Controlled Release Scaffolds for Nerve Regeneration

描述（由申请人提供）：脊髓损伤导致损伤水平以下的瘫痪，目前没有能够恢复功能的治疗方法。局部环境缺乏刺激因子，抑制因子过多，导致再生受限。我们的长期目标是开发多功能生物材料，桥接损伤部位，控制微环境，促进和指导轴突生长进入和穿过，并重新进入宿主组织，形成完整电路的功能连接。在最初的资助阶段，我们已经开发了多通道桥，可以机械地稳定损伤部位，限制继发性损伤，并促进轴突在损伤部位的生长，并使轴突重新进入宿主组织。此外，我们拥有无与伦比的基因治疗载体的局部递送能力，神经营养因子的表达显著提高了再生轴突的数量。在建立了一个支持轴突在损伤中生长并进入宿主组织的系统后，我们现在将重点放在形成这些再生轴突与脊髓完整回路之间的功能连接上。因此，本研究的目标是：1)使再生的轴突形成髓鞘，以提供适当的神经冲动传导速度；2)增强轴突重新进入宿主组织；3)将重新进入的轴突延伸到健康组织，以连接完整的神经回路。实现这些目标的第一步是调节炎症反应，炎症反应通常会引发一系列事件，导致继发性组织损伤，包括神经和胶质细胞死亡，以及硫酸软骨素蛋白聚糖（CS）的产生，CS是胶质瘢痕的主要成分。由于桥的通道和孔之间的细胞浸润不同，桥的结构将靶向炎症（Aim 1a）。此外，我们的基因传递换能器巨噬细胞，我们将研究促进更多再生表型（M2）而不是更多炎症表型（M1）的策略（Aim 1b）。减少炎症有望增加神经元和胶质细胞的存活，从而增加再生纤维的数量并增强髓鞘形成。随后，我们建议使用shRNA靶向胶质瘢痕的抑制成分（Aim 2），这些抑制成分沉积在桥和宿主组织之间的界面上。防止这些抑制成分沉积有望增加轴突重新进入宿主组织的数量。最后，基于纳米颗粒的基因传递将用于创建桥尾侧的梯度，并促进重新进入宿主组织的轴突的延伸，这可以实现完整电路的连接（目的3）。这些可控系统可以识别形成功能连接所需的设计。此外，这些系统具有已在临床中使用的定义良好的组件，这可能有助于最终转化为临床。

DESCRIPTION (provided by applicant): Injury to the spinal cord results in paralysis below the level of the injury, and there are no current therapies that are able to restore function. Limited regeneration occurs as result of the local environment, which is deficient in stimulatory factors and has an excess of inhibitory factors. Our long-term goal is to develop multi-functional biomaterials that bridge the injury site to control the microenvironment to promote and direct axonal growth into and through, and to re-enter the host tissue to form functional connections with intact circuitry. In the initial funding period, we have developed multiple channel bridges that mechanically stabilize the injury site that limits secondary damage, and promotes axonal growth into and across the injury, with axonal re-entry into the host tissue. Additionally, we have an unparalleled ability to localize delivery of gene therapy vectors, with which expression of neurotrophic factors significantly enhanced the number of regenerating axons. Having established a system that supports axonal growth through the injury and into the host tissue, we now focus on forming functional connections of these regenerating axons with intact circuitry of the spinal cord. Thus, the objectives of this proposal are to i) myelinate the regenerating axons provide the appropriate conduction speed of neural impulses, ii) enhance axonal re-entry into the host tissue, and iii) extension of the re-entering axons to healthy tissue for connection with intact circuitry. The initial step towards these objectives is to regulate the inflammatory response, which normally initiates a cascade of events leading to secondary tissue damage, including neural and glial death, and production of chondroitin sulfate proteoglycans (CS), a major component of the glial scar. Inflammation will be targeted by the bridge architecture (Aim 1a), as cell infiltration differs between the channels and pores of the bridge. Additionally, our gene delivery transducers macrophages, and we will investigate strategies to promote a more regenerative phenotype (M2) rather than a more inflammatory phenotype (M1) (Aim 1b). Reducing inflammation is expected to increase survival of neurons and glial, which should enhance the number of regenerating fibers and enhance myelination. Subsequently, we propose to employ shRNA to target the inhibitory components of the glial scar (Aim 2), which is deposited at the interface between the bridge and host tissue. Preventing deposition of these inhibitory components is anticipated to enhance the number of axons re-entering host tissue. Finally, nanoparticle based gene delivery will be employed to create gradients caudal to the bridge and promote extension of axons that have re-entered the host tissue, which can enable connections with intact circuitry (Aim 3). These controllable systems can identify the design necessary for the formation of functional connections. Additionally, these systems have well-defined components that have been used in the clinic, which may facilitate the ultimate translation to the clinic. PUBLIC HEALTH RELEVANCE: Injury to the spinal cord results in paralysis below the level of the injury, and current therapeutic strategies are ineffective at restoring function. The spinal cord has the intrinsic potential to regenerate, but does not due to the insufficient supply of growth promoting factors and an excess of inhibitory factors. We are developing biomaterials capable of gene delivery as a means to control the environment at the spinal cord. This proposal focuses on using these tools to reduce the presence of inhibitory factors within the injury, and to provide a gradient of growth factors that will direct axons to leave the biomaterials and re-enter the host tissue and form functional connections. Controllable systems such as this will identify the contribution of each component to functional outcome, and can be tuned to obtain the functionality necessary for translation to the clinic.