title: Mediation of osteogenic differentiation of human mesenchymal stem cells on titanium surfaces by a Wnt-integrin feedback loop.
abstract: Peri-implant bone formation depends on the ability of mesenchymal cells to colonize the implant surface and differentiate into osteoblasts. Human mesenchymal stem cells (HMSCs) undergo osteoblastic differentiation on microstructured titanium (Ti) surfaces in the absence of exogenous factors, but the mechanisms are unknown. Wnt proteins are associated with an osteoblast phenotype, but how Wnt signaling regulates HMSC differentiation on microstructured Ti surfaces is not known. HMSCs were cultured on tissue culture polystyrene or Ti (PT [Sa = 0.33 μm, θ = 96°], SLA [Sa = 2.5 μm, θ = 132°], modSLA [hydrophilic-SLA]). Expression of calcium-dependent Wnt ligand WNT5A increased and canonical Wnt pathway ligands decreased on microstructured Ti in a time-dependent manner. Treatment of HMSCs with canonical ligand Wnt3a preserved the mesenchymal phenotype on smooth surfaces. Treatment with Wnt5a increased osteoblastic differentiation. Expression of integrins ITGA1, ITGA2, and ITGAV increased over time and correlated with increased WNT5A expression. Treatment of HMSCs with Wnt5a, but not Wnt3a, increased integrin expression. Regulation of integrin expression due to surface roughness and energy was ablated in WNT5A-knockdown HMSCs. This indicates that surface properties regulate stem cell fate and induce osteoblast differentiation via the Wnt calcium-dependent pathway. Wnt5a enhances osteogenesis through a positive feedback with integrins and local factor regulation, particularly though BMP signaling.
authors.affiliation: Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, 315 Ferst Drive NW, Atlanta, GA 30332, USA.
authors.forename: Rene
authors.initials: R
authors.lastname: Olivares-Navarrete
authors.forename: Sharon L
authors.initials: SL
authors.lastname: Hyzy
authors.forename: Jung Hwa
authors.initials: JH
authors.lastname: Park
authors.forename: Ginger R
authors.initials: GR
authors.lastname: Dunn
authors.forename: David A
authors.initials: DA
authors.lastname: Haithcock
authors.forename: Christine E
authors.initials: CE
authors.lastname: Wasilewski
authors.forename: Barbara D
authors.initials: BD
authors.lastname: Boyan
authors.forename: Zvi
authors.initials: Z
authors.lastname: Schwartz
mesh_terms: D002454:Cell Differentiation / Q000187:drug effects*; D025461:Feedback, Physiological / Q000187:drug effects*; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions / Q000187:drug effects; D016023:Integrins / Q000235:genetics / Q000378:metabolism*; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D010012:Osteogenesis / Q000187:drug effects*; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D013499:Surface Properties / Q000187:drug effects; D013816:Thermodynamics; D013997:Time Factors; D014025:Titanium / Q000494:pharmacology*; D051153:Wnt Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D016023:Integrins; D051153:Wnt Proteins; D014025:Titanium