MiR-499a-5p suppresses apoptosis of human nucleus pulposus cells and degradation of their extracellular matrix by targeting SOX4

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.

Acetylshikonin promoting PI3K/Akt pathway and inhibiting SOX4 expression to delay intervertebral disc degeneration and low back pain

This study investigated the molecular mechanism by which acetylshikonin inhibits SOX4 expression via the PI3K/Akt pathway to delay intervertebral disc degeneration (IVDD) and low back pain (LBP). Bulk RNA-seq, RT-qPCR, Western blot analysis, immunohistochemical staining, small interfering RNA (siSOX4), lentivirus (lentiv-SOX4hi ), and imaging techniques were used to assess SOX4 expression and validate its upstream regulatory pathway. Acetylshikonin and siSOX4 were injected into the IVD to measure IVDD. SOX4 expression significantly increased in degenerated IVD tissues. TNF-α increased SOX4 expression and apoptosis-related proteins in nucleus pulposus cells (NPCs). siSOX4 reduced TNF-α-induced NPCs apoptosis, while Lentiv-SOX4hi increased it. The PI3K/Akt pathway was significantly correlated with SOX4, and acetylshikonin upregulated PI3K/Akt pathway while inhibiting SOX4 expression. In the anterior puncture IVDD mouse model, SOX4 expression was upregulated, and acetylshikonin and siSOX4 delayed IVDD-induced LBP. Acetylshikonin delays IVDD-induced LBP by inhibiting SOX4 expression through the PI3K/Akt pathway. These findings offer potential therapeutic targets for future treatments.

MSC-Derived Exosomes Ameliorate Intervertebral Disc Degeneration By Regulating the Keap1/Nrf2 Axis

Bone marrow mesenchymal stem cell derived exosomes (BMSC-exos) are a crucial means of intercellular communication and can regulate a range of biological processes by reducing inflammation, decreasing apoptosis and promoting tissue repair. The process of intervertebral disc degeneration (IVDD) is accompanied by increased reactive oxygen species (ROS) because of a decrease in the expression of Nrf2, a critical transcription factor that resists excessive ROS. Our study demonstrated that BMSC-exos decreased ROS production by inhibiting Keap1 and promoting Nrf2 expression, attenuating the apoptosis, inflammation, and degeneration of nucelus pulposus (NP) cells. BMSC-exos promoted an increase in Nrf2 and nuclear translocation, while NF-κB expression was downregulated during this process. Additionally, the expression of antioxidative proteins was elevated after treatment with BMSC-exos. In vivo, we found more NP tissue retention in the BMSC-exos-treated group, along with more expression of Nrf2 and antioxidant-related proteins. Our findings demonstrated for the first time that BMSC-exos could restore the down-regulated antioxidant response system in degenerating NP cells by modulating the Keap1/Nrf2 axis. BMSC-exos could be used as an immediate ROS modulator in the treatment of intervertebral disc degeneration. When BMSC-exos were uptaken by NPCs, the expression of Keap1 decreased and this led to increased expression of Nrf2. Nuclear translocation of Nrf2 then promoted the synthesis of antioxidants against ROS and inhibited NF-kB signalling. Cellular inflammation, apoptosis, and ECM-related indicators were further reduced. Together, the process of IVDD was alleviated.

High-Tech Methods of Cytokine Imbalance Correction in Intervertebral Disc Degeneration

An important mechanism for the development of intervertebral disc degeneration (IDD) is an imbalance between anti-inflammatory and pro-inflammatory cytokines. Therapeutic and non-therapeutic approaches for cytokine imbalance correction in IDD either do not give the expected result, or give a short period of time. This explains the relevance of high-tech medical care, which is part of specialized care and includes the use of new resource-intensive methods of treatment with proven effectiveness. The aim of the review is to update knowledge about new high-tech methods based on cytokine imbalance correction in IDD. It demonstrates promise of new approaches to IDD management in patients resistant to previously used therapies, including: cell therapy (stem cell implantation, implantation of autologous cultured cells, and tissue engineering); genetic technologies (gene modifications, microRNA, and molecular inducers of IDD); technologies for influencing the inflammatory cascade in intervertebral discs mediated by abnormal activation of inflammasomes; senolytics; exosomal therapy; and other factors (hypoxia-induced factors; lysyl oxidase; corticostatin; etc.).

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.

miR-4478 Accelerates Nucleus Pulposus Cells Apoptosis Induced by Oxidative Stress by Targeting MTH1

OBJECTIVES

Low back pain is the leading cause of disability in the elderly population and is strongly associated with intervertebral disk degeneration (IVDD). However, the precise molecular mechanisms regulating IVDD remain elusive. This study aimed to investigate the role of differentially expressed miRNAs in the pathogenesis of IVDD.

MATERIALS AND METHODS

We analyzed miRNA microarray datasets to identify differentially expressed miRNAs in IVDD progression and conducted quantitative real-time polymerase chain reaction and fluorescence in situ hybridization analysis to further confirm the differential expression of miR-4478 in nucleus pulposus (NP) tissues of patients diagnosed with IVDD. Using public databases of miRNA-mRNA interactions, we predicted the target genes of miR-4478, and subsequent flow cytometry and western blot analyses demonstrated the effect of MTH1 in H 2 O 2 -induced nucleus pulposus cells (NPCs) apoptosis. Finally, miR-4478 inhibitor was injected into NP tissues of the IVDD mouse model to explore the effect of miR-4478 in vivo.

RESULTS

miR-4478 was upregulated in NP tissues from IVDD patients. Silencing of miR-4478 inhibits H 2 O 2 -induced NPCs apoptosis. MTH1 was identified as a target gene for miR-4478, and miR-4478 regulates H 2 O 2 -induced NPCs apoptosis by modulating MTH1. In addition, downregulation of miR-4478 alleviated IVDD in a mouse model.

CONCLUSIONS

In summary, our study provides evidence that miR-4478 may aggravate IVDD through its target gene MTH1 by accelerating oxidative stress in NPCs and demonstrates that miR-4478 has therapeutic potential in IVDD treatment.

Targeting Autophagy for Developing New Therapeutic Strategy in Intervertebral Disc Degeneration

Intervertebral disc degeneration (IVDD) is a prevalent cause of low back pain. IVDD is characterized by abnormal expression of extracellular matrix components such as collagen and aggrecan. In addition, it results in dysfunctional growth, senescence, and death of intervertebral cells. The biological pathways involved in the development and progression of IVDD are not fully understood. Therefore, a better understanding of the molecular mechanisms underlying IVDD could aid in the development of strategies for prevention and treatment. Autophagy is a cellular process that removes damaged proteins and dysfunctional organelles, and its dysfunction is linked to a variety of diseases, including IVDD and osteoarthritis. In this review, we describe recent research findings on the role of autophagy in IVDD pathogenesis and highlight autophagy-targeting molecules which can be exploited to treat IVDD. Many studies exhibit that autophagy protects against and postpones disc degeneration. Further research is needed to determine whether autophagy is required for cell integrity in intervertebral discs and to establish autophagy as a viable therapeutic target for IVDD.

MECHANISM OF MIR-25-3P CARRIED BY EXTRACELLULAR VESICLES DERIVED FROM PLATELET-RICH PLASMA IN IL-1β-INDUCED NUCLEUS PULPOSUS CELL DEGENERATION VIA THE SOX4/CXCR7 AXIS

ABSTRACT

Objectives: Nucleus pulposus (NP) cell degeneration promotes the progression of intervertebral disc (IVD) degeneration. MicroRNAs (miRs) are associated with IVD degeneration. This study expounded the mechanism of microRNA (miR)-25-3p carried by extracellular vesicles (EVs) derived from platelet-rich plasma (PRP) in interleukin (IL)-1β-induced NP cell degeneration. Methods: Platelet-rich plasma from mouse blood was obtained, and EVs were isolated from PRP (EVs derived from PRP [PRP-EVs]) and identified. Nucleus pulposus cells were isolated from the mouse lumbar IVD and treated with IL-1β to induce NP cell degeneration. Extracellular vesicles derived from PRP were added into NP cell culture medium. Afterward, intracellular miR-25-3p, sex determining region Y-related high-mobility-group box 4 (SOX4), and CXC chemokine receptor 7 (CXCR7) levels were examined. Nucleus pulposus cell viability, apoptosis, and inflammation were detected. Extracellular vesicles derived from PRP were labeled by PKH67 to obverse the uptake of EVs by NP cells. The binding relations between SOX4 and miR-25-3p and CXCR7 were predicted and examined. Functional rescue experiments were performed to investigate the roles of miR-25-3p, SOX4, and CXCR7 in NP cell degeneration. Results: miR-25-3p was downregulated, whereas SOX4 and CXCR7 were upregulated in IL-1β-induced NP cells. Extracellular vesicles derived from PRP increased the cell viability, and decreased apoptosis and inflammation. miR-25-3p carried by PRP-EVs into NP cells alleviated NP cell degeneration. miR-25-3p inhibited SOX4 expression and limited CXCR7 transcription. Silencing miR-25-3p or overexpressing SOX4 or CXCR7 reversed the alleviating role of PRP-EVs in NP cell degeneration. Conclusion: miR-25-3p carried by PRP-EVs into NP cells elevated intracellular miR-25-3p expression, which suppressed SOX4 expression and further limited CXCR7 transcription, thus alleviating IL-1β-induced NP cell degeneration. Extracellular vesicles derived from PRP containing miR-25-3p may be a new method for IVD treatment.

Treatment of Intervertebral Disc Degeneration

Intervertebral disc degeneration (IDD) causes a variety of signs and symptoms, such as low back pain (LBP), intervertebral disc herniation, and spinal stenosis, which contribute to high social and economic costs. IDD results from many factors, including genetic factors, aging, mechanical injury, malnutrition, and so on. The pathological changes of IDD are mainly composed of the senescence and apoptosis of nucleus pulposus cells (NPCs), the progressive degeneration of extracellular matrix (ECM), the fibrosis of annulus fibrosus (AF), and the inflammatory response. At present, IDD can be treated by conservative treatment and surgical treatment based on patients' symptoms. However, all of these can only release the pain but cannot reverse IDD and reconstruct the mechanical function of the spine. The latest research is moving towards the field of biotherapy. Mesenchymal stem cells (MSCs) are regard as the potential therapy of IDD because of their ability to self-renew and differentiate into a variety of tissues. Moreover, the non-coding RNAs (ncRNAs) are found to regulate many vital processes in IDD. There have been many successes in the in vitro and animal studies of using biotherapy to treat IDD, but how to transform the experimental data to real therapy which can apply to humans is still a challenge. This article mainly reviews the treatment strategies and research progress of IDD and indicates that there are many problems that need to be solved if the new biotherapy is to be applied to clinical treatment of IDD. This will provide reference and guidance for clinical treatment and research direction of IDD.

UBR3 promotes inflammation and apoptosis via DUSP1/p38 pathway in the nucleus pulposus cells of patients with intervertebral disc degeneration

Intervertebral disc disease (IDD) is a primary cause of low back pain, affecting 5% of individuals. Previous study have shown that dual-specificity (Thr/Tyr) phosphatase 1 (DUSP1) regulates p38 MAPK activity and DUSP1 level is regulated by ubiquitination. As an E3 ubiquitin-protein ligase, UBR3 has been shown to regulate a variety of biological processes through ubiquitination. However, the role of UBR3/DUSP1/p38 in IDD remains to be elucidated. In the current study, we found that UBR3 was significantly increased in the nucleus pulposus tissues of IDD patients and was correlated with IDD severity. Silencing UBR3 promoted the growth, inhibited apoptosis, and inhibited inflammation in primary NPCs. Mechanism study suggested that UBR3 exerted its effects through p38. Co-immunoprecipitation assay indicated that UBR3 promoted DUSP1 ubiquitination. Overexpression of DUSP1 reversed the effect of UBR3 overexpression. Our data also supported that UBR3 was positively correlated with p-p38, but negatively correlated with DUSP1 in IDD. In summary, UBR3 promotes inflammation and apoptosis via inhibiting the p38 signaling pathway by DUSP1 ubiquitination in the NPCs of IDD patients. These findings highlight the importance of UBR3/DUSP1/p38 signaling pathway in IDD and provide new insights for the prevention and treatment of IDD.

LncRNA nuclear receptor subfamily 2 group F member 1 antisense RNA 1 (NR2F1-AS1) aggravates nucleus pulposus cell apoptosis and extracellular matrix degradation

Emerging reports uncover that long noncoding RNAs (lncRNAs) help regulate intervertebral disc degeneration (IVDD). Here, we probe the function of lncRNA nuclear receptor subfamily 2 group F member 1 antisense RNA 1 (NR2F1-AS1) in IVDD. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was applied to verify the expression of NR2F1-AS1 and miR-145-5p in nucleus pulposus (NP) tissues from IVDD patients or NP cells dealt with IL-1β or TNF-α. Flow cytometry or the TdT-mediated dUTP nick end labeling (TUNEL) assay was performed to validate the apoptosis of NP cells with selective regulation of NR2F1-AS1 and miR-145-5p. ECM-related genes, FOXO1, Bax, and Bcl2 were evaluated by qRT-PCR or Western blot (WB). The targeted relationships between NR2F1-AS1 and miR-145-5p, miR-145-5p and FOXO1 were testified by the dual-luciferase reporter assay and the RNA immunoprecipitation (RIP) assay. Our outcomes substantiated that NR2F1-AS1 was up-regulated, while miR-145-5p was down-regulated in intervertebral disc tissues of IVDD patients or NP cells treated with IL-1β or TNF-α. Besides, overexpressing NR2F1-AS1 intensified ECM degradation and NP cell apoptosis induced by IL-1β, while knocking down NR2F1-AS1 or up-regulating miR-145-5p reversed IL-1β-mediated effects in NP cells. Meanwhile, NR2F1-AS1 choked miR-145-5p and abated its effects in NP cells. This study confirms that NR2F1-AS1 modulates IVDD progression by up-regulating the FOXO1 pathway through the sponge of miR-145-5p as a competitive endogenous RNA (ceRNA).

Causes of and Molecular Targets for the Treatment of Intervertebral Disc Degeneration: A Review

Intervertebral disc degeneration (IVDD) is a pathological condition that can lead to intractable back pain or secondary neurological deficits. There is no fundamental cure for this condition, and current treatments focus on alleviating symptoms indirectly. Numerous studies have been performed to date, and the major strategy for all treatments of IVDD is to prevent cell loss due to programmed or regulated cell death. Accumulating evidence suggests that several types of cell death other than apoptosis, including necroptosis, pyroptosis, and ferroptosis, are also involved in IVDD. In this study, we discuss the molecular pathway of each type of cell death and review the literature that has identified their role in IVDD. We also summarize the recent advances in targeted therapy at the RNA level, including RNA modulations through RNA interference and regulation of non-coding RNAs, for preventing cell death and subsequent IVDD. Therefore, we review the causes and possible therapeutic targets for RNA intervention and discuss the future direction of this research field.

The potential mechanisms and application prospects of non-coding RNAs in intervertebral disc degeneration

Low back pain (LBP) is one of the most common musculoskeletal symptoms and severely affects patient quality of life. The majority of people may suffer from LBP during their life-span, which leading to huge economic burdens to family and society. According to the series of the previous studies, intervertebral disc degeneration (IDD) is considered as the major contributor resulting in LBP. Furthermore, non-coding RNAs (ncRNAs), mainly including microRNAs (miRNAs), long noncoding RNAs (lncRNAs) and circular RNAs (circRNAs), can regulate diverse cellular processes, which have been found to play pivotal roles in the development of IDD. However, the potential mechanisms of action for ncRNAs in the processes of IDD are still completely unrevealed. Therefore, it is challenging to consider ncRNAs to be used as the potential therapeutic targets for IDD. In this paper, we reviewed the current research progress and findings on ncRNAs in IDD: i). ncRNAs mainly participate in the process of IDD through regulating apoptosis of nucleus pulposus (NP) cells, metabolism of extracellular matrix (ECM) and inflammatory response; ii). the roles of miRNAs/lncRNAs/circRNAs are cross-talk in IDD development, which is similar to the network and can modulate each other; iii). ncRNAs have been attempted to combat the degenerative processes and may be promising as an efficient bio-therapeutic strategy in the future. Hence, this review systematically summarizes the principal pathomechanisms of IDD and shed light on the therapeutic potentials of ncRNAs in IDD.

Human Bone Marrow Mesenchymal Stromal Cell-Derived Extracellular Vesicles Promote Proliferation of Degenerated Nucleus Pulposus Cells and the Synthesis of Extracellular Matrix Through the SOX4/Wnt/β-Catenin Axis

Objective: Intervertebral disk degeneration (IDD) is a major cause of pain in the back, neck, and radiculus. Mesenchymal stem cells (MSCs)-derived extracellular vesicles (EVs) are therapeutic in musculoskeletal degenerative diseases such as IDD. This study explored the effect and functional mechanism of human bone MSCs (hBMSCs)-derived EVs in proliferation and apoptosis of degenerated nucleus pulposus cells (DNPCs) and extracellular matrix (ECM) synthesis.

Methods: Extracellular vesicles were isolated from hBMSCs and identified. DNPCs were induced by TNF-α. EVs were incubated with DNPCs for 24h. Internalization of EVs by DNPCs, DNPCs proliferation, apoptosis, and expressions of ECM synthetic genes, degrading genes and miR-129-5p were assessed. Downstream target genes of miR-129-5p were predicted. Target relation between miR-129-5p and SRY-box transcription factor 4 (SOX4) was verified. DNPCs proliferation, apoptosis, and ECM synthesis were measured after treatment with EVs and miR-129-5p inhibitor or SOX4 overexpression. Expressions of SOX4 and Wnt/β-catenin pathway-related proteins were determined.

Results: hBMSC-EVs promoted DNPCs proliferation, inhibited apoptosis, increased expressions of ECM synthetic genes, and reduced expressions of ECM degrading genes. hBMSC-EVs carried miR-129-5p into DNPCs. Silencing miR-129-5p in EVs partially inverted the effect of EVs on DNPCs proliferation and ECM synthesis. miR-129-5p targeted SOX4. SOX4 overexpression annulled the effect of EVs on DNPCs proliferation and ECM synthesis. Expressions of Wnt1 and β-catenin were decreased in EVs-treated DNPCs, while silencing miR-129-5p in EVs promoted expressions of Wnt1 and β-catenin.

Conclusion: hBMSC-EVs promoted DNPCs proliferation and ECM synthesis by carrying miR-129-5p into DNPCs to target SOX4 and deactivating the Wnt/β-catenin axis.

miR-489-3p overexpression inhibits lipopolysaccharide-induced nucleus pulposus cell apoptosis, inflammation and extracellular matrix degradation via targeting Toll-like receptor 4

Intervertebral disc degeneration (IDD) is a common disease with a high morbidity rate, which results in a significant deterioration in the quality of life of patients. MicroRNAs (miRNAs/miRs) are a class of endogenous small non-coding RNAs that influence target genes and serve critical roles in numerous biological processes. However, the role of miR-489-3p in lumbar disc degeneration is yet to be elucidated. In the present study, human NP cells were treated with 10 ng/ml lipopolysaccharide (LPS) for 24 h to investigate the role of miR-489-3p in IDD in an in vitro model. Reverse transcription-quantitative (RT-q)PCR was performed to determine the expression levels of miR-489-3p. Then, the TargetScan database was used to predict the potential binding sites between miR-489-3p and Toll-like receptor (TLR)4, and a dual-luciferase reporter assay was performed to verify the findings. Subsequently, RT-qPCR and western blotting were used to analyze the expression levels of TLR4. In addition, human nucleus pulposus (NP) cells were transfected with a miR-489-3p mimic and TLR4 overexpression plasmid to study the effects of miR-489-3p on LPS-induced human NP cells. Cell apoptosis and cell viability were also determined using flow cytometry and MTT assays, respectively. Finally, ELISAs were performed to analyze the levels of inflammatory factors. The expression levels of miR-489-3p were discovered to be downregulated in LPS-treated human NP cells. In addition, TLR4 was revealed to be a direct target gene of miR-489-3p, and its expression levels were upregulated in LPS-treated human NP cells. miR-489-3p was found to inhibit the LPS-induced decreases in cell viability and increases in apoptosis, and the concentration of inflammatory cytokines. Furthermore, miR-489-3p suppressed the LPS-induced decreases in extracellular matrix deposition via decreasing the expression levels of aggrecan and collagen type II in human NP cells. Finally, the results revealed that miR-489-3p inhibited the LPS-induced activation of the NF-κB signaling pathway in human NP cells. Conversely, all of the effects of miR-489-3p on LPS-induced human NP cells were reversed by the TLR4 overexpression plasmid. These findings suggested that miR-489-3p may represent a novel therapeutic target for the treatment of IDD.

miR-19b-3p relieves intervertebral disc degeneration through modulating PTEN/PI3K/Akt/mTOR signaling pathway

Emerging studies have revealed that non-coding RNAs contribute to regulating intervertebral disc degeneration (IVDD). Here, we intended to probe into the function of miR-19b-3p in IVDD evolvement. The miR-19b-3p level in the intervertebral disc (IVD) tissues of IVDD patients and IL-1β/TNF-α/hydrogen peroxide-treated human nucleus pulposus cells (HNPCs) was determined by quantitative real-time polymerase chain reaction (qRT-PCR). Also, qRT-PCR was conducted to examine the profiles of MMP-3, MMP-9, MMP-13, ADAMTS-4 and ADAMTS-5. The PTEN/PI3K/Akt/mTOR pathway was examined by Western blot (WB). The miR-19b-3p overexpression assay was carried out, and HNPC proliferation and apoptosis were compared by the cell counting kit-8 (CCK-8) assay and flow cytometry (FCM). In addition, the mechanism of action of miR-19b-3p was clarified using the PTEN inhibitor (VO-Ohpic triphosphate) or the mTOR inhibitor (Rapamycin) on the basis of IL-1β intervention and miR-19b-3p mimics transfection. Our results testified that miR-19b-3p expression was curbed in IVD tissues of the IVDD patients (vs. normal IVD tissues) and IL-1β-, TNF-α, or hydrogen peroxide-treated HNPCs. Up-regulating miR-19b-3p enhanced HNPC proliferation and hampered its apoptosis. Moreover, miR-19b-3p dampened the PTEN profile and activated the PI3K/Akt/mTOR pathway. Interestingly, attenuating PTEN reduced IL-1β-, TNF-α-, or hydrogen peroxide-mediated HNPC apoptosis and up-regulated PI3K/Akt/mTOR, while inhibiting the mTOR pathway offset the protective function of miR-19b-3p. Further mechanism studies illustrated that miR-19b-3p targeted the 3'untranslated region (UTR) of PTEN and abated the PTEN level. This research confirmed that miR-19b-3p suppressed HNPC apoptosis in the in-vitro model of IVDD by regulating PTEN/PI3K/Akt/mTOR pathway.

ETS1 promoted cell growth, metastasis and epithelial-mesenchymal transition process in melanoma by regulating miR-16-mediated SOX4 expression

Melanoma is a malignant tumor with high metastasis and mortality. Epithelial-mesenchymal transition (EMT) was reported to be involved in the growth and metastasis of melanoma. To investigate these sections further, we showed that E26 transformation specific 1 (ETS1) could regulate growth, metastasis and EMT process of melanoma by regulating microRNA(miR)-16/SRY-related HMG box (SOX) 4 expression. MiR-16, ETS1, SOX4 and nuclear factor κB (NF-κB) expression levels in melanoma cells were examined using qPCR. ETS1, SOX4, EMT-related proteins and NF-κB signaling pathway-related proteins were examined using western blot. Cell counting kit-8 assay, transwell assay were applied to evaluate the cell proliferation, migration and invasion of melanoma cells, respectively. Besides, a dual-luciferase reporter assay was employed to verify the binding relationship between ETS1 and miR-16, miR-16 and SOX4, miR-16 and NF-κB1. We showed that ETS1 and SOX4 were upregulated in melanoma cells, while miR-16 was downregulated. MiR-16 overexpression suppressed growth, metastasis and EMT process of melanoma. We found ETS1 could bind to the promoter region of miR-16 and inhibited its transcription. ETS1 silence could inhibit growth, metastasis and EMT process of melanoma, and inhibition of miR-16 could reverse the effects. Besides, miR-16 is directly bound to SOX4 and downregulated its expression. Rescued experiments confirmed that SOX4 overexpression abolished the inhibition effect of miR-16 mimics on growth, metastasis and EMT process of melanoma. Finally, NF-κB1 as the target of miR-16 mediated downstream biological responses. ETS1 activated NF-κB signaling pathway through miR-16 via targeting SOX4, thus promoting growth, metastasis and EMT of melanoma.

Expression of miR-195 and its target gene Bcl-2 in human intervertebral disc degeneration and their effects on nucleus pulposus cell apoptosis

Objective

To investigate the expression of miR-195 and its target gene Bcl-2 in intervertebral disc degeneration (IVDD) and its effect on nucleus pulposus (NP) cell apoptosis.

Methods

The expressions of miR-195 and Bcl-2 in NP tissues of IVDD patients were quantified by qRT-PCR and western blotting, respectively. NP cells were divided into blank group, TNF-α group, TNF-α + miR-NC group, TNF-α + siBcl-2 group, and TNF-α + miR-195 inhibitors + siBcl-2 group. Cell proliferation was detected by MTT assay, cell apoptosis evaluated by flow cytometry, and mitochondrial membrane potential (MMP) tested by JC-1 staining. Moreover, the function of miR-195 on IVDD in vivo was investigated using a puncture-induced IVDD rat model.

Results

IVDD patients had significantly increased miR-195 expression and decreased Bcl-2 protein expression in NP tissues. The expression of miR-195 was negatively correlated with the expression of Bcl-2 in IVDD patients. Dual-luciferase reporter gene assay indicated that Bcl-2 was a target gene of miR-195. In comparison with blank group, TNF-α group showed decreased cell proliferation and MMP, increased cell apoptosis, upregulated expression of miR-195, Bax, and cleaved caspase 3, and downregulated Bcl-2 protein, while these changes were attenuated by miR-195 inhibitors. Additionally, siBcl-2 can reverse the protective effect of miR-195 inhibitors on TNF-α-induced NP cells. Besides, inhibition of miR-195 alleviated IVDD degeneration and NP cell apoptosis in the rat model.

Conclusion

MiR-195 was significantly upregulated in NP tissues of IVDD patients, and inhibition of miR-195 could protect human NP cells from TNF-α-induced apoptosis via upregulation of Bcl-2.

Role of microRNAs in intervertebral disc degeneration (Review)

The incidence of lower back pain caused by intervertebral disc degeneration (IDD) is gradually increasing. IDD not only affects the quality of life of the patients, but also poses a major socioeconomic burden. There is currently no optimal method for delaying or reversing IDD, mainly due to its unknown pathogenesis. MicroRNAs (miRNAs/miRs) participate in the development of a number of diseases, including IDD. Abnormal expression of miRNAs in the intervertebral disc is implicated in various pathological processes underlying the development of IDD, including nucleus pulposus (NP) cell (NPC) proliferation, NPC apoptosis, extracellular matrix remodeling, inflammation and cartilaginous endplate changes, among others. The focus of the present review was the advances in research on the involvement of miRNAs in the mechanism underlying IDD. Further research is expected to identify markers for early diagnosis of IDD and new targets for delaying or reversing IDD.

Circular RNA ITCH promotes extracellular matrix degradation via activating Wnt/β-catenin signaling in intervertebral disc degeneration

Intervertebral disc degeneration (IDD) is the prevailing spine disorder and is associated with musculoskeletal disease. The extracellular matrix (ECM) degradation is an essential hallmark of IDD progression. Circular RNAs (circRNAs), as crucial cellular regulators, participate in multiple pathological processes including IDD. Here, we tried to explore the effect of circITCH on the ECM degradation of IDD and the underlying mechanism. Significantly, the expression levels of circITCH were elevated in the IDD patients’ nucleus pulposus (NP) tissues relative to that of normal cases. CircITCH promoted apoptosis and decreased proliferation of NP cells. CircITCH contributed to ECM degradation, as demonstrated by increased ADAMTS4 and MMP13 expression and decreased aggrecan and collagen II expression. Mechanically, miR-17-5p could be sponged by circITCH and miR-17-5p inhibited ECM degradation by repressing SOX4 in degenerative NP cells. CircITCH could activate Wnt/β-catenin pathway by targeting miR-17-5p/SOX4 signaling. SOX4 overexpression, miR-17-5p inhibitor, or Wnt/β-catenin signaling activator LiCl was able to reverse circITCH knockdown-inhibited apoptosis and ECM degradation, and circITCH knockdown-enhanced proliferation in NP cells. Thus, we conclude that circITCH promotes ECM degradation in IDD by activating Wnt/β-catenin through miR-17-5p/SOX4 signaling. Our finding presents novel insight into the mechanism that circITCH modulates the IDD progression. CircITCH and SOX4 may serve as potential targets for IDD therapy.

Upregulation of miR-499a-5p Decreases Cerebral Ischemia/Reperfusion Injury by Targeting PDCD4

MiR-499a-5p was significantly downregulated in degenerative tissues and correlated with apoptosis. Nonetheless, the biological function of miR-499a-5p in acute ischemic stroke has been still unclear. In this study, we found that the plasma levels of miR-499a-5p were significantly downregulated in 64 ischemic stroke patients and negatively correlated with the National Institutes of Health Stroke Scale score. Then, we constructed cerebral ischemia/reperfusion (I/R) injury in rats after middle cerebral artery occlusion and subsequent reperfusion and oxygen-glucose deprivation and reoxygenation (OGD/R)-treated SH-SY5Y cell model. Transfection with miR-499a-5p mimic was accomplished by intracerebroventricular injection in the in vivo I/R injury model. We further found that miR-499a-5p overexpression decreased infarct volumes and cell apoptosis in the in vivo I/R stroke model using TTC and TUNEL staining. PDCD4 was a direct target of miR-499a-5p by luciferase report assay and Western blotting. Knockdown of PDCD4 reduced the infarct damage and cortical neuron apoptosis caused by I/R injury. MiR-499a-5p exerted neuroprotective roles mainly through inhibiting PDCD4-mediated apoptosis by CCK-8 assay, LDH release assay, and flow cytometry analysis. These findings suggest that miR-499a-5p might represent a novel target that regulates brain injury by inhibiting PDCD4-mediating apoptosis.

Overexpression of long non-coding RNA XIST promotes IL-1β-induced degeneration of nucleus pulposus cells through targeting miR-499a-5p

BACKGROUND

Long non-coding RNA X-interactive specific transcript (XIST) is implicated in many diseases. However, its role and interaction with microRNA (miR)-499a-5p in intervertebral disc degeneration (IDD) remained unclear.

METHODS

Nucleus pulposus (NP) tissue samples were collected and nucleus pulposus cells (NPCs) were isolated for Interleukin-1β (IL-1β) treatment and identification. XIST and miR-499a-5p expressions in the tissue were measured with quantitative real-time polymerase chain reaction (qRT-PCR). After IL-1β treatment, NPC apoptosis was detected by flow cytometry. The potential binding sites of XIST and miR-499a-5p were predicted by starBase and confirmed by dual-luciferase reporter assay. Relative expressions of tissue inhibitor of metalloproteinases-3 (TIMP-3), Matrix metalloproteinases-3 (MMP-3), MMP-13, Collagen II, Aggrecan and apoptosis-related proteins (Bcl-2 associated X protein, Bax; B-cell lymphoma 2, Bcl-2; cleaved caspase-3) were measured by qRT-PCR and Western blot as needed.

RESULTS

XIST expression was upregulated in the NP tissues of patients with IDD, and IL-1β treatment resulted in a degradation of NPCs. Overexpressed XIST promoted the effects of IL-1β on increasing NPC apoptosis and expressions of XIST, MMP-3, MMP-13, Bax and Cleaved caspase-3, but down-regulated TIMP-3, Collagen II, Aggrecan and Bcl-2 expressions. Silencing XIST, however, showed the opposite effects to its overexpression. MiR-499a-5p expression was downregulated in NP tissues of IDD patients and could bind with XIST, while its upregulation reversed the effects of overexpressed XIST in the IL-1β-treated NPCs.

CONCLUSION

Overexpressed XIST caused NPC degeneration through promoting apoptosis and extracellular matrix degradation of IL-1β-treated NPCs through targeting miR-499a-5p, and therefore can serve as a potential treatment for IDD.

The function of lncRNAs in the pathogenesis of osteoarthritis

Osteoarthritis (OA), one of the most common motor system disorders, is a degenerative disease involving progressive joint destruction caused by a variety of factors. At present, OA has become the fourth most common cause of disability in the world. However, the pathogenesis of OA is complex and has not yet been clarified. Long non-coding RNA (lncRNA) refers to a group of RNAs more than 200 nucleotides in length with limited protein-coding potential, which have a wide range of biological functions including regulating transcriptional patterns and protein activity, as well as binding to form endogenous small interference RNAs (siRNAs) and natural microRNA (miRNA) molecular sponges. In recent years, a large number of lncRNAs have been found to be differentially expressed in a variety of pathological processes of OA, including extracellular matrix (ECM) degradation, synovial inflammation, chondrocyte apoptosis, and angiogenesis. Obviously, lncRNAs play important roles in regulating gene expression, maintaining the phenotype of cartilage and synovial cells, and the stability of the intra-articular environment. This article reviews the results of the latest research into the role of lncRNAs in a variety of pathological processes of OA, in order to provide a new direction for the study of OA pathogenesis and a new target for prevention and treatment. Cite this article: Bone Joint Res 2021;10(2):122-133.

Non-coding RNAs modulate function of extracellular matrix proteins

The extracellular matrix (ECM) creates a multifaceted system for the interaction of diverse structural proteins, matricellular molecules, proteoglycans, hyaluronan, and various glycoproteins that collaborate and bind with each other to produce a bioactive polymer. Alterations in the composition and configuration of ECM elements influence the cellular phenotype, thus participating in the pathogenesis of several human disorders. Recent studies indicate the crucial roles of non-coding RNAs in the modulation of ECM. Several miRNAs such as miR-21, miR-26, miR-19, miR-140, miR-29, miR-30, miR-133 have been dysregulated in disorders that are associated with disruption or breakdown of the ECM. Moreover, expression of MALAT1, PVT1, SRA1, n379519, RMRP, PFL, TUG1, TM1P3, FAS-AS1, PART1, XIST, and expression of other lncRNAs is altered in disorders associated with the modification of ECM components. In the current review, we discuss the role of lncRNAs and miRNAs in the modification of ECM and their relevance with the pathophysiology of human disorders such as cardiac/ lung fibrosis, cardiomyopathy, heart failure, asthma, osteoarthritis, and cancers.

Low expression of miR-142-3p promotes intervertebral disk degeneration

Background

Intervertebral disk degeneration (IDD) is a degenerative disease characterized by cytoplasm loss and extracellular matrix degradation. Numerous evidence reported that miRNAs participated in IDD development. Nevertheless, the function of miR-142-3p in IDD development remains unknown. This study mainly explored the potential role and function of miR-142-3p in IDD development.

Methods

One percent fetal bovine serum was used to induce the degeneration of ATDC5 cells, and miR-142-3p level was examined by qRT-PCR. Then, miR-142-3p mimic/inhibitor and its corresponding negative control were transfected into ATDC5 normal and degenerative cells. Viability, migration, invasion, apoptosis, cycle, Bax, Bcl-2, P62, and Beclin1 expression levels were assessed using CCK8, wound healing assay, annexin V-FITC/PI staining, western blot, and qRT-PCR, respectively.

Results

The results revealed that the expression levels of MMP13, ADAMTS5, MMP3, and Col-X were increased as well as the expression levels of SOX-9 and Col-II were reduced in ATDC5 degenerative cells, indicating the degeneration model was constructed. We observed that miR-142-3p was decreased in ATDC5 degenerative cells and its suppression could promote ATDC5 cell degeneration. However, miR-142-3p overexpression could reverse the cell viability inhibition, as well as apoptosis and autophagy enhancement in ATDC5 degenerative cells.

Conclusions

Our results proved that miR-142-3p may play an important role in disk degeneration. Further animal study is needed to illustrate the role of the miR-142-3p in IDD development.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-020-02194-4.

microRNA-499a promotes the progression and chemoresistance of cervical cancer cells by targeting SOX6

Emerging evidence has indicated that microRNAs are involved in multiple processes of cancer development. Previous studies have demonstrated that microRNA-499a (miR-499a) plays both oncogenic and tumor suppressive roles in several types of malignancies, and genetic variants in miR-499a are associated with the risk of cervical cancer. However, the biological roles of miR-499a in cervical cancer have not been investigated. Quantitative real-time PCR was used to assess miR-499a expression in cervical cancer cells. Mimics or inhibitor of miR-499a was transfected into cervical cancer cells to upregulate or downregulate miR-499a expression. The effects of miR-499a expression change on cervical cancer cells proliferation, colony formation, tumorigenesis, chemosensitivity, transwell migration and invasion were assessed. The potential targets of miR-499a were predicted using online database tools and validated using real-time PCR, Western blot and luciferase reporter experiments. miR-499a was significantly upregulated in cervical cancer cells. Moreover, overexpression of miR-499a significantly enhanced the proliferation, cell cycle progression, colony formation, apoptosis resistance, migration and invasion of cervical cancer cells, while inhibiting miR-499a showed the opposite effects. Further exploration demonstrated that Sex-determining region Y box 6 was the direct target of miR-499a. miR-499a-induced SOX6 downregulation mediated the oncogenic effects of miR-499a in cervical cancer. Inhibiting miR-499a could enhance the anticancer effects of cisplatin in the xenograft mouse model of cervical cancer. Our findings for the first time suggest that miRNA-499a may play an important role in the development of cervical cancer and could serve as a potential therapeutic target.

New insights into the interplay between miRNAs and autophagy in the aging of intervertebral discs

Intervertebral disc degeneration (IDD) has been widely known as a main contributor to low back pain which has a negative socioeconomic impact worldwide. However, the underlying mechanism remains unclear. MicroRNAs (miRNAs) are a class of small noncoding RNAs that post-transcriptionally regulate gene expression and serve key roles in the ageing process of intervertebral disc. Autophagy is an evolutionarily conserved process that maintains cellular homeostasis through recycling of nutrients and degradation of damaged or aged cytoplasmic organelles. Autophagy has been proposed as a "double-edged sword" and autophagy dysfunction of IVD cells is considered as a crucial reason of IDD. A rapidly growing number of recent studies demonstrate that both miRNAs and autophagy play important roles in the progression of IDD. Furthermore, accumulated research has indicated that miRNAs target autophagy-related genes and influence the onset and development of IDD. Hence, this review focuses mainly on the current findings regarding the correlations between miRNA, autophagy, and IDD and provides new insights into the role of miRNA-autophagy pathway involved in IDD pathophysiology.

Emerging evidence on noncoding-RNA regulatory machinery in intervertebral disc degeneration: a narrative review

Intervertebral disc degeneration (IDD) is the most common cause of low-back pain. Accumulating evidence indicates that the expression profiling of noncoding RNAs (ncRNAs), including microRNAs (miRNAs), circular RNAs (circRNAs), and long noncoding RNAs (lncRNAs), are different between intervertebral disc tissues obtained from healthy individuals and patients with IDD. However, the roles of ncRNAs in IDD are still unclear until now. In this review, we summarize the studies concerning ncRNA interactions and regulatory functions in IDD. Apoptosis, aberrant proliferation, extracellular matrix degradation, and inflammatory abnormality are tetrad fundamental pathologic phenotypes in IDD. We demonstrated that ncRNAs are playing vital roles in apoptosis, proliferation, ECM degeneration, and inflammation process of IDD. The ncRNAs participate in underlying mechanisms of IDD in different ways. MiRNAs downregulate target genes’ expression by directly binding to the 3′-untranslated region of mRNAs. CircRNAs and lncRNAs act as sponges or competing endogenous RNAs by competitively binding to miRNAs and regulating the expression of mRNAs. The lncRNAs, circRNAs, miRNAs, and mRNAs widely crosstalk and form complex regulatory networks in the degenerative processes. The current review presents novel insights into the pathogenesis of IDD and potentially sheds light on the therapeutics in the future.