium, under pathological conditions (pathological angiogenesis) is associated with several human diseases of high social impact. An efficient angiogenesis also requires that angiogenic factors cooperate with microenvironment derived co-factors, including metals. In this Perspective we describe the bioinorganic aspects of angiogenesis which contribute to a better understanding of the molecular mechanisms and regulation of angiogenesis. In particular, the role of metals, especially copper, metalloproteinases, and the current status on the imaging of angiogenesis targeting VEGF or VEGF receptors will be discussed.

New blood vessel growth via angiogenesis is a fundamental process in both physiological and pathological conditions. Physiological angiogenesis is critical during embryogenesis and placental development, whereas pathological angiogenesis plays an important role in the progression of many diseases, most notably tumor growth. Tumor angiogenesis is well accepted to be regulated by a balance of proangiogenic and antiangiogenic factors produced both by tumor cells and surrounding stromal cells. For many years, investigation of antiangiogenic therapies for cancer has focused on the proangiogenic cytokine, vascular endothelial growth factor; its receptors; or downstream signaling pathways. However, more recently with the identification of endogenous angiogenesis inhibitors, studies have turned toward understanding the role of endogenous antiangiogenic proteins in preventing disease progression. Clinical clues have suggested that specific populations may have dysregulated angiogenesis due to differential expression of endogenous angiogenesis regulators. For example, individuals with Down syndrome may possess a systemic antiangiogenic state with a significantly decreased incidence of angiogenesis-dependent diseases. Our work suggests that endogenous angiogenesis inhibitors may be the master regulators controlling progression of angiogenesis-dependent diseases such as vascular anomalies and cancer. The molecular regulation of angiogenesis is not yet fully understood; however, the Down syndrome population may give us insights toward novel therapies for controlling angiogenesis in disease.

An understanding of the mechanisms regulating growth and differentiation of vascular endothelial cells is very important for cardiovascular biology and medicine. Several potential regulators of angiogenesis have been identified, including acidic and basic fibroblast growth factors, epidermal growth factor, platelet-derived endothelial cell growth factor, transforming growth factors α and β, and tumor necrosis factor α (TNF-α). Vascular endothelial growth factor (VEGF) is unique among these agents by virtue of its direct and specific mitogenic effects on endothelial cells combined with the fact that it is a secreted polypeptide. By alternative splicing of mRNA, VEGF may exist in four different isoforms that have similar biologic activities but differ markedly in their secretion pattern. VEGF is emerging as an important regulator of developmental and ovarian angiogenesis. Its action is purely paracrine as it is produced by a variety of cell types, but its receptors are only in endothelial cells. There is no evidence that endothelial cells in vivo produce VEGF. The VEGF mRNA is expressed at high level by a variety of human tumors, suggesting that VEGF may be a tumor angiogenesis factor. This hypothesis is supported by the finding that monoclonal antibodies specific for VEGF are able to suppress tumor growth in vivo. Therefore, VEGF antagonists may be used for the treatment of malignancies and, possibly, other angiogenic diseases. The VEGF protein has therapeutic potential as an inducer of neovascularization in conditions characterized by impaired tissue perfusion like obstructive atherosclerosis.