β1 and β4 integrins are receptors on epithelial cells mediating cell‐extracellular matrix adhesion. Furthermore, α2β1 and α3β1 contribute to cell‐cell adhesion. Laminin‐5 in epithelial basement membranes (BMs) is a ligand for α6β4 and α3β1. Expression of different integrins and laminin‐5 was studied in oral epithelium to characterize regional variations in these adhesion molecules. Monoclonal antibodies directed against α2‐α6β1/α6β4 and laminin‐5 were examined in cryopreserved biopsies of normal mucosa by immunohistochemistry. Laminin‐5 was expressed as a line along the BMs. The junctional epithelium showed a unique phenotype: 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 stroma. α6β4 was expressed in all cells of the junctional epithelium. Integrins α4β1 and α5β1 were not detected in the epithelia, whereas α2β1 and α3β1 showed differential expression. Epithelia with well‐developed rete pegs and connective tissue papillae showed polarized α3β1 expression along the BM in the rete pegs, in contrast to negative expression at the tips of the connective tissue papillae. A variation in the suprabasal distribution of α2β1 and α3β1 was observed between epithelia from different regions. α2β1 and α3β1 were detected in basal/parabasal cells in keratinized epithelia, whereas there was increased suprabasal expression in nonkeratinized mucosa. These results indicate inhomogeneity in the basal cell population of oral squamous epithelia and differential expression of integrins, which may reflect differences in the underlying stroma. Laminin‐5 deposits in the stroma underneath the junctional epithelium may indicate subclinical gingival inflammation.

Periodontitis is characterized by destruction of dento-gingival fibers and apical migration of the junctional epithelium. Tissue destruction may be associated with altered interactions between epithelium and connective tissue mediated by integrins localized in the basement membrane zone. We examined the expression of alpha2beta1, alpha3beta1, alpha4/alpha5/beta1, alpha6beta4 and their related extracellular matrix (ECM) ligands: laminin-1, laminin-5, and collagen type IV in untreated periodontitis sites of various categories. The expression and location of ECM proteins along the basement membrane were found to be similar between clinically healthy and periodontitis affected tissues. However, ECM proteins were more diffusely distributed in connective tissue (CT) of periodontitis tissues as streak-like/ fibrillar/granular stainings, particularly beneath the pocket epithelium (PE) and around the blood vessels. This may reflect an increase in inflammatory cell migration. The more widespread distribution of integrins alpha2beta1, alpha3beta1 in PE of periodontitis specimens may be related to disease activity and increased rate of keratinocyte proliferation and migration. Moreover, the weaker expression of alpha6beta4 in junctional epithelium (JE) of periodontitis affected tissues may be related to the epithelial detachment from the tooth surface. Clarification of expressions of integrins and their ligands in relation to known clinical disease susceptibility factors may provide information on the onset and progression mechanisms of periodontal disease destruction.

Development of squamous cell carcinomas (SCCs) involves alterations in the adhesive interactions in the epithelium and invasion through the basement membrane. Therefore, changes in the expression of receptors and ligands involved in cell‐cell and cell‐matrix adhesion may be essential for the transformation of a premalignant into a malignant lesion. The aim of this study was to examine if expression of specific cell adhesion molecules can be used as markers of malignant development. By immunohistochemistry, we examined the expression pattern of integrins α2β1, α3β1, α6β4 and laminin‐5 in biopsies from SCCs (n=18), premalignant lesions (leukoplakias, n=21) and non‐premalignant tissue with chronic inflammation (n=11). In poorly differentiated SCCs, patchy loss of α3β1, α6β4 and laminin‐5 expression was pronounced at the invasion front, whereas there was a tendency to increased expression of α2β1. Analogous to the SCCs, biopsies from the leukoplakias and the non‐premalignant inflammatory tissue showed alterations of the expression of α3β1 and α6β4 in the basal cell layers and of laminin‐5. However, a characteristic finding in biopsies from leukoplakias was loss of α2β1 and α3β1 in the suprabasal cells. There was no unequivocal expression of the adhesion molecules distinguishing between inflammatory tissue, premalignant, and malignant lesions.