MODULATION OF PROTEOGLYCAN COMPOSITION IN CULTURED ANATOMICALLY INTACT JOINT CARTILAGE BY CYCLIC LOADS OF VARIOUS MAGNITUDES

The anatomically intact articular cartilage (area approximate to 2.5 c m(2)) of 5-month-old bovine sesamoid bones was cyclically (0.3 Hz) loa ded with 0, 5, 25 and 50 kg in vitro for 7 days. The amount and compos ition of the proteoglycans that were synthesized during the last 17 ho urs of incubation under each regime were studied. Loads of all magnitu des produced a 45% overall increase in synthesis, which included a dis proportionate increase in the synthesis oi small proteoglycans, loadin g with either 25 or 50 kg induced the synthesis of much larger glycosa minoglycan side-chains and a species oi small proteoglycan rich in ker atan sulfate. Under these greater loads, synthesis in the deep layer o f the cartilage was reduced and there was focal damage to the cartilag e surface.