Bone marrow mesenchymal stem cell functions are stimulated by oxidized titanium surfaces

The aim of this study was to analyze the features of a novel oxidized titanium implant surface and to evaluate its effect on the response of human bone marrow mesenchymal stem cells (BM-MSC). 10x10x1 mm turned (control) and oxidized (test) titanium samples (P.H.I. s.r.l., San Vittore Olona, Milano, Italy) were examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM) and characterized by height, spatial and hybrid roughness parameters. Primary cultures of BM-MSC were seeded on titanium samples and cell morphology, adhesion, proliferation and osteogenic differentiation, in terms of alkaline phosphatase activity, osteocalcin synthesis and extracellular matrix mineralization, were evaluated At SEM and AFM analyses, control and test surfaces appeared considerably different: turned samples were grooved, whereas oxidized surfaces showed a more complex micro- and nano-scaled texture, as evidenced by roughness parameters. At 6 hours from the plating, cell adhesion and osteogenic parameters were greater on oxidized (p<0.05 at least) vs turned surfaces, whereas the 7-d cell proliferation rate was similar on both samples. Although both control and test samples were in the range of average roughness proper of smooth surfaces, they exhibited significantly different topographic properties in terms of height, spatial and, mostly, of hybrid parameters. Furthermore, oxidized surfaces enhanced BM-MSC adhesion and differentiation, and this could be due to the different structure at micro and nano-scale levels.