Engineering functional anisotropy in chondrocyte- and MSC-laden hydrogels

描述（由申请人提供）： 关节软骨排列在关节的表面，并起到传递与关节负荷相关的力的作用。由于其较差的愈合能力，对基于细胞的修复策略的需求日益增长。考虑到天然组织的机械作用，使用工程构建体成功置换关节软骨将需要具有功能性机械特性的生长组织。在这项研究中，我们提出了软骨细胞或间充质干细胞（可以进行软骨分化）在水凝胶环境（琼脂糖和自组装肽水凝胶）的组合，并专注于这些结构的压缩和拉伸性能的发展。成熟软骨的拉伸性能是各向异性的，特别是在浅表区，并出现在青春期的成熟与关节负荷。借用这个发展的概念，我们提出了一种新的生物反应器系统，旨在重现两个接触关节软骨层之间发生的滑动接触。使用该生物反应器，将评估MSC的软骨细胞生物合成和软骨形成分化作为预孵育期和滑动持续时间和滑动不稳定性的函数。假设基因表达和分化的模式将由凝胶中的位置与施加的接触的关系决定，其中增强发生在接触线下方和沿着，特别是在表层中。随后的长期研究将利用这些优化的加载方案来指导MSC和软骨细胞负载的水凝胶构建体的压缩和拉伸（在滑动方向上）机械性能的增加。此外，假设这些结构将表现出增强的胶原含量以及在滑动接触方向上的平行胶原纤维取向。本申请检查了软骨细胞和MSC负载的水凝胶实现软骨样拉伸特性的能力，并通过在新型滑动接触生物反应器系统中培养来在这些构建体中灌输各向异性。这些研究将有助于深入了解软骨分化和成熟的机制。如果实现，该建议的具体目标将进一步促进我们的努力，以产生临床相关的软骨细胞和MSC负载的功能性软骨替代品，表现出复杂的材料特性和各向异性，定义了天然组织，并为其成熟功能所必需。

DESCRIPTION (provided by applicant): Articular cartilage lines the surfaces of joints and functions to transmit the forces associated with joint loading. Limited by its poor healing capacity, there exists a growing demand for cell-based strategies for repair. Given the mechanical role of the native tissue, the successful replacement of articular cartilage using engineered constructs will require grown tissue possessing functional mechanical properties. In this study, we propose the combination of chondrocytes or mesenchymal stem cells (which can undergo chondrogenic differentiation) in a hydrogel environment (agarose and self-assembling peptide hydrogels), and focus on the development of compressive and tensile properties of these constructs. Tensile properties in mature cartilage are anisotropic, particularly in the superficial zone, and emerge during adolescence as maturation occurs with joint loading. Borrowing from this developmental concept, we suggest a novel bioreactor system designed to recapitulate the sliding contact that occurs between two contacting articular cartilage layers. Using this bioreactor, chondrocyte biosynthesis and chondrogenic differentiation of MSCs will be valuated as a function of pre-incubation period and duration and intermittency of sliding. It is hypothesized that the patterns of gene expression and differentiation will be dictated by the relation of the position in the gel to the applied contact, with enhancements occurring beneath and along the line of contact, particularly in the superficial layer. Subsequent long-term studies will utilize these optimized loading protocols to direct the increase the compressive and tensile (in the direction of sliding) mechanical properties of MSC- and chondrocyte-laden hydrogel constructs. Furthermore, it is hypothesized that these constructs will exhibit enhanced collagen content as well as a parallel collagen fiber orientation in the direction of sliding contact. This application examines the ability of chondrocyte- and MSC-laden hydrogels to achieve cartilage-like tensile properties, and to instill anisotropy in these constructs via culture in a novel sliding contact bioreactor system. These studies will provide insight into the mechanisms of cartilage differentiation and maturation. If realized, the specific aims of this proposal will further our efforts to produce clinically relevant chondrocyteand MSC-laden functional cartilage replacements that exhibit the complex material properties and anisotropies that define the native tissue and are necessary for its mature function.