ABSTRACT
<p><b>OBJECTIVE</b>To observe the effects of close-to-bone needing combined with electroacupuncture (EA) on cartilage collagen type Ⅱ/discoidin domain receptor/matrix metalloproteinase 13 (collagen type Ⅱ/DDR2/MMP 13) signaling pathway in rabbits with knee osteoarthritis (KOA), and to explore the possible action mechanism of this method on repair of extracellular matrix of knee cartilage.</p><p><b>METHODS</b>Forty New Zealand white rabbits were randomly assigned into a normal group (10 rabbits) and a model establishing group (30 rabbits). The Hulth-Telhag technique was applied to establish the model of KOA, and X-ray was used for outcome assessment. The rabbits with successful modeling were randomly assigned into a model group, a close-to-bone needing group, a regular acupuncture group, 10 rabbits in each one. The rabbits in the close-to-bone needing group were treated with close-to-bone needing and EA; the rabbits in the regular acupuncture group were treated with regular acupuncture and EA. "Neixiyan" (EX-LE 4), "Dubi" (ST 35), "Yinlingquan" (SP 9), "Zusanli" (ST 36) and "Liangqiu" (ST 34) were selected in the two groups. The intervention was given for 20 min, once a day; the intervention of 5 days made 1 session, 2 days as the interval and totally 4 sessions were given. Rabbits in normal and model group were immobilized without any treatment. After the treatment, western blotting method was applied to evaluate the expression of DDR2 and collagen type Ⅱ; the activity of collagen type Ⅱ, DDR2 and MMP 13 was assessed by immunohistochemistry method; the mRNA expression of DDR2 and MMP 13 was determined by reverse transcription-polymerase chain reaction (RT-PCR).</p><p><b>RESULTS</b>Compared with the normal group, the activity expression of collagen type Ⅱ were significantly reduced in the other groups (all<0.01),while the activity and mRNA expression of DDR2 and MMP 13 were notably increased (all<0.01). Compared with the model group, the activity expression of collagen type Ⅱ in the close-to-bone needing group and regular acupuncture group were increased (all<0.01), while the activity and mRNA expression of DDR2 and MMP 13 were reduced (all<0.01). Compared with the regular acupuncture group, the activity and mRNA expression of MMP 13 and DDR2 in the close-to-bone needing group were reduced (all<0.01), while the activity expression of collagen type Ⅱ were increased (<0.01).</p><p><b>CONCLUSIONS</b>The close-to-bone needing combined with EA and regular EA could both promote the repair of knee cartilage, where closing-to-bone needing combined with EA shows a superior efficacy. The mechanism may be associated with the blocking effect of collagen type Ⅱ/DDR2/MMP13 signaling pathway and the inhibiting effect of degradation in extracellular matrix of cartilage.</p>
ABSTRACT
BACKGROUND: Reactive Oxygen species have been known to be a key factor to promote atherosclerosis. DDR2(Discoidin Domain Receptor 2) is a cell surface receptor tyrosine kinase which is activated by fiber collagen. Recently, DDR2 was suggested to be involved in activation of smooth muscle cell in blood vessel of atherosclerosis. METHODS: The effect of antioxidant, N-acetyl cysteine and H2O2(Hydrogen peroxide) in the activation of DDR2 by collagen was studied using HEK293 cells expressing DDR2. The direct activation of DDR2 tyrosine kinase domain by tyrosine phosphorylation upon the treatment of H2O2 was analysed after the kinase domain was expressed in sf9 cells. RESULTS: H2O2 enhanced DDR2 auto-phosphorylation and its cellular signaling to induce MMP-1 expression. However N-acetyl cysteine suppressed the DDR2 activation. The reactive oxygen induced tyrosine phosphorylation in DDR2 tyrosine kinase domain to activate its tyrosine kinase activity. CONCLUSIONS: DDR2 activity can be up-regulated by oxidative stress and this provides a mechanism that DDR2 plays a critical role when reactive oxygen species promote atherosclerosis. Therefore inhibition of the activated DDR2 could be a new therapeutic strategy for atherosclerosis.