LncRNA SNHG1 modulates p38 MAPK pathway through Nedd4 and thus inhibits osteogenic differentiation of bone marrow mesenchymal stem cells

Current study aimed to investigate the effects of lncRNA SNHG1 on osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) and explore the underlying mechanisms.Mouse model of osteoporosis was created by ovariectomy (OVX). The BMD of mice spine, the serum level of β-CTX and the ALP activity were measured. The expression of SNHG1, JNK, p-JNK, p-38, p-p38 and Osterix were examined by qRT-PCR and Western blot. Co-IP assay was used to verify the effect of SNHG1 on the interaction between p-p38 and Nedd4. Ubiquitination assay was used to evaluate the roles of SNHG1 in ubiquitination of p-p38.In the mice with osteoporosis, BMD was decreased and β-CTX concentration and SNHG1 expression were increased. ALP activity and p-p38 protein level were elevated and SNHG1 expression was down-regulated in BMSCs stimulated by osteogenic inducer, while the effects were reversed by SNHG1 over-expression. SNHG1 over-expression enhanced the interaction between Nedd4 and p-p38, disrupted protein stability of p-p38, and promoted the ubiquitination of p-p38. In addition, pcDNA-SNHG1 down-regulated p-p38 protein level, and sh-Nedd4 removed the trend. Nedd4 silencing elevated ALP activity and Osterix protein level, while p-38 inhibitor abrogated the effects. In vivo, SNHG1 silence increased BMD and Osterix protein level, and decreased endogenous SNHG1 expression in mice with OVX.This study proved the regulation mechanism that lncRNA SNHG1 negatively regulates p38 MAPK signal pathway through ubiquitination mediated by Nedd4, and thus inhibits osteogenic differentiation of BMSCs.