Papers by Author: Mika Tadokoro

Abstract: Hydroxyapatite (HA) ceramics together with various kinds of osteogenic cells have been used in bone tissue engineering. It is well known that the ceramics structure and composition affect cell proliferation / differentiation. In this study, three different types of HA ceramics were used to investigate initial cell attachment followed by osteoblastic differentiation of human mesenchymal stromal cells (MSCs). The results indicated that micro-pore affected the cell attachment and porosity (pore diameter and inter-pore connection) was the key to allow spacious distribution of the viable cells in the ceramics. This study also confirmed that surface pore areas of HA ceramics support the differentiation of human MSCs and thus the ceramics have the capability to regenerate damaged bone tissue.

Abstract: In the field of tissue engineering for bone regeneration, there have been many studies that examined in the bone forming ability of the porous biomaterials with mesenchymal stem cells (MSCs). To promote the tissue engineering approach in clinical situation, there is a need for the establishment and standardization of evaluation methods for measuring the in vivo bone forming ability. In this study, we examined the seeding process using rat MSCs to ascertain whether it is a valid protocol for various materials. Our results showed that the cell seeding process for the fabrication method of MSCs/materials composite influenced the number and distribution of the MSCs in the materials, therefore the process is a key to show new bone formation which derived from the seeded MSCs. Here, we describe the detailed process which can show consistent new bone formation in pores of the materials.

Abstract: This study focused on in vivo osteogenic capability of bone marrow mesenchymal stem cells (MSCs) seeded on ceramic scaffold. Human MSCs from a single donor were seeded on hydroxyapatite porous ceramic (HAP) and were induced to the osteogenic lineage during in vitro culture condition, then the MSCs/HAP composites were implanted subcutaneously into immunodeficient rats. The cellular activities of the composites were assayed in order to evaluate the distribution and differentiation capability of seeded MSCs before and after implantation. These results showed that the new bone, after implantation, was derived from the donor MSCs, which adhered to the surface of the ceramics pore areas during in vitro culture. Therefore, the engrafted donor cells proliferated and showed continuous osteogenic differentiation within the recipients. Consequently, our study demonstrates the usefulness of MSCs/HAP composites for clinical applications.

Abstract: Cultured osteoblasts with mineralized matrix (regenerative cultured bone; RCB) have been used for patients having osseous defects. The RCB can be fabricated on various ceramic substrata using patient’s mesenchymal stem cells (MSCs) at our cell processing center (CPC). Since we have to transport the RCB for hospitals outside of our town, the RCB should maintain the cell viability for a long time. To determine a suitable condition for transportation of the RCB, stability of the RCB was analyzed by biochemical assays. Even outside CO2 incubator, the RCB kept high level of viability until 24 hours at 25°C and also showed low level of cytotoxicity for 24 hours at 37°C and 25°C. On the other hand, the RCB incubated for 24 hours at 4°C outside CO2 incubator resulted in extremely low level of viability with obvious cytotoxicity. These data indicated that stability of the RCB can be maintained for 24 hours at 37°C and 25°C, but not at 4°C. Therefore, the RCB derived from patient’s MSCs can be transported and utilized for the patients at hospitals far away from the CPC.