LncRNA JPX regulates proliferation and apoptosis of nucleus pulposus cells by targeting the miR-18a-5p/HIF-1α/Hippo-YAP pathway.

With the aggravation of global aging, the rapid rise in the obesity rate, and the increasing number of patients with intervertebral disc degeneration (IDD), the principles and mechanism of this disease remain unclear. This study explored the molecular mechanism of IDD treatment through interactions of the lncRNA-miRNA-mRNA-signaling pathways and the effects on the proliferation and apoptosis of human nucleus pulposus cells (HNPCs) cultured in vitro. Our study revealed that lncRNA JPX is expressed at low levels in HNPCs under normoxic conditions. Luciferase and RNA pull-down assays were used to verify that lncRNA JPX directly bound to miR-18a-5p and influenced HNPC proliferation and apoptosis. Subsequently, a luciferase assay confirmed the direct binding of miR-18a-5p to HIF-1α and demonstrated a negative correlation between miR-18a-5p and HIF-1α. In addition, the HIF-1α antagonist reversed the inhibition of the Hippo-YAP pathway by the miR-18a-5p inhibitor. In conclusion, overexpression of lncRNA JPX upregulated HIF-1α by inhibiting the expression of miR-18a-5p, thereby inhibiting the Hippo-YAP pathway. By inhibiting this pathway, JPX overexpression promoted the proliferation of HNPCs and decreased their apoptosis. Therefore, the lncRNA JPX is a potential new target.

Identification of pathways and genes associated with meniscus degeneration using bioinformatics analyses.

OBJECTIVE: To explore the molecular mechanisms underlying meniscus degeneration. METHODS: We performed anterior cruciate ligament resection in the Hainan Wuzhishan pig to establish a meniscus degeneration model. We applied gene chip technology to detect differentially expressed genes (DEG) in the degenerative meniscus tissues. We applied Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway, core gene network, and relevant MicroRNA analyses to identify regulatory networks relevant to meniscus degeneration. We detected 893 differentially expressed genes, mainly involved in hormone production, apoptosis, and inflammation. RESULTS: We found that MUC13, inflammatory mediator regulation of TRP channels, MDFI, and miR-335-5p may play a key role in the degenerative meniscus tissue. CONCLUSION: We found that meniscus degeneration involves several molecular mechanisms and provide molecular targets for future research into the disease.

Hypoxia-inducible factor-1α regulates PI3K/AKT signaling through microRNA-32-5p/PTEN and affects nucleus pulposus cell proliferation and apoptosis.

Intervertebral disc degeneration and resulting low back pain arises from the programmed apoptosis of nucleus pulposus cells (NPCs). Recent studies show that hypoxia-inducible factor-1α plays a vital role in the etiology and pathogenesis of disc degeneration. However, the underlying mechanism of HIF-1α in NPCs is unclear. The present study identified 994 significant differentially expressed miRNAs by analyzing microarray data downloaded from the Gene Expression Omnibus database. MicroRNA(miR)-32-5p expression was 2.81-fold upregulated in NPCs compared with that of the healthy control tissues (P<0.05). A total of 331 significant differentially expressed mRNAs were identified, and PTEN was downregulated in NPCs of non-degenerative disc tissues from young patients. miR-32-5p was predicted to target the PTEN 3'-untranslated region (UTR). To confirm these results, in-vitro experiments investigating the molecular function of miR-32-5p and PTEN were performed. Furthermore, hypoxia induced miR-32-5p and PTEN expression. HIF-1α inhibited NPC proliferation and promoted cell apoptosis by regulating miR-32-5p and PTEN. miR-32-5p promoted NPC proliferation and decreased cell apoptosis. Next, it was verified whether miR-32-5p targeted the PTEN 3'-UTR using dual-luciferase reporter assays. Finally, it was observed that PI3K/AKT/mTOR signaling pathway was upregulated by a miR-32-5p mimic, which improved cell proliferation and decreased apoptosis. Importantly, PTEN was downregulated in these experiments; and inhibition of miR-32-5p had the opposite effect. Overall, these results demonstrate that HIF-1α regulates cell proliferation and apoptosis by controlling the miR-32-5p/PTEN/PI3K/AKT/mTOR axis in NPCs.

Basic fibroblast growth factor increases IFT88 expression in chondrocytes.

Intraflagellar transport protein 88 (IFT88) is protein crucial for the assembly and maintenance of primary cilia in chondrocytes. Primary cilia regulate mechanical and chemical signals in chondrocytes; however, the effects of cytokines on IFT88 expression and cilia formation and maintenance remain to be elucidated. Therefore, the role of basic fibroblast growth factor (bFGF) on IFT88 expression were examined in theATDC5 murine chondrocytic line, in order to investigate the signaling pathways involved in this process. bFGF treatment upregulated IFT88 expression in a dose­ and time­dependent manner in ATDC5 cells. The effects of bFGF on IFT88 protein expression were suppressed in the presence of the extracellular signal­regulated protein kinase (ERK) inhibitor PD0325901 and the FGF receptor inhibitor BGJ398. In addition, treatment with IFT88­trageting small interfering (si)RNA downregulated the protein expression of IFT88 and ERK, thus suggesting that the ERK signaling pathway may be involved in the regulation of IFT88 expression in ATDC5 cells. bFGF treatment increased the number of ciliated ATDC5 cells and primary cultured chondrocytes. Downregulation of IFT88 expression by PD0325901, BGJ398, or IFT88­targeting siRNA was revealed to reduce the number of ciliated cells. bFGF also upregulated the mRNA and protein expression of IFT88 in primary cultured chondrocytes. In conclusion, the findings of the present study suggested that bFGF may enhance the expression of IFT88, and promote primary cilia development, through the mitogen­activated protein kinase/ERK­mediated pathway in chondrocytes.