Effect of electroacupuncture at "Weizhong" (BL40) on expression of muscular PDGF-CC, PDGFR-α and MMP-1 in rats with lumbar multifidus muscle injury

Abstract

To observe the effect of electroacupuncture (EA) of "Weizhong" (BL40) on the expression of platelet-derived growth factor (PDGF)-CC, PDGF receptor (PDGFR)α and matrix metalloproteinase-1 (MMP-1) in rats with lumbar multifidus muscle injury (LMMI) so as to study its mechanisms underlying improvement of skeletal muscle injury. Fifty-four male SD rats were randomly divided into normal group (n=6), model group (n=24) and EA group (n=24), and the latter two groups were further divided into four subgroups (1, 3, 5 and 7 days), with 6 rats in each group. The LMMI model was established by injection of 0.5% bupivacaine (BPVC, 100 μL×4) into the multifidus along the L4 and L5 spinous process. EA (2 Hz/50 Hz, 1 mA) was applied to bilateral "Weizhong"(BL40) for 20 min, once daily for 1, 3, 5 and 7 days respectively, from the first day on after modeling. Histopathological changes of the left multifidus muscle were observed after H.E. staining, and the expression of PDGF-CC, PDGFR-α and MMP-1 proteins in the right multifidus was observed by Western blot. Compared with the normal group, the expression levels of PDGF-CC protein in the model subgroup 1 d, 3 d and 7 d were significantly decreased (P<0.05), and those of PDGFR-α and MMP-1 proteins in the model subgroup 5 d and 7 d, and PDGF-CC protein in the model subgroup 5 d significantly increased (P<0.05). In comparison with the model subgroups, the expression levels of PDGF-CC in the EA subgroup 3 d, 5 d and 7 d, PDGFR-α in the EA subgroup 5 d, and MMP-1 in the EA group 3 d and 5 d were significantly increased or significantly further increased (P<0.05). H.E. staining showed different shapes and uneven sizes, with large area of damage, enlarged muscle space and inflammatory cell infiltration in the model group, which was relatively milder in the EA subgroups particularly in subgroup 5 d and 7 d. EA stimulation of BL40 for about 5 days has a positive effect in promoting the repair of the injured multifidus muscle in LMMI rats, which may be related to its function in up-regulating the expression of muscular PDGF-CC, PDGFR-α and MMP-1 proteins.