Neuro-muscular innervation in neonatal intestinal development

我们观察新生哺乳动物肠道的神经肌肉层的发育，它在达到成年大小之前会延长许多倍。这涉及到平滑肌细胞的广泛生长，以形成成人形态。然而，出生时就存在的肠神经系统（ENS）的神经元必须与之协调并发展成成人的神经支配模式，因为ENS最终将调节平滑肌的及时收缩和松弛，使正常的消化成为可能。我们的目标是了解神经元是如何在出生时保持活力并适应目标细胞的快速生长，从而创造出在成人中看到的复杂而稳定的关系。****目前的支持表明，一个单一的因子（GDNF；一种神经营养因子）负责出生后ENS神经元的存活，并且GDNF是由肠平滑肌细胞产生的。至关重要的是，这些细胞的生长是GDNF表达增加所必需的，从而导致神经元存活和轴突生长。我们认为，GDNF与其受体RET结合会导致两种结果：最初是存活，然后是轴突延伸，可能每种结果都需要不同水平的GDNF。我们有解决这个问题所需的细胞和分子技术，以及一个独特的组织培养模型，包括新生儿肠道神经元和平滑肌细胞。我们将通过阻断神经元（唯一表达GDNF受体的细胞）中不同通路的药物抑制剂分离GDNF信号传导的结果，然后测量细胞存活结果或轴突生长程度。然后我们将检查生长完成时神经元对GDNF的需求-非常低的水平是否能维持存活？这种信号是如何实现的？****在成人肠中似乎没有轴突生长，但当轴突生长以促进修复时，神经元不能很好地发挥作用，这在其他神经损伤中也可以看到。我们现在认为，新生儿ENS的轴突生长和神经功能（即动作电位和神经递质释放）往往不会同时发生。因此，随着神经递质的合成、储存和释放，随着功能程序的优势，结构程序变得完整。定量测量所涉及的步骤，如mRNA和蛋白质，将测量属于这些程序之一的关键蛋白质，这将与神经元显示成熟信号特性的能力相关。这将帮助我们了解肠道是如何在新生儿中发育的，这是一个知之甚少的领域。****我将与实习生一起工作，他们主要是研究生和大四本科生。他们将获得技术专长以及科学思维和批判性评价方面的教育。迄今为止，我们的毕业生都非常成功，在这一领域发表了重要的论文，并取得了非常好的职业成就。**********

We look at the development of the neuromuscular layer of the newborn mammalian intestine, which will lengthen many-fold before reaching its adult size. This involves extensive growth of the smooth muscle cells to create the adult form. However, the neurons of the enteric nervous system (ENS), which are all present at birth, must coordinate with this and develop the adult pattern of innervation, as the ENS will eventually regulate the timely contraction and relaxation of the smooth muscle that allows normal digestion. Our goal is to understand how neurons at birth stay alive and adapt to the rapid growth of their target cells, creating the complex, stable relationship seen in the adult.****Current support showed us that a single factor (GDNF; a neurotrophin) is responsible for survival of the ENS neurons after birth, and that GDNF is made by the intestinal smooth muscle cells. Critically, growth of these cells is required for increased GDNF expression that leads to neuron survival and axon outgrowth. We propose that the binding of GDNF to its receptor, RET, causes two outcomes: initially, survival and then axonal extension, and it may be that different levels of GDNF are required for each. We have the cellular and molecular techniques needed to address this, and a unique tissue culture model involving both neonatal intestinal neurons and smooth muscle cells. We will separate the outcomes of GDNF signalling with pharmacological inhibitors that block distinct pathways in the neurons (the only cells expressing GDNF receptors) , and then measure cellular outcomes of survival or the degree of axonal outgrowth. We will then examine the requirements of neurons for GDNF when growth is complete - do very low levels maintain survival? How is this signalling achieved?****Axonal outgrowth seems absent in the adult intestine, but when it arises to facilitate repair, the neurons do not function well, and this is seen elsewhere with nerve damage. We now think that axon outgrowth and nerve function in the neonatal ENS (ie, action potentials and neurotransmitter release) tend not to occur at the same time. Therefore, the structural programme becomes complete as the functional programme gains ascendancy, with synthesis, storage and release of neurotransmitters. Quantitative measurement of the steps involved, such as mRNA and protein, will measure key proteins that belong in either one of these programmes, and this will be correlated with the ability of the neurons to display mature signalling properties. This will help us to understand how the intestine develops in the neonate, a field where little is known.****I will work with trainees, who will mainly be graduate students as well as senior undergraduates. They will gain both technical expertise as well as education in scientific thinking and critical evaluation. To date, our graduates are highly successful, with significant publications in this field, and very good career achievements.**********