Bone Regeneration Using Osteogenic and Vasculogenic Tissue Modules

描述（由申请人提供）：显然需要改进的骨移植替代物，特别是对于难以实现完全桥接的大缺损。目前的临床治疗受到自体移植组织的有限可用性和同种异体方法的不一致有效性的阻碍。越来越明显的是，再生组织的血管化是一个主要障碍，因为大的缺损需要伴随的血液供应来实现完全愈合。最近一个很有前途的策略是内皮细胞（EC）和间充质干细胞（MSC）的共同移植，以促进血管和骨形成。该提案将这种方法与创新的基于生物材料的系统相结合，以将成骨和血管生成祖细胞局部递送到大的骨缺损。我们已经开发出一种方法，将细胞嵌入基于蛋白质的微环境中，该微环境提供3D细胞外基质的结构和支持，同时还通过细胞-基质相互作用提供指导性线索。重要的是，这些模块是离散的“微珠”（直径200 - 50微米）的形式，可以单独创建和培养，但可以组合和浓缩成多组分糊剂，直接输送到骨缺损，而不需要破坏细胞-基质接触。我们的一般假设是，由于细胞之间的旁分泌相互作用及其产生血管化骨组织的组合能力，将成骨和血管生成模块作为多相组织一起递送将增强原位成骨。该项目有三个具体目标。在SA 1中，我们将通过系统地检查最有利于所需组织特异性功能的细胞和基质组合物，创建和表征分别促进包埋细胞的成骨和血管生成功能的蛋白质微珠。在SA 2中，我们将结合联合收割机成骨和血管生成微珠，以创建多相组织并在体外表征组织特异性功能，并将研究不同模块类型如何在高密度培养系统中相互作用。在SA 3中，我们将使用已建立的大鼠股骨缺损模型来测试我们的总体假设，并证明多相组织构建体在体内的骨形成能力增强。关键终点包括生物力学活性骨、血管化骨和代谢活性骨的速率和程度的量化指标。该项目采用模块化组织工程的有吸引力的功能，并利用我们对EC和MSC之间的旁分泌相互作用的理解的最新进展，这在骨再生中很重要。因此，它有可能改善最具挑战性的骨科缺陷的治疗，并可能对肌肉骨骼损伤的临床治疗产生重要影响。

DESCRIPTION (provided by applicant): There is a clear need for improved bone grafting substitutes, in particular for large defects in which complete bridging is difficult to achieve. Current clinical therapies are hampered by limited availability of autograft tissue and inconsistent effectiveness of allogeneic approaches. It has become increasingly evident that vascularization of the regenerating tissue is a main hurdle, since large defects require a concomitant blood supply to achieve complete healing. A promising recent strategy is the co-transplantation of endothelial cells (EC) and mesenchymal stem cells (MSC) to promote both blood vessel and bone formation. This proposal combines this approach with an innovative biomaterials-based system to deliver both osteogenic and vasculogenic progenitor cells locally to large bone defects. We have developed a method to embed cells in protein-based microenvironments that provide the structure and support of a 3D extracellular matrix while also presenting instructive cues through cell-matrix interactions. Importantly, these modules are in the form of discrete "microbeads" (200�50 �m in diameter), which can be created and cultured separately, but can be combined and concentrated into a multi-component paste for direct delivery to bone defects, without the need to disrupt cell-matrix contacts. Our general hypothesis is that delivery of osteogenic and vasculogenic modules together as multiphase tissues will enhance in situ osteogenesis, due to paracrine interactions between the cells and their combined ability to generate vascularized bone tissue. The project has three Specific Aims. In SA1, we will create and characterize protein-based microbeads that separately promote osteogenic and vasculogenic functions of embedded cells, by systematically examining the cell and matrix compositions that are most conducive to the desired tissue-specific functions. In SA2, we will combine osteogenic and vasculogenic microbeads to create multiphase tissues and characterize tissue-specific functions in vitro, and will examine how the different module types interact in a high density culture system. In SA3, we will test our overall hypothesis and demonstrate enhanced bone formation capability of multiphase tissue constructs in vivo, using an established femoral defect model in the rat. Key endpoints include quantified measures of the rate and extent of biomechanically competent, vascularized and metabolically active bone. This project employs attractive features of modular tissue engineering and capitalizes on recent advances in our understanding of paracrine interactions between EC and MSC that are important in bone regeneration. It therefore has the potential to improve treatment of the most challenging orthopaedic defects, and could have important impact on the clinical treatment of musculoskeletal injuries.