Effect of mechanical stress on differentiation of mouse mesenchymal stem cells seeded into an octacalcium phosphate-gelatin scaffold

We report the extent of mechanical stress on a bioactive three-dimensional scaffold that can induce differentiation of seeded osteoblastic cells in vitro. Mouse mesenchymal stem D1 cells were seeded on a porous spongy scaffold consists of octacalcium phosphate (OCP) and gelatin (Gel) composite, which was previously proven to be a sufficient bone-replaceable material in vivo. The cellular activity was determined after loading of uni-axial compression by deforming a 5 mm ring-shaped, cell-seeded OCP/Gel composite in the range of 1-3 mm (corresponding to 20-60% of the material thickness) using a cyclic mechanical loading device designed for this study. The extent of the deformation did not affect the proliferation. However, enhancement of differentiation marker genes, such as osteopontin and osteoclacin, occurred after the composite was deformed by just 20%. These results suggest that osteoblastic differentiation of D1 cells is promoted if suitable mechanical stress is provided, which indicates biological relevance of the bone regenerative properties of this material under mechanical stress that were shown in a previous in vivo study.