Department of Orthopaedic Surgery, Nara Medical University, Shijocho 840, 634-8521, Kashihara, Nara, Japan.
Department of Health and Welfare Services, National Institute of Public Health, 2-3-6 Minami, 351-0197, Wako, Saitama, Japan.
BMC Musculoskelet Disord. 2021 Aug 9;22(1):673. doi: 10.1186/s12891-021-04563-4.
β-Tricalcium phosphate (β-TCP) is a popular synthetic bone graft substitute with excellent osteoconductive properties and bioabsorbability. However, its osteoinductive properties are inferior to those of autologous or allogeneic bone. Trace elements such as strontium (Sr), silica (Si), and zinc (Zn) have been reported to promote osteogenesis in materials. In this study, we aimed to determine whether a Si/Zn-substituted Sr apatite coating of β-TCP could enhance osteoinductive properties.
The apatite-coated β-TCP disks were prepared using nanoparticle suspensions of silicate-substituted Sr apatite (SrSiP) or silicate- and Zn-co-substituted Sr apatite (SrZnSiP). Bone marrow mesenchymal cells (BMSCs) from rat femur were cultured and subsequently seeded at a density of 1.0 × 10/cm onto apatite-coated and non-coated β-TCP disks. In vitro, the β-TCP disks were then placed in osteogenic medium, and lactate dehydrogenase (LDH) activity was measured from supernatants after culture for 2 days. Additionally, after culture for 14 days, the mRNA expression of genes encoding osteocalcin (OC), alkaline phosphatase (ALP), bone morphogenetic protein-2 (BMP-2), and vascular endothelial growth factor (VEGF) was evaluated by qRT-PCR. In vivo, the β-TCP disks were transplanted subcutaneously into rats that were sacrificed after 4 weeks. Then, the harvested disks were evaluated biochemically (ALP activity, OC content, mRNA expression of OC, ALP, BMP-2, and VEGF measured by qRT-PCR), radiologically, and histologically.
Significantly higher mRNA expression of almost all evaluated osteogenic and angiogenic genes was observed in the SrZnSiP and SrSiP groups than in the non-coated group, with no significant cytotoxicity elicited by the apatite coating in vitro. Moreover, in vivo, the SrZnSiP and SrSiP groups showed significantly higher osteogenic and angiogenic gene expression and higher ALP activity and OC content than the non-coated group (P < 0.05). Radiological and histopathological findings revealed abundant bone formation in the apatite-coated group.
Our findings indicate that apatite coating of β-TCP improves osteoinductive properties without inducing significant cytotoxicity.
β-磷酸三钙（β-TCP）是一种具有良好骨传导性和生物可吸收性的常用合成骨移植替代物。然而，其成骨诱导性能劣于自体或同种异体骨。据报道，微量元素如锶（Sr）、硅（Si）和锌（Zn）可促进材料中的成骨作用。在本研究中，我们旨在确定β-TCP 的 Si/Zn 取代 Sr 磷灰石涂层是否可以增强成骨诱导特性。
使用硅取代 Sr 磷灰石（SrSiP）或硅和 Zn 共取代 Sr 磷灰石（SrZnSiP）的纳米颗粒悬浮液制备磷灰石涂层的 β-TCP 圆盘。从大鼠股骨骨髓间充质细胞（BMSCs）培养物中培养细胞，并随后以 1.0×10/cm 的密度接种于磷灰石涂层和未涂层的 β-TCP 圆盘上。在体外，将β-TCP 圆盘置于成骨培养基中，培养 2 天后从上清液中测量乳酸脱氢酶（LDH）活性。此外，培养 14 天后，通过 qRT-PCR 评估编码骨钙素（OC）、碱性磷酸酶（ALP）、骨形态发生蛋白-2（BMP-2）和血管内皮生长因子（VEGF）的基因的 mRNA 表达。在体内，将β-TCP 圆盘皮下移植到大鼠中，4 周后处死大鼠。然后，通过生物化学（ALP 活性、OC 含量、qRT-PCR 测定 OC、ALP、BMP-2 和 VEGF 的 mRNA 表达）、放射学和组织学评估收获的圆盘。
与未涂层组相比，SrZnSiP 和 SrSiP 组几乎所有评估的成骨和血管生成基因的 mRNA 表达均显著升高，体外磷灰石涂层无明显细胞毒性。此外，在体内，SrZnSiP 和 SrSiP 组的成骨和血管生成基因表达以及 ALP 活性和 OC 含量均显著高于未涂层组（P<0.05）。放射学和组织病理学检查结果显示，磷灰石涂层组有大量骨形成。
我们的研究结果表明，β-TCP 的磷灰石涂层可改善成骨诱导性能，而不会引起明显的细胞毒性。
