Department of Biomedical Engineering, Tufts University, Medford, Massachusetts 02155, USA.
Tissue Eng Part A. 2013 Sep;19(17-18):1889-908. doi: 10.1089/ten.tea.2012.0425.rev. Epub 2013 Jun 5.
Although adult stem cell transplantation has been implemented as a therapy for tissue repair, it is limited by the availability of functional adult stem cells. A potential approach to generate stem and progenitor cells may be to modulate the differentiated status of somatic cells. Therefore, there is a need for a better understanding of how the differentiated phenotype of mature cells is regulated. We hypothesize that bioelectric signaling plays an important role in the maintenance of the differentiated state, as it is a functional regulator of the differentiation process in various cells and tissues. In this study, we asked whether the mature phenotype of osteoblasts and adipocytes derived from human mesenchymal stem cells (hMSCs) could be altered by modulation of their membrane potential. hMSC-derived osteoblasts and adipocytes were depolarized by treatment with ouabain, a Na(+)/K(+) ATPase inhibitor, or by treatment with high concentrations of extracellular K(+). To characterize the effect of voltage modulation on the differentiated state, the depolarized cells were evaluated for (1) the loss of differentiation markers; (2) the up-regulation of stemness markers and stem properties; and (3) differences in gene expression profiles in response to voltage modulation. hMSC-derived osteoblasts and adipocytes exhibited significant down-regulation of bone and fat tissue markers in response to depolarization, despite the presence of differentiation-inducing soluble factors, suggesting that bioelectric signaling overrides biochemical signaling in the maintenance of cell state. Suppression of the osteoblast or adipocyte phenotype was not accompanied by up-regulation of genes associated with the stem state. Thus, depolarization does not activate the stem cell genetic signature and, therefore, does not induce a full reprogramming event. However, after transdifferentiating the depolarized cells to evaluate for multi-lineage potential, depolarized osteoblasts demonstrated improved ability to achieve correct adipocyte morphology compared with nondepolarized osteoblasts. The present study thus demonstrates that depolarization reduces the differentiated phenotype of hMSC-derived cells and improves their transdifferentiation capacity, but does not restore a stem-like genetic profile. Through global transcript profiling of depolarized osteoblasts, we identified pathways that may mediate the effects of voltage signaling on cell state, which will require a detailed mechanistic inquiry in future studies.
虽然成人干细胞移植已被应用于组织修复的治疗中，但它受到功能性成人干细胞的可用性限制。生成干细胞和祖细胞的一种潜在方法可能是调节体细胞的分化状态。因此，需要更好地了解成熟细胞的分化表型是如何被调控的。我们假设生物电信号在维持分化状态方面发挥着重要作用，因为它是各种细胞和组织中分化过程的功能调节剂。在这项研究中，我们询问了人骨髓间充质干细胞（hMSC）来源的成骨细胞和脂肪细胞的成熟表型是否可以通过调节其膜电位来改变。用哇巴因（Na+/K+ATP 酶抑制剂）或高浓度细胞外 K+处理 hMSC 来源的成骨细胞和脂肪细胞可使其去极化。为了研究电压调节对分化状态的影响，评估去极化细胞的以下方面：（1）分化标志物的丢失；（2）干性标志物和干性特征的上调；以及（3）对电压调节的基因表达谱差异。尽管存在诱导分化的可溶性因子，但 hMSC 来源的成骨细胞和脂肪细胞在去极化后表现出显著下调骨和脂肪组织标志物，这表明生物电信号在维持细胞状态方面优于生化信号。成骨细胞或脂肪细胞表型的抑制并不伴有与干细胞状态相关基因的上调。因此，去极化不会激活干细胞的遗传特征，因此不会诱导完全的重编程事件。然而，在对去极化细胞进行转分化以评估多系潜能后，与未去极化的成骨细胞相比，去极化的成骨细胞表现出改善的获得正确脂肪细胞形态的能力。因此，本研究表明，去极化降低了 hMSC 来源细胞的分化表型并提高了其转分化能力，但不会恢复类似干细胞的遗传特征。通过对去极化成骨细胞进行全转录组谱分析，我们确定了可能介导电压信号对细胞状态影响的途径，这将需要在未来的研究中进行详细的机制探究。
