Electroacupuncture Improves the Motor Function in Rats with Spinal Cord Injury by Regulating UCN2-Mediated cAMP-PKA Signaling in the Spinal Cord Microenvironment

Spinal cord injury (SCI) has a high mortality and disability rate and can result in severe neurological deficits and complications. The process of SCI is complex and has a long duration. Studies suggest that urocortin 2 (UCN2) is associated with motor functions regulated by the spinal cord. However, the role of electroacupuncture (EA) in regulating UCN2 at different times after SCI and its underlying molecular mechanisms remain unclear. The SCI animal model was established in SD rats by complete transection of the right spinal cord at the T10 level. EA was applied to the T9 and T11 Jiaji points. Behavioral analyses were performed at 1, 3, 7, 14 and 28 days post-injury (d.p.i.), and cellular morphology was observed in spinal cord tissue obtained from the injury site. RNA sequencing was carried out, and the results were validated. The use of EA significantly improved the behavioral scores and hind-limb locomotion in rats with SCI at 7, 14, and 28 d.p.i. (p < 0.05). At 3 d.p.i, the treatment resulted in a reduction in the number of astrocytes in the periphery of the injury site (p < 0.05), as well as a reduction in the extent of glial scar formation. Additionally, the number of microglia was increased, while neuronal apoptosis was suppressed (p < 0.05). At 14 and 28 d.p.i., the number of astrocytes was increased (p < 0.05), the number of microglia was decreased (p < 0.05), and the positive staining ratio of neurofilaments (NF) and myelin basic protein (MBP) was elevated (p < 0.05). Post-injury RNA sequencing showed that there were significant changes in UCN2 expression. The protein-protein interaction (PPI) network and KEGG enrichment analysis indicated a strong connection between UCN2 and the downstream cAMP-PKA signaling pathway. Subsequent qPCR, Western blotting, and immunohistochemistry experiments confirmed that EA significantly reduced the expression of UCN2, PKA, NF-κB, and NMDAR in rats with SCI at 1 and 3 d.p.i. (p < 0.05) while increasing the expression of UCN2, PKA, and CREB at 7, 14, and 28 d.p.i. (p < 0.05). By modulating UCN2, EA can activate the downstream cAMP-PKA signaling pathway. This process improves the presence of astrocytes and microglia around the injury site, inhibits neuronal apoptosis, and increases the number of myelin sheaths and NF. As a result, hind-limb locomotor ability is restored in rats with SCI.