Low-frequency electrical stimulation of quadriceps femoris and hip abductor muscle group against knee osteo-arthritis:an experimental study
Objective:To observe the outcomes of low-frequency electrical stimulation(LFES)of quadriceps femoris(QF)and hip ab-ductor muscle group against knee osteoarthritis(KO A)in rats,and to explore its underlying mechanism.Methods:Forty 2-month-old Spra-gue-Dawley(SD)rats were randomized into normal control group,model group,QF LFES group and combined QF LFES group,10 ones in each group.All rats but the ones in normal control group were intervened by knee intra-articular injection of a mixture of 4％papain solu-tion and 0.03 mol/L L-cysteine solution in a ratio of 2∶1(0.15 mL)into the right knees on day 1,4 and 7 after the beginning of the model-ing for inducing KO A.After successful modeling,the rats in QF LFES group and combined QF LFES group received LFES on the right QF as well as QF and hip abductor muscle group(especially the gluteus medius),respectively,once every other day,20 minutes at a time for consecutive 28 days;while the ones in model group and normal control group were not given any intervention.On day 2 after the end of in-tervention,the blood(2 mL)was drawn from the inferior vena cava(IVC)of rats in each group,and the serum levels of interleukin(IL)-1 βand matrix metalloproteinase(MMP)-13 were detected by using enzyme linked immunosorbent assay(ELISA).After phlebotomizing,the rats were sacrificed,and their distal femoral cartilage tissues were harvested and stained with hematoxylin-eosin(HE),toluidine blue and modified safranin O-fast green(SO-FG)for observing the histopathological changes;meanwhile,the knee articular cartilage injury was evalu-ated by using Mankin score.Furthermore,the expression level of MMP-13 in the knee cartilage tissues were detected by using immunohisto-chemical staining.Results:①Compared with that of normal control group,the histopathological changes,manifesting as decreased and disor-dered arranged chondrocytes,reduced cartilage matrix with obviously uneven staining,thinned cartilage layer,and the unclear tidal line,were observed in the knee cartilage tissues of rats in model group;while,the rats in QF LFES group and combined QF LFES group presented with increased and neatly arranged chondrocytes,uniformly stained cartilage matrix,thickened cartilage layer and clear tidal lines,with combined QF LFES group performed more pronounced.②The Mankin score of the knee cartilage was higher in model group,QF LFES group and com-bined QF LFES group compared to normal control group(P=0.000,P=0.000,P=0.000),and was higher in model group and QF LFES group compared to combined QF LFES group(P=0.000,P=0.000),and was highest in model group(P=0.000).③The serum levels of IL-1 β and MMP-13 were higher in model group,QF LFES group and combined QF LFES group compared to normal control group(P=0.000,P=0.000,P=0.000;P=0.000,P=0.000,P=0.000),and was higher in model group and QF LFES group compared to com-bined QF LFES group(P=0.000,P=0.000;P=0.000,P=0.000),and was highest in model group(P=0.000,P=0.000).④The MMP-13-positive cells accounted for a higher proportion in the knee cartilage tissues of rats in model group,QF LFES group and combined QF LFES group compared to normal control group(P=0.000,P=0.000,P=0.000),and a higher proportion in model group and QF LFES group compared to combined QF LFES group(P=0.000,P=0.000),and a highest proportion in model group(P=0.000).Conclusion:LFES of QF and hip abductor muscle group can promote the repair of knee cartilage injury in KO A rats.It may exert the effects by reducing the serum levels of IL-1 β and MMP-13 and inhibiting the expression of MMP-13 in knee cartilage of KOA rats.
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