Effects of beta-D-xyloside on cultured embryonnic tooth germs

Objective: beta-D-xyloside inhibits the synthesis of proteoglycan(PG)-associated glycosaminoglycans (GAGs)and stimulates the synthesis of free chondroitin/dermatan sulfate. GAGs are cell-associated and matrix components in embryonnic tooth germs. However the role(s) of these components are poorely understood. Therefore the inhibitor was used to get some insights on their functions. Methods: First mandibular tooth germs were dissected out from day 18 embryos. They were cultured for 11 days in a semi-solid medium BCJb (Gibco) supplemented with 0.2, 2 or 5 mM beta-D-xyloside. As control, germs were grown in a xyloside- free medium or in a medium containing 2mM alpha-xyloside. After fixation and embedding sections of the germs were sudied by histochemistry and immunohistochemistry. Results: Cell proliferation , detected by PCNA staining, was detected at the tip of the cusps and in the dental follicule. It was altered in the beta -D-xyloside group in a dose-dependant way. Consequently, cusp morphogenesis was limitted in the 0.2 mM group, and almost suppressed in the 2mM group. 5mM was cytotoxic. Alcian blue staining at pH 1 was intense in the basement membrane, strong in the pulp and weak in the enamel organ. In the 2mM group, the staining was reinforced in the enamel organ and weak in the pulp. Similar changes were obserrved with 2B6 and antibody raised against CS/DS. No difference was detectable wit an antidecorine, whereas biglycan immunostaining was stronger in the 2mM group. Conclusions: During tooth morphogenesis, GAGs more than PGs control cell proliferation and consequently tooth morphogenesis. The shift between the embryonnic pulp and enamel organ needs further investigations.