title: Integrin alpha(5) controls osteoblastic proliferation and differentiation responses to titanium substrates presenting different roughness characteristics in a roughness independent manner.
abstract: Integrin alpha(5)beta(1) regulates osteoblast proliferation and differentiation on smooth synthetic surfaces presenting different chemistries, but it is not known whether this integrin controls osteoblast behavior on surfaces that have micron-scale rough topographies. We cultured MG63 human osteoblast-like cells on titanium substrates with three different roughness characteristics: chemically polished (PT), grit blasted and acid etched with a complex topography consisting of 20-100 mum craters and 0.5-2 mum micropits (SLA), and plasma-sprayed Ti with irregular projections (TPS). Cells spread well on PT but displayed a smaller footprint on SLA or TPS. Nuclei were larger on PT as well. alpha(5)beta(1) binding and FAK phosphorylation were greater on the rougher surfaces (TPS > SLA > PT). Antibodies against the alpha(5)beta(1) binding site on fibronectin had no effect on cell number at 3 days, but [(3)H]-thymidine incorporation was increased, suggesting that binding to fibronectin was necessary for cell cycle regulation. Antibodies to the alpha(5) subunit reduced cell number at 3 days on PT and TPS and reduced DNA synthesis on all substrates in a surface microstructure-independent manner. At 7 days, cell numbers were reduced on PT, and DNA synthesis was reduced by 50% on all surfaces. At 7 days, anti-alpha(5) antibodies caused a partial reduction in alkaline phosphatase enzyme activity on all surfaces, but this effect was independent of surface microstructure. These results indicate that surface micron-scale topography modulates alpha(5)beta(1) integrin binding and FAK activation. Signaling via alpha(5)-dependent mechanisms is required for DNA synthesis and regulation of alkaline phosphatase, but this effect is independent of surface microstructure.
authors.affiliation: Department of Biomedical Engineering, University of Florida, Gainesville, Florida, USA.
authors.forename: B G
authors.initials: BG
authors.lastname: Keselowsky
authors.forename: L
authors.initials: L
authors.lastname: Wang
authors.forename: Z
authors.initials: Z
authors.lastname: Schwartz
authors.forename: A J
authors.initials: AJ
authors.lastname: Garcia
authors.forename: B D
authors.initials: BD
authors.lastname: Boyan
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D001672:Biocompatible Materials / Q000494:pharmacology*; D002453:Cell Cycle; D002454:Cell Differentiation; D002460:Cell Line; D049109:Cell Proliferation; D004247:DNA / Q000096:biosynthesis; D005353:Fibronectins / Q000378:metabolism; D051417:Focal Adhesion Kinase 1 / Q000378:metabolism; D006801:Humans; D039081:Integrin alpha5beta1 / Q000378:metabolism; D039564:Integrin alphaV / Q000378:metabolism / Q000502:physiology*; D010006:Osteoblasts / Q000166:cytology* / Q000187:drug effects; D015398:Signal Transduction; D013499:Surface Properties; D014025:Titanium / Q000494:pharmacology*
chemical_list: D001672:Biocompatible Materials; D005353:Fibronectins; D039081:Integrin alpha5beta1; D039564:Integrin alphaV; D004247:DNA; D014025:Titanium; D051417:Focal Adhesion Kinase 1; D000469:Alkaline Phosphatase