[Effect of electroacupuncture combined with Schwann cell transplantation on limb locomotor ability, regional remyelination and expression of spinal CD4 and CD8 proteins in compressive spinal injury rats].

Objective: To observe the effect of electroacupuncture (EA) combined with transplantation of Schwann cells (SCs) on limb locomotor, myelin sheath repair and expression of CD4 and CD8 in compressed spinal cord injury (CSCI) rats, so as to explore its mechanisms underlying improvement of CSCI.

Methods: A total of 45 female SD rats were randomly divided into normal control, model, EA, Schwann cell (SC) transplantation, and EA＋SC transplantation groups (＝9 rats in each group). The CSCI model was established by laminectomy at T12-L2 and clip compression. Rats of the SC transplantation group accepted injection of the cultured SC suspension (2×10/6 µL) into the central, upper and lower sites of the injured spinal cord (5 mm in depth) 7-8 days after CSCI modeling. EA (2 Hz) was applied to bilateral "Zusanli" (ST36) and "Sanyinjiao" (SP6) for 10 min, once daily and 6 days a week for 3 weeks. The Basso, Beattie and Bresnahan locomotor rating scale (BBB scale) was used to evaluate the function state of CSCI. Morphological changes of the regional injured tissue were observed under light microscope after H．E. staining. The myelin sheath repair state and survival of SCs were detected by Luxol fast blue (LFB) staining and immunofluorescence histochemistry, and the expression of CD4, CD8 and P0 of the injured spinal cord was detected by Western blot.

Results: Compared with the normal control group, the BBB scores at the time-points of 0 d, and 1, 2, and 3 weeks were significantly decreased in the model group (<0.001), and those of the EA＋SC transplantation group at the 2 and 3 week were significantly higher than those of the model group (<0.05). No significant changes of BBB scores were found after EA and SC transplantation relevant to the model group (>0.05). LFB staining showed a disordered arrangement of the nerve fibers in the white matter, myelinociasis and obvious decrease of the medullated fibers in the model group, and these situations were relatively milder in both EA and SC transplantation groups and obviously milder in the EA＋SC transplantation group. H．E. staining displayed that the structure of the injured region of the spinal cord was incomplete, accompanied with a large number of defect cavities and neuronal karyopyknosis in the model group, while the structure was relatively clear, with an increase of the normal neurons and fewer neuronal karyopyknosis in the EA＋SC transplantation group. Compared with the normal control group, MBP in the model group was significantly decreased (<0.001)，and P0 was significantly increased (<0.001). Compared with the model group, the expressions of MBP and P0 were significantly increased in the EA, SC transplantation, and EA＋SC transplantation groups (<0.01, <0.001), and was significantly higher in the EA＋SC transplantation group than in both EA and SC transplantation groups (<0.001). The average immunofluorescence intensity of Hoechst33342-labeled SCs was significantly higher in the EA＋SC transplantation group than in the SC transplantation group (<0.05). After CSCI, the expression levels of spinal CD4, CD8 and P0 proteins had no significant changes in comparison with the normal control group (>0.05), while after the intervention and in comparison with the model group, the expression levels of P0 protein were significantly increased in the EA, SC transplantation and EA＋SC transplantation groups (<0.05), and was significantly higher in the EA＋SC transplantation group than in both EA and SC transplantation groups (<0.05). The expression levels of CD4 and CD8 proteins were significantly lower in the EA＋SC transplantation group than in the SC transplantation group (<0.05)．.

Conclusion: EA＋SCs transplantation can improve the locomotor function in CSCI rats, which may be related to its effects in increasing the survival of transplanted SCs to promote the remyelination and in reducing the immune rejecting reaction.