Surface Nanofeature Effects on Titanium-Adherent Human Mesenchymal Stem Cells

Purpose: Hydrofluoric acid treatment of moderately rough commercially pure titanium produced by titanium oxide (TiO2) grit blasting (OsseoSpeed) results in a surface with nanofeatures. The aim of this project was to better understand the effect of surface nanotopography on adherent osteoblastic differentiation. Materials and Methods: Human mesenchymal stem cells were grown on TiO2 grit-blasted and hydrofluoric acid-treated/TiO2 grit-blasted titanium coins for 1 to 28 days. The nature of the surfaces was evaluated using scanning electron microscopy, optical interferometry, and x-ray photoelectron spectrometry. Osteoblastic differentiation was measured using real-time polymerase chain reaction measurement of more than 80 mineralized tissue-associated, protein-encoding mRNAs. Results: Hydrofluoric acid-treated surfaces displayed nanofeatures of 100 nm in diameter and maintenance of micron-level topography. Adherent cell osteoblastic differentiation occurred on both surfaces but took place more rapidly and to a greater extent on hydrofluoric acid-treated surfaces. This was revealed by earlier, higher, and sustained levels of osteoinductive transcription factors (RUNX-2, SMADs), growth factors (insulin-like growth factor 2, bone morphogenetic proteins), and bone matrix proteins. Conclusions: The superimposition of nanofeatures on a moderately rough commercially pure titanium surface is associated with marked osteoinduction and osteogenesis of adherent mesenchymal stem cells. The role of nanotopography in directing adherent cell behavior should be fully investigated. Keywords: commercially pure titanium, gene expression, human mesenchymal stem cell, nanotopography, osteoinduction, real-time polymerase chain reaction