骨科醫生面臨著老年婦女的骨修復受損或者癒合延遲的挑戰，這使得康復過程變長，甚至引發高死亡率。至今為止，臨床上仍然沒有促進老年骨癒合的滿意治療方法，因此亟需其他治療策略。骨癒合重現了胚胎後的骨骼發育過程。直接由骨外膜成骨（膜內骨化）以及通過軟骨介質成骨（軟骨內骨化）是骨癒合中的兩個重要過程。 雌激素受體β（ERβ基因敲除雌性小鼠的研究表明ERβ信號通路在骨骼發育過程中同時參與了抑制膜內骨化和軟骨內骨化這兩個過程。臨床活檢的資料顯示，在絶經後婦女的骨痂中，ERβ陽性的增生軟骨細胞數量增加。然而，ERβ在正常和老年骨癒合的作用還沒有研究。 / 本研究通過下述部分檢查了ERβ在正常和老年骨癒合的作用，以及其將來的藥物應用：1) 建立一個以膜內骨化為主的骨癒合模型。2) 通過連個骨癒合模型，檢查ERβ在正常骨癒合中的作用。3) 檢查ERβ在老年骨癒合中的作用並檢查ERβ拮抗劑PHTPP 對老年骨癒合的潛在藥物療效。 / 實驗1是建立一個以膜內骨化為主的骨癒合模型。以前建立的小鼠股骨中段骨折模型是軟骨內骨化為主的骨癒合模型。由於技術難度，該模型可重複性不高，而且其金屬內固定器會造成金屬偽影，進而不能應用高解析度微焦點CT跟蹤觀察的技術。為了檢查ERβ在膜內骨化中的作用，並且應用微焦點CT跟蹤觀察技術，我們首先建立了一個小鼠鑽孔缺損模型。該實驗同時也確認了去勢誘導的骨質疏鬆小鼠相比正常小鼠，在鑽孔缺損模型中骨癒合受阻。 / 實驗2檢驗了阻斷ERβ能促進正常骨癒合的假設。本實驗應用ERβ基因敲除小鼠，在兩個模型中檢驗了實驗假設。第一個是傳統的小鼠股骨中段骨折模型，第二個是由實驗1建立的鑽孔缺損模型。兩個模型都證實ERβ基因敲除小鼠骨癒合和野生型小鼠相比，早期的血管新生和中期的礦化有所增強，末期的骨癒合沒有明顯差異。 / 實驗3 進一步研究ERβ在老年骨癒合中的作用。實驗應用老年小鼠股骨中段骨折模型，比較ERβ基因敲除小鼠和野生型小鼠之間的癒合過程。結果顯示ERβ基因敲除小鼠骨癒合和野生型小鼠相比，早期的血管新生，中期的礦化以及末期的力學性能都有所增強。該結果預示阻斷ERβ能作為另一種治療老年骨折癒合的治療策略。同時，我們也檢測了ERβ的拮抗劑PHTPP（4 - [2 - 苯基- 5,7 -二（三氟甲基）吡唑並[1,5 - A]嘧啶3 - 基]苯酚, 在老年骨癒合中的治療效果。 通過比較用藥組小鼠與安慰劑組小鼠的骨癒合品質，顯示PHTPP治療小鼠血管新生，骨痂礦化和最終的力學性質均優於對照安慰劑組小鼠。 / 綜上所述，本研究描述了ERβ在正常和老年骨癒合中的作用。骨癒合的關鍵過程包括血管新生，膜內骨化以及軟骨內骨化在阻斷ERβ後都得到增強，從而加快正常骨和老年骨的骨痂形成，礦化並增強力學性質。ERβ的拮抗劑PHTPP在老年小鼠骨折模型中能促進骨癒合。本研究提出了一個新的骨癒合治療策略，並為將來的臨床實驗提供了堅實的基礎。 / Orthopaedic surgeons are challenged by impaired or delayed bone healing in elderly women, which requires prolongation of rehabilitation process or even induces high mortality. Up to date, there are no satisfactory therapeutic modalities for promoting aged bone healing clinically, and alternative therapeutic stratagem is therefore desirable. Bone healing recapitulates postnatal bone development. Direct periosteam-dependent bone formation (intramembranous ossification) and the formation of bone through a cartilage intermediate (endochondral ossification) are the two important processes during bone healing. Evidences from Estrogen Receptor β (ERβ), gene knockout female mouse studies have demonstrated that ERβ signaling participates in inhibiting both intramembranous and endochondral ossification during bone development. Clinical biopsy data demonstrated that the number of ERβ positive proliferative chondrocytes within fracture callus was increased in postmenopausal women. However, the role of ERβ in normal and aged bone healing is not examined yet. / This study examined role of ERβ in normal and aged bone healing and the future pharmaceutical application though the following part: 1) Establish an intramembranous ossification-dominant bone healing model. 2) Examine the role of ERβ in normal bone healing though two models. 3) Examine the role of ERβ in aged bone healing and investigate the potential therapeutical efficacy of an ERβ antagonist PHTPP in aged bone healing. / Study I was to establish an intramembranous ossification dominant bone healing mouse model. Previous available mouse femoral shaft fracture model was a endochondral ossification dominant bone healing model. This model was technically difficult to generate high reproducibility and the inside metal stabilization devices prevented the application of high-resolution in vivo micro-CT monitoring due to the metal artifact. In order to examine the role of ERβ in intramembranous ossification and apply the micro-CT monitoring technique, a drill-hole defect mouse model was developed. The study also confirmed bone healing was impaired in mice with ovariectomy -induced osteoporosis in drill-hole defect model. / Study II was to test the hypothesis that blockade of ERβ could promote normal bone healing. ERβ knockout mice were employed in this study and the hypothesis was examined in two models, the first is the traditional mouse femoral shaft fracture model, and the second is the drill-hole defect model that was developed in study I. Both models demonstrated that the bone healing in ERβ knockout mice was enhanced in the early stage of neovascularization and the middle stage of ossification but not by the end of healing compare to the wild type mice. / Study III was designed to further investigate the role of ERβ in aged bone healing. Femoral shaft fracture model was created in aged mice. The healing process was compared between the ERβ knockout mice and wild type mice. The results demonstrated that ERβ knockout mice was enhanced in the early stage of neovascularization, the middle stage of ossification and end stage of mechanical strength. The findings implied blockade of ERβ can be considered as another therapeutic strategy for aged fracture healing. PHTPP (4-[2-Phenyl-5,7-bis(trifluoromethyl)pyrazolo[1,5-a]pyrimidin-3-yl] phenol), an ERβ antagonist, was employed in aged mice femoral shaft fracture model. The bone healing quality of treated mice was compared with that of the vehicle control mice. It showed PHTPP treated mice had enhanced neovascularization, callus ossification and finally better mechanical properties than vehicle mice. / The present study depicted the role of ERβ in normal and aged bone healing. Key processes including neovascularization, intramembranous and endochondral ossification were all enhanced by blockade of ERβ, which led to fast callus formation, mineralization in normal bone and better mechanical properties in aged bone. ERβ antagonist PHTPP could promote aged bone healing in mouse osteotomy model. This study raised an alternative therapeutic stratagem for bone healing and provided solid basis for future clinical trials. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / He, Yixin. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 147-167). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / ABSTRACT --- p.i / 中文摘要 --- p.iv / PUBLICATIONS AND AWARDS --- p.vi / ACKNOWLEDGEMENTS --- p.xi / TABLE OF CONTENTS --- p.xii / LIST OF ABBREVIATIONS --- p.xvi / LIST OF FIGURES --- p.xviii / LIST OF TABLES --- p.xx / Chapter CHAPTER 1 --- INTRODUCTION AND LITERATURE REVIEW --- p.1 / Chapter 1.1 --- Fracture and Bone Healing --- p.2 / Chapter 1.1.1 --- Epidemiology and Impacts of Fractures --- p.2 / Chapter 1.1.2 --- Current Management and Limitations --- p.3 / Chapter 1.1.3 --- Bone Structures --- p.5 / Chapter 1.1.4 --- Bone Healing --- p.7 / Chapter 1.1.5 --- Aged Bone Healing --- p.12 / Chapter 1.1.6 --- Enhancements of Bone Healing --- p.17 / Chapter 1.2 --- Estrogen and Estrogen Receptors --- p.19 / Chapter 1.2.1 --- Estrogen Receptors α and β --- p.19 / Chapter 1.2.2 --- Molecular Actions of Estrogens --- p.20 / Chapter 1.2.3 --- Estrogen receptors in bone homeostasis --- p.24 / Chapter 1.3 --- Hypothesis --- p.28 / Chapter 1.4 --- Study Plan and Objectives --- p.32 / Chapter 1.4.1 --- Bone Healing Models --- p.32 / Chapter 1.4.2 --- Study Outline --- p.32 / Chapter 1.5 --- Figures and Tables --- p.34 / Chapter CHAPTER 2 --- ESTABLISHMENT OF DRILL-HOLE DEFECT HEALING MODEL IN MICE --- p.39 / Chapter 2.1 --- Introduction --- p.40 / Chapter 2.1.1 --- Limitations in currently available mouse models of osteoporotic bone healing --- p.40 / Chapter 2.1.2 --- Creation of a drill-hole defect at the mid-diaphysis of the femur for in vivo monitoring of bone healing in mice --- p.40 / Chapter 2.2 --- Materials and Methods --- p.43 / Chapter 2.2.1 --- Experimental animals --- p.43 / Chapter 2.2.2 --- Surgical protocol and experimental design --- p.43 / Chapter 2.2.3 --- Micro-CT analysis of intact femur --- p.44 / Chapter 2.2.4 --- In vivo micro-CT analysis of new bone formation in the drill-hole site --- p.45 / Chapter 2.2.5 --- Micro-CT-based angiography --- p.45 / Chapter 2.2.6 --- Histological examination --- p.46 / Chapter 2.2.7 --- Immunohistochemistry --- p.46 / Chapter 2.2.8 --- Quantitative real-time PCR --- p.47 / Chapter 2.2.9 --- Analysis of bone formation and resorption markers --- p.47 / Chapter 2.2.10 --- Mechanical testing --- p.48 / Chapter 2.2.11 --- Statistical analysis --- p.48 / Chapter 2.3 --- Results --- p.51 / Chapter 2.3.1 --- Confirmation of osteoporotic bone prior to generation of a drill-hole defect --- p.51 / Chapter 2.3.2 --- General observation of mice following drill-hole surgery --- p.51 / Chapter 2.3.3 --- In vivo micro-CT analysis of new bone in the drill-hole site of mouse femurs --- p.51 / Chapter 2.3.4 --- In vivo micro-CT analysis of new bone in drill-hole sites is highly reproducible --- p.52 / Chapter 2.3.5 --- Micro-CT angiography --- p.52 / Chapter 2.3.6 --- Histological observation of bone healing --- p.53 / Chapter 2.3.7 --- Immunohistochemical analysis of ER expressions during bone healing --- p.54 / Chapter 2.3.8 --- Quantitative real-time PCR analysis of gene expression during bone healing --- p.54 / Chapter 2.3.9 --- Analysis of bone formation and resorption markers during bone healing --- p.54 / Chapter 2.3.10 --- Mechanical testing of femurs from Sham and OVX mice --- p.55 / Chapter 2.4 --- Discussion --- p.56 / Chapter 2.4.1 --- Bone healing with dominant intramembranous ossification --- p.56 / Chapter 2.4.2 --- Impaired osteoporotic bone healing --- p.57 / Chapter 2.4.3 --- Reproducibility of the in vivo micro-CT method for analysis of bone healing --- p.58 / Chapter 2.4.4 --- Dysregulated expression of estrogen receptors and bone healing in OVX mice --- p.59 / Chapter 2.4.5 --- Study limitations --- p.60 / Chapter 2.4.6 --- Conclusions --- p.60 / Chapter 2.5 --- Figures and Tables --- p.61 / Chapter CHAPTER 3 --- ROLE OF ERβ IN NORMAL BONE HEALING --- p.72 / Chapter 3.1 --- Introduction --- p.73 / Chapter 3.2 --- Materials and Methods --- p.75 / Chapter 3.2.1 --- Part I Study --- p.75 / Chapter 3.2.1.1 --- Experimental animals --- p.75 / Chapter 3.2.1.2 --- Fracture model and experimental design --- p.75 / Chapter 3.2.1.3 --- Radiographic Analysis --- p.76 / Chapter 3.2.1.4 --- Micro-CT-based angiography --- p.76 / Chapter 3.2.1.5 --- Micro-CT analysis of callus --- p.77 / Chapter 3.2.1.6 --- Histological examination --- p.78 / Chapter 3.2.1.7 --- Dynamic Bone histomorphometric analysis --- p.78 / Chapter 3.2.1.8 --- Mechanical testing --- p.79 / Chapter 3.2.1.9 --- Quantitative real-time PCR --- p.80 / Chapter 3.2.1.10 --- Analysis of bone formation and resorption markers --- p.80 / Chapter 3.2.1.11 --- Statistical analysis --- p.81 / Chapter 3.2.2 --- Part II Study --- p.81 / Chapter 3.2.2.1 --- Experimental animals and design --- p.81 / Chapter 3.2.2.2 --- Evaluation protocols --- p.82 / Chapter 3.2.2.3 --- Statistical analysis --- p.82 / Chapter 3.3 --- Results --- p.83 / Chapter 3.3.1 --- Part I Study --- p.83 / Chapter 3.3.1.1 --- Radiographic Analysis --- p.83 / Chapter 3.3.1.2 --- Micro-CT angiography --- p.83 / Chapter 3.3.1.3 --- Micro-CT analysis of callus --- p.83 / Chapter 3.3.1.4 --- Histological and dynamic histomorphometric analysis --- p.84 / Chapter 3.3.1.5 --- Mechanical testing of the callus --- p.85 / Chapter 3.3.1.6 --- Quantitative real-time PCR analysis of gene expression --- p.85 / Chapter 3.3.1.7 --- Analysis of bone formation and resorption markers during bone healing --- p.85 / Chapter 3.3.2 --- Part II Study --- p.86 / Chapter 3.3.2.1 --- In vivo micro-CT analysis of new bone in the drill-hole site of mouse femurs --- p.86 / Chapter 3.3.2.2 --- Micro-CT angiography --- p.87 / Chapter 3.3.2.3 --- Histological observation of bone healing --- p.87 / Chapter 3.3.2.4 --- Quantitative real-time PCR analysis of gene expression --- p.88 / Chapter 3.3.2.5 --- Analysis of bone formation and resorption markers during bone healing --- p.88 / Chapter 3.3.2.6 --- Mechanical testing of femurs from WT and KO mice --- p.88 / Chapter 3.4 --- Discussion --- p.90 / Chapter 3.4.1 --- Angiogenesis --- p.90 / Chapter 3.4.2 --- Fracture Healing --- p.91 / Chapter 3.4.3 --- Estrogen receptor β and endochondral and intramembranous ossification --- p.93 / Chapter 3.4.4 --- Estrogen receptor β in aged bone --- p.94 / Chapter 3.4.5 --- Conclusions --- p.94 / Chapter 3.5 --- Figures and Tables --- p.95 / Chapter CHAPTER 4 --- ROLE OF ERβ AND ITS ANTAGONIST PHTPP IN AGED BONE HEALING --- p.113 / Chapter 4.1 --- Introduction --- p.114 / Chapter 4.2 --- Materials and Methods --- p.116 / Chapter 4.2.1 --- Experimental animals --- p.116 / Chapter 4.2.2 --- Fracture model and experimental design --- p.116 / Chapter 4.2.3 --- Radiographic Analysis --- p.117 / Chapter 4.2.4 --- Micro-CT-based angiography --- p.118 / Chapter 4.2.5 --- Micro-CT analysis of callus --- p.118 / Chapter 4.2.6 --- Histological examination --- p.119 / Chapter 4.2.7 --- Dynamic Bone histomorphometric analysis --- p.120 / Chapter 4.2.8 --- Mechanical testing --- p.120 / Chapter 4.2.9 --- Quantitative real-time PCR --- p.121 / Chapter 4.2.10 --- Analysis of bone formation and resorption markers --- p.122 / Chapter 4.2.11 --- Statistical analysis --- p.122 / Chapter 4.3 --- Results --- p.123 / Chapter 4.3.1 --- Radiographic Analysis --- p.123 / Chapter 4.3.2 --- Micro-CT angiography --- p.123 / Chapter 4.3.3 --- Micro-CT analysis of callus --- p.123 / Chapter 4.3.4 --- Histological and dynamic histomorphometric analysis --- p.124 / Chapter 4.3.5 --- Mechanical testing of the callus --- p.125 / Chapter 4.3.6 --- Quantitative real-time PCR analysis of gene expression during fracture healing --- p.125 / Chapter 4.3.7 --- Analysis of bone formation and resorption markers during bone healing --- p.126 / Chapter 4.4 --- Discussion --- p.127 / Chapter 4.4.1 --- Angiogenesis --- p.127 / Chapter 4.4.2 --- Fracture Healing --- p.128 / Chapter 4.4.3 --- Estrogen receptor β and endochondral ossification --- p.129 / Chapter 4.4.4 --- ERβ antagonist PHTPP --- p.130 / Chapter 4.4.5 --- Conclusions --- p.130 / Chapter 4.5 --- Figures and Tables --- p.131 / Chapter CHAPTER 5 --- STUDY LINITATIONS, FURTHER RESEARCH AND CONCLUDSIONS --- p.142 / Chapter 5.1 --- Limitations --- p.143 / Chapter 5.1.1 --- Bone healing model --- p.143 / Chapter 5.1.2 --- Estrogen receptors and transgenic mouse --- p.143 / Chapter 5.1.3 --- ERβ antagonist PHTPP --- p.144 / Chapter 5.2 --- Further Research --- p.144 / Chapter 5.2.1 --- ERβ signaling --- p.144 / Chapter 5.2.2 --- Preclinical Trial --- p.145 / Chapter 5.3 --- Conclusions --- p.146 / BIBLIOGRAPHY --- p.147

研究背景：常规骨科临床在治疗大段骨缺损时需要移植骨和（或）支架材料，尤其复合有治疗性生物活性成分的复合材料尤为理想。本研究的策略在于发展开发一种具有生物活性和生物降解特性的的合并有植物小分子icaritin（外源性生长因子）或者骨形态发生蛋白2（BMP-2, 内源性生长因子）的复合骨支架用于骨再生。基于聚乳酸乙交酯共聚物和磷酸三钙，我们利用先进的快速成型技术编制了新型的符合有BMP-2 或者icaritin 的支架材料， 命名为PLGA/TCP （ 对照材料组） ，PLGA/TCP/BMP-2（BMP-2 编织复合治疗材料组）， PLGA/TCP/icaritin （低，中，高剂量icaritin 编织复合治疗材料组）。 / 研究目标：本研究的总体目标是通过系统的体外实验和兔骨缺损的体内实验，建立和评估一种优化的复合递送系统，用于骨再生的应用。体内效果的研究体现在终点关于合并有外源性生长因子icaritin 和内源性生长因子BMP-2 的复合材料之间的比较研究。 / 材料和方法：低温快速成型机器用于复合材料的编制。PLGA 和TCP 作为基本载体材料，icaritin 和BMP-2 作为具有生物活性的外源性和内源性生长因子，分别进行编织复合。最终编织复合的支架材料命名为P/T 对照组，P/T/BMP-2 和低，中，高剂量P/T/icaritin 治疗组。另外，我们通过液体完全浸泡并在真空橱内干燥24 小时的方法制备了BMP-2 和icaritin 浸泡复合支架材料，分别是P/T+BMP-2(阳性对照组)和中剂量P/T+icaritin(比较组)。体外成骨潜能是通过兔骨髓干细胞和支架材料共培养的方法检测细胞接种，增殖效率，碱性磷酸酶活性，钙沉积以及成骨基因定量mRNA 表达检测。兔尺骨双侧阶段性缺损并植入复合支架材料的模型用于探讨支架材料体内成骨和成血管功效，影像学和活体检测CT 技术用于评估骨再生；借助CT的血管造影术和组织学检测新生血管；动态核磁共振技术用于检测骨缺损局部血液灌注功能，以及宿主组织和支架材料之间的相互作用。 / 研究结果： 对编织的支架材料的体外特性和成骨潜能进行鉴定和评估。显微CT 定量结果显示此支架材料具有互联大孔隙，平均孔隙率75±3.27%，平均孔径458±25.6μm。和对照组，icaritin 浸泡复合组，BMP-2 编织复合组比较，在icaritin 编织复合支架材料（n=6, p<0.05）特别是中剂量组（n=6, p<0.01）中，与材料共培养的兔骨髓干细胞（BMSCs）表现了较高的细胞接种效率，碱性磷酸酶活性和上调的胶原酶I，骨桥蛋白mRNA 表达，以及较多的钙结节沉积。同时，BMP-2 浸泡复合组表现了最佳的效果（n=6, p<0.01）。兔尺骨缺损模型体内试验结果显示，术后2，4，8周影像学和显微CT 显示，和对照组，icaritin 浸泡复合组，BMP-2 编织复合组比较，icaritin 编织复合支架材料（n=6, p<0.05）特别是中剂量组材料（n=6, p<0.01）植入的骨缺损区域有更多新生成骨。BMP-2 浸泡复合组表现了最多的新骨形成（n=6,p<0.01）。组织学结果同样也验证了在icaritin 编织复合支架材料（n=6, p<0.05）特别是中剂量组（n=6, p<0.01）中，存在较多的骨样组织和典型的板层骨。BMP-2 浸泡复合组也具有最多的新骨组织生成（n=6, p<0.01）。此外， 在icaritin 编织复合支架材料（n=6, p<0.05）尤其中剂量组（n=6, p<0.01）中，借助显微CT 的血管造影术检测发现，骨缺损区域出现较大的新生血管体积，动态核磁共振检查发现较好的局部血液灌注功能。在三种icaritin 剂量浓度的编织复合材料组之间比较，我们发现中浓度icaritin 复合比例的编织复合材料组显示了最佳的成骨潜能。 / 研究结论： 编织复合有外源性植物分子icaritin 的PLGA/TCP 支架材料在体内体外试验中均表现了预期的成骨分化潜能和骨再生能力，尤其是中剂量icaritin 编织复合材料。传统的应用前做体外复合的BMP-2 浸泡复合支架材料和更具吸引力和方便应用的植物分子icaritin 编织复合支架材料，都可以较好的增强骨修复，这很可能为新型生物复合材料潜在的临床有效性验证提供很好的基础。 / Background: Treatment of large bone defect in routine orthopaedic clinics requires bonegrafting and/or scaffold materials, especially desirable with composite material combined with therapeutic and bioactive agents for achieving better treatment outcome. The strategy of this study was to develop such a bioactive biodegradable composite bone scaffold incorporating a phytomolecule icaritin as an exogenous growth factor or bone morphogenetic protein-2 (BMP-2) as a known endogenous growth factor for bone regeneration. Based on polylactide-co-glycolide (PLGA) and Tricalcium Phosphate (TCP), we fabricated innovative BMP-2 or icaritin incorporated scaffold materials, namely PLGA/TCP (Control group), PLGA/TCP/BMP-2 and PLGA/TCP/low-, middle-, and high-icaritin with three different dosages of icaritin (Treatment groups) by an advanced prototyping technology. / Aims: The overall aim of the study was to establish and evaluate a local delivery system with slow release of bioactive agents for acceleration of bone regeneration in a bone defect model in rabbits. In vivo efficacy study served as end-point of this comparative study between composite scaffold incorporating exogenous growth factor icaritin and endogenous growth factor BMP-2. / Materials & Methods: Composite scaffolds were fabricated at -28ºC by a lowtemperature rapid-prototyping machine. PLGA and TCP were used as basic carrier materials, and icaritin or BMP-2 was incorporated as exogenous or endogenous bioactive growth factors, respectively. The incorporated scaffolds were named by PLGA/TCP (P/T, Control group), PLGA/TCP/BMP-2 and PLGA/TCP/low-, middle-, and high-icaritin (Treatment groups). In addition, we prepared BMP-2 and icaritin loading scaffolds, namely PLGA/TCP+BMP-2 as positive control group and PLGA/TCP+middle-icaritin as comparative group by entire immersion in the solution and dry in vacuum cabinet for 24 hours. In vitro osteogenic potentials of the designed bioactive composite scaffolds were tested in scaffold-co-cultured rabbit bone marrow stem cells (BMSCs) for measurement of cell seeding and proliferation efficiency, alkaline phosphatase (ALP) activity, calcium deposition, and quantitative mRNA expression of relative osteogenic genes. In vivo efficacy investigation was designed to evaluate osteogenesis and angiogenesis in a bilateral ulna bone segmental defect model implanted with composite scaffold in rabbits, with radiography and in vivo micro-CT for studying new bone regeneration and micro-CT-based angiography and histology for neovascularization, dynamic MRI for local blood perfusion function, as well as host tissue and scaffold material interactions. / Results: The in vitro characterization and osteogenic potential of the fabricated scaffolds were performed and confirmed, respectively. Micro-CT quantitation showed that the scaffolds had interconnected macropores with an average porosity of 75±3.27 % and pore size or diameter of 458±25.6 μm. Compared to P/T, P/T+icaritin and P/T/BMP-2 scaffolds, P/T/icaritin scaffolds (n=6, p<0.05), especially P/T/middle-icaritin (n=6, p<0.01) presented higher cell seeding efficiency, ALP activity and calcium nodules and up-regulated mRNA expressions of Collagen type I and Osteopontin of co-cultured BMSCs. P/T+BMP-2 showed the best osteogenic effects among all groups (n=6, p<0.01). In vivo measurement of x-ray and micro-CT in rabbit ulna bone defect model at week 2, 4 and 8 post-surgery showed more newly formed bone in the defects treated with P/T/icaritin scaffolds (n=6, p<0.05), especially P/T/middle-icaritin scaffold (n=6, p<0.01) compared with that of P/T, P/T+icaritin and P/T/BMP-2 groups. P/T+BMP-2 also showed the best bone formation among all groups (n=6, p<0.01). Histological results also demonstrated that there were more osteoid tissues and typical lamellar bone in surface and internal of the implants, as well as along the adjacent host bone in P/T/icaritin groups (n=5, p<0.05), especially P/T/middle-icaritin group (n=6, p<0.01). P/T+BMP-2 group showed the most newly formed bone (n=6, p<0.01). In addition, newly formed vessels in the defects were identified with micro-CT-based angiography and functionally supported by dynamic MRI for reflecting blood perfusion. The results showed more ingrowing new vessels in P/T/icaritin groups (n=6, p<0.05), especially P/T/middle-icaritin group (n=6, p<0.01), compared to P/T and P/T/BMP-2 groups. For comparing dose effects among three scaffolds incorporating different concentration of icaritin, we found that middle dose PLGA/TCP/icaritin composite scaffold showed the best osteogenic potential. / Conclusion: PLGA/TCP scaffolds incorporating exogenous phytomolecule icaritin demonstrated the desired osteogenic differentiation potential and bone regeneration capability as investigated in vitro and in vivo, where the middle dose of icaritin incorporating PLGA/TCP composite scaffold showed the best effects. These findings may form a good foundation for potential clinical validation of this innovative bioactive composite scaffold with either conventional endogenous BMP-2 for in vitro loading before application or more attractively and user-friendly incorporated with exogenous phytomolecule icaritin as a ready product for enhancing bone defect repair. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Chen, Shihui. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 173-198). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Acknowledgements --- p.viii / Abstract --- p.x / 中文摘要 --- p.xiii / List of Abbreviations --- p.xvi / List of Tables --- p.xix / List of Figures --- p.xx / Journal Publications --- p.xxv / Journal Supplements --- p.xxv / Conference Abstracts --- p.xxvi / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Bone Defect in Orthopaedics --- p.2 / Chapter 1.2 --- Human Skeletons --- p.2 / Chapter 1.2.1 --- Bone Types and Function --- p.2 / Chapter 1.2.2 --- Bone Development --- p.4 / Chapter 1.2.3 --- Bone Physiology and Structure --- p.6 / Chapter 1.2.4 --- Bone Specific Markers --- p.7 / Chapter 1.2.5 --- Bone Cells --- p.9 / Chapter 1.2.6 --- Bone Marrow Stromal Cells --- p.12 / Chapter 1.3 --- Bone Regeneration and Remodeling --- p.13 / Chapter 1.3.1 --- Bone Defect Healing --- p.13 / Chapter 1.3.2 --- Non-union and Segmental Defect --- p.15 / Chapter 1.3.3 --- Bone Defect Treatment --- p.16 / Chapter 1.4 --- Angiogenesis in Bone Healing --- p.19 / Chapter 1.4.1 --- Blood Vessels Formation Process --- p.20 / Chapter 1.4.2 --- Growth Factor in Angiogenesis --- p.21 / Chapter 1.5 --- Biomaterials in Bone Tissue Engineering --- p.22 / Chapter 1.6 --- Scaffold-Based Therapy --- p.23 / Chapter 1.6.1 --- Bone Grafts --- p.23 / Chapter 1.6.1.1 --- Autografts --- p.23 / Chapter 1.6.1.2 --- Allografts --- p.25 / Chapter 1.6.2 --- Bone Graft Substitutes --- p.25 / Chapter 1.6.2.1 --- Bone Formation in Porous Scaffolds --- p.25 / Chapter 1.6.2.2 --- Degradable Polymers --- p.27 / Chapter 1.6.2.3 --- Non-Degradable Polymers --- p.29 / Chapter 1.6.2.4 --- Ceramics --- p.29 / Chapter 1.6.2.5 --- Bioactive Composite Materials --- p.30 / Chapter 1.7 --- Growth Factor-Based Therapy --- p.31 / Chapter 1.7.1 --- Endogenous Growth Factor--Bone Morphogenetic Proteins --- p.31 / Chapter 1.7.2 --- Exogenous phytomoleculeIcaritin--Icaritin --- p.31 / Chapter 1.7.3 --- Delivery of Growth Factor in Tissue Engineering --- p.34 / Chapter 1.8 --- Fabrication of Porous Composite Scaffolds --- p.37 / Chapter 1.8.1 --- Architectural Parameters of Bone Scaffolds --- p.37 / Chapter 1.8.2 --- Three-Dimensional Scaffold Fabrication --- p.37 / Chapter 1.9 --- Animal Models for Testing Bone Defects Healing --- p.39 / Chapter Chapter 2 --- Research Rationale and Study Objectives / Chapter 2.1 --- Research Rationale --- p.42 / Chapter 2.2 --- Study Objectives --- p.46 / Chapter Chapter 3 --- Bioactive Composite Scaffolds: Preparation, Morphology and Release Assay / Chapter 3.1 --- Introduction --- p.49 / Chapter 3.2 --- Materials and Methods --- p.50 / Chapter 3.2.1 --- Materials --- p.50 / Chapter 3.2.2 --- Fabrication of PLGA/TCP Incorporating BMP-2 or Icaritin --- p.51 / Chapter 3.2.3 --- Morphological Analysis of Composite Scaffolds --- p.53 / Chapter 3.2.3.1 --- Analysis of Porosity and Macropores Diameter Using High-resolution Micro-CT --- p.53 / Chapter 3.2.3.2 --- Analysis of Surface Morphology and Elements Composition Using Scanning Electron Microscopy --- p.54 / Chapter 3.2.4 --- Icaritin Content Assay in PLGA/TCP Scaffolds Incorporating Icaritin --- p.54 / Chapter 3.2.5 --- Preparation of PLGA/TCP Scaffold Coating BMP-2 or Icaritin --- p.55 / Chapter 3.2.6 --- In vitro Release Assay --- p.55 / Chapter 3.2.6.1 --- Icaritin Release from Scaffolds of PLGA/TCP Incorporating Icaritin --- p.55 / Chapter 3.2.6.2 --- BMP-2 Release from Scaffolds of PLGA/TCP Incorporating/Coating BMP-2 --- p.56 / Chapter 3.2.7 --- Mechanical Properties of Composite Scaffolds --- p.56 / Chapter 3.2.8 --- Statistical Analysis --- p.57 / Chapter 3.3 --- Results --- p.57 / Chapter 3.3.1 --- Morphological Analysis of Composite Scaffolds --- p.57 / Chapter 3.3.1.1 --- Porosity and Macroscopic Diameter --- p.57 / Chapter 3.3.1.2 --- Surface Morphology and Elements Composition --- p.58 / Chapter 3.3.2 --- Icaritin Content in Scaffolds of PLGA/TCP Incorporating Icaritin --- p.60 / Chapter 3.3.3 --- Icaritin Release from Scaffolds of PLGA/TCP Incorporating Icaritin --- p.60 / Chapter 3.3.4 --- BMP-2 Release from Scaffolds of PLGA/TCP Incorporating/Coating BMP-2 --- p.61 / Chapter 3.3.5 --- Mechanical Properties of Composite Scaffolds --- p.63 / Chapter 3.4 --- Discussion --- p.64 / Chapter 3.5 --- Summary --- p.71 / Chapter Chapter 4 --- Bioactive Composite Scaffolds: In vitro Degradation and Characterization Studies / Chapter 4.1 --- Introduction --- p.73 / Chapter 4.2 --- Materials and Methods --- p.74 / Chapter 4.2.1 --- Preparation of Composite Scaffolds for in vitro Degradation Assay --- p.74 / Chapter 4.2.2 --- Characterizations --- p.75 / Chapter 4.2.2.1 --- Scaffold Volume Changes --- p.75 / Chapter 4.2.2.2 --- Scaffold Weight Changes --- p.75 / Chapter 4.2.2.3 --- pH Value Changes --- p.75 / Chapter 4.2.2.4 --- Calcium Ion Release from Scaffolds --- p.76 / Chapter 4.2.3 --- Mechanical Properties Changes --- p.76 / Chapter 4.2.4 --- Statistical Analysis --- p.77 / Chapter 4.3 --- Results --- p.77 / Chapter 4.3.1 --- Volume Decrease --- p.78 / Chapter 4.3.2 --- Weight Loss --- p.78 / Chapter 4.3.3 --- pH Value Reduction --- p.79 / Chapter 4.3.4 --- Calcium Ion Release --- p.79 / Chapter 4.3.5 --- Mechanical Properties --- p.80 / Chapter 4.4 --- Discussion --- p.81 / Chapter 4.5 --- Summary --- p.84 / Chapter Chapter 5 --- In vitro Evaluation of Bone Marrow Stem Cells (BMSCs) Growing on Bioactive Composite Scaffolds / Chapter 5.1 --- Introduction --- p.87 / Chapter 5.2 --- Materials and Methods --- p.90 / Chapter 5.2.1 --- Preparation of Composite Scaffolds for in vitro Evaluation --- p.90 / Chapter 5.2.2 --- BMSCs Seeding Rate and Proliferation on Composite Scaffolds --- p.90 / Chapter 5.2.3 --- Alkaline Phosphate (ALP) Activity Assay --- p.92 / Chapter 5.2.4 --- Osteogenic Gene Expression Assay Using Quantitative Real-time PCR --- p.92 / Chapter 5.2.5 --- Calcium Deposition Assay Using Alizarin Red Staining --- p.93 / Chapter 5.2.6 --- Statistical Analysis --- p.94 / Chapter 5.3 --- Results --- p.94 / Chapter 5.3.1 --- Cells Seeding Efficiency and Proliferation --- p.94 / Chapter 5.3.2 --- ALP Activity --- p.97 / Chapter 5.3.3 --- Osteogenic Gene mRNA Expression --- p.97 / Chapter 5.3.4 --- Calcium Deposition --- p.98 / Chapter 5.4 --- Discussion --- p.99 / Chapter 5.5 --- Summary --- p.102 / Chapter Chapter 6 --- In vivo Evaluation of Bone Healing in Bone Defect Model Implanted with Bioactive Composite Scaffolds / Chapter 6.1 --- Introduction --- p.105 / Chapter 6.2 --- Materials and Methods --- p.106 / Chapter 6.2.1 --- Preparation of Composite Scaffolds for Implantation --- p.106 / Chapter 6.2.2 --- Establishment of Ulna Bone Segmental Defect in Rabbits --- p.107 / Chapter 6.2.3 --- Radiographic Evaluation of New Bone Area Fraction --- p.109 / Chapter 6.2.4 --- XtremeCT Evaluation of New Bone Formation and Bone Mineral Density (BMD) --- p.110 / Chapter 6.2.5 --- Histological Evaluation of New Bone Formation --- p.111 / Chapter 6.2.6 --- Evaluation of Rate of New Bone Formation and Mineral Apposition Rate (MAR) --- p.114 / Chapter 6.2.7 --- Evaluation of Neovascularization Using Micro-CT-based Microangiography --- p.116 / Chapter 6.2.8 --- Blood Perfusion Function Using Dynamic Magnetic Resonance Imaging (MRI) --- p.119 / Chapter 6.2.9 --- Statistical Analysis --- p.120 / Chapter 6.3 --- Results --- p.121 / Chapter 6.3.1 --- Radiographic Area Fraction of New Bone Formation --- p.123 / Chapter 6.3.2 --- XtremeCT New Bone Volume Fraction and BMD --- p.128 / Chapter 6.3.3 --- Histological New Bone Fraction --- p.133 / Chapter 6.3.4 --- Rate of New Bone Formation and MAR --- p.136 / Chapter 6.3.5 --- New Vessels Volume Evaluated Using Micro-CT-Based Microangiography --- p.140 / Chapter 6.3.6 --- Dynamic Blood Perfusion Function --- p.144 / Chapter 6.4 --- Discussion --- p.146 / Chapter 6.5 --- Summary --- p.151 / Chapter Chapter 7 --- Summaries, Conclusions, Limitations and Future Studies / Chapter 7.1 --- Introduction --- p.153 / Chapter 7.2 --- Bioactive Composite Scaffolds: Preparation, Morphology and in vitro Release Evaluation --- p.155 / Chapter 7.3 --- Bioactive Composite Scaffolds: in vitro Degradation and Characterization Studies --- p.159 / Chapter 7.4 --- In vitro Evaluation of the Response of Bone Marrow Stem Cells Growing on Bioactive Composite Scaffolds --- p.160 / Chapter 7.5 --- In vivo Evaluation of Bone Healing in Bone Defect Model Implanted with Bioactive Composite Scaffolds --- p.162 / Chapter 7.6 --- Evaluation of Dose-dependent Effects of Icaritin Mechanical Property, Degradation, and Osteogenic Potentials --- p.164 / Chapter 7.7 --- Conclusions --- p.170 / Chapter 7.8 --- Limitations and Future Studies --- p.171 / Chapter 7.9 --- References --- p.173 / Chapter 7.10 --- Appendix --- p.199 / Chapter 7.10.1 --- Animal Licence and Ethics --- p.199 / Chapter 7.10.2 --- Safety Approval --- p.201 / Chapter 7.10.3 --- Journal Supplements --- p.202 / Chapter 7.10.4 --- Conference Abstracts--Posters --- p.205 / Chapter 7.10.5 --- Conformation of Paper Submission --- p.208 / Chapter 7.10.6 --- Published Paper --- p.209

Bone defects caused by trauma, tumor resection or disease present a significant clinical problem. Failures in 'high risk' fractures and large bone defects have been reported to be as high as 30-50%. The drawbacks associated with current bone grafting procedures have stimulated the search for improved techniques for bone repair. Tissue engineering/regenerative medicine approaches promote tissue repair by providing a combination of physical and biological cues through structural scaffolds and bioactive agents. Though they have demonstrated significant promise for bone regeneration, very little has been translated to clinical practice. The goal of this thesis was to investigate the potential of electrospun nanofiber mesh scaffolds for bone regeneration. Nanofiber meshes were utilized in a three-pronged approach. First, we validated their ability to robustly support osteogenic cell functions, including proliferation and matrix mineralization. We also demonstrated their efficacy as a cell delivery vehicle. Second, we investigated the effects of modulating nanofiber bioactivity and orientation on stem cell programming. Our results indicate that functionalization of nanofiber meshes with a collagen-mimetic peptide enhanced the migration, proliferation and osteogenic differentiation of cells. Fiber alignment improved cell migration along the direction of fiber orientation. Finally, a nanofiber mesh based hybrid system for growth factor delivery was developed for bone repair and tested in a challenging animal model. The delivery of bone morphogenetic protein (BMP) via this system resulted in the functional restoration of limb function, and in fact proved more efficacious than the current clinical standard for BMP delivery. The studies performed in this thesis have suggested novel techniques for improving the repair of clinically challenging bone defects. They indicate that the delivery of BMP via the hybrid system may reduce the dose and side effects of BMP, thereby broadening the use of BMP based bone augmentation procedures. Therefore, this nanofiber mesh based system has the potential to become the standard of care for clinically challenging bone defects, including large bone defects, open tibial fractures, and nonunions.

Regeneration of large bone defects presents a critical challenge to orthopaedic clinicians as the current treatment strategies are severely limited. Tissue engineering has therefore emerged as a promising alternative to bone grafting techniques. This approach features the delivery of bioactive agents such as stem cells, genes, or proteins using biomaterial delivery systems which together stimulate endogenous repair mechanisms to regenerate the tissue. Because bone is a highly mechanosensitive tissue which responds and adapts dynamically to its mechanical environment, application of mechanical stimuli may enhance endogenous tissue repair. While mechanical loading has been shown to stimulate bone fracture healing, the ability of loading to enhance large bone defect regeneration has not been evaluated. The goal of this thesis was to evaluate the ability of sustained osteogenic growth factor delivery and functional biomechanical loading to stimulate vascularized repair of large bone defects in a rat segmental defect model. First, we evaluated the hypothesis that the relationship between protein dose and regenerative efficacy depends on delivery system. We determined the dose-response relationship between dose of recombinant human bone morphogenetic protein-2 (rhBMP-2) and bone regeneration in a hybrid alginate-based protein delivery system and compared with the current clinically-used collagen sponge. The hybrid delivery system improved bone formation and reduced the effective dose due to its sustained delivery properties in vivo. Next, we tested the hypothesis that transfer of compressive ambulatory loads during segmental defect repair enhances bone formation and subsequent limb regeneration. We found that delayed application of axial loads enhanced bone regeneration by altering bone formation, tissue differentiation and remodeling, and local strain distribution. Finally, we evaluated the hypothesis that in vivo mechanical loading can enhance neovascular growth to influence bone formation. We found that early mechanical loading disrupted neovascular growth, resulting in impaired bone healing, while delayed loading induced vascular remodeling and enhanced bone formation. Together, this thesis presents the effects of dose and delivery system on BMP-mediated bone regeneration and demonstrates for the first time the effects of in vivo mechanical loading on vascularized regeneration of large bone defects.

Thesis (M.S.)--University of Louisville, 1998. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.S.)--University of Louisville, 1998. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Akademisk avhandling--Uppsala. / Extra t.p., with thesis statement, inserted. Bibliography: p. 73-76.

Akademisk avhandling--Uppsala. / Extra t.p., with thesis statement, inserted. Bibliography: p. 73-76.

Photocopy of typescript. / Digitized by Kansas Correctional Industries

published_or_final_version / abstract / Dentistry / Doctoral / Doctor of Philosophy