title: Effect of proteoglycans at interfaces as related to location, architecture, and mechanical cues.
abstract: BACKGROUND
  Covalently bound functional GAGs orchestrate tissue mechanics through time-dependent characteristics.
  
  
  OBJECTIVE
  The role of specific glycosaminoglycans (GAGs) at the ligament-cementum and cementum-dentin interfaces within a human periodontal complex were examined. Matrix swelling and resistance to compression under health and modeled diseased states was investigated.
  
  
  METHODS
  The presence of keratin sulfate (KS) and chondroitin sulfate (CS) GAGs at the ligament-cementum and cementum-dentin interfaces in human molars (N=5) was illustrated by using enzymes, atomic force microscopy (AFM), and AFM-based nanoindentation. The change in physical characteristics of modeled diseased states through sequential digestion of keratin sulfate (KS) and chondroitin sulfate (CS) GAGs was investigated. One-way ANOVA tests with P<0.05 were performed to determine significant differences between groups. Additionally, the presence of mineral within the seemingly hygroscopic interfaces was investigated using transmission electron microscopy.
  
  
  RESULTS
  Immunohistochemistry (N=3) indicated presence of biglycan and fibromodulin small leucine rich proteoglycans at the interfaces. Digestion of matrices with enzymes confirmed the presence of KS and CS GAGs at the interfaces by illustrating a change in tissue architecture and mechanics. A significant increase in height (nm), decrease in elastic modulus (GPa), and tissue deformation rate (nm/s) of the PDL-C attachment site (215±63-424±94nm; 1.5±0.7-0.4±0.2GPa; 21±7-48±22nm/s), and cementum-dentin interface (122±69-360±159nm; 2.9±1.3-0.7±0.3GPa; 18±4-30±6nm/s) was observed.
  
  
  CONCLUSIONS
  The sequential removal of GAGs indicated loss in intricate structural hierarchy of hygroscopic interfaces. From a mechanics perspective, GAGs provide tissue recovery/resilience. The results of this study provide insights into the role of GAGs toward conserved tooth movement in the socket in response to mechanical loads, and modulation of potentially deleterious strain at tissue interfaces.
authors.affiliation: Division of Biomaterials and Bioengineering, Department of Preventive and Restorative Dental Sciences, School of Dentistry, University of California, San Francisco, San Francisco, CA 94143, United States.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Kurylo
authors.affiliation: Division of Biomaterials and Bioengineering, Department of Preventive and Restorative Dental Sciences, School of Dentistry, University of California, San Francisco, San Francisco, CA 94143, United States.
authors.forename: Kathryn
authors.initials: K
authors.lastname: Grandfield
authors.affiliation: Division of Biomaterials and Bioengineering, Department of Preventive and Restorative Dental Sciences, School of Dentistry, University of California, San Francisco, San Francisco, CA 94143, United States.
authors.forename: Grayson W
authors.initials: GW
authors.lastname: Marshall
authors.affiliation: Materials Division, The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, United States.
authors.forename: Virginia
authors.initials: V
authors.lastname: Altoe
authors.affiliation: Materials Division, The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, United States.
authors.forename: Shaul
authors.initials: S
authors.lastname: Aloni
authors.affiliation: Division of Biomaterials and Bioengineering, Department of Preventive and Restorative Dental Sciences, School of Dentistry, University of California, San Francisco, San Francisco, CA 94143, United States. Electronic address: Sunita.ho@ucsf.edu.
authors.forename: Sunita P
authors.initials: SP
authors.lastname: Ho
mesh_terms: D000293:Adolescent; D000328:Adult; D003739:Dental Cementum / Q000502:physiology; D003804:Dentin / Q000502:physiology; D006025:Glycosaminoglycans / Q000502:physiology*; D006801:Humans; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D018625:Microscopy, Atomic Force; D008855:Microscopy, Electron, Scanning; D008963:Molar; D010513:Periodontal Ligament / Q000502:physiology; D011509:Proteoglycans / Q000502:physiology*; D017001:Tooth Demineralization; D014092:Tooth Root / Q000648:ultrastructure*
chemical_list: D006025:Glycosaminoglycans; D011509:Proteoglycans
keywords: Glycosaminoglycans; Indentation; Interfaces; Tissue mechanics; Tissue recovery