hUC-MSC-derived exosomes ameliorate Alzheimer's disease pathology through lncRNA-9969-mediated multi-target protection involving neuronal autophagy and microglial modulation.
BACKGROUND: Alzheimer's disease is characterized by intertwined pathologies including neuroinflammation, driven by microglial dysfunction, and metabolic disturbances such as lipid dyshomeostasis. Mesenchymal stem cell-derived exosomes (MSC-Exos) hold therapeutic promise, Still, it is unknown whether they can simultaneously address these co-occurring impairments via specific molecular cargos, such as long non-coding RNAs (lncRNAs). METHODS: Transcriptome sequencing of exosomes derived from human umbilical cord mesenchymal stem cells (hUC-MSCs) revealed high expression of the long noncoding RNA ENST00000629969 (hereinafter referred to as lncRNA-9969). We isolated exosomes from hUC-MSCs (WT-Exo) and established human umbilical cord blood mesenchymal stem cells stably knocked down for lncRNA-9969 via siRNA, from which corresponding exosomes (KD-Exo) were isolated. Cross-species analysis identified the mouse homolog of lncRNA-9969 as ENSMUST00000200021 (hereinafter referred to as lncRNA-0021). Cellular experiments employed an Aβ₂₅₋₃₅-induced SH-SY5Y cell model to evaluate the protective effects of exosomes. In animal experiments, 6-month-old APP/PS1 mice received biweekly tail vein injections of WT-Exo or KD-Exo for 4 weeks. Phenotypic and mechanistic analyses were subsequently conducted using the Morris water maze, Western blot, immunofluorescence, qPCR, and transmission electron microscopy. RESULTS: In Aβ-injured SH-SY5Y cells, WT-Exo significantly attenuated cellular damage and promoted Aβ clearance, whereas the protective effect of KD-Exo was markedly reduced. In APP/PS1 mice, WT-Exo treatment significantly improved spatial memory deficits and upregulated hippocampal expression of synaptic proteins synaptophysin (Syn) and brain-derived neurotrophic factor (BDNF). Molecular mechanism studies demonstrated that lncRNA-0021 directly binds mmu-miR-6361. Through this ceRNA mechanism, exosome-delivered lncRNA activated the mTOR/p70S6K autophagy pathway, regulated lipid metabolism-related genes, promoted microglial polarization toward the protective M2 phenotype, and suppressed pyroptosis. These beneficial changes were not observed in the KD-Exo-treated group. CONCLUSIONS: hUC-MSC-derived exosomes exert neuroprotective effects by delivering functional lncRNA-9969. Its highly conserved homolog in mice, lncRNA-0021, achieves coordinated multi-target regulation of neuroinflammation, pyroptosis, and metabolic disturbances by sequestering miR-6361 and activating downstream signaling pathways. This study elucidates the central role of exosomal lncRNAs in AD pathology and provides new insights for developing RNA-based multi-target therapeutic strategies.