OBJECTIVETo investigate the anti-inflammatory effect of electroacupuncture in rats with bupivacaine-induced lumbar multifidus injury and its underlying regulatory mechanism on macrophage polarization.METHODSA total of seventy-two Sprague-Dawley male rats were randomly divided into control, model, and electroacupuncture groups. Forty-eight rats categorized in model groups were injected 0.5% bupivacaine (BPVC) into the lumbar multifidus at the L4-L5 segment. Rats in the electroacupuncture groups received the intervention for 1, 2, 3 and 5 d, respectively. The degree of macrophage infiltration and change of M1/M2 polarization were observed based on hematoxylin and eosin staining, immunohistochemistry and immunofluorescence to evaluate the anti-inflammatory effect of electroacupuncture. Meanwhile, exosomal miRNA-sequencing and bioinformatics analysis predicted the pathways and biological processes related to inflammatory response and macrophage polarization regulated by electroacupuncture intervention.RESULTSBPVC injection induced the infiltration of local macrophages at the L4-L5 segment of lumbar multifidus. Comparison of mean IOD values with 2 d and 5 d post injury revealed the highest expression of CD68+ macrophages on day 3 post injury by immunohistochemistry. (P < 0.001, P < 0.001, respectively). Compared with the model group, the cell counts of iNOs+ CD68+ M1-macrophages were lower in the electroacupuncture group, while the positive percent of CD163+ CD206+ M2-macrophages was higher in the electroacupuncture group, on day 3 after BPVC injection (P < 0.001, P < 0.001, respectively). Moreover, the results of sequencing and bioinformatic analysis suggested that exosomal miRNAs were involved in the EA regulating macrophage polarization.CONCLUSIONSElectroacupuncture can promote macrophage polarization to reduce inflammation following lumbar multifidus muscular injury.