Targeted Therapies for Neonatal White Matter Injury

项目总结摘要 新生儿脑白质损伤(NWMI)是导致儿童神经系统和发育障碍的主要原因 早产的孩子。最初的缺血/缺氧后的神经炎症，缺血性或感染性 INSULT由激活的小胶质细胞和星形胶质细胞介导，参与了导致弥漫性疾病的发病机制 脑白质损伤。靶向给药减轻神经炎症可能会大大提高治疗效果 结果。然而，治疗新生儿弥漫性脑损伤的药物输送是一个主要的 挑战。我们的初步研究表明，静脉注射树状大分子(树状) 纳米结构聚合物，4 nm)导致它们选择性地聚集在激活的小胶质细胞/巨噬细胞和 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毫克/公斤的N-乙酰半胱氨酸 与树枝状大分子(D-NAC)偶联的NAC在新生儿缺血后应用，导致显著的 短期内髓鞘形成改善，神经炎症减轻。首先，我们寻求 以有针对性的方式减轻NWMI的神经炎症。然而，靶向药物输送用于治疗 弥漫性脑损伤是一个重大挑战。我们之前已经证明，树枝状大分子的系统性给药 (树状纳米结构聚合物，4 nm)导致它们选择性地聚集在激活的小胶质细胞和 在我们的缺血NWMI小鼠模型中，星形胶质细胞和少突胶质细胞表达。此外，树枝状大分子共轭 至N-乙酰半胱氨酸(D-NAC)，在新生儿缺血后24小时和5天全身应用，导致 出生后第14天，炎性细胞因子的持续减弱和脑白质损伤的减少。 其次，我们寻求使用靶向D-NAC纳米疗法来提高胶质细胞限制性前体(GRP)的存活率。 GRP细胞移植目前正作为一种治疗策略在许多神经病学中被研究。 疾病，我们以前已经表明，移植的GRP在相同的 NWMI缺血型小鼠模型，但注射后存活和分化能力有限 脑部受伤。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 D-NAC释放药物以延长疗效，(Ii)确定D-NAC的治疗窗口 产后治疗和(3)确定D-NAC是否可以提高存活率和恢复能力 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在激活的小胶质细胞/巨噬细胞和星形胶质细胞中的选择性积聚 NWMI的新生儿缺血后；(2)靶向细胞递送和NAC的持续释放 树枝状大分子纳米器件将导致(A)减少神经炎症/氧化应激，以及(B)改善 NWMI患者的长期神经行为和神经病理结果；(3)D-NAC治疗将减少炎症反应 和氧化应激，并允许GRP存活、迁移和恢复髓鞘形成的宽松环境 NWMI组轴突损伤。这些假设将使用三个特定的目标进行测试，这些目标与 树枝状大分子-NAC纳米器件的制备，确定出生后的治疗窗口，以及 评估树枝状大分子的持续疗效。这项研究意义重大，因为它探索了 在临床相关的NWMI模型中进行有针对性的产后治疗以改善神经预后， 这将有助于我们更好地理解如何调节小胶质细胞激活和 慢性神经炎影响新生儿脑损伤和前体细胞重新髓鞘形成的能力 脑部受伤。

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.