In vitro protection of the articular surface by cross-linking agents.

The effects of cross-linking agents on the resistance of the articular surface to digestion with clostridial collagenase were studied using a described in vitro system. Mouse femoral heads were treated with various concentrations of glutaraldehyde, with osmium tetraoxide and with dithiobis (succinimydil propionate), digested with the enzyme, labeled with cationized ferritin and examined by electron microscopy. Collagenase alone caused disruption of the articular surface with penetration of the large marker into the cartilage matrix. After treatment of the femoral heads with the cross-linking agents, no effects on the morphology and on the labeling of the articular surface and no penetration of the label into the cartilage matrix were observed. Increasing cross-linking at the articular surface might be a new route for therapeutic intervention. However, experiments would be needed to assess the effect of the procedure on the viability and nutrition of chondrocytes and on the functional properties of the tissue.