Exosomal miR-494 from Bone Marrow Mesenchymal Stem Cells Attenuates Ferroptosis and Enhances Spinal Cord Injury Repair by Modulating the SIRT1/HO-1 Pathway.

Spinal cord injury (SCI) is a severe traumatic disorder of the central nervous system, often resulting in partial or complete loss of sensory and motor functions. Ferroptosis, a lipid peroxidation-driven apoptotic process triggered by iron overload, has emerged as a novel form of programmed cell death and a focal point in post-SCI cell death research. Exosomes (Exo), as delivery vehicles, exhibit multiple advantages, including superior encapsulation capacity, high targeting efficiency, and enhanced blood-brain barrier penetration to reach the central nervous system. Previous studies have identified exosomes as key carriers of bioactive molecules, including miRNAs. Our prior investigations demonstrated that miR-494 attenuates SCI progression. To investigate the therapeutic mechanism of Exo-miR-494 in SCI, this study conducted in vitro and in vivo experiments using PC12 cell models and rat SCI models. In vitro, qRT-PCR and Western blot were employed to detect the expression levels of miR-494, SIRT1, HO-1, GPX4, and 4HNE, while intracellular oxidative stress markers were measured to clarify the regulatory effects of Exo-miR-494 on cellular oxidative stress and ferroptosis. In vivo, rats with successful SCI modeling were intravenously injected with Exo-miR-494. Fluorescence quantitative PCR, Western blot, and immunofluorescence were comprehensively used to analyze the changes in SIRT1/HO-1 signaling pathway molecules and ferroptosis-related indicators in injured spinal cord tissues. HE staining and Nissl staining were applied to evaluate spinal cord tissue damage and neuronal morphology. Transmission electron microscopy was utilized to observe cellular ultrastructural changes, and Prussian blue staining was combined to detect iron deposition, thereby deeply exploring the ferroptosis mechanism. Finally, Basso, Beattie, Bresnahan (BBB) locomotor scores and inclined plane tests were used to systematically assess the motor function recovery of rats. Results revealed a significant downregulation of miR-494 post-SCI. Exo-miR-494 effectively restored miR-494 levels in injured spinal tissues, suppressed ferroptosis through SIRT1/HO-1 pathway activation, mitigated SCI progression, and enhanced functional recovery in rats. Exosomes derived from rat bone marrow mesenchymal stem cells (BMSCs) delivering miR-494 represent a potential therapeutic strategy for SCI. miR-494 targets injury sites, reduces neuronal ferroptosis after spinal cord injury by regulating the SIRT1/HO-1 signaling pathway, alleviates damage caused by spinal cord injury, and promotes motor function recovery in rats.