Endothelial Progenitor-Derived exosomes Induce Macrophage M2 Polarization via SOCS3/JAK2/STAT3 axis and Improve the Outcome of Spinal Cord Injury

Abstract Background Macrophage in the spinal cord injury (SCI) area imparts a chronic pro-inflammation effect that challenges the recovery of SCI. Previously, endothelial progenitor cell-produced exosomes (EPC-EXOs) have been noticed to facilitate revascularization and inflammation control after SCI. However, their effects on macrophage polarization remained unclear. This study aimed to investigate the EPC-EXOs' role in macrophage polarization and reveal its underlying mechanism. Methods We extracted the macrophages and EPC from the bone marrow suspension of C57BL/L mice by centrifugation. After cell identification, the EPC-EXOs were collected by ultra-high-speed centrifugation and exosome extraction kits and identified by transmission electron microscopy and nanoparticle tracking analysis. Then, macrophages were cultured with EPC-EXOs in different concentrations. We labeled the exosome to confirm its internalization by macrophage and detected the macrophage polarization marker level both in vitro and in vivo. We further estimated EPC-EXOs' protective effects on SCI by mice spinal cord tissue H&E staining and motor behavior evaluation. Finally, we performed RT-qPCR to identify the upregulated miRNA in EPC-EXOs and manipulate its expression to estimate its role in macrophage polarization, SOCS3/JAK2/STAT3 pathway activation, and motor behavior improvement. Results We found that EPC-EXOs decreased the macrophages’ M1 polarization marker expression and increased their M2 polarization marker expression on the 7 and 14 days after SCI. The spinal cord H&E staining results showed that EPC-EXOs raised the tissue-sparing area rate significantly after 28 days of SCI and the motor behavior evaluation indicated an increased BMS score and motor evoked potential by EPC-EXOs treatment after SCI. The RT-qPCR assay identified that miR-222-3P was specifically upregulated in EPC-EXOs and its miRNA-mimic also decreased the M1 polarization and increased the M2 polarization of macrophages. Additionally, miR-222-3P mimic activated the SOCS3/JAK2/STAT3 pathway, and SOCS3/JAK2/STAT3 pathway inhibition blocked miR-2223P’s effects on macrophage polarization and mouse motor behavior. Conclusion Comprehensively, we discovered that EPC-EXOs-derived miR-222-3P affected macrophage polarization via SOCS3/JAK2/STAT3 pathway and promoted mouse functional repair after SCI. This reveals EPC-EXOs’ role in macrophage polarization and will provide a novel interventional strategy to induce the poste-SCI recovery.