材料及力学因素对磷酸钙陶瓷骨诱导性的影响

发布时间：2018-08-28 09:53

【摘要】：目前研究认为在磷酸钙生物陶瓷骨诱导性潜能中发挥作用的材料特性包括:化学成分、宏观及微观几何结构和孔隙率。此外,生物体的种属及植入部位也会影响材料的骨诱导活性。尽管对磷酸钙生物陶瓷骨诱导现象的生物机制进行了大量的研究,却仍缺乏对这些机制的系统性理解,这限制了生物陶瓷在临床骨再生治疗中的广泛应用。本研究综合考虑磷酸钙生物陶瓷的宏观孔隙结构和微结构表面特性在异位骨形成中的作用,以及生理环境下应力刺激对骨发生、发育及动态平衡起到的重要作用,从体内应力环境、支架孔隙结构和支架内细胞受到的力学刺激之间的相关性角度入手,基于生物力学调控理论,对生物材料通过自身结构特征调控骨诱导发生的机制进行探讨。为深入研究磷酸钙生物陶瓷与骨诱导发生的相关性机制提供新途径,并对优化设计可控骨诱导性的磷酸钙生物陶瓷提供实验和理论依据。包括以下内容:(1)将具有不同宏观孔隙形状和尺寸的羟基磷灰石颗粒堆积支架(HA spheres accumulating scaffolds, HASAs)和羟基磷灰石颗粒造孔支架(HAporogen-pore scaffolds,HAPPs)植入狗的背肌和腹腔,系统比较宏孔形状和尺寸对支架异位成骨能力的影响。并构建三维支架理论模型,对支架内微流体动力环境进行流动仿真模拟,探讨材料的宏观结构因素通过微流体动力途径转换为骨诱导调控信号的相关性。研究表明宏孔尺寸和形状对HA多孔支架骨诱导性有显著的影响,并且这种影响是两种结构变量共同作用的结果。流体仿真计算结果表明微流体动力环境影响支架内新骨形成和分布。研究发现微流体动力环境是材料的宏孔结构因素转换为骨诱导生物调控信号的重要途径。(2)通过调节溶胶-凝胶体系中HA/Chitin的质量比制备具有不同表面微形貌(粗糙度、比表面积和微孔隙率)的HA球形颗粒。体外细胞实验结果证实材料表面微形貌对BM-MSCs的生物行为有明显影响,多孔粗糙表面在与BM-MSCs复合初期更有利于细胞的增殖,后期则利于细胞骨向分化。细胞在与致密光滑表面复合初期因增殖很快受限,因此提前促进了 BM-MSCs的骨向分化。总体来说多孔粗糙表面对BM-MSCs具有更好的促增殖和分化作用。每种表面都具有良好的细胞相容性。体内动物实验结果表明,本研究所用的具有不同表面微形貌的HA多孔颗粒支架均具有良好的生物相容性,而粗糙表面更利于支架植入体内非骨部位后的异位骨形成。(3)在体外构建生理-微振动应力环境,研究微振动应力刺激(振幅≤50μm、强度1×g、频率范围在1-100Hz的极低幅度、低强度、低频率的力学环境,MV)对羟基磷灰石多孔支架材料上复合的BM-MSCs成骨分化和细胞外基质矿化的影响,探讨微振动对羟基磷灰石生物活性及生物力学性能的影响,以及与羟基磷灰石陶瓷骨诱导性之间的关联性。研究发现微振动应力环境能提升HA多孔支架生物矿化能力,有利于构建成骨环境;微振动应力环境通过三维多孔支架发生力学信号转换诱导BM-MSCs成骨分化;并且微振动应力环境和HA多孔支架协同提高了 BM-MSCs成骨相关基因Cbfal/Runx2、Col-I、ALP、OC的表达和成骨特征性蛋白ALP的表达。(4)将HA颗粒堆积支架(HASAs)植入实验动物腹腔内构建体内组织工程骨移植物,修复自体股骨节段性骨缺损,以探讨利用多孔贯通生物材料支架在体内自然生理环境异位培养组织工程化骨移植物修复大节段承重骨缺损的可能性。同时,也探讨腹腔作为自体生物反应器构建特定形状、大体积的组织工程骨移植物的可能性。研究证明腹腔内低血供、低应力负荷和缺少干细胞源性物质的生理环境具有作为体内生物反应器构建组织工程化骨移植物的可能。并成功将腹腔中构建的具有自体骨组织的骨移植物应用于节段性承重骨缺损修复。
[Abstract]:Current studies have shown that the material properties that play a role in the bone induction potential of calcium phosphate bioceramics include chemical composition, macroscopic and microscopic geometric structures and porosity. However, there is still a lack of systematic understanding of these mechanisms, which limits the wide application of Bioceramics in clinical bone regeneration therapy. Dynamic balance plays an important role in bone induction. Based on the theory of biomechanical regulation, the mechanism of biomaterials regulating bone induction through their own structural characteristics is discussed from the point of view of the correlation between stress environment in vivo, pore structure of scaffolds and mechanical stimulation of cells in scaffolds. This study provides a new way to optimize the design of bone-inducible calcium phosphate bioceramics, including: (1) HA spheres accumulating scaffolds (HASAs) and hydroxyapatite particles with different macroporous shapes and sizes. Haporogen-pore scaffolds (HAPPs) were implanted into the dorsal and abdominal muscles of dogs to compare the effects of macropore shape and size on the ectopic osteogenesis of the scaffolds. A three-dimensional scaffold model was constructed to simulate the microhydrodynamic environment in the scaffolds and explore the macrostructural factors of the scaffolds through the microhydrodynamic pathway. Studies have shown that macropore size and shape have a significant effect on the osteoinductivity of HA porous scaffolds, and this effect is the result of the interaction of two structural variables. Force environment is an important way to convert macroporous structural factors into bone-induced biological signals. (2) HA spherical particles with different surface micromorphologies (roughness, specific surface area and microporosity) were prepared by adjusting the mass ratio of HA/Chitin in sol-gel system. Biological behavior of BM-MSCs was significantly influenced by porous rough surfaces, which were more conducive to cell proliferation at the early stage of BM-MSCs compounding, but more conducive to cell bone differentiation at the later stage. The results of in vivo animal experiments showed that HA porous particle scaffolds with different surface micromorphologies had good biocompatibility, and rough surfaces were more conducive to heterotopic bone formation after implantation in non-bone sites in vivo. To study the effect of micro-vibration stress stimulation (amplitude < 50 micron, intensity 1 xg, frequency range 1-100Hz, mechanical environment of low amplitude, low strength, low frequency, MV) on the osteogenic differentiation and extracellular matrix mineralization of BM-MSCs on porous scaffolds, and to explore the effect of micro-vibration on the formation of hydroxyapatite. It was found that the micro-vibration stress environment could enhance the biomineralization ability of HA porous scaffolds and facilitate the construction of osteogenic environment, and the micro-vibration stress environment could induce BM-MSCs osteogenic differentiation through mechanical signal transformation of three-dimensional porous scaffolds. The expression of BM-MSCs osteogenesis-related genes Cbfal/Runx2, Col-I, ALP, OC and the expression of osteogenic characteristic protein ALP were enhanced by microvibration stress and HA porous scaffolds. (4) HA granular accumulation scaffold (HASAs) was implanted into the abdominal cavity of experimental animals to construct in vivo tissue-engineered bone grafts to repair segmental bone defects of the femur. The possibility of repairing large segmental load-bearing bone defects with tissue-engineered bone grafts in heterotopic culture in vivo using porous perforated biomaterial scaffolds was also discussed. The possibility of constructing large-scale tissue-engineered bone grafts in the abdominal cavity as an autologous bioreactor was also discussed. It is possible to construct tissue-engineered bone grafts in vivo as bioreactor under mechanical loading and lack of stem cell-derived materials. Bone grafts with autogenous bone tissue from abdominal cavity were successfully used to repair segmental load-bearing bone defects.
【学位授予单位】：西南交通大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：R318.08

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