title: Systemic dendrimer-drug treatment of ischemia-induced neonatal white matter injury.
abstract: Extreme prematurity is a major risk factor for perinatal and neonatal brain injury, and can lead to white matter injury that is a precursor for a number of neurological diseases, including cerebral palsy (CP) and autism. Neuroinflammation, mediated by activated microglia and astrocytes, is implicated in the pathogenesis of neonatal brain injury. Therefore, targeted drug delivery to attenuate neuroinflammation may greatly improve therapeutic outcomes in models of perinatal white matter injury. In this work, we use a mouse model of ischemia-induced neonatal white matter injury to study the biodistribution of generation 4, hydroxyl-functionalized polyamidoamine dendrimers. Following systemic administration of the Cy5-labeled dendrimer (D-Cy5), we demonstrate dendrimer uptake in cells involved in ischemic injury, and in ongoing inflammation, leading to secondary injury. The sub-acute response to injury is driven by astrocytes. Within five days of injury, microglial proliferation and migration occurs, along with limited differentiation of oligodendrocytes and oligodendrocyte death. From one day to five days after injury, a shift in dendrimer co-localization occurred. Initially, dendrimer predominantly co-localized with astrocytes, with a subsequent shift towards microglia. Co-localization with oligodendrocytes reduced over the same time period, demonstrating a region-specific uptake based on the progression of the injury. We further show that systemic administration of a single dose of dendrimer-N-acetyl cysteine conjugate (D-NAC) at either sub-acute or delayed time points after injury results in sustained attenuation of the 'detrimental' pro-inflammatory response up to 9days after injury, while not impacting the 'favorable' anti-inflammatory response. The D-NAC therapy also led to improvement in myelination, suggesting reduced white matter injury. Demonstration of treatment efficacy at later time points in the postnatal period provides a greater understanding of how microglial activation and chronic inflammation can be targeted to treat neonatal brain injury. Importantly, it may also provide a longer therapeutic window.
authors.affiliation: Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, United States; Center for Nanomedicine, Johns Hopkins University School of Medicine, Baltimore, MD21205, United States.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Nance
authors.affiliation: Kennedy Krieger Institute, Johns Hopkins University, Baltimore, MD 21205, United States.
authors.forename: Michael
authors.initials: M
authors.lastname: Porambo
authors.affiliation: Center for Nanomedicine, Johns Hopkins University School of Medicine, Baltimore, MD21205, United States; Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, MD 21218, United States.
authors.forename: Fan
authors.initials: F
authors.lastname: Zhang
authors.affiliation: Center for Nanomedicine, Johns Hopkins University School of Medicine, Baltimore, MD21205, United States; Ophthalmology, Wilmer Eye Institute at Johns Hopkins School of Medicine, 21205, United States.
authors.forename: Manoj K
authors.initials: MK
authors.lastname: Mishra
authors.affiliation: Kennedy Krieger Institute, Johns Hopkins University, Baltimore, MD 21205, United States.
authors.forename: Markus
authors.initials: M
authors.lastname: Buelow
authors.affiliation: Kennedy Krieger Institute, Johns Hopkins University, Baltimore, MD 21205, United States.
authors.forename: Rachel
authors.initials: R
authors.lastname: Getzenberg
authors.affiliation: Kennedy Krieger Institute, Johns Hopkins University, Baltimore, MD 21205, United States; Department of Neurology, Johns Hopkins School of Medicine, Baltimore, MD 21205, United States.
authors.forename: Michael
authors.initials: M
authors.lastname: Johnston
authors.affiliation: Center for Nanomedicine, Johns Hopkins University School of Medicine, Baltimore, MD21205, United States; Kennedy Krieger Institute, Johns Hopkins University, Baltimore, MD 21205, United States; Ophthalmology, Wilmer Eye Institute at Johns Hopkins School of Medicine, 21205, United States.
authors.forename: Rangaramanujam M
authors.initials: RM
authors.lastname: Kannan
authors.affiliation: Kennedy Krieger Institute, Johns Hopkins University, Baltimore, MD 21205, United States; Department of Neurology, Johns Hopkins School of Medicine, Baltimore, MD 21205, United States.
authors.forename: Ali
authors.initials: A
authors.lastname: Fatemi
authors.affiliation: Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, United States; Center for Nanomedicine, Johns Hopkins University School of Medicine, Baltimore, MD21205, United States; Kennedy Krieger Institute, Johns Hopkins University, Baltimore, MD 21205, United States. Electronic address: skannan3@jhmi.edu.
authors.forename: Sujatha
authors.initials: S
authors.lastname: Kannan
mesh_terms: D000111:Acetylcysteine / Q000008:administration & dosage / Q000627:therapeutic use; D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000473:pathology; D001921:Brain / Q000378:metabolism; D002545:Brain Ischemia / Q000188:drug therapy* / Q000473:pathology; D002465:Cell Movement / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D016207:Cytokines / Q000037:antagonists & inhibitors; D050091:Dendrimers / Q000737:chemistry* / Q000493:pharmacokinetics; D003720:Densitometry; D016503:Drug Delivery Systems; D005260:Female; D051379:Mice; D017628:Microglia / Q000187:drug effects; D009186:Myelin Sheath / Q000378:metabolism; D009836:Oligodendroglia / Q000187:drug effects; D011247:Pregnancy; D012313:RNA / Q000096:biosynthesis / Q000235:genetics; D066127:White Matter / Q000473:pathology*
chemical_list: D016207:Cytokines; D050091:Dendrimers; D012313:RNA; D000111:Acetylcysteine
keywords: Dendrimer; Ischemia; Microglia; Neonatal; Neuroinflammation; Targeted delivery