Matsuoka H, Akiyama H, Okada Y, Ito H, Shigeno C, Konishi J, Kokubo T, Nakamura T
Department of Orthopaedic Surgery, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan.
J Biomed Mater Res. 1999 Nov;47(2):176-88. doi: 10.1002/(sici)1097-4636(199911)47:2<176::aid-jbm7>3.0.co;2-z.
We analyzed the mechanisms of the efficient bone formation on the osteoconductive surface of apatite- and wollastonite-containing glass-ceramic (AW) by using an in vitro system. AW releases Ca ions and bonds to bone via a submicron-thick hydroxycarbonate apatite (HCA) layer. AW disks were conditioned with simulated body fluid (SBF) to grow HCA layers, and the amount of released Ca ion was regulated by modulating the conditioning time from 24 to 240 h. Surface-transformed AW disks increased alkaline phosphatase (AP) activity in osteoblastic ROS17/2.8 cells by 1.5- to threefold over unconditioned disks. AW disks conditioned for 24 h [AW(24)], which had a homogeneous, submicron-thick apatite layer and increased extracellular ionized Ca concentration (Ca(2+)) in the culture medium to the greatest extent, enhanced the AP activity the most. High Ca(2+) promoted osteogenic differentiation in ROS17/2.8 cells: It increased AP activity in a dose-dependent manner by up to 1.6-fold, and up-regulated the expression of AP, osteocalcin (OC), and transforming growth factor-beta1 mRNAs in dose- and time-dependent manners. AW(24) enhanced AP activity in ROS17/2.8 cells as much as AW disks conditioned with SBF containing serum to exhibit in vivo surface-structure changes. AW(24) increased AP activity in ROS17/2.8 cells by 1.6-fold and enhanced the expression of AP and OC mRNAs significantly, compared with sintered hydroxyapatite (HA). After implantation of AW and HA in the distal metaphyses of rabbit femurs, thin, newly formed bone lined with cuboidal, osteoblast-like cells was characteristically observed adjacent to the AW surface within 8 days. These results provide evidence for the hypothesis that AW stimulates bone formation on its surface by increasing Ca(2+) to promote the HCA layer formation and the differentiation of osteogenic cells.
我们通过体外系统分析了含磷灰石和硅灰石的微晶玻璃（AW）的骨传导表面上高效骨形成的机制。AW通过亚微米厚的羟基碳酸磷灰石（HCA）层释放钙离子并与骨结合。用模拟体液（SBF）处理AW圆盘以生长HCA层，并通过将处理时间从24小时调节至240小时来调节钙离子的释放量。与未处理的圆盘相比，表面转化的AW圆盘使成骨细胞ROS17/2.8细胞中的碱性磷酸酶（AP）活性提高了1.5至3倍。处理24小时的AW圆盘[AW(24)]具有均匀的亚微米厚磷灰石层，并在最大程度上提高了培养基中的细胞外离子钙浓度(Ca(2+))，其对AP活性的增强作用最大。高Ca(2+)促进了ROS17/2.8细胞的成骨分化：它以剂量依赖的方式将AP活性提高了1.6倍，并以剂量和时间依赖的方式上调了AP、骨钙素（OC）和转化生长因子-β1 mRNA的表达。AW(24)使ROS17/2.8细胞中的AP活性增强程度与用含血清的SBF处理以呈现体内表面结构变化的AW圆盘相同。与烧结羟基磷灰石（HA）相比，AW(24)使ROS17/2.8细胞中的AP活性提高了1.6倍，并显著增强了AP和OC mRNA的表达。将AW和HA植入兔股骨远端干骺端后，在8天内可在AW表面附近观察到特征性的现象，即有一层由立方形成骨细胞样细胞衬里的薄新生骨。这些结果为以下假设提供了证据：AW通过增加Ca(2+)来刺激其表面的骨形成，从而促进HCA层的形成和成骨细胞的分化。
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