Square prism micropillars improve osteogenicity of poly(methyl methacrylate) surfaces

Osteogenicity and osteointegration of materials is one of the key elements of the success of bone implants. Poly(methyl methacrylate) (PMMA) is the basic compound of bone cement and has been widely investigated for other orthopedic applications, but its poor osteointegration and the subsequent loosening of implant material limits its widespread use as bone implants. Micropillar features on substrate surfaces were recently reported to modulate cell behavior through alteration of cell morphology and promotion of osteogenesis. Utilization of this pillar-decorated topography may be an effective approach to enhance osteogenicity of polymeric surfaces. The aim of this study was to investigate the effect of cell morphology on the micropillar features on attachment, proliferation, and osteogenic activity of human osteoblast-like cells. A series of solvent cast PMMA films decorated with 8 µm high square prism micropillars with pillar width and interpillar distances of 4, 8 and 16 µm were prepared from photolithographic templates, and primary human osteoblast-like cells (hOB) isolated from bone fragments were cultured on them. Micropillars increased cell attachment and early proliferation rate compared to unpatterned surfaces, and triggered distinct morphological changes in cell body and nucleus. Surfaces with pillar dimensions and gap width of 4 µm presented the best osteogenic activity. Expression of osteogenic marker genes was upregulated by micropillars, and cells formed bone nodule-like aggregates rich in bone matrix proteins and calcium phosphate. These results indicated that micropillar features enhance osteogenic activity on PMMA films, possibly by triggering morphological changes that promote the osteogenic phenotype of the cells.