Abstract
Oral lichen planus (OLP) is a chronic inflammatory disease with different clinical types. Reticular and erosive forms are the most common. Although the cause of OLP remains speculative, many findings suggest auto-immune involvement, mediated by T lymphocytes against the basal keratinocytes. Inflammation, mechanical trauma or toxic agents can affect the epithelial homeostasia. Increased apoptosis may cause a decrease in epithelial thickness reflecting in the activity of the lesion. The objective of this study was to evaluate the occurrence of apoptosis and epithelial thickness in reticular and erosive forms of OLP. 15 samples of OLP each type (reticular and erosive) plus 10 of healthy mucosa were collected and processed. After morphometry, the apoptotic index and epithelial thickness were obtained. TUNEL and M30 CytoDEATH immunohistochemical assay were used to validate the morphologic criteria used. Apoptosis in the erosive OLP was significantly more intense than in the reticular type and both forms of OLP presented more apoptosis than the healthy oral mucosa. Healthy oral mucosa was thicker than both OLP forms and thicker in OLP reticular form than in the erosive one. The clinical differences between reticular and erosive forms of OLP are related to variations in epithelial thickness and in intensity of apoptosis.
Highlights
Oral lichen planus (OLP) is a chronic inflammatory disease with unknown etiology [1], affecting approximately 2% of the population [2,3]
Sections processed by TUNEL technique showed a diffuse positive labeling of the basal and supra-basal keratinocytes indicating and confirming the occurrence of apoptosis, as previously detected by morphological criteria using Shorr staining (Fig. 2A and 2B)
Sections processed by M3O cytoDEATH method confirmed the occurrence of apoptosis as detected using Shorr staining, with a positive diffuse labeling within the basal and supra-basal keratinocytes (Fig. 3A and 3B)
Summary
Oral lichen planus (OLP) is a chronic inflammatory disease with unknown etiology [1], affecting approximately 2% of the population [2,3]. OLP appears in different clinical forms [3] and Neville et al [1] recognize essentially two types, the reticular and the erosive. The reticular lesions appear as a network of connecting and overlapping lines, papules or plaques [3]. The erosive and ulcerative forms are more destructive forms and cause enormous oral discomfort [4], while reticular forms are associated with fewer symptoms and might reflect an intermediate phase [5]. OLP is characterized histologically by epithelial basal cell destruction and a dense subepithelial lymphocytic infiltrate [6,7]. Degenerating basal keratinocytes form colloid or “Civatte” bodies. The ultrastructure of colloid bodies suggests that they are apoptotic keratinocytes [2]
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