Guangzhou University of Chinese Medicine, Guangzhou 510405, China.
Department of Spinal Surgery, The First Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510405, China.
Int J Biol Sci. 2019 Aug 19;15(10):2182-2197. doi: 10.7150/ijbs.33490. eCollection 2019.
Previous studies indicated that let-7 enhances osteogenesis and bone formation of human adipose-derived mesenchymal stem cells (MSCs). We also have confirmed that let-7f-5p expression was upregulated during osteoblast differentiation in rat bone marrow-derived MSCs (BMSCs) and was downregulated in the vertebrae of patients with glucocorticoid (GC)-induced osteoporosis (GIOP). The study was performed to determine the role of let-7f-5p in GC-inhibited osteogenic differentiation of murine BMSCs and in GIOP . Here, we report that dexamethasone (Dex) inhibited osteogenic differentiation of BMSCs and let-7f-5p expression, while increasing the expression of transforming growth factor beta receptor 1 (TGFBR1), a direct target of let-7f-5p during osteoblast differentiation under Dex conditions. In addition, let-7f-5p promoted osteogenic differentiation of BMSCs, as indicated by the promotion of alkaline phosphatase (ALP) staining and activity, Von Kossa staining, and osteogenic marker expression (,, , and ), but decreased TGFBR1 expression in the presence of Dex. However, overexpression of TGFBR1 reversed the upregulation of let-7f-5p during Dex-treated osteoblast differentiation. Knockdown of TGFBR1 reversed the effect of let-7f-5p downregulation during Dex-treated osteogenic differentiation of BMSCs. We also found that glucocorticoid receptor (GR) mediated transcriptional silencing of let-7f-5p and its knockdown enhanced Dex-inhibited osteogenic differentiation. Further, when injected , agomiR-let-7f-5p significantly reversed bone loss induced by Dex, as well as increased osteogenic marker expression (, , , and ) and decreased TGFBR1 expression in bone extracts. These findings indicated that the regulatory axis of GR/let-7f-5p/TGFBR1 may be important for Dex-inhibited osteoblast differentiation and that let-7f-5p may be a useful therapeutic target for GIOP.
先前的研究表明，let-7 可增强人脂肪间充质干细胞（MSCs）的成骨和骨形成。我们还证实，在大鼠骨髓来源的 MSCs（BMSCs）成骨分化过程中，let-7f-5p 的表达上调，而在糖皮质激素（GC）诱导的骨质疏松症（GIOP）患者的椎骨中下调。该研究旨在确定 let-7f-5p 在 GC 抑制鼠 BMSCs 成骨分化中的作用，以及在 GIOP 中的作用。在这里，我们报告地塞米松（Dex）抑制 BMSCs 的成骨分化和 let-7f-5p 的表达，同时在 Dex 条件下增加转化生长因子β受体 1（TGFBR1）的表达，TGFBR1 是 let-7f-5p 在成骨分化过程中的直接靶标。此外，let-7f-5p 促进 BMSCs 的成骨分化，表现为碱性磷酸酶（ALP）染色和活性、Von Kossa 染色以及成骨标志物表达（、、、和）的增加，但 Dex 存在时 TGFBR1 表达减少。然而，TGFBR1 的过表达逆转了 Dex 处理成骨分化过程中 let-7f-5p 的上调。TGFBR1 的敲低逆转了 Dex 处理 BMSCs 成骨分化过程中 let-7f-5p 下调的作用。我们还发现，糖皮质激素受体（GR）介导 let-7f-5p 的转录沉默，其敲低增强了 Dex 抑制的成骨分化。此外，当注射时，agomiR-let-7f-5p 显著逆转了 Dex 诱导的骨丢失，同时增加了骨提取物中成骨标志物的表达（、、、和）并降低了 TGFBR1 的表达。这些发现表明，GR/let-7f-5p/TGFBR1 调节轴对于 Dex 抑制的成骨分化可能很重要，并且 let-7f-5p 可能是治疗 GIOP 的有用治疗靶点。
