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，这是由细胞死亡和再生受限引起的。虽然脊髓神经元具有天生的再生能力，但它们受到促进再生的因子供应不足和抑制再生的因子供应充足的限制。我们的长期目标是开发一种基于生物材料的联合疗法，以桥接损伤部位，控制微环境。桥微结构将引导轴突生长，并且局部药物递送将提供刺激再生的因子，但限制抑制轴突生长的因子。能够局部DMA递送的桥将局部地抑制细胞，而蛋白质递送将降解抑制剂以再生。将采用释放编码神经营养因子的DMA的桥来测试转染概况将引发轴突伸长进入桥、穿过损伤部位并促进重新进入宿主组织的假设。该假设基于以下观察：i）DMA递送可诱导体内持续的、局部的转基因表达，ii）神经营养因子递送至损伤部位可促进轴突伸长成合成桥，iii）细胞移植或渗透泵植入不提供用于促进再生的神经营养因子的可控浓度，iv）通过将桥内的生长促进刺激物减少到与宿主组织相当的水平，并降解桥附近瘢痕中的抑制剂，来促进轴突重新进入宿主。基于这些观察，实验的重点是设计有效的基因转移的桥梁，并将其应用于脊髓再生模型。具体目标1：通过从多通道桥持续释放，研究脊髓中的转基因表达（数量、持续时间）和转染（细胞数量、分布和身份）。具体目标2：使用体外模型研究具有转染特征的轴突伸长。具体目标3：研究体内通过桥的轴突生长对转染曲线的依赖性，以最大限度地增加通过桥的轴突数量。具体目标4：研究neurorophin编码质粒和软骨素酶的双重递送，以使轴突能够穿过Aim 3的焦点桥，重新进入宿主组织。

DESCRIPTION (provided by applicant): Injury to the spinal cord results in paralysis below the level of the injury, which results from cell death and limited regeneration. Although spinal cord neurons have the innate capacity to regenerate, they are limited by an insufficient supply of factors to promote regeneration, and an abundant supply of factors that inhibit regeneration. Our long-term goal is to develop a combination therapy based on biomaterials that bridge the injury site to control the microenvironment. The bridge microstructure will direct axonal outgrowth and localized drug delivery will provide factors that stimulate regeneration yet limit the factors that inhibit axonal outgrowth. Bridges capable of localized DMA delivery will transfect cells locally, whereas protein delivery will degrade inhibitors to regeneration. This bridge releasing DMA encoding for neurotrophic factors will be employed to test the hypothesis that the transfection profile will initiate axonal elongation into the bridge, across the injury site, and facilitate re-entry into the host tissue. This hypothesis is based on the observations that i) DMA delivery can induce sustained, localized transgene expression in vivo, ii) neurotrophin delivery to the injury site can promote axonal elongation into a synthetic bridge, iii) cell transplantation or osmotic pump implantation does not provide a controllable concentration of neurotrophins for promoting regeneration, iv) axonal re-entry into the host is encouraged by reducing the growth promoting stimuli within the bridge to levels comparable to host tissue, and degrading inhibitors in the scar adjacent to the bridge. Based on these observations, the experimental focus is on designing bridges for efficient gene transfer and applying them in a spinal cord model of regeneration. Specific Aim 1: Investigate transgene expression (quantity, duration) and transfection (cell number, distribution, and identity) in the spinal cord by sustained release from the multiple channel bridge. Specific Aim 2: Investigate axonal elongation with the transfection profile using an in vitro model. Specific Aim 3: Investigate the dependence of axonal growth through the bridge in vivo on the transfection profile to maximize the number of axons crossing the bridge. Specific Aim 4: Investigate dual delivery of neurorophin-encoding plasmid and chondroitinase to enable axons crossing the bridge, the focus of Aim 3, to re-enter the host tissue.