抄録
Stress relaxation experiments were performed for articular cartilage (AC) specimens which were cultured in the medium (DMEM) containing collagenase and in the medium containing cellular fibronectin having an extra domain A (EDA(+)FN). For all the specimens measured, stress relaxation was divided into two processes: the process observed in the short time region (S-process) and that observed in the longer time region (L-process). Relaxation modulus of L-process was described by a simple exponential type function with single relaxation time, while the decay in S-process was more rapid than that of L-process and seemed to contain many relaxation times. In AC cultured with collagenase, S-process became dominant as compared with AC cultured in DMEM without collagenase nor EDA(+)FN (control). As type II collagen molecules in AC are destroyed by a collagenase digestion, S-process was regarded as the molecular-scale structural change in collagen fibrils. For AC cultured with EDA(+)FN, increase in modulus was observed as compared with the control system. This increase was considered as the collagen synthesis by chondrocytes activated by EDA(+)FN. A chronic existence of EDA(+)FN may break the homeostatic metabolism of AC matrix by chondrocytes, which can be a trigger of rheumatoid arthritis in AC.
