CD44 standard form (CD44H) expression and distribution in dysfunctional human temporomandibular joint discs

The expression pattern of the cell adhesion molecule CD44 standard form (CD 44H) in dysfunctional human temporomandibular joint (TMJ) discs was studied immunohistochemically and compared with normal disc pattern in order to ev aluate the expression of this adhesion molecule and correlate it to histopa thological changes. Immunohistochemistry with anti-CD44H antibodies was per formed on paraffin sections of pathological and normal discs. In normal TMJ discs, a moderate immunolabelling with anti-CD44H antibodies was detectabl e in fibroblastlike cells, in the few fibrochondrocytes and in chondrocytel ike cells. In dysfunctional discs, the staining pattern and intensity varie d according to the histopathological findings of the specimens. The TMJ dis cs showing abnormal collagen arrangement or fragmentation of collagen fibre s presented overall the same immunolabelling pattern of normal discs. In th e discs showing areas of fibrocartilaginous metaplasia, CD44H expression wa s upregulated in fibrochondrocytes and fibroblastlike cells. especially aro und the chondroid tissue. Overall. these results suggest that CD44H mediate s the binding of some ECM proteins in TMJ disc cells. The up-regulation of CD44H observed in some dysfunctional TMJ discs seems to indicate a preventi on of apoptosis in fibroblastlike cells and an important role in phenotypic al change of fibrochondrocytes into chondroblastlike cells, enabling the ag gregation of chondroid tissue pericellular matrix components.