Trinity Centre for Bioengineering, School of Engineering, Trinity College Dublin, Ireland.
J Mech Behav Biomed Mater. 2011 Oct;4(7):1257-65. doi: 10.1016/j.jmbbm.2011.04.012. Epub 2011 Apr 22.
Mechanical signals can play a key role in regulating the chondrogenic differentiation of mesenchymal stem cells (MSCs). The objective of this study was to determine if the long-term application of cyclic hydrostatic pressure could be used to improve the functional properties of cartilaginous tissues engineered using bone marrow derived MSCs. MSCs were isolated from the femora of two porcine donors, expanded separately under identical conditions, and then suspended in cylindrical agarose hydrogels. Constructs from both donors were maintained in a chemically defined media supplemented with TGF-β3 for 42 days. TGF-β3 was removed from a subset of constructs from day 21 to 42. Loaded groups were subjected to 10 MPa of cyclic hydrostatic pressurisation at 1 Hz for one hour/day, five days/week. Loading consisted either of continuous hydrostatic pressure (CHP) initiated at day 0, or delayed hydrostatic pressure (DHP) initiated at day 21. Free swelling (FS) constructs were cultured in parallel as controls. Constructs were assessed at days 0, 21 and 42. MSCs isolated from both donors were morphologically similar, demonstrated comparable colony forming unit-fibroblast (CFU-F) numbers, and accumulated near identical levels of collagen and GAG following 42 days of free swelling culture. Somewhat unexpectedly the two donors displayed a differential response to hydrostatic pressure. For one donor the application of CHP resulted in increased collagen and GAG accumulation by day 42, resulting in an increased dynamic modulus compared to FS controls. In contrast, CHP had no effect on matrix accumulation for the other donor. The application of DHP had no effect on either matrix accumulation or construct mechanical properties for both donors. Variability in the response to hydrostatic pressure was also observed for three further donors. In conclusion, this study demonstrates that the application of long-term hydrostatic pressure can be used to improve the functional properties of cartilaginous tissues engineered using bone marrow derived MSCs by enhancing collagen and GAG accumulation. The response to such loading however is donor dependent, which has implications for the clinical utilisation of such a stimulus when engineering cartilaginous grafts using autologous MSCs.
机械信号在调节间充质干细胞（MSCs）的软骨分化中起着关键作用。本研究的目的是确定长期应用循环静压是否可用于改善使用骨髓来源的 MSCs 工程化的软骨组织的功能特性。从两名猪供体的股骨中分离出 MSCs，在相同条件下分别进行扩增，然后悬浮于圆柱形琼脂糖水凝胶中。来自两名供体的构建体均在补充有 TGF-β3 的化学定义培养基中维持 42 天。从第 21 天到第 42 天，从一部分构建体中去除 TGF-β3。加载组每天接受 1 小时、1Hz 的 10MPa 循环静压，每周 5 天。加载要么从第 0 天开始进行连续静压（CHP），要么从第 21 天开始进行延迟静压（DHP）。自由膨胀（FS）构建体作为对照平行培养。在第 0、21 和 42 天评估构建体。从两名供体中分离出的 MSCs 在形态上相似，表现出相当的集落形成单位-成纤维细胞（CFU-F）数量，并且在 42 天的自由膨胀培养后积累了几乎相同水平的胶原蛋白和 GAG。出人意料的是，两名供体对静压表现出不同的反应。对于一名供体，CHP 的应用导致第 42 天胶原蛋白和 GAG 的积累增加，与 FS 对照相比，动态模量增加。相比之下，CHP 对另一名供体的基质积累没有影响。对于两名供体，DHP 的应用对基质积累或构建体机械性能都没有影响。对另外三名供体也观察到了对静压的反应差异。总之，本研究表明，长期应用静压可用于通过增强胶原蛋白和 GAG 的积累来改善使用骨髓来源的 MSCs 工程化的软骨组织的功能特性。然而，这种加载的反应是供体依赖性的，这对使用自体 MSCs 工程化软骨移植物时对这种刺激的临床应用具有影响。
