LncRNA EPIC1 Protects Human Osteoblasts From Dexamethasone-induced Cell Death

Background and aims.Osteoporosis is a metabolic bone disease characterized by reduced bone mass and deterioration of bone microstructures,which increases the risk of bone fragility and fracture.However,the molecular mechanisms of osteoporosis are largely unclear.The adverse effect of glucocorticoid on bone is mainly due to the direct effect of glucocorticoid on osteoblasts,inhibiting osteoblasts production and increasing the apoptosis of osteoblasts.Long non-coding RNA(LncRNA)has become an important epigenetic regulator for controlling gene expression,affecting various biological processes.Studies have shown that LncRNA is involved in bone remodeling and is closely associated with the occurrence and development of osteoporosis.Dexamethasone(Dex)can induce injury to human osteoblasts.Long non-coding RNA(LncRNA)EP1C1(Lnc-EPIC1)is a novel Myc-interacting LncRNA.Its effect on Dex-treated human osteoblasts is studied here.Methods.In OB-6 human osteoblasts and primary human osteoblasts Lnc-EPICI was overexpressed by using a lentiviral Lnc-EPIC1 vector("LV-EPIC1").Conversely,Lnc-EPIC1 was silenced by targeted siRNAs.After treatment with Dex,Lnc-EPIC1 expression was detected by quantitative real-time polymerase chain reaction(qPCR).Cell viability,death and apoptosis were detected by MTT(3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazole bromide),lactate dehydrogenase(LDH)and histone-DNA enzyme-linked immunosorbent assays(ELISA),respectively.Programmed necrosis was detected by Mito-IP.The expression of Lnc-EPIC1 necrotic femoral head tissues and surrounding normal tissues of Dex-taking patients was detected.Myc was overexpressed by adenovirus vector.Contrarily,Myc was knocked out by CRISPR/Cas-9 gene editing method.Dex-induced osteoblast cell death was detected.Results.In OB·6 osteoblastic cells and primary human osteoblasts,treatment with Dex increased expression of Lnc-EPIC1.Its expression is also elevated in the necrotic femoral head tissues of Dex-taking patients.Ectopic overexpression of Lnc-EPIC1 inhibited Dex-induced apoptosis and programmed necrosis in OB-6 cells and primary human osteoblasts.Reversely,Lnc-EPIC1 silencing by targeted siRNA potentiated Dex-induced eytotoxicity.Myc is the target of in osteoblasts.Exogenous overexpression of Myc protected OB-6 cells from Dex.Conversely,Myc knockout by CRISPR-Cas-9 method abolished Lnc-EPIC1-induced OB-6 cytoprotection against Dex.Conclusion.Lnc-EPIC1 expression protects human osteoblasts from Dex possible via regulation of Myc.