Micro engineered 3D constructs for CNS repair

脊髓损伤通常会导致身体部分瘫痪（即已故演员克里斯·里维斯的“超人”）-在大多数情况下，这可能会影响四肢，而在其他情况下，只是膀胱，腿部和身体的下部等。这是由于神经纤维的直接或间接损伤（称为轴突）从大脑沿着脊髓运行，以及那些携带感觉信息从外周返回大脑。受伤后，受损区域将充满无功能的疤痕组织。不幸的是，受伤后几乎没有恢复，甚至在许多年后也没有恢复功能。损伤后脊髓修复的生物学方面是一个复杂的问题，尚未完全了解，正在积极研究。主要的神经外科医生同意，未来的治疗设想的脊髓损伤的修复将是一个细胞移植与药物干预相结合。移植的热门候选者是支持细胞或神经胶质（星形胶质细胞，嗅鞘细胞），它们通常包裹并引导再生的神经过程。希望这些细胞将有助于轴突再生穿过移植物通过瘢痕部位进入正常的CNS组织。由于疤痕环境是抑制轴突生长，由于存在许多抑制分子（分子参与这甚至被称为nogo！）药物干预对于克服抑制信号或去除抑制分子是必要的。我们最近关于使用嗅觉神经胶质细胞的细胞移植的数据表明，它们可以支持许多轴突的向内生长，尽管很少（如果有的话）出现离开移植物。移植物的解剖学检查给人的印象是轴突被嗅觉神经胶质包裹，但这些轴突在移植物内没有排列或顺序。很明显，CNS修复是一个复杂的过程，单一的治疗如胶质细胞移植不足以恢复脊髓功能。在这项资助中，我们打算开发一种基于支架的轴突生长指导系统。设想的支架将是一种聚合物，内部有微小的（约。1/2头发直径宽）引导管填充移植的神经胶质。在这些管道的内部，我们放置了更小的局部引导结构。这个支架将引导轴突，同时保护它们免受再生限制疤痕环境的影响。为计算机工业开发的制造原理使我们能够设计具有非常精细细节的硬材料（硅）的平板。为了创造三维支架，我们正在创造这些结构的聚合物复制品，然后使用类似于滚筒的小装置将结构化片材卷起。因此，我们能够以非常高的精度和可重复性制造这样的支架。通过使用可生物降解的聚合物作为支架，该装置可以留在体内慢慢溶解并被身体自身的材料所取代，同时指导神经延伸。由于神经辅助细胞和延伸的轴突如何在这样的人工环境中相互作用事先并不明显，我们将在分子细节上研究细胞反应，并使用获得的信息在不断的对话中告知构建体设计。预期对细胞存活和定向具有显著影响的结构特征的一个示例是允许营养物进入管所需的穿孔的尺寸、数量和分布。我们还将研究哪种细胞移植物最适合与我们的微结构植入物结合使用。我们希望最终能有一个设备，并选择一种细胞类型，一起可以进入脊髓损伤的体内测试。

Spinal cord injury often leads to a paralysis of parts of the body (i.e. the late actor Chris Reeves 'Superman') - which can be in most severe cases affect all four limbs, and in others just the bladder, the legs and lower parts of the body etc. This is due to the direct or indirect damage to the nerve fibres (known as axons) running from the brain along the spinal cord, and those carrying sensory information from the periphery back to the brain. After the injury the area damaged will fill with non-functional scar tissue. Unfortunately there is very little recovery after injury and no restoration of function - even over many years. The biological aspects of spinal cord repair after injury is a complex problem that is not completely understood and is actively being investigated. Leading neurosurgeons agree that future treatment envisaged for the repair of spinal cord injury will be a combination of a cellular transplant with pharmacological intervention. Popular candidates for transplantation are support cells or glia (astroglia, olfactory ensheathing cells) that normally envelope and guide regenerating nerve processes. It is hoped that these cells will aid axonal regeneration across the graft through the site of the scar into normal CNS tissue. As the scar environment is inhibitory to axonal outgrowth due to the presence of many inhibitory molecules (a molecule involved in this is even called nogo!) intervention with drugs is necessary to either overcome inhibitory signals or to remove the inhibitory molecules Our recent data on cellular transplantation using olfactory glia has shown that they can support the ingrowth of many axons, although very few if any appear to exit the graft. Anatomical examination of the grafts gives an impression that the axons are wrapped by olfactory glia but there is no alignment of these axons or order within the graft. It is clear that CNS repair is a complex process and a single treatment like glial cell transplantation is not sufficient for restoring spinal cord function. Within this grant we intend to develop a scaffold based guidance system for axonal outgrowth. The envisaged scaffold will be a polymer with internal tiny (ca. 1/2 hair diameter wide) guidance tubes filled with transplanted glia. On the inside of these tubes we place even smaller local guidance structures. This scaffold will guide the axons and at the same time protect them from the regeneration limiting scar environment. The principles of fabrication developed for the computer industry allow us to design flat sheet of hard material (silicon) with very fine detail. In order to create 3-dimensional scaffolds we are creating polymer replicates of these structures and then roll the structured sheet up using a small device akin to a cigarette-roller. We are therefore able to make such scaffolds with very high accuracy and repeatability. By using biodegradable polymers for the scaffold the device can be left within the body slowly dissolving and being replaced with the bodies own material, all the while instructing the nerve extensions. As it is not beforehand obvious how the nerve helper cells and the extending axons interact within such an artificial environment we will investigate the cellular response in molecular detail and use the information gained to inform the construct design in a constant dialog. One example of the structural features modified, which are expected to have a significant effect on cellular survival and orientation, is the size number and distribution of perforations / which are needed to allow nutrients to enter the tube. We will also investigate which cellular transplant is best used in combination with our microstructured implant. We hope to have at the end a device and selected a cell type that together could enter in vivo testing of spinal cord injury.