中国神经再生研究(英文版) ›› 2016, Vol. 11 ›› Issue (2): 224-225.doi: 10.4103/1673-5374.177719

• 观点:脊髓损伤修复保护与再生 • 上一篇    下一篇

脊髓损伤后操控轴突再生的内外在障碍

  

  • 收稿日期:2015-12-14 出版日期:2016-02-15 发布日期:2016-02-15
  • 基金资助:

    这项工作是由美国国立卫生研究院R01 NS085426资助

Manipulating extrinsic and intrinsic obstacles to axonal regeneration after spinal cord injury

Eugene Mironets, Di Wu, Veronica J. Tom   

  1. Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania, PA, USA
  • Received:2015-12-14 Online:2016-02-15 Published:2016-02-15
  • Contact: Veronica J. Tom, Ph.D., veronica.tom@drexelmed.edu.
  • Supported by:

    This work was funded by NIH R01 NS085426 (VJT) and the Craig H. Neilsen Foundation (DW).

摘要:

脊髓损伤是一种可以导致永久性运动和感觉障碍的创伤性事件。初始创伤后,存活的神经元轴突会迅速缩回。虽然其可能有较小程度的不良萌芽,但几乎所有企图在整个病变部位增强的再生最终都会失败。因此,在损伤水平下的神经元会被永久的从它们的正常输入中断开,进而造成功能持续损失。最近,一些实验室已经开始阐明哪些因素可能介导内在的成熟中枢神经系统神经元增长不足。有趣的是,几个增强的发育调节转录因子,如Kruppel样家族因子和Sox11的若干成员,在成年神经元中可以改善它们的重新生长或发芽的能力。Zhigang He和他同事卓有成效的研究工作表明,肿瘤抑制因子PTEN(磷酸酶同源),会在成熟神经元内上调。PTEN可以抑制蛋白合成调节器mTOR(哺乳动物雷帕霉素靶标)的活化。而MTOR激活增加了与生长和存活相关的蛋白质合成。此外,PTEN基因缺失可以增强mTOR活性并导致损伤后轴突大幅生长。然而,虽然这种方法解决了上述损伤后生长的固有局限性,但内在的神经胶质瘢痕抑制屏障仍保持不变。最近,我们实验室推测同时解决内在神经元缺损和外在相关再生障碍瘢痕会引导脊髓损伤后显著的轴突再生。为了检验这一假设,我们采用了多管齐下的办法。将周围神经移植入胸椎水平完全脊髓损伤中,其会提供一种跨越空腔的促生长环境。他们使用编码绿色荧光蛋白(GFP;对照载体)注入腺相关病毒或者组合成型活性RHEB(caRheb;Ras同源富含脑)喙病灶转导并驱动mTOR激活是脊髓损伤后的神经元。最后使用了远侧接枝与ch'ase接口削弱并抑制细胞外基质中胶质瘢痕的影响。因为想要实现脊髓损伤后的功能性修复需要考虑很多方面多面,组合策略,即操控内在神经元生长潜力的同时减少轴突延长的外在抑制因素将可能是未来开发治疗脊髓损伤手段的重要发展方向。

Abstract:

Spinal cord injury (SCI) is a traumatic event that can lead to permanent motor and sensory deficits. After the initial trauma, axons of surviving neurons rapidly retract. While there may be a small degree of abortive sprouting, virtually all attempts at robust regrowth across the lesion site ultimately fail. Thus, neurons below the level of the injury are permanently disconnected from their normal input, resulting in persistent loss of function.  Recently, several labs have begun to elucidate what factors may mediate the intrinsic, growth deficiency in mature CNS neurons. Interestingly, increasing levels of several developmentally-regulated transcription factors, such as several members of the Krüppel-like factor (KLF) family and Sox11, in adult neurons improves their ability to re-grow or sprout. Elegant work by Zhigang He and colleagues showed that the tumor suppressor PTEN (phosphatase and tensin homolog), is upregulated in mature neurons. PTEN inhibits the activation of the protein synthesis regulator mTOR (mammalian target of rapamycin). MTOR activation increases the synthesis of proteins that are associated with growth and survival. Moreover, genetic deletion of PTEN increases mTOR activation and results in substantial axon growth after injury. However, while this approach addresses the intrinsic limitations to growth after injury, the inhibitory barriers within the glial scar remain intact. Recently, we hypothesized that simultaneously addressing intrinsic neuronal deficits in axon regrowth and extrinsic, scar-associated impediments to regeneration would result in significant regeneration after SCI. We grafted PN into the complete, thoracic level SCI to provide a growth-promoting environment to span the cavity. We injected adeno-associated virus (AAV) encoding for green fluorescent protein (GFP; control vector) or constitutively active Rheb (caRheb; Ras homolog enriched in brain) rostral to the lesion to transduce and drive mTOR activation in neurons above the SCI. Lastly, we treated the distal graft-host interface with ch’ase to diminish the effects of the inhibitory extracellular matrix in the glial scar. Because multiple facets will need to be considered to achieve functional repair of the SCI, combinatorial strategies focused on manipulate intrinsic neuronal growth potential while simultaneously reducing the extrinsic inhibitors of axon extension will likely be a staple for future therapies in SCI.