I-Corps: Tissue-engineering vascular grafts using autologous cell sheets

美国约有1000万人患有外周血管疾病（PVD），每年使用合成或自体静脉移植物进行460，000例血管旁路手术。大隐静脉是最常用的自体移植材料，由于内膜增生，18个月内有50%的失败率。对于不再有静脉可用于旁路的患者，血管外科医生必须使用合成移植物（PTFE或Dacron），这与更高的并发症发生率相关，如闭塞和感染。此外，这些合成移植物通常只能用于旁路内径大于6 mm的血管。所提出的技术/产品由一种新型细胞片衍生的工程化自体血管移植物组成，可以满足对生物反应性血管移植物的迫切临床需求。这有可能克服自体和合成移植物的当前问题：供应有限;自体移植物的长度有限，以及合成移植物的生物相容性差。对所提出的细胞片培养和堆叠系统进行优化，以低成本产生生物响应性的活血管移植物。任何生理相关细胞类型、大小和2D模式的汇合和自组装细胞片层可以在接种后10天内实现。从根本上影响细胞表型和行为的水凝胶基质刚度可以与血管的各个层（例如，图尼卡中膜或图尼卡外膜）的刚度精确匹配。在水凝胶基质平台上生长的细胞片表现出高细胞活力和高度的天然组织重演性质（例如血管），例如细胞排列、细胞外基质组成和机械强度。细胞片层堆叠和滚动过程保留了单个细胞片层模式和细胞活力（99%），以产生结构和生物学相似的血管移植物。该系统可扩展用于高产量制造工艺，以降低成本和制造时间。完全血管化的三维活体组织一直是组织工程领域未解决的难题。所提出的系统可用于设计需要复杂结构以实现适当组织功能的组织替代物。这种多功能技术可能会进一步扩展到目前的心血管应用之外，为其他疾病状态创建组织工程解决方案。

There are approximately 10 million people in the US with peripheral vascular disease (PVD), and 460,000 vascular bypass surgeries are performed annually using either synthetic or autologous venous grafts. Saphenous vein, the most commonly used autograft material, has a 50% failure rate within 18 months due to intimal hyperplasia. For patients who no longer have veins available for bypass, the vascular surgeon must use synthetic grafts (PTFE or Dacron) which are associated with a higher rate of complications such as occlusion and infection. Furthermore, these synthetic grafts can typically only be used to bypass vessels with an internal diameter greater than 6 mm. The proposed technology/product consists of a novel cell sheet-derived engineered autologous vascular graft that can meet this urgent clinical need for biologically responsive vascular grafts. This has the potential to overcome the current problems of autologous and synthetic grafts: limited supply; restricted length of autologous grafts, and poor biocompatibility of synthetic grafts. The proposed cell sheet culture and stacking system was optimized to produce biologically responsive, living vascular grafts at low-cost. Confluent and self-assembled cell sheets of any physiologically relevant cell type, size and 2D pattern can be achieved within 10 days after seeding. Hydrogel substrate stiffness, which fundamentally affects cell phenotype and behavior, can be accurately matched to the stiffness of individual layers of the vessel, e.g. tunica media or tunica adventitia. Cell sheets grown on a hydrogel substrate platform demonstrate high cell viability and a high degree of native tissue recapitulative properties (e.g. blood vessel) such as cell alignment, extracellular matrix composition, and mechanical strength. The cell sheet stacking and rolling process preserves individual cell sheet patterns and cell viability (99%) to produce structurally and biologically similar vascular graft. This system is scalable for high throughput manufacturing processes to lower the cost and fabrication time. Fully vascularized three-dimensional living tissue remains an unsolved challenge in tissue engineering. The proposed system can be utilized for the design of tissue replacements that require complex structures for proper tissue function. This versatile technology may be further expanded beyond the current cardiovascular application to create tissue engineered solutions for other disease states.