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枝的细胞，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、抽血或消化食物。Tau蛋白是一种神经细胞蛋白，它使神经元能够将必要的蛋白质分配到大脑、脊髓和神经元中调节感觉和控制内脏器官活动的细胞的远程部分。在阿尔茨海默氏症中，tau失去了正常的功能；它变得错误折叠，最终形成神经原纤维缠结(NFT)，这被认为是疾病中神经退化的关键。目前，有20多种不同的人类神经退行性疾病表现出NFT，其中一些是由编码tau的基因的单一突变引起的。这一观察表明，tau的突变形式足以导致神经退行性疾病。然而，在许多情况下，tau没有突变，但它仍然形成缠结。因此，tau是一个重要的治疗靶点。关于tau的病理变化已经知道了很多，但一个基本的问题仍然没有答案：什么形式的tau是真正的病理性的，tau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的神经系统来解决，因为很难捕捉到濒临死亡的神经细胞，因为死亡的神经细胞会被邻近的细胞迅速清除。出于这个原因，已经建立了牵牛症的小鼠模型，其中复制了这种疾病的几个特征。然而，即使是在老鼠身上，大脑中濒临死亡的细胞也不容易接触到。为了减少动物使用，同时仍然能够研究tau是如何杀死细胞的，我们转向了感觉神经系统神经细胞的细胞培养系统。耐人寻味的是，随着时间的推移，培养的神经元会发展出tau病理的各个方面。此外，那些表达tau病理形式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来研究tau病理的原因和机制。同时，减少、提炼和替换大量的小鼠，否则这项研究是必要的。我们现在知道，细胞死亡不一定是一个随机的过程。它可能涉及到对牢房的有序拆除。在这里，我们建议发展这个模型来确定tau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，这个模型将减少老鼠在旨在解开tau为什么使神经细胞失效并导致它们死亡的谜团的研究中的使用。

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.