THE PROTEOGLYCAN METABOLISM OF MATURE BOVINE ARTICULAR-CARTILAGE EXPLANTS SUPERIMPOSED TO CONTINUOUSLY APPLIED CYCLIC MECHANICAL LOADING

This study describes the effect of load magnitude, frequency and durat ion on proteoglycan (PG) biosynthesis and loss in mature bovine articu lar cartilage explants. Cultured full thickness cartilage discs were s ubjected to a continuously applied, uniaxial compressive cyclic load. The loads were applied using a sinusoidal waveform of 0.001, 0.01, 0.1 or 0.5 Hz-frequency and a peak, stress of 0.1, 1.0, 2.5, or 5.0 MPa f or a period of 1, 3 or 6 days. Increasing the load magnitude, as well as the duration of loading, reduced the PG biosynthesis. Reducing the load frequency abolished the inhibitory effect of a given load magnitu de on PG biosynthesis, even though explants mere more compressed. Incr easing the load magnitude stimulated the release of newly synthesized PGs from explants, whereas an elevated duration of loading significant ly decreased the release of endogenous PGs. Explants loaded for 1 or 3 days were viable as determined biochemically, whereas 6 days of loadi ng resulted in a slightly diminished viability of explants. This study demonstrates that the duration and intensity of loading influences th e inhibition of PG biosynthesis, while PG loss is only modulated by th e magnitude and duration of loading. (C) 1997 Academic Press.