The diffuse axonal damage in white matter and neuronal loss, along with excessive neuroinflammation, hinder long-term functional recovery after traumatic brain injury (TBI). MicroRNAs (miRs) are small noncoding RNAs that negatively regulate protein-coding target genes in a posttranscriptional manner. Recent studies have shown that loss of function of the miR-15a/16-1 cluster reduced neurovascular damage and improved functional recovery in ischemic stroke and vascular dementia. However, the role of the miR-15a/16-1 cluster in neurotrauma is poorly explored. Here, we report that genetic deletion of the miR-15a/16-1 cluster facilitated the recovery of sensorimotor and cognitive functions, alleviated white matter/gray matter lesions, reduced cerebral glial cell activation, and inhibited infiltration of peripheral blood immune cells to brain parenchyma in a murine model of TBI when compared with WT controls. Moreover, intranasal delivery of the miR-15a/16-1 antagomir provided similar brain-protective effects conferred by genetic deletion of the miR-15a/16-1 cluster after experimental TBI, as evidenced by showing improved sensorimotor and cognitive outcomes, better white/gray matter integrity, and less inflammatory responses than the control antagomir–treated mice after brain trauma. miR-15a/16-1 genetic deficiency and miR-15a/16-1 antagomir also significantly suppressed inflammatory mediators in posttrauma brains. These results suggest miR-15a/16-1 as a potential therapeutic target for TBI.

Ischemic stroke followed by reperfusion (IR) leads to extensive cerebrovascular injury characterized by neuroinflammation and brain cell death. Inhibition of matrix metalloproteinase-3 (MMP-3) emerges as a promising therapeutic approach to mitigate IR-induced stroke injury. We employed middle cerebral artery occlusion with subsequent reperfusion (MCAO/R) to model ischemic stroke in adult mice. Specifically, we investigated the impact of MMP-3 knockout (KO) on stroke pathophysiology using RNA sequencing (RNA-seq) of stroke brains harvested 48 h post-MCAO. MMP-3 KO significantly reduced brain infarct size following stroke. Notably, RNA-seq analysis showed that MMP-3 KO altered expression of 333 genes (252 downregulated) in male stroke brains and 3768 genes (889 downregulated) in female stroke brains. Functional pathway analysis revealed that inflammation, integrin cell surface signaling, endothelial- and epithelial-mesenchymal transition (EndMT/EMT), and apoptosis gene signatures were decreased in MMP-3 KO stroke brains. Intriguingly, MMP-3 KO downregulated gene signatures more profoundly in females than in males, as indicated by greater negative enrichment scores. Our study underscores MMP-3 inhibition as a promising therapeutic strategy, impacting multiple cellular pathways following stroke.

Ischemic stroke promotes monocyte recruitment to the injured brain and their differentiation into monocyte-derived macrophages (MDMs). These cells contribute to debris clearance but may also exacerbate neuroinflammation. However, the heterogeneity of MDM subsets and the phenotypic transitions that shape MDM functional states during the subacute phase of stroke remain incompletely characterized. To address this, we first performed single-cell RNA sequencing (scRNA-seq) to define the transcriptional landscape of the mouse brain 48 h after transient middle cerebral artery occlusion/reperfusion compared with sham controls. Reclustering of macrophage-lineage cells identified multiple MDM subsets, including a distinct Cd68^hi/Ctsd^hi MDM subset enriched for lysosomal and lipid-processing gene expression programs. Cell trajectory inference supported a transition from early recruited MDMs toward the Cd68^hi/Ctsd^hi state, accompanied by induction of transcriptomic networks that drive MDM function to favor a clearance-competent phenotype in response to ischemic stroke. Complementary single-cell ATAC sequencing (scATAC-seq) demonstrated cell type-specific chromatin remodeling after stroke and revealed MDM subclusters with accessibility at key loci regulating lysosomal function and lipid metabolism. Together, our findings define a cellular and regulatory framework of the subacute post-stroke brain and identify a lysosome-enriched Cd68^hi/Ctsd^hi MDM trajectory, highlighting endolysosomal and lipid-processing programs during early stroke recovery.

Ischemic stroke is a leading cause of death and disability worldwide. Currently, there is an unmet clinical need for pharmacological treatments that can improve ischemic stroke outcomes. In this study, we investigated the role of brain peroxisome proliferator-activated receptor alpha (PPARα) in ischemic stroke pathophysiology. We used a well-established model of cerebral ischemia in PPARα transgenic mice and conducted the RNA sequencing (RNA-seq) of mouse stroke brains harvested 48 h post-middle cerebral artery occlusion (MCAO). PPARα knockout (KO) increased brain infarct size following stroke, indicating a protective role of PPARα in brain ischemia. Our RNA-seq analysis showed that PPARα KO altered the expression of genes in mouse brains with known roles in ischemic stroke pathophysiology. We also identified many other differentially expressed genes (DEGs) upon the loss of PPARα that correlated with increased infarct size in our stroke model. Gene set enrichment analysis (GSEA) and Gene Ontology (GO) analysis revealed the upregulation of gene signatures for the positive regulation of leukocyte proliferation, apoptotic processes, acute-phase response, and cellular component disassembly in mouse stroke brains with PPARα KO. In addition, pathway analysis of our RNA-seq data revealed that TNFα signaling, IL6/STAT3 signaling, and epithelial–mesenchymal transition (EMT) gene signatures were increased in PPARα KO stroke brains. Our study highlights PPARα as an attractive drug target for ischemic stroke due to its transcriptional regulation of inflammation-, apoptosis-, and EMT-related genes in brain tissue following ischemia.