Trinity Centre for Biomedical Engineering, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland. Department of Mechanical and Manufacturing Engineering, School of Engineering, Trinity College Dublin, Ireland.
Biofabrication. 2020 May 12;12(3):035011. doi: 10.1088/1758-5090/ab8708.
Engineering constructs that mimic the complex structure, composition and biomechanics of the articular cartilage represents a promising route to joint regeneration. Such tissue engineering strategies require the development of biomaterials that mimic the mechanical properties of articular cartilage whilst simultaneously providing an environment supportive of chondrogenesis. Here three-dimensional (3D) bioprinting is used to develop polycaprolactone (PCL) fibre networks to mechanically reinforce interpenetrating network (IPN) hydrogels consisting of alginate and gelatin methacryloyl (GelMA). Inspired by the significant tension-compression nonlinearity of the collagen network in articular cartilage, we printed reinforcing PCL networks with different ratios of tensile to compressive modulus. Synergistic increases in compressive modulus were observed when IPN hydrogels were reinforced with PCL networks that were relatively soft in compression and stiff in tension. The resulting composites possessed equilibrium and dynamic mechanical properties that matched or approached that of native articular cartilage. Finite Element (FE) modelling revealed that the reinforcement of IPN hydrogels with specific PCL networks limited radial expansion and increased the hydrostatic pressure generated within the IPN upon the application of compressive loading. Next, multiple-tool biofabrication techniques were used to 3D bioprint PCL reinforced IPN hydrogels laden with a co-culture of bone marrow-derived stromal cells (BMSCs) and chondrocytes (CCs). The bioprinted biomimetic composites were found to support robust chondrogenesis, with encapsulated cells producing hyaline-like cartilage that stained strongly for sGAG and type II collagen deposition, and negatively for type X collagen and calcium deposition. Taken together, these results demonstrate how 3D bioprinting can be used to engineer constructs that are both pro-chondrogenic and biomimetic of the mechanical properties of articular cartilage.
工程构建体模仿关节软骨的复杂结构、组成和生物力学特性，代表了关节再生的一种有前途的途径。这种组织工程策略需要开发模仿关节软骨机械性能的生物材料，同时提供支持软骨生成的环境。在这里，我们使用三维（3D）生物打印来开发聚己内酯（PCL）纤维网络，以机械增强由藻酸盐和明胶甲基丙烯酰（GelMA）组成的互穿网络（IPN）水凝胶。受关节软骨中胶原网络显著的拉压非线性的启发，我们打印了具有不同拉伸与压缩模量比的增强 PCL 网络。当 IPN 水凝胶用在拉伸时较硬而在压缩时较软的 PCL 网络增强时，观察到压缩模量的协同增加。所得复合材料具有平衡和动态机械性能，与天然关节软骨相匹配或接近。有限元（FE）建模表明，用特定的 PCL 网络增强 IPN 水凝胶可以限制径向膨胀，并在施加压缩载荷时增加 IPN 内产生的静水压力。接下来，使用多工具生物制造技术 3D 生物打印 PCL 增强的 IPN 水凝胶，其中负载骨髓基质细胞（BMSCs）和软骨细胞（CCs）的共培养物。发现生物打印的仿生复合材料支持强大的软骨生成，包封的细胞产生强 sGAG 和 II 型胶原沉积染色的透明样软骨，以及对 X 型胶原和钙沉积呈阴性。总的来说，这些结果表明 3D 生物打印如何可用于工程构建体，这些构建体既具有软骨生成性，又模仿关节软骨的机械性能。
