Involvement of laminin and integrins in adhesion and migration of junctional epithelium cells

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Abstract
Background and Objective: The junctional epithelium attaches to the enamel surface with hemidesmosomes (of which laminin‐5 and integrin‐α6β4 are the main components) in the internal basal lamina. Laminin‐5 is also involved in cell motility with integrin‐α3β1, although their functions have not yet been clarified. The purpose of this study was to determine the functions of those adhesive components between the tooth and the junctional epithelium during cell migration. Because an idea has been proposed that directly attached to tooth cells (DAT cells) may not contribute to cell migration, 5‐bromo‐2‐deoxyuridine staining was performed to confirm cell migration. Material and Methods: We investigated laminin‐γ2 (contained only in laminin‐5), integrin‐β4 (involved in cell–extracellular matrix contact) and integrin‐α3 (inducing cell migration) in the junctional epithelium, oral gingival epithelium and gingival sulcus epithelium of 6‐wk‐old ICR mice using laser microdissection, quantitative real‐time reverse transcription‐polymerase chain reaction, immunofluorescence and 5‐bromo‐2‐deoxyuridine staining. Results: Laminin and integrins were clearly immunolocalized in the basal lamina of all epithelium. Quantitative analysis of laminin and integrin mRNAs by laser microdissection showed that they were more highly expressed in DAT cells than in basal cells in the oral gingival epithelium. In particular, a 12‐fold higher expression of laminin‐5 was observed in the junctional epithelium compared with the oral gingival epithelium. 5‐Bromo‐2‐deoxyuridine staining showed rapid coronal migration of DAT cells. Conclusion: These results suggest that the abundant expression of laminin‐5 and integrin‐α6β4 is involved in the attachment of DAT cells to teeth by hemidesmosomes. Abundant expression of laminin‐5 and integrin‐α3β1 might assist in DAT cell migration, confirmed by 5‐bromo‐2‐deoxyuridine staining during the turnover of junctional epithelium.