Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA, 19129, USA.
Department of Physiology and Biophysics, Albert Einstein College of Medicine, Bronx, NY, 10461, USA.
Sci Rep. 2017 Aug 29;7(1):9675. doi: 10.1038/s41598-017-10250-z.
Microtubule-stabilizing drugs have gained popularity for treating injured adult axons, the rationale being that increased stabilization of microtubules will prevent the axon from retracting and fortify it to grow through inhibitory molecules associated with nerve injury. We have posited that a better approach would be not to stabilize the microtubules, but to increase labile microtubule mass to levels more conducive to axonal growth. Recent work on fetal neurons suggests this can be accomplished using RNA interference to reduce the levels of fidgetin, a microtubule-severing protein. Methods to introduce RNA interference into adult neurons, in vitro or in vivo, have been problematic and not translatable to human patients. Here we show that a novel nanoparticle approach, previously shown to deliver siRNA into tissues and organs, enables siRNA to gain entry into adult rat dorsal root ganglion neurons in culture. Knockdown of fidgetin is partial with this approach, but sufficient to increase the labile microtubule mass of the axon, thereby increasing axonal growth. The increase in axonal growth occurs on both a favorable substrate and a growth-inhibitory molecule associated with scar formation in injured spinal cord. The nanoparticles are readily translatable to in vivo studies on animals and ultimately to clinical applications.
微管稳定药物在治疗受伤的成年轴突方面越来越受欢迎，其基本原理是增加微管的稳定性将防止轴突回缩，并通过与神经损伤相关的抑制分子来增强其生长。我们假设，一个更好的方法不是稳定微管，而是增加不稳定的微管质量，使其更有利于轴突生长。最近对胎儿神经元的研究表明，这可以通过 RNA 干扰来实现，以降低微管切割蛋白 fidgetin 的水平。将 RNA 干扰引入成年神经元的方法，无论是在体外还是体内，都存在问题，并且不能转化为人类患者。在这里，我们表明，一种新的纳米颗粒方法，以前被证明可以将 siRNA 递送到组织和器官中，能够使 siRNA 进入培养的成年大鼠背根神经节神经元。这种方法对 fidgetin 的敲低是部分的，但足以增加轴突中不稳定的微管质量，从而增加轴突生长。这种轴突生长的增加发生在有利于生长的基质上，以及与受伤脊髓中瘢痕形成相关的生长抑制分子上。这些纳米颗粒很容易转化为动物体内研究，并最终应用于临床。
