Applying the 3Rs to elucidate the mechanisms of tau pathology using DRG neurons in culture

神经细胞是复杂的高度分支的细胞，对我们的大脑和身体的功能至关重要。没有神经细胞，我们就不能思考、感觉、行走、泵血或消化食物。tau蛋白是一种神经细胞蛋白，它使神经元能够将必需蛋白质分布到大脑，脊髓和神经元中细胞的远端部分，这些神经元介导感觉并控制我们内部器官的活动。在阿尔茨海默病中，tau蛋白停止正常发挥功能;它变得错误折叠并最终形成神经元缠结（NFT），这被认为是疾病中神经退行性变的关键。目前，有超过20种不同的人类神经退行性疾病显示NFT，其中一些是由编码tau的基因中的单一突变引起的。这一观察结果表明，tau蛋白的突变形式足以引起神经变性疾病。然而，在许多情况下，tau没有突变，但它仍然形成缠结。因此，Tau是重要的治疗靶点。关于tau蛋白发生的病理变化，我们已经知道了很多，但有一个基本问题仍然没有答案：什么形式的tau蛋白是真正的病理性的，以及tau蛋白是如何导致神经细胞死亡的？这些问题很难通过观察死后人脑中的神经系统来解决，因为很难捕捉到垂死的神经细胞，因为死亡的神经细胞会被邻近的细胞迅速清除。由于这个原因，已经建立了tau蛋白病的小鼠模型，其中复制了该疾病的几个特征。然而，即使在小鼠中，大脑中垂死的细胞也不容易接近。为了减少动物使用，同时仍然能够研究tau蛋白如何杀死细胞，我们转向了感觉神经系统神经细胞的细胞培养系统。有趣的是，随着时间的推移，培养的神经元会发展出tau病理学的各个方面。此外，那些表达病理形式的tau蛋白的神经细胞会继续死亡。这使我们能够接触到单个神经细胞，以研究tau病理学的原因和机制。与此同时，减少、改进和替换大量的小鼠，否则这些小鼠将是这项研究所必需的。我们现在知道细胞死亡不一定是一个随机的过程。它可以包括有序地拆除细胞。在这里，我们建议开发这个模型来确定tau蛋白导致神经细胞病理和死亡的途径。我们还希望探索是否可以使用正在开发的最终用于人类的药物来保持患病神经细胞的存活。而且，重要的是，这种模型将减少在旨在解决为什么tau蛋白使神经细胞丧失功能并导致它们死亡的研究中使用小鼠。

Nerve cells are complicated highly branched cells that are essential for our brains and our bodies to function. Without nerve cells we cannot think, feel, walk, pump blood or digest our food. The protein tau is a nerve cell protein that enables neurons to distribute essential proteins to distant parts of the cell in the brain, spinal cord, and in neurons that mediate sensation and control the actions of our internal organs. In Alzheimer's disease, tau ceases to function normally; it becomes misfolded and eventually forms neurofibrillary tangles (NFT) that are thought to be critical for neurodegeneration in the disease. Currently there are over 20 different human neurodegenerative diseases that show NFT, some of which are caused by a single mutation in the gene that codes for tau. This observation demonstrates that mutant forms of tau are enough to cause neurodegnerative disease. However, in many cases tau is not mutated, yet it still forms tangles. Tau is therefore an important therapeutic target. Quite a lot is known about pathological changes that occur in tau but one fundamental problem is still unanswered: what form of tau is truly pathological and how tau causes the nerve cells to die? These problems are difficult to solve by looking at the nervous system in post mortem human brains because it is difficult to catch a dying nerve cell as dead nerve cells are rapidly cleared by neighbouring cells. For this reason mouse models of tauopathy have been created where several features of the disease are replicated. However, even in mice, the dying cells in the brain are not easily accessible. To reduce animal use and still be able to investigate how tau kills cells, we have turned to a cell culture system of nerve cells from the sensory nervous system. What is intriguing is that the neurons that are cultured develop aspects of tau pathology as time goes by. Moreover, those nerve cells that express pathological forms of tau go on to die. This allows us to gain access to individual nerve cells to study the causes and mechanisms of tau pathology. and at the same time, reduce, refine, and replace a large number of mice that would have been otherwise necessary for this study. We now know that cell death is not necessarily a random process. It can involve the orderly demolition of the cell. Here we propose to develop this model to determine the pathways by which tau causes nerve cell pathology and death. We also wish to explore whether we can keep the sick nerve cells alive using drugs that are being developed for eventual use in humans. And, importantly, this model will reduce use of mice in research aimed at solving the mystery of why tau disables nerve cells and causes them to die.