Abstract MP58: Motor Cortex and Spinal Cord Transcriptome After Post-Stroke Optogenetic Neuronal Stimulation

Abstract

Background: Post-stroke brain stimulation is a promising neurorestorative technique to promote recovery. However, the underlying molecular mechanisms driving recovery are still unclear. Here we investigate the molecular changes in both the primary motor cortex and the cervical spinal cord after large cortical stroke in mice receiving repeated optogenetic stimulations in the ipsilateral primary motor cortex (iM1). Methods: C57Bl6 male mice (8 weeks) underwent stereotaxic surgery to express Channelrhodopsin2 in excitatory neurons in iM1, with optical fiber implanted in the same location. After five weeks the mice underwent a transient middle cerebral artery occlusion to induce stroke. Optogenetic stimulations were given daily from post-stroke days (PD) 5-14. Non-stimulated mice were used as controls. Rotating beam test was used to evaluate functional recovery after stroke. At PD 7 and 15, ipsi- and contralesional primary motor cortex (iM1 and cM1) and cervical spinal cords (iSp and cSp) were dissected and processed for RNA sequencing. Results: Repeated iM1 stimulations resulted in a robust recovery on the rotating beam test at PD14, with significant improvement in distance traveled (p<0.05). RNA sequencing analysis (stimulated vs non-stimulated mice) revealed differential transcriptome in both motor cortex and spinal cord. Higher number of differentially expressed genes (DEGs) were observed in the ipsilesional regions (iM1 and iSp). At PD 7, stimulated mice exhibited upregulation of activity-dependent and neuroplasticity-related genes in iM1. Interestingly, at PD15, cholesterol metabolism and neuroinflammatory related genes in iM1 were downregulated. The expressions of the genes were negatively correlated with behavioral recovery. Higher number of DEGs were altered in the spinal cord than motor cortex, suggesting more dynamic molecular changes occur in this area during the post-stroke reinnervation processes. Expressions of synaptogenesis related genes were altered in both iSp and cSp at both timepoints. Conclusions: These transcriptome data reveal important insights into the molecular signaling involved in post-stroke stimulation-induced recovery and provide potential drug targets for enhancing recovery in stroke patients.