MULTIPRONGED APPROACH TO PROMOTE FUNCTIONAL AXONAL REGENERATION AFTER SCI

多管齐下促进 SCI 后功能性轴突再生

• 批准号: 9057394
• 负责人: Veronica Jean Tom
• 金额: $ 33.8万
• 依托单位: DREXEL UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-05-01 至 2019-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9057394
• 关键词: Address; Adult; Affect; American; Astrocytes; Axon; Behavioral; Cerebral Ischemia; Chondroitin ABC Lyase; Cicatrix; Clinical; Complex; Data; Distal; Embryonic Nervous System; Environment; Excitatory Synapse; Exogenous Factors; Extracellular Matrix; FRAP1 gene; Fiber; Glypican; Goals; Growth; Guanosine Triphosphate Phosphohydrolases; Health; Heparan Sulfate Proteoglycan; Histologic; In Vitro; Injury; Lead; Lesion; Mediating; Modeling; Motor; Natural regeneration; Nerve Degeneration; Nervous system structure; Neuraxis; Neurons; Pathway interactions; Peripheral Nerves; Persons; Physiological; Population; Property; Protein Biosynthesis; Public Health; Quality of life; Ras homolog enriched in brain; Recovery; Recovery of Function; Sensory; Site; Spinal Cord; Spinal cord injury; Synapses; Testing; Tissues; Translating; Work; axon growth; axon regeneration; clinical application; improved; improved functioning; in vivo Model; neurotrophic factor; novel; novel strategies; novel therapeutic intervention; postsynaptic; presynaptic; reinnervation; relating to nervous system; repaired; research study; response; synaptogenesis

DESCRIPTION (provided by applicant): While the mature central nervous system has an overall diminished capacity for regrowth compared to an embryonic nervous system, axonal regeneration of some populations is possible when they are provided with a potently growth-permissive environment, such as one conferred by a peripheral nerve graft (PNG). Still, axons that are capable of regenerating into the graft fail to grow beyond the PNG to reinnervate spinal cord, at least partly because of the presence of the inhibitory glial scar that is present at the graft-host interface. Digesting the inhibitory extracellular matrix within the scar with chondroitinase ABC (ChABC) allows some axons to traverse the distal interface, synapse upon distal neurons, and mediate some behavioral recovery. Nonetheless, most of the axons remain in the graft. Thus it is important to develop strategies that enhance the ability of axons to regenerate out of a graft in order to increase their potential to improve function. We have preliminary data indicating that expressing constitutively active Rheb (caRheb) - a GTPase that is a critical regulatory component of protein synthesis - in adult neurons results in robust axonal outgrowth in an in vitro glial scar model and in vivo after SCI. In Aim 1, we will test the hypothesis that expressing caRheb after SCI will enhance regeneration into and beyond a PNG. We will use histological, physiological, and behavioral analyses to examine if caRheb augments axonal regeneration - especially following ChABC treatment of the distal graft interface - and if these regenerated axons form functional synapses that facilitate behavioral recovery. Any regeneration is irrelevant if these axons do not integrate into circuits. Though ChABC enhances plasticity, ChABC-induced sprouted/regenerated fibers do not always form synapses to impact function. Thus, it is also important to devise strategies to improve integration of these axons (i.. synaptogenesis) in order to exploit regrowth that we encourage. We recently demonstrated the proof-of-principle that providing a single exogenous factor enhances the integration of axons that regenerate out of a PNG. Recent work indicates that secreted glypican is sufficient to promote functional, excitatory synapse formation in vitro and behavioral recovery in a cerebral ischemia model in vivo. In Aim 2, we will test the hypothesis that providing exogenous glypican will enhance synaptogenesis of regenerated axons following SCI. We will graft a PNG into a SCI site that has been treated with ChABC to promote axonal regeneration. We will determine if infusing exogenous glypican into tissue surrounding the SCI site enhances synaptogenesis of these regenerated axons upon neurons distal to the PNG. We will gauge improvements in functional synapse formation physiologically and histologically by examining the colocalization of pre- and postsynaptic markers. We will also assess if enhanced synapse formation correlates with behavioral recovery. Because the strategies to be tested in Aims 1 and 2 take different approaches - enhancing the growth response and synaptogenesis, respectively - to promote functional repair after SCI, it is possible that even if the results in the previous Aims are incremental, combining the two approaches will lead to greater recovery than either alone. In Aim 3, we will use a novel, multipronged strategy to fill the lesion cavity with a growth-promoting substrate (PNG), enhance the growth response (caRheb), modulate the inhibitory properties of the glial scar (ChABC) and promote synaptogenesis (glypican). We will use histological and physiological analyses to examine if glypican enhances the functional integration of axonal regeneration beyond a ChABC-treated PNG interface that is induced by expressing caRheb and if this results in more robust behavioral recovery than what occurs with either caRheb or glypican treatment separately. These data will identify new therapeutic strategies that may eventually be translated to clinical use to improve the quality of life of persons with SCI.

描述（由申请人提供）：虽然与胚胎神经系统相比，成熟的中枢神经系统的再生能力总体上降低，但当为某些群体提供有效的生长许可环境时，如外周神经移植物（PNG）所赋予的环境，它们的轴突再生是可能的。尽管如此，能够再生到移植物中的轴突不能生长到PNG之外以重新神经支配脊髓，至少部分是因为存在于移植物-宿主界面处的抑制性胶质瘢痕的存在。用软骨素酶ABC（ChABC）消化瘢痕内的抑制性细胞外基质，允许一些轴突穿过远端界面，在远端神经元上形成突触，并介导一些行为恢复。尽管如此，大部分轴突仍留在移植物中。因此，重要的是开发策略，增强轴突再生的能力，以增加其潜力，以改善功能的移植。我们有初步的数据表明，在成年神经元中表达组成型活性Rheb（caRheb）-一种GT3，是蛋白质合成的关键调控成分-导致了强大的轴突生长。 体外胶质瘢痕模型和SCI后体内的生长。在目标1中，我们将测试SCI后表达caRheb将增强PNG的再生的假设。我们将使用组织学，生理学和行为分析来检查caRheb是否增强轴突再生-特别是在ChABC治疗远端移植物界面后-以及这些再生的轴突是否形成促进行为恢复的功能性突触。如果这些轴突不能整合到回路中，任何再生都是无关紧要的。虽然ChABC增强可塑性，但ChABC诱导的发芽/再生纤维并不总是形成突触来影响功能。因此，设计策略来改善这些轴突的整合也很重要（即，突触发生），以利用我们鼓励的再生。我们最近证明了提供一个单一的外源性因素，增强了整合的轴突再生出PNG的原则证明。最近的工作表明，分泌型磷脂酰肌醇蛋白聚糖足以促进体外功能性兴奋性突触的形成和体内脑缺血模型中的行为恢复。在目标2中，我们将测试提供外源性磷脂酰肌醇蛋白聚糖将增强SCI后再生轴突的突触发生的假设。我们将把PNG移植到用ChABC处理过的SCI部位，以促进轴突再生。我们将确定是否注入外源性磷脂酰肌醇蛋白聚糖到周围的SCI网站的组织增强这些再生轴突的神经元远端的PNG突触。我们将通过检查突触前和突触后标记物的共定位，在生理学和组织学上评估功能性突触形成的改善。我们还将评估增强的突触形成是否与行为恢复相关。由于目标1和目标2中测试的策略采用不同的方法--分别增强生长反应和突触发生--来促进SCI后的功能修复，因此即使先前目标中的结果是渐进的，结合两种方法也可能比单独使用更好地恢复。在目标3中，我们将使用一种新颖的多管齐下的策略，用促进生长的 神经胶质瘤的作用包括抑制神经胶质基质（PNG）、增强生长反应（caRheb）、调节神经胶质瘢痕的抑制特性（ChABC）和促进突触发生（磷脂酰肌醇蛋白聚糖）。我们将使用组织学和生理学分析来检查磷脂酰肌醇蛋白聚糖是否增强了ChABC处理的PNG界面以外的轴突再生的功能整合，该界面由表达caRheb诱导，并且这是否导致比分别用caRheb或磷脂酰肌醇蛋白聚糖处理发生的行为恢复更稳健。这些数据将确定新的治疗策略，最终可能转化为临床应用，以改善SCI患者的生活质量。