Matrix metalloproteinase inhibition impairs the processing, formation and mineralization of dental tissues during mouse molar development

Organotypic cultures of embryonic mouse tooth germs were used to investigate the developmental expression and roles of MMPs in the formation and mineralization of dentin and enamel matrices. The spatially and temporally regulated expression of MMP-2, MMP-9 and MMP-20 in developing mouse tooth germs in vivo was maintained in culture. The inhibition of metalloproteinases activity by marimastat altered the morphogenesis and mineralization of the tooth germs associated with an inhibition of the activation of both MMP-20 and MMP-2. MMP inhibition deregulated the molecular processing of two major dental matrix proteins, amelogenin and dentin sialoprotein (DSP). This coincided with their accumulation and the loss of their normal distribution within the extracellular matrix, resulting in a defective mineralization of dentin and enamel matrices. These findings demonstrate the critical role of MMPs in the processing and maturation of the dental matrix.