Total Joint Resurfacing

全关节表面置换 以前修复关节软骨的尝试集中在局部缺损的修复上。之一 局部缺损修复的主要并发症是修复组织与周围天然组织的整合 软骨是不一致的，通常很差，这使得修复部位在生物力学上不稳定， 临床上有效。在整个关节表面已经恶化的严重骨关节炎的情况下， 修复局部软骨缺损的方法不再适用。对于严重的关节炎， 更换是最终的选择，虽然它有一个总体上良好的结果，但仍然存在长期 并发症，包括假体关节面侵蚀， 假体柄这些问题需要翻修手术，这逐渐变得更加困难， 复杂为了解决这个问题，我们提出设计和测试组织工程细胞基质， 用于关节或关节间室的完全表面置换的复合物，其被设计为消除软骨-软骨 整合问题，并提供了一个基于细胞的选择，完全重铺关节，而不完全 取代他们。 组织工程的主要挑战是关节的全软骨表面重建， 有足够厚度和表面积的活软骨组织，覆盖整个关节，以产生软骨 具有适当的机械性能，以支持体内机械需求，并确保 结构与下层骨的整合。该提案的目标是产生功能性的 使用组织工程原理的自体软骨构建体，其中自体细胞，例如 间充质干细胞（MSC）、耳廓或关节软骨细胞用于产生全层软骨。 替换软骨，然后融合并允许整合到软骨下骨上， 用自体工程化软骨替换退化的软骨。 这种方法是基于这样的假设，即生产全层软骨植入物 避免了外侧软骨整合的棘手困难，功能性长期修复将 通过产生生物力学上健全的自体软骨来完成。 这项建议的具体目标是： 1.为了产生可移植的组织工程化软骨构建体：在兔模型中， 培养扩增的软骨细胞将用于产生全厚度（300 μ m）的软骨结构， 足以覆盖整个肱骨髁的区域。待测试的变量包括使用耳或 关节软骨细胞或MSC;基于透明质酸或胶原的支架;以及培养条件的变化 如细胞接种密度、培养基流速和生长因子如TGF-β 1，TGF β 5， 骨形态发生蛋白和欧米茄-3脂肪酸。 1.在软骨表面置换的离体模型中测试准备好的重建结构：植入物 将合成到适当厚度和表面积的材料固定到固定的兔肱骨上 髁突采用四种粘接方法：磷酸钙糊剂、纤维蛋白胶、最后采用零长 交联剂1-乙基-3-{3-二甲基氨基丙基}碳二亚胺，和APTMS-MBA（氨基丙基三甲氧基硅烷亚甲基双丙烯酰胺）， 一种无毒的聚合物粘合剂。将测试这些粘合剂材料的 在体外、器官培养中以及植入无胸腺小鼠宿主后， 6周待测试的生物力学特性包括表面硬度图，以及在 单轴拉伸和水平剪切（破坏）。MRI成像、组织学检查，以及 免疫化学将用于确定软骨厚度的一致性和整合到 软骨下骨 2.在兔体内软骨表面置换模型中测试构建体： 工程化软骨结构将用于在兔子中对整个肱骨髁进行表面置换。植入物 将在植入后4、12、24和48周收获并检查生物力学特性和组织学。 通过使用细胞，生物反应器和成像核心，本提案的目标将更多 容易和有效地完成。核心组件非常适合这个项目，因为 对细胞（软骨细胞和MSC）的高需求，需要生物反应器来制造软骨组织， 结果分析需要成像。 如果这些研究是成功的，后续研究将在一个大的 动物临床前模型，如绵羊或山羊。这项研究的长期目标是提供一个 由活的自体组织组成的严重关节炎的替代治疗 希望在需要进行全关节置换之前能够提供多年的功能使用。

Total Joint Resurfacing Previous attempts to repair articular cartilage have focused on the repair of focal defects. One of the main complications of focal defect repair is that integration of the repair tissue with the surrounding native cartilage is inconsistent and generally poor, which renders the repair site biomechanically unstable not clinically efficacious. In the case of severe osteoarthritis where the entire joint surface has deteriorated, the procedures for repair of focal cartilage defects are no longer applicable. For severe arthritis, total joint replacement is the final option which, although it has a generally good outcome, there are still long-term complications including, erosion of the articulating surface of the prostheses, and breaking or loosening of the prosthetic stem. These problems necessitate revision surgery which is progressively more difficult and complicated. To obviate this problem, we propose to design and test a tissue engineered cell-matrix composite for the total resurfacing of a joint or joint compartment, which is designed to eliminate cartilage-tocartilage integration problems and provide a cell-based option for totally resurfacing joints without totally replacing them. The primary challenges for tissue engineering the total cartilage resurfacing of a joint are to produce viable cartilage tissue of sufficient thickness and surface area to cover an entire joint, to produce cartilage that has appropriate mechanical properties to support the in vivo mechanical demands, and to ensure the integration of the construct with underlying bone. The goal of this proposal is to produce functional autologous cartilage constructs using tissue engineering principles wherein autologous cells, such as Mesenchymal Stem Cells (MSCs), auricular or articular chondrocytes are used to produce full-thickness replacement cartilage and that is then fused and allowed to integrate onto sub-chondral bone, thus totally replacing the deteriorated cartilage with autologous engineered cartilage. This approach is based on the hypothesis that the production of full-thickness cartilage implants obviates the intractable difficulty of lateral cartilage integration, and functional long-term repair will be accomplished by producing biomechanically sound autologous cartilage. The specific aims of this proposal are: 1. To produce implantation-ready tissue engineered cartilage constructs: In a rabbit model, MSCs and culture-expanded chondrocytes will be used to produce full-thickness (300 um) cartilage constructs of sufficient area to cover an entire humeral condyle. Variables to be tested include the use of auricular or articular chondrocytes or MSCs; hyaluronan- or collagen-based scaffolds; and variations in culture conditions such as cell seeding density, medium flow rate, and the addition of growth factors such as TGF-p1, TGFpS, BMPs, and omega-3 fatty acids. 1. To test implantation-ready constructs in an ex vivo model for cartilage resurfacing: Implant materials synthesized to the proper thickness and surface area will be fixed onto explanted rabbit humeral condyles using four adhesive methods: a calcium phosphate paste, fibrin glue, a final using the zero-length cross-linker1-Ethyl-3-{3-dimethylaminopropyl} carbodiimide, and APTMS-MBA (aminopropyltrimethoxysilanemethylenebisacrylamide), a non-toxic polymer adhesive. These adhesive materials will be tested for their biomechanical properties in vitro, in organ culture, and after implantation into athymic mouse hosts for up to 6 weeks. Biomechanical properties to be tested include a map of surface stiffness, and measures under uniaxial tension and horizontal shear (to failure). MRI imaging, histological examination, and immunochemistry will be used to determine the consistency of cartilage thickness and integration into subchondral bone. 2. To test constructs in an in vivo model of cartilage resurfacing in rabbits: Autologous engineered cartilage constructs will be used to resurface entire humeral condyles in rabbits. The implants will be harvested and examined for biomechanical properties and histology at 4, 12, 24 and 48 weeks post-implantation. Through the use of the Cell, Bioreactor and Imaging Cores, the goals of this proposal will be more easily and efficiently accomplished. The Core components are very appropriate for this project as there is a high demand for cells (chondrocytes and MSCs), bioreactors are need to fabricate cartilage tissue, and imaging is needed for outcome analysis. If these studies are successful, the follow-up study would be to reproduce these results in a large animal pre-clinical model such as in sheep or goats. The long-term objective of this study is to provide an alternative treatment for severe arthritis of diarthrodial joints that is composed of living autologous tissue which, hopefully, will provide many years of functional use before the need for total joint replacement.