Improvement of Bone Formation in Rats with Calvarial Defects by Modulating the Pore Size of Tricalcium Phosphate Scaffolds

The use of multi-porous scaffolds for bone tissue engineering has been shown to improve osteogenesis. Although the exact mechanisms by which these scaffolds promote new bone formation have not yet been recognized well, related hypotheses can be found in many previous studies. The aim of this study was to examine the influence of the modulation of the pore size of beta- TCP ceramics on osteogenic differentiation in rats with calvarial defects. Treatments with macro- and meso-sized particles of NaCl, which was used as a porogen, were carried out during scaffold manufacturing, and the pore sizes of the beta-TCP scaffolds were measured by SEM. New bone formation was evaluated by Micro-CT, H&E staining, and immuno-histochemical analysis at week 4 after the operation. It was observed that the multi porosity of beta-TCP ceramics was controlled by treating the scaffolds with NaCl particles of two sizes (500-800 mu m and 10-50 mu m) during the firing process. Histological and immunohistochemical analysis of type 1 collagen and osteocalcin protein expression showed that the new bone formation and mineralization in case of the multi-porous beta-TCP ceramics comprising macro-and meso-sized pores were significantly higher than those in case of single porous macro- or meso-sized scaffolds. In conclusion, the distribution and size of the pores, as well as the surface structure of the scaffolds, may play an important role for osteogenic differentiation in vivo.