Introduction: The molecular response following brain ischemia is very complex, and the mechanisms underlying spontaneous recovery are unclear. This study investigates the molecular mechanisms driving spontaneous recovery after unilateral experimental stroke using RNA sequencing (RNAseq) transcriptome analysis of the ipsi-lesional and the contra-lesional primary motor cortex (iM1 and cM1).
Methods: Ischemic stroke was induced in C57BL/6J adult male mice by transient MCAO. Behavior tests were performed at pre-stroke baseline and post-stroke days (PD) 4, 8, and 14. All mice were sacrificed at PD15 and processed for immunohistochemistry or RNAseq. Infarcts were visualized by T2WI at PD2 using 7T MR scanner or histology at PD15. All stroke mice included in the study have comparable cortico-striatal infarcts and exhibit similar pre-stroke baseline performance and PD4 deficits. These mice were further categorized into spontaneously-recovered and non-recovered groups based on their rotating beam performance during recovery.
Results: Out of 34 stroke mice with above-mentioned similar conditions, 9 (26%) were categorized into spontaneously-recovered group and 25 (74%) were categorized into non-recovered group. After PD4, the spontaneously-recovered group exhibited significant improvement in beam performance in distance traveled and speed compared to PD4 (p<0.05, respectively). Supervised clustering analysis of differentially expressed genes (DEGs) revealed clear separation between recovery groups only in the cM1. Comparison of the RNAseq transcriptome between recovery groups revealed that 215 genes were significantly altered in the cM1. Ingenuity Pathway Analysis revealed significant differential molecular pathways, including axonal guidance signaling, and neuroinflammatory pathways.
Conclusions: Our study demonstrates that stroke mice with similar cerebral stroke lesion can exhibit significant differences in their behavioral recovery outcome. RNAseq transcriptome analysis revealed significant pathways in contralesional M1, highlighting its involvement in driving spontaneous recovery at post-stroke 2 weeks. Validation of key molecular candidates would provide insights into the molecular mechanisms mediating spontaneous recovery after stroke.
Patient Care: By learning molecular/pathway mechanisms driving spontaneous recovery after stroke, and the different role of the ipsi-lesional and the contra-lesional primary motor cortex (iM1 and cM1), we might be able to learn the mechanisms of stroke patient functional recovery, and then possibly neurosurgeon might be able to promote their recovery.
Learning Objectives: By the conclusion of this presentation, participants should be able to: 1) Describe that stroke mice with similar large cerebral infarct can exhibit significant differences in their behavioral recovery outcome. 2) Identify the difference of the role of ipsi- and contra-lesional motor cortex in spontaneously recovered and non-recovered mice after experimental unilateral stroke. 3) Discuss molecular/pathway mechanisms underlying spontaneous functional recovery after stroke and its difference in rodents and human.