脉冲电磁场、振动波协同低弹多孔钛合金修复骨缺损的作用研究

Repair of bone defects is one of the most common and toughest issues in orthopedic surgery, and especially thorny for the segmental bone defects repair in long bone. Titanium alloy has become an ideal bone substitutes to repair bone defects, based on its excellent biocompatibility and corrosion-resistant capacity. Due to the mismatching of elastic modulus between the traditional titanium alloy and bone, our group has designed a novel porous titanium alloy with low elastic modulus, which exhibited significant similarity in elastic modulus with trabecular bone as well as favorable biocompatibility. However, the poor osseointegration of this porous titanium alloy for patients with bone defects was a non-negligible issue, especially for the osteoporotic patients. The skeletal tissues are surrounded by complex mechanical and electromagnetic microenvironment. Substantial studies have shown that both pulsed electromagnetic fields (PEMF) and whole-body vibration (WBV) were able to promote bone healing, whereas PEMF and WBV displayed distinct osteogenetic mechanisms. Thus, in this proposal, we hypothesize that synergetic application of our new porous titanium alloy with PEMF and WBV may generate more significant efficiency in bone defects repair by establishing the 'mechanical-electromagnetic' microenvironment surrounding the porous titanium alloy. We will systematically evaluate the effects of synergetic application of porous titanium alloy with PEMF and WBV on the functions of bone cells in vitro and bone defect repair in vivo, as well as achieving the optimum stimulation parameters of PEMF and WBV. Moreover, we will further explore the mechanism of synergetic application of porous titanium alloy with PEMF and WBV on bone repair via systematic investigation of intracellular calcium signaling in bone cells. Together, our present study aims to provide a new therapeutic strategy for bone defects in clinics, reduce the cost of the treatment of bone defects, and improve the living quality of patients with bone defects.

骨缺损是骨科临床常见病和难治病，尤以长骨大段骨缺损修复最为困难。钛合金凭借优良生物相容性和抗腐蚀性成为理想的骨替代修复材料。由于传统钛合金与骨弹性模量不匹配，课题组研制了新型低弹多孔钛合金，该材料能在骨小梁水平实现弹性模量匹配，具有较好的生物相容性。但它在微观水平仍难与骨组织实现充分整合，而对骨质疏松患者骨整合则更为困难。骨处于复杂的应力和电磁微环境中，诸多研究证实脉冲电磁场和振动波具有促骨生成效果，且二者作用机制不同。因此本研究提出了脉冲电磁场、振动波协同低弹多孔钛合金修复骨缺损的新理念，通过施加脉冲电磁场和振动波为多孔钛合金的修复区域构建应力-电磁微环境，通过体外和体内实验系统评估电磁场、振动协同多孔钛合金对骨骼细胞生长和骨缺损修复的作用效果，筛选最佳电磁场、振动波参数，并以细胞钙信号为切入点探索作用的相关机制。本研究旨在为临床骨缺损修复提供新思路，降低骨缺损治疗成本，改善病患生活质量

本项目主要工作包括：（1）构建了新型Ti2448低弹钛合金，其致密植入体弹性模量也只有33GPa，采用电子束熔融技术将该钛合金制备成多孔结构，从而保证了植入体在结构和力学属性上与骨组织匹配。随后我们分别构建了能够用于体内和体外实验的程控式脉冲电磁场（PEMF）和周期振动载荷（WBV）发生系统。（2）于兔股骨外侧髁构建骨缺损模型，缺损处植入Ti2448多孔钛合金（pTi），发现了PEMF促进pTi外周和空隙内部骨长入，提高pTi中骨矿化沉积率，并显著提高成骨分化能力。（3）构建胰岛素依赖糖尿病骨质疏松骨缺损模型，发现了PEMF同样显著提升骨质疏松骨缺损的骨整合能力，改善pTi外周骨力学属性，并显著提高pTi中成骨细胞（OB）功能，但对破骨细胞（OC）和骨细胞（OCY）影响不明显。（4）将兔原代OB接种入pTi中，发现PEMF显著促进体外OB在pTi中的粘附、增殖和成骨分化潜能，并激活了经典Wnt通路。我们也发现，PEMF能够诱发更多的OB产生更显著的钙瞬变，进一步揭示PEMF对于pTi骨整合的作用效果与OB功能的促进相关。（5）我们同样发现了WBV能够促进正常和糖尿病骨质疏松骨缺损的骨整合能力，改善pTi外周骨的力学属性，在提高OB分化能力的基础上，还能够促进OCY功能的改善并抑制OC的骨吸收功能。（6）体外实验进一步揭示，WBV不仅能够促进OB粘附、增殖与成骨分化，还能够促进OCY活性功能，并抑制OC活性与噬骨能力。我们也发现，周期机械载荷能够诱发OCY产生独特的多尖峰钙振荡，而OCY能够响应机械力学信号调控OB和OC的功能活性。综上，本研究揭示了PEMF和WBV均能够有效提高正常和骨质疏松组织pTi骨整合能力，但二者作用在骨组织的靶细胞和诱发的细胞钙振荡机制均存在差异性，本研究不但为临床骨缺损修复提供了新策略，并为更加深入的认识骨骼的电磁和力学信号转导机制提供重要线索。