Bone marrow mesenchymal stem/stromal cells (MSCs) maintain bone homeostasis and repair through the ability to expand in response to mitotic stimuli and differentiate into skeletal lineages. Signalling mechanisms that enable precise control of MSC function remain unclear. Here we report that by initially examining differences in signalling pathway expression profiles of individual MSC clones, we identified a previously unrecognised signalling mechanism regulated by epidermal growth factor (EGF) in primary human MSCs. We demonstrate that EGF is able to activate β-catenin, a key component of the canonical Wnt signalling pathway. EGF is able to induce nuclear translocation of β-catenin in human MSCs but does not drive expression of Wnt target genes or T cell factor (TCF) activity in MSC reporter cell lines. Using an efficient Design of Experiments (DoE) statistical analysis, with different combinations and concentrations of EGF and Wnt ligands, we were able to confirm that EGF does not influence the Wnt/β-catenin pathway in MSCs. We show that the effects of EGF on MSCs are temporally regulated to initiate early "classical" EGF signalling mechanisms (e.g via mitogen activated protein kinase) with delayed activation of β-catenin. By RNA-sequencing, we identified gene sets that were exclusively regulated by the EGF/β-catenin pathway, which were distinct from classical EGF-regulated genes. However, subsets of classical EGF gene targets were significantly influenced by EGF/β-catenin activation. These signalling pathways cooperate to enable EGF-mediated proliferation of MSCs by alleviating the suppression of cell cycle pathways induced by classical EGF signalling.

中文翻译：

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表皮生长因子可以通过β-catenin信号传导，独立于经典Wnt信号传导控制间充质干细胞的增殖。

骨髓间充质干/基质细胞（MSC）通过响应有丝分裂刺激而扩展并分化为骨骼谱系的能力来维持骨稳态和修复。能够精确控制MSC功能的信号机制尚不清楚。在这里，我们报告说，通过最初检查各个MSC克隆的信号传导途径表达谱的差异，我们发现了原发性人类MSC中由表皮生长因子（EGF）调控的先前无法识别的信号传导机制。我们证明EGF能够激活β-catenin，这是经典Wnt信号通路的关键组成部分。EGF能够诱导人MSC中β-catenin的核易位，但不会在MSC报告细胞系中驱动Wnt靶基因的表达或T细胞因子（TCF）活性。使用有效的实验设计（DoE）统计分析，以及EGF和Wnt配体的不同组合和浓度，我们能够确认EGF不会影响MSC中的Wnt /β-catenin途径。我们显示，EGF对MSC的影响在时间上受到调节，以启动早期的“经典” EGF信号传导机制（例如通过有丝分裂原激活的蛋白激酶），并延迟了β-catenin的激活。通过RNA测序，我们确定了仅受EGF /β-catenin途径调控的基因集，这与经典的EGF调控基因不同。但是，经典EGF基因靶标的子集受EGF /β-catenin激活的影响很大。