Morris H L, Reed C I, Haycock J W, Reilly G C
Department of Engineering Materials, Kroto Research Institute, University of Sheffield, Broad Lane, UK.
Proc Inst Mech Eng H. 2010 Dec;224(12):1509-21. doi: 10.1243/09544119JEIM751.
Matrix production by tissue-engineered bone is enhanced when the growing tissue is subjected to mechanical forces and/or fluid flow in bioreactor culture. Cells deposit collagen and mineral, depending upon the mechanical loading that they receive. However, the molecular mechanisms of flow-induced signal transduction in bone are poorly understood. The hyaluronan (HA) glycocalyx has been proposed as a potential mediator of mechanical forces in bone. Using a parallel-plate flow chamber the effects of removal of HA on flow-induced collagen production and NF-kappaB activation in MLO-A5 osteoid osteocytes were investigated. Short periods of fluid flow significantly increased collagen production and induced translocation of the NF-kappaB subunit p65 to the cell's nuclei in 65 per cent of the cell population. Enzymatic removal of the HA coat and antibody blocking of CD44 (a transmembrane protein that binds to HA) eliminated the fluid-flow-induced increase in collagen production but had no effect on the translocation of p65. HA and CD44 appear to play roles in transducing the flow signals that modulate collagen production over long-term culture but not in the short-term flow-induced activation of NF-kappaB, implying that multiple signalling events are initiated from the commencement of flow. Understanding the mechanotransduction events that enable fluid flow to stimulate bone matrix production will allow the optimization of bioreactor design and flow profiles for bone tissue engineering.
当生长中的组织在生物反应器培养中受到机械力和/或流体流动作用时，组织工程骨的基质生成会得到增强。细胞会根据所承受的机械负荷来沉积胶原蛋白和矿物质。然而，骨骼中流体诱导信号转导的分子机制目前还知之甚少。有人提出透明质酸（HA）糖萼可能是骨骼中机械力的潜在介质。利用平行板流动腔，研究了去除HA对MLO - A5类骨质骨细胞中流体诱导的胶原蛋白生成和核因子-κB（NF-κB）激活的影响。短时间的流体流动显著增加了胶原蛋白的生成，并使65%的细胞群体中NF-κB亚基p65向细胞核发生易位。酶法去除HA外衣以及用抗体阻断CD44（一种与HA结合的跨膜蛋白）消除了流体流动诱导的胶原蛋白生成增加，但对p65的易位没有影响。在长期培养中，HA和CD44似乎在转导调节胶原蛋白生成的流动信号中发挥作用，但在短期流体诱导的NF-κB激活中不起作用，这意味着从流动开始就启动了多个信号事件。了解使流体流动能够刺激骨基质生成的机械转导事件，将有助于优化用于骨组织工程的生物反应器设计和流动模式。
