Traumatic brain injury (TBI) affects millions of individuals annually resulting in disrupted neuronal circuitry and chronic neurological deficits. Subsequent neuroinflammation can exacerbate tissue damage and induce neurodegeneration that is many times worse than the original injury. Recent evidence suggests that monocyte- derived macrophages, the primary innate immune cells of the body, can exacerbate pathology or can induce tissue regeneration depending on the timing and extent of their infiltration, the behavioral phenotype they express, and the duration of time spent in the tissue. However, the role that macrophages play in driving secondary injury pathology and regeneration after TBI is largely contested because of incomplete or contradictory findings. Therefore, the purpose of this project is to characterize the contribution of these cells to TBI pathology and to simultaneously track monocyte infiltration in real time to generate a translational, minimally- invasive diagnostic strategy. Additionally, I propose to utilize a high-fidelity preclinical porcine model of closed- head diffuse TBI in order to characterize monocyte infiltration into the brain using magnetic resonance imaging to track magnetically-labeled cells and characterize macrophage behavior in the brain using imaging mass cytometry. Specifically, porcine monocytes, will be exogenously loaded with magnetic microparticles and these microparticle-loaded cells will be administered intravenously after TBI. Thereafter, magnetically labeled cells will be tracked in real time with magnetic resonance imaging (MRI) over time to characterize cell infiltration into the brain. I hypothesize that infiltrating macrophages will localize with micro-pathological features and that tracking macrophage infiltration with magnetic microparticles can be utilized as a novel diagnostic strategy. Importantly, this porcine model of TBI is the most clinically relevant model of TBI in use today, as this model closely replicates human head injury biomechanics.
In Aim 1, I will generate, validate, and implement a panel of porcine antibodies to characterize macrophage infiltration, distribution, and phenotype in archived porcine TBI tissue with imaging mass cytometry.
In Aim 2, I will synthesize, characterize, and administer magnetically labeled monocytes intravenously to swine in order to track cell infiltration into the brain in real time after TBI. Information gained from this proposal will develop a translationally relevant diagnostic strategy for TBI that could improve treatment and care in affected individuals and inform basic science questions about neuro-immune interactions. Importantly, this research can only be completed at the University of Pennsylvania and VA Medical Center because of unique resources and equipment that is not available anywhere else in the world. During this fellowship, I will have access to an imaging mass cytometer, an archive of over 120 porcine brains, an MRI, equipment for magnetic microparticle fabrication, and the injury device that induces the porcine closed-head diffuse TBI. Together, these resources, experiments, sponsor, collaborators, and institutional environment will cultivate a specialized research niche on neuro-immune interactions that will foster the growth of my developing research career.
After traumatic brain injury (TBI), monocyte-derived macrophages, the primary innate immune cells of the body, home to the brain, extravasate into the damaged tissue, differentiate into macrophages, and contribute to neuroinflammation. However, the extent of monocyte infiltration, the behaviors macrophages express after infiltrating, and their role in pathological debris removal and tissue regeneration is largely unknown. Here, we aim to develop new methodologies to characterize monocyte infiltration, macrophage distribution throughout the tissue, and cellular phenotype in order simultaneously answer basic neuroimmunology questions and develop a translational diagnostic strategy.
