The role of miRNA, lncRNA and circRNA in the development of intervertebral disk degeneration (Review)

Inhibiting DNA methyltransferase DNMT3B confers protection against ferroptosis in nucleus pulposus and ameliorates intervertebral disc degeneration via upregulating SLC40A1

Epigenetic changes are important considerations for degenerative diseases. DNA methylation regulates crucial genes by epigenetic mechanism, impacting cell function and fate. DNA presents hypermethylation in degenerated nucleus pulposus (NP) tissue, but its role in intervertebral disc degeneration (IVDD) remains elusive. This study aimed to demonstrate that methyltransferase mediated hypermethylation was responsible for IVDD by integrative bioinformatics and experimental verification. Methyltransferase DNMT3B was highly expressed in severely degenerated NP tissue (involving human and rats) and in-vitro degenerated human NP cells (NPCs). Bioinformatics elucidated that hypermethylated genes were enriched in oxidative stress and ferroptosis, and the ferroptosis suppressor gene SLC40A1 was identified with lower expression and higher methylation in severely degenerated human NP tissue. Cell culture using human NPCs showed that DNMT3B induced ferroptosis and oxidative stress in NPCs by downregulating SLC40A1, promoting a degenerative cell phenotype. An in-vivo rat IVDD model showed that DNA methyltransferase inhibitor 5-AZA alleviated puncture-induced IVDD. Taken together, DNA methyltransferase DNMT3B aggravates ferroptosis and oxidative stress in NPCs via regulating SLC40A1. Epigenetic mechanism within DNA methylation is a promising therapeutic biomarker for IVDD.

Noncoding RNAs in skeletal development and disorders

Protein-encoding genes only constitute less than 2% of total human genomic sequences, and 98% of genetic information was previously referred to as "junk DNA". Meanwhile, non-coding RNAs (ncRNAs) consist of approximately 60% of the transcriptional output of human cells. Thousands of ncRNAs have been identified in recent decades, and their essential roles in the regulation of gene expression in diverse cellular pathways associated with fundamental cell processes, including proliferation, differentiation, apoptosis, and metabolism, have been extensively investigated. Furthermore, the gene regulation networks they form modulate gene expression in normal development and under pathological conditions. In this review, we integrate current information about the classification, biogenesis, and function of ncRNAs and how these ncRNAs support skeletal development through their regulation of critical genes and signaling pathways in vivo. We also summarize the updated knowledge of ncRNAs involved in common skeletal diseases and disorders, including but not limited to osteoporosis, osteoarthritis, rheumatoid arthritis, scoliosis, and intervertebral disc degeneration, by highlighting their roles established from in vivo, in vitro, and ex vivo studies.

Construction of a novel mRNA-miRNA-lncRNA/circRNA triple subnetwork associated with immunity and aging in intervertebral disc degeneration

OBJECTIVE

Intervertebral disk degeneration (IVDD) is one of the most common causes of low back pain. However, in the etiology of IVDD, the specific method by which nucleus pulposus (NP) cell senescence and the immune response induce disease is uncertain.

METHODS

Gene Expression Omnibus database was used to find differentially expressed genes (DEGs), differentially expressed miRNAs (DE miRNAs), differentially expressed lncRNAs (DE lncRNAs), and differentially expressed circRNAs (DE circRNAs). Functional enrichment analysis was performed through Enrichr database. Potential regulatory miRNAs, lncRNAs and circRNAs of mRNAs were predicted by ENCORI and circBank, respectively.

RESULTS

We identified 198 upregulated and 131 downregulated genes, 39 upregulated and 22 downregulated miRNAs, 2152 upregulated and 564 downregulated lncRNAs, and 352 upregulated and 279 downregulated circRNAs as DEGs, DE miRNAs, DE lncRNAs, DE circRNAs, respectively. Functional enrichment analysis revealed that they were significantly enriched in Toll-like receptor signaling route and the NF-kappa B signaling pathway. An mRNA-miRNA-lncRNA/circRNA network linked to the pathogenesis of NP cells in IVDD was constructed based on node degree and differential expression level. Eight immune-related DEGs (6 upregulated and 2 downregulated genes) and five aging-related DEGs (3 upregulated and 2 downregulated genes) were identified in the critical network.

CONCLUSION

We established a novel immune-related and aging-related triple regulatory network of mRNA-miRNA-lncRNA/circRNA ceRNA, among which all RNAs may be utilized as the pathogenesis biomarker of NP cells in IVDD.

Ginsenoside Rg1 relieves rat intervertebral disc degeneration and inhibits IL-1β-induced nucleus pulposus cell apoptosis and inflammation via NF-κB signaling pathway

The study aimed to investigate the effect of ginsenoside Rg1 on intervertebral disc degeneration (IVDD) in rats and IL-1β-induced nucleus pulposus (NP) cells, and explore its underlying mechanism. Forty IVDD rat models were divided into the IVDD group, low-dose (L-Rg1) group (intraperitoneal injection of 20 mg/kg/d ginsenoside Rg1), medium-dose (M-Rg1) group (intraperitoneal injection of 40 mg/kg/d ginsenoside Rg1), and high-dose (H-Rg1) group (intraperitoneal injection of 80 mg/kg/d ginsenoside Rg1). The pathological change was observed by HE and safranin O-fast green staining. The expression of IL-1β, IL-6, TNF-α, MMP3, aggrecan, and collagen II was detected. The expression of NF-κB p65 in IVD tissues was detected. Rat NP cells were induced by IL-1β to simulate IVDD environment and divided into the control group, IL-1β group, and 20, 50, and 100 µmol/L Rg1 groups. The cell proliferation activity, the apoptosis, and the expression of IL-6, TNF-α, MMP3, aggrecan, collagen II, and NF-κB pathway-related protein were detected. In IVDD rats, ginsenoside Rg1 improved the pathology of IVD tissues; suppressed the expression of IL-1β, IL-6, TNF-α, aggrecan, and collagen II; and inhibited the expression of p-p65/p65 and nuclear translocation of p65, to alleviate the IVDD progression. In the IL-1β-induced NP cells, ginsenoside Rg1 also improved the cell proliferation and inhibited the apoptosis and the expression of IL-6, TNF-α, aggrecan, collagen II, p-p65/p65, and IκK in a dose-dependent manner. Ginsenoside Rg1 alleviated IVDD in rats and inhibited apoptosis, inflammatory response, and ECM degradation in IL-1β-induced NP cells. And Rg1 may exert its effect via inhibiting the activation of NF-κB signaling pathway.

Circ_LRP6 facilitates osteosarcoma progression via the miR-122-5p/miR-204-5p/HMGB1 axis

Circ_LRP6 is participated in the occurrence and development of numerous tumors. Nevertheless, its roles and mechanism in osteosarcoma (OS) is unknown. This study aims to illustrate this point. With the use of qRT-PCR, the level of circ_LRP6, miR-122-5p, miR-204-5p and HMGB1 was identified. To observe cell proliferation, migration and invasion, we adopted CCK-8 and Transwell assays in the present study. Besides, to prove the existing interaction, bioinformatics analysis and dual luciferase reporting assays were employed. The influence of circ_LRP6 on osteosarcoma in vivo was evaluated by subcutaneous tumor formation model in nude mice. In osteosarcoma tissues, circ_LRP6 and HMGB1 are strongly denoted, whereas miR-122-5p and miR-204-5p are under-expressed. Circ_LRP6 knockdown could significantly hinder the proliferation, migration and invasion of osteosarcoma cells. Circ_LRP6 hindered the proliferation of osteosarcoma in vivo. Bioinformatics predicted that miR-122-5p and miR-204-5p functioned as direct targets of circ_LRP6, and HMGB1 were possible target genes of miR-122-5p and miR-204-5p. The findings indicated that the low level of miR-122-5p and miR-204-5p and the overexpression of HMGB1 could partially restore and reduce the inhibitory impact of circ_LRP6 on the proliferation, migration and invasion of osteosarcoma cells. Circ_LRP6 affects osteosarcoma progression via the miR-122-5p/miR-204-5p/HMGB1 axis, and is shown to be a molecular biomarker.

HSA-MIR-183-3P TARGETING ATAXIA-TELANGIECTASIA MUTATED PROTEIN REGULATION OF NF-ΚB SIGNALING PATHWAY AFFECTS CELLULAR SENESCENCE CAUSED BY DNA DAMAGE IN LUMBAR DISC DEGENERATION

Aims

To test the effect of Hsa-miR-183-3p on cell aging and disc degeneration in lumbar intervertebral disc.

Methods

This study combined clinical research with basic cell experiment, analyzing clinical data from patients with lumbar disc degeneration and traumatic lumbar spine fracture, as well as the differences in baseline data. The degree of lumbar disc injury in patients of different ages was also compared. Differentially expressed miRNAs were predicted via GEO database, and qPCR confirmation was determined by collecting cartilage endplates from two groups. ACAN, Col2A1, p16, p21, and p53 were detected by immunofluorescence, Western blot and qPCR in human nucleus pulposus cells. Changes of cell senescence were detected. The binding of Hsa-miR-183-3p to ataxia-telangiectasia mutated protein was confirmed by dual luciferase reporter assay.

Results

Degenerative discs showed elevated expression of hsa-miR-183-3p, which may be upregulated by TNF-α via NF-κB signaling pathway and target ataxia-telangiectasia mutated protein regulation.

Conclusion

Degeneration of the intervertebral disc can be accelerated by TNF-α. Additionally, Hsa-miR-183-3p passed NF-κB signaling pathway is blocked via up-regulation of TNF-α to reduce inflammation via targeting ataxia-telangiectasia mutated protein. As a result, this negative feedback mechanism may assist in maintaining a low degenerative load and preserving chronic disc degeneration.

Emerging role and therapeutic implication of mTOR signalling in intervertebral disc degeneration

Intervertebral disc degeneration (IDD), an important cause of chronic low back pain (LBP), is considered the pathological basis for various spinal degenerative diseases. A series of factors, including inflammatory response, oxidative stress, autophagy, abnormal mechanical stress, nutritional deficiency, and genetics, lead to reduced extracellular matrix (ECM) synthesis by intervertebral disc (IVD) cells and accelerate IDD progression. Mammalian target of rapamycin (mTOR) is an evolutionarily conserved serine/threonine kinase that plays a vital role in diverse degenerative diseases. Recent studies have shown that mTOR signalling is involved in the regulation of autophagy, oxidative stress, inflammatory responses, ECM homeostasis, cellular senescence, and apoptosis in IVD cells. Accordingly, we reviewed the mechanism of mTOR signalling in the pathogenesis of IDD to provide innovative ideas for future research and IDD treatment.

Downregulation of miR-760 Causes Human Intervertebral Disc Degeneration by Targeting the MyD88/Nuclear Factor-Kappa B Signaling Pathway

Dysregulation of microRNAs (miRNAs) plays a critical role in the development of intervertebral disc degeneration (IDD). In this study, we present evidence from in vitro and in vivo research to elucidate the mechanism underlying the role of miR-760 in IDD. miRNA microarray and quantitative reverse transcription-polymerase chain reaction were used to determine the miRNA profiles in patients with IDD. Functional analysis was performed to evaluate the role of miR-760 in the pathogenesis of IDD. Luciferase reporter and western blotting assays were used to confirm the miRNA targets. The expression of miR-760 was significantly decreased in degenerative nucleus pulposus (NP) cells and negatively correlated with disc degeneration grade. Functional assays demonstrated that miR-760 delivery significantly increased NP cell proliferation and promoted the expression of collagen II and aggrecan. Moreover, MyD88 was identified as a target gene of miR-760. miR-760 effectively suppressed MyD88 expression by interacting with the 3′-untranslated region, which was abolished by miR-760 binding site mutations. An in vivo experiment using an IDD mouse model showed that the upregulation of miR-760 could effectively suspend IDD. Therefore, miR-760 was found to play an important role in IDD and can be used as a promising therapeutic target for the treatment of patients with IDD.

Can Manganese Dioxide Microspheres be Used as Intermediaries to Alleviate Intervertebral Disc Degeneration With Strengthening Drugs?

Degenerative disc disease (DDD) is a pathological condition associated with intervertebral discs (IVDs) that causes chronic back pain. IVD degeneration has become a significant issue in contemporary society. To date, numerous biological therapies have been applied to alleviate the progression of DDD, among which therapeutic protein injection is the most direct and convenient. However, there are some limitations to applying direct protein injection therapy, the most significant being that the efficacy of this method has a short duration, which is a major factor in its effectiveness and the resulting patient satisfaction. How do we solve this problem? Or how can the effectiveness of the treatment be enhanced? It has been proved that manganese dioxide (MnO₂) microspheres, widely used in environmental science, not only regulate the expression of cell genes and cytokines in the microenvironment, but also have the ability to release drugs slowly. We propose that direct injection of protein encapsulated in hollow MnO₂ (h-MnO₂) microspheres could solve the problem of rapid drug release. In addition, the use of a MnO₂ and protein injection in the treatment of DDD may have a synergistic effect, which would be highly significant for the degradation of pro-inflammatory factors in the DDD microenvironment. Therefore, the combination of MnO₂ and protein may provide a new therapeutic approach to alleviate the progression of DDD.

Oxidative Stress in Intervertebral Disc Degeneration: New Insights from Bioinformatic Strategies

Oxidative stress has been proved to play important roles in the development of intervertebral disc degeneration (IDD); however, the underlying mechanism remains obscure to date. The aim of this study was to elucidate the vital roles of oxidative stress-related genes in the development of IDD using strict bioinformatic algorithms. The microarray data relevant to the IDD was downloaded from Gene Expression Omnibus database for further analysis. A series of bioinformatic strategies were used to determine the oxidative stress-related and IDD-related genes (OSIDDRGs), perform the function enrichment analysis and protein-protein interaction analysis, construct the lncRNA-miRNA-mRNA regulatory network, and investigate the potential relationship of oxidative stress to immunity abnormality and autophagy in IDD. We observed a significantly different status of oxidative stress between normal intervertebral disc tissues and IDD tissues. A total of 72 OSIDDRGs were screened out for the further function enrichment analysis, and 10 hub OSIDDRGs were selected to construct the lncRNA-miRNA-mRNA regulatory network. There was a very close association of oxidative stress with immunity abnormality and autophagy in IDD. Taken together, our findings can provide new insights into the mechanism research of oxidative stress in the development of IDD and offer new potential targets for the treatment strategies.

circ‑LRP6 contributes to osteosarcoma progression by regulating the miR‑141‑3p/HDAC4/HMGB1 axis

Circular RNA-lipoprotein receptor 6 (circ-LRP6) serves a role in promoting the tumorigenesis of retinoblastoma, esophageal squamous cell cancer and oral squamous cell carcinoma; however, whether circ-LRP6 demonstrates the same effect in osteosarcoma (OS) is yet to be fully elucidated. The present study aimed to analyze the expression, role and potential molecular mechanism of circ-LRP6 in OS. The expression levels of circ-LRP6, microRNA (miR)-141-3p, histone deacetylase 4 (HDAC4) and high mobility group protein 1 (HMGB1) were evaluated by reverse transcription- quantitative PCR in OS tissues and cell lines. Cell Counting Kit-8, Transwell and Matrigel assays were conducted to evaluate cell proliferation, migration and invasion, respectively. Western blotting was also performed to determine HDAC4 and HMGB1 protein expression levels. Bioinformatics and dual-luciferase reporter assays were used to predict and analyze the interactions between circ-LRP6 and miR-141-3p, miR-141-3p and HDAC4, as well as between miR-141-3p and HMGB1. Additionally, RNA immunoprecipitation was performed to verify the association between circ-LRP6 and miR-141-3p. The results confirmed that circ-LRP6 was highly expressed in OS tissues and cell lines. In addition, circ-LRP6 negatively regulated the expression of miR-141-3p and, in turn, miR-141-3p negatively regulated HDAC4 and HMGB1 expression. Functional assays revealed that circ-LRP6 knockdown inhibited the proliferation, migration and invasion of OS cells, whereas the inhibition of miR-141-3p or the overexpression of either HDAC4 or HMGB1 partly reversed the inhibitory effect of circ-LRP6 knockdown. In summary, the present study determined that circ-LRP6 knockdown inhibited the proliferation, migration and invasion of OS cells by regulating the miR-141-3p/HDAC4/HMGB1 axis.

Long non-coding RNA OIP5-AS1 (Cyrano): A context-specific regulator of normal and disease processes

Long non-coding (lnc) RNAs have been implicated in a plethora of normal biological functions, and have also emerged as key molecules in various disease processes. OIP5-AS1, also commonly known by the alias Cyrano, is a lncRNA that displays broad expression across multiple tissues, with significant enrichment in particular contexts including within the nervous system and skeletal muscle. Thus far, this multifaceted lncRNA has been found to have regulatory functions in normal cellular processes including cell proliferation and survival, as well as in the development and progression of a myriad disease states. These widespread effects on normal and disease states have been found to be mediated through context-specific intermolecular interactions with dozens of miRNAs and proteins identified to date. This review explores recent studies to highlight OIP5-AS1's contextual yet pleiotropic roles in normal homeostatic functions as well as disease oetiology and progression, which may influence its utility in the generation of future theranostics.

CircRNA RERE Promotes the Oxidative Stress-Induced Apoptosis and Autophagy of Nucleus Pulposus Cells through the miR-299-5p/Galectin-3 Axis

Intervertebral disc degeneration (IDD) is widely accepted as a cause of low back pain and related degenerative musculoskeletal disorders. Nucleus pulposus (NP) cell loss is closely related to IDD progression. Thus, investigating the specifically targeted therapeutic agents against NP cell loss depends on understanding the molecular mechanisms. In this study, human NP cells were treated with hydrogen peroxide (H2O2). Cell viability was assessed by using the Cell Counting Kit-8 (CCK-8) kit. The expression of circRNA arginine-glutamic acid dipeptide repeats (hsa_circ_RERE) and miR-299-5p was analyzed by real-time quantitative PCR. Western blot analysis was used to assess the protein expression levels. The autophagy levels in NP cells were detected by using an electronic microscope, LC3B protein immunofluorescence, and western blot. The apoptosis levels of NP cells were detected by flow cytometry and western blot. Dual-luciferase reporter assay analyzed the miR-299-5p bound to circ_RERE and galectin-3. Our results revealed that H2O2 significantly inhibited the viability of NP cells, promoted apoptosis and autophagy, and upregulated galectin-3 expression. miR-299-5p was reduced in IDD and H2O2-induced NP cells. The overexpression of miR-299-5p promoted cell viability and attenuated apoptosis and autophagy under H2O2 treatment. Besides, circ_RERE was upregulated in IDD and H2O2-induced NP cells. However, knockdown of circ_RERE reversed the effects of miR-299-5p overexpression on cell viability, apoptosis, and autophagy in NP cells. We propose that circ_RERE promotes the H2O2-induced apoptosis and autophagy of NP cells through the miR-299-5p/galectin-3 axis and may provide a new target for the clinical treatment of IDD.

Stem Cells and Exosomes: New Therapies for Intervertebral Disc Degeneration

Intervertebral disc degeneration (IVDD) occurs as a result of an imbalance of the anabolic and catabolic processes in the intervertebral disc, leading to an alteration in the composition of the extracellular matrix (ECM), loss of nucleus pulposus (NP) cells, excessive oxidative stress and inflammation. Degeneration of the IVD occurs naturally with age, but mechanical trauma, lifestyle factors and certain genetic abnormalities can increase the likelihood of symptomatic disease progression. IVDD, often referred to as degenerative disc disease (DDD), poses an increasingly substantial financial burden due to the aging population and increasing incidence of obesity in the United States. Current treatments for IVDD include pharmacological and surgical interventions, but these lack the ability to stop the progression of disease and restore the functionality of the IVD. Biological therapies have been evaluated but show varying degrees of efficacy in reversing disc degeneration long-term. Stem cell-based therapies have shown promising results in the regeneration of the IVD, but face both biological and ethical limitations. Exosomes play an important role in intercellular communication, and stem cell-derived exosomes have been shown to maintain the therapeutic benefit of their origin cells without the associated risks. This review highlights the current state of research on the use of stem-cell derived exosomes in the treatment of IVDD.