Inhibitory synapses and axon regeneration in adults after injury-induced axotomy

成人损伤诱导轴突切除术后的抑制性突触和轴突再生

• 批准号: 10020198
• 负责人: FRANCISCO J ALVAREZ
• 金额: $ 19.5万
• 依托单位: EMORY UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-09-30 至 2021-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10020198
• 关键词: Adult; Affect; Anatomy; Axon; Axotomy; Bed rest; Biology; Calcium; Cells; Cephalic; Chronic; Data; Denervation; Development; Down-Regulation; Epidemiology; Epileptogenesis; Estrogen receptor positive; Excitatory Synapse; Exercise; Experimental Designs; Face; Future; Genetic; Glutamates; Glycine; Grant; Growth; Immobilization; Impairment; Incidence; Inhibitory Synapse; Injury; Interneurons; Knowledge; Label; Limb structure; Mediating; Military Personnel; Motor; Motor Neurons; Muscle; Muscular Atrophy; Mutation; Natural regeneration; Nature; Nerve; Nerve Regeneration; Neurites; Neurons; Operative Surgical Procedures; Patients; Peripheral Nerves; Peripheral nerve injury; Pharmacology; Potassium Chloride; Protein Isoforms; Recovery; Recovery of Function; Rehabilitation therapy; Resolution; Sampling; Schwann Cells; Sensory; Speed; Spinal; Stretching; Supporting Cell; Synapses; Synaptic plasticity; Techniques; Testing; Time; Validation; afferent nerve; axon growth; axon regeneration; combat; cost; designer receptors exclusively activated by designer drugs; dorsal motor nucleus; driving force; exercise program; functional outcomes; gamma-Aminobutyric Acid; improved; interest; limb injury; male; mouse model; nerve injury; nerve supply; novel; novel strategies; preservation; prevent; professor; recruit; regenerative; reinnervation; repaired; symporter; synaptic function; tetanospasmin; transmission process; young adult

Motor and sensory nerves regenerate in the periphery after being axotomized following nerve injuries. This capacity allows some functional recovery, however this is frequently suboptimal being the relative inefficiency of axon regeneration a major problem, particularly for injuries at some distance from muscle. Axotomy induces genetic changes in motoneurons that promote axon growth, yet this is rather slow taking months or years for axons to reach their targets after limb injuries. This compounds with the fact that the regenerative capacity of motoneurons is limited to a short temporal window and that chronic denervation results in muscle atrophy, as well as changes in central circuits, all impairing recovery. Therefore there is renewed interest on mechanisms to promote axon regeneration. One mechanism recently highlighted and intensely studied by one of the P.I.s (Dr. A.W. English) is the effect of activity and exercise in promoting axon regeneration. However, this approach is limited since patients are frequently either with the affected limbs immobilized or in bed rest preventing implementation of adequate exercise programs. We now seek proof for a mechanistic explanation that could be recruited also with passive rehabilitation and/or pharmacology. After axotomy motoneurons increase their excitability and shed excitatory synapses while maintaining inhibitory synapses. In addition, the potassium chloride co-transporter isoform 2 (KCC2) is downregulated changing the nature of inhibitory synapses from hyperpolarizing to depolarizing. The other P.I. in this proposal (Dr. F.J. Alvarez) is an expert in spinal inhibitory interneurons and synapses. Together, both P.I.s hypothesized that after axotomy inhibitory synapses are the main drivers of motoneuron activity and could stimulate axon regeneration. There is a strong scientific premise for this hypothesis: GABA actions promote axon elongation during early development and manipulations that enhanced preservation of inhibitory synapses on axotomized motoneurons correlated with faster functional recovery. To directly test whether inhibitory synaptic activity on axotomized motoneurons promotes axon regeneration we propose in Aim 1 to block inhibitory synapses on axotomized motoneurons using tetanus neurotoxin A and study the effects on motor axon regeneration and muscle reinnervation. In Aim 2 we will use mouse models to genetically define the interneurons targeting the cell body of regenerating motoneurons and that could provide a depolarizing synaptic drive. We will then use genetically-encoded activity modifiers to examine whether their activity influences motor axon regeneration. Resolution of these aims will reveal for the first time whether inhibitory synapse activity is a driving force for axon regeneration in the adult and the spinal neurons that might be responsible. This is of high significance from a translational point of view since it will point to new approaches to enhance “inhibitory” drive by either pharmacological means or by recruiting key interneurons through various manipulations, like stretching or stimulating the antagonist muscles and nerves.

运动神经和感觉神经在神经损伤后被轴突切断后会在周围再生。 容量允许一定的功能恢复，但这通常不是最理想的，因为效率相对较低 轴突再生的一个主要问题，特别是对于距肌肉一定距离的损伤。 运动神经元的遗传变化促进轴突生长，但这相当缓慢，需要数月或数年的时间 肢体受伤后轴突到达目标的能力与再生能力有关。 运动神经元仅限于较短的时间窗口，慢性去神经支配会导致肌肉萎缩，如 以及中枢回路的变化，都会损害恢复，因此人们对机制重新产生了兴趣。 一位 P.I. 最近强调并深入研究了一种机制。 （A.W. English 博士）是活动和锻炼在促进轴突再生方面的效果，然而，这种方法。 由于患者要么经常固定受影响的肢体，要么卧床休息，因此受到限制 我们现在寻求机械解释的证据。 轴突切除术后运动神经元也可以通过被动康复和/或药物来招募。 兴奋性并释放兴奋性突触，同时保持抑制性突触。 氯离子协同转运蛋白亚型 2 (KCC2) 下调，改变了抑制性突触的性质 该提案中的另一位 P.I.（F.J. Alvarez 博士）是脊柱抑制方面的专家。 中间神经元和突触一起，在轴切术抑制性突触之后受到追捧。 运动神经元活动的主要驱动因素并可以刺激轴突再生有强有力的科学前提。 对于这个假设：GABA 作用在早期发育和操作过程中促进轴突伸长， 轴突运动神经元上抑制性突触的增强保存与更快的功能相关 直接测试轴突运动神经元的抑制性突触活动是否促进轴突。 我们在目标 1 中建议使用破伤风来阻断轴突运动神经元的抑制性突触再生 在目标 2 中，我们将使用神经毒素 A 并研究其对运动轴突再生和肌肉神经支配的影响。 小鼠模型从基因上定义靶向再生运动神经元细胞体的中间神经元 然后我们将使用基因编码的活动调节剂来提供去极化的突触驱动。 检查它们的活动是否影响运动轴突再生将揭示这些目标的解决。 首次研究抑制性突触活动是否是成人和脊髓轴突再生的驱动力 从翻译的角度来看，这具有重要意义，因为它会起作用。 指出通过药理学手段或招募关键药物来增强“抑制”驱动力的新方法 通过各种操作来控制中间神经元，例如拉伸或刺激拮抗肌肉和神经。