Functional Restoration of the Optic Nerve After Disease or Damage

描述(申请人提供)：本研究计划的长期目标是结合神经解剖学、细胞生物学和小鼠行为测试的方法，探索调节视神经再生和损伤或疾病后恢复视力的机制。视神经损伤是几种致盲疾病的主要特征，如青光眼、视神经病变和创伤。寻找拯救视网膜神经节细胞免于变性和促进视神经再生的方法对于开发针对这些疾病的有效治疗方法至关重要。此前，利用已建立的视神经切断模型和小鼠基因技术，我们发现了视神经再生的两个障碍：星形胶质细胞的表达缺失和成熟以及形成胶质瘢痕的能力的获得。通过消除这两个障碍，首次在小鼠中成功地将视神经重新延伸到大脑靶点，直到出生后第14天(P14)。有趣的是，出生后的小鼠再生的轴突进入了错误的(同侧)大脑，并对那里的视觉目标进行了神经支配。然而，如果损伤是在P14之后发生的，再生一直失败，这表明在这个年龄段出现了更多的障碍来阻碍神经再生。剩下的关键问题是：(1)P14后视神经再生的额外障碍是什么，成年后能否成功再生切断的视神经，以及(2)再生的轴突是否能够建立地形图和与靶神经元的功能性突触，进而恢复视力。我的实验室最近的研究表明，视神经再生的第三个也可能是最后一个障碍的出现与中枢神经系统髓鞘的发育有关。我们推测，视神经再生的三个障碍包括视网膜神经节细胞表达Bcl2的缺失、胶质瘢痕的形成和中枢神经系统髓鞘的出现；同时消除这三个障碍将使成年人的视神经再生和视力恢复。这项研究计划的三个具体目标包括：(1)确定同时消除阻碍视网膜神经节轴突再生的三个障碍是否能够使成年人的视神经再生。(2)利用EphB1基因敲除小鼠模型，探讨EphB1在视网膜神经节细胞轴突再生过程中对同侧投射的指导作用。(3)通过神经解剖学、视觉诱发电位和动物行为学测试，研究再生的RGC轴突是否能够建立局部有序的功能联系，从而导致视力恢复。这项研究的结果可能会为使用神经移植治疗失明和其他中枢神经系统疾病提供一种新的策略。 项目简介：视神经损伤无法修复是几种致盲疾病的主要特征，包括青光眼、视神经炎、多发性硬化症以及创伤。我们目前的研究计划是为了识别和缓解视神经再生的所有障碍。这些拟议研究的结果将为未来疾病或损伤后视神经损伤的治疗策略的发展打开大门。

DESCRIPTION (provided by applicant): The long-term objectives of this research plan are to combine approaches of neuroanatomy, cellular biology and mouse behavior tests to probe for mechanisms regulating optic nerve regeneration and restoring vision after injury or diseases. Optic nerve damage is a major feature of several blinding diseases, such as glaucoma, optic neuropathy, and trauma. Finding ways to rescue retinal ganglion cells from degeneration and to promote optic nerve regrowth are crucial to the development of efficacious treatment for these conditions. Previously, using the established model of optic nerve axotomy and mouse genetic technology, we identified two barriers to optic nerve regeneration the loss of Bcl-2 expression and maturation of astrocytes and their acquisition of the ability to form glial scars. By eliminating these two barriers demonstrated for the first time successful optic nerve re-elongation into the brain targets, up to postnatal day 14 (P14) in mice. Interestingly, regenerating axons in the postnatal mice entered the wrong (ipsilateral) side of the brain and innervated the visual targets in there. However, the regeneration fails consistently if the injury is incurred after P14, suggestion development of additional barriers to nerve regrowth at this age. The key remaining questions are: (1) what is the additional barrier to optic nerve regeneration that is developed after P14 and whether successful regeneration of the severed optic nerve can be achieved in the adult, and (2) whether regenerated axons are capable of establishing a topographic map and functional synapses with target neurons and in turn restoring vision. Recent studies in my laboratory implicate that appearance of the third and likely the last barrier to optic nerve regeneration is related to the development of CNS myelin. We hypothesize that the three barriers to optic nerve regeneration include the loss of Bcl-2 expression by retinal ganglion cells, development of glial scars, and appearance of CNS myelin; simultaneous elimination of the three barriers will allow optic nerve regeneration and restoration of vision in the adult. The three specific aims of this research plan includes: (1) To determine if simultaneous eliminating the three barriers to retinal ganglion axonal regrowth will enable optic nerve regeneration in the adult. (2) To determine a role for EphB1 in directing the ipsilateralization projection of retinal ganglion cell axons during regeneration, using the model of EphB1 knockout mice. (3) To investigate whether regenerated RGC axons are capable of establishing topographically ordered functional connections that can lead to vision restoration, using neuroanatomy, visual evoked potential, and animal behavioral tests. The results of this study may lead to a novel strategy for using neural transplantation to treat blindness and other CNS diseases. Project Narrative: Failure of optic nerve injury to be repaired is a major feature of several blinding diseases, including glaucoma, optic neuritis, and multiple sclerosis, as well as trauma. Our present research plan is proposed to identify and alleviate all barriers to optic nerve regeneration. The results of these proposed studies will open the door for future development of treatment strategies for optic nerve damage after disease or injury.