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: 9275033
• 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/9275033
• 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; Heparan Sulfate Proteoglycan; Histologic; In Vitro; Injury; 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; enhancing factor; experimental study; improved; improved functioning; in vivo; in vivo Model; neurotrophic factor; novel; novel strategies; novel therapeutic intervention; permissiveness; postsynaptic; public health relevance; reinnervation; relating to nervous system; repaired; 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有所下降，但当为某些人群提供强大的生长许可环境时，例如周围神经移植（PNG）所赋予的环境，轴突再生是可能的。然而，能够再生成移植物的轴突不能生长到PNG以外的脊髓再神经支配，至少部分原因是移植物-宿主界面存在抑制性胶质瘢痕。用软骨素酶ABC （ChABC）消化疤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，开发增强移植物轴突再生能力的策略以增加其改善功能的潜力是很重要的。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GTPase，是蛋白质合成的关键调节成分-导致强大的轴突