Static compression is associated with decreased diffusivity of dextrans incartilage explants

The chondrocytes of adult articular cartilage rely upon transport phenomena within their avascular extracellular matrix for many biological activities . Therefore, changes in matrix structure which influence cytokine transport parameters may be an important mechanism involved in the chondrocyte respo nse to tissue compression. With this hypothesis in mind, partitioning and d iffusion of 3-, 10-, and 40-kDa dextrans conjugated to tetramethylrhodamine , and 430-Da tetramethylrhodamine itself, mere measured within statically c ompressed bovine articular cartilage explants using a novel experimental ap paratus and desorption fluorescence method. Partitioning and diffusion were examined as functions of solute molecular weight and matrix proteoglycan d ensity, and diffusion was measured versus static compression up to 35% volu metric strain. In general, partition coefficients and diffusivities were fo und to decrease with increasing solute molecular weight. In addition, for a given solute, diffusivities decreased significantly with increasing static compression. Results therefore suggest a possible role for transport limit ations of relatively large molecular weight solutes within the extracellula r matrix in mediating the biological response of chondrocytes to cartilage compression. (C) 2000 Academic Press.