Injectable biomaterial depots to manipulate scar and foster axon growth after SCI

描述（由申请人提供）：改善脊髓损伤（SCI）后结局的一个重要策略是实现轴突再生穿过损伤到达功能性神经靶点。各种分子具有促进轴突再生的潜力，但不能通过血脑屏障并在许多中枢神经系统（CNS）区域中表现出活性，需要局部递送以实现功效同时避免副作用。长期但暂时的分娩是 needed.缺乏临床上可翻译的这种交付方法。我们的目标是开发功能化的二嵌段共聚肽水凝胶（DCH）作为完全合成的生物材料，其可以容易且安全地注射到SCI病变中和附近，以提供用于持续局部释放多个分子的仓库，所述多个分子操纵局部细胞并刺激轴突再生成健康组织。我们以前的工作证明了DCH的安全性和有效性，以提供生长因子，发挥可预测的影响，在几毫米的距离在中枢神经系统。新的初步数据表明：（1）SCI后2天注射的DCH贮库能够同时提供多种生长因子，刺激整个SCI病变核心的感觉和本体脊髓纤维的实质性再生。我们发现，这些再生轴突跟踪沿着细胞与新上调层粘连蛋白的表达，并再生可以被阻断的功能阻断抗体，破坏层粘连蛋白-整合素结合的同时交付。(2)当DCH递送多种生长因子与通过在转基因小鼠中缺失STAT 3来减弱胶质瘢痕结合时，轴突再生超出病变核心进入远端胶质瘢痕。新的数据还表明，DCH可以提供像JSI这样的疏水性小分子，它可以抑制STAT 3并以与我们的转基因小鼠相当的方式减弱疤痕形成。(3)当将多个DCH储库放置到病变核心和远端健康组织中时，我们发现相当多的轴突再生长到含有活的NeuN阳性神经元的健康组织区域中。这项工作将建立在这些初步发现的基础上，并使用SCI后注入的DCH库同时提供不同类型的分子（包括多种蛋白质生长因子、抗体和操纵基因表达的小疏水分子），以便：（i）操纵瘢痕和损伤核心中的细胞以使能和支持轴突再生长，（ii）直接刺激和引导轴突再生长，通过和超越损伤进入健康组织，（iii）剖析由不同分子或分子组合刺激的轴突再生的细胞和分子机制，以及（iv）测试到达健康组织的再生的固有脊髓神经元是否能够接触那里的神经元并且能够形成改善运动功能的中继连接。这种DCH储库方法将为SCI后细胞和分子机制的实验研究提供强有力的工具，并将促进为潜在的临床翻译鉴定合适分子所需的广泛试验和错误测试。此外，由于DCH是完全合成的生物材料， 也是DCH临床翻译用于SCI的现实潜力。

DESCRIPTION (provided by applicant): An important strategy for improving outcome after spinal cord injury (SCI) is to achieve axon regrowth across lesions to reach functional neural targets. Various molecules have the potential to foster axon regrowth but cannot pass the blood brain barrier and exhibit activity in many central nervous system (CNS) regions, necessitating local delivery to achieve efficacy while avoiding side effects. Prolonged but temporary delivery is needed. Clinically translatable methods for such delivery are lacking. Our goal is to develop functionalized diblock copolypeptide hydrogels (DCH) as fully synthetic biomaterials that that can easily and safely be injected into, and near, SCI lesions to provide depots for sustained local release of multiple molecules that manipulate local cells and stimulate axons to regrow into healthy tissue. Our previous works demonstrates DCH safety and efficacy to deliver growth factors that exert predictable effects over distances of several mm in CNS. New preliminary data show that: (1) DCH depots injected 2 days after SCI are able to simultaneously deliver multiple growth factors that stimulate substantive regrowth of both sensory and propriospinal fibers throughout the SCI lesion core. We find that these regrowing axons track along cells with newly upregulated laminin expression, and that regrowth can be blocked by simultaneous delivery of function-blocking antibodies that disrupt laminin-integrin binding. (2) When DCH delivery of multiple growth factors is combined with attenuation of glial scar by deletion of STAT3 in transgenic mice, axons regrow beyond the lesion core into the distal glial scar. New data also show DCH can deliver hydrophobic small molecules like JSI, which inhibits STAT3 and attenuates scar formation in a manner comparable to our transgenic mice. (3) When multiple DCH depots are placed into both the lesion core and distal healthy tissue, we find considerable axon regrowth into healthy tissue areas that contains viable NeuN-positive neurons. The work proposed will build on these preliminary findings and use DCH depots injected after SCI to simultaneously deliver different types of molecules (including multiple protein growth factors, antibodies and small hydrophobic molecules that manipulate gene expression) in order to: (i) manipulate cells in scar and lesion core to enable and support axon regrowth, (ii) directly stimulate and guide axon regrowth into, through and beyond lesions into healthy tissue, (iii) dissect cellular and molecular mechanisms that underlie the axon regrowth stimulated by different molecules or combinations of molecules, and (iv) test whether regrowing propriospinal neurons that reach healthy tissue are able to contact neurons there and are able to form relay connections that improve locomotor function. This DCH depot approach will provide a powerful tool for the experimental investigation of cellular and molecular mechanisms after SCI, and will facilitate the extensive trial and error testing needed to identify appropriate molecules for potential clinical translation. In addition, because DCH are fully synthetic biomaterials, there is also a realistic potential for clinical translation of DCH for use in SCI.