KSCHIRT: A miRNA-Based Liposome Nanoparticle Intervention to Treat Secondary Injury Following Traumatic Brain Injury in Mice

Abstract: Traumatic brain injury (TBI) elicits complex underlying neurochemical mechanisms. Up to date, no effective treatment exists partly because of the incomplete understanding of the numerous secondary biochemical and pathophysiological events occurring following the initial injury. Some of these secondary events, such as persistent neuroinflammation and disruption of autophagy homeostasis are highly destructive and poorly understood. Compelling evidence supports targeting these secondary events as a promising strategy for promoting cellular repair and functional recovery. MicroRNAs (miRNA) are small, non-coding RNAs that regulate gene expression in all known animal species. Numerous miRNAs are differentially expressed after brain injury and several of them exhibit sexually dimorphic activities. One of these miRNAs is an X-chromosome encoded miRNA, miR-223, which is a macrophage-enriched miRNA, and has been documented to regulate inflammatory responses in various disease conditions. However, the molecular mechanisms by which miR-223 drives the pathological or reparative secondary events, and the potential for using miRNAs for TBI therapeutic strategies, are not known and these represent critical knowledge gaps. We have generated exciting preliminary data that may help identify novel translational strategies to promote cellular repair and neurological recovery by tuning neuroinflammation and autophagy in the injured brain. We propose to test the central hypothesis that miR-223 strongly promotes a CNS reparative outcome following TBI by controlling chronic neuroinflammatory signaling and maintaining a homeostatic autophagy phenotype, and is a therapeutically targetable molecular regulator of secondary events in TBI. Testing this hypothesis will be accomplished with the following specific aims: Specific Aim 1. Demonstrate the efficacy of liposome-nanoparticle capsuled miR-223 retro-orbital injection in targeting neuroinflammation and autophagy elicited by CCI. In mice of both sexes, we will identify the cell-type specificity of exogenous delivered miR-223 by fluorescent-activated cell sorting (FACS), in conjugate with biochemistry, and immunohistochemistry (IHC) analysis. Specific Aim 2. Assess targets and potential “off-target” effects of the exogenous delivered miR-223 using “RIP-chip” (RNA immunoprecipitation chip) methodology developed and established in our lab [ref]. “RIP-chip” is highly effective method to stochastically identify and confirm all bona fide targets (including unintended “off-target” effects) in an in vivo biological context. This is a key step to evaluate the miRNA therapeutic potential and we have the unique resources and experience to accomplish this project. Specific Aim 3. Optimize the regimen of liposome-nanoparticle miR-223 retro-orbital injections required to mitigate chronic neuroinflammation and autophagy dysregulation after CCI. We will employ neurobehavioral tests, biochemistry, and IHC to determine an effective combination of injection dosage and timing. Our proposed research is highly translational and the paradigm of CNS miRNA delivery to mitigate TBI- induced brain damage is novel. We expect this research program will have an enduring impact on therapeutic strategies treating secondary neurotoxicity elicited by brain injury and other neurological disorders.