Pigment-epithelium-derived factor is upregulated in photocoagulated human retinal pigment epithelial cells

There is much evidence that pigment-epithelium-derived factor (PEDF) is a potent antiangiogenic cytokine which inhibits retinal and choroidal neovascularization by inducing apoptosis in activated vascular endothelial cells. Furthermore, the regulation of PEDF appears to be linked to the regulation of vascular endothelial growth factor (VEGF), one of the most potent inducers of intraocular neovascularization. Previous studies have established that thermal photocoagulation, the mainstay in the therapy of various neovascular diseases of the posterior segment, results in a decrease in intraocular concentrations of VEGF and other angiogenic growth factors, thereby inhibiting active retinal neovascularization. In the current study, we sought to determine whether thermal photocoagulation has the potential to regulate the expression of PEDF in human retinal pigment epithelial (RPE) cells. Cultures of RPE cells were photocoagulated with a 532-nm diode laser. Subsequently, RNA was isolated for RT-PCR, and whole-cell extracts and precipitated cell culture supernatant were subjected to Western blot analysis. According to our results, PEDF mRNA and protein are significantly upregulated after photocoagulation. Moreover, PEDF protein was found to be secreted in the cell culture medium.     

verteporfin光动力疗法对体外培养的成人视网膜色素上皮细胞色素上皮衍生因子、血管内皮生长因子表达水平的影响

目的 观察经光敏剂verteporfin光动力疗法（PDT）处理后的体外培养的成人视网膜色素上皮（RPE）细胞色素上皮衍生因子（PEDF）、血管内皮生长因子（VEGF）mRNA表达水平的改变。 方法 采用噻唑蓝比色法（MTT）测定PDT前后体外培养的成人RPE细胞活性的变化。应用半定量逆转录聚合酶链式反应(RT-PCR)测定PDT前后RPE细胞PEDF和VEGF mRNA表达水平的变化。 结果 PDT可造成RPE细胞死亡，死亡率与激光能量密度和光敏剂浓度成正相关。PDT后RPE细胞表达PEDF、VEGF mRNA水平下降，下降程度与激光能量密度和光敏剂浓度成正相关。 结论 PDT可下调体外培养的成人RPE细胞PEDF、VEGF mRNA的表达水平，这可能与PDT治疗黄斑下脉络膜新生血管膜（CNVM）后CNVM的消退或再生有关。 (中华眼底病杂志, 2006, 22: 256-260)     

Expression of pigment epithelium derived factor and vascular endothelial growth factor in choroidal neovascular membranes and polypoidal choroidal vasculopathy

AIMS: To determine whether pigment epithelium derived factor (PEDF), a protein that inhibits angiogenesis, is expressed in human choroidal neovascular membranes (CNVMs) and in tissues from an eye with polypoidal choroidal vasculopathy (PCV). In addition, to compare the expression of PEDF with that of vascular endothelial growth factor (VEGF), a known stimulator of angiogenesis, in these tissues. METHODS: CNVMs, associated with age related macular degeneration (AMD), angioid streaks, and PCV, were obtained during surgery. The expression of PEDF and VEGF in the excised subretinal fibrovascular membranes was determined by immunohistochemistry. RESULTS: PEDF and VEGF were strongly expressed in the vascular endothelial cells and retinal pigment epithelial (RPE) cells in the CNVMs where numerous new vessels were prominent (clinically active CNVMs). On the other hand, immunoreactivity for PEDF and VEGF was weak in the new vessels where fibrosis was prominent (clinically quiescent CNVMs). However, the RPE cells were still positive for PEDF and VEGF. The specimens from the eye with PCV also showed strong expression of PEDF and VEGF in the vascular endothelial cells and the RPE cells. CONCLUSION: Because PEDF is an inhibitor of ocular angiogenesis and an inhibitor of ocular cell proliferation, our results suggest that PEDF along with VEGF may modulate the formation of subfoveal fibrovascular membranes.     

Insulin-like growth factor-I and its receptor in neovascular age-related macular degeneration

PURPOSE: The insulin-like growth factor (IGF)-I protein is a growth-promoting polypeptide that can act as an angiogenic agent in the eye. The purpose of the current study was to localize the expression of IGF-I and its receptor (IGF-IR) mRNA and IGF-IR protein in situ in the normal human eye and to examine the presence of expression in eyes with neovascular age-related macular degeneration (AMD). METHODS: Formalin-fixed, paraffin-embedded slides of 4 normal control eyes and 14 eyes with choroidal neovascularization (CNV) secondary to AMD were examined. Three eyes with proliferative diabetic retinopathy were studied as the positive control. IGF-I and IGF-IR mRNA was detected by in situ hybridization with digoxigenin-labeled RNA probes. IGF-IR protein was studied by immunohistochemistry. RESULTS: In the normal retina, IGF-I and IGF-IR mRNA expression was found throughout the neuroretinal layers, in the retinal pigment epithelium (RPE), and in some choriocapillary and retinal capillary endothelial cells. In eyes with CNV we found IGF and IGF-IR mRNA in capillary endothelial cells, some transdifferentiated RPE, and fibroblast-like cells. IGF-IR protein was found in normal eyes in all neuroretinal layers, in the RPE, and in the choroidal vessels. In eyes with CNV, IGF-IR protein was present in the RPE monolayer, in transdifferentiated RPE, and in newly formed vessels. CONCLUSIONS: The colocalization of protein and receptor indicates an autocrine function of IGF-I in the normal human retina. Because IGF-I participates in ocular neovascularization, synthesis of IGF-IR and IGF-I in endothelial cells, RPE cells, and fibroblast-like cells in CNV may point toward a role for this growth factor in the pathogenesis of neovascular AMD.     

Effective transfection of a cis element "decoy" of the nuclear factor-kappaB binding site into the experimental choroidal neovascularization

PURPOSE: To evaluate the efficacy of the gene transfer of a double-stranded phosphorothioate oligonucleotides (ODNs), called a "decoy", against the NF-kappaB binding site into cells of an experimentally-induced choroidal neovascularization. METHODS: FITC-labeled decoy was injected into the subretinal space of rat eyes by the HVJ-liposome delivery system, and 3 days later, choroidal neovascularization was induced by laser photocoagulation. The eyes were removed and the transfected cells were detected by fluorescence microscopy and also detected by immunohistochemistry. The degree of neovascularization was evaluated by fluorescein angiography. RESULTS: The decoy was transfected into the retinal pigment epithelial (RPE) cells, inner and outer segment of the photoreceptors at 3 days after the injection. When choroidal neovascularization was induced, highly effective transfection of the decoy was observed 3 to 14 days after photocoagulation, after which the level decreased. Decoys were transfected into the RPE cells and macrophages in the choroidal neovascularization. The eyes transfected with NF-kappaB decoy showed a weaker leakage in fluorescein angiograms than that of the control eyes transfected with scrambled decoy. CONCLUSIONS: A decoy can be transfected into retinal cells and cells within a choroidal neovascularization by the HVJ-liposome method. The transferred NF-kappaB decoy reduced the degree of choroidal neovascularization. Decoy targeted against NF-kappaB may be considered as a potential therapy for neovascularization.     

Expression of FLK-1 in laser-induced choroidal neovascularization in mouse

AIM: To investigate the expression of vascular endothelial growth factor receptor 2 (VEGFR-2, also known as FLK-1) in laser-induced choroidal neovascularization (CNV) in mouse. METHODS: CNV was induced in C57BL/6 mouse eyes by krypton laser photocoagulation. Choroidal fluorescein angiography and histopathological examination were used to assess the development of experimental CNV. Cryostat sections from lesions on day 10 after laser treatment and normal eyes were prepared for immunohistochemistry for FLK-1. RESULTS: Laser-induced CNV developed in all lesions on day 10. The expression of FLK-1 was detected in endothelial cells, retinal pigmented epithelium (RPE)-like cells and fibroblast-like cells in neovascular lesions. In normal adult mouse retinas, FLK-1 expression was mainly observed in RPE cells, inner nuclear and ganglion cell layers. CONCLUSION: Our findings demonstrate that expression of FLK-1 may play a role in the formation of laser-induced CNV in mice, which suggests that FLK-1 may be a promising potential target for antiangiogenesis therapy for CNV.     

小鼠脉络膜血管新生模型中FLK-1的表达

目的:探讨小鼠脉络膜血管新生(choroidal neovascu larization, CNV)模型中FLK-1的表达.方法:采用激光击射的方法诱导成年C57BL/6小鼠CNV模型,术后行脉络膜灌流铺片及组织病理学检查观察CNV的发展.应用免疫组织化学染色探讨正常视网膜以及激光术后10d CNV模型中FLK-1的表达.结果:术后10d所有激光光斑均发展为实验性CNV,其中血管内皮细胞,类视网膜色素上皮细胞(retinal pigmented epithelium,RPE)及类成纤维细胞FLK-1表达强烈;在正常视网膜中,FLK-1仅在RPE、内核层及神经节细胞层有微弱的表达.结论:FLK-1参与了实验性CNV的发病过程,提示拮抗FLK-1可能成为防治CNV有效的生物学方法之一.     

Regression of ocular neovascularization in response to increased expression of pigment epithelium-derived factor

PURPOSE: Several pharmacologic treatments have been shown to reduce ocular neovascularization when administered before the onset of angiogenic stimuli, but none have been shown to cause regression of already established ocular neovascularization. In this study, the authors tested the effect of adenoviral vectored pigment epithelium-derived factor (PEDF) gene transfer on established neovascularization in transgenic mice with expression of vascular endothelial growth factor (VEGF) in photoreceptors (rho/VEGF mice) and in a model of choroidal neovascularization. METHODS: Two weeks after the onset of VEGF transgene expression in rho/VEGF mice or 2 weeks after laser-induced rupture of Bruch's membrane in wild-type mice, subgroups of mice were killed, and the baseline amount of neovascularization was measured by image analysis. The remainder of the mice received an intravitreous or subretinal injection of adenoviral vector containing a PEDF expression construct (AdPEDF.11) or control vector (AdNull.11). RESULTS: Seven days after injection in rho/VEGF mice or 10 days after injection in the choroidal neovascularization model, the amount of neovascularization in AdPEDF.11-injected eyes was significantly less than the baseline level, indicating that regression of neovascularization had occurred. There was TUNEL staining within choroidal neovascular lesions in eyes injected with AdPEDF.11. Eyes given a subretinal injection of AdNull.11 had TUNEL-positive cells in the retina, but none within areas of choroidal neovascularization. CONCLUSIONS: These data indicate that increased expression of PEDF causes regression of ocular neovascularization by promoting apoptosis of cells within neovascular lesions and possibly represents a new treatment paradigm for patients with established ocular neovascularization.     

血管内皮生长因子及其受体在实验性脉络膜新生血管中的表达

目的 探讨血管内皮生长因子(VEGF)及其FLK1受体在氪激光诱导的棕色挪威(BN)大鼠脉络膜新生血管(CNV)中的表达。方法 应用氪激光对30只雄性BN大鼠实验眼进行视网膜光凝,创建CNV模型,分别于光凝后3、7、14、21、28及56 d行荧光素眼底血管造影(FFA),处死大鼠后摘除眼球,制作组织病理学标本观察,原位杂交检测VEGFmRNA,免疫组化检测VEGF和FLK1受体。结果 正常BN大鼠视网膜神经节细胞层、内核层、色素上皮层、视网膜及脉络膜血管内皮细胞中均表达VEGFmRNA。实验眼光凝后3 d,光凝区视网膜神经节细胞层、内核层、外核层缺损区、视网膜及脉络膜血管内皮细胞均表达VEGFmRNA,此时视网膜下未形成CNV;3-21 d视网膜内VEGFmRNA表达水平逐渐下降(P<0.01);21 d与28 d和56 d比较,VEGFmRNA表达水平差异无显著意义(P>0.05)。光凝后7 d,FFA检查可见光凝区有圆盘状荧光素渗漏。病理切片可见视网膜下形成CNV,CNV中VEGFmRNA表达阳性;7～21 d,CNV中VEGFmRNA阳性染色面积及吸光度(A)值逐渐增加(P<0.01);21 d后VEGFmRNA表达水平差异无显著意义(P>0.05)。正常视网膜和脉络膜血管内皮细胞及视网膜神经节细胞层FLK1受体表达阳性;光凝后7 d,CNV中FLK1受体表达阳性;随CNV的增生,FLK1受体阳性染色面积及A值逐渐增加(P<0.01);21 d与28 d和5     

Expression of vascular endothelial growth factor in experimental choroidal neovascularization

Background: Although the choroidal neovascularization (CNV) is a common pathologic feature of a number of different eye diseases, its pathological mechanisms have not been fully elucidated. We investigated the expression of vascular endothelial growth factor (VEGF) in CNV using an experimental primate model. Method: CNV was induced by intense laser photocoagulation in four monkey eyes. Single eyes were enucleated at 1, 3, 7 or 14 days after photocoagulation and examined immunohistochemically for VEGF, macrophage antigen, von Willebrand factor and glial fibrillary acidic protein (GFAP). Expression of VEGF mRNA was examined byin situ hybridization. Results: One day after photocoagulation, the normal structure of the outer portion of the retina and the inner portion of the choroid was destroyed. Three days after photocoagulation, choroidal vascular endothelial cells migrated into the subretinal space through the defect in Bruch's membrane. Increased expression of VEGF was detected in the accumulating macrophages, migrating retinal pigment epithelial (RPE) cells and Muller cells. Maximal expression of VEGF was observed between 3 and 7 days after wounding, and many newly formed vessels extended into the subretinal space 7–14 days after photocoagulation. Conclusion: VEGF derived from RPE cells, macrophages and Müller cells may play a role in the formation of CNV.     

色素上皮衍生因子在大鼠脉络膜新生血管中的表达及意义

目的　探讨激光诱导BN大鼠脉络膜新生血管 (choroidalneovascularization ,CNV)中色素上皮衍生因子 (pigmentepithelium derivedfactor,PEDF)的表达及意义。方法　对 5组 30只BN大鼠行单眼视网膜氪激光光凝 ,诱导脉络膜新生血管形成。分别在光凝后 3d ,1、2、3及 4周摘除眼球 ,对光凝区进行病理学检查、Ⅷ因子相关抗原 (FⅧR :Ag)的免疫组织化学检查 ,以观测CNV形成。应用免疫组织化学及原位杂交技术检测CNV形成过程中PEDF、PEDFmRNA的表达及变化。结果　病理学检查及FⅧR :Ag免疫组织化学检查显示 ,光凝后 1周开始形成CNV ,3～ 4周达到高峰。正常BN大鼠PEDFmRNA、PEDF在视网膜神经节细胞、内核层部分细胞、视网膜色素上皮层表达。视网膜光凝后 ,PEDFmRNA、PEDF阳性染色信号可见于视网膜神经节细胞层、内核层、视网膜色素上皮层、外核层和脉络膜的损伤区 ;光斑边缘近脉络膜侧PEDF阳性表达信号明显高于光斑内部。光凝后 3d至 4周 ,光斑区内FⅧR :Ag阳性染色密度逐渐增加 (P <0 0 5 ) ,PEDFmRNA、PEDF阳性染色密度逐渐下降 (P<0 0 5 ) ,PEDF与FⅧR :Ag阳性染色密度负相关 (r=- 0 84 ,P <0 0 5 )。结论　CNV形成与PEDF表达量负相关 ,提示PEDF表达不足可能是CNV形成和增生的主要原因之一。     

Vitreous levels of pigment epithelium-derived factor and vascular endothelial growth factor: implications for ocular angiogenesis

PURPOSE: Pigment epithelium-derived factor (PEDF) has been demonstrated to suppress ocular angiogenesis in several animal models. In this study, we sought to measure the levels of PEDF and vascular endothelial growth factor (VEGF) in the vitreous of patients with and without ocular neovascular disorders. DESIGN: Case-control study of patients undergoing intraocular surgery for a variety of neovascular and nonneovascular conditions. METHODS: Vitreous samples were collected from 65 eyes of 65 patients with no neovascular disorder (n = 24), choroidal neovascularization (n = 9), active proliferative diabetic retinopathy (n = 16), and inactive proliferative diabetic retinopathy (n = 16). The levels of VEGF and PEDF in these vitreous samples were determined by enzyme-linked immunosorbent assay. RESULTS: The VEGF levels were at or below the level of detectability in the reference and choroidal neovascularization groups. The VEGF levels were significantly elevated in both the active and inactive PDR groups, and significantly higher in the active PDR group as compared with the inactive PDR group. The PEDF levels, which were present at relatively high concentrations in all groups, were higher in patients with active PDR compared with the control and choroidal neovascularization groups. CONCLUSIONS: High levels of immunoreactive PEDF are present in the vitreous of individuals with or without ocular neovascularization, but PEDF levels are significantly higher in patients with active PDR compared with patients with choroidal neovascularization or nonneovascular retinal diseases. Although these results do not preclude the possibility that endogenous PEDF helps to modulate ocular neovascularization, they do not support ischemia-induced downregulation of PEDF as a mechanism for such modulation.     

超声联合载色素上皮源性因子免疫纳米脂质体靶向治疗脉络膜新生血管

目的研究超声联合载色素上皮源性因子（PEDF）免疫纳米脂质体对脉络膜新生血管（CNV）的靶向治疗作用。方法以CNV内皮细胞上血管内皮生长因子受体-2（VEGFR-2）为靶向位点,将其配体寡肽连接到纳米脂质体上,再反向装载PEDF,制备能与CNV内皮细胞特异性结合的免疫纳米脂质体。对48只BN大鼠右眼行半导体倍频激光（波长为532nm）光凝术建立CNV模型。光凝后7d,实验组鼠尾静脉分别注射游离PEDF、载PEDF脂质体、载PEDF免疫脂质体,联合眼局部超声波辐照20s,并设立玻璃体腔注射PEDF组和对照组。光凝后14d,脉络膜巩膜冰冻切片观察免疫脂质体对CNV的靶向性。FITC-右旋糖酐标记脉络膜巩膜铺片行新生血管定量分析。结果载PEDF免疫脂质体可特异性靶向结合CNV。CNV与FITC标记的PEDF免疫纳米脂质体结合而呈现绿色荧光,正常脉络膜血管不显现荧光。玻璃体腔注射PEDF组及鼠尾静脉注射游离PEDF、载PEDF脂质体、载PEDF免疫脂质体组CNV面积均较对照组减少,差异有统计学意义（P〈0.05）。超声联合PEDF免疫纳米脂质体组对CNV的抑制作用强于玻璃体腔注射PEDF组（P〈0.05）。结论动物实验证实PEDF免疫纳米脂质体可特异性结合CNV细胞,超声可增强PEDF免疫纳米脂质体对CNV的抑制作用,该方法有望为眼新生血管的治疗提供新途径。     

Generation and characterization of a recombinant adenovirus expressing vascular endothelial growth factor for studies of neovascularization in the eye.

There is accumulating evidence that an increased expression of vascular endothelial growth factor from retinal pigment epithelial cells may be important in choroidal neovascularization. In vivo studies have demonstrated that subretinal injection of recombinant adenovirus vectors produces long-term transgene expression specifically within retinal pigment epithelial cells. A recombinant adenovirus encoding of vascular endothelial growth factor (Ad.RSV.VEGF) was therefore produced and characterized in order to determine whether an upregulation of vascular endothelial growth factor expression is sufficient to induce choroidal neovascularization. Ad.RSV.VEGF was produced by homologous recombination and its identity confirmed by restriction enzyme analysis. Ad.RSV.VEGF was characterized in vitro by the transduction of cultured retinal pigment epithelial cells. The in vitro characterization confirmed vascular endothelial growth factor mRNA and protein expression from Ad.RSV.VEGF and demonstrated the biological activity of the vascular endothelial growth factor protein. A preliminary in vivo study suggested that the subretinal injection of Ad.RSV.VEGF induced vascular leakage.     

Vitamin A up-regulates the expression of thrombospondin-1 and pigment epithelium-derived factor in retinal pigment epithelial cells

Vitamin A is essential for the visual system. It is metabolized in the retina and the resulting product, retinoic acid (RA), greatly affects the structure and functions of retinal pigment epithelial (RPE) cells. RPE cells produce a variety of extracellular matrix (ECM) proteins and angiogenic factors, both of which are expressed at varying levels in the normal RPE layer. In this study, we investigated the effect of all-trans-retinoic acid on the production of an ECM protein, thrombospondin-1 (TSP-1), and two angiogenic factors, pigment epithelium-derived factor (PEDF) and vascular endothelial growth factor (VEGF) by RPE cells. RA increased the release of TSP-1 and PEDF, but not that of VEGF, from human RPE cells in vitro. In vitamin A-deficient mice, the expression of TSP-1 and PEDF in the RPE layer considerably decreased compared with that of normal control mice. The vitamin A deficiency hardly affected the accumulation of VEGF in the RPE layer. These findings suggest that vitamin A modulates the structure and anti-angiogenic functions of the RPE layer partly by up-regulating the expression of the angiogenesis-related ECM protein, TSP-1, and the anti-angiogenic factor, PEDF.     

Molecular mechanism of choroidal neovascularization in age-related macular degeneration

The exudative form of age-related macular degeneration (AMD) is characterized by choroidal neovascularization (CNV). Retinal pigment epithelial cells (RPE) secrete various angiogenesis-related factors, especially vascular endothelial growth factor (VEGF) and pigment epithelium-derived factor (PEDF). The imbalance between the VEGF and PEDF secreted by RPE is a key contributor to the development of CNV in AMD. The earliest clinical hallmark of AMD is the presence of drusen. Although drusen are an epidemiological risk factor for the development of CNV, the mechanism of how drusen induce the development of CNV remains unclear. Recent proteome analysis demonstrated that amyloid beta (Abeta) deposition was specific to drusen from eyes with AMD. We focused on Abeta and investigated the effect of Abeta on cultured human RPE cells as well as ocular findings in neprilysin gene-disrupted mice, which leads to an increased deposition of Abeta. Our study demonstrates that Abeta accumulation affects the balance between VEGF and PEDF in the RPE, and reproduces features characteristic of human AMD, such as RPE atrophy and basal deposit formation in neprilysin gene-disrupted mice.     

Expression of transforming growth factor-beta receptors in normal rat retina and experimental choroidal neovascularization

PURPOSE: Transforming growth factor-beta (TGF-beta) plays an important role in the development of choroidal neovascularization. TGF-beta transduces signals through the mediation of type I and type II receptors. We investigated the expression of TGF-beta receptors in a normal rat retina and a model of experimentally induced choroidal neovascularization. METHODS: Choroidal neovascularization was induced by laser photocoagulation in rat eyes. The expression of TGF-beta receptors was determined using immunohistochemical and in situ hybridization methods. RESULTS: In normal adult rat retinas, immunoreactivity and mRNA expression of TGF-beta receptor type I (TbetaRI) and TGF-beta receptor type II (TbetaRII) were found in the ganglion cells. During the process of neovascularization, immunoreactivity and mRNA expression of TbetaRI and TbetaRII were widely distributed in laser lesions soon after photocoagulation; thereafter, these receptors were specifically detected in the endothelial cells of choroidal neovascularization. CONCLUSIONS: The expression of TGF-beta receptors in normal rat retinas suggests that TGF-beta plays an important role in the homeostasis of normal retina. The upregulation of TGF-beta receptors in choroidal neovascularization strongly suggests that TGF-beta is most likely transduced through specific receptors and plays an important role in the development of choroidal neovascularization.     

Expressions of angiopoietins and Tie2 in human choroidal neovascular membranes.

PURPOSE: To elucidate the potential role of angiopoietins and the Tie2 system in choroidal neovascularization. METHODS: Surgically excised choroidal neovascular membranes (CNVMs) were obtained at vitrectomy from five eyes with age-related macular degeneration, three eyes with idiopathic neovascular maculopathy, and two eyes had degenerative myopia and two eyes had angioid streaks. Light microscopic immunohistochemistry was performed to detect cytokines such as vascular endothelial growth factor (VEGF), Ang1, and Ang2 and cellular components such as retinal pigment epithelial (RPE) cells, macrophages, and endothelial cells. Immunofluorescent double staining using confocal microscopy was performed to identify the cell types that secrete specific cytokines. RESULTS: Ang1 and Ang2 were positive in all surgically excised CNVMs, regardless of the primary disease. Double staining revealed that many of the cytokeratin, CD68 and factor VIII positive cells also had Ang1 and Ang2 immunoreactivities. In contrast to Ang1, Ang2 immunoreactivity tends to be higher in the highly vascularized regions of many CNVMs, and the localization was very similar to that of VEGF staining. Almost all vascular structures had prominent immunoreactivity for Tie2, which was confirmed by double staining for Tie2 and factor VIII. Tie2 immunoreactivity was also observed in the RPE monolayer and in pigmented, polygonal, and fibroblast-like cells in the stroma. CONCLUSIONS: Present findings that Ang2 and VEGF are co-upregulated and that Tie2 is expressed in a variety of cell types in CNVMs further support a crucial role of the interaction between VEGF and Ang2 in pathologic angiogenesis of CNVM formation.     

Expression of connective tissue growth factor and its potential role in choroidal neovascularization

BACKGROUND: To determine the expression of connective tissue growth factor (CTGF) in choroidal neovascularization. METHODS: Surgically excised choroidal neovascular membranes (CNVMs) were obtained at vitrectomy from eight eyes with age-related macular degeneration, five eyes with high myopia, and two eyes with angioid streaks. Light microscopic immunohistochemical analysis was performed to detect CTGF, transforming growth factor beta 1 (TGF-beta1), vascular endothelial growth factor (VEGF), pancytokeratin, and smooth muscle actin (SMA). RESULTS: CNVMs were classified by fibrotic status as cellular CNVM, moderate fibrous CNVM, and extensive fibrous CNVM. CTGF expression was found in vascular cells, stromal cells, and retinal pigment epithelium (RPE) cells. For the stromal cells, fibroblastlike cells were most strongly positive for CTGF. CTGF immunoreactivity in the stroma was stronger in the fibrous CNVMs than in the cellular CNVMs. Immunohistochemical analysis of serial sections revealed colocalization of CTGF with TGF-beta1 and VEGF; colocalization of CTGF with pancytokeratin and SMA was also found. CONCLUSION: Our findings suggest that transdifferentiated RPE cells and vascular cells possess remarkable CTGF expression in CNVMs. This expression of CTGF may stimulate fibroblasts to produce extracellular matrix and may promote angiogenesis in vascular cells. Colocalized TGF-beta1 and VEGF may also contribute the upregulation of CTGF.