Permeability of lichen planus lesions and healthy buccal mucosa to water.
The resurgence of interest in the oral mucosa as a route for drug delivery requires a thorough understanding of the permeability of this tissue in health and disease. Previous work has indicated that non-keratinized oral mucosa is more permeable than its keratinized counterpart. It has been suggested that pathological hyperkeratotic mucosa, which was previously non-keratinized, would be more permeable than healthy tissue. Equivocal results obtained from animal studies in which chemical or mechanical irritation was used to induce a hyperplastic and hyperkeratotic epithelium, prompted us to conduct a study on the comparison of the permeability to water of lichen planus lesions and healthy buccal mucosa. Buccal mucosa was obtained from six patients with previously confirmed lichen planus and from six clinically healthy patients. Thawed biopsies from each specimen were mounted in flow-through diffusion cells and their permeability to tritiated water determined using a continuous flow-through perfusion system. Specimens were examined histologically before and after permeability experiments. No statistically significant differences between mean steady state flux values (10-20 h) for lichen planus tissue and healthy buccal mucosa were found. These results warrant further studies with other oral conditions associated with hyperkeratosis to establish whether the nature and course of the condition are determinants for the retention or loss of the epithelium's permeability characteristics.