Dendrimer nanoparticles for assessment of microglial activation and therapeutic response to neonatal brain injury

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Project Summary Perinatal asphyxia (PA) is the leading cause of morbidity and mortality around the time of birth. In patients born with PA, many develop moderate or severe hypoxic-ischemic encephalopathy (HIE) and 20 to 30% will develop long term effects including cerebral palsy, epilepsy, mental retardation, or learning disability. PA is difficult to prevent or predict, and the current treatment strategy of therapeutic hypothermia only offers a 15% absolute reduction in the risk of death and disability. Thus, strategies to identify a therapeutic window or improve therapeutic efficacy have significant clinical potential. Inflammation is implicated in the development of HIE and is a useful therapeutic target since it broadly describes multiple pathways which perpetuate and increase the severity of injury. In neuroinflammation, microglia, the resident immune cells of the brain, adopt an activated phenotype with increased phagocytic behavior. Previous studies have leveraged this effect to demonstrate increased small molecule, specifically dendrimer nanoparticle, uptake within microglia in injured tissue. Accumulation of drug-loaded dendrimers in microglia, mediators of HIE injury, allows for targeted delivery of a therapeutic payload. Curcumin, our proposed therapeutic, has been shown by our lab to have significant neuroprotective effect in a rat model of neonatal HIE due to its anti-inflammatory and antioxidant properties. We will formulate two dendrimer conjugates, a fluorescent Cy5-dendrimer particle and a drug loaded Cy5-dendrimer- curcumin particle, using established chemistries. We will use Cy5-dendrimers to evaluate the timeline of microglia activation in response to injury in the neonatal rat model, finding time points of peak microglial activation by immunohistochemistry (semi-quantification based on phenotype and dendrimer-Cy5 co-localization) and fluorescent activated cell sorting (quantification based on antibody expression and Cy5 fluorescence). Using these same techniques, we will then evaluate microglial response to therapeutic dendrimer administration after systemic injection of the curcumin-loaded conjugate. This project will provide key answers including (1) the ideal time to provide therapeutic intervention after ischemic injury for suppression of inflammation, and (2) the ability of anti-inflammatory therapeutics to reverse injury on a cellular level. The overall goal of this project is to demonstrate the therapeutic potential of engineered dendrimer nanoparticles in neonatal HIE during a determined optimal therapeutic window. Identifying the injury timeline and a nanoparticle platform to leverage the disease pathophysiology will lead to improved therapeutic intervention in neonatal brain injury, with implications that can be translated to adult neurological disorders, where inflammation also plays a critical role.