title: Extracts of irradiated mature human tooth crowns contain MMP-20 protein and activity.
abstract: OBJECTIVE
  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.
  
  
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department 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.
authors.forename: J D
authors.initials: JD
authors.lastname: McGuire
authors.affiliation: Department 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.
authors.forename: A A
authors.initials: AA
authors.lastname: Mousa
authors.affiliation: Department 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.
authors.forename: Bo J
authors.initials: BJ
authors.lastname: Zhang
authors.affiliation: Department 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.
authors.forename: L S
authors.initials: LS
authors.lastname: Todoki
authors.affiliation: Department 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.
authors.forename: N T
authors.initials: NT
authors.lastname: Huffman
authors.affiliation: Center for Craniofacial Molecular Biology, Ostrow School of Dentistry, University of Southern California, Los Angeles, CA, United States.
authors.forename: K B
authors.initials: KB
authors.lastname: Chandrababu
authors.affiliation: Center for Craniofacial Molecular Biology, Ostrow School of Dentistry, University of Southern California, Los Angeles, CA, United States.
authors.forename: J
authors.initials: J
authors.lastname: Moradian-Oldak
authors.affiliation: Biological Mass Spectrometry and Proteomics Facility, School of Biological Sciences, University of Missouri-Kansas City, MO, United States.
authors.forename: A
authors.initials: A
authors.lastname: Keightley
authors.affiliation: Department 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.
authors.forename: Y
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department 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.
authors.forename: M P
authors.initials: MP
authors.lastname: Walker
authors.affiliation: Department 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.
authors.forename: J P
authors.initials: JP
authors.lastname: Gorski
mesh_terms: D000368:Aged; D015153:Blotting, Western; D003743:Dental Enamel / Q000201:enzymology / Q000528:radiation effects; D003804:Dentin / Q000201:enzymology / Q000528:radiation effects; D004586:Electrophoresis; D006801:Humans; D013058:Mass Spectrometry / Q000379:methods; D053519:Matrix Metalloproteinase 20 / Q000032:analysis* / Q000528:radiation effects; D018613:Microscopy, Confocal; D008875:Middle Aged; D008964:Molar, Third / Q000201:enzymology / Q000528:radiation effects; D011879:Radiotherapy Dosage; D053719:Tandem Mass Spectrometry; D019228:Tooth Crown / Q000201:enzymology / Q000528:radiation effects*; D055815:Young Adult
chemical_list: C507111:MMP20 protein, human; D053519:Matrix Metalloproteinase 20
keywords: Dentine–enamel junction; Human tooth crown; Matrix metalloproteinase-20; Oral cancer; Radiotherapy