Overcoming glial scar inhibitions on axonal growth

描述（由申请人提供）：在中枢神经系统轴索损伤后，促进神经功能缺损恢复的医学治疗非常有限。不允许轴突生长的环境至少部分导致了成人中枢神经系统的生长衰竭。具体来说，几组抑制分子强烈抑制中枢神经系统病变后的轴突延伸，包括胶质疤痕产生的硫酸软骨素蛋白多糖（CSPGs）。CSPGs是神经胶质瘢痕的主要抑制成分，是轴突再生的主要障碍。尽管已有几种策略被报道，但通过局部应用细菌软骨素酶ABC消化CSPGs是克服CSPGs在中枢神经系统损伤后生长抑制的主要体内方法。然而，这种酶的一些重要缺点阻碍了它作为轴突损伤患者的治疗选择，包括从CSPGs中去除抑制成分不完全，在体温下酶活性短，不能穿过血脑屏障。在本提案中，我们的目标是开发基于单独抑制CSPGs或与我们先前确定的方法相结合的治疗中枢神经系统轴索损伤的新策略。我们假设CSPGs的肽拮抗剂将增强CNS损伤小鼠模型的形态和功能恢复。使用生物信息学方法来定义几种CSPGs的保守元件，我们已经确定了CSPGs的两种选择性肽拮抗剂。我们的初步研究表明，这些低纳摩尔浓度的肽主要克服了神经元培养中CSPGs的神经突生长限制。体内系统应用cspg阻断肽可显著改善CNS轴突损伤小鼠的行为恢复。在本研究中，我们将表征这些CSPG拮抗肽在小鼠脊髓损伤（SCI）模型中的治疗潜力。除CSPGs外，许多抑制分子通过激活聚合RhoA或糖原合成酶激酶32 （GSK-32）参与细胞内轴突生长抑制。最近，我们已经证明，布洛芬或GSK-32加锂灭活RhoA克服了不同分子的生长抑制，显著促进了脊髓损伤啮齿动物下行运动神经元轴突生长和运动恢复。因此，我们还旨在通过将cspg阻断肽与抑制rhoa的布洛芬或gsk -32灭活锂这两种广泛用于人类的药物联合使用，来刺激脊髓损伤小鼠更显著的轴突再生。使用我们的新型CSPGs拮抗剂，单独或与布洛芬或锂联合使用，可能通过促进轴突再生和功能恢复，显著提高我们治疗成年哺乳动物中枢神经系统轴突损伤的能力。

DESCRIPTION (provided by applicant): After CNS axonal injuries, medical treatments to enhance recovery from neurological deficits are extremely limited. Non-permissive environments for axonal growth at least partially contribute to growth failure in the adult CNS. Specifically, several groups of inhibitory molecules strongly suppress axonal extension following CNS lesions, including chondroitin sulfate proteoglycans (CSPGs) generated by glial scars. CSPGs are the principal inhibitory components of glial scars and form a major barrier to regenerating axons. Although several strategies have been reported, digestion of CSPGs with local application of bacterial chondroitinase ABC is the major in vivo approach to surmount growth inhibition of CSPGs after CNS injuries. Important disadvantages, however, preclude the use of this enzyme as a therapeutic option for axonal injury patients, including incomplete removal of inhibitory components from CSPGs, short-period of enzymatic activity at body temperature and inability to cross the blood-brain barrier. In this proposal, we aim to develop novel strategies for treating CNS axonal injury based on inhibition of CSPGs alone or in combination with our previously identified approaches. We hypothesize that peptide antagonists of CSPGs will augment both morphological and functional recovery in a mouse model of CNS injury. Using a bioinformatics approach to define the conserved elements of several CSPGs, we have identified two selective peptide antagonists for CSPGs. Our preliminary studies suggest that these peptides at low nanomolar concentrations principally overcome neurite growth restrictions of CSPGs in neuronal cultures. Systemic application of a CSPG-blocking peptide significantly improves behavioral recovery in CNS axon-injured mice in vivo. In this study, we will characterize the therapeutic potential of these CSPG antagonistic peptides in mouse spinal cord injury (SCI) model. In addition to CSPGs, a number of inhibitory molecules contribute to axonal growth suppression intracellularly mediated via activation of convergent RhoA or glycogen synthase kinase 32 (GSK-32). Recently, we have demonstrated that inactivation of RhoA with ibuprofen or GSK-32 with lithium overcomes growth inhibition of different molecules and significantly promotes axonal growth of descending motor neurons and locomotor recovery in SCI rodents. Thus, we also aim to stimulate a more dramatic axonal regeneration in SCI mice by combining a CSPG-blocking peptide with RhoA-inhibiting ibuprofen or GSK-32-inactivating lithium, two drugs widely used in humans. The use of our novel antagonists for CSPGs, alone or in combination with ibuprofen or lithium, may significantly advance our ability to treat CNS axonal injuries in adult mammals by promoting axonal regeneration and functional recovery. PUBLIC HEALTH RELEVANCE: We aim to develop novel therapies for CNS axonal injuries based on strong inhibitory properties of chondroitin sulfate proteoglycans, a group of extracellular matrix molecules generated by reactive glial scars. Development of novel peptide antagonists for these axonal growth inhibitors may advance our ability to treat CNS axonal injuries in the adult mammals. We hope that the translation of our novel therapeutic strategies from neuronal cultures in vitro to mouse model in vivo will ultimately lead to key strategies in patients with spinal cord injury and other CNS lesions.