Phenotypic alteration of basal cells in oral lichen planus; switching keratin 19 and desmoglein 1 expression.

In oral lichen planus, extracellular matrix and basal cells are damaged by T-lymphocytes. As a consequence, changes in expression of collagen fibers within the connective tissue and cytoskeletons of the epithelial tissue can be observed. With the goal of examining the characteristic changes undergone by basal cells as a consequence of T-lymphocytes damage in oral lichen planus, we investigated protein expression in the epithelial-connective junction. We selected 20 cases of oral lichen planus and 5 control samples of buccal mucosa. Subsequently, we divided the oral lichen planus cases into thin and thick parts based on the mean values of epithelial thickness from the control samples, and counted the positive rate of collagen IV, keratin 19, desmoglein 1, and Ki-67. Collagen IV immune-reactivity partially disappeared or thickened in oral lichen planus. The keratin 19 positive rate in oral lichen planus cases was significantly lower than in the controls. Desmoglein 1 positive rate of the thick part was significantly higher compared to the thin part of oral lichen planus. Thus, modifications in basal cells with both reduced keratin 19 expression and alterations of desmoglein 1 expression suggest that in oral lichen planus, as a consequence of cell injury or regeneration in the interface area, there is a disappearance of the "true basal cell nature".