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

Aims: 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. Main methods: Mouse model of osteoporosis was created by ovariectomy (OVX). The BMD of mice spine, the serum level of beta-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. Key findings: In the mice with osteoporosis, BMD was decreased and beta-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. Significance: 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.