Abstract: BACKGROUND: The analgesic effect of stagnant moving needle on myofascial pain syndrome is remarkable, but the analgesic mechanism is still unclear. 
OBJECTIVE: To investigate the analgesic mechanism of stagnant moving needle acupuncture in the treatment of myofascial pain syndrome. 
METHODS:  Fifty-four SD rats were randomly divided into a blank group (n=16) and a modeling group (n=38). The models of left myofascial pain syndrome in the modeling group were prepared by using the method of “striking combined with centrifugal movement”. Twelve weeks after modeling, six mice were randomly selected to verify the success of the modeling. The rest of the 32 rats were randomly divided into the model group and the stagnant moving needle group, with 16 rats in each group. The stagnant needle moving group was treated by stagnant moving needle into the local excitation point nodule of the left medial vastus muscle fascia in rats, twice a week, for 4 weeks. The mechanical foot contraction reflex threshold of the left foot were measured weekly in the pre/post modeling and post-intervention groups of rats. At 4 weeks after treatment, hematoxylin-eosin staining was used to observe the morphological changes in the muscle tissue of the left medial femoral muscle of rats, ELISA was used to detect the levels of substance P and β-endorphin in the serum and the gray matter around the midbrain aqueduct. Immunohistochemistry was used to detect positive expression of microglia markers (Iba-1) and c-fos in the gray matter around the midbrain aqueduct. Western blot assay was used to detect the expression level of brain-derived neurotrophic factor protein in the periaqueductal gray.
RESULTS AND CONCLUSION: Compared with the blank group, the mechanical pain threshold of the rats in the model group and the stagnant moving needle group decreased after modeling (P < 0.05). After 4 weeks of treatment, the mechanical pain threshold of the rats in the stagnant moving needle group was higher than that in the model group (P < 0.05). Hematoxylin-eosin staining results showed that in the model group, the muscle fibers of the left lower limb medial femoral muscle of rats were disorganized, unequal in thickness, myocytes were enlarged, with inward movement of the nucleus, rounded contracture nodules and tension bands; whereas in the stagnant moving needle group, the muscle fibers were arranged in a neat way, the myocytes were angular, and the contracture nodules were occasionally seen. Compared with the blank group, the expression of substance P in the serum of the model group was significantly higher (P < 0.05), while the levels of β-endorphin in serum and substance P and β-endorphin in brain were decreased (P < 0.01). Compared with the model group, the level of serum substance P in the stagnant moving needle group was decreased (P < 0.05), and the levels of serum β-endorphin and brain substance P and β-endorphin were increased (P < 0.05). Compared with the blank group, the positive expression of c-fos and Iba-1 and the protein of brain-derived neurotrophic factor in the model group were increased (P < 0.05). Compared with the model group, the positive expression of c-fos in the stagnant moving needle group was increased (P < 0.05), and the positive expression of Iba-1 and the protein of brain-derived neurotrophic factor were decreased (P < 0.05). These findings suggest that stagnant moving needle may indirectly promote the release of β-endorphin by microglia polarized to the M2 phenotype and increase the excitability of c-fos neurons by inhibiting the activity of microglia in the gray matter around the periaqueductal gray and downregulating the expression of brain-derived neurotrophic factor protein, thereby reducing the degree of central sensitization and effectively relieving myofascial pain syndrome. 

中国组织工程研究杂志出版内容重点：组织构建；骨细胞；软骨细胞；细胞培养；成纤维细胞；血管内皮细胞；骨质疏松；组织工程

Key words: myofascial pain syndrome, myofascial trigger points, stagnant moving needle, central analgesia, brain-derived neurotrophic factor, periaqueductal gray