Cartilage Responses to a Novel Triaxial Mechanostimulatory Culture System

We have developed a novel mechanically active cartilage culture device capable of modulating the interplay between compression and shear, at physiologic stress levels (2-5 MPa). This triaxial compression culture system subjects cylindrical cartilage explants to pulsatile axial compression from platen contact, plus pulsatile radially transverse compression from external fluid compression. These compressive loads can be independently modulated to impose stress states that resemble normal physiologic loading, and to investigate perturbations of individual components of the multi-axial stress state, such as increased shear stress. Based on the observation that joint incongruity predisposes cartilage to premature degeneration, we hypothesized that cartilage extracellular matrix (ECM) synthesis would be inhibited under conditions of low transverse buttressing (high shear stress). To test this hypothesis, we compared ECM synthesis in human cartilage explants exposed to axial compression without transverse compression (high shear stress), versus explants exposed to axial compression plus an equal level of transverse compression (low shear stress). Both total (35)SO(4) incorporation and aggrecan-specific (35)SO(4) incorporation were significantly inhibited by axial compression, relative to axial plus transverse compression.