Engineering microdent structures of bone implant surfaces to enhance osteogenic activity in MSCs

- Arrays of microdents regulate functions of mesenchymal stem cells.
- Denser arrays of smaller microdents cause lower cell spreading and proliferation.
- Denser arrays of smaller microdents cause a higher level of calcified matrix.

Problems persist with the integration of hip and dental implants with host bone tissues, which may result in long-term implant failure. Previous studies have found that implants bearing irregular surfaces can facilitate osseointegration. An improvement to this approach would use implant surfaces harboring a well-defined surface microstructure to decrease variability in implant surfaces. In this study, we tested whether well-defined surfaces with arrays of microdents (each with depth approximately 3 µm) significantly affected the morphology, proliferation, and osteogenic activity of mesenchymal stem cells (MSCs). Arrays of microdents tested had diameters of 9 µm, 12 µm, and 18 µm, while spacing between arrays ranged from 8 µm to 34 µm. Effects on MSC morphology (cell spreading area) and proliferation were also quantified, with both significantly decreasing on micropatterned surfaces (p<0.05) on smaller and denser microdents. In contrast, MSCs were found to deposit more calcified matrix on smaller and denser arrays of microdents. MSCs on a pattern with arrays of microdents with a diameter of 9 µm and a spacing 8 µm deposited 3-4 times more calcified matrix than on a smooth surface (p<0.05). These findings show that well-defined surface microtopographies promote osteogenic activity, which can be used on implant surfaces to improve integration with the host bone tissue.