睫状神经营养因子对视神经损伤修复作用研究进展

视神经损伤后,视网膜神经节细胞进行性损害,轴突变性坏死,再生困难.睫状神经营养因子是一种非靶源性神经营养因子,在视网膜神经节细胞的生长发育中起重要作用,同时对损伤的视网膜神经节细胞有促进存活及轴突再生的作用.     

转基因表达神经营养因子治疗视神经损伤的研究进展

视神经损伤是眼科重要的致盲因素之一,目前临床尚无特效的治疗方法.神经营养因子可明显促进视网膜神经节细胞的存活和轴突的再生,但其在体内的作用时间较短.通过转基因技术持续表达神经营养因子则克服了这一缺点,这将为治疗视神经损伤性疾病提供新思路.笔者就近年来国外应用神经营养因子转基因技术治疗视神经损伤的研究进展进行综述,以供同道参考.     

晶状体损伤促进视神经再生的研究进展

视神经损伤是眼科重要的致盲原因之一,在眼科的临床治疗中并没有有效的方法.近期发现的晶状体损伤可以促进视网膜神经节细胞(RGCs)存活与再生,为临床医生治疗视神经损伤提供了新的思路.目前,关于晶状体损伤促进RGCs再生效应的机制有很多的说法,主要与基因表达、局部炎症作用、晶状体上皮和蛋白的变化以及神经营养因子作用有关.     

睫状神经营养因子转基因治疗视神经损伤的研究进展

视神经损伤的治疗一直是医学界的难题。而睫状神经营养因子(CNTF)能促进视网膜缺血后视网膜神经节细胞的存活和轴突切断后再生,为治疗视神经损伤提供了可能。但单纯应用外源性CNTF直接治疗,在体内作用时间短,而其与转基因技术相结合克服了该缺点,为治疗视神经损伤性疾病开辟了新途径。本文就CNTF的分子生物学特性、对视神经损伤的保护作用,特别是CNTF转基因治疗在视神经损伤的研究进展作一综述。     

细胞因子对视网膜神经元保护和诱导作用的研究进展

近年来细胞因子在视网膜功能重建中的作用已初见端倪。研究发现,脑源性神经营养因子、睫状神经营养因子、碱性成纤维细胞生长因子及神经营养素4可以防止视网膜光感受器细胞变性的发生,增强光感受器细胞损伤后的修复,促进视网膜神经节细胞的发育,刺激神经节细胞轴突的再生。同时,晶状体上皮源性生长因子及人羊膜上皮细胞分泌的细胞因子也对神经节细胞有保护效应。而神经营养素-3在视网膜的作用性质还有待更多的研究。（中华眼科杂志,2005,41：861-864）     

脑源性神经营养因子与视网膜神经节细胞

脑源性神经营养因子作为神经营养因子家族中的重要成员，广泛分布于中枢神经系统。视神经与视网膜是中枢神经系统的一部分，视网膜神经节细胞在视觉通路中起着重要的传导作用。脑源性神经营养因子作为一种靶源性神经营养因子和顺行性神经营养因子，在视网膜神经节细胞的生长发育过程中起重要调控作用，同时对损伤的视网膜神经节细胞有促进其存活及轴突生长的作用。     

晶状体损伤与视神经轴突再生关系的研究进展

视神经损伤是眼科重要的致盲因素之一,临床中尚无有效的治疗方法.研究证实,晶状体损伤后可以成功促进视网膜神经节细胞(RGC)存活和视神经轴突再生.晶状体损伤后,晶状体上皮细胞活化,可能成为影响视神经轴突再生的潜在因素.同时,巨噬细胞活化并分泌某些因子刺激RGC轴突再生.进一步的研究发现,可溶性混合晶状体蛋白对RGC的存活和突起生长有显著的促进作用,是晶状体来源的"神经保护性物质",其作用显著强于巨噬细胞提取液.因此,研究晶状体损伤后促进视网膜神经节细胞存活和神经轴突再生的机制及其关键性物质,有利于进一步揭示视神经损伤和再生的机制,探求新的治疗方法.     

脑源性神经营养因子与视网膜神经节细胞

脑源性神经营养因子作为神经营养因子家族中的重要成员,广泛分布于中枢神经系统。视神经与视网膜是中枢神经系统的一部分,视网膜神经节细胞在视觉通路中起着重要的传导作用。脑源性神经营养因子作为一种靶源性神经营养因子和顺行性神经营养因子,在视网膜神经节细胞的生长发育过程中起重要调控作用,同时对损伤的视网膜神经节细胞有促进其存活及轴突生长的作用。     

重组逆转录病毒脑源性神经营养因子在小鼠胚胎细胞中的表达

神经干细胞移植是近年来治疗视神经损伤疾病新的研究方向之一，然而如何能够让干细胞在眼内移植后定向分化为视网膜神经节细胞，一直是个难题。脑源性神经营养因子（BDNF）作为神经营养因子家族的重要成员之一，因其能够促进神经细胞生长分化、维持神经细胞正常功能、减缓神经元的损伤、并能够防止损伤后的细胞凋亡而日益受到重视。我们将重组的真核表达载体pLXSN—BDNF进行体外包装并检测了BDNF基因在细胞中的表达，对BDNF基因转染的神经干细胞眼内移植，探讨该基因在视神经保护中的作用奠定了基础。     

晶状体损伤对视神经损伤后再生影响的研究

视神经损伤是眼科重要的致盲因素之一 ,在眼科临床中尚未找到有效的治疗方法 ,为此寻找促进神经修复与再生的有效手段成为现代神经生物领域的热点。最近研究认为 :损伤晶状体后可以成功地促进视网膜神经节细胞的存活和视神经轴突的再生。我们对该领域迄今为止的主要研究成果做一综述。     

Adeno-associated viruses containing bFGF or BDNF are neuroprotective against excitotoxicity

PURPOSE: Brain-derived neurotrophic factor (BDNF) and basic fibroblast growth factor (bFGF) hold much promise for the protection of retinal ganglion cells against excitotoxic cell death. We tested the possibility of delivering these growth factors to retinal ganglion cells via an adeno-associated viral (AAV) vector and tested their efficacy in two models of excitotoxicity. METHODS: Rat retinas were infected with AAV vectors encoding bFGF or BDNF. A control vector containing green fluorescent protein (GFP) was injected in the contralateral eye. Eyes were subjected to either an intravitreal injection of N-methyl-D-aspartate (NMDA) or optic nerve crush, and ganglion cell survival was evaluated. RESULTS: AAV.CMV.bFGF and AAV.CBA.BDNF were neuroprotective against NMDA injection 1 month post-treatment. Additionally, AAV.CMV.bFGF was protective against optic nerve crush. CONCLUSION: AAV-mediated delivery of bFGF and BDNF can promote retinal cell survival following excitotoxic insult.     

CNTF, not other trophic factors, promotes axonal regeneration of axotomized retinal ganglion cells in adult hamsters

PURPOSE: To investigate the in vivo effects of trophic factors on the axonal regeneration of axotomized retinal ganglion cells in adult hamsters. METHODS: The left optic nerve was transected intracranially or intraorbitally, and a peripheral nerve graft was apposed or sutured to the axotomized optic nerve to enhance regeneration. Trophic factors were applied intravitreally every 5 days. Animals were allowed to survive for 3 or 4 weeks. Regenerating retinal ganglion cells (RGCs) were labeled by applying the dye Fluoro-Gold to the distal end of the peripheral nerve graft 3 days before the animals were killed. RESULTS: Intravitreal application of ciliary neurotrophic factor substantially enhanced the regeneration of damaged axons into a sciatic nerve graft in both experimental conditions (intracranial and intraorbital optic nerve transections) but did not increase the survival of distally axotomized RGCs. Basic fibroblast growth factor and neurotrophins such as nerve growth factor, brain-derived neurotrophic factor, neurotrophin-3, and neurotrophin-4/5 failed to enhance axonal regeneration of distally axotomized RGCs. CONCLUSIONS: Neurons of the adult central nervous system can regenerate in response to trophic supply after injury, and ciliary neurotrophic factor is at least one of the trophic factors that can promote axonal regeneration of axotomized RGCs.     

玻璃体内细胞移植或细胞衍生物注入在视神经损伤中的作用

视网膜神经节细胞绝大部分位于神经节细胞层,可通过视神经通路将光感受器接收的视觉信息传递至高级视觉中枢,产生视觉。视网膜神经节细胞损伤和视神经轴突的中断,往往会导致视力下降甚至失明。近年来研究证实,玻璃体内细胞移植对损伤的视神经具有保护作用,为视神经损伤的修复治疗提供了新的方向。本文就玻璃体内细胞移植或细胞衍生物注入在视神经损伤中的作用展开综述。     

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.     

神经营养素家族因子对视网膜神经细胞保护作用的研究进展

现有大量研究表明神经营养素家族因子对视网膜神经细胞具有重要的保护作用。在所有家族成员中,神经生长因子能够有效保护视网膜光感受器细胞;阻断视网膜神经节细胞中神经生长因子与受体p75的结合,可以抑制神经节细胞的凋亡。脑源性神经营养因子可以防止光感受器细胞变性,增强光感受器细胞损伤后的修复。在刺激神经节细胞轴突生长和突触形成方面,脑源性神经营养因子、神经营养素-3及神经营养素-4/5均具有显著效应。通过对神经营养素家族因子的研究,了解其作用机制,以期能够应用于视网膜神经细胞变性及损伤性疾病的治疗中。     

CNTF gene transfer protects ganglion cells in rat retinae undergoing focal injury and branch vessel occlusion

Ciliary neurotrophic factor (CNTF) has been shown to protect ganglion cells in a variety of acute ischaemia models. Here we assess the efficacy of local CNTF gene transfer in protecting retinal ganglion cells when there is focal ischaemia combined with interruption of axoplasmic flow. This dual injury may be more representative of the pathological mechanisms operating in acute retinal diseases, such as vascular events acting at the optic nerve head. Fourteen rats received an intravitreal injection of an adeno-associated viral (AAV) vector expressing a secretable form of CNTF into the right eye and a control vector into the left eye. Three weeks later, each rat underwent a symmetrical small vertical 2mm standardised retinal crush injury approximately 2mm temporal to the optic disc. The injury also occluded the temporal retinal arteriole so that the axon crush was combined with an acute retinal infarction visible on fundoscopy. Changes in the damaged sector were compared histologically four weeks after injury and ganglion cell survival was estimated by comparing cell counts on retinal flat-mounts immunostained with RT-97 antibody. This mode of injury led to a profound loss of both the inner nuclear and ganglion cell layers, but was limited to the lesioned sector. In AAV.CNTF-treated eyes approximately 12% of ganglion cells survived compared with approximately 2% in control eyes (p=0.01). The scotopic electroretinogram (ERG), however, was reduced to about 50% in AAV.CNTF-treated eyes, both before and after injury. We therefore show that CNTF gene transfer confers neuroprotection to ganglion cells undergoing an acute ischaemic injury combined with interruption of axoplasmic flow. This approach may be relevant to optic nerve trauma and a variety of retinal vascular diseases that lead to swelling of the optic nerve head, provided CNTF can be delivered in a way that does not significantly suppress retinal function.     

视神经再生的实验研究进展

视神经是中枢神经的一部分，损伤后将无法再生，继而引起进一步视力损害。根据目前视神经损伤后视网膜神经节细胞（retinal ganglion cells，RGCs）轴突再生的基础研究，视神经损伤后必须采取以下有效措施:提高RGCs内在的再生潜力，改善生长抑制环境，优化RGCs神经再生，而诱导再生轴突靶向延伸是理想的促进视神经的再生与修复方式。本文查阅国内外最新实验性视神经再生研究类文献，从调控眼内炎症因子、提供合适外源性神秘生长因子、激活RGCs再生潜能、阻断抑制性轴突再生信号传导、给予适当的再生刺激信号、改善抑制性细胞外微环境等方面阐述促进视神经再生的研究现状，以期对早日实现基础研究成果尽快向临床应用转化有所帮助。     

磷酸二酯酶抑制剂调控小胶质细胞活化治疗青光眼的研究进展

青光眼是世界上发病率最高的不可逆致盲性眼病,主要表现为进行性的视网膜神经节细胞死亡、视神经萎缩和视野缺损.青光眼性神经节细胞死亡的机制复杂,小胶质细胞过度活化是重要因素之一.环磷酸腺苷(cAMP)与小胶质细胞活化密切相关.一方面,细胞浆内cAMP水平升高可以通过活化PKA/CREB信号通路抑制核因子κB的转录,从而减少...     

Chronology of optic nerve head and retinal responses to elevated intraocular pressure

PURPOSE: To determine the chronology of optic nerve head and retinal responses to elevated intraocular pressure (IOP). METHODS: After 1 to 39 days of unilaterally elevated IOP, experimental and fellow rat eyes were examined for morphology and immunohistochemical labeling alterations and for ganglion cell DNA fragmentation. RESULTS: Mean IOP for the experimental eyes was 36 +/- 8 mm Hg, an approximately 15-mm Hg elevation above normal values. By 7 days of pressure elevation above 40 mm Hg, endogenous immunostaining for brain-derived neurotrophic factor and neurotrophin 4/5 was absent from the nerve head and superior retina, whereas normal labeling was present in the inferior retina and distal optic nerve of these same eyes. These changes were preceded by a loss of gap junctional connexin43 labeling and astrocytic proliferation in the nerve head and by increased retinal ganglion cell layer apoptosis in the retina. Nerve head depletion of neurotrophins coincided with evidence of axonal degeneration, loss of astrocytic glial fibrillary acidic protein staining, and spread of collagen VI vascular immunolabeling. After longer durations at these same pressures, neurotrophin labeling returned to nerve head glia and scattered retinal ganglion cells. CONCLUSIONS: Optic nerve head and retinal responses, including the depletion of endogenous neurotrophins, are readily identified in the rat eye after experimental IOP elevation. However, the apparent chronology of these responses suggests that the withdrawal of neurotrophic support was not the only determinant of retinal ganglion cell apoptosis and axonal degeneration in response to pressure.