ABSTRACT
Recent evidence indicates that the abnormal differentiation of bone marrow-derived mesenchymal stem cells (BMSCs) plays a pivotal role in the pathogenesis of osteoporosis. LncRNA SNHG1 has been found to be associated with the differentiation ability of BMSCs. In this study, we aimed to elucidate the role of lncRNA SNHG1 and its associated pathway on the differentiation of BMSCs in osteoporosis. Mice that underwent bilateral ovariectomy (OVX) were used as models of osteoporosis. Induced osteogenic or adipogenic differentiation was performed in mouse BMSCs. Compared to sham animals, lncRNA SNHG1 expression was upregulated in OVX mice. Also, the in vitro expression of SNHG1 was increased in adipogenic BMSCs but decreased in osteogenic BMSCs. Moreover, overexpression of SNHG1 enhanced the adipogenic capacity of BMSCs but inhibited their osteogenic capacity as determined by oil red O, alizarin red, and alkaline phosphatase staining, while silencing of SNHG1 led to the opposite results. LncRNA SNHG1 interacting with the RNA-binding polypyrimidine tract-binding protein 1 (PTBP1) promoted osteoprotegerin (Opg) methylation and suppressed Opg expression via mediating DNA methyltransferase (DNMT) 1. Furthermore, Opg was showed to regulate BMSC differentiation. Knockdown of SNHG1 decreased the expressions of adipogenic related genes but increased that of osteogenic related genes. However, the knockdown of Opg partially reversed those effects. In summary, lncRNA SNHG1 upregulated the expression of DNMT1 via interacting with PTBP1, resulting in Opg hypermethylation and decreased Opg expression, which in turn enhanced BMSC adipogenic differentiation and contributed to osteoporosis.
Subject(s)
DNA Methylation , Mesenchymal Stem Cells , Osteoprotegerin , RNA, Long Noncoding , Adipogenesis/genetics , Animals , Cell Differentiation/genetics , Cells, Cultured , DNA (Cytosine-5-)-Methyltransferase 1 , DNA Methylation/genetics , Female , Heterogeneous-Nuclear Ribonucleoproteins/genetics , Mesenchymal Stem Cells/metabolism , Mesenchymal Stem Cells/physiology , Mice , Osteogenesis/genetics , Osteoprotegerin/genetics , Osteoprotegerin/metabolism , Polypyrimidine Tract-Binding Protein , RNA, Long Noncoding/genetics , RNA, Long Noncoding/metabolismABSTRACT
BACKGROUND: We aimed to investigate the functions and underlying mechanism of lncRNA SNHG1 in bone differentiation and angiogenesis in the development of osteoporosis. METHODS: The differential gene or proteins expressions were measured by qPCR or western blot assays, respectively. The targeted relationships among molecular were confirmed through luciferase reporter, RIP and ChIP assays, respectively. Alkaline phosphatase (ALP), alizarin red S (ARS) and TRAP staining were performed to measure the osteoblast/osteoclast differentiation of BMSCs. The viability, migration and angiogenesis in BM-EPCs were validated by CCK-8, clone formation, transwell and tube formation assays, respectively. Western blot and immunofluorescence detected the cytosolic/nuclear localization of ß-catenin. Ovariectomized (OVX) mice were established to confirm the findings in vitro. RESULTS: SNHG1 was enhanced and miR-181c-5p was decreased in serum and femoral tissue from OVX mice. SNHG1 directly inhibited miR-181c-5p to activate Wnt3a/ß-catenin signaling by upregulating SFRP1. In addition, knockdown of SNHG1 promoted the osteogenic differentiation of BMSCs by increasing miR-181c-5p. In contrast, SNHG1 overexpression advanced the osteoclast differentiation of BMSCs and inhibited the angiogenesis of BM-EPCs, whereas these effects were all reversed by miR-181c-5p overexpression. In vivo experiments indicated that SNHG1 silencing alleviated osteoporosis through stimulating osteoblastogenesis and inhibiting osteoclastogenesis by modulating miR-181c-5p. Importantly, SNHG1 could be induced by SP1 in BMSCs. CONCLUSIONS: Collectively, SP1-induced SNHG1 modulated SFRP1/Wnt/ß-catenin signaling pathway via sponging miR-181c-5p, thereby inhibiting osteoblast differentiation and angiogenesis while promoting osteoclast formation. Further, SNHG1 silence might provide a potential treatment for osteoporosis.
Subject(s)
Bone Remodeling/genetics , MicroRNAs , Osteoporosis/genetics , RNA, Long Noncoding , Sp1 Transcription Factor/genetics , Animals , Cell Differentiation , Cells, Cultured , Female , Membrane Proteins/metabolism , Mice, Inbred C57BL , Neovascularization, Physiologic , Signal Transduction , Stem Cells/cytology , Wnt3A Protein/metabolismABSTRACT
Parathyroid hormone is one kind of osteoanabolic agents widely used in clinic for osteoporosis. However, parathyroid hormone needs to be further optimized in the treatment of osteoporosis due to its two way regulatory effect of bone formation with low-dose intermittent treatmentand bone resorption with high-dosecontinuous treatment. Hence, based on the molecular mechanism of parathyroid hormone regulating bone metabolism, we conclude that parathyroid hormone regulates bone metabolism mainly through the following signaling pathways: (1) Gs/cAMP/PKA signaling pathway, whichis the main mechanism of parathyroid hormone regulating bone metabolism to lead to bone formation or bone resorption. (2) Gq/11/PLC/PKC signaling pathway, whose f_6_main function is to inhibit osteogenesis.(3)nonPLC/PKC signaling pathway, which is considered to playosteogenic effect, but whose specific content is not completely clear. (4) ß-arrestin signaling pathway, which can only induceosteogenesis without osteoclastic activation byreceptor desensitization and endocytosis. In this work, we will review the specific contents and functions of the four main signaling pathways activated by parathyroid hormoneto find more optimalosteoanabolic agents. Among them, SOST and Dickkopf-1 monoclonal antibodies are novel targeted drugs. Parathyroid hormone-related peptide that specifically activates the nonPLC/PKC signaling pathway or ß-arrestin signaling pathway is worthy of further development and application.
