Cellular S-100 protein immunostaining in human dysfunctional temporomandibular joint discs

S-100 protein was detected immunohistochemically in diseased human temporom andibular joint discs with different degrees of pathology, and the findings compared with those of normal discs. In normal discs, large nerve trunks i n the posterior ligament were strongly stained by anti-S-100 antiserum; the very few chondrocyte-like cells sometimes showed faint staining, while no staining was observed in any fibrochondrocyte-like or fibroblast-like cell. In dysfunctional discs, S-100 protein immunostaining seemed to correlate w ith structural pathological findings. The discs showing an abnormal collage n arrangement or fragmentation of collagen fibres presented overall the sam e immunolabelling pattern as normal discs. In discs with fibrocartilaginous metaplasia and dystrophic cartilage formation, fibrochondrocyte cells show ed a very strong immunoreaction for S-100 protein and fibroblast-like cells in some instances were also positive. These findings suggest that S-100 up regulation in disc cells can be considered an attempt at tissue repair by c hondroid metaplasia following an injury in that it enables fibroblast-like cells and fibrochondrocytes to acquire a chondrogenic phenotype. (C) 2000 E lsevier Science Ltd, All rights reserved.