Int J Biol Sci 2019; 15(10):2182-2197. doi:10.7150/ijbs.33490
Let-7f-5p regulates TGFBR1 in glucocorticoid-inhibited osteoblast differentiation and ameliorates glucocorticoid-induced bone loss
1. Guangzhou University of Chinese Medicine, Guangzhou 510405, China;
2. Department of Spinal Surgery, The First Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510405, China;
3. Lingnan Medical Research Center of Guangzhou University of Chinese Medicine, Guangzhou 510405, China;
# These authors contributed equally to this work.
Shen GY, Ren H, Shang Q, Zhao WH, Zhang ZD, Yu X, Huang JJ, Tang JJ, Yang ZD, Liang D, Jiang XB. Let-7f-5p regulates TGFBR1 in glucocorticoid-inhibited osteoblast differentiation and ameliorates glucocorticoid-induced bone loss. Int J Biol Sci 2019; 15(10):2182-2197. doi:10.7150/ijbs.33490. Available from http://www.ijbs.com/v15p2182.htm
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 in vitro and in GIOP in vivo. 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 (Runx2,Osx, Alp, and Ocn), 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 in vivo, agomiR-let-7f-5p significantly reversed bone loss induced by Dex, as well as increased osteogenic marker expression (Runx2, Osx, Alp, and Ocn) 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.
Keywords: Let-7f-5p, osteoblast differentiation, bone formation, glucocorticoid-induced bone loss, TGFBR1, GR