DIFFERENTIAL EXPRESSION OF INTEGRINS AND LAMININ-5 IN NORMAL ORAL EPITHELIA

beta 1 and beta 4 integrins are receptors on epithelial cells mediatin g cell-extracellular matrix adhesion. Furthermore, alpha 2 beta 1 and alpha 3 beta 1 contribute to cell-cell adhesion. Laminin-5 in epitheli al basement membranes (BMs) is a ligand for alpha 6 beta 4 and alpha 3 beta 1. Expression of different integrins and laminin-5 was studied i n oral epithelium to characterize regional variations in these adhesio n molecules. Monoclonal antibodies directed against alpha 2-alpha 6 be ta 1/alpha 6 beta 4 and laminin-5 were examined in cryopreserved biops ies of normal mucosa by immunohistochemistry. Laminin-5 was expressed as a line along the BMs. The junctional epithelium showed a unique phe notype: Laminin-5 was detected in the internal BM at the tooth surface and in the external BM, where excessive laminin-5 was seen in the str oma, alpha 6 beta 4 was expressed in all cells of the junctional epith elium. Integrins alpha 4 beta 1 and alpha 5 beta 1 were not detected i n the epithelia, whereas alpha 2 beta 1 and alpha 3 beta 1 showed diff erential expression. Epithelia with well-developed rete pegs and conne ctive tissue papillae showed polarized alpha 3 beta 1 expression along the BM in the rete pegs, in contrast to negative expression at the ti ps of the connective tissue papillae. A variation in the suprabasal di stribution of alpha 2 beta 1 and alpha 3 beta 1 was observed between e pithelia from different regions. alpha 2 beta 1 and alpha 3 beta 1 wer e detected in basal/parabasal cells in keratinized epithelia, whereas there was increased suprabasal expression in nonkeratinized mucosa. Th ese results indicate inhomogeneity in the basal cell population of ora l squamous epithelia and differential expression of integrins, which m ay reflect differences in the underlying stroma. Laminin-5 deposits in the stroma underneath the junctional epithelium may indicate subclini cal gingival inflammation.