In vitro study of osteogenic differentiation of bone marrow stromal cells on heat-treated porcine trabecular bone blocks

This in vitro study investigated the potential of the heat-treated porcine trabecular bone block as a bone substitute for the treatment of bone defects or related diseases. Chemical, mechanical, and morphological studies of bone blocks were performed. The resultant properties were compared with the properties of currently available commercial products from bovine trabecular bones. The major component of the bone block was hydroxyapatite, and the ratio of Ca/P was 1.65-1.66. The average values of the compressive Young's modulus and the ultimate strength were 346.33 +/- 83.15 and 6.66 +/- 1.62 MPa, respectively. The pore size of the heat-treated bone blocks was approximately 300-500 microm. For the biological investigations, expanded bone marrow stromal cells (BMSCs) were isolated from the femurs of New Zealand White rabbits and were dynamically seeded into the heat-treated porcine bone block (10x10x5 mm3). Before the cells were seeded, the heat-treated porcine bone blocks were divided into two groups: collagen coated blocks (n=16) and uncoated blocks (n=16). Within each group, the blocks were again divided into two groups, depending on the culture method, i.e., static or rotating culture. Cells were cultured in the blocks for up to 6 weeks. Scanning electron microscopic examination after 4 weeks showed that the cell layers attached to the porcine bone block. Proliferation and osteogenic differentiation were analyzed by cell counting, an MTT assay, alkaline phosphatase activity, and total protein content. The deposition of extracellular substances and osteoid formation surrounded by osteoblast-like cuboidal cells were confirmed through histochemical staining and transmission electron microscopy. Based on the results of this study, we conclude that heat-treated porcine trabecular bone has great potential as a bone substitute and may even be superior to currently available commercial products.