Bone marrow mesenchymal stem cells induce M2 microglia polarization through PDGF-AA/MANF signaling

Cerebral ischemia remains the most frequent cause of death and quality-of-life impairments due to neurological deficits, and accounts for the majority of total healthcare costs. However, treatments for cerebral ischemia are limited. Over the last decade, bone marrow stromal cell (BMSC) therapy has emerged as a particularly appealing option, as it is possible to help patients even when initiated days or even weeks after the ischemic insult. BMSCs are a class of multipotent, self-renewing cells that give rise to differentiated progeny when implanted into appropriate tissues. Therapeutic effects of BMSC treatment for ischemic stroke, including sensory and motor recovery, have been reported in pre-clinical studies and clinical trials. In this article, we review the recent progress in BMSC-based therapy for ischemic stroke, focusing on the route of delivery and pre-processing of BMSCs. Selecting an optimal delivery route is of particular importance. The ideal approach, as well as the least risky, for translational applications still requires further identification. Appropriate preprocessing of BMSCs or combination therapy has the benefit of achieving the maximum possible restoration. Further pre-clinical studies are required to determine the time-window for transplantation and the appropriate dosage of cells.

Background: Ischemic stroke remains a leading cause of mortality and disability worldwide. Microglia, the resident immune cells of the central nervous system, perform critical roles in immune surveillance, debris clearance, and tissue repair. Analyzing the heterogeneity, activation trajectories, and metabolic states of microglia in ischemic stroke is essential for discovering therapeutic targets. Methods: We performed single-cell RNA sequencing (scRNA-seq) on brains from ischemic and control rats and identified transcriptionally distinct microglial subpopulations. We conducted differential expression, pathway enrichment, pseudotime analysis, regulatory network inference, and cell-cell communication mapping to characterize functional states, key transcription factors, and intercellular crosstalk underlying microglial responses following cerebral ischemia-reperfusion injury. We used Real-Time Quantitative PCR (RT-qPCR), Western blot, and immunohistochemistry to measure relative RNA and protein expression levels. Results: We identified seven microglial subclusters with distinct transcriptional signatures. Ischemia-associated clusters exhibited strong activation of inflammatory pathways, increased glycolysis and lipid metabolism, and suppressed TCA cycle and oxidative phosphorylation (OXPHOS), reflecting a shift toward proinflammatory, energy-demanding phenotypes. Pseudotime analysis revealed transitions from homeostatic to pathological states, highlighting potential therapeutic windows. Regulatory network analysis identified activating transcription factor 3 (ATF3) as a central regulator controlling the expression of cholesterol 25-hydroxylase (CH25H) and secreted phosphoprotein 1 (SPP1). Notably, ATF3 overexpression enhanced CH25H expression and selectively increased proinflammatory cytokine production, linking metabolic reprogramming to neuroinflammatory responses. Cell-cell communication analysis further revealed extensive remodeling of interactions with astrocytes, endothelial cells, and fibroblasts, potentially amplifying postischemic neuroinflammation. Conclusion: Our study demonstrates that cerebral ischemia induces transcriptionally and functionally distinct microglial subpopulations, characterized by metabolic reprogramming and proinflammatory activation. ATF3 serves as a central regulator linking CH25Hmediated metabolic changes to cytokine-driven neuroinflammation, highlighting potential therapeutic targets for modulating microglial responses and mitigating ischemia-induced brain injury.