| Objective:Knee osteoarthritis(KOA)is the most common chronic,progressive and degenerative joint disease.Whole body vibration(WBV)can transmit mechanical vibration to the whole body,stimulate the activity and excitability of nerve,muscle and bone,and is gradually applied to the clinical treatment of KOA.Interleukin-1?(IL-1?)and Matrix metalloproteinase 13(MMP-13)are important factors in articular cartilage degeneration of knee joint.Hypoxia inducible factor-2?(HIF-2?)is the catabolic regulator of articular cartilage,and Collagen type ? alpha 1 gene(COL2A1)is the main anabolic factor of articular cartilage.The purpose of this study is to investigate the effect of different frequencies of WBV on KOA articular cartilage and the expression of HIF-2? related factors in SD rats at early stage,and to provide theoretical evidence for KOA new therapeutic target clinically.Methods:64 8-week-old male SD rats were selected in this study,and 16 rats were randomly selected as normal control group(NC group).The remaining 48 rats were injected with 2%papain solution and 0.03 mmol/L L-cysteine into the left and right knee cavities.After 6 weeks,early KOA models were established.The cartilage samples of 8 rats in the normal group and the model group were stained with safranin O for histological observation and scoring to check whether the model was successfully established.40 rats in the model group were randomly divided into 5 groups with 8 rats in each group.WBV intervention(NC group,0Hz),model group(SC group,0Hz),high frequency group 1(HV1 group,60Hz),high frequency group 2(HV2 group,40Hz),medium frequency group(MV group,20Hz)and low frequency group(LV group,10Hz)were performed for 40min per time,5 days per week.After 8 weeks of intervention,the samples were taken for the following analysis:(1)safranine O staining,histological observation of articular cartilage and Modified Mankin score;(2)mRNA expression levels of IL-1?,HIF-2?,MMP-13 and COL2A1 were detected by RT-qPCR.(3)protein expression levels of IL-1?,HIF-2?,MMP-13 and COL2A1 were detected by Western blot.All data are presented as means ± standard deviation.Statistical analysis was done using SPSS 20.0.Results:1.Model identification:Histological observation showed that compared with NC group,the cartilage surface of SC group was uneven,cracked and damaged,the cartilage was degenerated.Modified Mankin Score showed that the score of SC group was higher than that of NC group significantly(P<0.001).2.Impact of WBV intervention:(1)Histological observation and Modified Mankin Score showed that:Compared with NC group,SC group has denudation of cartilage surface and obvious thinning of cartilage layer.Cartilage degeneration in other vibration groups was improved in varying degree,especially in lower frequency group.Modified Mankin Score of the other group was significantly higher than NC group(P<0.001);HV2,MV and LV group were significantly lower than SC and HV1 group(P<0.001).MV and LV group were significantly lower than HV2 group(P<0.001).LV group was significantly lower than MV group(P=0.006).(2)RT-qPCR results show that:? IL-1?:SC,HV1,HV2,MV group were significantly higher than NC group(P<0.001),LV group was significantly higher than NC group(P=0.015);HV1,HV2,MV and LV group were significantly lower than SC group(P<0.001).HV2,MV and LV group were significantly lower than HV1 group(P<0.001).LV group was significantly lower than HV2 group(P<0.001)and MV group(P=0.008).? HIF-2?:SC,HV1,HV2,MV group were significantly higher than NC group(P<0.001);HV1,HV2,MV and LV group were significantly lower than SC group(P<0.001).MV and LV group were significantly lower than HV1 group(P<0.001).LV group was significantly lower than HV2 and MV group(P<0.001).?MMP-13:SC,HV1,HV2,MV group were significantly higher than NC group(P<0.001).HV1,HV2,MV and LV group were significantly lower than SC group(P<0.001).HV2,MV and LV group were significantly lower than HV1 group(P<0.001).MV and LV group were significantly lower than HV2 group(P<0.001).LV group was significantly lower than MV group(P=0.023).?COL2A1:SC,HV1,HV2,MV,LV group were significantly lower than NC group(P<0.001).HV2 group was significantly higher than SC group(P=0.012),MV and LV group were significantly higher than SC and HV1 group(P<0.001).MV group was significantly higher than HV2 group(P=0.016),LV group was significantly higher than HV2 and MV group(P<0.001).(3)Western Blot results showed that:? IL-1?:SC,HV1,HV2,MV group were significantly higher than NC group(P<0.001);HV1,HV2,MV and LV group were significantly lower than SC group(P<0.001).HV2,MV and LV group were significantly lower than HV1 group(P<0.001).LV group was significantly lower than HV2 and MV group(P<0.001).? HIF-2?:SC,HV1,HV2 and MV group were significantly higher than NC group(P<0.001),LV group was significantly higher than NC group(P=0.018);HV1,HV2,MV and LV group were significantly lower than SC group(P<0.001).HV2,MV and LV group were significantly lower than HV1 group(P<0.001).MV group was significantly lower than HV2 group(P=0.011);LV group was significantly lower than HV2 and MV group(P<0.001).? MMP-13:SC,HV1,HV2,MV group were significantly higher than NC group(P<0.001),LV group was significantly higher than NC group(P=0.046);HV1,HV2,MV and LV group were significantly lower than SC group(P<0.001).HV2,MV and LV group were significantly lower than HV1 group(P<0.001).LV group was significantly lower than HV2 and MV group(P<0.001).?COL2A1:SC,HV1,HV2,MV,LV group were significantly lower than NC group(P<0.001).HV1,HV2,MV and LV group were significantly higher than SC group(P<0.001).HV2,MV and LV group were significantly higher than HV1 group(P<0.001).MV group was significantly higher than HV2 group(P=0.002);LV group was significantly higher than HV2 and MV group(P<0.001).Conclusion:(1)Different frequencies of WBV have different effects on knee cartilage and expression of HIF-2? related factors in early KOA.(2)Lower frequency of WBV can reduce the expression of inflammatory factor IL-1?,hypoxia inducible factor HIF-2?,catabolic factor MMP-13 and increase the expression of anabolic factor COL2A1,suggesting that lower frequency of WBV has the beneficial effect of improving degeneration of articular cartilage significantly.(3)HIF-2? may be the target of WBV intervention in early KOA. |
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