Objective 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. Methods 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. Results 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. Conclusion 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.