Long non-coding RNA TUG1 promotes the osteogenic differentiation of bone marrow mesenchymal stem cells by regulating the AMPK/mTOR/autophagy pathway.

Promoting the differentiation of bone marrow mesenchymal stem cells (BMSCs) into osteoblasts is an effective strategy against osteoporosis. Long non-coding RNAs are closely implicated in BMSC osteogenic differentiation. The present study explored the expression pattern and biological role of taurine upregulated gene 1 (TUG1) in osteogenic differentiation. The expressions of TUG1 and osteogenic markers following the osteogenic induction of BMSCs were detected. The functional relevance of TUG1 was evaluated by performing gain- and loss-of-function tests. Inhibitors of AMP-activated protein kinase (AMPK) autophagy were applied to ascertain the effects of TUG1 on the osteogenic differentiation of BMSCs. TUG1 expression increased during the osteogenic differentiation of BMSCs. The overexpression of TUG1 was promoted, whereas the knockdown of TUG1 was suppressed, by BMSC osteogenic differentiation. Mechanically, TUG1 promoted the osteogenesis of BMSCs via the AMPK-mammalian target of rapamycin (mTOR)-autophagy signaling pathway. Blocking AMPK and autophagy could abrogate the osteogenic role of TUG1 in BMSCs. These results demonstrated that TUG1 promoted the osteogenic differentiation of BMSCs by regulating the AMPK/mTOR/autophagy axis, suggesting that targeting TUG1 may be a potential therapy for osteoporosis.

Upregulation of microRNA-320 decreases the risk of developing steroid-induced avascular necrosis of femoral head by inhibiting CYP1A2 both in vivo and in vitro.

Steroid-induced avascular necrosis of femoral head (SANFH) occurs frequently in patients receiving high-dose steroid treatment for these underlying diseases. The target of this study is to investigate the effect of microRNA-320 (miR-320) on SANFH by targeting CYP1A2. CYP1A2 expression was detected using immunohistochemistry. Specimens were collected from patients with SANFH and femoral neck fracture. Seventy rats were assigned into seven groups. The targeting relationship between miR-320 and CYP1A2 was verified by bioinformatics website and dual luciferase reporter gene assay. RT-qPCR and Western blot analysis were used to detect miR-320 and CYP1A2 expressions. The enzymatic activity of CYP1A2 was detected by fluorescence spectrophotometry. Hemorheology and microcirculation were measured in rats. MiR-320 expression decreased and CYP1A2 expression and enzymatic activity increased in SANFH patients compared to those with femoral neck fracture. CYP1A2 was the target gene of miR-320. Hemorheology and microcirculation results showed that up-regulated expression of CYP1A2 promoted the development of SANFH while increased expression of miR-320 inhibited the development of SANFH. Compared with the SANFH group, the SANFH + miR-320 mimic group showed increased miRNA-320 expression, and decreased CYP1A2 expression and enzymatic activity. Opposite results were found in the SANFH + miR-320 inhibitor group. The SANFH + miR-320 inhibitor + pCR-CYP1A2_KO group showed decreased miRNA-320 expression and the SANFH + pCR-CYP1A2_KO group showed decreased CYP1A2 expression and enzymatic activity. Our findings provide evidences that miR-320 might inhibit the development of SANFH by targeting CYP1A2.