Microengineered Osteons for Bone Tissue Engineering

描述（由申请人提供）：血管化仍然是阻碍大多数骨组织工程构建体转化为临床实践的主要障碍。大结构的预血管化具有很大的潜力来改善整个支架的功能性脉管系统，以快速促进与周围组织的整合并避免支架核心中的坏死。在我们以前的研究中，我们已经开发了微工程化凝胶来共培养人内皮祖细胞（hEPCs）和人间充质干细胞（hMSC）以工程化微血管，但观察到有限的吻合潜力。我们还开发了许多方法，其中工程化水凝胶可以组装成分级组织支架以产生血管化构建体，并确定需要使用机械坚固的支架来保护微脉管系统的结构完整性。我们的工作中仍然存在的一个主要挑战是，尽管初步改造了 将细胞整合到功能性微血管中，但尚未观察到有效整合到大血管中。该更新提案的主要前提是，通过结合可灌注血管移植物，将工程结构的微血管系统连接到大型宿主血管，我们将能够解决这一具有挑战性的问题。在这个更新项目中，我们建议设计一种骨支架，将微血管与可移植的大血管移植物整合在一起，以愈合关键尺寸的节段性骨缺损。该构建体将在体外开发，使得凝胶中的微血管毛细血管与大血管移植物连接，随后与体内宿主血管连接。我们的假设是，这种构建体可以通过在移植后立即恢复血液供应来显著改善与宿主组织的整合。为了验证我们的假设，我们的团队由组织工程，生物材料，微工程和骨科专家组成，提出了以下目标：目标1。开发用于制造可植入预血管化骨结构的组件。目标2.体外工程化和表征可生物降解的预血管化骨结构。目标3。评价可植入预血管化骨结构修复关键尺寸节段性骨缺损的有效性。这项工作的完成将是一个范式的转变和一个里程碑式的成就，努力临床治疗骨临界尺寸缺损。

DESCRIPTION (provided by applicant): Vascularization remains the principle obstacle that impedes the translation of most bone tissue engineered constructs to clinical practice. Pre-vascularization of large constructs has great potential to improve functional vasculature throughout the scaffold to rapidly facilitate integration with the surrounding tissue and circumvent necrosis in the core of the scaffold. In our previous studies, we have developed microengineered gels to co- culture human endothelial progenitor cells (hEPCs) and human mesenchymal stem cells (hMSCs) to engineer microvasculature, but observed limited anastomotic potential. We have also developed a number of approaches in which engineered hydrogels can be assembled into graded tissue scaffolds to generate vascularized constructs, and determined the need to protect structural integrity of microvasculature using mechanically-robust scaffolds. A major remaining challenge in our work is that despite the initial remodeling of the cells into functioning microvessels, efficient integration to major vessels has not been observed. The main premise of this renewal proposal is that by incorporating a perfusable vessel graft that connects the microvasculature of the engineered construct to large host vessels, we will be able to address this challenging issue. In this renewal project, we propose to engineer a bone scaffold that integrates microvasculature with a surgically-anastomizable large vessel graft to heal critical size segmental bone defects. This construct will be developed in vitr such that the microvascular capillaries in gels connect with the large vessel graft and subsequently to the host vessel in vivo. Our hypothesis is this construct can substantially improve on the integration to the host tissue by restoring blood supply immediately after transplantation. To test our hypothesis, our team comprised of experts in tissue engineering, biomaterials, microengineering, and orthopedics proposes the following aims: Aim 1. Develop components for fabrication of surgically-anastomizable pre- vascularized bone construct. Aim 2. Engineer and characterize surgically-anastomizable pre-vascularized bone construct in vitro. Aim 3. Evaluate the efficiency of surgically-anastomizable pre-vascularized bone construct in repair of critical size segmental bone defects. The completion of this work will be a paradigm shift and a landmark achievement in efforts to clinical treatments for bone critical size defects.