Griffin F E, Schiavi J, McDevitt T C, McGarry J P, McNamara L M
Biomechanics Research Centre (BMEC), Biomedical Engineering, College of Engineering and Informatics, National University of Ireland, Galway, Ireland.
Gladstone Institute, University of California, San Francisco, USA.
J Biomech. 2017 Jul 5;59:71-79. doi: 10.1016/j.jbiomech.2017.05.014. Epub 2017 May 22.
Osteogenesis of mesenchymal stem cells (MSC) can be regulated by the mechanical environment. MSCs grown in 3D spheroids (mesenspheres) have preserved multi-lineage potential, improved differentiation efficiency, and exhibit enhanced osteogenic gene expression and matrix composition in comparison to MSCs grown in 2D culture. Within 3D mesenspheres, mechanical cues are primarily in the form of cell-cell contraction, mediated by adhesion junctions, and as such adhesion junctions are likely to play an important role in the osteogenic differentiation of mesenspheres. However the precise role of N- and OB-cadherin on the biomechanical behaviour of mesenspheres remains unknown. Here we have mechanically tested mesenspheres cultured in suspension using parallel plate compression to assess the influence of N-cadherin and OB-cadherin adhesion junctions on the viscoelastic properties of the mesenspheres during osteogenesis. Our results demonstrate that N-cadherin and OB-cadherin have different effects on mesensphere viscoelastic behaviour and osteogenesis. When OB-cadherin was silenced, the viscosity, initial and long term Young's moduli and actin stress fibre formation of the mesenspheres increased in comparison to N-cadherin silenced mesenspheres and mesenspheres treated with a scrambled siRNA (Scram) at day 2. Additionally, the increased viscoelastic material properties correlate with evidence of calcification at an earlier time point (day 7) of OB-cadherin silenced mesenspheres but not Scram. Interestingly, both N-cadherin and OB-cadherin silenced mesenspheres had higher BSP2 expression than Scram at day 14. Taken together, these results indicate that N-cadherin and OB-cadherin both influence mesensphere biomechanics and osteogenesis, but play different roles.
间充质干细胞（MSC）的成骨作用可受机械环境调节。与在二维培养中生长的MSC相比，在三维球体（间球）中生长的MSC保留了多谱系潜能，提高了分化效率，并表现出增强的成骨基因表达和基质组成。在三维间球内，机械信号主要以细胞间收缩的形式存在，由黏附连接介导，因此黏附连接可能在间球的成骨分化中发挥重要作用。然而，N-钙黏蛋白和骨钙黏蛋白对间球生物力学行为的确切作用仍不清楚。在此，我们使用平行板压缩对悬浮培养的间球进行了力学测试，以评估N-钙黏蛋白和骨钙黏蛋白黏附连接在成骨过程中对间球黏弹性特性的影响。我们的结果表明，N-钙黏蛋白和骨钙黏蛋白对间球黏弹性行为和成骨作用有不同影响。当骨钙黏蛋白沉默时，与N-钙黏蛋白沉默的间球和用乱序小干扰RNA（Scram）处理的间球相比，间球在第2天的黏度、初始和长期杨氏模量以及肌动蛋白应力纤维形成增加。此外，间球黏弹性材料特性的增加与骨钙黏蛋白沉默的间球在更早时间点（第7天）的钙化证据相关，但Scram处理的间球无此现象。有趣的是，在第14天，N-钙黏蛋白和骨钙黏蛋白沉默的间球均比Scram处理的间球有更高的骨涎蛋白2（BSP2）表达。综上所述，这些结果表明，N-钙黏蛋白和骨钙黏蛋白均影响间球生物力学和成骨作用，但发挥不同作用。
