Effects of food consistency on expression of extracellular matrices in the temporo-mandibular joints

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To analyse the effects of food consistency on expression of extracellular matrix components in rat temporomandibular joint (TMJ), expression and localization of the core proteins of small reisin-rich proteoglycan and a large chondroitin sulphate proteoglycan, versican, in the TMJ discs during postnatal development (2 weeks to 32 weeks) were examined, using Western blotting, immunohistochemistry and rapid-cycle real-time RT-PCR. Western blotting analysis showed that protein expression was rapidly decreased after birth in biglycan, increased up to 16 weeks for decorin, and increased after birth, peaked at 8 weeks, and then gradually decreased for versican. An immunohistochemical study showed that staining for each proteoglycans was and homogeniously distributed in the TMJ discs at 2 weeks. The regional differences of the staining for became prominent after 4 weeks; the staining for 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. The staining for biglycan was preferentially localized in the posterior band, on which compressive force would be exerted. mRNA expression was peak after birth and gradually decreased with growing. These results demonstrate that the growth-related changes and regional differences exist in the expression of versican 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.