Claudins 1,4,5,7 and Occludin in Ameloblastomas and Developing Human Teeth

OBJECTIVE: To analyze the distribution pattern of claudins 1, 4, 5, 7 and occludin in benign and malignant ameloblastomas and developing human teeth. METHODS: Paraffin-embedded tissue specimens of 25 benign and 4 malignant ameloblastomas and 2 developing human teeth were examined immunohistochemically using antibodies against claudins 1, 4, 5, 7 and occludin. RESULTS: In ameloblastomas strongest expression was seen for claudins 1 and 7 while claudin 4 was expressed less frequently. Claudin 5 and occludin were seen only in a minority of cases. There were no evident differences in the expression of claudins or occludin between different histological subtypes of ameloblastomas nor between benign or malignant cases. For claudins 1 and 4 central cells showed stronger immunoreactivity than peripheral ones. In developing teeth both claudin 1 and 7 stained strongly in the enamel epithelium, ameloblasts and enamel matrix, but staining for claudin 4 was relatively weak. Claudin 5 was preferentially expressed only in vessels, and occludin staining ranged from negative to weak in ameloblastomas and teeth germs. CONCLUSION: There were no clear differences in the expression levels between benign or malignant ameloblastic tumors. The strong immunoreactivity of ameloblasts and newly synthesized enamel matrix for claudins 1 and 7 indicates that they may be involved in cell signalling influencing enamel formation.