Objective: To observe the effect of electroacupuncture (EA) of "Jiaji" (EX-B 2) on limb locomotor function and expression of Ras homolog gene family member A (RhoA), Rho-associated kinase Ⅱ (ROCK Ⅱ) and myosin light chain (MLC) proteins in the anterior horn of spinal cord in acute spinal cord injury (ASCI) rats, so as to explore its mechanisms under-lying improvement of SCI-induced limb locomotor dysfunction.
Methods: Forty-eight female Wistar rats were randomly divided into sham operation (sham), ASCI model (model), EA EX-B 2 (EA) and ROCK inhibitor (Fasudil) groups which were further divided into 14 d and 28 d subgroups (n=6 in each). The ASCI model was made by using weight drop striking method. Three hours after modeling, EA (100 Hz, 0.4, 0.6 mA) was applied to EX-B 2 (T 9, T 11) for 30 min, once daily for 14 d and 28 d, respectively. The ROCK inhibitor (hydrochloride Fasudil, 10 mg/kg) was administrated by intraperitoneal injection immediately after modeling, once a day, continuously for 14 d or 28 d. The expression of RhoA, ROCK Ⅱ and MLC proteins in the spinal cord anterior horn tissue (T 10) was detected by immunohistochemistry. The rats' hindlimb locomotor function was assessed according to Basso, Beattie and Bresnahan (BBB) locomotor rating scale (21-points).
Results: After ASCI, the BBB scores were significantly lower in the model group than in the sham group on day 14 and 28 (P<0.05), and obviously higher in the EA and inhibitor groups than in the model group (P<0.05), suggesting an improvement of the hindlimb locomotor function after EA intervention or suppression of ROCK. Immunohistochemical results indicated that the numbers of RhoA, ROCK Ⅱ and MLC immune-reaction positive cells in the anterior horn of spinal cord were significantly more in the model group than in the sham group (P<0.05), and remarkably decreased in both EA and inhibitor groups on day 14 and 28 relevant to the model group (P<0.05). The therapeutic effects of EA were markedly weaker than those of inhibitor Fasudil in up-regulating BBB score and down-regulating the number of RhoA, ROCK Ⅱ and MLC positive cells (P<0.05).
Conclusion: EA of EX-B 2 can improve the hindlimb locomotor function in ASCI rats, which may be associated with its effect in down-regulating the expression of RhoA, ROCK Ⅱ and MLC proteins (i.e., inhibiting the RhoA/ROCK signaling pathway) in the anterior horn of spinal cord.
Keywords: MLC; Acute spinal cord injury; Electroacupuncture; Myelin-associated inhibitory factors; ROCK Ⅱ; Rho/ROCK Ⅱ signaling pathway; RhoA.