Department of Orthopedics, Jinling Hospital, Jinling Clinical Medical College of Nanjing Medical University, Nanjing, 210002, Jiangsu, People's Republic of China.
Department of Orthopedics, Affiliated Hospital 2 of Nantong University, Nantong, 226001, Jiangsu, People's Republic of China.
Mol Cell Biochem. 2019 Oct;460(1-2):113-121. doi: 10.1007/s11010-019-03575-y. Epub 2019 Jul 16.
Sustained dexamethasone (Dex) treatment could induce secondary osteoporosis, osteonecrosis, or even bone fractures. Dex can induce potent cytotoxicity in cultured human osteoblasts. The aim of this study was to test the potential role of microRNA-7 (miR-7), which targets the epidermal growth factor receptor (EGFR), in Dex-treated human osteoblasts. In OB-6, hFOB1.19, and primary human osteoblasts, miR-7 depletion by a lentiviral antagomiR-7 construct (LV-antagomiR-7) increased EGFR expression and downstream Akt activation, protecting cells from Dex-induced viability reduction, cell death, and apoptosis. In contrast, forced overexpression of miR-7 by a lentiviral miR-7 construct (LV-miR-7) inhibited EGFR expression and Akt activation, potentiating Dex-induced cytotoxicity in OB-6, hFOB1.19, and primary human osteoblasts. EGFR is the primary target of miR-7 in human osteoblasts. Luciferase activity of the EGFR 3-untranslated region was enhanced by LV-antagomiR-7, but decreased by LV-miR-7 in OB-6 cells. Further, LV-antagomiR-7-induced osteoblast cytoprotection against Dex was abolished by the EGFR inhibitors AG1478 and PD153035. Moreover, neither LV-antagomiR-7 nor LV-miR-7 was functional in EGFR-KO OB-6 cells. We also show that miR-7 is upregulated in the necrotic femoral head tissues of Dex-administered patients, correlating with EGFR downregulation. Together, we conclude that miR-7 inhibition protects human osteoblasts from Dex via activation of EGFR signaling.
地塞米松（Dex）的持续治疗可能会导致继发性骨质疏松症、骨坏死，甚至骨折。地塞米松可在培养的人成骨细胞中诱导出强烈的细胞毒性。本研究旨在检测靶向表皮生长因子受体（EGFR）的 microRNA-7（miR-7）在 Dex 处理的人成骨细胞中的潜在作用。在 OB-6、hFOB1.19 和原代人成骨细胞中，通过慢病毒反义 miR-7 构建体（LV-antagomiR-7）耗竭 miR-7 会增加 EGFR 表达和下游 Akt 激活，从而保护细胞免受 Dex 诱导的活力降低、细胞死亡和凋亡。相比之下，通过慢病毒 miR-7 构建体（LV-miR-7）强制过表达 miR-7 会抑制 EGFR 表达和 Akt 激活，从而增强 Dex 在 OB-6、hFOB1.19 和原代人成骨细胞中的细胞毒性。EGFR 是人成骨细胞中 miR-7 的主要靶标。在 OB-6 细胞中，EGFR 3'-UTR 的荧光素酶活性被 LV-antagomiR-7 增强，而被 LV-miR-7 降低。此外，EGFR 抑制剂 AG1478 和 PD153035 可消除 LV-antagomiR-7 诱导的 Dex 对成骨细胞的保护作用。此外，EGFR-KO OB-6 细胞中既没有 LV-antagomiR-7 也没有 LV-miR-7 发挥功能。我们还表明，miR-7 在 Dex 给药患者的坏死股骨头组织中上调，与 EGFR 下调相关。总之，我们的结论是，miR-7 通过激活 EGFR 信号通路来保护人成骨细胞免受 Dex 的侵害。
