Stem Cell Biology and Therapy Laboratory of the Key Laboratory for Pediatrics designated by Chinese Ministry of Education and Chongqing Bureau of Education, Department of Orthopaedic Surgery, The Children's Hospital of Chongqing Medical University, Chongqing, China.
J Cell Mol Med. 2013 Sep;17(9):1160-72. doi: 10.1111/jcmm.12097. Epub 2013 Jul 11.
Mesenchymal stem cells (MSCs) are multipotent progenitors, which give rise to several lineages, including bone, cartilage and fat. Epidermal growth factor (EGF) stimulates cell growth, proliferation and differentiation. EGF acts by binding with high affinity to epidermal growth factor receptor (EGFR) on the cell surface and stimulating the intrinsic protein tyrosine kinase activity of its receptor, which initiates a signal transduction cascade causing a variety of biochemical changes within the cell and regulating cell proliferation and differentiation. We have identified BMP9 as one of the most osteogenic BMPs in MSCs. In this study, we investigate if EGF signalling cross-talks with BMP9 and regulates BMP9-induced osteogenic differentiation. We find that EGF potentiates BMP9-induced early and late osteogenic markers of MSCs in vitro, which can be effectively blunted by EGFR inhibitors Gefitinib and Erlotinib or receptor tyrosine kinase inhibitors AG-1478 and AG-494 in a dose- and time-dependent manner. Furthermore, EGF significantly augments BMP9-induced bone formation in the cultured mouse foetal limb explants. In vivo stem cell implantation experiment reveals that exogenous expression of EGF in MSCs can effectively potentiate BMP9-induced ectopic bone formation, yielding larger and more mature bone masses. Interestingly, we find that, while EGF can induce BMP9 expression in MSCs, EGFR expression is directly up-regulated by BMP9 through Smad1/5/8 signalling pathway. Thus, the cross-talk between EGF and BMP9 signalling pathways in MSCs may underline their important roles in regulating osteogenic differentiation. Harnessing the synergy between BMP9 and EGF should be beneficial for enhancing osteogenesis in regenerative medicine.
间充质干细胞（MSCs）是多能祖细胞，可分化为多种谱系，包括骨、软骨和脂肪。表皮生长因子（EGF）刺激细胞生长、增殖和分化。EGF 通过与细胞表面的表皮生长因子受体（EGFR）高亲和力结合并刺激其受体的内在蛋白酪氨酸激酶活性来发挥作用，这会启动信号转导级联反应，导致细胞内发生各种生化变化，并调节细胞增殖和分化。我们已经确定 BMP9 是 MSCs 中最具成骨能力的 BMP 之一。在这项研究中，我们研究了 EGF 信号是否与 BMP9 相互作用并调节 BMP9 诱导的成骨分化。我们发现，EGF 可增强 MSC 中 BMP9 诱导的早期和晚期成骨标志物，这可以通过 EGFR 抑制剂吉非替尼和厄洛替尼或受体酪氨酸激酶抑制剂 AG-1478 和 AG-494 以剂量和时间依赖的方式有效地减弱。此外，EGF 可显著增强培养的小鼠胎肢外植体中 BMP9 诱导的骨形成。体内干细胞植入实验表明，MSCs 中外源表达 EGF 可有效增强 BMP9 诱导的异位骨形成，产生更大、更成熟的骨量。有趣的是，我们发现，虽然 EGF 可以诱导 MSCs 中 BMP9 的表达，但 BMP9 通过 Smad1/5/8 信号通路直接上调 EGFR 的表达。因此，MSCs 中 EGF 和 BMP9 信号通路之间的串扰可能强调了它们在调节成骨分化中的重要作用。利用 BMP9 和 EGF 之间的协同作用应该有益于增强再生医学中的成骨作用。
