Modulating microglial phenotype to prevent SCI-induced central neuropathic pain

脊髓损伤（SCI）患者中有相当比例（40-50%）表现出中枢神经性疼痛 (CNP)，一种持续不适的状况，通常涉及无法忍受的灼烧、刺痛、射击和/或诱发的疼痛。 对轻触的反应。CNP在女性中更常见，女性也表现出更大的 对疼痛的敏感性。CNP响应于躯体感觉信号传导的失调而发展， 传统的治疗干预很难治愈，只有40-60%的人获得部分缓解。 因此，CNP仍然是一个主要的未满足的临床挑战，不仅对于SCI，而且对于许多其他神经系统疾病 条件，包括多发性硬化症，中风和创伤性脑损伤，其患病率一直是 观察尽管包括先天免疫系统、小胶质细胞和巨噬细胞的细胞的激活， 已被确定为CNP发展和持久性的关键效应子，通过其产生一种 尽管这些细胞是疼痛和可塑性调节因子的集合，但这些细胞的免疫表型特征仍然很差 在存在或不存在CNP的条件下，在SCI中表征。最近的工作已经 强调了经典活化的M1小胶质细胞-巨噬细胞表型在有害的 与损伤相关的过程，包括炎症、细胞死亡和轴突再生失败，而 交替激活的M2形式，其在功能上促进组织重塑、血管生成、轴突生长和 髓鞘再生在慢性病变中基本上不存在。活化的小胶质细胞和 直接损伤外的神经轴区域内的巨噬细胞，例如腰脊髓， 其中伤害感受和抗伤害感受系统处理中发生生理变化，包括增加 然而，背角神经元的过度兴奋和GABA能神经传递的丧失/抑制， 未知此外，SCI后小胶质细胞和巨噬细胞表型的表征在动物中， 尚未研究是否存在CNP，也未研究M1的治疗靶向， 评价了M2表型转化作为预防CNP发展或持续性的方法。 拟议的调查将采用临床相关的挫伤范例，研究时间和 存在和不存在CNP的SCI动物中的空间M1和M2群体动态，如以下所示： 疼痛行为（具体目标1）。这个范例将使我们开始理解特定的 小胶质细胞表型在CNP的发展和持续性以及性别对这些的影响 应答随后，通过使用一种新的和有效的M1到M2的转换协议， 我们的实验室，我们将进一步解决这个问题，通过检查是否M1小胶质细胞转化为M2 a或 M2 c表型可预防CNP的发生或降低其严重程度（特定目的2）。集体 这些研究将为小胶质细胞和巨噬细胞的特定表型形式所起的作用提供新的见解。 在CNP中，性别如何影响这些免疫反应和CNP的发展，以及提供一个假定的 减轻SCI后CNP的治疗方向。

A significant percentage (40-50%) of individuals with spinal cord injury (SCI) exhibit central neuropathic pain (CNP), a condition of persistent discomfort involving often unbearable burning, pricking, shooting and/or evoked types of pain in response to light touch. CNP appears more frequently in females, who also exhibit a greater sensitivity to pain than males. CNP develops in response to a dysregulation of somatosensory signaling and is largely refractory to conventional therapeutic interventions with only 40-60% of people achieving partial relief. Therefore CNP remains a major unmet clinical challenge, not only for SCI but numerous other neurological conditions, including Multiple Sclerosis, stroke and traumatic brain injury where its prevalence has been observed. Though the activation of cells comprising the innate immune system, microglia and macrophages, has been identified as key effector in the development and persistence of CNP, through their production of a repertoire of pain and plasticity modulating factors, the immunophenotypical identity of these cells remains poorly characterized in SCI under conditions in which there is the presence or absence of CNP. Recent work has highlighted the importance of the classically-activated M1 microglia-macrophage phenotype in the deleterious processes associated with injury including inflammation, cell death and abortive axon regeneration, while the alternatively-activated M2 form, which functionally promotes tissue remodeling, angiogenesis, axon growth and remyelination, is largely absent from chronic lesions. The phenotypic identity of activated microglia and macrophages within regions of the neural axis outside of the immediate injury, such as the lumbar spinal cord, where physiological changes in nociceptive and anti-nociceptive system processing occurs, including increased hyperexcitability of dorsal horn neurons and the loss/inhibition of GABAnergic neurotransmission, however, is unknown. Furthermore, the characterization of microglia and macrophage phenotype after SCI in animals where there is an absence or presence of CNP has not been investigated nor has the therapeutic targeting of M1 to M2 phenotypic conversion as an approach to preventing CNP development or persistence been evaluated. The proposed investigation will employ a clinically-relevant contusion paradigm to study temporally and spatially M1 and M2 population dynamics in SCI animals in which CNP is present and absent as evidenced by pain behaviors (Specific Aim 1). This paradigm will allow us to begin to understand the involvement of specific microglia phenotypes in the development and persistence of CNP as well as the influence of gender on these responses. Subsequently, through the use of a novel and potent M1 to M2 conversion protocols established in our laboratory, we will further address this question by examining if the conversion of M1 microglia to a M2a or M2c phenotype can either prevent the development of CNP or reduce its severity (Specific Aim 2). Collectively these studies will provide novel insight into the role specific phenotypic forms of microglia and macrophages play in CNP, how gender influences these immune responses and the development of CNP as well as offer a putative therapeutic direction for attenuating CNP after SCI.