KSCHIRT: PACAP mRNA delivery to treat traumatic brain injury

Neuroinflammation mediated by proinflammatory immune cells drives the secondary injury pathology observed after a traumatic brain injury (TBI). Therapeutic strategies that shift the immune phenotype from inflammatory to reparative will have a profound impact on patient outcomes by minimizing tissue injury, promoting neuronal growth, and restoring brain function. Pituitary adenylate cyclase-activation polypeptide-38 (PACAP) is a naturally occurring neuropeptide with neurotrophic and neuroprotective potential. Thus, PACAP has been suggested as an ideal therapeutic to treat neurotrauma, but suffers from poor circulation half-life which limits its therapeutic potential in the brain. Therefore, our overall goal is to establish foundational knowledge aimed at implementing PACAP mRNA as an innovative therapeutic modality to for inflammation-specific expression in the brain. This strategy benefits from our innovative lipid nanoparticle platform to enhance delivery to inflammatory immune cells trafficking to injured tissues including the brain, and robust mRNA transgene expression from immune cells infiltrating the injured tissue. This proposed research builds upon our strong preliminary data in which we observe immune-cell specific accumulation of lipid nanoparticles in the brain after TBI, and robust in vivo mRNA expression in vitro and in vivo. Our rationale is based on the knowledge that phagocytic immune cells flood into circulation from the bone marrow and migrate toward sites of injury while accumulating nanoparticle by phagocytosis. Our hypothesis is that lipid nanoparticles taken up by immune cells trafficking to the brain will enhance localized PACAP expression in the brain and reduce secondary neuronal injury and improve outcomes after a TBI. Encouraged by our preliminary data, we propose the following Specific Aims to advance the fundamental understanding of PACAP mRNA as a therapeutic modality to treat neuroinflammation after a TBI: 1) Evaluate a novel class of triazine lipids for mRNA transfection and PACAP expression; 2) Elucidate the timing of delivery that promotes optimal accumulation of nanoparticles in immune cells trafficking to the brain in a controlled cortical impact model; and 3) Determine the behavioral implications of mRNA-based PACAP expression after a TBI. This approach is innovative due to: 1) our investigation of mRNA encoding PACAP to treat TBI; 2) our development of triazine based lipids as ideal nucleic acid carriers to improve mRNA transfection and protein expression; and 3) our approach to target immune cells migrating to the site of inflammation to improve inflammation-specific expression in vivo. The significance of this research is focused on advancing the field focused on PACAP biology in the context of TBI and the utility of nanoparticle compositions to treat neuroinflammation following TBI.