Objective

2

To explore the effect and mechanism of acupuncture at "Weizhong" (BL40) on microcirculation of paravertebral skeletal muscle in rats with chronic blunt injury of lumbar muscle based on the insulin-like growth factor-1 (IGF-1)/phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) pathway.

Methods

2

Forty-eight SPF-grade SD rats were randomized into a blank group (8 rats) and a modeling group (40 rats). Chronic blunt injury model was established by weight impact method in the modeling group. Forty rats were successfully modeled

and were randomly divided into a model group

an acupuncture at Weizhong group (Weizhong group)

an acupuncture at non-acupoint group (non-acupoint group)

an inhibitor group

and an inhibitor+acupuncture at Weizhong group (inhibitor+Weizhong group)

8 rats in each group. In the Weizhong group and the inhibitor+Weizhong group

acupuncture was applied at bilateral "Weizhong" (BL40). In the non-acupoint group

acupuncture was applied at non-acupoints

i.e. points 0.5 cm inward from bilateral "Weizhong" (BL40). The acupuncture intervention was delivered 20 min each time

once a day for continuous 2 weeks. In the inhibitor group and the inhibitor+Weizhong group

intraperitoneal injection of IGF-1 receptor (IGF-1R) inhibitor was given once a day

at a dosage of 2 mg/100 g

for continuous 2 weeks. Before modeling and on the 1st

7th and 14th days of intervention

the body mass was measured. Before and after modeling

and after intervention

the limb grip strength and paw withdrawal threshold (PWT) were measured. After intervention

the morphology of psoas muscle was observed by HE staining; the ultrastructure of psoas muscle capillaries was observed by electron microscopy; the levels of serum vascular endothelial growth factor (VEGF) and endothelial nitric oxide synthase (eNOS) were detected by ELISA; and the protein and mRNA expression of IGF-1

IGF-1R

PI3K

AKT of psoas muscle was detected by Western blot and real-time PCR.

Results

2

Compared with the blank group

in the model group

the body mass on the 7th and 14th days of intervention

the limb grip strength

and the PWT of left and right hind feet were decreased (

P

<

0.001

P

<

0.01); the skeletal muscle cells showed enlarged intercellular space

loosely arranged and irregularly shaped

the capillaries in the psoas muscle tissues were edematous

and the lumen of the blood vessels was obviously atrophied; the levels of serum VEGF and eNOS were decreased (

P

<

0.001); in psoas muscle

the protein expression of IGF-1 and IGF-1R

as well as the p-PI3K/PI3K

p-AKT/AKT values were decreased (

P

<

0.001)

the mRNA expression of IGF-1

IGF-1R

PI3K and AKT was decreased (

P

<

0.001

P

<

0.05). Compared with the model group

in the Weizhong group

the body weight was increased on the 7th and 14th days of intervention (

P

<

0.001)

the limb grip strength and the PWT of the left and right hind feet were increased (

P

<

0.001

P

<

0.01); the arrangement of the skeletal muscle cells was relatively tight and the intercellular space was reduced

the blood vessels tended to be regular and the structure of the basement membrane was continuous

while the lumens of blood vessels were collapsed locally; the levels of serum VEGF and eNOS were increased (

P

<

0.001); in psoas muscle

the protein expression of IGF-1 and IGF-1R

as well as the p-PI3K/PI3K

p-AKT/AKT values were increased (

P

<

0.001)

the mRNA expression of IGF-1

IGF-1R

PI3K and AKT was increased (

P

<

0.001

P

<

0.01). Compared with the model group

in the inhibitor group

the body mass was decre

ased on the 7th and 14th days of intervention (

P

<

0.05

P

<

0.01); the limb grip strength and the PWT of the left hind foot were decreased (

P

<

0.01

P

<

0.001); the intercellular space of skeletal muscle cells was larger

the nuclei of the cells and erythrocytes were scattered in the intercellular space

the damage of the capillaries in the muscular tissues was serious

the collagen fibers were sparsely distributed and disorganized; the levels of serum VEGF and eNOS were decreased (

P

<

0.001

P

<

0.01); in psoas muscle

the protein expression of IGF-1 and IGF-1R

as well as the p-PI3K/PI3K and p-AKT/AKT values were decreased (

P

<

0.01

P

<

0.05

P

<

0.001)

the mRNA expression of IGF-1

IGF-1R

PI3K

and AKT was decreased (

P

<

0.01

P

<

0.001

P

<

0.05). Compared with the Weizhong group

in the non-acupoint group and the inhibitor+Weizhong group

the body mass was decreased on the 7th and 14th days of intervention (

P

<

0.001

P

<

0.01)

the limb grip strength was decreased (

P

<

0.001); the morphology of muscle cell was relatively poor

with generally irregular

there was mild collapse and atrophy in the vascular lumen

and mild edema in the endothelial cells; the levels of serum VEGF and eNOS were decreased (

P

<

0.001); in psoas muscle

the protein expression of IGF-1 and IGF-1R

as well as the p-PI3K/PI3K and p-AKT/AKT values were decreased (

P

<

0.01

P

<

0.001)

the mRNA expression of IGF-1

IGF-1R

PI3K

and AKT was decreased (

P

<

0.001

P

<

0.01

P

<

0.05). Compared with the Weizhong group

the PWT of the left hind foot was decreased in the non-acupoint group (

P

<

0.001)

and PWT of the left and right hind feet was dec

reased in the inhibitor+Weizhong group (

P

<

0.001).

Conclusion

2

Acupuncture at "Weizhong" (BL40) promotes lumbar muscle repair in chronic low back pain

its mechanism may be related to the activation of the IGF-1/PI3K/AKT pathway

thereby improving the microcirculation.