Alteration of Cartilage Compressive Properties When Exposed to Calcium

Pseudogout is a form of arthritis that causes pain, stiffness, tenderness, and swelling of the joints. It results from the abnormal formation of calcium pyrophosphate (CPP) crystals in articular cartilage, which is later followed by the release of crystals into the synovial fluid. The cause of abnormal deposits of CPP crystals in cartilage is unknown but may be associated with abnormal levels of Ca²⁺ ions in the joint fluid. It is possible that calcium is attracted into cartilage via a physiochemical mechanism, where it effectively neutralizes and precipitates the polyanionic glycosaminoglycans (GAG) of cartilage, in turn reducing its compressive stiffness. The purpose of this study is to determine whether cartilage adsorbs calcium and whether this results in the alteration of cartilage compressive properties in a dose-dependent manner. Samples of adult bovine articular cartilage from the femoral condyles will be treated with calcium and tested in static and dynamic compression before and after treatment to determine the compressive stiffness of the tissue. The tissue and spent treatment solutions will be assayed for calcium content using an o-Cresophthalein Complexone (CPC) assay and for GAG content using a DMMB assay. It is expected that the change in cartilage compressive stiffness will be inversely proportional to the up-take of calcium by the cartilage tissue. Increased calcium in the joint fluid in disease states, such as pseudogout, or following an injury may result in the loss of cartilage compressive stiffness and cartilage deterioration but may be amenable to a chelation therapy.