Modification and transplantation of anisotropic capillary gels for directed axonal regeneration in the injured spinal cord

创伤性脊髓损伤（SCI）后，组织完整性的显著丧失阻碍了轴突再生和目标神经再生。为了成功实现功能恢复，必须在新形成的病变腔及其周围疤痕组织中启动、引导和维持轴突生长，通过引入允许的物理基质来支持目标神经再支配和适当的突触形成。在我们的第一个资助周期中，我们能够将基于海藻酸盐的各向异性毛细血管水凝胶（ACH）与雪旺细胞（SC）播种/移植和病毒脑源性神经营养因子（BDNF）的使用独特地结合起来，成功地在ACH中产生长距离轴突生长并重新进入宿主脊髓。在这一资助期内，我们将研究一种改良的——与第一个资助期内提出的病变相比——低胸段完全脊髓横断，这些结构变化在运动和膀胱功能以及导致神经性疼痛的适应性不良可塑性方面的功能相关性。为了克服再生程度上的一些可能的限制，新生星形胶质细胞已经开始被探索作为sc的替代细胞类型。之前我们关注的是提高ACH整合和神经元再生能力的生物因素，现在我们将调节ACH固有的机械特性，即它的粘弹性，以增强更强大的轴突再生。我们的目标是发展稳定的ACH，具有接近脊髓的不同粘弹性。我们将在离体脊髓切片培养模型中确定1)诱导轴突生长电位的最佳乙酰胆碱。2)在脊髓损伤的活体研究中，我们将探索这些新的乙酰胆碱候选药物的潜力，以限制宿主的反应，如炎症、疤痕和囊肿的形成，并增强组织和机械的连续性，最终进一步增强轴突再进入宿主脊髓、长距离生长和功能恢复，作为促进远离神经元靶区损伤部位恢复的结构前提。

Following a traumatic spinal cord injury (SCI), dramatic loss of tissue integrity prohibits axonal regeneration and target reinnervation. For successful functional recovery to occur, axonal growth must be initiated, guided and sustained across a newly formed lesion cavity and its surrounding scar tissue by introducing a permissive physical substrate to support target reinnervation with proper synapse formation. In our first funding cycle we were able to uniquely combine the use of alginate-based anisotropic capillary hydrogels (ACH) with Schwann cell (SC) seeding/transplantation and viral brain-derived neurotrophic factor (BDNF) delivery to successfully generate long-distance axonal growth into the ACH and re-entry into the host spinal cord. In this funding period we will examine in a modified – compared to the lesion proposed in the first funding period - low thoracic complete spinal cord transection the functional relevance of these structural changes in respect to locomotor and bladder function as well as maladaptive plasticity leading to neuropathic pain. To overcome some possible limitations in the extent of regrowth, neonatal astrocytes have begun to be explored as an alternative cell type to SC.Having previously focused on biological factors to improve ACH integration and the neuronal regenerative capacity, we will now modulate the inherent mechanical characteristics of the ACH - namely its viscoelasticity to augment more robust axon regrowth. We aim to develop stable ACH with differing viscoelasticities approaching that of the spinal cord. We will determine 1) the optimal ACH for inducing axonal growth potential in an ex vivo spinal slice culture model. 2) Moving in vivo to a spinal cord lesion, we will explore the potential of these new ACH candidates to limit the host’s response such as inflammation, scar and cyst formation as well as enhance tissue and mechanical continuity, ultimately further enhancing axonal re-entry into the host spinal cord, long distance outgrowth and functional recovery as a structural prerequisite to promote recovery in injury sites remote from neuronal target regions.