[Effect of concanavalin A on morphology and DNA synthesis of resting chondrocyte cultures]

Rabbit chondrocytes were isolated from resting cartilage of ribs of 4-week-old New Zealand rabbits. Chondrocytes were seeded at low density and grown to confluency in medium (DME) with 10% fetal bovine serum, 50 micrograms/ml ascorbic acid, and antibiotics, at 37 degrees C under 5% CO2 in air, and then serum concentration was reduced to 0.3%. At the low serum concentration, chondrocytes adopted fibroblastic morphology. Addition of concanavalin A to the culture medium induced a morphologic alteration of the fibroblastic cells to polygonal or spherical chondrocytes that were surrounded by refractile matrix. Wheat germ agglutinin and garden pea lectin induced similar cell shape changes without any increase in matrix synthesis. Concanavalin A decreased [3H]thymidine incorporation into DNA in a dose-dependent manner with an ED50 of 0.4-1 micrograms/ml in the presence of various concentrations of serum ranging from 0.3 to 20%. The concanavalin A inhibition of DNA synthesis was abolished by 10 mmol/L methyl-D-mannopyranoside. The inhibition of chondrocyte proliferation does not seem to be specific to concanavalin A. Wheat germ agglutinin, lentil lectin, phytohemagglutinin, Ulex europeaus agglutinin, and garden pea lectin also decreased, dose-dependently, [3H]thymidine incorporation into DNA in chondrocytes. Other lectins at 0.01-20 micrograms/ml had little effect on [3H] thymidine incorporation. Because the molecular structure of concanavalin A and its mode of actions have been extensively characterized, chondrocytes exposed to this lectin will be useful as a novel model in studying of the control of cellular differentiation.