Controlled Release Scaffolds for Nerve Regeneration

描述(申请人提供)：脊髓损伤会导致损伤水平以下的瘫痪，目前还没有能够恢复功能的治疗方法。有限的再生是局部环境的结果，局部环境缺乏刺激因子，而抑制因子过多。我们的长期目标是开发多功能生物材料，连接损伤部位，控制微环境，促进和引导轴突生长进入和穿过，并重新进入宿主组织，与完整的电路形成功能连接。在最初的资助阶段，我们已经开发了多个通道桥，这些桥机械地稳定了损伤部位，限制了二次损伤，并促进了进入和穿过损伤的轴突生长，轴突重新进入宿主组织。此外，我们拥有无与伦比的定位基因治疗载体的能力，通过表达神经营养因子显著增加再生轴突的数量。在建立了一个通过损伤支持轴突生长并进入宿主组织的系统后，我们现在专注于形成这些再生轴突与完整的脊髓回路的功能性连接。因此，这个方案的目标是：i)再生轴突的髓鞘形成，提供神经冲动的适当传导速度；ii)增强轴突重新进入宿主组织；以及iii)将重新进入轴突的轴突延伸到健康组织，以连接完整的电路。迈向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导致继发性组织损伤的事件，包括神经和胶质细胞死亡，以及产生硫酸软骨素蛋白多糖(CS)，这是胶质瘢痕的主要成分。炎症将是桥结构(目标1a)的目标，因为桥的通道和毛孔之间的细胞渗透不同。此外，我们的基因传递转导巨噬细胞，我们将研究促进更具再生性的表型(M2)而不是更具炎症性的表型(M1)的策略(目标1b)。减轻炎症有望增加神经元和神经胶质细胞的存活率，这应该会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来靶向胶质瘢痕(Aim 2)的抑制成分，该成分沉积在桥和宿主组织之间的界面上。阻止这些抑制成分的沉积有望增加重新进入宿主组织的轴突的数量。最后，基于纳米颗粒的基因传递将被用于在桥的尾部产生梯度，并促进重新进入宿主组织的轴突的延伸，这可以使与完整的电路连接(目标3)。这些可控系统可以识别形成功能连接所需的设计。此外，这些系统具有定义良好的组件，已在临床上使用，这可能有助于最终转换到临床。 公共卫生相关性：脊髓损伤会导致损伤水平以下的瘫痪，目前的治疗策略在恢复功能方面无效。脊髓具有再生的内在潜力，但不是由于生长促进因子供应不足和抑制因子过剩所致。我们正在开发能够传递基因的生物材料，作为控制脊髓环境的一种手段。这项建议侧重于使用这些工具来减少损伤中抑制因子的存在，并提供一种生长因子的梯度，以引导轴突离开生物材料，重新进入宿主组织并形成功能连接。像这样的可控系统将识别每个组件对功能结果的贡献，并可以进行调整以获得转换到临床所需的功能。

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.