title: Type IV collagen is a novel DEJ biomarker that is reduced by radiotherapy.
abstract: The dental basement membrane (BM) is composed of collagen types IV, VI, VII, and XVII, fibronectin, and laminin and plays an inductive role in epithelial-mesenchymal interactions during tooth development. The BM is degraded and removed during later-stage tooth morphogenesis; however, its original position defines the location of the dentin-enamel junction (DEJ) in mature teeth. We recently demonstrated that type VII collagen is a novel component of the inner enamel organic matrix layer contiguous with the DEJ. Since it is frequently co-expressed with and forms functional complexes with type VII collagen, we hypothesized that type IV collagen should also be localized to the DEJ in mature human teeth. To identify collagen IV, we first evaluated defect-free erupted teeth from various donors. To investigate a possible stabilizing role, we also evaluated extracted teeth exposed to high-dose radiotherapy--teeth that manifest post-radiotherapy DEJ instability. We now show that type IV collagen is a component within the morphological DEJ of posterior and anterior teeth from individuals aged 18 to 80 yr. Confocal microscopy revealed that immunostained type IV collagen was restricted to the 5- to 10-µm-wide optical DEJ, while collagenase treatment or previous in vivo tooth-level exposure to > 60 Gray irradiation severely reduced immunoreactivity. This assignment was confirmed by Western blotting with whole-tooth crown and enamel extracts. Without reduction, type IV collagen contained macromolecular α-chains of 225 and 250 kDa. Compositionally, our results identify type IV collagen as the first macromolecular biomarker of the morphological DEJ of mature teeth. Given its network structure and propensity to stabilize the dermal-epidermal junction, we propose that a collagen-IV-enriched DEJ may, in part, explain its well-known fracture toughness, crack propagation resistance, and stability. In contrast, loss of type IV collagen may represent a biochemical rationale for the DEJ instability observed following oral cancer radiotherapy.
authors.affiliation: Department of Oral and Craniofacial Sciences, School of Dentistry mcguireja@umkc.edu.
authors.forename: J D
authors.initials: JD
authors.lastname: McGuire
authors.affiliation: Department of Oral and Craniofacial Sciences, School of Dentistry Center of Excellence in Musculoskeletal and Dental Tissues, University of Missouri-Kansas City, Kansas City, MO 64108, USA.
authors.forename: J P
authors.initials: JP
authors.lastname: Gorski
authors.affiliation: Department of Oral and Craniofacial Sciences, School of Dentistry.
authors.forename: V
authors.initials: V
authors.lastname: Dusevich
authors.affiliation: Department of Oral and Craniofacial Sciences, School of Dentistry Center of Excellence in Musculoskeletal and Dental Tissues, University of Missouri-Kansas City, Kansas City, MO 64108, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Oral and Craniofacial Sciences, School of Dentistry Center of Excellence in Musculoskeletal and Dental Tissues, University of Missouri-Kansas City, Kansas City, MO 64108, USA.
authors.forename: M P
authors.initials: MP
authors.lastname: Walker
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001485:Basement Membrane / Q000737:chemistry; D015415:Biomarkers / Q000032:analysis; D024141:Collagen Type IV / Q000032:analysis* / Q000187:drug effects / Q000528:radiation effects; D024143:Collagen Type VII / Q000032:analysis; D017364:Collagenases / Q000494:pharmacology; D003743:Dental Enamel / Q000737:chemistry* / Q000187:drug effects / Q000528:radiation effects; D003746:Dental Enamel Proteins / Q000032:analysis / Q000528:radiation effects; D003804:Dentin / Q000737:chemistry* / Q000187:drug effects / Q000528:radiation effects; D058750:Epithelial-Mesenchymal Transition / Q000502:physiology; D006801:Humans; D008875:Middle Aged; D009805:Odontogenesis / Q000502:physiology; D011879:Radiotherapy Dosage; D011882:Radiotherapy, High-Energy; D019228:Tooth Crown / Q000737:chemistry / Q000528:radiation effects; D055815:Young Adult
chemical_list: D015415:Biomarkers; D024141:Collagen Type IV; D024143:Collagen Type VII; D003746:Dental Enamel Proteins; C109069:enamel matrix proteins; D017364:Collagenases
keywords: basement membrane; confocal immunofluorescent microscopy; dentin-enamel junction; enamel organic matrix; oral cancer; radiation effects