McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, University of Pennsylvania, 36th Street and Hamilton Walk, Philadelphia, PA 19104, USA.
Eur Cell Mater. 2010 Feb 26;19:72-85. doi: 10.22203/ecm.v019a08.
Mesenchymal stem cells (MSCs) are an attractive cell source for cartilage tissue engineering given their ability to undergo chondrogenesis in 3D culture systems. Mechanical forces play an important role in regulating both cartilage development and MSC chondrogenic gene expression, however, mechanical stimulation has yet to enhance the mechanical properties of engineered constructs. In this study, we applied long-term dynamic compression to MSC-seeded constructs and assessed whether varying pre-culture duration, loading regimens and inclusion of TGF-beta3 during loading would influence functional outcomes and these phenotypic transitions. Loading initiated before chondrogenesis decreased functional maturation, although chondrogenic gene expression increased. In contrast, loading initiated after chondrogenesis and matrix elaboration further improved the mechanical properties of MSC-based constructs, but only when TGF-beta3 levels were maintained and under specific loading parameters. Although matrix quantity was not affected by dynamic compression, matrix distribution, assessed histologically and by FT-IRIS analysis, was significantly improved on the micro- (pericellular) and macro- (construct expanse) scales. Further, whole genome expression profiling revealed marked shifts in the molecular topography with dynamic loading. These results demonstrate, for the first time, that dynamic compressive loading initiated after a sufficient period of chondro-induction and with sustained TGF-beta exposure enhances matrix distribution and the mechanical properties of MSC-seeded constructs.
间充质干细胞（MSCs）在 3D 培养系统中具有向软骨分化的能力，因此成为软骨组织工程中极具吸引力的细胞来源。机械力在调节软骨发育和 MSC 软骨生成基因表达方面起着重要作用，然而，机械刺激尚未增强工程化构建体的机械性能。在这项研究中，我们对 MSC 接种的构建体施加长期动态压缩，并评估在加载过程中改变预培养时间、加载方案和 TGF-β3 的包含情况是否会影响功能结果和这些表型转变。在软骨生成之前开始加载会降低功能成熟度，尽管软骨生成基因表达增加。相比之下，在软骨生成和基质形成之后开始加载可以进一步提高基于 MSC 的构建体的机械性能，但仅在维持 TGF-β3 水平和特定加载参数的情况下。虽然动态压缩不会影响基质数量，但通过组织学和 FT-IRIS 分析评估的基质分布在微观（细胞周）和宏观（构建体扩张）尺度上得到了显著改善。此外，全基因组表达谱分析显示，动态加载会导致分子拓扑结构发生明显变化。这些结果首次证明，在充分的软骨诱导期后开始的动态压缩加载，并持续暴露于 TGF-β 会增强 MSC 接种构建体的基质分布和机械性能。
