ABSTRACT
OBJECTIVES: The pathogenesis of denture-induced fibrous hyperplasias has not been examined in detail to explain how tissue injury results in fibrous hyperplasia of the oral mucosa. PATIENTS AND METHODS: We examined the presence of mast cells and myofibroblasts in 33 denture-induced fibrous hyperplasias (DIFH) compared with 10 healthy gingival tissues. The parameters examined included mast cell numbers, tissue distribution, degranulation, and cell subtypes using immunohistochemistry. The presence of myofibroblasts and their likely origin was also examined by double immunofluorescense staining. Furthermore, we investigated the synthesis of osteopontin and TGF-ß, considered to be involved in the transformation of a fibroblast to a myofibroblast. RESULTS: The results demonstrated that the mast cell numbers are significantly increased in the DIFH compared with non-disease controls. The mast cell localization in lesions was higher in the superficial areas with inflammatory cell infiltration compared with the deep fibrotic area (P < 0.01). The number of tryptase-positive mast cells was significantly higher compared with chymase-positive ones. The TGF-ß- or osteopontin-positive cell infiltration into the lesion was found in high numbers. The presence of myofibroblasts was identified in 14 of 33 cases (42%), and some of these cells showed apoptosis when assessed by the TUNEL assay. On the survey of the origin of myofibroblasts, results showed αSMA and vimentin positivity indicating these transformed from fibroblasts. CONCLUSION: These results are the first to show that mast cells and myofibroblasts can be detected in DIFH, indicating important roles of these cells in the pathogenesis of this lesion.
