The effects of age on viscoelasticity and deformation recovery of articular chondrocytes

The aim of this study was to characterize the age-relatedchanges of viscoelastic properties and deformation recovery of rabbitchondrocytes in natural development of articular cartilage. The micropipetteaspiration combined with a standard linear viscoelastic solid model was usedto quantify all parameters of chondrocytes from different age groups.Results indicate that the viscoelastic properties of chondrocytes in oldgroup exhibited a significantly lower instantaneous modulus (E_0),equilibrium modulus (E_\infty ), and apparent viscosity (\mu )compared withthose of young group (p<0.005) and adult group (p<0.005). But no differenceswere found between young and adult group (p>0.1). The process of creep anddeformation recovery of chondrocytes has changed significantly duringnatural development. The time t_E that old chondrocytes need to reach equilibrium is significantlyless than young and adult ones (p<0.05), but no differences were foundbetween young and adult ones (p>0.05). At the same time, maximal creep displacementL_M in old group dramatically higher than young and adult group(p<0.005), however, there were no differences between young and adult group(p>0.05).Comparisons of the deformation recovery ratio ofdifferent age groups before 8 seconds have shown that the ratio value ofyoung group is significantly higher than those of adult and old ones(p<0.005), and there were no significant difference between adult and oldones (p>0.05). Additionally, there were no significant correlation betweenthe viscoelastic parameters and the ratio of the cell to micropipette diameter.These results may be helpful for chondrocyte-based cartilage tissueengineering.