Brain-derived neurotrophic factor enhances neurite regeneration from retinal ganglion cells in aged human retina in vitro

To investigate the capability of neurite regeneration from retinal ganglion cells (RGCs) in an adult human retina and to evaluate the effect of neurotrophin on the neurite regeneration, an in vitro model for retinal explants was developed. A human retina was obtained from a 70 year old patient with retrobulbar carcinoma. The retina was excised and the retinal explants were cultured in serum-free medium with or without brain-derived neurotrophic factor. The capability of neurite regeneration was evaluated by counting the numbers of outgrowing neurites outside the retinal explants. In culture without brain-derived neurotrophic factor (control), there was no neurite outgrowth from the retinal explants after 2 days. And at 3 days in culture, a small number of outgrowing neurites were first observed outside the retinal explants. In contrast, within 24 hr in culture with brain-derived neurotrophic factor, there were a considerable number of elongating neurites with spread growth cones from the retinal explants. Immunohistochemical analysis revealed that these neurites were derived from RGCs. The addition of brain-derived neurotrophic factor increased the number of outgrowing neurites approximately 10-fold compared to that of the control at 3 days in culture. The enhancement of neurite regeneration induced by brain-derived neurotrophic factor continued for longer than 1 week in culture. In conclusion, an aged human retina can regenerate neurites from RGCs in vitro and brain-derived neurotrophic factor significantly promotes the regeneration.     

Brain-derived neurotrophic factor inhibits changes in soma-size of retinal ganglion cells following optic nerve axotomy in rats.

To determine if optic nerve axotomy affects the cell soma size of retinal ganglion cells and to establish whether such quantitative analysis is useful as a new way of evaluating retinal ganglion cell damage, we measured the changes in both the number and soma size of retinal ganglion cells after optic nerve axotomy in rats. Retinal ganglion cells were retrogradely labeled by fluoro-gold injection into the superior colliculus, and the soma size was measured using image-analysis software. We detected a decrease in the proportion of large-sized retinal ganglion cells that was significant at 3, 5 and 7 days after the axotomy, and an increased proportion of small-sized ones that was significant at 5 and 7 days after the axotomy, indicating that retinal ganglion cells shrank following axotomy, that there was a shift away from the largest category of retinal ganglion cells towards the smallest category. On days 3 and 5 post-axotomy, there was no significant change in the proportion of medium-sized retinal ganglion cells. Intravitreal injection of brain-derived neurotrophic factor one hour before the axotomy significant inhibited the increase in the proportion of small-sized retinal ganglion cells otherwise seen at 3 days after the axotomy. These results may suggest that larger retinal ganglion cells are more sensitive to optic nerve axotomy than small- and medium-sized ones, and that a quantitative analysis of soma size is a useful way of detecting retinal ganglion cell damage in the early phase after axotomy.     

Brain-derived neurotrophic factor prevents axotomized retinal ganglion cell death through MAPK and PI3K signaling pathways

PURPOSE: Brain-derived neurotrophic factor (BDNF) has a potential neuroprotective effect on axotomized retinal ganglion cells (RGCs); however, the mechanism, in regard to intracellular signaling, of BDNF-induced neuroprotection of RGCs is largely unknown. Intracellular signaling was investigated, by using axotomized RGCs and the relative contribution of the two major downstream signaling routes of TrkB determined--that is, mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3 kinase (PI3K)-Akt routes, mediated by BDNF. METHODS: Neuroprotective effects of BDNF were determined by quantifying the surviving RGCs after axotomy, by retrograde labeling. The MAPK and Akt levels were determined by Western blot analysis and activity assays. Quantification of the relative contribution of the two signaling pathways was performed by use of specific inhibitors for MAPK and PI3K (i.e., U0126 and LY294002, respectively). RESULTS: Intravitreous administration of BDNF had the most profound neuroprotective effects on axotomized RGCs among the neurotrophins. Burst phosphorylation of MAPK and Akt was induced by BDNF within 1 hour and was sustained over 2 weeks in the whole retina. Immunohistochemistry revealed that phosphorylated MAPK was detected in the RGCs and retinal Müller cells, and Akt was in the RGCs. BDNF-induced phosphorylation of MAPK and Akt was suppressed by their specific inhibitors. Moreover, administration of U0126 and LY294002 decreased significantly, but only partially, the neuroprotective effect of BDNF on the axotomized RGCs. CONCLUSIONS: BDNF-mediated signaling involves activation of both MAPK and Akt on the axotomized adult rat retina, and the collaboration of both MAPK and PI3K-Akt pathways seems to be necessary in neuroprotective signaling in axotomized RGCs.     

脑源性神经营养因子对视网膜神经细胞bcl-2蛋白动态表达的影响

目的 探讨脑源性神经营养因子(brain-derived neurotrophic factor,BDNF)对新生小牛视网膜神经细胞中bcl-2蛋白表达的影响.方法 以新生小牛视网膜为研究对象,传代培养视网膜神经细胞.培养细胞传至第2代,以加入BDNF为BDNF组,不加任何药物为正常对照组.在接种后第3天BDNF组加入终浓度为50μg·L-1的BDNF,Western blotting法检测给药后第2天、第4天、第6天BDNF组和正常对照组不同时间点以及两组间对应时间点bcl-2蛋白表达变化情况.结果 BDNF组bcl-2蛋白的表达在给药后第2天、第4天、第6天相对灰度值分别为0.447±0.052、0.355±0.039、0.287±0.031,呈现逐渐下降的趋势,第2天与第4天(t=2.788,JP=0.016)、第2天与第6天(t=4.844,P=0.000)比较差异均有统计学意义,第4天与第6天(t=2.056,P=0.062)比较差异无统计学意义.而正常对照组分别为0.314±0.033、0.300±0.004、0.299±0.060,第2天与第4天(t=0.411,P=0.688)、第2天与第6天(t=0.441,P=0.667)、第4天与第6天(t=0.030,P=0.976)之间比较差异均无统计学意义.在给药后第2天,BDNF组bcl-2蛋白的表达强度与正常对照组相比差异具有统计学意义(t=4.022,P=0.002),第4天(t=1.645,P=0.126)、第6天(t=0.381,P=0.710)与相应对照组间比较差异均无统计学意义.结论 BDNF能在短期内促进视网膜神经细胞bcl-2蛋白表达,提高细胞抗凋亡的能力,对延缓退行性视网膜疾病中的凋亡形成,开展视网膜神经细胞的神经保护具有一定作用.     

视网膜神经节细胞的保护和修复

视网膜神经节细胞(RGCs)的进行性死亡是许多视网膜和视神经疾病发展到最后的必经之路。长期以来一直认为，由于抑制性环境的存在，视神经损伤后不能再生和修复，现在研究证实，在特定的条件下，尽管RGCs的胞体或轴突受损，仍能免于死亡，而且变性的轴突能再生，并能与靶组织建立突触联系。对RGCs的保护和修复的研究进展作一综述。     

睫状神经营养因子对纯化培养大鼠视网膜神经节细胞突起再生的影响

目的观察睫状神经营养因子（ciliary neurotrophic factor，CNTF）对纯化培养大鼠视网膜神经节细胞（retinal ganglion cells，RGCs）突起再生的影响。方法取新生SD大鼠视网膜，消化并利用筛网纯化后接种于96孔板，加入不同浓度（10μg·L-1、20μg·L-1、30μg·L-1、40μg·L-1）CNTF作为实验组，不加CNTF作为对照。根据细胞形态及免疫细胞化学的方法鉴定细胞，观察RGCs生长规律，观测随机选取视野下的RGCs数和有突起细胞数（400倍荧光显微镜和相差显微镜）。结果 纯化的RGCs在含体积分数20％胎牛血清DMEM培养液中可存活30d。加入CNTF后3~5d，40μg·L-1组突起率显著高于对照组（P〈0.05）。7~15d，20μg·L-1、30μg·L-1、40μg·L-1组突起率显著高于时照组（P〈0.05），30μg·L-1、40μg·L-1组突起率显著高于10μg·L-1、20μg·L-1组（P〈0.05）。结论CNTF能显著促进RGCs突起再生，CNTF的浓度和突起率存在量效关系，一定浓度范围内．高浓度CNTF可较早促进突起再生。     

青光眼视网膜节细胞损伤的研究进展

青光眼是一种主要的致盲眼病,随着对青光眼研究的深入,逐渐认为高眼压和/或缺血造成视网膜节细胞(retinal ganglion cells,RGCs)以凋亡的方式不断丢失,而神经营养因子、谷氨酸、NO、自由基及Ca2+的浓度变化参与了RGCs的凋亡过程。我们通过本文综述了参与青光眼RGCs损伤的几种因素。     

Protective effects of ciliary neurotrophic factor on the retinal ganglion cells by injure of hydrogen peroxide

AIM: To explore the effect of ciliary neurotrophic factor (CNTF) on retinal ganglion cell (RGC)-5 induced by hydrogen peroxide (H2O2). METHODS: After cell adherence, RGC-5 culture medium was changed to contain different concentrations of H2O2 from 50 to 150 μmol/L at four time points (0.5, 1, 1.5 and 2h) to select the concentration and time point for H2O2 induced model. Two different ways of interventions for injured RGC-5 cells respectively were CNTF as an addition in the culture medium or recombinant lentiviral plasmid carrying CNTF gene transfecting bone mesenchymal stem cells (BMSCs) for co-culture with RGC-5. RESULTS: Compared to the control group, H2O2 led to RGC-5 death closely associated with concentrations and action time of H2O2 and we chose 125 μmol/L and 2h to establish the H2O2-induced model. While CNTF inhibited the loss of RGC-5 cells obviously with a dose-dependent survival rate. Nevertheless two administration routes had different survival rate yet higher rate in recombinant lentiviral plasmid group but there were no statistically significant differences. CONCLUSION: Both the two administration routes of CNTF have effects on RGC-5 cells induced by H2O2. If their own advantages were combined, there may be a better administration route.     

睫状神经营养因子对培养大鼠视网膜神经节细胞的影响

目的 观察不同浓度睫状神经营养因子(ciliary neurotrophic factor，CNTF)对培养大鼠视网膜神经节细胞（retinal ganglion cell，RGC）生长、存活的影响。 方法 取15只生后2～3d Wistar大鼠视网膜组织进行细胞培养，通过Thy-1单克隆抗体免疫细胞化学对培养的RGC进行鉴定。实验分对照组和10、20、40 ng/mlCNTF组（Ⅰ、Ⅱ、Ⅲ组），记录RGC存活时间，将培养第3、5、7天的RGC行四甲基偶氮唑盐（methylthio tetrazole,MTT）法测量吸光度(A)值［旧称光密度(OD)］。 结果 Thy-1单克隆抗体免疫组织化学检查显示培养3d的存活细胞90%以上为RGC。细胞存活期间实验组与对照组细胞均无明显突起,细胞体积无明显增大，实验组细胞存活时间比对照组长3~4d。培养第5、7d，Ⅰ组A值分别为0.075 8±0.0139、0.0693±0.0113，Ⅱ组A值分别为0.0902±0.0114、0.0825±0.0125，Ⅲ组A值分别为0.0792±0.0133、0.0653±0.0086，对照组A值分别为0.0620±0.0071、0.0513±0.0068。实验组与同时间对照组A值相比差异有显著性的意义（Ⅱ组与对照组相比P＜0.01，Ⅰ、Ⅲ组与对照组相比P＜0.05）。 结论 一定浓度的CNTF能促进培养大鼠RGC的存活，对RGC形态无影响。 (中华眼底病杂志, 2002, 18: 283-285)     

神經營養因子對混合培養鼠視網膜神經節細胞的影響

目的觀察兩種神經營養因子腦源性神經營養因子BDNF和碱性成纤維生長因子bFGF對混合培養鼠視網膜神經節細胞(retinal ganglion cells,RGCs)的影響,并節選出其有效濃度.方法采用胰酶消化法將12衹生後2～3天的Sprague-Dawley(SD)乳鼠視網膜制成細胞悬液,接種于鼠尾原包被的96孔培養板(5×104個細胞/孔).分别加入各種濃度梯度的BDNF和bFGF,在37℃、5%CO2恒温培養箱中培養,于1、3、5天,用MTT微量自動比色法測量存活細胞的吸光度A值.用Thy-l抗體、NSE抗體和GFAP抗體進行細胞免疫化學檢查以鍳定RGCs.結果培養在鼠尾原上的細胞生長良好,大部分伸出突起.培養1天、3天,各種濃度的BDNF和bFGF實驗組吸光度A值舆對照組比較均具有顯著性差异(p<0.01,p<0.05);培養5天,BDNF(40ng/ml、50ng/ml)、bFGF(15ng/ml)和BDNF+bFGF組吸光度A值高于對照組,具有顯著性差异(P＜0.01,P＜0.05).結論各種濃度的BDNF和bFGF均能促進鼠RGCs在體外的存活,BDNF具有濃度依賴性,BDNF的作用優于bFGF;同時應用BDNF和bFGF無叠加作用.     

Rat retinal ganglion cells co-express brain derived neurotrophic factor (BDNF) and its receptor TrkB.

The expression of brain derived neurotrophic factor (BDNF) and its preferred receptor (TrkB) in rat retinal ganglion cells (RGCs) have been determined in the present study. To identify RGCs retrograde labelling was performed with fluorogold (FG). Subsequently, retinas were immunostained with antibodies to BDNF and TrkB. We found that all RGCs labelled with FG express both BDNF and its preferred receptor, TrkB. Moreover, displaced amacrine cells were also found to be immunolabelled by both antibodies. Thus BDNF/TrkB signalling in RGCs probably involves endogenous BDNF produced by the RGCs themselves.     

超声微泡造影剂介导脑源性神经营养因子联合转染视网膜和视皮质对视神经损伤后视网膜神经节细胞的保护作用

　　目的　观察超声微泡造影剂介导脑源性神经营养因子（BDNF）联合转染大鼠视网膜和视皮质区细胞对视神经损伤后视网膜神经节细胞（RGC）的保护作用。方法　雄性Sprague-Dawley（SD）大鼠88只随机分为正常组（A组）、假手术组（B组）、空白对照组（C组）、单纯眼转染组（D组）、单纯脑转染组（E组）、联合转染组（F组）;A组8只大鼠,B～F组每组16只大鼠。建立钳夹视神经损伤模型,将B～F组大鼠随机分为视神经损伤1、2周亚组,各亚组8只大鼠。B、C组玻璃体腔和视皮质区分别注射磷酸盐缓冲液（PBS）,D、E组玻璃体腔和视皮质区分别注射BDNF质粒（pBDNF）微泡造影剂悬液,F组玻璃体腔和视皮质区同时注射pBDNF微泡造影剂悬液。D～F组注射pBDNF微泡微泡造影剂悬液后,立即用超声辐照相应转染部位。视神经损伤后1、2周,各组行逆行荧光金标记RGC计数;半胱氨酸蛋白酶-3(caspase-3）蛋白免疫组织化学染色,观察其阳性表达情况;图形视网膜电流图（PERG）检测,记录N95振幅。结果　荧光金标记RGC结果显示,各组均可见金黄色荧光散布于视网膜定向铺片上。A~F组间RGC计数差异有统计学意义（F=256.30,P＜0.01）;B~F组视神经损伤1、2周亚组间RGC计数差异也有统计学意义（F=6518,P＜0.01）。光学显微镜观察发现,A、B组大鼠视网膜均未见caspase-3蛋白阳性表达;C~F组均可见主要位于神经节细胞层的caspase-3蛋白阳性表达。PERG检测发现,A~F组间N₉₅振幅差异有统计学意义（F=121.56,P＜0.01）;B~F组视神经损伤1、2周亚组间N95振幅差异也有统计学意义（F=8238,P＜0.01）。结论　超声微泡造影剂介导BDNF联合转染视网膜和视皮质区细胞能抑制视神经损伤后RGC凋亡,提高RGC存活数,保护其视功能。      

氨基胍对视神经损伤后视网膜神经节细胞的保护性作用

视神经损伤是眼科常见疾病,多并发于颅脑外伤,预后不良,常致患者失明。由于视神经损伤的发病机制尚未完全明了,所以迄今为止其治疗仍是国内外眼科界的一大难题。现将视神经损伤后视网膜神经节细胞（retinal ganglion cells,RGCs）凋亡及氨基胍（Aminogunidine,AG）对其保护性作用做一综述。     

腺伴随病毒介导的脑源性神经营养因子对体外培养的鼠视网膜神经节细胞转染及生长特性的影响

目的 探讨重组腺伴随病毒载体介导的脑源性神经营养因子(rAAV-BDNF)对体外培养的鼠视网膜神经节细胞(RGCs)转染及其生长活性的影响.方法 实验研究.(1)应用rAAV-BDNF对体外培养2 d的RGCs进行转染;(2)应用逆转录聚合酶链反应(RT-PCR)技术,检测外源性BDNF基因在RGCs细胞mRNA水平的表达情况;(3)应用酶联免疫吸附测定(ELISA)法,对细胞培养液中BDNF含量进行检测;(4)对rAAV-BDNF转染细胞、未转染细胞及加入BDNF的培养细胞进行MTT比色分析;(5)应用Annexin V-FITC凋亡检测试剂盒和流式细胞仪,检测rAAV-BDNF转染细胞、未转染细胞及加入BDNF培养细胞的凋亡比率.结果 (1)RT-PCR检测结果:转染细胞表达外源性BDNF基因,而未转染细胞不表达BDNF基因.(2)ELISA法检测结果:rAAV-BDNF转染细胞的培养液中BDNF含量:转染7 d后为(616.1±40.0)ng/L,转染14 d后为(1075.1±48.7)ng/L.(3)MTT比色结果:转染3和6 d后,rAAV-BDNF转染细胞与未转染细胞间的吸光度(A)值差异无统计学意义(t=1.084,1.582;P=0.284,0.120);转染9 d后,转染细胞的A值高于未转染细胞(t=4.854,P=0.000).(4)流式细胞仪检测结果:rAAV-BDNF转染细胞和加入BDNF培养细胞的凋亡率明显低于未转染细胞的凋亡率,差异有统计学意义(P=0.015,0.017).结论 rAAV-BDNF可有效转染体外培养的鼠RGCs,转染细胞可在转录水平和翻译水平表达外源性BDNF基因,且生长活性改善,凋亡细胞减少.这为青光眼视神经保护的基因治疗提供了理论和技术支持.     

超声微泡造影剂联合美金胺增强视神经损伤大鼠视网膜神经节细胞保护作用

目的 探讨超声微泡造影剂联合美金胺对视神经损伤大鼠视网膜神经节细胞( RGC)的保护作用.方法 将Sprague-Dawley(SD)雄性成年大鼠40只随机分为正常对照组(A组),假手术组(B组),空白对照组(C组),玻璃体腔单独注射美金胺组(D组),玻璃体腔注射美金胺加超声微泡组(E组)5个组,每组8只大鼠,再将各组随机分为视神经损伤后1、2周2个亚组,各亚组4只大鼠.A组不做任何处理;B组只暴露视神经,不进行钳夹,玻璃体腔注射生理盐水,立即用超声波辐照大鼠眼球;C～E组建立视神经钳夹伤模型后,处理方式分别为C组玻璃体腔注射生理盐水,D组玻璃体腔注射美金胺,E组玻璃体腔注射超声微泡造影剂及美金胺,立即用超声波辐照大鼠眼球.视神经损伤1、2周时,各组行逆行荧光金标记RGC并计数;闪光视觉诱发电位(F-VEP)检测,记录P100波潜伏期及振幅;荧光电子显微镜下观察视网膜细胞形态学改变.结果 逆行荧光金标记RGC结果显示,各处理组视网膜定向铺片上均可见金黄色着染的RGC.A、B组RGC数间差异无统计学意义(q=0.018,0.011;P=0.986,0.873);C～E组RGC数均较A组减少,差异具有统计学意义(F=85.944,P=0.012);D组RGC数多于C组,差异具有统计学意义(q=1.721,1.924;P=0.043,0.037);E组RGC数明显高于C、D组,差异具有统计学意义(q=1.128,1.482,P=0.027,0.008;q=1.453,1.855,P=0.031,0.010).F-VEP检测发现,A、B组P100波潜伏期及振幅间差异无统计学意义(q=0.008,0.019,P=0.981,0.946;q=0.072,0.052,P=0.737,0.851) ;C～E组P100波潜伏期较A组延长,振幅较A组降低,差异具有统计学意义(F=134.312,106.312;P=0.017,0.009).荧光电子显微镜下观察发现,A、B组大鼠视网膜各层结构完整,排列整齐,RGC排列紧密整齐,细胞核均匀深染,胞核大小一致.C～E组大鼠的视网膜不同程度水肿变厚,RGC有不同程度的排列紊乱,空泡化及细胞数目减少.结论 超声微泡造影剂联合美金胺能抑制视神经损伤后大鼠RGC的丢失,促进其视功能的恢复,对视神经损伤大鼠的RGC具有保护作用.     

Effects of brain-derived neurotrophic factor and neurotrophin-4 on isolated cultured retinal ganglion cells: evaluation by flow cytometry

PURPOSE: Effects of brain-derived neurotrophic factor (BDNF) and neurotrophin (NT)-4 on retinal ganglion cells (RGCs) isolated and cultured in a serum-free medium are evaluated objectively by using flow cytometry. METHODS: RGCs from the retinas of 2-day-old rats were isolated in a two-step panning and cultured in a serum-free medium. BDNF (1, 10, and 100 pg/ml or 1, 10, and 100 ng/ml), NT-4 (0.1, 1, 10, and 100 ng/ml) or their vehicle, phosphate-buffered saline, were individually added to aliquots of the medium to be cultured for 48 hours. Then, after adding 5-chloromethylfluorescein diacetate, the survival of RGCs was evaluated using flow cytometry. RESULTS: The method used allowed the authors to analyze 10,000 RGCs per sample in approximately 2 minutes, so that a much larger number of cells was evaluated in a shorter period than with previously reported methods. RGCs were classified into either large or small RGCs, and the survival of each of these groups was determined objectively by the amount of fluorescent emission. BDNF improved the survival rate of RGCs concentration-dependently. In particular, the survival rate of small RGCs was greatly improved. BDNF at 100 ng/ml increased the survival rate of small RGCs by 17.4% and that of large RGCs by 7.8% in comparison to the controls. NT4 did not significantly improve the survival rates of either large or small RGCs. CONCLUSIONS: BDNF improved the survival rate of RGCs, particularly of small RGCs, concentration-dependently, but NT-4 had little influence on the survival rate. The current method was useful in evaluating the effects of neuroprotective factors or neurotoxic factors on cultured RGCs.     

脑源性神经营养因子在视觉系统发育和可塑性研究中的进展

弱视是一种与视觉中枢发育相关的疾病。近年来对于弱视中枢机制的研究集中于视皮层神经元突触可塑性及各种相关信号分子的表达差异。神经营养因子与神经系统发育及可塑性变化之间具有显著的相关性，其中脑源性神经营养因子（BDNF）在视觉系统中对神经元的正常发育、存活、分化、功能维持及可塑性等方面具有重要作用，既能调控神经元群体的程序性凋亡，亦能调制神经系统突触发育可塑性的效应。本文综述此方面的研究进展，以期对弱视发病机制的进一步研究有所提示。     

视神经损伤后节细胞的保护和神经修复的研究进展

高眼压、炎性病变、创伤、缺血及肿瘤压迫等均能严重损伤视神经,造成视力严重丧失。自1928年Cajal断言哺乳动物的中枢神经系统无再生能力以来,人们一直认为视神经损害后无法再生或修复。1985年So和Aguayo进行周围神经视网膜移植成功,彻底改变了视神经损伤后不能再生的观念,预示着不久的将来人类前视路损伤后视觉恢复将成为可能。