【In Press】Autophagy: a potential target for the treatment of intraocular neovascularization

The formation of neovascularization is a common pathological feature of many ocular vascular diseases, and is an important cause of vision loss in patients. Neovascularization can cause retinal hemorrhage, vitreous hemorrhage, and other serious complications, leading to loss of vision. The treatment of intraocular neovascularization is the focus of Ophthalmology research. In recent years, some studies have found that autophagy is closely related to vascular endothelial growth factor (VEGF) and the formation of neovascularization. Autophagy is expected to become a new target for the treatment of intraocular neovascularization. Therefore, this article reviews the research on autophagy and the formation of intraocular neovascularization.     

Autophagy: a potential target for the treatment of intraocular neovascularization

The formation of neovascularization is a common pathological feature of many ocular vascular diseases, and is an important cause of vision loss in patients. Neovascularization can cause retinal hemorrhage, vitreous hemorrhage, and other serious complications, leading to loss of vision. The treatment of intraocular neovascularization is the focus of ophthalmology research. In recent years, some studies have found that autophagy is closely related to vascular endothelial growth factor and the formation of neovascularization. Autophagy is expected to become a new target for the treatment of intraocular neovascularization. Therefore, this article reviews the research on autophagy and the formation of intraocular neovascularization.     

Angiogenesis and retinal diseases

Angiogenesis is the process involving the growth of new blood vessels from preexisting vessels which occurs in both physiologic and pathological settings. It is a complex process controlled by a large number of modulating factors, the pro-and antiangiogenic factors. The underlying cause of vision loss in proliferative retinal diseases, such as age-related macular degeneration and proliferative diabetic retinopathy, are increased vascular permeability and choroidal neovascularization, and vascular endothelial growth factor (VEGF) plays a central role in this process. VEGF is produced in the eye by retinal pigment epithelium (RPE) cells and is upregulated by hypoxia. There are four major biologically active human isoforms, of which VEGF165 is the predominant in the human eye and appears to be the responsible for pathological ocular neovascularization. Besides being a potent and specific mitogen for endothelial cells, VEGF increases vascular permeability, inhibits endothelial cells apoptosis, and is a chemoattractant for endothelial cell precursors. VEGF is not the only growth factor involved in ocular neovascularization. Basic fibroblast growth factor (bFGF), angiopoietins, pigment epithelium-derived factor (PEDF), and adhesion molecules also play a role in the pro- and antiangiogenic balance. Advances in the understanding of the bases of pathological ocular angiogenesis and identification of angiogenesis regulators have enabled the development of novel therapeutic agents. Anti-VEGF antibodies have been developed for intravitreal use, and other approaches are currently under investigation. These new drugs may be powerful tools for the treatment of the leading causes of irreversible blindness in people over age 65.     

Retinal vascular development is mediated by endothelial filopodia,a preexisting astrocytic template and specific R-cadherin adhesion

PURPOSE: A neonatal mouse retina developmental model was used to study endothelial cell guidance and subsequent formation of vascular patterns. Since most diseases that cause catastrophic loss of vision do so as a result of abnormal ocular angiogenesis, a better understanding of events regulating normal retinal vascular growth may provide insight into pathologic angiogenesis. METHODS: Development of the retinal vasculature at various postnatal and embryonic time points was analyzed by collagen IV immunohistochemistry and staining with isolectin Griffonia simplicifolia. GFAP-GFP transgenic mice were used to evaluate the relationship between developing vessels and retinal glial cells. Immunolocalization of R-cadherin and intravitreous injection of R-cadherin-specific antibodies was performed to determine the role of R-cadherin during patterning of the superficial and deep retinal vascular plexuses. RESULTS: The characteristic honeycomb pattern of vessel formation observed in the superficial layer is a result of endothelial cell migration over a preexisting astrocytic template. Filopodial extensions associate with underlying astrocytes by protruding from the tips of endothelial cells at the migrating vascular front. Branching of vessels in the primary vascular plexus, as well as appropriate localization of the deep vascular network is mediated by R-cadherin, an adhesion molecule known to be involved in neuronal cell guidance. Injection of antibodies directed against R-cadherin prevents the normally extensive collateralization observed during formation of the superficial network. Injection of anti-R cadherin antibodies also dramatically affects vessels of the deep network. These vessels migrate beyond the normal turning point, penetrating into the deeper photoreceptor layer. CONCLUSIONS:. These studies suggest that angiogenesis and formation of vascular patterns in the retina may use many of the same developmental cues used by neurons in both the central and peripheral nervous systems. Furthermore, retinal vascular endothelial cell guidance mediated by filopodial extensions and neuronal guidance cues may represent a novel conceptual framework within which to study the establishment of vascular patterns in a variety of angiogenic systems.     

Role of vascular endothelial growth factor in ocular angiogenesis

VEGF-A is a critical regulator of ocular angiogenesis and vascular permeability and is involved in the pathogenesis of several ocular diseases involving neovascularization or increased vascular permeability, such as neovascular AMD, diabetic ME, and diabetic retinopathy. Currently available therapies for neovascular AMD, such as laser photocoagulation, PDT with verteporfin, and pegaptanib sodium, slow visual loss but do not improve vision for most patients. In contrast, an emerging anti-VEGF agent, ranibizumab, improved vision in 25% to 34% of treated patients in one clinical trial, rather than slowing visual loss and is the first treatment for neovascular AMD to demonstrate visual improvement in a substantial number of patients. This represents a major advance in the treatment of ocular diseases involving neovascularization or increased vascular permeability and provides hope to patients with these debilitating diseases. Since the submission of this article, ranibizumab was approved by the FDA for the treatment of neovascular AMD.     

The unfolded protein response in retinal vascular diseases: Implications and therapeutic potential beyond protein folding

Angiogenesis is a complex, step-wise process of new vessel formation that is involved in both normal embryonic development as well as postnatal pathological processes, such as cancer, cardiovascular disease, and diabetes. Aberrant blood vessel growth, also known as neovascularization, in the retina and the choroid is a major cause of vision loss in severe eye diseases, such as diabetic retinopathy, age-related macular degeneration, retinopathy of prematurity, and central and branch retinal vein occlusion. Yet, retinal neovascularization is causally and dynamically associated with vasodegeneration, ischemia, and vascular remodeling in retinal tissues. Understanding the mechanisms of retinal neovascularization is an urgent unmet need for developing new treatments for these devastating diseases. Accumulating evidence suggests a vital role for the unfolded protein response (UPR) in regulation of angiogenesis, in part through coordinating the secretion of pro-angiogenic growth factors, such as VEGF, and modulating endothelial cell survival and activity. Herein, we summarize current research in the context of endoplasmic reticulum (ER) stress and UPR signaling in retinal angiogenesis and vascular remodeling, highlighting potential implications of targeting these stress response pathways in the prevention and treatment of retinal vascular diseases that result in visual deficits and blindness.     

Ocular angiogenesis: the role of growth factors

Ocular angiogenesis, the formation of new vessels from the existing vascular tree, is a major cause of severe vision loss. It can affect different structures in the eye, including the retina, choroid and cornea. During the last decade our knowledge in the mechanisms underlying ocular angiogenesis has increased dramatically. We have witnessed the identification of key molecules. Many are classified as growth factors due to their biological properties, regulating angiogenesis. This knowledge has propelled the development of a new group of therapeutic tools, the antiangiogenic agents. This review gives an update on the role of growth factors in ocular angiogenesis from both a basic and a clinical perspective.     

Peripheral retinal neovascularization in talc retinopathy.

BACKGROUND: Neovascularization of the peripheral retina can be present in a number of systemic and ocular diseases. Very rarely, peripheral retinal neovascularization can also be manifested in intravenous drug abusers. In addition to ocular complications, intravenous drug abusers are at high risk for contracting various infections and the development of pulmonary and cardiovascular diseases. We present a case of a chronic heroin and cocaine abuser with bilateral peripheral retinal neovascularization, pulmonary complications, and a history of endocarditis. CASE REPORT: A patient with a 20-year history of heroin and cocaine abuse initially presented for a routine eye examination. Fundus examination revealed pinpoint white deposits centered in both maculas, engorged vascular fronds with a patch of intraretinal hemorrhage in the peripheral retinal of the right eye and neovascularization of the disc as well as exudation with adjacent focal preretinal hemorrhage in the left eye. The patient underwent fluorescein angiography and was screened for diabetes, sarcoidosis, and sickle cell disease. When no systemic disease could be discovered, it was concluded that the peripheral retinal neovascularization developed as a result of vascular occlusion from heroin and cocaine abuse. DISCUSSION: It is important to investigate the cause of neovascularization in the peripheral retina. Retinal vascular emboli such as talc are common in drug abusers, but in most cases, the retinal deposits pose only a minimal threat to vision. However, this case shows that careful retinal examination is warranted in drug abusers to rule out neovascularization of the retina. Other causes of peripheral retinal neovascularization should be ruled out as well. These conditions include sickle cell retinopathy, sarcoidosis, diabetic retinopathy, blood dyscrasias, retinal vascular occlusion, Eales' disease, and other systemic conditions, so that appropriate ocular and systemic treatment can be provided. Peripheral retinal neovascularization is best treated by pan-retinal photocoagulation.     

Three-dimensional in vivo imaging of the mouse intraocular vasculature during development and disease

PURPOSE: Aberrant growth of blood vessels in the eye is a major cause of vision loss, occurring as a complication of diabetic retinopathy, age-related macular degeneration, and retinal vascular occlusions, among others. Whereas in humans, in vivo angiography is routinely used to image such diseases, many animal models of ocular vascular disease and development rely on dissected tissues that may not accurately represent in vivo conditions and require enucleation of the eye, the death of the animal, or both. METHODS: A method of three-dimensional imaging of blood vessels was used in the living mouse eye that involved scanning laser confocal microscopy and computer-aided image reconstruction. RESULTS: This minimally invasive technique was used to collect three-dimensional images of intraocular vessels in vivo during development. The retinal and choroidal vasculature was studied during development and disease, in models of retinal degeneration, central retinal vein occlusion, and oxygen-induced retinopathy. To aid in investigations into cell-based therapies for retinal disease, two-color imaging was used to localize transplanted cells in relation to the vasculature. This technique was used to perform serial imaging of the ocular vasculature over time, when developmental regression of vessels was observed. CONCLUSIONS: This in vivo vascular imaging approach is valuable in monitoring normal development, disease progression, and efficacy of experimental treatments in mouse models of ocular vascular disease and may have broader applications to the field of angiogenesis by using the readily visualized ocular vascular bed as a surrogate to test pro- and antiangiogenic compounds.     

Suppressed expression of tubedown-1 in retinal neovascularization of proliferative diabetic retinopathy.

PURPOSE: Retinal neovascularization occurring as a complication of diabetes mellitus can cause vision loss and blindness. The identification and study of novel genes involved in retinal angiogenesis may define new targets to suppress retinal neovascularization in diabetes and other ocular diseases. A novel acetyltransferase subunit, tubedown-1 (tbdn-1), has been isolated, the expression of which is regulated during blood vessel development. Tbdn-1 is not detected in most adult vascular beds but persists at high levels in the adult ocular vasculature. The purpose of this study was to gain insight into the possible role of tbdn-1 in retinal blood vessels by characterizing its expression patterns in adult homeostasis and in retinal neovascularization associated with diabetes. METHODS: Western blot analysis and immunohistochemistry were performed to study the expression patterns of tbdn-1 during adult homeostasis in normal human retinas, in a model of choroid-retina endothelial capillary outgrowth in vitro, and in retinas showing neovascularization in patients with proliferative diabetic retinopathy (PDR). RESULTS: In adults during homeostasis, tbdn-1 was expressed highly in normal endothelium of retinal and limbic blood vessels. Tbdn-1 was also expressed in RF/6A, a rhesus macaque choroid-retina-derived endothelial cell line. In an in vitro model system using the RF/6A cell line, tbdn-1 expression was downregulated during the outgrowth of these cells into capillary-like structures on a reconstituted basement membrane matrix. Similar to this in vitro model, tbdn-1 expression is specifically suppressed in the endothelial cells of blood vessels and capillary fronds in vivo in both the neural retinal tissue and in preretinal membranes in eyes of patients with PDR. CONCLUSIONS: High levels of expression of tbdn-1 are associated with ocular endothelial homeostasis in adults. Conversely, low levels of tbdn-1 expression are associated with endothelial capillary outgrowth in vitro and retinal neovascularization in vivo. Because the tbdn-1 acetyltransferase subunit is a member of a family of regulatory enzymes that are known to control a range of processes, including cell growth and differentiation, through posttranslational modification, the current results support a hypothesis that tbdn-1 may be involved in maintaining homeostasis and preventing retinal neovascularization.     

Inhibition of retinal neovascularization by soluble EphA2 receptor

Eph receptor tyrosine kinases (RTKs) and their ligands, known as ephrins, play an important role in vascular remodeling during embryogenesis, but their functions in adult angiogenesis are just beginning to be investigated. In this report, we investigated the effect of blocking EphA receptor activation on VEGF-induced angiogenic responses of cultured retinal endothelial cells and on retinal neovascularization in a rodent model of retinopathy of prematurity (ROP). Soluble EphA2-Fc receptors inhibited ephrin-A1 ligand or VEGF-induced BRMEC migration and tube formation without affecting proliferation in vitro. Since EphA2-Fc receptors can inhibit activation of multiple EphA receptors, the specific role of EphA2 receptor in angiogenesis was further investigated in EphA2-deficient endothelial cells. Loss of EphA2 in endothelial cells leads to defective cell migration and assembly in response to either ephrin-A1 or VEGF. Finally, a significant reduction in the severity of abnormal retinal neovascularization was observed in the eyes treated with soluble EphA2-Fc receptors, yet the normal total retinal vascular area was not significantly changed. Because soluble Eph receptor significantly inhibited pathologic retinal angiogenesis without affecting normal intraretinal vessels, it may be a promising agent for treatment of retinal angiogenesis in a number of human ocular diseases.     

Peripheral proliferative retinopathies

Peripheral retinal neovascularization (i.e., new vessel growth peripheral to the major vascular arcades) may be secondary to a wide variety of ocular and systemic diseases. Vascular and inflammatory diseases in particular may cause peripheral neovascularization. Following a brief review of ocular angiogenesis, the various clinical entities that can cause peripheral retinal neovascularization are described. The diagnostic workup of a patient with peripheral proliferative retinopathy is outlined and techniques of treatment of the neovascularization (including feeder vessel technique, cryopexy, and panretinal photocoagulation) are discussed.     

视网膜新生血管抑制因子的研究进展

血管的正常生长是血管组织中促生长因子和抑制因子相互协调达到动态平衡的结果,但是当这种平衡被打破后,就会诱发新生血管的生长.内源性的新生血管抑制因子,是一组机体自身产生的抑制血管生成的负反馈分子,其产生血管抑制的作用主要是通过影响促新生因子与其受体或其下游促增生信号结合,或者自身促进内皮凋亡而实现的.血管新生抑制因子的研究对于防治眼底视网膜新生血管生长具有潜在的临床意义.本文就视网膜新生血管抑制因子的最新研究进展进行系统综述.     

Retinal and choroidal angiogenesis: pathophysiology and strategies for inhibition

Retinal angiogenesis and choroidal angiogenesis are major causes of vision loss, and the pathogenesis of this angiogenesis process is still uncertain. However, several key steps of the angiogenic cascade have been elucidated. In retinal angiogenesis, hypoxia is the initial stimulus that causes up regulation of growth factors, integrins and proteinases, which result in endothelial cell proliferation and migration that are critical steps in this process. Once the endothelial tube is formed from the existing blood vessels, maturation starts with recruitment of mural cell precursors and formation of the basement membrane. Normally, there is a tight balance between angiogenic factors and endogenous angiogenesis inhibitors that help to keep the angiogenic process under control. Although the steps of choroidal angiogenesis seem to be similar to those of retinal angiogenesis, there are some major differences between these two processes. Several anti-angiogenic approaches are being developed in animal models to prevent ocular angiogenesis by blocking the key steps of the angiogenic cascade. Based on these pre-clinical studies, several anti-angiogenic clinical trials are ongoing in patients with diabetic retinopathy and age-related macular degeneration. This review discusses the pathogenesis of retinal and choroidal angiogenesis, and alternative pharmacological approaches to inhibit angiogenesis in ocular diseases.     

Normal and pathological mechanisms in retinalvascular development

Angiogenesis is a complex biologic process that occurs normally in development and in turnover and remodeling of mature vascular networks. Pathological angiogenesis and neovascularization occur in association with retinal and ocular ischemic diseases, in retinopathy of prematurity and other developmental disorders, and in tumor growth and metastasis. We describe current understanding of cellular and molecular mechanisms of retinal vascular development, highlighting aspects that relate to eye diseases, that provide sites of therapeutic intervention in ophthalmology and that are potential avenues for research.     

Application of optical coherence tomography angiography in ocular anterior segment diseases北大核心CSCD

Optical coherence tomography angiography (OCTA) is a rapid, noninvasive new blood flow imaging technique that was first applied to retinal retinopathy and acquired retinal vascular imaging in only a few seconds. Compared with the traditional optical coherence tomography(OCT), OCTA analyze has the advantages of higher resolution, faster scanning speed, quantitative blood flow, etc. OCTA not only can more accurately and qualitatively analyze ocular vascular morphology, but also can measure blood vessels and blood flow perfusion noninvasively and quantitatively. With the application of anti angiogenesis drugs in the anterior segment, it is important to evaluate the neovascularization of the cornea and iris in order to guide the clinical medication and evaluate the therapeutic effect. This article reviewed the application of OCTA in ocular anterior segment diseases, such as cornea and iris diseases, etc. Copyright © 2018 by the Chinese Medical Association.     

Ranibizumab治疗脉络膜新生血管的研究现状

脉络膜新生血管(choroidal neovascularization,CNV)是引起多种眼底疾病、导致视力丧失的重要原因之一。CNV的发生机制尚不清楚,目前普遍认为血管生成因子与抑制因子之间平衡的破坏具有关键作用,而血管内皮生长因子(vascular endothelial growth factor,VEGF)是其重要的始动因素。Ranibizumab是一种重组的人源化抗VEGF单克隆抗体片段,能够结合并抑制VEGF,阻止血管渗漏和新生血管的形成,抑制CNV的发生,进而阻碍CNV相关疾病的病程进展。随着对CNV发生机制的深入研究,针对CNV发生过程进行治疗,有可能从根本上治愈CNV相关疾病。     

Ocular vasodilation and angiogenesis in Potter's syndrome

At autopsy we examined eight eyes of six infants with Potter's syndrome, an idiopathic multisystem condition with a constellation of ocular anomalies, to explore its ocular component more fully and systematically. A striking abnormality in some cases was the presence of dilated intraocular blood vessels, and these were sometimes associated with retinal and preretinal neovascularization reminiscent of the vasoproliferative stage of retrolental fibroplasia. Since oxygen therapy cannot be implicated in these cases, other causes, either genetic or environmental, must be sought. The presence of nonretinal ocular vascular anomalies, such as iris capillary dilation, peripapillary angioma formation, and vascular anomalies in nonocular tissue, point to a generalized derangement in the control of ocular angiogenesis. Our study indicated that an understanding of the pathogenesis of the vascular anomalies in Potter's syndrome is clearly relevant to other more common retinopathies that are associated with neovascularization.     

SOLITARY SILENT VENOUS PAPILLARY LOOPS AND OCULAR HYPERTENSION

A series of 24 eyes in 23 patients is described showing solitary silent venous papillary loops. These loops are usually associated with a considerable degree of ocular hypertension, presenting when this hypertension is being investigated. They are silent, usually with no previous ocular history, single with a large diameter, affecting veins at the optic disc and not extending into the vitreous. The optic disc is cupped, but usually not more than 0.6 disc diameter, there is good central vision and either a full visual field or only early field loss. Fluorescein angiography shows the loops to be competent with no evidence of any other retinal vascular abnormality. Rarely loss of central vision may occur due to progression to advanced glaucoma. The condition is distinct from prepapillary vascular arterial papillary loops, neovascularization at the optic disc and optociliary shunt vessels. It is also distinct from the venous collateral vessels which develop at the optic disc after acute central or branch retinal vein occlusion. These collaterals are usually multiple, the accompanying ocular hypertension is of lesser degree, cupping of the disc and field loss are usually much more advanced and, while visual acuity may be normal, it is often grossly reduced. On fluorescein angiography all these cases of venous collaterals after retinal vein occlusion showed evidence of other retinal vascular dysfunction. Solitary silent venous papillary loops appear to develop from venules on the optic disc as a bypass to a low grade venous occlusion which is seldom clinically manifest. They form a distinct entity with a good prognosis if the accompanying ocular hypertension is carefully controlled.