IADR Abstract Archives
Matrix-Metalloproteinase-13 Deletion Reduces Dentine and Enamel Volume, but Increases Dystrophic-Pulp-Calcification
Objectives: Matrix-metalloproteinase-13 (Mmp13) is important in bone formation/remodelling and dental-pulp-mineralisation. Mmp13-expression is repressed by histone-deacetylase (HDAC) 4 in bone and increased by HDAC-inhibition in dental-pulp-cell cultures, while Mmp13-inhibition affects dental-pulp-cell repair processes in vitro; however, little is known about the dental-role of Mmp13 in vivo. The aim was to investigate the role of Mmp13/collagenase-3 in tooth development and relationship with mineralisation-associated class-2 HDAC-expression.
Methods: Homozygous Mmp13-deficient mice (Mmp13−/−) on a C57BL/6 background were sacrificed at various time-points and compared with wild-type (WT) mice. The jaws were fixed, decalcified, paraffin-embedded and sectioned (5μm), prior to haematoxylin/eosin (H&E) and immunohistochemical (IHC) staining. Mmp13 expression was analysed at 1, 3, 6, 9 and 11 days post-natal, before assessment of odontoblast markers (Nestin, DSP), Mmp9, HDAC4 and 5 in similar sections at 10days and 12wks. MicroCT was used for quantitative analysis of enamel/dentine volumes in developing and mature teeth (3 month-old, male mice) and statistically analysed using a 2-sample student t-test (p<0.05).
Results: Mmp13 was highly expressed in oral-mucosa, pulp-tissue, ameloblasts and odontoblasts at all time-points; however, there was reduced expression in mature odontoblasts. Dental-hard-tissue in Mmp13-deleted mice was phenotypically normal, but the expression of Mmp9, HDAC5 and DSP was decreased compared with control. HDAC4 and 5 expression was high in odontoblasts in developing teeth, but reduced in adult samples. Pulp-stone-formation was frequently present in adult Mmp13-KO teeth (incisor/molar), but was rarely evident in WT equivalents. Enamel (p=0.045) and dentine (p=0.0003) volume was significantly reduced (13%/16% respectively) in adult Mmp13-KO samples, while animal-weight, mineral-density and total-pulp-volume was unchanged.
Conclusions: Mmp13-deficient mice exhibit a normal dental-phenotype in developing and adult teeth, but a reduced enamel and dentine volume compared with WT mice. Dystrophic pulp calcification was a frequent finding in Mmp13 groups, but not in WT-controls suggestive of a role for Mmp13 in the organisation of mineralisation in the tooth.
Methods: Homozygous Mmp13-deficient mice (Mmp13−/−) on a C57BL/6 background were sacrificed at various time-points and compared with wild-type (WT) mice. The jaws were fixed, decalcified, paraffin-embedded and sectioned (5μm), prior to haematoxylin/eosin (H&E) and immunohistochemical (IHC) staining. Mmp13 expression was analysed at 1, 3, 6, 9 and 11 days post-natal, before assessment of odontoblast markers (Nestin, DSP), Mmp9, HDAC4 and 5 in similar sections at 10days and 12wks. MicroCT was used for quantitative analysis of enamel/dentine volumes in developing and mature teeth (3 month-old, male mice) and statistically analysed using a 2-sample student t-test (p<0.05).
Results: Mmp13 was highly expressed in oral-mucosa, pulp-tissue, ameloblasts and odontoblasts at all time-points; however, there was reduced expression in mature odontoblasts. Dental-hard-tissue in Mmp13-deleted mice was phenotypically normal, but the expression of Mmp9, HDAC5 and DSP was decreased compared with control. HDAC4 and 5 expression was high in odontoblasts in developing teeth, but reduced in adult samples. Pulp-stone-formation was frequently present in adult Mmp13-KO teeth (incisor/molar), but was rarely evident in WT equivalents. Enamel (p=0.045) and dentine (p=0.0003) volume was significantly reduced (13%/16% respectively) in adult Mmp13-KO samples, while animal-weight, mineral-density and total-pulp-volume was unchanged.
Conclusions: Mmp13-deficient mice exhibit a normal dental-phenotype in developing and adult teeth, but a reduced enamel and dentine volume compared with WT mice. Dystrophic pulp calcification was a frequent finding in Mmp13 groups, but not in WT-controls suggestive of a role for Mmp13 in the organisation of mineralisation in the tooth.