Evidence that laminin-5 is a component of the tooth surface internal basallamina, supporting epithelial cell adhesion

Laminin-5 (Ln-5) is an extracellular matrix (ECM) glycoprotein found in epi thelial basal laminae. We studied its expression on the surface of rat mola rs, in relationship to the location of the internal basal lamina (IBL) of t he junctional epithelium (JE). In order to avoid disruption of the JE-tooth interface as much as possible, the surface of molars was prepared by mecha nical removal of tissue debris and detergent/osmotic lysis of epithelial ce ll layers, and directly stained by immunohistochemistry, without sectioning . Antibodies to Ln-5 specifically stained a narrow band in the region of th e cemento-enamel junction (CEJ), consistent with the expected location of t he IBL. Western blotting of ECM material detergent-solubilized from the pre pared tooth surfaces confirmed the molecular nature of Ln-5 identified by i mmunohistochemistry. By the use of a high-definition 3-D microscope, it app eared that Ln-5 coated the most apical part of the enamel and the most coro nal portion of the cementum, on either side of the CEJ. In adhesion assays performed directly on tooth surfaces, epithelial cells adhered preferential ly to the Ln-5 coated area of the tooth compared to the root surface, which is coated by other ECM components. Adhesion to the Ln-5 coated surface was specifically inhibited by a function-blocking monoclonal antibody to Ln-5. These results suggest that Ln-5 is a component of the IBL, and that it may be important in promoting adhesion of JE cells onto the tooth surface.