Reprogramming reactive glial cells into functional new neurons after SCI

项目总结 严重的发病率和死亡率通常与脊髓损伤(SCI)有关。人类患者 在脊髓损伤中幸存下来，经常瘫痪，生活质量和生产力极大下降。SCI往往会导致 神经元的永久性丧失和神经回路的中断对正常的运动、感觉、 和自主神经功能。补充丢失的神经元和重建破裂的神经回路对于治疗 功能恢复。与身体的其他组织或器官不同，如皮肤和肝脏，它们可以 通过内源性干细胞或体细胞的增殖进行自我修复，成人脊髓表现出极少的 再生能力。干细胞源性神经前体细胞或分化神经元的细胞移植 拥有12-18岁的临床潜力。然而，细胞治疗的效率相对较低，因为这些细胞未能 存活或完全采用一种功能表型，特别是在神经损伤的慢性阶段。与之形成鲜明对比的是 基于移植的治疗，我们建议使用一种新的策略来重新编程内源性反应性胶质细胞 为脊髓损伤后功能恢复向成熟神经元转化。胶质细胞数量丰富，分布广泛。 成人的脊髓。它们变得反应性、增殖，并在损伤后形成胶质疤痕，并发挥作用。 在调节组织损伤和损伤后修复中的关键作用。值得注意的是，疤痕的形成和分泌物 反应性胶质细胞(如星形胶质细胞)所产生的硫酸软骨素蛋白多糖(CSPG)对功能有抑制作用 进步。减轻反应性胶质增生或降低CSPG活性可促进创伤后再生， 而不断增加的反应性胶质细胞增多症会加重脑损伤。这里我们假设重新编程是反应性的 损伤部位的胶质细胞向神经元转化会减少局部胶质瘢痕的形成，并促进新的 神经回路导致功能恢复。使用颈椎C5背侧半横断模型(C5DH)和前肢 在成年小鼠的功能恢复评估中，我们将用三个特定的目标来检验这一假说。在目标1中，我们 将决定C5水解酶之后胶质细胞转化神经元的功能整合。在目标2中，我们将确定 C5DH后神经胶质细胞转化神经元与局部神经回路的解剖整合。最后，在目标3中，我们 将确定脊髓上和/或固有脊髓下行通路对诱导神经元的功能作用 在促进C5DH术后前肢功能恢复方面。拟议的战略预计将提供 可能促进脊髓损伤后功能恢复的替代神经元亚型。

PROJECT SUMMARY Severe morbidity and mortality are commonly associated with spinal cord injury (SCI). Human patients who survive SCI frequently live with paralysis and extremely reduced quality of life and productivity. SCI often results in a permanent loss of neurons and the disruption of neural circuits that are critical for normal motor, sensory, and autonomic function. It is crucial to replenish the lost neurons and reconstruct the broken neural circuits for functional recovery. Unlike some other tissues or organs in the body, such as skin and liver, which can undergo self-repair through proliferation of endogenous stem or somatic cells, adult spinal cord exhibits minimal regenerative capacity. Cellular transplantation of stem cell-derived neural progenitors or differentiated neurons holds clinical potential 12-18. However, cell therapy is relatively inefficient due to the failure of these cells to survive or fully adopt a functional phenotype especially under the chronic phase of neural injury. In contrast to transplantation-based therapy, we propose to employ a novel strategy to reprogram endogenous reactive glial cells to mature neurons for functional recovery after SCI. Glial cells are abundant and ubiquitously distributed in the adult spinal cord. They become reactive, proliferate, and form glial scars in response to damage, and play critical roles in modulating tissue damage and repair after injury. Of note, scar formation and secretion of chondroitin sulfate proteoglycans (CSPG) by reactive glial cells (e.g. astrocytes) are inhibitory for functional improvement. Attenuating reactive gliosis or reducing CSPG activity improves posttraumatic regeneration, whereas increasing reactive gliosis worsens brain injuries. Here we hypothesize that reprogramming reactive glial cells to neurons at the injury site will reduce local glial scar formation and enhance establishment of new neural circuit resulting in functional recovery. Using a cervical C5 dorsal hemisection model (C5 DH) and forelimb functional recovery assessments in adult mice, we will test this hypothesis with three specific aims. In Aim 1, we will determine functional integration of glia-converted neurons after the C5 DH. In Aim 2, we will determine the anatomical integration of glia-converted neurons into local neural circuitry after the C5 DH. Lastly, in Aim 3, we will determine functional roles of descending supraspinal and/or propriospinal pathways over induced neurons in promoting forelimb functional recovery after the C5 DH. The proposed strategy is expected to provide alternative neuronal subtypes that may facilitate functional recovery after SCI.