LAUSR

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.