Osmotic Swelling Responses are Conserved Across Cartilaginous Tissues with Varied Sulfated-Glycosaminoglycan Contents

The interactions between the negatively charged sulfated glycosaminoglycan (sGAG) chains and the ionic interstitial fluid in articular cartilage and meniscal fibrocartilage give rise to an osmotic swelling stress that is critical for the load-bearing capability of both tissues. This osmotic swelling stress is altered when the sGAG content is changed, as during progression of degenerative joint disease; understanding the influence of sGAG concentration on the osmotic swelling stress of cartilage and meniscus is important to enhance our understanding of physiology and disease. This study compared the effect of altered osmotic environments on the confined compression swelling behavior of bovine tissues spanning a range of sGAG concentrations: juvenile articular cartilage, juvenile and adult meniscus, and juvenile cartilage degraded to reduce sGAG content. The transient response to changes in bath conditions was evaluated for explants assigned to one of three compressive offsets (5%, 10%, or 15% strain) and one of three bath conditions (0.1X, 1X, or 10X Phosphate Buffered Saline). Our results show that relative responses to alterations to the osmotic environment are consistent across tissue types, demonstrating that the role of sGAG in the swelling properties of the tissues tested is conserved, even when sGAG is present at low concentrations. Additionally, this study found unexpected correlations across tissue types between sGAG and collagen contents and between the aggregate modulus and both sGAG and collagen contents. These results suggest some conservation of composition-function relationships across a range of tissue types.