Clarification of the Mechanisms that Causes Internal Derangement of the Temporomandibular Joint

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To analyse the effects of mechanical environments on gene and protein expressions of major extracellular matrix components in rat temporomandibular joint (TMJ), expression and localization of the core proteins of proteoglycans in the TMJ discs during postnatal development were examined, using Western blotting, immunohistochemistry and rapid-cycle real-time RT-PCR (Real-time Polymerase Chain Reaction). The obtained results were followings; 1. Quantitative RT-PCR showed that mRNA expressions of biglycan and versican were peak after birth and gradually decreased with growing, while decorin mRNA increased with growing. 2. Among four versican isoforms, V0, V1 and V3 decreased with growing, while V2 peaked at 8 weeks and then gradually decreased.3. Western blotting showed that mRNA expression of rapidly decreased with growing, while mRNA of decorin increased. 4. An immunohistochemical study showed that biglycan was evenly distributed in the TMJ dsics throughout the growing stage. In contrast; localization of decorin and versican showed the regional differences; the stainingfor decorin and biglycan was weak in the central part of the discs and intense in the anterior and posterior peripheral attachments, which would mainly experience tensile forces. These results demonstrate that the growth-related changes and regional differences exist in the expression of proteoglycans in the TMJ discs of growing rats, which probably reflect the alteration of biomechanical environments caused by development of orofacial functions. Further study concerning the effects of food consistency would be necessary to understand mechanisms of temporomandibular joint diseases (TMD)s.