Pathophysiological remodeling of the enteric neuromuscular compartment in experimental spinal cord injury

摘要 脊髓损伤(Sci)最明显的物理效应是运动控制的丧失。 以及伤情水平以下的感觉。然而，神经源性肠病是最常见和临床上最常见的肠病之一。 公认的与脊髓损伤相关的合并症，表现为结肠传输减少，便秘， 排空不协调，大小便失禁。结肠调节失调被认为是一种终生的身体疾病 给脊髓损伤患者带来心理挑战，严重影响患者的生活质量。脊髓损伤与疾病的关系 储存和疏散缺陷促进了一种固有的倾向，即专注于失去脊柱上的监管 脊髓的躯体和自主神经回路。然而，胃肠道是独一无二的，因为它有自己的 广泛的内在神经系统，肠道神经系统(ENS)，并有能力发挥准 自主地。正常的结肠运输需要维持ENS和调节细胞的合体 收缩平滑肌以调节内在反射和协调肠道活动。虽然该函数 推测脊髓损伤后保留了一部分ENS，反射结肠传输的中断提示 否则的话。虽然神经源性肠道的病理生理学仍有待了解，但有关GI的研究 动力障碍提示肠神经元、Cajal间质细胞(ICC)和成纤维细胞样细胞的丢失 (FLC)可能是大多数这些疾病的潜在原因。这些细胞形成神经肌肉 调节所有平滑肌活动的界面。在这个提案中，我们将使用一个动物模型 T3-SCI结合分子和细胞技术以及活体神经生理学记录 目的探讨肠易激综合征后肠神经系统介导的结肠功能丧失机制。 SCI。我们的主要假设是脊髓损伤通过减少肠道运动而导致结肠运动障碍。 神经系统调节。我们将证明，活性氧物种(ROS)水平的升高 在肠道神经肌肉回路丧失之前，ROS清道夫将拯救这些细胞。基座 根据我们的初步观察，我们将检验这样的假设：1)脊髓损伤会降低神经肌肉 脊髓损伤后结肠平滑肌内的传递；2)脊髓损伤引起ENS神经元、ICC和 FLC(结肠合体的神经肌肉重塑)；3)脊髓损伤引起抗氧化防御受损 通过评估结肠内升高的ROS水平和降低的 血红素加氧酶1(HO1)，一个关键的抗氧化分子。我们最初的预期是胆碱能兴奋性 连接电位和抑制性(硝能和嘌呤能)连接电位将减少，从而 表现为肠道神经病变，引起结肠传输抑制。这些收敛的测试 中心假说将为研究脊髓损伤后炎症机制提供有价值的见解。 提供治疗策略以减少这种改变，从而改善结肠的功能结果 运动障碍。

ABSTRACT The striking physical effects of spinal cord injury (SCI) are most obviously observed as a loss of motor control and sensation below the level of injury. However, neurogenic bowel is one of the most prevalent and clinically recognized comorbidities associated with SCI and is manifested as diminished colonic transit, constipation, evacuation dyssynergy, and overflow incontinence. Colonic dysregulation is recognized as a lifelong physical and psychological challenge for SCI patients and gravely impacts quality of life. The association of SCI with storage and evacuation deficits promotes an inherent tendency to focus upon the loss of supraspinal regulation of somatic and autonomic circuitry of the spinal cord. However, the GI tract is unique in that it has its own extensive intrinsic nervous system, the enteric nervous system (ENS), and has the ability to function quasi- autonomously. Normal colonic transit requires maintenance of the ENS and a syncytium of cells regulating contraction of the smooth muscle to modulate intrinsic reflexes and coordinate gut activity. While the function of the ENS is presumed to be preserved following SCI, the disruption of reflex colonic transit suggests otherwise. While the pathophysiology of neurogenic bowel remains to be understood, studies focusing on GI motility disorders suggest that a loss of enteric neurons, interstitial cells of Cajal (ICC) and fibroblast-like cells (FLC) may be an underlying cause for the majority of these disorders. These cells form the neuromuscular interface through which all smooth muscle activity is regulated. In this proposal we will use an animal model of T3-SCI combined with molecular and cellular techniques as well as in vivo neurophysiological recordings in an aim to define the mechanisms resulting in the loss of enteric nervous system-mediated colonic function post- SCI. Our overarching hypothesis is that spinal cord injury induces colonic dysmotility by reducing the enteric nervous system regulation. We will demonstrate that elevated levels of reactive oxygen species (ROS) precedes the loss of enteric neuromuscular circuits and that ROS scavengers will rescue these cells. Based upon our preliminary observations, we will test the hypothesis that 1) SCI decreases neuromuscular transmission within the colonic smooth muscle after SCI; 2) SCI provokes the loss of ENS neurons, ICC and FLC (neuromuscular remodeling of the colonic syncytium); and 3) SCI provokes impaired anti-oxidant defense of the proximal and distal colon by evaluating elevated ROS levels within the colon and diminished levels of heme oxygenase 1 (HO1), a key anti-oxidant molecule. Our initial expectation is that cholinergic excitatory junction potentials and inhibitory (nitrergic and purinergic) junction potentials will be reduced, thus demonstrating an enteric neuropathy provoking inhibition of colonic transit. These convergent tests of the central hypothesis will provide valuable insight into the inflammatory mechanisms which occur post-SCI and offer therapeutic strategies to reduce such alterations, thereby improving the functional outcome of colonic dysmotility.