Division of Endocrinology and Centre for Research in Anabolic Skeletal Targets in Health and Illness (ASTHI), CSIR-Central Drug Research Institute, Lucknow, Uttar Pradesh, India.
J Cell Biochem. 2018 Apr;119(4):3293-3303. doi: 10.1002/jcb.26490. Epub 2017 Dec 26.
Wnt signaling pathway plays important role in all aspects of skeletal development which include chondrogenesis, osteoblastogenesis, and osteoclastogenesis. Induction of the Wnt-3 signaling pathway promotes bone formation while inactivation of the pathway leads to bone related disorders like osteoporosis. Wnt signaling thus has become a desired target to treat osteogenic disorders. MicroRNAs (miRNAs) represent an important category of elements that interact with Wnt signaling molecules to regulate osteogenesis. Here, we show that miR-376c, a well-characterized tumor suppressor which inhibits cell proliferation and invasion in osteosarcoma by targeting to transforming growth factor-alpha, suppresses osteoblast proliferation, and differentiation. Over-expression of miR-376c inhibited osteoblast differentiation, whereas inhibition of miR-376c function by antimiR-376c promoted expression of osteoblast-specific genes, alkaline phosphatase (ALP) activity, and matrix mineralization. Target prediction analysis tools and experimental validation by luciferase 3' UTR reporter assay along with qRT-PCR identified Wnt-3 and ARF-GEF-1 as direct targets of miR-376c. It was seen that over-expression of miR-376c leads to repression of canonical Wnt/β-catenin signaling. Our overall results suggest that miR-376c targets Wnt-3 and ARF-GEF-1 suppresses ARF-6 activation which prevents the release of β-catenin and its transactivation thereby inhibiting osteoblast differentiation. Although miR-376c is known to be a tumor repressor; we have identified a second complementary function of miR-376c where it inhibits Wnt-3-mediated osteogenesis and promotes bone loss.
Wnt 信号通路在骨骼发育的各个方面都起着重要作用，包括软骨生成、成骨细胞生成和破骨细胞生成。诱导 Wnt-3 信号通路可促进骨形成，而抑制该通路则会导致骨质疏松等骨骼相关疾病。因此，Wnt 信号已成为治疗成骨障碍的理想靶点。microRNAs（miRNAs）是一类重要的调节因子，可与 Wnt 信号分子相互作用，调节成骨作用。在这里，我们发现 miR-376c 是一种经过充分研究的肿瘤抑制因子，通过靶向转化生长因子-α（transforming growth factor-alpha）抑制骨肉瘤细胞的增殖和侵袭，抑制成骨细胞的增殖和分化。miR-376c 的过表达抑制成骨细胞分化，而通过抗 miR-376c 抑制 miR-376c 的功能则促进成骨细胞特异性基因、碱性磷酸酶（alkaline phosphatase，ALP）活性和基质矿化的表达。靶预测分析工具和通过荧光素酶 3'UTR 报告实验和 qRT-PCR 进行的实验验证表明，Wnt-3 和 ARF-GEF-1 是 miR-376c 的直接靶标。结果表明，miR-376c 的过表达导致经典 Wnt/β-catenin 信号的抑制。我们的总体结果表明，miR-376c 靶向 Wnt-3 和 ARF-GEF-1，抑制 ARF-6 激活，从而阻止 β-catenin 的释放及其反式激活，从而抑制成骨细胞分化。尽管 miR-376c 是众所周知的肿瘤抑制因子；但我们已经确定了 miR-376c 的第二个互补功能，它抑制 Wnt-3 介导的成骨作用并促进骨质流失。
