Viscoelastic properties of chondrocytes isolated from normal and osteoarthritic rabbit knee cartilage

This study uses the micropipette aspiration techniquecoupled with a viscoelastic solid model to investigate the viscoelasticproperties of chondrocytes isolated from normal and osteoarthritic rabbitarticular cartilage. Rabbit osteoarthritic model obtained by anteriorcruciate ligament (ACL) transection is used to simulate the pathologicalevents associated with OA. The average grades for normal and osteoarthriticcartilages are found to be higher in the ACL transection joints than in normal joints(p<0.005). The experimental results show that the mean diameters ofchondrocytes from normal and OA cartilage are 14.85\pm 2.218\mum and14.38\pm1.909\mum, respectively, and are not significantly different(p>0.05), however, OA chondrocytes see a significantly lowerequilibrium modulus, instantaneous modulus and apparent viscosity(E_\infty =0.257\pm 0.091\,kPa, E_0=0.455\pm 0.182\,kPa,\mu =0.386\pm 0.136\,kPa\cdot s, n=67) compared with normal chondrocytes(E_\infty =0.366 \pm 0.07\,kPa, E_0=0.653\pm 0.095\,1\,kPa,\mu =6.360\pm 1.121\,kPa\cdot s, n=52) (p<0.000\,1). Theanalyses of correlation indicate no dependence of the viscoelasticparameters on the cell diameter or on the ratio of cell diameter tomicropipette diameter for cells from normal or OA chondrocytes(p>0.05) except for the equilibrium modulus (E_\infty ) of normal chondrocytes(p<0.05).