Effects of beta-D-xyloside on morphogenesis and cytodifferentiation in cultured embryonic mouse molars.

Embryonic mouse molars were grown on a semi-solid medium supplemented with 2 mM beta-D-xylopyranoside (beta-xyloside), a specific inhibitor of proteoglycan synthesis. The induced glycosaminoglycan depletion in the extracellular matrix was monitored by immunohistochemistry employing monoclonal antibodies to chondroitin 4- and chondroitin 6-sulfates. beta-Xyloside inhibited formation of the dental bell and delayed the appearance of the first odontoblasts. Odontoblast functional differentiation proceeded in the absence of chondroitin sulfate in the basement membrane. Predentin secreted in the presence of beta-xyloside triggered the polarization of ameloblasts, but did not allow the maintenance of polarized odontoblasts. These results support the hypothesis that, in the tooth germ, chondroitin sulfate proteoglycans participate in the regulation of cell kinetic-dependent morphogenesis (Mark et al., 1990. Differentiation 43, 37-50). On the other hand, the possibility that chondroitin sulfate might play a role in odontoblast terminal differentiation is definitively ruled out.