title: Type VII collagen is enriched in the enamel organic matrix associated with the dentin-enamel junction of mature human teeth.
abstract: The inner enamel region of erupted teeth is known to exhibit higher fracture toughness and crack growth resistance than bulk phase enamel. However, an explanation for this behavior has been hampered by the lack of compositional information for the residual enamel organic matrix. Since enamel-forming ameloblasts are known to express type VII collagen and type VII collagen null mice display abnormal amelogenesis, the aim of this study was to determine whether type VII collagen is a component of the enamel organic matrix at the dentin-enamel junction (DEJ) of mature human teeth. Immunofluorescent confocal microscopy of demineralized tooth sections localized type VII collagen to the organic matrix surrounding individual enamel rods near the DEJ. Morphologically, immunoreactive type VII collagen helical-bundles resembled the gnarled-pattern of enamel rods detected by Coomassie Blue staining. Western blotting of whole crown or enamel matrix extracts also identified characteristic Mr=280 and 230 kDa type VII dimeric forms, which resolved into 75 and 25 kDa bands upon reduction. As expected, the collagenous domain of type VII collagen was resistant to pepsin digestion, but was susceptible to purified bacterial collagenase. These results demonstrate the inner enamel organic matrix in mature teeth contains macromolecular type VII collagen. Based on its physical association with the DEJ and its well-appreciated capacity to complex with other collagens, we hypothesize that enamel embedded type VII collagen fibrils may contribute not only to the structural resilience of enamel, but may also play a role in bonding enamel to dentin.
authors.affiliation: Department of Oral and Craniofacial Sciences, School of Dentistry, University of Missouri - Kansas City, Kansas City, MO 64108, USA. Electronic address: mcguireja@umkc.edu.
authors.forename: Jacob D
authors.initials: JD
authors.lastname: McGuire
authors.affiliation: Department of Oral and Craniofacial Sciences, School of Dentistry, University of Missouri - Kansas City, Kansas City, MO 64108, USA; Center of Excellence in Musculoskeletal and Dental Tissues, University of Missouri - Kansas City, Kansas City, MO 64108, USA.
authors.forename: Mary P
authors.initials: MP
authors.lastname: Walker
authors.affiliation: Department of Oral and Craniofacial Sciences, School of Dentistry, University of Missouri - Kansas City, Kansas City, MO 64108, USA.
authors.forename: Ahmad
authors.initials: A
authors.lastname: Mousa
authors.affiliation: Department of Oral and Craniofacial Sciences, School of Dentistry, University of Missouri - Kansas City, Kansas City, MO 64108, USA; Center of Excellence in Musculoskeletal and Dental Tissues, University of Missouri - Kansas City, Kansas City, MO 64108, USA.
authors.forename: Yong
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Oral and Craniofacial Sciences, School of Dentistry, University of Missouri - Kansas City, Kansas City, MO 64108, USA; Center of Excellence in Musculoskeletal and Dental Tissues, University of Missouri - Kansas City, Kansas City, MO 64108, USA.
authors.forename: Jeff P
authors.initials: JP
authors.lastname: Gorski
mesh_terms: D024143:Collagen Type VII / Q000378:metabolism*; D003743:Dental Enamel / Q000378:metabolism*; D003804:Dentin / Q000378:metabolism*; D006801:Humans; D014070:Tooth / Q000378:metabolism*
chemical_list: D024143:Collagen Type VII
keywords: Dentin–enamel junction; Immunofluorescent confocal microscopy; Mature human enamel; Type VII collagen