Confocal analysis of local and cellular strains in chondrocyte-agarose constructs subjected to mechanical shear.

Although numerous previous studies have investigated cell deformation and mechanotransduction within isolated chondrocytes compressed in agarose gel, no published studies have examined the cellular response to shear. In the present study, a novel experimental system has been used to apply precise magnitudes of simple shear strain to isolated bovine articular chondrocytes seeded in agarose. Specimens were gelled between porous endplates which enabled the specimen to be gripped within a specially designed test rig mounted on an inverted microscope. Confocal imaging of individual chondrocytes was used to determine the local and cellular shear strains at gross static shear strains up to 15%. The central region of the specimens experienced uniform local shear strain equal to the applied gross shear strain. An image analysis technique was developed to quantify the level of cell shear strain based upon the shear-induced rotation of a best-fit ellipse. Cell deformation occurred such that the magnitude of the cellular shear strain was equal to gross shear strain. This study is the first to describe the deformation of isolated articular chondrocytes subjected to shear strain. This validated experimental system will enable future studies to examine the influence of shear on chondrocyte function and the associated mechanotransduction signalling pathways.