Rough surface topography enhances the activation of Wnt/β-catenin signaling in mesenchymal cells

It is known that the roughness of titanium surfaces affects cell proliferation and differentiation. However, the mechanisms mediating the cellular responses to surface topography are only partially understood. The present study investigated whether Wnt canonical signaling, an important pathway in determining cell fate, is modulated by surface roughness. This study analyzed the behavior of the murine C2C12 mesenchymal cell line on polished or acid-etched, sand-blasted (SLA) commercially pure titanium. When we transfected cells with Wnt3a or wild-type beta-catenin and a reporter construct, we found that stimulation of Wnt canonical signaling was enhanced in cells on SLA surfaces. Moreover, more beta-catenin translocated to the nucleus in cells on SLA surfaces after stimulation with Wnt3a as evidenced by immunofluorescence. However, when cells were transfected with constitutively active S33Y beta-catenin mutant, no difference was observed between the groups. Higher levels of transcripts of Wnt target genes were detected in C2C12 cells cultured on SLA surfaces following transfection with Wnt3a, but the expression of a gene regulating beta-catenin degradation, Axin 2, was reduced on SLA surfaces. Inhibition of beta-catenin mediated transcription by dnTCF in murine osteoblastic MC3T3 cells, reversed the effects of topography on cell differentiation. Taken together, these results show that surface roughness modulates the responsiveness of mesenchymal cells to Wnt3a, that this requires the control of beta-catenin degradation, and that the control of beta-catenin signaling by surface topography is accountable for at least part of the effects of surface on cell differentiation. (C) 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 95A: 682-690, 2010.