TY - JOUR
T1 - The roles of Wnt signaling modulators Dickkopf-1 (Dkk1) and Dickkopf-2 (Dkk2) and cell maturation state in osteogenesis on microstructured titanium surfaces
AU - Olivares-Navarrete, Rene
AU - Hyzy, Sharon
AU - Wieland, Marco
AU - Boyan, Barbara D.
AU - Schwartz, Zvi
PY - 2010/3/1
Y1 - 2010/3/1
N2 - Osteoblast differentiation on tissue culture polystyrene (TCPS) requires Wnt/beta-catenin signaling, regulating modulators of the Wnt pathway like Dickkopf-1 (Dkk1) and Dkk2. Osteoblast differentiation is increased on microstructured titanium (Ti) surfaces compared to TCPS; therefore, we hypothesized that surface topography and hydrophilicity affect Dkk1 and Dkk2 expression and that their roles in osteoblast differentiation on Ti differs depending on cell maturation state. Human osteoblast-like MG63 cells, normal human osteoblasts (HOBs), and human mesenchymal stem cells (MSCs), as well as MG63 cells stably silenced for Dkk1 or Dkk2 were grown for 6 days on TCPS and Ti surfaces (PT [Ra<0.2 μm], SLA [Ra = 4 μm], modSLA [hydrophilic-SLA]). Dkk1 and Dkk2 mRNA and protein increased on SLA and modSLA for all cell types, but exogenous rhDkk1 and rhDkk2 affected MSCs differently than MG63 cells and HOBs. Silencing Dkk1 reduced MG63 cell number on TCPS and PT, but increased differentiation on these substrates. Silencing Dkk2 reduced stimulatory effects of SLA and modSLA on osteoblast differentiation; Dkk2 but not Dkk1 restored these effects. Antibodies to Dkk1 or Dkk2 specifically blocked substrate-dependent changes caused by the proteins, demonstrating their autocrine action. This indicates major roles for Dkk1 and the canonical Wnt pathway in early-stage differentiation, and for Dkk2 and Wnt/Ca2+-dependent signaling in late-stage differentiation on microstructured and hydrophilic surfaces, during osseointegration.
AB - Osteoblast differentiation on tissue culture polystyrene (TCPS) requires Wnt/beta-catenin signaling, regulating modulators of the Wnt pathway like Dickkopf-1 (Dkk1) and Dkk2. Osteoblast differentiation is increased on microstructured titanium (Ti) surfaces compared to TCPS; therefore, we hypothesized that surface topography and hydrophilicity affect Dkk1 and Dkk2 expression and that their roles in osteoblast differentiation on Ti differs depending on cell maturation state. Human osteoblast-like MG63 cells, normal human osteoblasts (HOBs), and human mesenchymal stem cells (MSCs), as well as MG63 cells stably silenced for Dkk1 or Dkk2 were grown for 6 days on TCPS and Ti surfaces (PT [Ra<0.2 μm], SLA [Ra = 4 μm], modSLA [hydrophilic-SLA]). Dkk1 and Dkk2 mRNA and protein increased on SLA and modSLA for all cell types, but exogenous rhDkk1 and rhDkk2 affected MSCs differently than MG63 cells and HOBs. Silencing Dkk1 reduced MG63 cell number on TCPS and PT, but increased differentiation on these substrates. Silencing Dkk2 reduced stimulatory effects of SLA and modSLA on osteoblast differentiation; Dkk2 but not Dkk1 restored these effects. Antibodies to Dkk1 or Dkk2 specifically blocked substrate-dependent changes caused by the proteins, demonstrating their autocrine action. This indicates major roles for Dkk1 and the canonical Wnt pathway in early-stage differentiation, and for Dkk2 and Wnt/Ca2+-dependent signaling in late-stage differentiation on microstructured and hydrophilic surfaces, during osseointegration.
KW - Cell signaling
KW - Mesenchymal stem cell
KW - Osseointegration
KW - Osteoblast
KW - Surface roughness
KW - Titanium
UR - http://www.scopus.com/inward/record.url?scp=74449086192&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=74449086192&partnerID=8YFLogxK
U2 - 10.1016/j.biomaterials.2009.11.071
DO - 10.1016/j.biomaterials.2009.11.071
M3 - Article
C2 - 20004015
AN - SCOPUS:74449086192
VL - 31
SP - 2015
EP - 2024
JO - Biomaterials
JF - Biomaterials
SN - 0142-9612
IS - 8
ER -