Reconstruction of Tissue-Engineered Bone Using an Apatite-Fiber Scaffold, Rat Bone Marrow Cells and Radial-Flow Bioreactor: Optimization of Flow Rate in Circulating Medium

Abstract

We have successfully developed porous apatite-fiber scaffolds (AFSs) which have three-dimensional (3D) inter-connected pores; subsequently, we have clarified that the AFSs have an excellent bioactivity on the basis of both in vitro and in vivo evaluations. In addition, we have reconstructed the tissue-engineered bone with 3D structure through 3D-cell culture of mesenchymal stem cells derived from rat bone marrow (RBMC) using the AFS settled into the radial-flow bioreactor (RFB), and examined effect of flow rate of medium in the RFB on the differentiation of osteoblasts in tissue-engineered bone. Aim in the present work is to establish of the optimal conditions of flow rate in this construction method of 3D tissue-engineered bone. The flow rates were set to 0.4, 1.3, 6.3, 11.5 and 16.5 cm3min-1; tissue-engineered bones cultured by the individual flow rates are defined as bones#1~#5. The level of differentiation of osteoblasts in all the bones#1~#5 was examined by determining the content of two kinds of differentiation maker into osteoblast, alkaline phosphatase (ALP) for initial/middle stage and osteocalcin (OC) for late stage. The ALP activity normalized for DNA content of bone#3 showed the highest value among all of them. Moreover, the OC amount normalized for DNA content of bone#3 also indicated the highest among all the examined samples. These results demonstarate that the flow rate of 6.3 cm3min-1 may promote the differentiation into osteoblast. In conclusion, we determined that this flow rate was the optimal conditions for the bone regeneratrion in RFB.