Bio-Fabrication of Tissue Engineering Scaffolds

数以百万计的人遭受组织/器官损伤，包括周围神经损伤、脊髓损伤、骨关节炎和心脏病发作。组织/器官移植是治疗这些类型损伤的金标准，但由于供体组织/器官的可用性有限，作为一种选择受到严重限制。其他治疗方法包括手术调整神经末梢，抗炎甲基强的松龙疗法，用钢或其他人造材料制成的假体植入物代替关节，以及抗凝血药物和血管成形术。然而，这些治疗后的恢复水平是高度可变的，功能的恢复几乎从来没有完全。组织工程（TE）是一个新兴的领域，其目标是生产可以与患者一起生长的组织/器官替代品或支架，最终提供永久的解决方案，从而改进当前的治疗方法。组织支架的设计和制造已被证明是一项具有挑战性的任务，其临床应用的进展受到严重限制。一个重要的障碍是无法制造具有模仿天然组织/器官的结构和细胞组织的支架。

INTRODUCTION: Millions of people suffer from tissue/organ injuries, including peripheral nerve injuries, spinal cord injury, osteoarthritis, and heart attacks. Tissue/organ transplantation is the gold standard to treat some of these types of injuries but is severely restricted as an option due to the limited availability of donor tissues/organs. Other treatment approaches include surgically realigning nerve endings, anti-inflammatory methylprednisolone therapy, replacing joints with prosthetic implants made from steel or other artificial materials, and clot-busting medicines and angioplasty. However, the level of recovery following these treatments is highly variable and the return of function is almost never complete. Tissue engineering (TE) is an emerging field that aims to produce tissue/organ substitutes or scaffolds that can grow with patients, ultimately providing a permanent solution and thus improving upon current treatment approaches. The design and fabrication of tissue scaffolds has proven to be a challenging task that has significantly limited progress towards clinical applications. An important barrier is the inability to fabricate scaffolds with structures and cell organizations that mimic those of native tissues/organs. OBJECTIVES: The long-term goal of this research program is to advance the theoretical and practical basis of bio-fabricating scaffolds for TE applications, by which living cells are incorporated into the scaffolds during their fabrication. Over the next five years, the research aims to develop novel methods or tools to address three key issues with respect to scaffold bio-fabrication. Specifically, the short-term objectives are to: (1) develop methods to improve cell viability so that more cells survive the process and play a role in the subsequent healing process; (2) manipulate multiple materials/cells for mimicking the complicated structure of native tissues/organs; and (3) develop novel methods that allow for the creation of patterned vascular networks within scaffolds during their fabrication. Objective 1 builds on work conducted during my previous NSERC Discovery grant, recognizing that cells are subjected to sustained process-induced forces (e.g., shear stress) during biofabrication and, as a result, may not survive the process. Objective 2 addresses the fact that existing approaches lack the ability to manipulate materials/cells in a controllable manner and, as a result, scaffold fabrication is largely limited to simple structures. Objective 3 recognizes that vascularization within scaffolds is critical to supply cells with oxygen and nutrients and to transport the waste products of cells; however, the vasculatures formed within scaffolds by existing methods are inadequate, and this has significantly limited the function of scaffolds in the healing process, particularly in the repair of such thick and large tissues/organs as hearts. IMPACT: This research will lead to the development of new techniques and tools to advance the bio-fabrication of cell-encapsulated scaffolds, as well as novel scaffolds, for wide TE applications including peripheral-nerve repair, articular-cartilage repair, spinal-cord-injury repair, and treatment of heart attack. As such, the primary stakeholders are the large number of Canadian citizens who suffer from tissue/organ injuries as well as health researchers and practitioners and industry partners in related areas. This research will also involve the training of graduate students to meet the increasing demand for highly qualified personnel in TE.