Abstract
BackgroundThe effects of microchannel diameter in hydroxyapatite (HAp) substrates on osteoblast behavior were investigated in this study. Microchannels of 100, 250 and 500 μm diameter were created on hydroxyapatite disks. The changes in osteoblast precursor growth, differentiation, extra cellular matrix (ECM) secretion and cell attachment/orientation were investigated as a function of microchannel diameter.ResultsCurvature did not impact cellular differentiation, however organized cellular orientation was achieved within the 100 and 250 μm microchannels (mc) after 6 days compared to the 12 days it took for the 500mc group, while the flat substrate remained disorganized. Moreover, the 100, 250 and 500mc groups expressed a specific shift in orientation of 17.45°, 9.05°, and 22.86° respectively in 24 days. The secreted/mineralized ECM showed the 100 and 250mc groups to have higher modulus (E) and hardness (h) (E = 42.6GPa; h = 1.6GPa) than human bone (E = 13.4-25.7GPa; h = 0.47-0.74GPa), which was significantly greater than the 500mc and control groups (p < 0.05). It was determined that substrate curvature affects the cell orientation, the time required for initial response, and the shift in orientation with time.ConclusionsThese findings demonstrate the ability of osteoblasts to organize and mineralize differentially in microchannels similar to those found in the osteons of compact bone. These investigations could lead to the development of osteon-like scaffolds to support the regeneration of organized bone.
Highlights
Natural bone achieves much of its mechanical strength through cortical bone, through the organization of its osteons
Even though primary Mesenchymal cells are pluripotent compared to Human Fetal Osteoblasts (HFObs) which are committed to the osteogenic lineage, they were not used because the objective of this study was to investigate the effect of local micro-architecture on the matrix production, organization and maturation of osteoblast-like cells, rather than to investigate the commitment of progenitor cells to an osteoblast-like phenotype
Characterization of the Hap disks Reproducible disks with longitudinal curved microchannels spanning the entire disk were created using the casting technique. This novel geometry was analyzed under scanning electron microscopy (SEM) and constant microchannel diameter was seen throughout the four disk groups (Figure 5)
Summary
Natural bone achieves much of its mechanical strength through cortical bone, through the organization of its osteons. While Col-I and other organic molecules make up 70% of total bone composition, the remaining 30% is inorganic, composed of bone minerals, nano-size crystals of hydroxyapatite (HAp) [1]. The secretion of Col-I along different orientations, followed by the deposition of bone minerals, gives cortical bone its high compressive strength and toughness [3]. The effects of microchannel diameter in hydroxyapatite (HAp) substrates on osteoblast behavior were investigated in this study. The changes in osteoblast precursor growth, differentiation, extra cellular matrix (ECM) secretion and cell attachment/orientation were investigated as a function of microchannel diameter
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