Immunolocalization of gelatinase-A (matrix metalloproteinase-2) in damagedhuman temporomandibular joint discs

The fibrous tissue of the articular disc of the dysfunctional temporomandib ular joint undergoes deep and variable structural modifications. Here the c oncurrence of morphological changes and the expression of matrix metallopro teinase-2 (MMP-7) in damaged discs from individuals suffering joint dysfunc tion was investigated. Microscopic, ultrastructural and immunocytochemical investigations were made on variously damaged articular discs and on one co ntrol sample. Disaggregation of collagen fibres, an increase in cellular co mponents and calcification of large areas of tissue were observed in the da maged discs. These modifications were accompanied by a positive immunoreact ion pattern for MMP-2. Fibroblast-, chondroblast- and osteoblast-like cells displayed a positive cytoplasmic reaction. In samples displaying evidence of synovial hyperplasia, some cells of the synovial protrusions were MMP-2 immunoreactive. No MMP-2 staining was observed in the control sample. These findings demonstrate that structural modifications of the articular disc c ould be specific responses to changes in the function of the temporomandibu lar joint. Variations in extrinsic stimuli may activate intrinsic factors, such as MMPs, that induce structural modifications in the discal tissue. (C ) 1999 Elsevier Science Ltd. All rights reserved.