Nigrostriatal Tract Reconstruction

描述（由申请人提供）：这个探索性项目旨在推进一个意想不到的发现，该发现来自我们的项目拨款，旨在改善帕金森病非人类灵长类动物的拨款功能。作为设计的一部分，我们测试了“辅助”移植物刺激和引导含有多巴胺能神经元的腹侧中脑移植物的神经突延伸的能力。我们发现来自多巴胺神经元的神经突可以在脑干和纹状体之间架起桥梁，它们可以从一个遥远的辅助移植物延伸到第二个，最终延伸到位于纹状体的第三个。这是关于重建黑质纹状体通路要素的一个重要发现，因为它将移植的多巴胺神经元置于中脑，在那里它们有机会通过适当的传入输入进行接触。在动物模型和人类中，帕金森病的移植治疗都利用纹状体作为多巴胺能神经元的移植部位。虽然这种方便的放置导致多巴胺直接释放到纹状体目标神经元区域，但其缺点是它将供体神经元置于远离正常途径的位置。在一些临床试验中，最初表现出一定程度的运动改善的患者最终表现出运动障碍，这被认为是由于移植物不受控制或过度释放多巴胺所致。有趣的是，我们使用纹状体“辅助”移植在非人灵长类动物的吻侧中脑和尾侧纹状体之间架起了相对较长的距离，并保持了解剖的纹状体角素块在尾侧到吻侧的正确位置。因此，多巴胺神经突首先到达发育中的纹状体尾部部分，然后在吻侧方向继续生长，到达纹状体供体移植物的第二部分，即后来发育的中间部分。最终，纤维到达位于宿主纹状体的第三纹状体“台阶”。我们假设纹状体存在从尾侧到吻侧的发育梯度，通常引导多巴胺纤维从脑干接近纹状体，纹状体生长因子活性的递进波存在，以解释这些纤维持续延伸到纹状体内最远的部位。因此，我们建议在对非人类灵长类动物进行进一步探索之前，先在啮齿动物中进行测试。该计划项目拨款不会提交续期，这是P01执行委员会的决定，如果啮齿动物的探索性提案获得批准并证明是成功的，那么我们将利用这一信息计划在非人类灵长类动物中进行额外的测试，在行为受损的动物中进行辅助移植物电路重建，作为未来可能的R01。公共卫生相关性：该研究有潜力确定多巴胺能通路的成功电路重建的关键援助，该通路负责帕金森病的体征和症状的表现。我们对非人类灵长类动物的早期研究提供了一个新的发现，在进一步研究更复杂的灵长类动物之前，可以在啮齿动物模型中进行更充分的测试。我们认为更完整的电路重建是优化接枝功能的关键。

DESCRIPTION (provided by applicant): This exploratory project is designed to advance an unexpected finding that resulted from our program project grant on improving grant function in parkinsonian non-human primates. As part of the design we tested the ability of "helper" grafts to stimulate and guide the extension of neurites from grafts of ventral mesencephalon that contained dopaminergic neurons. We found that neurites from dopamine neurons could bridge the distance between the brain stem and the striatum and that they could extend from one distant helper graft to a second and ultimately to a third that was located in the striatum. This is an important finding with respect to the potential for reconstruction of elements of the nigrostriatal pathway because it places the grafted dopamine neurons in the mesencephalon where they have the opportunity to be contacted by appropriate afferent inputs. Graft therapy for Parkinsonism in both animal models and humans has utilized the striatum as the graft site for placement of dopaminergic neurons. While this convenient placement resulted in the release of dopamine directly into the region of the striatal target neurons, its shortcoming is that it places the donor neurons in a position that is removed from the normal pathway. In some clinical trials patients who initially showed some level of motor improvement eventually showed dyskinesias that are postulated to be due to uncontrolled or excessive release of dopamine by the grafts. The interesting thing about our finding is that we used striatal "helper" grafts to bridge the relatively long distance between the rostral mesencephalon and caudal striatum in the non-human primate and maintained the correct caudal to rostral position of the dissected pieces of the striatal anlagen. Thus, the dopamine neurites first reached the developing caudal portion of the striatum, and then somewhat remarkably continued to grow in a rostral direction to reach the second, later developing middle portion of the striatal donor graft. Ultimately, the fibers reached the third striatal "step" which was located in the host striatum. We hypothesize that a developmental gradient exists for the striatum from caudal to rostral that normally guides dopamine fibers that approach the striatum from the brain stem, and that a progressive wave of striatal growth factor activity exists to account for the continued extension of these fibers to reach the most distant sites within the striatum. Thus, we propose to test this in rodents prior to any further exploration in non-human primates. The program project grant is not going to be submitted for renewal which is a decision made by the executive committee of the P01 and if this exploratory proposal in rodent is awarded and proves successful then we will utilize this information to plan additional tests in the non-human primate of helper graft circuit reconstruction in behaviorally impaired animals as a possible future R01. PUBLIC HEALTH RELEVANCE: The proposed study has the potential to identify a key aid for successful circuit reconstruction of the dopaminergic pathway that is responsible for the manifestation of the signs and symptoms of Parkinson's disease. Our earlier studies in non-human primates provided a novel finding that can be tested more fully presently in a rodent model prior to moving forward with the more complex primate. We believe that more complete circuit reconstruction is crucial for optimizing graft function.