Rh. Ostendorf et al., IRREVERSIBLE CHANGES IN GLYCOSAMINOGLYCAN COMPOSITION OF ANATOMICALLYINTACT BOVINE ARTICULAR-CARTILAGE INDUCED BY INTERMITTENT LOADING, Connective tissue research, 31(3), 1995, pp. 245-251
The changes in matrix composition induced by 1 MPa intermittent (0.2 H
z) loading of anatomically intact bovine articular cartilage in vitro
are studied. The kinetics of chondrocyte response was determined in ex
periments where sesamoid bones of adult cows were loaded for 0, 3, 5 a
nd 7 days. The reversibility of the induced changes were studied in se
samoid bones that were loaded for 5 days and subsequently cultured wit
hout loading for another 1, 2 and 3 weeks. Water content was not affec
ted by loading, nor by subsequent unloaded culture. Glycosaminoglycan
content was not affected by loading. nor by subsequent unloaded cultur
e for another 2 weeks. However, after 3 weeks of culture following 5 d
ays of loading, a significant decrease in glycosaminoglycan content wa
s found. Glycosaminoglycan synthesis was already increased after 3 day
s of loading. Loading for longer periods (5 and 7 days) further increa
sed the glycosaminoglycan synthesis rate. Glycosaminoglycan synthesis
decreased during the first week of subsequent culture without loading.
In the third week it dropped to a lower level than observed for the c
ontrol. The amount of 3-B-3(-) epitope was increased and the length of
newly synthesized glycosaminoglycans was decreased by intermittent lo
ading. Subsequent unloaded culture did not further increase the amount
of 3-B-3(-) epitope. However, after 3 weeks of unloaded culture the n
ewly synthesized glycosaminoglycans were as long as those synthesized
in the control. The results suggest that the changes in glycosaminogly
can chain length were reversible. However, the overall chondrocyte res
ponse to our loading regime seems to be detrimental to the tissue: exp
ression of 3-B-3(-) epitope induced by loading together with the drop
in glycosaminoglycan content and synthesis observed at the end of the
total culture period indicate that the cartilage is irreversibly damag
ed.