人胎视网膜血管结构发育的研究

目的；观察人胎视网膜血管结构发育过程。 方法：收集134例12~38周受精龄胎儿和4例成人视网膜，进行整装铺片和切片的免疫组织化学染色检查。 结果：①梭形细胞仅存于小于27周胎儿的视网膜内；足月胎儿节细胞层血管仍有出芽．②各阶段胎儿及成人视网膜血管基膜的纤维连接蛋白免疫反应均呈阳性。层粘连蛋白和Ⅳ型胶原免疫反应分别于25周和29周出现在节细胞层血管基膜，并分别在29周和32周开始完全包裹视网膜内已形成的4层血管．③内皮细胞束管道化时管道外即出现平滑肌细胞和周细胞．④4层血管向锯齿缘扩展的同时，内皮细胞外即有星形腔质细胞和Müller细胞突起形成血—视网膜屏障胶质膜。 结论：与成人比较，不同阶段胎儿视网膜血管均存在一定的缺陷，到足月时内皮细胞仍处在增殖、迁移状态． （中华眼底病杂志，1997，13：153-156）     

血管内皮生长因子对人胚胎视网膜血管发生的调节作用

目的研究血管内皮生长因子(vascular endothelial growth factor, VEGF)对人胚胎视网膜血管发生的调节作用。方法收集54例9-40周龄胎儿眼球后壁标本,免疫组织化学染色,光镜观察。结果①VEGF在视网膜的表达呈波峰式分布,高峰在9-13周及26周左右。②节细胞层的梭形细胞（血管内皮细胞前提细胞）、血管内皮细胞呈增殖细胞核抗原(proliferation cell nuclear antigen,PCNA)免疫反应阳性,水平波动,高峰在9-13周及21周前后,此期间梭形细胞不断增殖、分化形成内皮细胞索,经改建形成视网膜内层血管,26、34周起见内核层内、外缘血管内皮细胞呈PCNA免疫反应阳性,并保持至足月。③视网膜VEGF表达量与梭形细胞、血管内皮细胞PCNA表达量呈显著正相关(r=0.736,p＜0.01)。结论VEGF对视网膜血管的发生有显著促进作用。(中华眼底病杂志,1999,15:12-15)     

人胎视网膜血管发生方式的研究

目的：观察人胎视网膜血管的形成方式。方法：收集13～38周胎儿视网膜86例，免疫组织化学染色(ABC)法，光镜观察。结果：在胎儿12—13周时，间充质的梭形细胞从视盘处进入视网膜，并向锯齿缘迁移，同时分化、增殖为内皮细胞索，此索经管道化和改建成为节细胞层内的血管。第26周，节细胞层内已生成血管“出芽”，朝神经纤维层和内核层生长，分别在神经纤维层内和内核层的内、外缘各形成一层毛细血管网。结论：足月胎儿视网膜基本具有四层血管，分别由两种不同方式生成。 （中华眼底病杂志，1996，12：88-90）     

8～20周糖尿病大鼠视网膜血管内皮细胞周期阻滞

目的 研究非增生性糖尿病视网膜病变血管内皮细胞的周期变化。 方法 四氧嘧啶(alloxan)诱导Wistar大鼠糖尿病模型。免疫组化光镜和电镜、Western blotting法观察1～20周病程糖尿病大鼠视网膜血管壁细胞细胞周期的变化。 结果 免疫光镜和电镜观察到8～20周糖尿病大鼠视网膜血管呈cyclinD1、cyclinD3、cyclinB1、p21和p27免疫阳性反应,偶见内皮细胞呈cyclinE免疫阳性反应。同时可见内皮细胞细胞质减少、细胞变薄、腔面泡状结构和微绒毛增多。而此阶段周细胞和视网膜内其它类型细胞未见有超微结构变化并为免疫阴性反应。考马斯亮蓝凝胶电泳和Western blotting亦证实视网膜内有cyclinD1、cyclinB1、p21和p27蛋白的表达。 结论 高糖导致8～20周糖尿病大鼠视网膜血管内皮细胞进入细胞周期并阻滞于G1/S限制点,而周细胞没有出现相应的变化,本研究也提示在糖尿病早期视网膜血管内皮细胞具有拮抗高糖损伤、自我稳定的分子机制。 (中华眼底病杂志,2000,16:173-716)     

CD34在翼状胬肉中表达的意义

目的研究翼状胬肉组织中CD34的表达及意义。方法对50例手术切除的翼状胬肉标本行苏木精-伊红染色、过碘酸希夫染色，并进行形态学、免疫组织化学研究和免疫荧光共聚焦显微镜下观察CD34、波形蛋白（VIM）、血管内皮生长因子（VEGF）在翼状胬肉中的表达。结果在翼状胬肉标本中，CD34在血管内皮细胞、血管周细胞以及一些散在的星形、梭形细胞中表达阳性，而在血管壁上及成熟的胶原细胞上呈阴性表达；VIM阳性表达于大部分翼状胬肉组织中；组织中部分疏松排列的网状及裂隙样、管样区结构过碘酸希夫染色呈阳性的紫红色反应；网状区的梭形细胞VEGF阳性表达。结论翼状胬肉组织中CD34阳性细胞来源于间充质干细胞的分化。翼状胬肉除以血管发生和血管新生的方式生成血管外，血管拟态可能是另外一种供血途径。     

人视网膜星形胶质细胞发育及起源的研究

背景 视网膜星形胶质细胞是视网膜主要的神经胶质细胞,其起源及演变过程一直是国内外研究的热点和难点. 目的 探讨人胚胎眼视网膜星形胶质细胞的起源及发育.方法 收集33例自愿终止妊娠的流产人胚胎眼标本,其中8 ～12孕周者20例,15～ 17孕周者2例,19～ 23孕周者4例,25～ 28孕周者4例,30 ～32孕周者3例.对眼球壁切片进行常规组织病理学检查以观察不同胚龄人视网膜发育的形态学变化,分别采用免疫组织化学法及免疫荧光法动态观察不同胚龄人视网膜星形胶质细胞起源位点及发育过程中胶质纤维酸性蛋白( GFAP)表达的变化.结果 人胚6～7周视杯处于视网膜分层发育阶段,9周时视杯内层原无细胞层出现分化不成熟的圆短梭形细胞；胚龄15周时视网膜主要层次可见,分化的细胞增加,但未发现GFAP阳性细胞；胚龄19周视网膜可见梭形细胞从返折部原始神经上皮迁出,并可见这些细胞中GFAP呈阳性表达；胚龄25～ 26周后极部视网膜可见GFAP表达阳性的梭形细胞,这些细胞围绕视网膜血管分布,与血管壁联系密切,邻近锯齿缘处的视网膜内层可见表达GFAP的星形或梭形细胞与睫状体非色素上皮相连,但锯齿缘稍后与赤道区之间并未见GFAP阳性细胞；胚龄28周,视网膜星形胶质细胞呈典型的星状,其突起伸达视网膜内网状层. 结论 人视网膜星形胶质细胞至少存在3个起源位点,即血管前体细胞/周皮细胞、视盘旁原始神经上皮及邻近锯齿缘的睫状体无色素上皮.     

胚胎视网膜血管发生方式及其促进因子

视网膜血管病中新生血管的发生占有重要地位。是很多视网膜病变的严重并发症,其发病机制尚未完全明了,综述了胚胎视网膜篾 发生方式及其促进因素。人胚胎视网膜血和发生存在两个阶段,第一阶段为视网膜内因发育,由梭形细胞增殖分化形成血管内皮细胞,再改建成血管,第二阶段是外层血管的发育,由已存在的内层血管以出芽方式因管的生成受到多种因素的调节,促进血管新生的调节因子有很多,其中血管内皮生长因子,碱性成纤维细胞生     

重组人血管抑制因子Vasostatin对视网膜血管内皮细胞增殖的影响

目的 探讨重组人血管抑制因子Vasostatin对体外培养的恒河猴视网膜血管内皮细胞(RF／6A)增殖的影响。方法 以bFGF刺激增殖，体外培养恒河猴视网膜血管内皮细胞(RF／6A)至4代，分别加入不同质量浓度的重组人Vasostatin蛋白，并采用MTT法、^3H-TdR法检测2、4、6d时其对血管内皮细胞增殖抑制的作用，同时利用流式细胞仪对重组人Vasostatin蛋白是否诱导细胞凋亡进行了探讨。结果 MTT法、^3H-TdR两种方法均显示重组人Vasostatin蛋白以质量浓度依赖的方式抑制bFGF刺激的恒河猴视网膜血管内皮细胞(RF／6A)的增殖。流式细胞仪检测显示加入重组人Vasostatin蛋白后，G0／G1期无明显的亚二倍体核形峰出现，其不是通过诱导细胞凋亡的方式来抑制细胞增殖的。结论 重组人Vasostatin蛋白在体外具有抑制bFGF诱导的血管内皮细胞增殖的作用，其有可能成为一种有效的血管新生抑制剂。     

星形胶质细胞与糖尿病视网膜病变

视网膜星形胶质细胞分布于神经元与毛细血管之间。在发育过程中，星形胶质细胞的成熟需要血管内皮细胞的诱导。视网膜星形胶质细胞参与血一视网膜屏障的形成，并对其功能进行调控；通过表达谷氨酸转运体参与谷氨酸代谢；通过产生的钙振荡对神经元细胞的活动进行调节；调节大分子物质在胶质细胞问的扩散。此外，星形胶质细胞还具有神经元营养保护功能。糖尿病视网膜病变（DR）发生时，视网膜星形胶质细胞的数量减少，其标志物GFAP的表达量减少、谷氨酸代谢能力减弱、COX-2表达、AR和VEGF表达量增加。由此可以推论：视网膜星形胶质细胞是神经元与血管细胞活动的桥梁。对星形胶质细胞的研究有助于揭示DR中神经元病变与血管病变之间的相互关系。     

糖尿病大鼠视网膜血管内皮细胞p53、bcl-2及生长因子的表达与细胞周期阻滞

目的 观察p53、bcl-2、bax基因、血管内皮细胞生长因子（vascular endothelial cell growth factor, VEGF）、碱性成纤维细胞生长因子（basic fibro blast gro wth factor, bFGF）、胰岛素样生长因子-I（insulin-like growth factor-I, IGF-I ）及其受体在1～20周糖尿病大鼠视网膜血管内皮细胞(vascular endothelial cell, VECs) 的表达以及与细胞周期阻滞的关系。 方法 四氧嘧啶(alloxan)诱导制作糖尿病大鼠模型；免疫组织化学染色，光、电镜观察；斑点印迹（dot blotting）测定p53、bcl-2 mRNA；Western 印迹（Western blotting）测定p53、bcl-2蛋白。 结果 免疫组织化 学染色后光学显微镜观察显示8～20周糖尿病大鼠视网膜节细胞层、内核层的各类血管都呈p53、bcl-2免疫阳性反应。电镜观察显示阳性反应物沉淀在VECs。VECs同时为VEGF、bFGF、IGF-I蛋白及其受体阳性反应。视网膜内其它细胞及同窝对照大鼠和1～6周病程糖尿病大鼠视网膜所有细胞均未见上述蛋白阳性反应。Dot blotting测定结果显示，20周糖尿病大鼠视网膜组织有p53和bcl-2 mRNA表达。Western blotting测定证实20周糖尿病大鼠视网膜表达p53和bcl-2 蛋白。对照组及1 ~ 20周糖尿病大鼠视网膜内未见bax阳性反应物。 结论 p53、bcl-2可能参与介导糖尿病大鼠视网膜VECs周期阻滞。高糖刺激生长因子VEGF、bFGF、IGF-I及其受体的表达，生长因子可能通过自分泌途径维持VECs存活。 （中华眼底病杂志，2003，19：29-33）     

Development of the primate retinal vasculature

Human and macaque retinae have similar retinal vascular anatomy. The general features of the retinal vascular anatomy of these two primates have much in common with more widely studied animal models such as rat and cat. However, primates are unique amongst mammals in having a region in temporal retina specialized for high visual acuity, which includes the fovea centralis (or ‘fovea’). Several features distinguish the fovea from other parts of the retina, including a very high local density of cone photoreceptors, a high density of inner retinal cells during development, and an absence of retinal blood vessels.

The retinal vascular complex comprises a number of cell types, in addition to vascular endothelial cells, including pericytes, microglia, astrocytes—none of which is intrinsic to the retina. In addition, amacrine-like cells make bouton-like associations with retinal vessels and may be involved in the autoregulation of blood flow. During development endothelial cells ‘invade’ the retina, accompanied by a population of microglial cells; glial fibrillary acidic protein (GFAP)-immunoreactive astrocytes are also seen associated with the developing vasculature, and are in advance of the vascular front by a few hundred microns. Recent findings indicate that astrocytes at the vascular front proliferate in response to factors released by endothelial cells, including leukemia inhibitory factor. Better understood is the role of GFAP-immunoreactive astrocytes just in advance of the developing vessels. These astrocytes are sensitive to hypoxia and in response release vascular endothelial growth factor (VEGF) which in turn promotes the migration, differentiation and proliferation of vascular endothelial cells. This hypoxia/VEGF-mediated process of migration, proliferation and differentiation appears common to the retinae of a variety of species, including human. However, in human and macaque retina, different mechanisms appear to govern the development of the retinal vessels growing along the horizontal meridian of the retina towards the central area, which contains the fovea. Despite the relatively advanced state of differentiation and maturation of cells in the central area compared with the periphery, the growth of retinal vessels into the central area has been described as ‘retarded’, and the incidence of cell proliferation associated with these vessels is lower than in peripheral vessels. Furthermore, neither retinal vessels nor their accompanying astrocytes grow into a circumscribed region which, at a later stage, develops into the foveal depression. These observations suggest that molecular markers define the foveal region and inhibit cell proliferation and vascular growth at the fovea and, perhaps, along the horizontal meridian. The findings also suggest that at the fovea, the retina is adapted morphologically to its blood supply, since in the vicinity of the fovea, the development of retinal vessels is retarded or inhibited. The limitations on vascularization of central retina has implications for its vulnerability to degenerative changes, as seen in age-related macular degeneration.     

Pathophysiology of intraocular neovascularization]

The pathology of intraocular neovascularization was studied in human and animal eyes by means of electron microscopy and histochemistry, and also by tissue culture of bovine retinal small vessels. The newly formed vessels in the vitreous obtained at the time of vitrectomy from the eyes with proliferative diabetic retinopathy and retinal vein occlusion lacked tight junction and formed fenestration in the endothelial cells. When 1 microgram of the basic fibroblast growth factor (b-FGF) enveloped in ethylene vinyl acetate copolymer was implanted into the vitreous of monkey eyes, new vessels were formed in the iris in all eyes and in the vitreous in 12 eyes out of 14 experimental eyes. The origins of new vessels were the iris vessels in the iris, and both stromal vessels of the ciliary body and retinal vessels in the vitreous. These vessels showed fenestration in the endothelial cells. The activity of the lysosomal enzyme detected by acid phosphatase increased in the epithelial layer of the ciliary body. The new vessels in the vitreous of rabbits were seen in 9 out of 10 eyes when b-FGF was implanted in the vitreous with an intravitreal injection of amino adipic acid solution (1 mg in 0.2 ml of physical saline), although none of the 8 eyes formed new vessels when sodium iodate was injected intravenously after implantation of b-FGF with aminoadipic acid. Corneal neovascularization was formed by implantation of 250 ng of b-FGF into the corneal micropockets of the guinea pigs, and regressed after the b-FGF was removed. The endothelial budding and protrusion were frequently seen during the course of neovascularization. Immunohistochemical detections showed positive stainings for fibronectin in most front-end lesions, for laminin and type 4 collagen associated with the endothelial cells, and for factor VIII only on the endothelial cells which formed the vascular lumen. The acid phosphatase activity was detected on the leucocytes infiltrating in the corneal stroma. In the course of regression of corneal neovascularization, initial pathological change was thrombus formation followed by disappearance of endothelial cells, although the basement membrane of the endothelial cells remained. Fibronectin reduced its activity in the early stage of regression, laminin and type 4 collagen remained even after the vascular lumen had subsided, and factor VIII was stained in a geographically irregular manner. Migrating activity of the cultured-bovine retinal small vessels was accelerated by fibronectin and fetal bovine serum.     

Astrocyte-endothelial cell relationships during human retinal vascular development

PURPOSE: To evaluate evidence for the presence of vascular precursor cells (angioblasts) and astrocyte precursor cells (APCs) in the developing human retina and determine their relationship. METHODS: Pax-2/GFAP/CD-34 triple-label immunohistochemistry was applied to four retinas aged 12, 14, 16, and 20 weeks of gestation (WG) to label APCs, astrocytes, and patent blood vessels. APCs are Pax-2(+)/GFAP(-), whereas astrocytes are Pax-2(+)/GFAP(+). Adenosine diphosphatase (ADPase) enzyme histochemistry, which identifies endothelial cells and vascular precursors, was applied to human retinas aged 12, 16, 17, and 19 WG. Nissl stain, a nonspecific cell soma marker, was applied to 14.5-, 18-, and 21-WG retinas. Established blood vessels were visualized with CD34 and ADPase. RESULTS: Topographical analysis of the distribution of Nissl-stained spindle cells and ADPase(+) vascular cells showed that these two populations have similar distributions at corresponding ages. ADPase(+) vascular precursor cells preceded the leading edge of patent vessels by more than 1 millimeter. In contrast, Pax-2(+)/GFAP(-) APCs preceded the leading edge of CD34(+) blood vessels by a very small margin, and committed astrocytes (Pax-2(+)/GFAP(+)) were associated with formed vessels and nerve fiber bundles. Two populations of ADPase(+) cells were evident, a spindle-shaped population located superficially and a deeper spherical population. The outer limits of these populations remain static with maturation. CONCLUSIONS: A combination of Pax-2/GFAP/CD34 immunohistochemistry, Nissl staining, and ADPase histochemistry showed that the vascular precursor cells (angioblasts), identified using ADPase and Nissl, represent a population distinct from Pax-2(+)/GFAP(-) APCs in the human retina. These results lead to the conclusion that formation of the initial human retinal vasculature takes place through vasculogenesis from the prior invasion of vascular precursor cells.     

Localization of tubby-like protein 1 in developing and adult human retinas

PURPOSE: To localize tubby-like protein 1 (TULP1) in developing and adult human retinas. METHODS: TULP1 was localized by immunofluorescence microscopy in human retinas, aged 8.4 fetal weeks to adult. TULP1-positive cells were identified by double labeling with antibodies specific for cones, rods, and astrocytes. RESULTS: In adult retinas, anti-TULP1 labels cone and rod inner segments, somata, and synapses; outer segments are TULP1-negative. A few inner nuclear and ganglion cells are weakly TULP1-positive. In fetal retinas, cells at the outer retinal border are TULP1-positive at 8.4 weeks. At 11 weeks, the differentiating central cones are strongly TULP1-reactive and some are positive for blue cone opsin. At 15.4 weeks, all central cones are strongly positive for TULP1 and many are reactive for red/green cone opsin. At 17.4 weeks, central rods are weakly TULP-reactive. In peripheral retina at 15.4 weeks to 1 month after birth, displaced cones in the nerve fiber layer are positive for TULP1, recoverin, and blue cone opsin. Some ganglion cells are weakly reactive for TULP1 at 11 weeks and later, but astrocytes and the optic nerve are TULP1-negative at all ages examined. CONCLUSIONS: The finding of TULP1 labeling of cones before they are reactive for blue or red/green cone opsin suggests an important role for TULP1 in development. TULP1 expression in both developing and mature cones and rods is consistent with a primary photoreceptor defect in retinitis pigmentosa (RP) caused by TULP1 mutations. Weak TULP1-immunolabeling of some inner retinal neurons in developing and adult retinas suggests that optic disc changes in patients with RP who have TULP1 mutations may be primary as well as secondary to photoreceptor degeneration.     

Endothelial nitric oxide synthase is expressed in amacrine cells of developing human retinas

PURPOSE: To examine the expression and cellular distribution pattern of endothelial nitric oxide synthase (eNOS) in the developing human retina and to compare its expression with that in rats. METHODS: Expression of eNOS was examined by immunohistochemistry in retinas of humans ranging from 8.5 to 28 weeks of gestation (WG) and of rats. RESULTS: In the developing human retina, eNOS expression was first detected in the proximal margin of the neuroblastic layer in the incipient fovea-surrounding area at 12 WG. At 17 to 28 WG, eNOS-immunoreactive cells were located in the innermost part of the inner nuclear layer and in the ganglion cell layer, expanding to both temporal and nasal retinas and the processes projecting into the inner plexiform layer. These eNOS-positive cells coexpressed syntaxin and glutamate decarboxylase, and are probably GABAergic amacrine cells. The onset of eNOS expression in developing amacrine cells, however, preceded the invasion of retinal vasculature, long before vascular function involving these cells can be expected, suggesting that eNOS has a role not only in vasoregulation but also in retinal development. From 20 WG on, eNOS was also detected in the photoreceptors adjacent to the fovea. eNOS expression in amacrine cells and photoreceptors was observed in the central-to-peripheral and temporal-to-nasal gradients. However, in the developing rat retina, eNOS was expressed exclusively in the vascular endothelial cells. CONCLUSIONS: The results support that eNOS plays a role, not only in the regulation of vascular function but also in the process of retinal development in humans.