Matrix-mediated epitheliomesenchymal interactions control dental cytodifferentiations. Experiments were performed in order to study the effects of noncollagenous proteins extracted from dentin on cultured enamel organs and dental papillae.

Seven noncollagenous protein fractions were prepared from rabbit incisor dentin and used as substrates to coat Millipore filters. Embryonic mouse tooth germs were dissociated and the isolated tissues were cultured for 4 days on these different substrates as well as on noncoated Millipore filters.

When compared to control cultures, only two protein fractions affected the behaviour of epithelial cells. A slight elongation of the cell body and a preferential localization of the nuclei at the basal pole of the cells in contact with the filter was observed with protein fractions 5 and 6.

When dental papillae were cultured on Millipore filters coated either with protein fraction 2 or fraction 6, the mesenchymal cells in contact with the filter elongated, polarized and demonstrated a high metabolic activity. Such modifications in the cell organization, implying changes in the cytoskeleton organization and, or, activity, never occurred spontaneously or in the presence of isolated collagens (I–V), laminin or fibronectin.

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