The Mechanism and Function of miRNA in Intervertebral Disc Degeneration

The role of sirtuins in intervertebral disc degeneration: Mechanisms and therapeutic potential

Intervertebral disc degeneration (IDD) is one of the main causes of low back pain, which affects the patients' quality of life and health and imposes a significant socioeconomic burden. Despite great efforts made by researchers to understand the pathogenesis of IDD, effective strategies for preventing and treating this disease remain very limited. Sirtuins are a highly conserved family of (NAD+)-dependent deacetylases in mammals that are involved in a variety of metabolic processes in vivo. In recent years, sirtuins have attracted much attention owing to their regulatory roles in IDD on physiological activities such as inflammation, apoptosis, autophagy, aging, oxidative stress, and mitochondrial function. At the same time, many studies have explored the therapeutic effects of sirtuins-targeting activators or micro-RNA in IDD. This review summarizes the molecular pathways of sirtuins involved in IDD, and summarizes the therapeutic role of activators or micro-RNA targeting Sirtuins in IDD, as well as the current limitations and challenges, with a view to provide possible solutions for the treatment of IDD.

Bioinformatics Research and qRT-PCR Verify Hub Genes and a Transcription Factor-MicroRNA Feedback Network in Intervertebral Disc Degeneration

The present study explores the potentials of bioinformatics analysis to identify hub genes linked to intervertebral disc degeneration (IDD) and explored the potential molecular mechanism of transcription factor-microRNA regulatory network. Furthermore, the hub genes were identified through quantitative reverse transcriptase PCR (qRT-PCR). GEO database expression profile datasets for candidate genes (GSE124272) were downloaded. Genes that were differentially expressed (DEGs) were detected utilizing limma technique in the R programming language. Search Tool for the Retrieval of Interacting Genes/Proteins and NetworkAnalyst software identified hub genes. The Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis as well as Gene Ontology annotation of the DEGs were performed using Metascape. Using Bioinformatics data from the TRRUST, StarBase, and TransmiR databases, a TF-miRNA-hub genes network was constructed. qRT-PCR was utilized to confirm the result. As compared to healthy persons, 521 DEGs, comprising 203 down-regulated and 318 up-regulated genes, as well as 7 core genes, were found in people with IDD. Analysis revealed that all seven essential genes were under-expressed. qRT-PCR further confirmed the low expression of these seven important genes. Based on the TRRUST database, 16 TFs that could target five junction genes were then predicted. According to the StarBase database, four miRNAs were linked to crucial genes, while the TransmiR database predicted regulatory connections between four miRNAs and five TFs. The expression of the TP53-(hsa-miR-183-5p)-CCNB1 TF-miRNA-mRNA interaction network was discovered to be correlated with IDD. Throughout this investigation, a network of TF-miRNA-mRNA connections was built for investigation of the probable molecular mechanisms responsible for IDD. The identification of hub genes associated with IDD may reveal promising IDD treatment strategies.

Progress in the study of molecular mechanisms of intervertebral disc degeneration

Degenerative intervertebral disc disease (IVDD) is one of the main spinal surgery, conditions, which markedly increases the incidence of low back pain and deteriorates the patient's quality of life, and it imposes significant social and economic burdens. The molecular pathology of IVDD is highly complex and multilateral however still not ompletely understood. New findings indicate that IVDD is closely associated with inflammation, oxidative stress, cell injury and extracellular matrix metabolismdysregulation. Symptomatic management is the main therapeutic approach adopted for IVDD, but it fails to address the basic pathological changes and the causes of the disease. However, research is still focusing on molecular aspects in terms of gene expression, growth factors and cell signaling pathways in an attempt to identify specific molecular targets for IVDD treatment. The paper summarizes the most recent achievements in molecularunderstanding of the pathogenesis of IVDD and gives evidence-based recommendations for clinical practice.

MicroRNA-targeting nanomedicines for the treatment of intervertebral disc degeneration

Low back pain stands as a pervasive global health concern, afflicting almost 80% of adults at some point in their lives with nearly 40% attributable to intervertebral disc degeneration (IVDD). As only symptomatic relief can be offered to patients there is a dire need for innovative treatments.Given the accumulating evidence that multiple microRNAs (miRs) are dysregulated during IVDD, they could have a huge potential against this debilitating condition. The way miRs can profoundly modulate signaling pathways and influence several cellular processes at once is particularly exciting to tackle this multifaceted disorder. However, miR delivery encounters extracellular and intracellular biological barriers. A promising technology to address this challenge is the vectorization of miRs within nanoparticles, providing both protection and enhancing their uptake within the scarce target cells of the degenerated IVD. This comprehensive review presents the diverse spectrum of miRs' connection with IVDD and demonstrates their therapeutic potential when vectorized in nanomedicines.

Updates on Pathophysiology of Discogenic Back Pain

Discogenic back pain, a subset of chronic back pain, is caused by intervertebral disc (IVD) degeneration, and imparts a notable socioeconomic health burden on the population. However, degeneration by itself does not necessarily imply discogenic pain. In this review, we highlight the existing literature on the pathophysiology of discogenic back pain, focusing on the biomechanical and biochemical steps that lead to pain in the setting of IVD degeneration. Though the pathophysiology is incompletely characterized, the current evidence favors a framework where degeneration leads to IVD inflammation, and subsequent immune milieu recruitment. Chronic inflammation serves as a basis of penetrating neovascularization and neoinnervation into the IVD. Hence, nociceptive sensitization emerges, which manifests as discogenic back pain. Recent studies also highlight the complimentary roles of low virulence infections and central nervous system (CNS) metabolic state alteration. Targeted therapies that seek to disrupt inflammation, angiogenesis, and neurogenic pathways are being investigated. Regenerative therapy in the form of gene therapy and cell-based therapy are also being explored.

Strategies for Cartilage Repair in Osteoarthritis Based on Diverse Mesenchymal Stem Cells-Derived Extracellular Vesicles

Osteoarthritis (OA) causes disability and significant economic and social burden. Cartilage injury is one of the main pathological features of OA, and is often manifested by excessive chondrocyte death, inflammatory response, abnormal bone metabolism, imbalance of extracellular matrix (ECM) metabolism, and abnormal vascular or nerve growth. Regrettably, due to the avascular nature of cartilage, its capacity to repair is notably limited. Mesenchymal stem cells-derived extracellular vesicles (MSCs-EVs) play a pivotal role in intercellular communication, presenting promising potential not only as early diagnostic biomarkers in OA but also as efficacious therapeutic strategy. MSCs-EVs were confirmed to play a therapeutic role in the pathological process of cartilage injury mentioned above. This paper comprehensively provides the functions and mechanisms of MSCs-EVs in cartilage repair.

Programmable DNA hydrogel provides suitable microenvironment for enhancing autophagy-based therapies in intervertebral disc degeneration treatment

The pathogenesis of intervertebral disc degeneration (IVDD) is attributed to metabolic dysregulation within the extracellular matrix and heightened apoptosis of nucleus pulposus cells (NPC). Therefore, a potential therapeutic strategy for managing IVDD involves the reestablishment of metabolic equilibrium within the extracellular matrix and the suppression of excessive myeloid cell apoptosis. The microRNA, miR-5590, displays marked differential expression in degenerative nucleus pulposus (NP) tissues and exerts a direct influence on the regulation of DDX5 expression. This, in turn, modulates mammalian target of rapamycin (mTOR) phosphorylation, thereby impacting autophagy and apoptosis. However, ensuring the smooth delivery of miRNA to a specific injury site poses a significant challenge. To address this issue, a multifunctional DNA hydrogel was developed and subsequently loaded with miR-5590 via spherical nucleic acids (SNAs) for the treatment of IVDD. The hydrogel, which exhibits versatility, has the potential to be administered through injection at the site of injury, resulting in a consistent and prolonged release of miR-5590. This leads to the creation of a genetic microenvironment within the NP, which triggers the onset of autophagy in NPCs and subsequently suppresses apoptosis. As a result, this process regulates the metabolic equilibrium within the extracellular matrix, thereby impeding the in vitro and in vivo progression of IVDD. The amalgamation of miRNAs and biomaterials offers a promising therapeutic strategy for the management of IVDD in clinical settings.

GREM1, LRPPRC and SLC39A4 as potential biomarkers of intervertebral disc degeneration: a bioinformatics analysis based on multiple microarray and single-cell sequencing data

BACKGROUND

Low back pain (LBP) has drawn much widespread attention and is a major global health concern. In this field, intervertebral disc degeneration (IVDD) is frequently the focus of classic studies. However, the mechanistic foundation of IVDD is unclear and has led to conflicting outcomes.

METHODS

Gene expression profiles (GSE34095, GSE147383) of IVDD patients alongside control groups were analyzed to identify differentially expressed genes (DEGs) in the GEO database. GSE23130 and GSE70362 were applied to validate the yielded key genes from DEGs by means of a best subset selection regression. Four machine-learning models were established to assess their predictive ability. Single-sample gene set enrichment analysis (ssGSEA) was used to profile the correlation between overall immune infiltration levels with Thompson grades and key genes. The upstream targeting miRNAs of key genes (GSE63492) were also analyzed. A single-cell transcriptome sequencing data (GSE160756) was used to define several cell clusters of nucleus pulposus (NP), annulus fibrosus (AF), and cartilaginous endplate (CEP) of human intervertebral discs and the distribution of key genes in different cell clusters was yielded.

RESULTS

By developing appropriate p-values and logFC values, a total of 6 DEGs was obtained. 3 key genes (LRPPRC, GREM1, and SLC39A4) were validated by an externally validated predictive modeling method. The ssGSEA results indicated that key genes were correlated with the infiltration abundance of multiple immune cells, such as dendritic cells and macrophages. Accordingly, these 4 key miRNAs (miR-103a-3p, miR-484, miR-665, miR-107) were identified as upstream regulators targeting key genes using the miRNet database and external GEO datasets. Finally, the spatial distribution of key genes in AF, CEP, and NP was plotted. Pseudo-time series and GSEA analysis indicated that the expression level of GREM1 and the differentiation trajectory of NP chondrocytes are generally consistent. GREM1 may mainly exacerbate the degeneration of NP cells in IVDD.

CONCLUSIONS

Our study gives a novel perspective for identifying reliable and effective gene therapy targets in IVDD.

Preclinical to clinical translation for intervertebral disc repair: Effects of species-specific scale, metabolism, and matrix synthesis rates on cell-based regeneration

Background

A significant hurdle for potential cell-based therapies is the subsequent survival and regenerative capacity of implanted cells. While many exciting developments have demonstrated promise preclinically, cell-based therapies for intervertebral disc (IVD) degeneration fail to translate equivalent clinical efficacy.

Aims

This work aims to ascertain the clinical relevance of both a small and large animal model by experimentally investigating and comparing these animal models to human from the perspective of anatomical scale and their cellular metabolic and regenerative potential.

Materials and Methods

First, this work experimentally investigated species-specific geometrical scale, native cell density, nutrient metabolism, and matrix synthesis rates for rat, goat, and human disc cells in a 3D microspheroid configuration. Second, these parameters were employed in silico to elucidate species-specific nutrient microenvironments and predict differences in temporal regeneration between animal models.

Results

This work presents in silico models which correlate favorably to preclinical literature in terms of the capabilities of animal regeneration and predict that compromised nutrition is not a significant challenge in small animal discs. On the contrary, it highlights a very fine clinical balance between an adequate cell dose for sufficient repair, through de novo matrix deposition, without exacerbating the human microenvironmental niche.

Discussion

Overall, this work aims to provide a path towards understanding the effect of cell injection number on the nutrient microenvironment and the "time to regeneration" between preclinical animal models and the large human IVD. While these findings help to explain failed translation of promising preclinical data and the limited results emerging from clinical trials at present, they also enable the research field and clinicians to manage expectations on cell-based regeneration.

Conclusion

Ultimately, this work provides a platform to inform the design of clinical trials, and as computing power and software capabilities increase in the future, it is conceivable that generation of patient-specific models could be used for patient assessment, as well as pre- and intraoperative planning.

Research hotspots and trends of microRNAs in intervertebral disc degeneration: a comprehensive bibliometric analysis

BACKGROUND

MicroRNAs (miRNAs) are involved in various pathological processes, such as proliferation, growth, and apoptosis, of intervertebral disc (IVD) cells and play an important role in the development of intervertebral disc degeneration (IDD). Although some studies have reported the role of miRNAs in IDD, scientific econometric analysis in this field is not available.

OBJECTIVES

We designed this study to describe the current research trends and potential mechanisms associated with the role of miRNAs in IDD and to provide new ideas for future research in this field.

METHODS

We conducted a bibliometric analysis of the publications on the role of miRNAs in IDD included in the Web of Science core collection database to elucidate the current research trends in this field. The potential mechanisms were constructed using the Arrowsmith project.

RESULTS

We found that the number of miRNAs and IDD-related publications increased over the years. China was the most important contributor to research in this field. The top three institutions in terms of number of articles published were Huazhong University of Science and Technology, Shanghai Jiao Tong University, and Xi'an Jiao Tong University. Shanghai Jiao Tong University had the highest number of citations. Experimental and thermal medicine had the maximum number of documents, and Cell promotion had the most citations. The journal with the most mean times cited per study was Annals of the Rheumatic Diseases. The author Wang K had the highest number of publications, and Wang HQ had the highest number of citations. These two authors made important contributions to the research in this field. The keyword analysis showed that recent studies have focused on miRNAs regulating nucleus pulposus cell apoptosis and proliferation. Moreover, we revealed the potential mechanisms of miRNAs associated with IDD, including miRNAs regulating the extracellular matrix (ECM) degradation, mediating cartilage endplate (CEP) degeneration, and participating in inflammatory responses.

CONCLUSION

We demonstrated the knowledge map of miRNAs and IDD-related research through bibliometric analysis and elucidated the current research status and hotspots in this field. The mechanisms by which miRNAs regulate the apoptosis and proliferation of degenerated IVDs, promote ECM degradation, mediate CEP degeneration, and participate in inflammatory responses should be explored in further studies.

MicroRNA-155 suppressed cholesterol-induced matrix degradation, pyroptosis and apoptosis by targeting RORα in nucleus pulposus cells

Intervertebral disc degeneration (IDD) is associated with low back pain, yet its inherent mechanism remains obscure. Hypercholesteremia was regarded as a risk factor for IDD, and our previous study showed that cholesterol accumulation could elicit matrix degradation in the nucleus pulposus (NP). MicroRNA-155 (miR-155) was substantiated as protective in IDD, but its role in cholesterol-induced IDD was unclear. The present study investigated whether miR-155 could mediate cholesterol-related IDD and its internal mechanisms. In vivo experiments revealed high-fat diet-induced hypercholesteremia in wild-type (WT) mice along with the occurrence of IDD, whereas Rm155LG transgenic mice showed milder NP degeneration, as evidenced by Safranin O-fast green (SF) staining and immunohistochemistry (IHC). Meanwhile, IHC showed that NLRP3 and Bax expression was also suppressed in Rm155LG mice. In vitro studies using Western blotting (WB) and immunofluorescence (IF) confirmed that the miR-155 mimic could alleviate cholesterol-induced matrix degradation, apoptosis and pyroptosis in NP. Moreover, RORα was upregulated in severely degenerated NP compared to mild IDD. It was also noted that RORα was suppressed in Rm155LG mice. In this study, we demonstrated that miR-155 could target RORα and that inhibition of RORα could prevent cholesterol-induced matrix degradation, apoptosis, and pyroptosis in NP, indicating the protective effect of miR-155 in cholesterol-induced IDD by targeting RORα.

The Use of Medical Ozone in Chronic Intervertebral Disc Degeneration Can Be an Etiological and Conservative Treatment

Degeneration of the intervertebral disc is one of the most frequent causes of lumbar pain, and it puts an extreme strain on worldwide healthcare systems. Finding a solution for this disease is an important challenge as current surgical and conservative treatments fail to bring a short-term or long-term solution to the problem. Medical ozone has yielded excellent results in intervertebral disc pathology. When it comes to extruded disc herniation, ozone is the only etiological treatment because it stimulates the immune system to absorb the herniated portion of the nucleus pulposus, thus resolving discal extrusion. This work aims to examine the biomolecular mechanisms that lead to intervertebral disc degeneration while highlighting the significance of oxidative stress and chronic inflammation. Considering that ozone is a regulator of oxidative stress and, therefore, of inflammation, we assert that medical ozone could modulate this process and obtain inflammatory stage macrophages (M1) to switch to the repair phase (M2). Consequently, the ozone would be a therapeutic resource that would work on the etiology of the disease as an epigenetic regulator that would help repair the intervertebral space.

Extracellular vesicles derived from mesenchymal stem cells confer protection against intervertebral disc degeneration through a microRNA-217-dependent mechanism

OBJECTIVE

Extracellular vesicles released by mesenchymal stem cells (MSC-EVs) can be applied to alleviate intervertebral disc degeneration (IVDD) by curbing apoptosis of nucleus pulposus cells (NPCs). The current study aims to evaluate the effect of MSC-EVs on NPC apoptosis and IVDD and the related regulatory mechanisms involving microRNA (miR)-217.

METHOD

Expression of miR-217 was examined in tumor necrosis factor-α (TNF-α)-induced NPCs and MSC-EVs, followed by identification in the relationship between miR-217, enhancer of zeste homolog 2 (EZH2) and forkhead box O-3 (FOXO3). After isolation of EVs from MSCs and subsequent co-culture with NPCs, we assessed effects of miR-217 on NPC viability, autophagy, senescence and apoptosis along with extracellular matrix (ECM) degradation. Further in vivo experiments were conducted in rat models of IVDD to substantiate the effect of miR-217 on IVDD.

RESULTS

Poor miR-217 expression was found in TNF-α-induced NPCs, while high miR-217 expression was identified in MSC-EVs (P < 0.05). MSC-EVs transferred miR-217 to NPCs and increased its expression, thus attenuating NPC apoptosis and ECM degradation (elevated collagen II and aggrecan but reduced MMP13 and ADAMTS5) (P < 0.05). miR-217 targeted EZH2, and EZH2 bound to the FOXO3 promoter and consequently downregulated its expression. FOXO3 restrained NPC apoptosis and ECM degradation by stimulating cell autophagy (P < 0.05). Furthermore, in vivo experimental results confirmed the suppressive role of miR-217 shuttled by MSC-EVs in IVDD.

CONCLUSION

Overall, the delivery of miR-217 may be a novel mechanism underlying the effect of MSC-EVs on NPC apoptosis and ECM degradation following IVDD.

N6-Methyladenosine-induced miR-143-3p promotes intervertebral disc degeneration by regulating SOX5

Intervertebral disc degeneration is the basic cause of lumbocrural pain, which not only causes pain and but also serious economic burdens on patients. Increasingly more evidence has shown that tumor necrosis factor-α (TNF-α) is involved in the pathological process of intervertebral disc degeneration, but the specific molecular mechanism is still unclear. This study investigated the potential mechanism and function of methyltransferase-like 3 (METTL3)/miR-143-3p/SOX5 regulatory axis in nucleus pulposus cells under the action of TNF-α. Human nucleus pulposus cells were treated with TNF-α to construct an in vitro model of intervertebral disc degeneration. Flow cytometry, quantitative reverse-transcription PCR (RT-qPCR), Western blot (WB) and luciferase assays were used to identify the mechanism of action of miR-143-3p in the course of intervertebral disc degeneration in vitro and the downstream targeted regulatory molecules. The role of miR-143-3p in intervertebral disc degeneration was also validated by in vivo. RT-qPCR, WB, coimmunoprecipitation (Co-IP) and flow cytometry were used to verify the regulatory effect of METTL3 on miR-143-3p maturation. RT-qPCR and WB were adopted to detect differences in METTL3, miR-143-3p and SOX5 expression in human nucleus pulposus tissue. miR-143-3p in nucleus pulposus cells was involved in the regulation of extracellular matrix metabolism and apoptosis after TNF-α stimulation, and intervertebral disc degeneration was relieved by effectively regulating miR-143-3p expression. Subsequent experiments showed that the downstream direct target gene of miR-143-3p was SOX5 and that miR-143-3p negatively regulated the expression of SOX5. In addition, METTL3 promoted miR-143-3p maturation, and METTL3 and miR-143-3p were significantly upregulated in degenerative nucleus pulposus, an effect that was significantly negatively correlated with low SOX5 expression. In conclusion, TNF-α upregulates METTL3, METTL3 promotes miR-143-3p maturation, and miR-143-3p inhibits the transcriptional activity of SOX5 through targeted binding, thereby inducing intervertebral disc degeneration. The inhibition of METTL3 or miR-143-3p expression may be an effective way to treat intervertebral disc degeneration.

Comprehensive analysis of potential ceRNA network and immune cell infiltration in intervertebral disc degeneration

Background

Intervertebral disc degeneration (IDD) has become a serious public health problem, the mechanism of which is complex and still unclear. We aimed to construct a ceRNA network related to IDD to explore its pathogenesis.

Methods

We downloaded the GSE67566, GSE63492, GSE116726 and GSE124272 datasets from GEO database, and obtained the differentially expressed RNAs. Then, we constructed a ceRNA network and the KEGG and GO enrichment analysis were performed. Finally, we performed immune cell infiltration analysis on the GSE124272 dataset and analysed the correlation between immune cell abundance and hub genes expression levels.

Results

The ceRNA network included three down-regulated circRNAs: hsa_circ_0074817, hsa_circ_0002702, hsa_circ_0003600, three up-regulated miRNAs: hsa-miR-4741, hsa-miR-3158-5p, hsa-miR-508-5p, and 57 down-regulated mRNAs, including six hub genes: IGF1, CHEK1, CCNB1, OIP5, BIRC5, AR. GO and KEGG analysis revealed that the network is involved in various biological functions. Immune infiltration analysis showed that IDD was closely related to immune cell infiltration, and hub genes could further affect the development of IDD by affecting immune cell infiltration.

Conclusion

This study identified the hsa_circ_0074817-hsa-miR-508-5p-IGF1/CHEK1/CCNB1, the hsa_circ_0003600-hsa-miR-4741-BIRC5/OIP5/AR and the hsa_circ_0002702-hsa-miR-3158-5p-IGF1/AR as important regulatory axis of IDD, which will help us gain further insight into the pathogenesis of IDD and determine potential therapeutic targets.

CircRNA expression profile and potential role of hsa_circ_0040039 in intervertebral disc degeneration

PURPOSE

Circular RNAs (circRNAs) play an critical role in the pathological processes associated with IDD. However, the potential roles of circRNAs in IDD remain largely unclear. Here, we identify the circRNAs expression profiles and elucidate the potential role of candidate circRNAs in the pathogenesis of intervertebral disc degeneration (IDD) through microarray data and bioinformatics analyses.

METHODS

We obtained the datasets of microarrays (GSE67566 and GSE116726) from the Gene Expression Omnibus database. The differentially expressed circRNAs and miRNAs were identified using the Limma R package. The target miRNAs and target genes of the candidate circRNAs were predicted using an online tool. Functional enrichment analyses of the target genes were performed using the clusterProfiler R package. A protein-protein interaction (PPI) network was constructed using STRING.

RESULTS

A total of 104 differentially expressed circRNAs were identified between the IDD and the control groups, including 41 upregulated circRNAs and 63 downregulated circRNAs (cutoff criteria (|log2 fold change| > 2, P < .05)). Hsa_circ_0040039, which was the most upregulated circRNA (log2 fold change = 2.95), was selected for further analysis. The regulatory circRNA-miRNA-mRNA network comprised hsa_circ_0040039, 2 target miRNAs (hsa-miR-424-5p and hsa-miR-15b-5p), and 77 target genes. Functional enrichment analysis showed that the 77 promising target genes are mainly enriched in the ubiquitin proteasome system and Wnt signaling pathway. Further, the PPI network showed that the top 3 hub genes are BRTC, SIAH1, and UBE2V1.

CONCLUSIONS

A total of 104 differentially expressed circRNAs were identified between the IDD and control groups. Hsa_circ_0040039 may serve as a sponge of hsa-miR-424-5p and hsa-miR-15b-5p, to regulate the expression of downstream genes (such as BRTC, SIAH1, and UBE2V1); thus, it may be involved in IDD-associated pathological processes via the Wnt/β-catenin signaling pathway. Further studies are required to confirm the potential roles of hsa_circ_0040039 in IDD.