Nanopit-induced osteoprogenitor cell differentiation: the effect of nanopit death

We aimed to assess osteogenesis in osteoprogenitor cells by nanopits and to assess optimal feature depth. Topographies of depth 80 nm, 220 nm and 333 nm were embossed onto polycaprolactone (PCL) discs. Bone marrow-derived mesenchymal stromal cells were seeded onto PCL discs, suspended in media and incubated. Samples were fixed after three and 28 days. Cells were stained for the adhesion molecule vinculin and the osteogenic transcription factor RUNX2 after three days. Adhesion was lowest on planar controls and it was the shallowest, 80 nm deep pits that supported optimal adhesion formation. 80 nm and 220 nm deep pits induced most RUNX2 accumulation. After 28 days, osteocalcin and osteopontin expression were used as markers of osteoblastic differentiation. 220 nm deep pits produced cells with the highest concentrations of osteopontin and osteocalcin. All topographies induced higher expression levels than controls. We demonstrated stimulation of osteogenesis in a heterogeneous population of mesenchymal stromal cells. All nanopit depths gave promising results with an optimum depth of 220 nm after 28 days. Nanoscale modification of implant surfaces could optimise fracture union or osteointergration