Diabetes Increases TNF-a, FOXO1& Fibroblast Apoptosis in Healing Gingival Wounds

Although it is widely accepted that diabetes impairs oral connective tissue wound healing little is known about the mechanisms through which this may occur Objective: To investigate enhanced fibroblast apoptosis as a potential mechanisms through which diabetes affects gingival wound healing in type 2 diabetic mice. Methods: Small 1.5mm excisional wounds were created in the anterior palatal gingiva of type two diabetic (db/db) and normoglycemic littermates. Nuclear and cytoplasmic extracts of healing tissue were examined by ELISA for TNF-a and activation of the pro-apoptotic transcription factor FOXO1, respectively. Histologic sections were examined by the TUNEL assay for fibroblast apoptosis, expression of activated caspase-3 and the formation of new connective tissue. Significance was determined by Student's T test. Results: Five days after wounding the formation of new connective tissue in type two diabetic mice was half that of normal glycemic controls (P<0.05). There was a six fold increase in the number of apoptotic fibroblasts (P<0.05) which could be accounted for by a three fold increase in TNF-a levels, a two fold increase in activation of the pro apoptotic transcription factor, FOXO1 and a three fold increase in the number of fibroblasts expressing activated caspase-3, all of which were significant (P<0.05). Conclusion: Diabetic mice exhibited significantly impaired formation of gingival connective tissue compared to normal glycemic mice. This may be due to significantly enhanced fibroblast apoptosis. Diabetes may increase apoptosis during wound healing by enhancing the levels of TNF-a, caspase-3 activation and FOXO1 activation. These studies provide insight into mechanisms through which diabetes may impair the connective tissue healing in the oral cavity. This work was supported by grant R01 DE017732 funded by the National Institute of Dental and Craniofacial Research (NIDCR).