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，这是由于细胞死亡和有限的再生造成的。尽管脊髓神经元具有与生俱来的再生能力，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，通过桥接损伤部位来控制微环境。桥接微结构将指导轴突生长，局部给药将提供刺激再生的因素，但限制抑制轴突生长的因素。能够局部传递DMA的桥将局部地转染细胞，而蛋白质传递将使抑制物降解为再生。这种桥释放编码神经营养因子的DMA将被用来检验这样的假设，即转染组将启动轴突延伸到桥，穿过损伤部位，并促进重新进入宿主组织。这一假说基于以下观察结果：i)DMA传递可以在体内诱导持续的、局部的转基因表达，ii)将神经营养素传递到损伤部位可以促进轴突延长进入合成桥，iii)细胞移植或渗透泵植入并不提供可控的神经营养因子浓度来促进再生，iv)通过将桥内的促生长刺激减少到与宿主组织相当的水平并在桥相邻的瘢痕中降解抑制物来鼓励轴突重新进入宿主。基于这些观察，实验的重点是设计有效的基因转移桥梁，并将其应用于脊髓再生模型。具体目标1：通过多通道桥的持续释放，研究转基因在脊髓中的表达(数量、持续时间)和转基因(细胞数量、分布和身份)。特定目标2：使用体外模型研究轴突延长与转染组的关系。具体目的3：研究体内通过桥的轴突生长对转染率的依赖，以最大限度地增加通过桥的轴突数量。具体目标4：研究双重递送神经递质粒和软骨素酶，以使穿过桥的轴突，目标3的焦点，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.