The effect of MMP-13, MMP-12, and AMBN on gingival enlargement and root deformation in a new type of gingival fibromatosis

This case compared gene-expression between a new type of idiopathic gingival fibromatosis (IGF) and normal gingiva, to clarify the nature of the gingival overgrowth and dental anomaly. A 6-year-old girl with generalized gingival overgrowth and root deformations was diagnosed with IGF. Gene expression profiles were compared between normal gingiva (N=9) and one IGF gingiva using cDNA microarray. Genes related to regulation of cell proliferation and proteolytic degradation were expressed strongly in IGF. MMP-13 and MMP-12 expression were 120 times and 96 times lower in IGF, respectively, whereas AMBN expression was 79 times higher. RT-PCR and immunohistochemical staining supported the microarray results. Reduced proteolytic activity due to low MMP-13 and MMP-12 expression appears to be a potential mechanism for gingival overgrowth. Genetic investigations, such as expression levels of MMP-13, MMP-12, and AMBN, may enable classification of a new syndrome characterized by gingival enlargement with abnormal root development.