Assessing the Effect of Matrix Metalloproteinase-9 on the Growth of Mice Teeth by NMR

Qingwen Ni[1,2] , Shuo Chen[3]
Page No. 186-197

A wide spectrum of mouse and human disorders affecting tooth and bone biomineralization shows
that dentin and bone formation are under strict genetic control. Although the controlling
mechanisms of dentinogenesis and osteogenesis require further study, a large body of evidence
points to the importance of the matrix metalloproteinases (MMPs) participate in a wide variety of
extracellular matrix degradation. Currently, we attempt to find that in MMP-9 knock out (KO) mice
displayed severe attrition on teeth development. In this study a technique of low-field nuclear
magnetic resonance (NMR) spin relaxation (T2) is applied for assessment of MMP-9 KO mice and
wild-type (normal). Then, the spin relaxation decay curve is converted into T2 distribution spectrum.
Here, we propose an NMR calibration method – the ratio of the amount of fluid in pulp
component to the amount of fluid in dentin component obtained from NMR T2 distribution spectra.
This ratio method can be used to calibrate the age-growth MMP-9 KO structural changes in teeth
while eliminating any variations in size of teeth. Five MMP-9 KO groups from 10 days to 147 days
were tested in this study. It is found that the ratio of dental pulp chamber to dentin greatly varies on
the early age periods (1 month) than on the elder ages suggesting that MMP-9 is more involved in
early stages of tooth development and formation.
Keywords : MMP-9, teeth, NMR, x-ray.