AN IMMUNOHISTOCHEMICAL STUDY OF REGIONAL DIFFERENCES IN THE DISTRIBUTION OF TYPE-I AND TYPE-II COLLAGENS IN RAT MANDIBULAR CONDYLAR CARTILAGE

The mammalian temporomandibular joint is a highly specialized diarthro dial joint under multidirectional compressive and tensile forces. In s uch a complicated biomechanical environment, the phenotypic expression of extracellular matrix may vary in different regions of the mandibul ar condylar cartilage. To test this hypothesis, immunohistochemical te chniques were used to examine the localization of type I and type II c ollagens in various anterioposterior regions of the condylar cartilage of 4-week-old rats. In the posterosuperior region, which is mainly su bjected to compressive forces, a strong reaction for type II collagen was observed in the cartilaginous layer (maturative and hypertrophic c ell layers), and a rather weak reaction was observed for type I collag en in the precartilaginous and cartilaginous layers, compared with the reactions in other peripheral regions. Proceeding anteriorly, stainin g for type I collagen increased, while that for type II collagen decre ased. In posteroinferior cartilage, which is subjected mainly to tensi le forces because of its direct attachment to the retrodiscal pad, sta ining for type I collagen was strong, and that for type II collagen wa s faint in the cartilaginous layer. These results demonstrate that mar ked regional differences exist in the phenotypic expression of two maj or collagen components in mandibular condylar cartilage, which may ref lect the local functional environment and cellular response. Copyright (C) 1996 Published by Elsevier Science Ltd.