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J Dent. 2014 May;42(5):626-35. doi: 10.1016/j.jdent.2014.02.013. Epub 2014 Mar 4.

Extracts of irradiated mature human tooth crowns contain MMP-20 protein and activity.

Author information

  • 1Department of Oral and Craniofacial Science, Center of Excellence in Dental and Musculoskeletal Tissues, School of Dentistry, University of Missouri-Kansas City, Kansas City, MO, United States.
  • 2Center for Craniofacial Molecular Biology, Ostrow School of Dentistry, University of Southern California, Los Angeles, CA, United States.
  • 3Biological Mass Spectrometry and Proteomics Facility, School of Biological Sciences, University of Missouri-Kansas City, MO, United States.
  • 4Department of Oral and Craniofacial Science, Center of Excellence in Dental and Musculoskeletal Tissues, School of Dentistry, University of Missouri-Kansas City, Kansas City, MO, United States. Electronic address: gorskij@umkc.edu.

Abstract

OBJECTIVES:

We recently demonstrated a significant correlation between enamel delamination and tooth-level radiation dose in oral cancer patients. Since radiation can induce the synthesis and activation of matrix metalloproteinases, we hypothesized that irradiated teeth may contain active matrix metalloproteinases.

MATERIALS AND METHODS:

Extracted teeth from oral cancer patients treated with radiotherapy and from healthy subjects were compared. Extracted mature third molars from healthy subjects were irradiated in vitro and/or incubated for 0-6 months at 37°C. All teeth were then pulverized, extracted, and extracts subjected to proteomic and enzymatic analyses.

RESULTS:

Screening of irradiated crown extracts using mass spectrometry identified MMP-20 (enamelysin) which is expressed developmentally in dentine and enamel but believed to be removed prior to tooth eruption. MMP-20 was composed of catalytically active forms at Mr=43, 41, 24 and 22kDa and was immunolocalized predominantly to the morphological dentine enamel junction. The proportion of different sized MMP-20 forms changed with incubation and irradiation. While the pattern was not altered directly by irradiation of healthy teeth with 70Gy, subsequent incubation at 37°C for 3-6 months with or without prior irradiation caused the proportion of Mr=24-22kDa MMP-20 bands to increase dramatically. Extracts of teeth from oral cancer patients who received >70Gy radiation also contained relatively more 24 and 22kDa MMP-20 than those of healthy age-related teeth.

CONCLUSION:

MMP-20 is a radiation-resistant component of mature tooth crowns enriched in the dentine-enamel. We speculate that MMP-20 catalyzed degradation of organic matrix at this site could lead to enamel delamination associated with oral cancer radiotherapy.

Copyright © 2014 Elsevier Ltd. All rights reserved.

KEYWORDS:

Dentine–enamel junction; Human tooth crown; Matrix metalloproteinase-20; Oral cancer; Radiotherapy

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