Measurement of the deformation of isolated chondrocytes in agarose subjected to cyclic compression.

Mechanically induced cell deformation is one of a number of possible mechanotransduction pathways by which chondrocytes sense and respond to changes in their mechanical environment. The present study describes a system for measuring the deformation of isolated chondrocytes in agarose during both static and cyclic compression. A test rig mounted on the stage of an inverted microscope was used to apply precise levels of compressive strain to individual cell-agarose constructs bathed in culture medium. Images of the cells were recorded using a CCD video camera attached to the microscope. Cell deformation was quantified in terms of a deformation index (X/Y) representing the ratio of cell diameters measured parallel (X) and perpendicular (Y) to the axis of compression. Cyclic compression between 0 and 15% strain, at 0.3 Hz, resulted in cyclic deformation of the cells at the same frequency. However, during the unstrained phase the cells did not fully recover to their initially spherical morphology (X/Y = 1.0). During the strained phase, the level of deformation (X/Y = 0.59) was initially similar to that observed during static 15% strain. However, this level of cell deformation reduced over a 20 min period of cyclic compression (X/Y = 0.72), although during static compression the cell deformation remained constant. This system may be used to examine cellular events under a range of dynamic mechanical stimuli.