Vascularization and Bone Repair

描述(由申请人提供)：骨修复的要求，无论是由宿主提供的，还是在可植入的组织工程构造中提供的，都包括细胞外基质支架、细胞、功能性血管供应和骨诱导因子。在这些基本要素中，血管供应在组织工程的背景下被研究得最少，部分原因是难以量化组织内的三维血管结构。传统上，二维组织学分析被用来评估血管密度。然而，这种方法充其量是半定量的，不容易在整个组织中进行分析。高分辨率3D微计算机断层成像(Micro-CT)结合造影剂灌注有可能克服这些限制来量化血管生长。体内微型CT系统的最新发展进一步提供了无创监测体内骨缺损区矿化基质形成的机会。这项应用的目标是结合和扩展这些方法，以更好地了解在一个明确的活体骨组织工程模型中血管形成和矿化之间的时间和空间关系。本研究的具体目的是：1.定量研究支架内三维血管的生长和矿化基质的形成；2.分析多孔支架结构对血管侵袭和矿化的影响；3.在节段性骨缺损修复过程中，在植入的支架中加入细胞成分对血管形成和矿化的影响。 这项拟议的研究具有重要意义，因为它将定量三维成像技术与具有良好特性的活体模型相结合，以更好地了解骨修复所必需的两个过程之间的相互关系：血管形成和矿化。缺乏强有力的血管反应可能是骨修复延迟或失败的重要机制。例如，在纤维组织修复过程中，血管形成和矿化反应的解偶联也是可能的。功能血管供应的恢复是除骨骼外各种组织修复工程中的关键问题。因此，拟议的研究将建立一个有价值的新方法来评估组织工程结构与生命系统的整合。此外，所开发的方法将广泛适用于其他研究领域，包括例如骨折愈合、骨骼发育、血管损伤和肿瘤发生的研究。

DESCRIPTION (provided by applicant): The requirements for bone repair, whether provided by the host or within an implantable tissue-engineered construct, include an extracellular matrix scaffold, cells, a functional vascular supply, and osteoinductive factors. Of these essential elements, vascular supply has been the least studied in the context of tissue engineering in part due to the difficulty in quantifying 3-D vascular structures within tissues. Traditionally, 2-D histological analysis has been used to assess vessel density. However, this approach is semi-quantitative at best and does not easily allow analysis throughout the tissue. High-resolution 3-D microcomputed tomography (micro-CT) imaging coupled with contrast agent perfusion has the potential to overcome these limitations to quantify vascular growth. The recent development of in vivo micro-CT systems has further provided the opportunity to non-invasively monitor mineralized matrix formation within a bone defect in vivo. The goal of this application is to combine and extend these methodologies to better understand the temporal and spatial relationships between vascularization and mineralization in a well defined in vivo bone tissue engineering model. The Specific Aims are to: I. Quantify 3-D vascular growth and mineralized matrix formation within scaffolds implanted into critically-sized segmental bone defects, II. Analyze the influence of porous scaffold architecture on vascular invasion and mineralization, and III. Test the effect of adding a cellular component to implanted constructs on vascularization and mineralization during segmental defect repair. The proposed research is highly significant because it integrates quantitative 3-D imaging techniques with a well characterized in vivo model to better understand the inter-relationship between two processes essential to bone repair: vascularization and mineralization. Lack of a vigorous vascular response may be an important mechanism of delayed or failed bone repair. Decoupling of vascularization and mineralization responses is also possible during for example fibrous tissue repair. The restoration of a functional vascular supply is a critical issue for engineering the repair of a wide variety of tissues in addition to bone. Thus, the proposed studies will establish a valuable new approach for assessing the integration of tissue-engineered constructs into living systems. Furthermore, the developed methodologies will have broad applicability to other research areas, including for example studies on fracture healing, skeletal development, vascular injury, and tumorigenesis.