Vascularization and Bone Repair

描述（由申请人提供）：骨修复的要求，无论是由宿主提供还是在植入式组织工程结构中提供，包括细胞外基质支架、细胞、功能性血管供应和骨诱导因子。在这些基本元素中，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，二维组织学分析已被用于评估血管密度。然而，这种方法充其量是半定量的，不容易对整个组织进行分析。高分辨率三维微计算机断层扫描（micro-CT）成像与造影剂灌注相结合，有可能克服这些限制，量化血管生长。最近体内微ct系统的发展进一步提供了无创监测体内骨缺损内矿化基质形成的机会。本应用程序的目标是结合和扩展这些方法，以更好地理解在一个定义良好的体内骨组织工程模型中血管化和矿化之间的时间和空间关系。具体目的是：1 .量化三维血管生长和矿化基质形成的支架植入临界尺寸的节段性骨缺损；分析多孔支架结构对血管侵入和矿化的影响；测试在植入体中添加细胞成分对节段性缺损修复过程中血管化和矿化的影响。

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.