There is now increasing evidence which suggests a key role for osteoblast apoptosis in the pathogenesis of postmenopausal osteoporosis. Here, we evaluated the role and mechanism of proteasome 26S subunit, ATPase (PSMC) 6, a protein that is highly expressed in bone. Gene expression pattern had been extracted based on database of Gene Expression Omnibus (GEO). GEO2R was employed for analyses, while the DAVID database was adopted to further analyze the gene ontology (GO) as well as Kyoto Encyclopedia of Genomes pathway (KEGG) enrichment. Then, the Search Tool Retrieval of Interacting Genes (STRING) was utilized to carry out interaction regulatory network for the top 200 differentially expressed genes (DEGs). A key gene, called PSMC6, was identified by Cytoscape 3.6.0. The OVX osteoporosis model was established in female C57BL/6 mice by full bilateral ovariectomy. According to our findings, PSMC6 gene knockout would elevate bone mineral density (BMD) and the phosphorylation level of PI3K protein and increased the protein level of cleaved caspase‐3/‐9 in OVX osteoporosis mice. Further, MTT, bromodeoxyuridine, and flow cytometry assays revealed that PSMC6 inhibition promoted the progression of cell cycle and cell proliferation, whereas, PSMC6 overexpression promoted the apoptosis and inhibited cell cycle progression and cell proliferation in vitro. Besides, we found that PI3K activation significantly decreased PSMC6‐induced osteoblast apoptosis and promoted cell proliferation through regulating the protein levels of p53, cyclinD1, and cleaved caspase‐3/9. In conclusion, PSMC6 aggravated the degree of OVX‐induced osteoporosis by inhibiting the PI3K/AKT signal transduction pathway, thereby promoting the apoptosis of osteoblasts.
Mesenchymal stem cells (MSCs) are previously found to have potential capacity to differentiate into osteocytes when exposed to specific stimuli. However, the detailed molecular mechanism during this progress remains largely unknown. In the current study, we characterized the lncRNA NKILA as a crucial positive regulator for osteogenesis of MSCs. NKILA attenuation significantly inhibits the calcium deposition and alkaline phosphatase activity of MSCs. More interestingly, we defined that NKILA is functionally involved in the regulation of RXFP1/PI3K‐AKT and NF‐κB signalling. Knockdown of NKILA dramatically down‐regulates the expression of RXFP1 and then reduces the activity of AKT, a downstream regulator of RXFP1 signalling which is widely accepted as an activator of osteogenesis. Moreover, we identify NF‐κB as another critical regulator implicated in NKILA‐mediated osteogenic differentiation. Inhibition of NF‐κB can induce the expression of RUNX2, a master transcription factor of osteogenesis, in a HDAC2‐mediated deacetylation manner. Thus, this study illustrates the regulatory function of NKILA in osteogenesis through distinct signalling pathways, therefore providing a new insight into searching for new molecular targets for bone tissue repair and regeneration.
Enzymatic decomposition of extracellular matrix and possibly local inflammation may cause intervertebral disc degeneration (IDD). MicroRNAs have been reported to correlate with the development of IDD. In this experiment, we aim at finding out the role of miR-181a in the inflammation of IDD and the underlying mechanism. The targeting relationship between miR-181a and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) was verified. Following the establishment of IDD mouse models, disc height index (DHI) and the change of DHI (%DHI) were measured.The functional role of miR-181a in IDD was determined using ectopic expression and depletion and reporter assay experiments. Expression of miR-181a, TRAIL, extracellular signal-regulated kinase (ERK) pathway-related genes and inflammatory factors was evaluated. Also, the expression of collagen I and collagen II was observed. miR-181a directly targeted TRAIL. IDD mice exhibited significant degeneration of the intervertebral disc. miR-181a was downregulated while TRAIL was upregulated in mice with IDD. miR-181a upregulation and the ERK pathway inhibition could reduce expression of TRAIL, ERK pathway-related genes, inflammatory factors, and collagen I, but promote collagen II expression. Our results reveal that upregulation of miR-181a protects against inflammatory response by inactivating the ERK pathway via suppression of TRAIL in IDD mice. These results point to miR-181a as a potential therapeutic target for the clinical management of IDD.
K E Y W O R D SERK pathway, inflammation, intervertebral disc degeneration, microRNA-181a, TRAIL
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