Yuan Bo, Raucci Maria Grazia, Fan Yujiang, Zhu Xiangdong, Yang Xiao, Zhang Xingdong, Santin Matteo, Ambrosio Luigi
National Engineering Research Center for Biomaterials, Sichuan University, Chengdu 610064, China.
J Mater Chem B. 2018 Dec 21;6(47):7974-7984. doi: 10.1039/c8tb02526f. Epub 2018 Nov 20.
The control of the inflammatory response induced by the implantation of foreign biomaterials is fundamental in determining tissue healing. It has been shown that the activation of specific macrophage pathways upon contact with a biomaterial can lead either to a chronic inflammation preventing a physiological tissue repair or to an improved tissue healing. In the case of bone repair, calcium phosphate cements with good osteoconductivity properties have been successfully applied in bone defect filling and repair, but poor handling properties, insufficient viscous flow and unmatched degradation rate are still problems that remain unsolved. In this study, a strontium-doped hydroxyapatite (HA) gel was modified by integrating branched poly(epsilon-lysine) dendrons with third-generation branches exposing phosphoserine (SrHA/G3-K PS). The interaction of this material with macrophages was investigated in vitro, focusing on the secretion and gene expression of specific pro-inflammatory cytokines. Our results showed that the addition of strontium and G3-K PS to HA sol-gel could down-regulate the gene expression of inflammatory factors such as IL-1β, TNF-α and MCP-1, while increasing the gene expression of IL-6, a cytokine known for its osteogenic effect. These results were further confirmed by ELISA test of the respective protein concentrations. When exposed to supernatants of macrophage culture in the presence of strontium and G3-K PS, osteoblast viability was promoted with elevated osteogenic gene markers, in terms of OPG, ALP, OCN and COL-I. In vivo implantation experiments using an osteoporotic rat model with bone defect further confirmed that the addition of G3-K PS to HA could dramatically promote new bone regeneration. Although the introduction of strontium improved the degradation properties of the injectable materials, no positive effect on promoting in vivo bone regeneration was observed.
控制由植入外来生物材料引起的炎症反应是决定组织愈合的关键。研究表明，生物材料与巨噬细胞接触后特定巨噬细胞途径的激活，要么导致慢性炎症从而阻碍生理性组织修复，要么促进组织愈合。在骨修复方面，具有良好骨传导性能的磷酸钙骨水泥已成功应用于骨缺损填充和修复，但操作性能差、粘性流动不足以及降解速率不匹配等问题仍未解决。在本研究中，通过将带有暴露磷酸丝氨酸的第三代分支的支化聚（ε-赖氨酸）树枝状分子整合到锶掺杂羟基磷灰石（HA）凝胶中，对其进行了改性（SrHA/G3-K PS）。在体外研究了这种材料与巨噬细胞的相互作用，重点关注特定促炎细胞因子的分泌和基因表达。我们的结果表明，向HA溶胶-凝胶中添加锶和G3-K PS可以下调炎症因子如IL-1β、TNF-α和MCP-1的基因表达，同时增加IL-6的基因表达，IL-6是一种以其成骨作用而闻名的细胞因子。相应蛋白质浓度的ELISA测试进一步证实了这些结果。当在锶和G3-K PS存在的情况下暴露于巨噬细胞培养上清液时，成骨细胞活力得到促进，成骨基因标志物OPG、ALP、OCN和COL-I水平升高。使用骨质疏松性骨缺损大鼠模型进行的体内植入实验进一步证实，向HA中添加G3-K PS可以显著促进新骨再生。虽然锶的引入改善了可注射材料的降解性能，但未观察到对促进体内骨再生的积极作用。
