Accelerated DNA fragmentation of the denture-bearing mucosal epithelium inan 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 o f keratinizing system of rats with and without streptozotocin-induced diabe tes 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 w ithout pressure. The synergy of the mechanical pressure and diabetic condit ion for 2 weeks greatly accelerated the DNA fragmentation, showing 8-fold i ncrease in TUNEL positive cells over the normal control, and caused exfolia tion of the stratum corneum. A 4-week exposure of diabetics to the masticat ory pressure induced laminar splitting in the midst of the spinosum. Some c ells in the stratum granulosum exhibited a sign of DNA fragmentation when l aminar splitting took place in the vital cell layer. Premature DNA fragment ation may disturb the adhesion between spinosum cells and prevent the matur ation 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 pressu re in diabetic patients.