Vascular endothelial growth factor and its inhibitor in age-related macular degeneration

Intraocular angiogenesis is considered the leading cause for severe loss of vision, and contributes to many ocular diseases such as neovascular age-related macular degeneration, diabetic retinopathy, and retinopathy of prematurity, the main causes of blindness in developed countries.¹ An enormous body of work has demonstrated that vascular endothelial growth factor (VEGF) plays a prominent role as mediator in the procedure of pathological angiogenesis. This makes VEGF a potential target for the medical therapies of retinal angiogenesis and some clinical trials have proved the efficacy of anti-VEGF strategies. This review evaluates the role of VEGF in the pathogenesis of age-related macular degeneration and provides an overview of recent developments in therapeutic modalities.     

阿柏西普在眼科疾病治疗中的应用

阿柏西普是一种与血管内皮生长因子-A、B及胎盘生长因子特异性结合的人源化重组融合蛋白,其通过降低血管内皮通透性进而抑制新生血管生成,在病理性血管形成过程中扮演重要角色。近年来,该药在医学领域的应用范围不断扩大,在结直肠癌、卵巢癌、糖尿病性黄斑水肿、老年性黄斑变性、视网膜静脉阻塞及早产儿视网膜病变等治疗中均被广泛应用,并取得较好效果。本文旨在综述阿柏西普的药理学特点及其在眼科疾病中的应用现状、治疗优势,为后续药物研究和临床应用提供更多的治疗策略。     

抗VEGF药物在视网膜血管性疾病围手术期的应用

血管内皮生长因子（VEGF）与新生血管性眼病密切相关,是有效的治疗靶点.抗VEGF药物能减少新生血管形成,降低血管通透性,为新生血管性眼病的治疗带来重大变革.目前雷珠单抗在国内已被批准用于湿性年龄相关性黄斑变性的治疗,在美国被批准用于糖尿病性黄斑水肿和视网膜静脉阻塞后黄斑水肿的治疗.抗VEGF药物也作为适应证外治疗药物用于其他新生血管性眼病的治疗,如增生性糖尿病视网膜病变、其他视网膜血管性疾病和新生血管性青光眼等.抗VEGF药物辅助手术治疗显示出明显的疗效,可减少术中、术后的并发症和疾病的复发率.就贝伐单抗和雷珠单抗等抗VEGF药物在视网膜血管性疾病围手术期的应用情况进行综述.     

色素上皮细胞衍生因子基因治疗视网膜及脉络膜新生血管性疾病研究进展

色素上皮细胞衍生因子（pigment epithelium—derived factor，PEDF）是一种相对分子质量为50000的分泌蛋白，属于丝氨酸超家族的一员。近年来研究发现PEDF具有多种生物学功效，包括抗新生血管，神经营养及神经保护功能。PEDF是最有效的内源性眼部新生血管抑制物。PEDF对于治疗血管增生性疾病及视网膜变性性疾病具有广阔的前景，基因转移为眼内组织治疗药物的持续传递提供了有效途径。就近年来关于PEDF基因治疗视网膜及脉络膜疾病的研究进展给以综述。     

Pegaptanib sodium for ocular vascular disease

Pegaptanib sodium (Macugen) is a selective RNA aptamer that inhibits vascular endothelial growth factor (VEGF) 165 , the VEGF isoform primarily responsible for pathologic ocular neovascularization and vascular permeability, while sparing the physiological isoform VEGF 121 . After more than 10 years in development and preclinical study, pegaptanib was shown in clinical trials to be effective in treating choroidal neovascularization associated with age-related macular degeneration. Its excellent ocular and systemic safety profile has also been confirmed in patients receiving up to three years of therapy. Early, well-controlled studies further suggest that pegaptanib may provide therapeutic benefit for patients with diabetic macular edema, proliferative diabetic retinopathy and retinal vein occlusion. Notably, pegaptanib was the first available aptamer approved for therapeutic use in humans and the first VEGF inhibitor available for the treatment of ocular vascular diseases.     

骨桥蛋白与眼部新生血管性疾病研究进展

眼部新生血管是眼部疾病中致盲的主要原因之一.常见的致盲眼病,如糖尿病视网膜病变、年龄相关性黄斑变性、感染性角膜炎等均与新生血管存在一定的关系.骨桥蛋白（OPN）是一种能够促进血管再生与组织修复的糖蛋白,在角膜、脉络膜和视网膜新生血管中表达增多,能够促进新生血管的发生.OPN与新生血管的关系为新生血管性疾病的研究和治疗提供了新的方向.从OPN促进角膜新生血管、脉络膜新生血管、视网膜新生血管生成3个方面对OPN与眼部新生血管性疾病的关系研究进展进行综述.     

血管内皮生长因子 A的选择性剪接与眼内新生血管的生成

眼内新生血管的生成是多种眼病致盲的重要原因.血管内皮生长因子A(VEGF-A)家族是促进眼内新生血管生成的关键因素,其通过调控病理性血管的发生和增加血管的通透性而起作用.VEGF-A依选择性剪接方式的不同,可形成2个蛋白家族,分别是具有促血管生成作用的VEGFxxx家族和具有抗血管生成作用的VEGFxxxb家族.VEGFxxxb家族蛋白在正常眼组织中均有表达,而在糖尿病性视网膜病变患者的眼组织中表达水平降低.VEGF165b是VEGFxxxb家族中最早分离出来且研究最为广泛的分子结构,其可以明显抑制视网膜前新生血管的生成,而对视网膜生理性血管的发生无抑制作用.随着对VEGFxxxb家族研究的逐步深入,选择性剪接调节VEGFxxx与VEGFxxxb两者之间的平衡,可作为糖尿病性视网膜病变、年龄相关性黄斑变性等眼内新生血管性疾病的治疗新策略.     

血管内皮生长因子 A的选择性剪接与眼内新生血管的生成

眼内新生血管的生成是多种眼病致盲的重要原因.血管内皮生长因子A(VEGF-A)家族是促进眼内新生血管生成的关键因素,其通过调控病理性血管的发生和增加血管的通透性而起作用.VEGF-A依选择性剪接方式的不同,可形成2个蛋白家族,分别是具有促血管生成作用的VEGFxxx家族和具有抗血管生成作用的VEGFxxxb家族.VEGFxxxb家族蛋白在正常眼组织中均有表达,而在糖尿病性视网膜病变患者的眼组织中表达水平降低.VEGF165b是VEGFxxxb家族中最早分离出来且研究最为广泛的分子结构,其可以明显抑制视网膜前新生血管的生成,而对视网膜生理性血管的发生无抑制作用.随着对VEGFxxxb家族研究的逐步深入,选择性剪接调节VEGFxxx与VEGFxxxb两者之间的平衡,可作为糖尿病性视网膜病变、年龄相关性黄斑变性等眼内新生血管性疾病的治疗新策略.     

胎盘生长因子在新生血管性眼病中的研究进展

新生血管是许多致盲性眼病的主要原因,例如糖尿病视网膜病变、早产儿视网膜病变、年龄相关性黄斑变性等。血管内皮生长因子( vascular endothelial growth factor, VEGF)在新生血管的形成中起着重要的作用,被认为是作用最强的血管生长因子。胎盘生长因子( placental growth factor, PlGF)是VEGF家族中的一员,可促进新生血管生成,刺激内皮细胞迁移增殖,介导免疫炎症反应,且特异性表达于病理性新生血管,但在正常血管中不表达。因此近年来PlGF逐渐受到人们关注。本文对PlGF在新生血管性眼病中的作用机制进行探讨。     

Targeting angiogenesis, the underlying disorder in neovascular age-related macular degeneration

Angiogenesis has a causal role in many diseases, including neovascular age-related macular degeneration (AMD). Identification of key regulators of angiogenesis, including vascular endothelial growth factor (VEGF), fibroblast growth factor 2, pigment epithelium-derived growth factor, angiopoietins and extracellular matrix molecules, has facilitated the development of novel therapeutic agents that target the underlying pathological angiogenic process. Among these, VEGF serves as a "master switch" for many ocular neovascular conditions through its promotion of endothelial cell proliferation and survival, vascular permeability and ocular inflammation. Two anti-VEGF agents are now clinically available: bevacizumab, an antibody for metastatic colorectal cancer, and pegaptanib sodium, an aptamer for neovascular AMD. Unlike bevacizumab, which binds all VEGF isoforms, pegaptanib targets only VEGF165, the isoform responsible for pathological ocular neovascularization and thus an ideal target for treatment of AMD. Although other therapies targeting angiogenesis in AMD are in clinical development, to date, pegaptanib is the only therapy approved by the Food and Drug Administration of the United States for the treatment of all neovascular AMD and represents a valuable addition to the hitherto limited options available for patients.     

Aging and retinal vascular diseases

Ocular vascular diseases such as diabetic retinopathy, retinal vein occlusion, and age-related macular degeneration, whose population increases along with aging, have become leading causes of severe visual disturbance. Macular edema and serous retinal detachment are associated with abnormal vascular leakage and tractional retinal detachment, and neovascular glaucoma is caused by retinal neovascularization. Such ocular vascular diseases are caused by vascular cell aging and vascular damage associated with lifestyle-related diseases including diabetes mellitus, hypertension, hyperlipidemia, and obesity. In the present study, we investigated molecular mechanisms in such vascular deficiencies using vascular cell biology methodology, and we propose novel strategies for the treatment of such vascular diseases. Along with aging, oxidative stress and physical stress, such as mechanical stretch, continuously and directly insult vascular cells. Such stress induces apoptosis by intracellular signaling through stress kinases in cultured retinal vascular cells. Inhibition of such stress kinases could be an effective treatment to protect the vascular cells against age-related damage. In a retinal vascular developmental model, pericyte loss causes pathology mimicking macular edema and proliferative diabetic retinopathy. Angiopoietin 1 (Ang 1) secreted by pericytes suppresses oxidative stress-induced intracellular signaling through stress kinases linked to cell apoptosis and normalizes such retinal pathology. This suggests that the paracrine action of Ang 1 in the pericytes is necessary to sustain normal retinal vasculature, and that Ang 1-triggered intracellular signaling is useful for the treatment of vascular cell pathology associated with pericyte loss. In diabetic retinopathy and retinal vein occlusion, retinal vessels regress along with retinal vascular cell apoptosis, and the retina becomes ischemic followed by pathological retinal neovascularization. VEGF has been recognized as a predominant factor to induce the ischemic retinal neovascularization. We found that retinal vascular cells have a characteristic pattern in VEGF receptor expression, which causes vascular pathology more frequently in the retina than in other organs. Neuropilin 1 (NRP 1), which enhances VEGF receptor function, is abundantly expressed in the retinal endothelial cells and is upregulated by VEGF itself and by hypoxia to regulate a positive feedback mechanism in retinal neovascularization. This receptor could be a unique target for retina-specific therapy. Lifestyle-related diseases increase along with aging and have further increased due to changes in Japanese lifestyle imitating that of Western countries. We found that the renin-angiotensin system which regulates hypertension and cardiovascular diseases, and adipocytokines which are abnormally secreted in obesity, act as proangiogenic factors. Regulation of such lifestyle-related disease factors is important for the treatment of retinal vascular diseases. Finally, we found that erythropoietin is an ischemia-induced angiogenic factor that acts independently and as potently as VEGF in proliferative diabetic retinopathy (PDR). Our study utilizing human vitreous samples demonstrates that the VEGF level is particularly high and strongly associated with angiogenic activity in PDR patients. The potential of VEGF inhibitors has recently been recognized in clinical applications. The manipulation of each angiogenic factor and adipocytokine that we report here could become potential therapy in the near future.     

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.     

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.     

糖尿病视网膜血管病变中未折叠蛋白反应:蛋白质折叠的意义和治疗潜力

血管生成是由多因素共同参与调节,涉及正常的胚胎发育以及出生后的一种复杂的病理过程,如癌症、心血管疾病和糖尿病。而糖尿病视网膜病变（diabetic retinopathy,DR）则是眼科疾病中常见的糖尿病微血管病变,其中视网膜和脉络膜异常的血管生长是导致视力丧失的主要原因,它与血管变性、缺血、视网膜组织血管重构互为因果并动态关联。了解视网膜新生血管的机制,研发具有创新性的治疗方案是今后努力的方向。越来越多的证据表明,未折叠蛋白反应（unfold protein response,UPR）在调节血管生成方面扮演着非常重要的角色。本文总结了目前在视网膜内质网中的UPR相关研究以及UPR在DR新生血管形成和血管重构的信号,强调这些应激反应途径在预防和治疗导致视力缺陷和失明的DR中的潜在意义。     

血管内皮生长因子 A的选择性剪接与眼内新生血管的生成

眼内新生血管的生成是多种眼病致盲的重要原因.血管内皮生长因子A(VEGF-A)家族是促进眼内新生血管生成的关键因素,其通过调控病理性血管的发生和增加血管的通透性而起作用.VEGF-A依选择性剪接方式的不同,可形成2个蛋白家族,分别是具有促血管生成作用的VEGFxxx家族和具有抗血管生成作用的VEGFxxxb家族.VEGFxxxb家族蛋白在正常眼组织中均有表达,而在糖尿病性视网膜病变患者的眼组织中表达水平降低.VEGF165b是VEGFxxxb家族中最早分离出来且研究最为广泛的分子结构,其可以明显抑制视网膜前新生血管的生成,而对视网膜生理性血管的发生无抑制作用.随着对VEGFxxxb家族研究的逐步深入,选择性剪接调节VEGFxxx与VEGFxxxb两者之间的平衡,可作为糖尿病性视网膜病变、年龄相关性黄斑变性等眼内新生血管性疾病的治疗新策略.

Abstract：

Ocular neovascularization is the primary cause of blindness in a wide range of ocular diseases. The vascular endothelial growth factor A (VEGF-A) is the key factor involved in ocular angiogenesis, which can cause eye diseases through the development of pathological angiogenesis and increase of vascular permeability. There are two families of VEGF-A isoforms formed by alternative splicing,the angiogenic VEGF-A family ( VEGFxxx ), known to contribute to ocular neovascularization, and the antiangiogenic VEGF-A family ( VEGFxxx b), which is found in normal ocular tissues but downregulated in human diabetic retinopathy. The first member of the VEGFxxxb family to be isolated was VEGF165b. It can significantly reduce preretinal neovascularization without inhibition of physiological intraretinal angiogenesis.As the studies on the VEGFxxxb family proceed more deeply, controlling the balance of VEGFxxx to VEGFxxxb isoforms may be therapeutically valuable in the treatment of angiogenic eye diseases such as diabetic retinopathy and age-related macular degeneration.     

Corneal Neovascularization: An Anti-VEGF Therapy Review

Corneal neovascularization is a serious condition that can lead to a profound decline in vision. The abnormal vessels block light, cause corneal scarring, compromise visual acuity, and may lead to inflammation and edema. Corneal neovascularization occurs when the balance between angiogenic and antiangiogenic factors is tipped toward angiogenic molecules. Vascular endothelial growth factor (VEGF), one of the most important mediators of angiogenesis, is upregulated during neovascularization. In fact, anti-VEGF agents have efficacy in the treatment of neovascular age-related macular degeneration, diabetic retinopathy, macular edema, neovascular glaucoma, and other neovascular diseases. These same agents have great potential for the treatment of corneal neovascularization. We review some of the most promising anti-VEGF therapies, including bevacizumab, VEGF trap, siRNA, and tyrosine kinase inhibitors.     

Molecular pathogenesis of retinal and choroidal vascular diseases

There are two major types of ocular neovascularization that affect the retina, retinal neovascularization (NV) and subretinal or choroidal NV. Retinal NV occurs in a group of diseases referred to as ischemic retinopathies in which damage to retinal vessels results in retinal ischemia. Most prevalent of these are diabetic retinopathy and retinal vein occlusions. Subretinal and choroidal NV occur in diseases of the outer retina and Bruch's membrane, the most prevalent of which is age-related macular degeneration. Numerous studies in mouse models have helped to elucidate the molecular pathogenesis underlying retinal, subretinal, and choroidal NV. There is considerable overlap because the precipitating event in each is stabilization of hypoxia inducible factor-1 (HIF-1) which leads to upregulation of several hypoxia-regulated gene products, including vascular endothelial growth factor (VEGF), angiopoietin 2, vascular endothelial-protein tyrosine phosphatase (VE-PTP), and several others. Stimulation of VEGF signaling and suppression of Tie2 by angiopoietin 2 and VE-PTP are critical for sprouting of retinal, subretinal, and choroidal NV, with perturbation of Bruch's membrane also needed for the latter. Additional HIF-1-regulated gene products cause further stimulation of the NV. It is difficult to model macular edema in animals and therefore proof-of-concept clinical trials were done and demonstrated that VEGF plays a central role and that suppression of Tie2 is also important. Neutralization of VEGF is currently the first line therapy for all of the above disease processes, but new treatments directed at some of the other molecular targets, particularly stabilization of Tie2, are likely to provide additional benefit for subretinal/choroidal NV and macular edema. In addition, the chronicity of these diseases as well as the implication of VEGF as a cause of retinal nonperfusion and progression of background diabetic retinopathy make sustained delivery approaches for VEGF antagonists a priority.     

VEGF抑制剂在新生血管性青光眼治疗中的应用

新生血管性青光眼(neovascular glaucoma,NVG)是一种常见的继发性青光眼,常继发于糖尿病性视网膜病变、视网膜中央静脉阻塞和视网膜缺血综合征。其发病机制复杂,传统的治疗方式虽然能短暂缓解高眼压、消退虹膜新生血管,但对NVG的长期控制效果并不明显。随着近年来对NVG发病机制的深入研究及VEGF抑制剂在眼科疾病中的使用,NVG的治疗迎来了新的曙光。本文就VEGF抑制剂在新生血管性青光眼治疗中的应用做一综述,以期为NVG的治疗提供新的思路。     

Intravitreal anti‐vascular endothelial growth factor therapy with bevacizumab for tuberous sclerosis with macular oedema

Purpose: To describe two patients with macular oedema secondary to tuberous sclerosis complex (TSC) who were treated with intravitreal bevacizumab injection. Methods: Interventional case reports. Bevacizumab 1.25 mg was injected into the vitreous of two patients with TSC‐associated macular oedema / exudative retinal detachment. Vascular endothelial growth factor (VEGF) concentration in the vitreous fluid was measured by enzyme‐linked immunosorbent assay (ELISA) in one of these patients. Results: Patient 1: a 22‐year‐old woman with TSC was diagnosed as having multiple retinal hamartomas in both eyes. Eleven years later, the patient developed macular oedema with epiretinal membrane formation in the right eye. The patient underwent pars‐plana vitrectomy with retinal photocoagulation for retinal tumours. VEGF concentration in the vitreous fluid was high compared to that in patients without retinal vascular diseases. Recurrent macular oedema disappeared by intravitreal injection of bevacizumab. Patient 2: a 32‐year‐old woman with TSC‐associated retinal hamartoma, temporally showing macular exudative retinal detachment, developed neovascularization originated from the tumour. By intravitreal bevacizumab injection, the tumour size reduced markedly with regression of neovascularization. Conclusion: These results suggest that VEGF derived from retinal hamartomas causes macular oedema associated with TSC. Intravitreal injections of bevacizumab may be a useful therapeutic option for macular oedema secondary to TSC.     

内皮抑素抑制糖尿病视网膜新生血管生成中的研究进展

糖尿病视网膜病变(DR)是眼科常见病,常导致患者视力不可逆性下降,其2大特征包括黄斑水肿,视网膜新生血管生成;而视网膜新生血管生成是导致患者视力丧失最重要的原因之一.内皮抑素(ES)各种作用的发挥与其特有的结构特点密不可分,是目前公认的最强的抑制血管生长的因子之一,ES抑制视网膜新生血管的作用机制复杂,且尚未完全明确.因此,本文拟从ES调控细胞外基质的表达、抑制促血管生成蛋白的表达、调控关键信号通路的表达3个方面阐述ES抑制糖尿病视网膜新生血管病变的可能机制,并作一综述.