Accelerated DNA fragmentation of the denture-bearing mucosal epithelium in an animal model of diabetes

This study examined the effect of masticatory pressure transmitted directly to the hard palate mucosa on the final stage of terminal differentiation of keratinizing system of rats with and without streptozotocin-induced diabetes mellitus. In the nondiabetic rats with masticatory pressure, the number of terminal-deoxynucleotidyl-transferase-mediated deoxyuridine-triphospate-biotin nick end labelling (TUNEL) positive cells tended to increase about twice as much as in the nondiabetic rats without pressure with and without denture. A similar tendency of increase was observed in the diabetic rats without pressure. The synergy of the mechanical pressure and diabetic condition for 2 weeks greatly accelerated the DNA fragmentation, showing 8-fold increase in TUNEL positive cells over the normal control, and caused exfoliation of the stratum corneum. A 4-week exposure of diabetics to the masticatory pressure induced laminar splitting in the midst of the spinosum. Some cells in the stratum granulosum exhibited a sign of DNA fragmentation when laminar splitting took place in the vital cell layer. Premature DNA fragmentation may disturb the adhesion between spinosum cells and prevent the maturation of stratum corneum. Increase in Bax protein-like immunoreactivity in these epithelial cells as revealed by immunocytochemistry may underlie the premature DNA fragmentation in the oral masticatory epithelium under pressure in diabetic patients.