淫羊藿苷-海藻酸钙/锶掺杂磷酸钙复合支架的构建和对骨质疏松症骨再生的作用研究

Osteoporosis-induced bone defects are common skeletal diseases. Most of the existing biomaterials for the treatment of osteoporotic bone defect have insufficient bioactivity to induce the differentiation of endogenous mesenchymal stem cells (MSCs) into osteoblast. Therefore, more effective implant materials need to be developed to promote bone regeneration in osteoporosis. It has been demonstrated that strontium-doped calcium phosphate (Sr-BCP) can reduce bone resorption and promote osteoporotic bone regeneration by stimulating OPG expression and inhibiting RANKL expression. Moreover, the natural product-icariin (Ica) can also inhibit the formation of osteoclasts and reduce bone resorption by upregulating expression of osteogenic related genes in osteoporotic MSCs and down-regulating the expression of inflammatory factors such as tumor necrosis factor-alpha (TNF-α), interleukin-1 (IL-1) and so on. Therefore, based on the hypothesis that the combination of Ica and Sr-BCP may have synergistic effects on bone regeneration in osteoporosis, in this study we propose to covalently load Ica into Sr-BCP-based composite scaffolds, and to investigate the roles of the released Ica and Sr-BCP in promoting osteogenic differentiation of MSCs in osteoporosis and inhibiting osteoclast formation. Meanwhile, we will investigate the synergistic effects of Ica and Sr-BCP on repairing bone defects in osteoporosis, and explore the mechanism of the synergy between Ica and Sr-BCP. This study will not only help to develop a novel biomaterial for osteoporosis-induced bone defects, but will also broaden the applications of Ica.

骨质疏松症骨缺损是常见的骨骼疾病。现有的许多治疗骨质疏松骨缺损的材料，缺乏足够的生物活性诱导内源性骨髓间充质干细胞（MSCs）成骨分化。因此，需要发展更有效的植入材料以促进骨质疏松症骨再生。锶掺杂磷酸钙（Sr-BCP）通过刺激OPG表达、抑制RANKL表达来降低骨吸收、促进骨质疏松症骨再生；天然产物淫羊藿苷（Ica）可上调MSCs成骨相关基因表达，下调炎症因子TNF-α、IL-1等的表达，抑制破骨细胞形成，降低骨吸收水平。于是，基于Ica与Sr-BCP结合可能对骨质疏松症骨再生产生协同作用的假设，本申请拟将Ica共价载入Sr-BCP基复合支架中，考察支架中释放的Ica和Sr-BCP在促进骨质疏松症MSCs成骨分化、抑制破骨细胞形成，以及对骨质疏松症骨缺损再生修复的协同作用，探讨Ica和Sr-BCP协同作用的机制。该研究不仅有望发展一种新型骨质疏松症骨缺损修复材料，也将拓宽Ica的应用范围。

骨质疏松性骨缺损是常见的骨骼疾病。现有的许多治疗骨质疏松骨缺损的材料，缺乏足够的生物活性诱导内源性骨髓间充质干细胞（MSCs）成骨分化。因此，需要发展更有效的植入材料以促进骨质疏松性骨缺损的再生修复。锶掺杂双相磷酸钙（Sr-BCP）通过刺激OPG表达、抑制RANKL表达来降低骨吸收、促进骨质疏松性的骨再生；天然产物淫羊藿苷（Ica）可上调MSCs成骨相关基因表达，下调炎症因子TNF-α、IL-1β等的表达，抑制破骨细胞形成，降低骨吸收水平。于是，基于Ica与Sr-BCP结合可能对骨质疏松性骨再生产生协同作用的假设，本研究首先采用双氧水发泡法、海藻酸钠凝胶成型技术并结合微波烧结技术制备出多孔纳米双相磷酸钙（BCP）和锶掺杂双相磷酸钙（Sr-BCP）陶瓷支架。为了获得药物释放更长久的复合支架，通过两步反应制备出巯基化淫羊藿苷（Ica-SH），然后采用双氧水促进Ica-SH发生交联反应从而将药物涂层到陶瓷支架中，获得具有长期稳定释放药物和锶离子、生物相容性良好的复合支架材料（Sr-BCP/Ica-SH）。支架中同时释放的锶离子和药物分子，可以协同促进去卵巢骨质疏松模型大鼠骨髓间充质干细胞（OVX-rBMSCs）的成骨分化，抑制破骨细胞形成，促进骨质疏松性骨缺损的修复。本研究显示，淫羊藿苷和锶离子通过激活Wnt/β-catenin通路和BMP-2/Smad通路，协同促进OVX-rBMSCs的成骨分化，并通过协同抑制NF-κB和MAPK通路，抑制破骨细胞的成熟和活化。因此，通过本研究，不仅阐明了锶离子和淫羊藿苷同时存在下增强成骨作用、抑制破骨形成的潜在机制，还有望发展一种新型骨质疏松性骨缺损修复材料，进一步拓宽Ica的应用范围。