Defining and modeling the cellular interactions for rhythmic colon motility

摘要：连续结肠运动对于机体的整体健康和生存至关重要， 肠神经系统（ENS）和Cajal间质细胞（ICC）的活动， 到平滑肌。虽然这些细胞成分已经被单独详细研究，但它们如何相互作用， 协调结肠长度上的运动性还不是很清楚。测量两种运动模式 实验：（1）ICC去极化慢波产生的“涟漪”收缩，以及（2）结肠移行 需要ENS活动的粪便内容物推进所必需的运动复合体。现有结肠模型 运动集中在远端区域，其中来自粪便颗粒的扩张激活了内在感觉神经元（或 IPAN），其刺激ENS运动神经元用于平滑肌的口腔收缩和肛门松弛; 小球的运动会扩张相邻的节段，激活另一个IPAN，这是神经机械的 “环”确保粪便内容物的繁殖和推进。然而，这些模型并不能解释常规的 结肠运动复合体的节律，每2-5分钟发生一次，或它们如何首先在近端结肠启动 粪便还没有形成不像运动复合体，只有当感觉 施加输入时，在近端区域发生自发的、有节奏的运动复合体，而不管腔内容， 拉伸或扩张，表明近端结肠具有独特的起搏器功能， 运动复合体的节律这个项目的目标是确定和模拟细胞的相互作用 近端结肠特有的，负责在正常和 发炎的情况。我们假设节律性运动复合体是由于ICC之间的周期性相互作用， IPAN和ENS的运动神经元，并且炎症期间的运动障碍是由于这些神经元的调节异常。 交互.为了测试这一点并解决知识缺口，我们将使用光遗传学，钙成像，原位 免疫荧光和计算机建模来定义负责细胞间相互作用的细胞间相互作用。 近端结肠中产生的自发的、有节奏的运动复合体，并决定细胞成分 导致炎症后运动节律紊乱。目标1将确定机械灵敏度 近端结肠IPAN对ICC产生的涟漪收缩。目标2将定义激活的“ENS神经程序” 在近端结肠产生运动复合体。目标3将确定ENS活性对 ICC慢波和涟漪收缩。每个目标将收集数据，从正常和发炎的结肠， 将被纳入我们的模型，以计算测试是否可以预测有关运动 基于细胞活动变化的行为。因此，这些研究将产生一种新的计算模型， 将有助于确定结肠疾病功能障碍的细胞机制，并指导治疗的优化。 采用起搏器技术或神经刺激以恢复结肠功能的器械。

ABSTRACT: Continuous colon motility is critical for the overall health and survival of an organism and results from activity in the enteric nervous system (ENS) and interstitial cells of Cajal (ICC) that are electrically-coupled to smooth muscle. Although these cellular components have been individually studied in detail, how they interact to coordinate motility across the length of colon is not well understood. Two motor patterns are measured experimentally: (1) ‘ripple’ contractions produced by ICC slow waves of depolarization, and (2) colon migrating motor complexes necessary for propulsion of fecal contents that require ENS activity. Existing models of colon motility are focused on distal regions where distension from a fecal pellet activates intrinsic sensory neurons (or IPANs) that excite ENS motor neurons for oral contraction and anal relaxation of smooth muscles; the forward movement of the pellet then distends the adjacent segment, activates another IPAN, and this ‘neuromechanical loop’ ensures propagation and propulsion of fecal contents. However, these models do not explain the regular rhythm of colon motor complexes, which occur every 2-5 min, or how they are first initiated in the proximal colon where fecal pellets have not yet formed. Unlike motor complexes that reach distal regions only when sensory input is applied, spontaneous, rhythmic motor complexes occur in proximal regions regardless of luminal content, stretch, or distension, indicating that the proximal colon has unique pacemaker capabilities that determine the rhythm of motor complexes. The objective for this project is to determine and model the cellular interactions unique to the proximal colon that are responsible for generating rhythmic motor complexes in normal and inflamed conditions. We hypothesize that rhythmic motor complexes are due to cyclical interactions among ICC, IPANs and motor neurons of the ENS, and that dysmotility during inflammation is due to dysregulation of these interactions. To test this and address knowledge gaps, we will use optogenetics, calcium imaging, in situ immunofluorescence, and computational modeling to define the cell-to-cell interactions responsible for spontaneous, rhythmic motor complexes produced in the proximal colon and determine the cellular components that contribute to dysrhythmic motility following inflammation. Aim 1 will determine the mechanical sensitivity of proximal colon IPANs to ICC-generated ripple contractions. Aim 2 will define the ‘ENS neural program’ activated by IPANs that produces motor complexes in proximal colon. Aim 3 will determine the effect of ENS activity on ICC slow waves and ripple contractions. Each Aim will collect data from normal and inflamed colons, and findings will be incorporated into our model to computationally test whether predictions can be made regarding motility behavior based on changes in cellular activity. Thus, these studies will yield a novel computational model that will help identify cellular mechanisms of dysfunction in colon diseases and guide optimization of therapeutic devices that employ pacemaker technology or nerve stimulation to normalize and restore colon function.