Targeted Therapies for Neonatal White Matter Injury

项目摘要 新生儿白色物质损伤（NHTN）是导致神经和发育障碍的主要原因， 早产儿。神经炎症，初始缺血/缺氧缺血或感染性 由活化的小胶质细胞和星形胶质细胞介导的损伤与导致弥漫性脑损伤的发病机制有关。 白色物质损伤。靶向药物递送以减轻神经炎症可以极大地改善治疗效果。 结果。然而，用于治疗新生儿弥漫性脑损伤的药物递送是新生儿脑损伤治疗的主要障碍。 挑战.我们的初步研究表明，静脉注射树枝状聚合物（树状）， 纳米结构聚合物，4 nm）导致它们在活化的小胶质细胞/巨噬细胞中选择性积累， 受伤动物大脑中的星形胶质细胞。重要的是，单次静脉注射10 mg/kg剂量的N-乙酰半胱氨酸 (NAC)与树枝状聚合物（D-NAC）结合，在新生儿缺血后给药， 在短期内髓鞘形成的改善和神经炎症的减弱。首先，我们力求 以靶向方式减轻Nerve中的神经炎症。然而，用于治疗的靶向药物递送 弥漫性脑损伤是一个重大挑战。我们以前已经表明，全身施用树枝状聚合物， （树状纳米结构聚合物，4 nm）导致它们在活化的小胶质细胞中选择性积累， 星形胶质细胞和少突胶质细胞在我们的缺血性Numbers小鼠模型。此外，树枝状聚合物缀合 在新生儿缺血后24小时和5天全身给予N-乙酰半胱氨酸（D-NAC），导致 出生后第14天炎性细胞因子的持续衰减和白色物质损伤的减少。 其次，我们寻求使用靶向D-NAC纳米疗法来改善胶质限制性前体（GRP）存活。 GRP细胞移植目前正在研究作为一种治疗策略，在许多神经系统疾病， 我们以前已经证明，移植的GRP在相同的疾病中发挥了一些恢复作用， 缺血性小鼠模型，但当注射到 受伤的大脑在这些有希望的发现的基础上，本申请的目标是（i）提供持续的 通过D-NAC的药物释放以延长治疗效果，（ii）确定D-NAC的治疗窗口 治疗在产后期间和（iii）确定是否D-NAC可以提高生存和恢复 移植的GRP细胞的能力。我们的假设是：（1）持续的神经炎症将促进 D-NAC在活化的小胶质细胞/巨噬细胞和星形胶质细胞中的选择性积累，甚至在较晚的时间点 在新生儿缺血后，（2）NAC的靶向细胞递送和持续释放， 树枝状聚合物纳米器件将导致（a）神经炎症/氧化应激的减少，和（B）改善长期的 结论：（1）D-NAC治疗可减轻炎症反应， 和氧化应激，并允许GRP生存，迁移和恢复髓鞘形成的宽松环境 和轴突损伤。这些假设将使用三个具体目标进行测试， 树枝状聚合物-NAC纳米器件的制备，确定出生后时期的治疗窗口，以及 评估树枝状聚合物的持续功效。这项研究意义重大，因为它探索了 在临床相关的Numbers模型中进行有针对性的产后治疗，以改善神经系统结局， 这将有助于我们更好地了解如何调节小胶质细胞激活的作用， 慢性神经炎症影响新生儿脑损伤和前体细胞髓鞘再生能力， 受伤的大脑

PROJECT SUMMARY ABSTRACT Neonatal White Matter Injury (NWMI) is the leading cause of neurologic and developmental disabilities in children born prematurely. Neuroinflammation, following an initial ischemic/hypoxic-ischemic or infectious insult, mediated by activated microglia and astrocytes, is implicated in the pathogenesis resulting in diffuse white matter injury. Targeted drug delivery to attenuate neuroinflammation may greatly improve therapeutic outcomes. However, delivery of drugs for the treatment of diffuse brain injury in the neonate is a major challenge. Our preliminary studies suggest that intravenous administration of dendrimers (tree-like nanostructured polymers, 4 nm) results in their selective accumulation in activated microglia/macrophages and astrocytes in the brain of injured animals. Importantly, a single, intravenous 10 mg/kg dose of N-acetyl cysteine (NAC) conjugated to the dendrimer (D-NAC), administered after neonatal ischemia resulted in a significant improvement in myelination in the short-term, and attenutation of neuroinflammation. First, we seek to attenuate neuroinflammation in NWMI in a targeted manner. However, target drug delivery for the treatment of diffuse brain injury is a major challenge. We have previously shown that systemic administration of dendrimers (tree-like nanostructured polymers, 4nm) results in their selective accumulation in activated microglia and astrocytes, and in oligodendrocytes in our ischemic NWMI mouse model. Furthermore, dendrimer conjugated to N-acetylcysteine (D-NAC), systemically administered at 24h and 5 days post neonatal ischemia, resulted in sustained attenuation of inflammatory cytokines and reduction of white matter injury at postnatal day 14. Second, we seek to use targeted D-NAC nanotherapy to improve Glial restricted precursor (GRP) survival. GRP cell transplantation is currently being investigated as a therapeutic strategy in a number of neurologic diseases, and we have previously shown that transplanted GRPs exert some restorative effect in the same ischemic mouse model of NWMI, but have limited survival and differentiation capacity when injected into injured brain. Building on these promising findings, the objective of this application is to (i) provide sustained drug release by D-NAC to prolong therapeutic effect, (ii) determine the therapeutic window for D-NAC treatment in the postnatal period and (iii) determine whether D-NAC can enhance survival and restorative capacity of transplanted GRP cells. Our hypotheses are that (1) ongoing neuroinflammation will facilitate selective accumulation of D-NAC in activated microglia/macrophages and astrocytes even at later time points following neonatal ischemia in NWMI; (2) Targeted cellular delivery and sustained release of NAC by dendrimer nanodevices will result in (a) reduction of neuroinflammation/oxidative stress, and (b) improve long term neurobehavioral and neuropathological outcomes in NWMI; (3) D-NAC therapy will reduce inflammation and oxidative stress and allow a permissive environment for GRPs to survive, migrate and restore myelination and axonal injury in NWMI. These hypotheses will be tested using three specific aims, relating to the preparation of dendrimer-NAC nanodevice, identifying the therapeutic window in the post-natal period, and assessing the sustained efficacy of dendrimer. This study is significant because, it explores the potential of targeted post-natal therapy in a clinically relevant model of NWMI for improvement in neurological outcomes, and it will help us to develop a better understanding of how modulating the role of microglial activation and chronic neuroinflammation affects neonatal brain injury and the capacity of precursor cells to remyelinate an injured brain.