Biochemical and immunohistochemical studies of the protein expression and localization of decorin and biglycan in the temporomandibular joint disc of growing rats

To analyze the growth-related changes in extracellular matrix components, biochemical/immunohistochemical techniques were used to examine the protein expression and localization of two small leucine-rich proteoglycans, biglycan and decorin, in the temporomandibular joint discs of growing rats. Western blotting showed that the protein expression of decorin increased with age, but that of biglycan gradually decreased. An immunohistochemical study showed that staining for decorin was weak and homogeneously distributed in the discs from birth to 2 weeks. Regional differences in staining for decorin became prominent at 4, 8 and 16 weeks; decorin was more abundant in the peripheral area (the periphery of the band and the attachment) than in the central area (the intermediate zone and central area of the posterior band). In contrast, staining for biglycan was evenly distributed throughout the disc until 4 weeks, and after that became rather intense in the anterior and posterior bands. These results demonstrate that there are growth-related changes and regional differences in the expression of biglycan and decorin in the temporomandibular joint discs of growing rats, which probably reflect changes in the biomechanical environment caused by the development of orofacial functions.