体内微环境pH在骨质疏松性骨折修复过程中对干细胞及破骨细胞的影响 -基于硅硼体系材料表面可控pH研究

Currently, there is lack of clinically approved biomaterials specifically tailored for application in osteoporotic bones. The major barrier that influences them to get a better performance is that they usually have an unbalanced bone remodeling condition. Therefore, the key issue for developing biomaterials specific to osteoporotic use is to re-establish normal bone regeneration at the fracture site: on the one hand, increasing osteoblastic differentiation from bone marrow stronmal cells; on the other hand, suppressing abnormal osteoclasts activity. .It was found that the osteoblast viability was significantly enhanced with an increase in pH, to an optimum level at around pH 8–8.5. We further found that weak alkaline conditions stimulated osteoporotic rat bone marrow stromal cells (oBMSCs) differentiation, while inhibiting the formation of osteoclasts. In vivo, the microenvironment pH (μe-pH) were significantly increased after biodegradable alkaline materials implantation. As a result, appropriately designed biomaterials, which create an ideal ambient alkaline environment for bone regeneration, may be crucial aspects for bone substitutes. .In this study, we will firstly achieve the modulation of an alkaline condition by degradation of borosilicate material system; secondly, the influence of μe-pH on BMSCs attachment, proliferation and differentiation, and on osteoclasts differentiation and activity will be studied; At last, a special attempt will be addressed on evaluating μe-pH change on the behavior of TRAP+ osteoclasts activity on the early stage of bone defect regeneration process. Therefore, μe-pH may be used as one of the indices for biomaterial evaluation to better guide the design of such materials, not only in particular for osteoporotic bone defect repair but also in any situation where osseointegration is required.

即今为止，临床上仍然缺乏针对改善骨质疏松病人骨稳态失衡的生物材料。与一般创伤骨缺损不同，为骨质疏松病人设计的材料必须考虑到疾病的特点：即通过调节干细胞及破骨细胞的活性，恢复骨折部位的正常骨再生能力，实现对骨折和骨质疏松的双重治疗。本项目组发现最有利于前成骨细胞增殖的环境在pH 8~8.5；进而发现可降解生物材料植入体内后，材料表面微环境pH会显著改变。此微环境的存在可能对材料植入早期阶段干细胞及破骨细胞的活性产生直接影响，并最终影响骨修复的效率。因此，本课题以硅酸盐和硼酸盐等降解偏碱性的材料为研究载体，研究材料表面离子释放与微环境pH值的关系；其次，探求材料表面酸碱效应对骨髓基质干细胞粘附、增殖、分化及对破骨细胞分化、活力的影响；最后，研究骨缺损修复早期，环境pH值的改变对早期破骨细胞活性，类骨质的生成等的影响。为骨质疏松性骨再生机制研究提供新思路，研发针对骨质疏松性骨折骨修复所需的材料。

骨再生材料微环境与细胞微环境是研究骨再生医学的基础，也是研究病理条件下骨再生修复的重要途经。本项目围绕材料体内降解行为学进行系统而广泛的研究，明确了体内pH变化与材料降解行为学之间的关系。探明了pH在体内成骨机制及调控骨再生功能作用，发现了在材料植入骨缺损部位营造微碱性环境，对骨髓基质干细胞的定向分化及破骨细胞的功能调控具有重要意义。这在以往的研究中没有被关注。.因此，本课题基于玻璃结构网络设计技术，开发了组成和降解可控的硼硅酸盐系列生物活性玻璃，利用非损伤微测技术（NMT），实时监测硼硅酸盐生物活性玻璃在人工模拟体液（SBF）中浸泡后的表面Ca2+和H+浓度的内流和外流动态变化，明晰了材料表面矿化机理，并通过硼含量的有效调控，调节了生物活性玻璃形成的碱性程度，实现了碱性在体内的有效形成。进一步的研究表明成骨最佳pH环境在pH7.8-8.1之间，可显著上调成骨相关基因Runx2和ALP的表达。骨质疏松大鼠骨髓基质干细胞（BMSC）在pH7.4左右拥有最佳的增殖效率，偏酸或者偏碱都会抑制BMSC的增殖，但微碱性环境可促进BMSC向成骨方向分化。.基于硼/硅双网络设计，可调控生物活性支架在股骨微环境的骨再生速度；生物活性支架在骨量完全丢失和血供严重破坏的胫骨中断节段性骨缺损换微环境下，仍能有效促进新骨再生。团队分别选取了能营造碱性pH微环境（生物活性玻璃），中性pH微环境（PMMA）和酸性pH微环境（PLGA）等材料，将其植入骨质疏松大鼠股骨中段的临界尺寸骨缺损，研究材料不同表面pH微环境对骨质疏松微环境骨缺损修复再生的调控；不同材料植入4个月后，碱性微环境材料（生物活性玻璃）能显著促进缺损部位的体内矿化和新骨形成。.本项目执行期间，共发表SCI论文6篇，中文期刊1篇；同时授权专利1项，申请专利3项。培养3名博士研究生，3名客座学生。已完成了立项所设定的研究内容和研究目标，并在此基础上开展了转化研究，为生物材料碱性微环境设计及骨科临床应用打下了重要的基础。