Effect Of Low Intensity Pulsed Ultrasound On The Apoptosis Of Chondrocytes In Rabbit Knee Osteoarthritis By PI3K / Akt Chemical Conduction Pathway

Objective: To investigate the effects of low intensity pulsed ultrasound(LIPUS) on the ECM production and apoptosis of rabbit osteoarthritis(OA) chondrocytes via PI3K/Akt mechanochemical transduction pathyway.Methods: Of the thirty healthy New Zealand white rabbits selected for the study, twenty-four received knee anterior cruciate ligament transection to model OA, the remaining six rabbits served as normal controls. At the 4 th weeks after modeling the rabbits were sacrificed and pathologic changes of articular surface of femoral condyles were assessed; chondrocytes were isolated and cultured in vitro. All the cultured cells were randomly divided into five groups: a normal control group(NC), an OA model group(OA), an OA model plus LIPUS group(OA+L), an OA model plus LY294002 group(OA+LY), an OA model plus LY294002 and LIPUS group(OA+LY+L). OA+L is stimulated by LIPUS for six days(40 mW/cm2,20min/d), OA+LY group is treated with PI3K/Akt inhibitors LY294002, OA+L+LY group is treated with LIPUS and PI3K/Akt inhibitors LY294002 simultaneously, NC and OA groups were treated in the same way without LIPUS and LY294002 stimulation. Cells were collected after six days and the chondrocytes apoptosis were detected by flow cytometric assay, The expression of type II collagen, aggrecan, MMP-13, Akt, pAkt, Bcl-2, P53 were detected by Western blotting.Results: Compared with the NC group, the chondrocyte was excessive apoptosis in the OA group(P<0.05); As compared with the OA group, the chondrocyte apoptosis was significantly decreased in the OA+L group(P<0.05) and significatly increased in the OA+LY group(P<0.05), but has no significant difference in the OA+LY+L group(P>0.05), while it showed significant difference between OA+L group and OA+LY group(P<0.05). Compared with the NC group, the expression of type II collagen, aggrecan, pAkt and Bcl-2 were lower, but that of MMP-13, P53 were higher in the OA group(P<0.05). Compared with the OA group, the expression of type II collagen, aggrecan, pAkt and Bcl-2 were higher, but MMP-13, P53 were lower in the OA+L group(P<0.05); the expression of type II collagen, aggrecan, pAkt and Bcl-2 were lower, but that of MMP-13, P53 were higher in the OA+LY group(P<0.05); the expression of type II collagen, aggrecan, MMP-13, pAkt, P53, Bcl-2 were no difference in the OA+LY+L group(P>0.05), while in comparisons with OA+L group and OA+LY group the expression of these protein indicators were significantly difference(P<0.05).The expression of Akt were no difference in all groups(P>0.05).Conclusions: LIPUS decrease the apoptosis of OA chondrocytes, inhibit the expression of MMP-13 and degration of type II collagen and aggrecan via PI3K/Akt pathway, the underlying mechanisms are closely related to upregulation of Bcl-2 expression and downregulation of P53 expression. LIPUS can accelerate the recovery of cartilage for the purpose of treatment of OA.