Alpha and epsilon isozymes of protein kinase C in the chondrocytes in normal and early osteoarthritic articular cartilage.

Protein kinase C (PKC) isozymes (alpha, beta I, beta II, gamma and, epsilon-PKC) were examined immunocytochemically in control and mechanically induced osteoarthritic knee joints in rats. beta I, beta II, and gamma PKC-positive cells were not observed in sham-operated or osteoarthritic knee joints. alpha-PKC, which was observed only in the cells in the subchondral bony layer in the controls, appeared in the chondrocytes in the superficial and columnar layers of the osteoarthritic knees. epsilon-PKC was observed in the control chondrocytes in the superficial portion of the columnar layers. In early osteoarthritic joints, however, epsilon-PKC-positive chondrocytes disappeared from the superficial portion of columnar layer and increased in number in the middle columnar layers. The appearance and changes in distribution of these PKC-positive chondrocytes, either under normal or osteoarthritic conditions, have not been reported previously. The role of the redistribution of PKC isozymes is still unclear as to whether they are involved in initiating destructive processes, reflect attempted cell repair mechanisms, or are simply a consequence of the cellular changes.