Exosomes from adipose-derived stem cells enhance functional recovery after spinal cord injury by inhibiting ferroptosis and promoting the survival and function of endothelial cells through the Nrf2/SLC7A11/GPX4 pathway

Background: Spinal cord injury (SCI) is a devastating disease that causes major motor, sensory and autonomic dysfunctions. Currently, there is a lack of effective treatment methods. In this study, we aimed to investigate the potential mechanisms of Exosomes from adipose-derived stem cells (ADSC-Exos) in reducing ferroptosis and promoting angiogenesis after spinal cord injury. Methods We isolated ADSC-Exos, the characteristics of which were confirmed. In vitro, we tested the potential of ADSC-Exos to promote the survival and function of human brain microvascular endothelial cells (HBMECs) with tube formation assays, scratch assays and Transwell assays and analyzed the ferroptosis of HBMECs with western blotting, immunofluorescence and biochemical detection. In vivo, we established a rat model of SCI by the modified Allen's method and locally injected ADSC-Exos to verify their efficacy. Results ADSC-Exos can reduce reactive oxygen species (ROS) accumulation and cell damage induced by an excessive inflammatory response in HMBECs. ADSC-Exos inhibit ferroptosis induced by excessive inflammation and upregulate the expression of glutathione peroxidase 4(GPX4) in HMBECs. It can also effectively promote proliferation, migration, and vessel-like structure formation. In vitro ADSC-Exos improved behavioral function at days 3, 7, and 14 after SCI and increased the number and density of blood vessels around the damaged spinal cord by approximately 30.4% ± 4.4%. Moreover, we found that ADSC-Exos could increase nuclear factor erythroid-2-related factor 2(Nrf2) expression and nuclear translocation, thereby affecting the expression of solute carrier family 7 member 11(SLC7A11) and GPX4, and the Nrf2 inhibitor ML385 could reverse the above changes. Conclusion In summary, our results suggest that ADSC-Exos may inhibit ferroptosis and promote the recovery of vascular and neural functions after SCI through the Nrf2/SLC7A11/GPX4 pathway. This may be a potential therapeutic mechanism for spinal cord injury.