LncRNA LINC00311 Promotes the Proliferation and Differentiation of Osteoclasts in Osteoporotic Rats Through the Notch Signaling Pathway by Targeting DLL3

Background/Aims: Osteoporosis is a commonly occurring condition marked by a loss of bone density. Previous evidence has highlighted the roles played by microRNAs as potential treatment tools for the disease. At present, the influence of long non-coding RNAs (lncRNAs) on the progression of osteoporosis remains largely unclear. Thus, an investigation was conducted into the target relationship between LINC00311, which has been reported to be highly expressed in osteoporosis, and delta-like 3 (DLL3), which is involved in the Notch signaling pathway, in connection with a series of bioinformatic methods. An osteoporotic rat model was established by means of ovariectomy (OVX) to evaluate the influence exerted by DLL3-binding LINC00311 on osteoclasts through the Notch signaling pathway. Methods: Osteoclasts were extracted from osteoporotic rats and transfected with the LINC00311-vector, shRNA-LINC00311, Notch activator, or a combination of the Notch activator and LINC00311-vector. Western blotting and RT-qPCR techniques were applied to determine the expression levels of LINC00311, DLL3, Notch1, Notch2, Jagged1, Hes-1 and TRAP in tissues and cells, while cell activity was detected by MTT assay. The cell cycle as well as the rate of apoptosis was detected by flow cytometry. The successfully established osteoporotic rats were designated into the OVX-siRNA, OVX-LINC00311 and OVX-control groups to observe the effects of LINC00311 on the proliferation and differentiation of osteoclasts. Results: Cells transfected with the LINC00311-vector exhibited increased expression levels of Notch2 and TRPA as well as increased cell activity, while decreased expression levels of DLL3, Notch1, Jagged1 and Hes-1, along with a decreased cell apoptosis rate, were observed. The opposite tendencies of these parameters were observed in the cells treated with shRNA-LINC00311. A key observation was made when the Notch signaling pathway was activated, in that the cell activity was decreased while the rate of apoptosis increased. In comparison with the OVX-control group, the expression levels of LINC00311, Notch2 and TRAP as well as the positive expression rate of TRAP all exhibited reductions, while those of DLL3, Jagged1 and Notch1 were elevated in the OVX-siRNA group. Compared with those in the sham group, in the OVX-control and OVX-LINC00311 groups, LINC00311 and the expression levels of Notch2 and TRAP were increased; however, decreased levels of DLL3, Jagged1 and Notch1 were noted. Conclusions: Taken together, the key findings of the present study suggest that LINC00311 induces proliferation and inhibits apoptosis of osteoclasts via the regulation of the Notch signaling pathway by inhibiting DLL3 expression, ultimately demonstrating that LINC00311 and its target gene DLL3 may serve as independent factors in cases of osteoporosis