Effects of electroacupuncture at "Jiaji" (EX-B 2) on extracellular matrix of chondrocytes and inflammatory reaction in rabbits with Modic changes of cartilage endplate

Abstract

To observe the effects of electroacupuncture (EA) at "Jiaji" (EX-B 2) on extracellular matrix (ECM) of chondrocytes and inflammatory reaction in rabbits with Modic changes (MC) of cartilage endplate, and to explore the mechanism of EA in treating MC of endplate cartilage. Eighteen male New Zealand white rabbits were randomly divided into a sham operation group, a model group and an EA group, 6 rabbits in each group. Based on the autoimmune theory, MC model was established by embedding autogenous nucleus pulposus in the rabbits of the model group and the EA group, based on autoimmunity. After successful modeling, EA was applied at bilateral "Jiaji" (EX-B 2) of L5 and L6 in the EA group, with disperse-dense wave, 2 Hz/15 Hz in frequency and 1 mA in current intensity, 20 min a time, once a day, 1-day interval was taken after continuous 6-day intervention, for 4 weeks totally. Before and after modeling, as well as before and after intervention, the comprehensive response score was observed. After modeling and intervention, magnetic resonance imaging (MRI) was used to observe the signal intensity of intervertebral disc and cartilage endplate. After intervention, the morphology of chondrocytes of cartilage endplate was observed by HE staining; the positive expression of a disintegrin and metalloproteinase with thrombospondin motif-5 (ADAMTS5) and Aggrecan in the cartilage endplate was detected by immunohistochemistry; the levels of inflammatory factors i.e. interleukin-1β (1L-1β) and tumor necrosis factor-α (TNF-α) in the cartilage endplate were detected by ELISA; the protein expression of ADAMTS5, Aggrecan, matrix metalloproteinase-13 (MMP-13), IL-1β and TNF-α in the cartilage endplate was detected by Western blot. Compared with the sham operation group, in the model group, the comprehensive response score was decreased (P<0.01); L5/L6 intervertebral disc and the cancellous bones of endplate vertebral body showed low signal and unclear boundary; the chondrocytes of the cartilage endplate increased significantly, the cells were enlarged and hypertrophic, and the nuclei were wrinkled and clustered; the positive expression of ADAMTS5 as well as the levels of IL-1β and TNF-α were increased (P<0.01), while the positive expression of Aggrecan was decreased (P<0.01) in the cartilage endplate; the protein expression of ADAMTS5, MMP-13, IL-1β and TNF-α was increased (P<0.01), while that of Aggrecan was decreased (P<0.01) in the cartilage endplate. Compared with the model group, in the EA group, the comprehensive response score was increased (P<0.01); the signal of L5/L6 intervertebral disc and the cancellous bones of endplate vertebral body was enhanced; the chondrocytes of the cartilage endplate were reduced, the nuclei were slightly crumpled and scattered; the positive expression of ADAMTS5 as well as the levels of IL-1β and TNF-α were decreased (P<0.05, P<0.01), while the positive expression of Aggrecan was increased (P<0.01) in the cartilage endplate; the protein expression of ADAMTS5, MMP-13, IL-1β and TNF-α was decreased (P<0.05, P<0.01), while that of Aggrecan was increased (P<0.05) in the cartilage endplate. EA at "Jiaji" (EX-B 2) can delay the MC of cartilage endplate. The mechanism may be related to inhibiting the degradation of ECM of chondrocytes and the secretion of inflammatory factors, and repairing the degeneration of endplate cartilage.