Alterations In Biomechanical Properties Of Chondrocytes Isolated From Normal And Osteoarthritic Rabbit Cartilage

Objective The mechanical environment of the chondrocyte is an important factor that influences the maintenance of the articular cartilage extracellular matrix, and the mechanical signals are believed to be significant factors in the initiation and progression of joint degeneration. The purpose of this study is to characterize the mechanical behavior of chondrocytes and to determine the biomechanical properties of chondrocytes isolated from Osteoarthritic and Non- osteoarthritic (Normal) cartilage.Methods Sixteen mature New Zealand white rabbits were divided into two groups randomly, each group 8. The animal model of OA was induced by anterior cruciate ligament transection(ACLT) in animals of experiment group ,and the same process of operation was performed on ones of control group, but no ACLT. After 20 weeks, rabbits were sacrificed and evaluated at two levels: macroscopic and histologic(HE) in all left knees. The micropipette aspiration combined with Half-space model was used to quantify changes in biomechanical properties of chondrocytes isolated from cartilage of right knees in two groups.Results The knee joints of experiment group had obvious degeneration of articular cartilage compared with control ones. The score of macroscopic and histologic evaluation of experiment group is significantly higher than control one (P<0.05).The mean diameter of chondrocytes from control and experiment group were 14.85±2.22μm and 14.38±1.91μm, respectively, and were not significantly different (P>0.05). No differences were found in the Young's moduli between control (0.57±0.43Kpa) and experiment chondrocytes (0.54±0.40Kpa) (P>0.05). There were significantly different (P<0.0001) in magnitude of this volume change between control (15.7%) and experiment (23.5%) chondrocytes after complete aspiration of the cell into the pipette. Specifically, control chondrocytes exhibited a significantly higher change than experiment ones in viscoelastic properties (P<0.0001). In response to a step pressure, chondrocytes exhibited viscoelastic solid creep behavior characterized initially by a jump in displacement followed by a monotonically decreasing rate of deformation that generally reached an equilibrium displacement.Conclusion In response to a step pressure, chondrocytes exhibited viscoelastic solid creep behavior. Except for the cell diameter and Young's moduli of chondrocytes, there were significantly alteration in the volume regulation capabilities and viscoelastic properties of chondrocytes with OA. These findings suggest that mechanical environment of the chondrocyte may be altered in osteoarthritic cartilage.