Usefulness of a novel hydroxyapatite fiber as a scaffold of stem cells for bone regeneration in spinal fusion surgery

用载有重组人骨形态发生蛋白-2的磷灰石纤维网(AFM)进行大鼠脊柱融合。植骨融合率为100%，提示AFM在脊柱融合术中可能是一种有效的骨替代材料。然而，由于AFM是脆弱的，我们需要小心操作处理。为了提高磷灰石的力学性能，我们用肌醇磷酸修饰的羟基磷灰石颗粒(IP_6-HAP)制备了包埋型磷灰石骨水泥。本研究的目的是开发IP_6-HAP作为骨移植材料。在2006年和2007年，我们进行了如下研究：1.将MC3T3-E1细胞接种于IP_6-HAP上进行培养。方法：1.细胞培养后，计数贴壁细胞数，检测初始贴壁效率和细胞增殖情况。将IP6-HAPS植入兔胫骨内，并与Biopex[0！R]-R(日本宾得公司)对照。24周内处死动物取材，取周围骨标本进行组织学观察。实验一，在IP6-HAP上培养的MC3T3-E1细胞的细胞贴壁率和细胞增殖率均低于对照组(聚苯乙烯12孔板)；扫描电子显微镜观察细胞形态显示，IP_6-Hap上的细胞在7d内几乎达到融合。实验2发现，与Biopex[0！R]-R相比，IP_6-HAPS表面有成熟骨形成。新生骨与骨水泥表面紧密接触，没有任何纤维组织层介入的迹象。这一结果表明，IP_6-HAP对活骨具有良好的骨传导性，说明IP_6-HAP没有细胞毒性。此外，IP6-HAP的硬组织反应与Biopex[0！R]-R相似。因此，IP_6-HAP是一种有价值的新型植骨材料。

Spinal fusion was conducted in rats using apatite fiber mesh (AFM) loaded with rhBMP-2. The percentage of fusion rate was 100% and concluded that AFM might be effective as a bone substitute in spinal fusion operation. However, as AFM was fragile, we needed to operate carefully on handling. In order to enhance the mechanical properties, we have developed chelete-setting apatite cement using hydroxyapatite particles surfaced-modified with inositol phosphate (IP_6-HAp). The aim of this study is to develop IP_6-HAp as a material for bone grafting. In 2006 and 2007, we have done some studies listed below.1. MC3T3-E1 cells were seeded and cultured on IP_6-HAp. After cell culture, the cell number attached on them was counted to examine initial cell-attachment efficiency and cell proliferation.2. IP_6-HAps were implanted into tibiae of rabbits, together with a control of Biopex[○!R]-R (PENTAX Corporation, Japan). Within 24 weeks after implantation, the rabbits were sacrificed to retrieve the specimens with the surrounding bone for histological evaluation.In experiment 1, The MC3T3-E1 cells cultured on IP_6-HAp showed lower cell attachment and cell proliferation than the control (polystyrene 12-wells plate);. However, cell morphology observed by SEM showed that cells on IP_6-Hap nearly attained to be confluent for 7 days. These results demonstrate that IP_6-Hap have noncytotoxicity.In experiment 2, mature bone was seen to have formed around the surface of the IP_6-HAps as compared with Biopex[○!R]-R. The newly-formed bone was in close contact with the cement surface, without any sign of intervening fibrous tissue layer. This result indicates that IP_6-HAp has an excellent osteoconductivity to living bone.These results have shown that IP_6-HAp has noncytotoxicity. Furthermore, the hard tissue response of IP_6-HAp is shown to be similar to that of Biopex[○!R]-R. Thus, we conclude that IP_6-HAp is useful as a material for novel bone grafting.