Skeletal stem cell physiology on functionally distinct titania nanotopographies.

Functionalisation of the surface of orthopaedic implants with nanotopographies that could stimulate in situ osteogenic differentiation of the patient's stem or osteoprogenitor cells would have significant therapeutic potential. Mesenchymal stem cell (MSC) responses to titanium substrates patterned with nanopillar structures were investigated in this study. Focal adhesions were quantified in S-phase cells, the bone-related transcription factor Runx2 was examined, osteocalcin production was noted, and Haralick computational analysis was used to assess the relatedness of the cell responses to each of the titanium substrata based on cytoskeletal textural features. Metabolomics was used as a novel means of assessing cellular responses to the biomaterial substrates by analysing the global metabolite profile of the cells on the substrata, and shows promise as a technique with high data yield for evaluating cell interactions with materials of different surface chemistry or topography. The cell response to 15 nm high nanopillars was distinct, consistent with a transition from a more quiescent phenotype on the planar substrate, to an 'active' phenotype on the pillars. These studies illustrate the potential for clinically relevant titania nanopillared substrata to modulate MSCs, with implications for orthopaedic device design and application.