Life and death in injured chick spinal cord with development: a functional genomics and proteomics approach

哺乳动物和鸟类的成年中枢神经系统（脑和脊髓）损伤，无论是由于侮辱还是由于疾病，通常会导致不可逆的损伤和严重的残疾。相反，在幼小的胚胎以及某些鱼类和两栖动物中，中枢神经系统能够再生。有几个因素可能导致再生能力的丧失，对它们的识别可能有助于我们理解为什么这种能力会丧失，以及如何恢复这种能力。中枢神经系统修复的一个关键条件是要么在受伤的神经元中保持较高的存活率，要么能够产生新的神经元，在适当的环境提示下，这些神经元将重新生长它们的过程并重新建立适当的连接。这些事件通常不会发生在鸟类和哺乳动物的成年中枢神经系统中，它们的损伤会导致神经元的广泛死亡，以及化学和形态变化，从而损害存活神经元的轴突再生。然而，在胚胎中，即使是相当发达的脊髓也可以再生，尽管这种能力最终会在发育后期丧失。目前，再生和非再生脊髓之间差异的分子机制尚不完全清楚。我们希望使用现代技术，使我们能够识别差异表达的基因和蛋白质，以确定在正常脊髓发育的再生能力和不再生能力阶段之间发生的分子变化，并以小鸡为模型对损伤做出反应。鸡胚的巨大优势在于，它易于获取，易于在鸡蛋中进行操作（可以在鸡蛋中切开一个窗口，然后在手术/药物治疗后用胶带关闭），这将使我们能够测试在筛选中确定的分子的作用。我们预计，我们的筛选将确定几个分子在发育阶段对损伤的反应中受到不同的调节，允许和不允许再生。我们将选择其中的一些分子进行功能研究，最初将重点放在那些可能参与的分子上：1)控制细胞是存活还是死亡；2)控制神经发生（新神经元的形成）。例如，我们将评估是否可以通过适当的药物调节这些分子的活性来增加神经细胞的存活和/或神经发生。识别在这些过程中起作用的分子，并在使用刺激目标神经生长的药物治疗之前通过药理学调节来增加神经元数量，是实现显著神经修复的关键一步。

Injury of the adult central nervous system (brain and spinal cord) of mammals and birds, due either to insult or disease, usually leads to irreversible damage and severe disability. In contrast, in young embryos and in certain fish and amphibia the central nervous system is able to regenerate. Several factors are likely to contribute to loss of regenerative ability and their identification may help us to understand why such capability is lost and how it may be recovered. A key requisite for central nervous system repair is either to maintain a high rate of survival in injured neurons or to be able to produce new neurones that, given appropriate environmental cues, will then re-grow their processes and re-establish the appropriate connections. These events do not usually occur in the adult central nervous system of birds and mammals where injury causes extensive death of neurones, and chemical and morphologoical changes which impair axonal regrowth from surviving neurones. In the embryo however, even a rather well developed spinal cord can regenerate, though eventually this capability is lost at late stages of development. At present the molecular mechanisms underlying the differences between regenerating and non regenerating spinal cords are not fully understood. We wish to use modern techniques that allow us to identify genes and proteins that are differentially expressed to define the molecular changes occurring at the transition between regeneration-competent and incompetent stages of development in normal spinal cord and in response to injury using the chick as a model. The great advantage of the chick embryo is that, being easily accessible, it is amenable to manipulations in ovo (a window can be cut in the egg and then closed with cellotape after surgery/ pharmacological treatments) and will allow us to test the role of molecules identified in our screenings. We anticipate that our screenings will identify several molecules that are differently regulated in response to injury at developmental stages permissive and non-permissive for regeneration. We will select some of these molecules for functional studies, initially focusing on those likely to be involved in i) controlling whether a cell is going to survive or die and ii) controlling neurogenesis (formation of new neurones). For example, we will assess whether we can increase neural cell survival and / or neurogenesis by modulating the activity of these molecules with appropriate drugs. Identification of molecules that play a role in these processes, and that can be modulated pharmacologically to increase neurone numbers before treatment with agents which can stimulate targeted nerve growth, is a key step towards attaining significant neural repair.