title: Role of integrin subunits in mesenchymal stem cell differentiation and osteoblast maturation on graphitic carbon-coated microstructured surfaces.
abstract: Surface roughness, topography, chemistry, and energy promote osteoblast differentiation and increase osteogenic local factor production in vitro and bone-to-implant contact in vivo, but the mechanisms involved are not well understood. Knockdown of integrin heterodimer alpha2beta1 (α2β1) blocks the osteogenic effects of the surface, suggesting signaling by this integrin homodimer is required. The purpose of the present study was to separate effects of surface chemistry and surface structure on integrin expression by coating smooth or rough titanium (Ti) substrates with graphitic carbon, retaining surface morphology but altering surface chemistry. Ti surfaces (smooth [Ra < 0.4 μm], rough [Ra ≥ 3.4 μm]) were sputter-coated using a magnetron sputtering system with an ultrapure graphite target, producing a graphitic carbon thin film. Human mesenchymal stem cells and MG63 osteoblast-like cells had higher mRNA for integrin subunits α1, α2, αv, and β1 on rough surfaces in comparison to smooth, and integrin αv on graphitic-carbon-coated rough surfaces in comparison to Ti. Osteogenic differentiation was greater on rough surfaces in comparison to smooth, regardless of chemistry. Silencing integrins β1, α1, or α2 decreased osteoblast maturation on rough surfaces independent of surface chemistry. Silencing integrin αv decreased maturation only on graphitic carbon-coated surfaces, not on Ti. These results suggest a major role of the integrin β1 subunit in roughness recognition, and that integrin alpha subunits play a major role in surface chemistry recognition.
authors.affiliation: Department of Biomedical Engineering, School of Engineering, Virginia Commonwealth University, Richmond, VA, USA.
authors.forename: Rene
authors.initials: R
authors.lastname: Olivares-Navarrete
authors.affiliation: Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Mexico City, Mexico.
authors.forename: Sandra E
authors.initials: SE
authors.lastname: Rodil
authors.affiliation: Department of Biomedical Engineering, School of Engineering, Virginia Commonwealth University, Richmond, VA, USA.
authors.forename: Sharon L
authors.initials: SL
authors.lastname: Hyzy
authors.affiliation: Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, USA.
authors.forename: Ginger R
authors.initials: GR
authors.lastname: Dunn
authors.affiliation: Facultad de Odontologia, Universidad Nacional Autonoma de Mexico, Mexico City, Mexico.
authors.forename: Argelia
authors.initials: A
authors.lastname: Almaguer-Flores
authors.affiliation: Department of Biomedical Engineering, School of Engineering, Virginia Commonwealth University, Richmond, VA, USA.
authors.forename: Zvi
authors.initials: Z
authors.lastname: Schwartz
authors.affiliation: Department of Biomedical Engineering, School of Engineering, Virginia Commonwealth University, Richmond, VA, USA; Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, USA. Electronic address: bboyan@vcu.edu.
authors.forename: Barbara D
authors.initials: BD
authors.lastname: Boyan
mesh_terms: D002448:Cell Adhesion / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects*; D002460:Cell Line; D020099:Coated Materials, Biocompatible / Q000494:pharmacology*; D020868:Gene Silencing / Q000187:drug effects; D006108:Graphite / Q000494:pharmacology*; D006801:Humans; D016023:Integrins / Q000378:metabolism*; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D010006:Osteoblasts / Q000166:cytology*; D021122:Protein Subunits / Q000378:metabolism*; D013499:Surface Properties; D014025:Titanium / Q000494:pharmacology
chemical_list: D020099:Coated Materials, Biocompatible; D016023:Integrins; D021122:Protein Subunits; D006108:Graphite; D014025:Titanium
keywords: Graphitic carbon coating; Growth factors; Mesenchymal stem cells; Osteoblast differentiation; Titanium