Investigating the Roles of Matrix Nanotopography and Elasticity in the Osteogenic Differentiation of Mesenchymal Stem Cells.

[摘要] We used substrates of poly(methyl methacrylate) (PMMA) to investigate the influence of nanotopography on the osteogenic phenotype of mesenchymal stem cells (MSCs), focusing on their ability to produce mineral similar to bone. Topography induced anisotropy in contact angles and surface free energy (SFE).Smooth PMMA had an SFE of 40 mN/m. Topographic surfaces had elevated and reduced SFEs when measuring parallel (up to ~45 mN/m ) or perpendicular to the gratings (as low as ~31 mN/m). Topography influenced alignment and enhanced MSC proliferation after 14 days of culture. Focal adhesion size was influenced after 7 days. Calcium deposition was not increased after 21 days. Ca: P ratios were similar to native mouse bone on films with gratings of 415 nm width and 200 nm depth (G415) and 303 nm width and 190 nm depth (G303).Notably, all surfaces had Ca:P ratios significantly lower than G415 films (less than 1.39).We used thin films of poly(ethylene glycol diacrylate) (PEGDA) with nanoscale gratings and tunable elasticity to investigate the potential synergistic effect on the osteogenic phenotype of MSCs. Three distinct moduli were used having a shear storage modulus of ~64, 300, and 530 kPa respectively. Topography did not influence cell alignment nor did the combination of matrix topography and elasticity enhance the calcium deposition or Ca:P ratios. Collagen I density (5 or 50 µg/mL) did not significantly influence calcium deposition.These data demonstrate that nanotopographic PMMA films, mimicking the architecture of bone, do not enhance calcium levels in mineral deposited by hMSCs. We showed that increased focal adhesion size on PMMA nanotopography is insufficient by itself to drive increased calcium deposition. Reports in literature rarely quantify changes in focal adhesions with changes in mineral quantity and composition. Similarly, an in vivo report suggests that topography does not enhance osteogenesis. In the first known attempt to combine adhesion ligand concentration (Col I) to nanogratings on surfaces with varied mechanical properties, these inputs were insufficient to synergistically enhance an osteogenic phenotype in MSCs. We highlight the importance of studying functional output rather than minor markers as function is a greater indicator of differentiation.

[发布机构] University of Michigan

[效力级别] Nanotopography

[关键词] Orthopedic Implants;Nanotopography;Mesenchymal Stem Cells;Mineralization;Matrix Mechanics;Surface Free Energy;Biomedical Engineering;Materials Science and Engineering;Engineering;Health Sciences;Science;Materials Science and Engineering