MicroRNA-494 promotes apoptosis and extracellular matrix degradation in degenerative human nucleus pulposus cells

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.

Exosome-mediated Repair of Intervertebral Disc Degeneration: The Potential Role of miRNAs

Intervertebral disc degeneration (IVDD) is a serious condition that manifests as low back pain, intervertebral disc protrusion, and spinal canal stenosis. At present, the main treatment methods for IVDD are surgical interventions such as discectomy, total disc replacement, and spinal fusion. However, these interventions have shown limitations, such as recurrent lumbar disc herniation after discectomy, lesions in adjacent segments, and failure of fixation. To overcome these shortcomings, researchers have been exploring stem cell transplantation therapy, such as mesenchymal stem cell (MSC) transplantation, but the treatment results are still controversial. Therefore, researchers are in search of new methods that are more efficient and have better outcomes. The exosomes from stem cells contain a variety of bioactive molecules that mediate cell interactions, and these components have been investigated for their potential therapeutic role in the repair of various tissue injuries. Recent studies have shown that MSC-derived miRNAs in exosomes and vesicles have therapeutic effects on nucleus pulposus cells, annulus fibrosus, and cartilage endplate. miRNAs play a role in many cell activities, such as cell proliferation, apoptosis, and cytokine release, by acting on mRNA translation, and they may have immense therapeutic potential, especially when combined with stem cell therapy. This article reviews the current status of research on intervertebral disc repair, especially with regard to the latest research findings on the molecular biological mechanisms of miRNAs in MSC-derived exosomes in intervertebral disc repair.

[Genetic factors in degenerative disc disease]

OBJECTIVE

To analyze available literature data on the role of genetic factors in degenerative disc disease.

METHODOLOGY

We reviewed the PubMed, MEDLINE, Cohrane Library, e-Library databases using the following keywords: degenerative spine lesions, intervertebral disc herniation, pathogenesis, genetic regulation.

RESULTS

Searching depth was 2002-2022. We reviewed 84 references. Exclusion criteria: duplicate publications, reviews without detailed description of results, opinions. Finally, we included 43 the most significant studies.

CONCLUSION

There are literature data on proinflammatory cytokines, growth factors and osteodestructive processes in pathogenesis of degenerative disc disease. However, there is only fragmentary information about the role of genetic regulation of these processes. Some factors, such as microRNA, TGF-b, VEGF, MMP are still poorly understood.

ATG7 upregulation contributes to malignant transformation of human bronchial epithelial cells by B[a]PDE via DNMT3B protein degradation and miR-494 promoter methylation

Lung cancer primarily arises from exposure to various environmental factors, particularly airborne pollutants. Among the various lung carcinogens, benzo(a)pyrene and its metabolite B[a]PDE are the strongest ones that actively contribute to lung cancer development. ATG7 is an E1-like activating enzyme and contributes to activating autophagic responses in mammal cells. However, the potential alterations of ATG7 and its role in B[a]PDE-caused lung carcinogenesis remain unknown. Here, we found that B[a]PDE exposure promoted ATG7 expression in mouse lung tissues, while B[a]PDE exposure resulted in ATG7 induction in human normal bronchial epithelial cells. Our studies also demonstrated a significant correlation between high ATG7 expression levels and poor overall survival in lung cancer patients. ATG7 knockdown significantly repressed Beas-2B cell transformation upon B[a]PDE exposure, and such promotive effect of ATG7 on cell transformation mediated the p27 translation inhibition. Further studies revealed that miR-373 inhibition was required to stabilize ATG7 mRNA, therefore increasing ATG7 expression following B[a]PDE exposure, while ATG7 induction led to the autophagic degradation of the DNA methyltransferase 3 Beta (DNMT3B) protein, in turn promoted miR-494 transcription via its promoter region methylation status suppression. We also found that the miR-494 upregulation inhibited p27 protein translation and promoted bronchial epithelial cell transformation via its directly targeting p27 mRNA 3'-UTR region. Current studies, to the best of our knowledge, are for the first time to identify that ATG7 induction and its mediated autophagy is critical for B[a]PDE-induced transformation of human normal epithelial cells.

Duhuo Jisheng Decoction suppresses apoptosis and mitochondrial dysfunction in human nucleus pulposus cells by miR-494/SIRT3/mitophagy signal axis

BACKGROUND

Increasing evidence suggests that mitophagy is responsible for the pathogenesis of intervertebral disk (IVD) degeneration. Previous studies have shown that Duhuo Jisheng Decoction (DHJSD), a classic Fangji of traditional Chinese medicine, can delay IVD degeneration; however, its specific mechanism of action is unknown. In this study, we investigated the mechanism by which DHJSD treatment prevented IVD degeneration in IL-1β-treated human nucleus pulposus (NP) cells in vitro.

METHODS

Cell Counting Kit-8 was performed to explore the effects of DHJSD on the viability of NP cells exposed to IL-1β. The mechanism by which DHJSD delays IVD degeneration was explored using luciferase reporter assay, RT-qPCR, western blotting, TUNEL assay, mitophagy detection assay, Mito-SOX, Mitotracker and in situ hybridization.

RESULTS

We observed that DHJSD enhanced the viability of NP cells treated with IL-1β in a concentration-time dependent approach. Moreover, DHJSD lessened IL-1β-induced NP apoptosis and mitochondrial dysfunction and activated mitophagy in NP cells treated with IL-1β. Mitophagy suppressor cyclosporin A reversed the beneficial impacts of DHJSD in NP cells. In addition, the differential expression of miR-494 regulated IL-1β-induced NP apoptosis and mitochondrial dysfunction, and the protective impact of miR-494 on NP cells treated with IL-1β was achieved by mitophagy activation, which was regulated by its target gene, sirtuin 3 (SIRT3). Finally, we observed that DHJSD treatment could effectively delay IL-1β-induced NP apoptosis by affecting the miR-494/SIRT3/mitophagy signal axis.

CONCLUSIONS

These results show that the miR-494/SIRT3/mitophagy signaling pathway is responsible for the apoptosis and mitochondrial dysfunction of NP cells and that DHJSD may exert protective effects against IVD degeneration by regulating the miR-494/SIRT3/mitophagy signal axis.

Mechanobiology of MicroRNAs in Intervertebral Disk Degeneration

Intervertebral disk degeneration (IDD) is an intricate pathological process contributing to one of the major causes of low back pain. The degradation of the extracellular matrix (ECM), inflammation, and apoptosis have all been investigated as critical factors involved in the pathology of degenerative disk disease. Additionally, the presence of aberrant microRNAs (miRNAs), conserved molecules that regulate the amount protein post-transcriptionally, may play a crucial role in the pathogenesis of IDD. Research regarding the dysfunction of miRNAs in IDD has been well researched over the past five years. Here, we provide a critical overview of the current knowledge of miRNAs, emphasizing the processes involved in the degenerative disk pathology.

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.

The Mechanism and Function of miRNA in Intervertebral Disc Degeneration

Intervertebral disc degeneration (IDD) disease has been considered as the main cause of low back pain (LBP), which is a very common symptom and the leading cause of disability worldwide today. The pathological mechanism of IDD remains quite complicated, and genetic, developmental, biochemical, and biomechanical factors all contribute to the development of the disease. There exists no effective, non-surgical treatment for IDD nowadays, which is largely related to the lack of knowledge of the specific mechanisms of IDD, and the lack of effective specific targets. Recently, non-coding RNA, including miRNA, has been recognized as an important regulator of gene expression. Current studies on the effects of miRNA in IDD have confirmed that a variety of miRNAs play a crucial role in the process of IDD via nucleus pulposus cells (NPC) apoptosis, abnormal proliferation, inflammatory factors, the extracellular matrix (ECM) degradation, and annulus fibrosus (AF) degeneration. In the past 10 years, research on miRNA has been quite active in IDD. This review summarizes the current research progression of miRNA in the IDD and puts forward some prospects and challenges on non-surgical treatment for IDD.

RETRACTED: Role of microRNA-15a-5p/Sox9/NF-κB axis in inflammatory factors and apoptosis of murine nucleus pulposus cells in intervertebral disc degeneration

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief. Concerns were raised over the provenance of the flow cytometry plots in Figures 6G and 7F, as detailed here: https://pubpeer.com/publications/A46066C72A3E518DD6CA192362E0DC; and here: https://docs.google.com/spreadsheets/d/1r0MyIYpagBc58BRF9c3luWNlCX8VUvUuPyYYXzxWvgY/edit#gid=262337249. In addition, a portion of Figure 2G, ‘miR-15a-5p antagomir’ group appeared to contain image similarities with Figure 2G, ‘Oe-NC’ group. The journal requested that the corresponding author comment on these concerns and provide the raw data. The authors did not respond to this request and therefore the Editor-in-Chief decided to retract the article.

NF-κB signalling pathways in nucleus pulposus cell function and intervertebral disc degeneration

Intervertebral disc degeneration (IDD) is a common clinical degenerative disease of the spine. A series of factors, such as inflammation, oxidative stress and mechanical stress, promote degradation of the extracellular matrix (ECM) of the intervertebral discs (IVD), leading to dysfunction and structural destruction of the IVD. Nuclear factor-κB (NF-κB) transcription factor has long been regarded as a pathogenic factor of IDD. Therefore, NF-κB may be an ideal therapeutic target for IDD. As NF-κB is a multifunctional functional transcription factor with roles in a variety of biological processes, a comprehensive understanding of the function and regulatory mechanism of NF-κB in IDD pathology will be useful for the development of targeted therapeutic strategies for IDD, which can prevent the progression of IDD and reduce potential risks. This review discusses the role of the NF-κB signalling pathway in the nucleus pulposus (NP) in the process of IDD to understand pathological NP degeneration further and provide potential therapeutic targets that may interfere with NF-κB signalling for IDD therapy.

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.

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.

Mir-573 regulates cell proliferation and apoptosis by targeting Bax in human degenerative disc cells following hyperbaric oxygen treatment

Background

MicroRNA (miRNA) plays a vital role in the intervertebral disc (IVD) degeneration. The expression level of miR-573 was downregulated whereas Bax was upregulated notably in human degenerative nucleus pulposus cells. In this study, we aimed to investigate the role of miR-573 in human degenerative nucleus pulposus (NP) cells following hyperbaric oxygen (HBO) treatment.

Methods

NP cells were separated from human degenerated IVD tissues. The control cells were maintained in 5% CO₂/95% air and the hyperoxic cells were exposed to 100% O₂ at 2.5 atmospheres absolute. MiRNA expression profiling was performed via microarray and confirmed by real-time PCR, and miRNA target genes were identified using bioinformatics and luciferase reporter assays. The mRNA and protein levels of Bax were measured. The proliferation of NPCs was detected using MTT assay. The protein expression levels of Bax, cleaved caspase 9, cleaved caspase 3, pro-caspase 9, and pro-caspase 3 were examined.

Results

Bioinformatics analysis indicated that the 3′ untranslated region (UTR) of the Bax mRNA contained the “seed-matched-sequence” for hsa-miR-573, which was validated via reporter assays. MiR-573 was induced by HBO and simultaneous suppression of Bax was observed in NP cells. Knockdown of miR-573 resulted in upregulation of Bax expression in HBO-treated cells. In addition, overexpression of miR-573 by HBO increased cell proliferation and coupled with inhibition of cell apoptosis. The cleavage of pro-caspase 9 and pro-caspase 3 was suppressed while the levels of cleaved caspase 9 and caspase 3 were decreased in HBO-treated cells. Transfection with anti-miR-573 partly suppressed the effects of HBO.

Conclusion

Mir-573 regulates cell proliferation and apoptosis by targeting Bax in human degenerative NP cells following HBO treatment.

Inhibited microRNA-494-5p promotes proliferation and suppresses senescence of nucleus pulposus cells in mice with intervertebral disc degeneration by elevating TIMP3

It has been unraveled that microRNAs (miRNAs) played crucial roles in processes of human diseases, while the role of miR-494-5p in intervertebral disc degeneration (IDD) remains scarcely studied. We aimed to investigate the mechanisms of miR-494-5p in IDD with the involvement of tissue inhibitor of metalloproteinase 3 (TIMP3). Expression of miR-494-5p and TIMP3 in IDD clinical specimens was assessed. The IDD models were established by needle punching, which were then injected with low expression of miR-494-5p or TIMP3 overexpression lentivirus to observe their effects on pathology and apoptosis in IDD mice. The nucleus pulposus cells were isolated and, respectively, treated with miR-494-5p inhibitor or TIMP3 overexpression plasmid to determine the viability, apoptosis, and senescence in vitro. Furthermore, the expression of Aggrecan, Col-2, Caveolin-1, and SA-β-gal in nucleus pulposus cells in vitro were measured. The target relation between miR-494-5p and TIMP3 was determined. An increased expression of miR-494-5p and a decreased expression of TIMP3 were found in IDD. Downregulation of miR-494-5p or overexpression of TIMP3 could relieve pathology and suppress nucleus pulposus cell apoptosis in IDD mice, as well as promote the viability and attenuate the apoptosis and senescence of nucleus pulposus cells from IDD mice. Moreover, inhibition of miR-494-5p or overexpression of TIMP3 upregulated Aggrecan and Col-2 expression while downregulated Caveolin-1 and SA-β-gal expression, and TIMP3 was the target gene of miR-494-5p. Results of this study indicated that the degradation of miR-494-5p ameliorates the development of IDD by elevating TIPM3, which may provide new targets for IDD treatment.

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.

Co-expression Network Analysis Revealing the Potential Regulatory Roles of LncRNAs in Atrial Fibrillation

Background:

Atrial fibrillation (AF) is one of the most common heart arrhythmic disorders all over the world. However, it is worth noting that the mechanism underlying AF is still dimness.

Methods:

In this study, we implemented a series of bioinformatics methods to explore the mechanisms of lncRNAs underlying AF pathogenesis. The present study analyzed the public datasets (GSE2240 and GSE115574) to identify differentially expressed long non-coding RNAs (lncRNAs) and mRNAs in the progression of AF.

Results:

Totally, 71 differentially expressed lncRNAs and 390 DEGs were identified in AF.Next, we performed bioinformatics analyses to explore the functions of lncRNAs in AF. Gene Ontology (GO) analysis indicated that differentially expressed lncRNAs were involved in regulating multiple key biological processes, such as cell cycle and signal transduction. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis demonstrated these lncRNAs were associated with the regulation of MAPK and Wnt signaling pathways. Eight lncRNAs (RP5-1154L15.2, RP11- 339B21.15, RP11-448A19.1, RP11-676J12.4, LOC101930415, MALAT1, NEAT1, and PWAR6) were identified to be key lncRNAs and widely co-expressed with a series of differentially expressed genes (DEGs).

Conclusion:

Although further validation was still needed, our study may be helpful to elucidate the mechanisms of lncRNAs underlying AF pathogenesis and providing further insight into identifying novel biomarkers for AF.

Interplay between C-type lectin receptors and microRNAs in cellular homeostasis and immune response

C-type lectin receptors (CLRs) belong to the family of pattern recognition receptors (PRRs). They have a critical role to play in the regulation of a range of physiological functions including development, respiration, angiogenesis, inflammation, and immunity. CLRs can recognize distinct and conserved exogenous pathogen-associated as well as endogenous damage-associated molecular patterns. These interactions set off downstream signaling cascades, leading to the production of inflammatory mediators, activation of effector immune cells as well as regulation of the developmental and physiological homeostasis. CLR signaling must be tightly controlled to circumvent the excessive inflammatory burden and to maintain the cellular homeostasis. Recently, MicroRNAs (miRNAs) have been shown to be important regulators of expression of CLRs and their downstream signaling. The delicate balance between miRNAs and CLRs seems crucial in almost all aspects of multicellular life. Any dysregulations in the miRNA-CLR axes may lead to tumorigenesis or inflammatory diseases. Here, we present an overview of the current understanding of the central role of miRNAs in the regulation of CLR expression, profoundly impacting upon homeostasis and immunity, and thus, development of therapeutics against immune disorders.

A Bioinformatic Analysis of MicroRNAs' Role in Human Intervertebral Disc Degeneration

Objectives The aim of our study was to ascertain the underlying role of microRNAs (miRNAs) in human intervertebral disc degeneration (IDD). Design Bioinformatic analysis from multiple databases. Methods Studies of the association of miRNAs and IDD were identified in multiple electronic databases. All potential studies were assessed by the same inclusion and exclusion criteria. We recorded whether miRNA expression was commonly increased or suppressed in the intervertebral disc tissues and cells of IDD subjects. We used String to identify biological process and cellular component pathways of differentially expressed genes. Results We included fifty-seven articles from 1,277 records in this study. This report identified 40 different dysregulated miRNAs in 53 studies, including studies examining cell apoptosis (26 studies, 49.06%), cell proliferation (15 studies, 28.3%), extracellular matrix (ECM) degradation (10 studies, 18.86%), and inflammation (five studies, 9.43%) in IDD patients. Three upregulated miRNAs (miR-19b, miR-32, miR-130b) and three downregulated miRNAs (miR-31, miR-124a, miR-127-5p) were considered common miRNAs in IDD tissues. The top three biological process pathways for upregulated miRNAs were positive regulation of biological process, nervous system development, and negative regulation of biological process, and the top three biological process pathways for downregulated miRNAs were negative regulation of gene expression, intracellular signal transduction, and negative regulation of biological process. Conclusions This study revealed that miRNAs could be novel targets for preventing IDD and treating patients with IDD by regulating their target genes. These results provide valuable information for medical professionals, IDD patients, and health care policy makers.

Cell Senescence: A Nonnegligible Cell State under Survival Stress in Pathology of Intervertebral Disc Degeneration

The intervertebral disc degeneration (IDD) with increasing aging mainly manifests as low back pain (LBP) accompanied with a loss of physical ability. These pathological processes can be preliminarily interpreted as a series of changes at cellular level. In addition to cell death, disc cells enter into the stagnation with dysfunction and deteriorate tissue microenvironment in degenerative discs, which is recognized as cell senescence. During aging, many intrinsic and extrinsic factors have been proved to have strong connections with these cellular senescence phenomena. Growing evidences of these connections require us to gather up critical cues from potential risk factors to pathogenesis and relative interventions for retarding cell senescence and attenuating degenerative changes. In this paper, we try to clarify another important cell state apart from cell death in IDD and discuss senescence-associated changes in cells and extracellular microenvironment. Then, we emphasize the role of oxidative stress and epigenomic perturbations in linking risk factors to cell senescence in the onset of IDD. Further, we summarize the current interventions targeting senescent cells that may exert the benefits of antidegeneration in IDD.

MicroRNAs in Intervertebral Disc Degeneration, Apoptosis, Inflammation, and Mechanobiology

Intervertebral disc (IVD) degeneration is a multifactorial pathological process associated with low back pain, the leading cause of years lived in disability worldwide. Key characteristics of the pathological changes connected with degenerative disc disease (DDD) are the degradation of the extracellular matrix (ECM), apoptosis and senescence, as well as inflammation. The impact of nonphysiological mechanical stresses on IVD degeneration and inflammation, the mechanisms of mechanotransduction, and the role of mechanosensitive miRNAs are of increasing interest. As post-transcriptional regulators, miRNAs are known to affect the expression of 30% of proteincoding genes and numerous intracellular processes. The dysregulation of miRNAs is therefore associated with various pathologies, including degenerative diseases such as DDD. This review aims to give an overview of the current status of miRNA research in degenerative disc pathology, with a special focus on the involvement of miRNAs in ECM degradation, apoptosis, and inflammation, as well as mechanobiology.

MicroRNA-221 silencing attenuates the degenerated phenotype of intervertebral disc cells

The aim of this study was to investigate the role of an antichondrogenic factor, MIR221 (miR-221), in intervertebral disc degeneration (IDD), and provide basic information for the development of a therapeutic strategy for the disc repair based on specific nucleic acid based drugs, such as miR-221 silencing. We established a relatively quick protocol to minimize artifacts from extended in vitro culture, without selecting the different types of cells from intervertebral disc (IVD) or completely disrupting extracellular matrix (ECM), but by using the whole cell population with a part of resident ECM. During the de-differentiation process miR-221 expression significantly increased. We demonstrated the effectiveness of miR-221 silencing in driving the cells towards chondrogenic lineage. AntagomiR-221 treated cells showed in fact a significant increase of expression of typical chondrogenic markers including COL2A1, ACAN and SOX9, whose loss is associated with IDD. Moreover, antagomiR-221 treatment restored FOXO3 expression and increased TRPS1 expression levels attenuating the severity grade of degeneration, and demonstrating in a context of tissue degeneration and inflammation not investigated before, that FOXO3 is target of miR-221. Data of present study are promising in the definition of new molecules useful as potential intradiscal injectable biological agents.

ERRFI1 Inhibits Proliferation and Inflammation of Nucleus Pulposus and Is Negatively Regulated by miR-2355-5p in Intervertebral Disc Degeneration

STUDY DESIGN

In vivo and in vitro studies of the role of miR-2355-5p and its possible targets in intervertebral disc degeneration (IVDD).

OBJECTIVE

To elucidate the regulatory role of miR-2355-5p in IVDD and the underlying mechanisms.

SUMMARY OF BACKGROUND DATA

IVDD, which is caused by multiple factors, is the main cause of lower back pain with or without extremity pain. However, the underlying cellular mechanisms of IVDD pathogenesis are not well elucidated. Cell hyper-proliferation, inflammation, and epidermal growth factor receptor activation have been implicated in IVDD. Up-regulated miR-2355-5p level was identified to associate with IVDD. ERRFI1 (the product of mitogen-inducible gene 6 [MIG6]) was known to inhibit epidermal growth factor receptor activation.

METHODS

We monitored the expression of miR-2355-5p and ERRFI1 in IVDD tissues and lipopolysaccharides (LPS)-treated nucleus pulposus (NP) cells. We explored the effects of ERFFI1 on NP cells proliferation and LPS-induced pro-inflammatory cytokines production. We searched the targets of miR-2355-5p and explored the effects of miR-2355-5p on NP cells proliferation and cytokines production.

RESULTS

We identified the up-regulation of miR-2355-5p and down-regulation of ERFFI1 in IVDD samples and LPS-treated NP cells. ERFFI1 inhibited NP cells proliferation and LPS-induced pro-inflammatory cytokine production. MiR-2355-5p targeted ERFFI1 and negatively regulated ERFFI1 expression. MiR-2355-5p regulated IVDD by targeting ERFFI1.

CONCLUSION

MiR-2355-5p negatively regulated ERFFI1 and prevented the effects of ERRFI1 on inhibiting NP cells proliferation and inflammation.

LEVEL OF EVIDENCE

N/A.

Systematic identification of lncRNAs and circRNAs-associated ceRNA networks in human lumbar disc degeneration

Lumbar disc degeneration (LDD) is a common cause of low back and neck pain. The molecular mechanisms underlying LDD, however, are unclear. Noncoding RNAs have been reported to participate in human diseases. We investigated a series of public datasets (GSE67566, GSE56081 and GSE63492) and identified 568 mRNAs, 55 microRNAs (miRNAs), 765 long noncoding RNAs (lncRNAs), and 586 circular RNAs (circRNAs) that were expressed differently in LDD than in normal discs. We constructed lncRNAs and circRNAs regulated competing endogenous RNAs (ceRNA) networks in LDD. Four lncRNAs, DANCR, CASK-AS1, SCARNA2, and LINC00638), and three circRNAs, hsa_circ_0005139, hsa_circ_0037858, and hsa_circ_0087890, were identified as key regulators of LDD progression. We found that hsa-miR-486-5p regulated the crosstalk among circRNA hsa_circ_0000189, lncRNA DANCR and 6 mRNAs, PYCR2, TOB1, ARHGAP5, RBPJ, CD247, SLC34A1. Gene ontology (GO) analysis demonstrated that these differently expressed lncRNAs and circRNAs were involved in cellular component organization or biogenesis, gene expression and negative regulation of metabolic processes. Our findings provide useful information for exploring new mechanisms for LDD and candidates for therapeutic targets.

Angiopoietin-like protein 8 expression and association with extracellular matrix metabolism and inflammation during intervertebral disc degeneration

Intervertebral disc degeneration (IDD) is considered the primary culprit for low back pain. Although the underlying mechanisms remain unknown, hyperactive catabolism of the extracellular matrix (ECM) and inflammation are suggested to play critical roles in IDD progression. This study was designed to elucidate the role of angiopoietin‐like protein 8 (ANGPTL8) in the progression of IDD, especially the relationship of ANGPTL8 with ECM metabolism and inflammation. A positive association between ANGPTL8 expression and degenerative grades of IDD was detected in the analysis of human nucleus pulposus tissue samples. Silencing of ANGPTL8 attenuated the degradation of the anabolic protein type collagen II, and reduced the expression of the catabolic proteins MMP3 and MMP9, and the inflammatory cytokine IL‐6 through inhibition of NF‐κB signalling activation. In addition, the effect of ANGPTL8 was evaluated in a rat model of puncture‐induced IDD. Based on the imaging results and histological examination in animal study, knockdown of ANGPTL8 was demonstrated to ameliorate the IDD progression. These results demonstrate the detrimental role of ANGPTL8 expression in the pathogenesis of IDD and may provide a new therapeutic target for IDD treatment.

miR-573 regulates cell proliferation and apoptosis by targeting Bax in nucleus pulposus cells

Background

MicroRNA (miRNA) plays a vital role in the pathogenesis of intervertebral disc degeneration (IDD). The expression and potential mechanism of miR-573 in human nucleus pulposus (NP) remains to be elucidated. In this study, we aimed to investigate the role of miR-573 in IDD.

Methods

Quantitative reverse transcription polymerase chain reaction (qRT-PCR) analysis was applied to examine the expression of miR-573 and Bax in idiopathic scoliosis tissues and IDD tissues. Human NP cells were employed for analysis. Moreover, the proliferation and apoptosis of NP cells were detected using MTT and flow cytometry assay respectively. The expression levels of Bcl-2, cleaved caspase-3, cleaved caspase-9, caspase-3 and caspase-9 in degenerative NP cells were measured by Western blotting assay. Furthermore, a luciferase reporter assay was used to verify the relationship between miR-573 and Bax.

Results

The results revealed that the mRNA expression level of miR-573 was down-regulated whereas Bax was up-regulated notably in degenerative NP cells. In addition, overexpression of miR-573 increased cell viability remarkably, coupled with inhibition of cell apoptosis. The expression level of Bcl-2 was increased while cleaved caspase-3 and cleaved caspase-9 expression levels were decreased in miR-573 overexpression NP cells. Additionally, the bioinformatics analysis underscored that Bax was a direct target gene of miR-573.

Conclusion

These results suggest that overexpression of miR-573 inhibited NP cell apoptosis by down-regulating Bax, which proved to be a novel effective strategy for IDD therapies.

MicroRNA-155 suppresses the catabolic effect induced by TNF-α and IL-1β by targeting C/EBPβ in rat nucleus pulposus cells

AIM

miR-155 is a pro-inflammatory or anti-inflammatory factor depending on the cell type in which it is expressed. miR-155 controls apoptosis and matrix degradation in nucleus pulposus (NP) cells in vitro. The aim of this study is to explore the effect of miR-155 in vivo and further investigate the mechanism of miR-155 in vitro.

METHODS

MRI, hematoxylin-eosin staining, or Collagen-II immunochemistry were performed to observe intervertebral disk degeneration in conditional miR-155 overexpression mice and miR-155 knockout mice. In vitro, a dual luciferase reporter assay, real-time PCR and western blot experiments were performed to demonstrate the effect of miR-155 on the expression of catabolic genes induced by inflammatory cytokines and determine the role of β-catenin and C/EBPβ in the miR-155-mediated modulation of the expression of catabolic genes.

RESULTS

Degeneration was observed in the lumbar disks of 1-year-old miR-155 knockout mice but not in the conditional miR-155 overexpression mice. miR-155 overexpression repressed the catabolic effect induced by TNF-α or IL-1β in vitro. Furthermore, specifically in NP cells, miR-155 overexpression suppressed the expression of C/EBPβ but not of β-catenin. Additionally, in the loss-of-function experiments using C/EBPβ siRNA, C/EBPβ knockdown repressed the expression of catabolic genes induced by TNF-α and IL-1β, which is consistent with the miR-155 results.

CONCLUSION

miR-155 is a sustainable factor for intervertebral disk and suppresses the expression of catabolic genes induced by TNF-α and IL-1β by targeting C/EBPβ in rat NP cells.

SIRT1 inhibits apoptosis in in vivo and in vitro models of spinal cord injury via microRNA-494

The aim of the present study was to investigate the function and mechanism of sirtuin 1 (SIRT1) in spinal cord injury (SCI). Reverse transcription-quantitative polymerase chain reaction was used to measure the expression levels of microRNA (miR)-494. MTT assay, lactate dehydrogenase activity assay and flow cytometry were used to analyze the effects of miR-494 on cell growth and apoptosis in a model of SCI. The present study demonstrated that SIRT1 expression was reduced; whereas miR-494 expression was increased in a rat model of SCI. Overexpression of miR-494 suppressed the protein expression levels of SIRT1, and induced p53 protein expression. Conversely, knockdown of miR-494 induced SIRT1 protein expression in an in vitro model of SCI. Furthermore, overexpression of miR-494 promoted cell apoptosis and decreased cell growth in an in vitro model of SCI; however, miR-494 knockdown enhanced cell growth and inhibited cell apoptosis. Administration of a SIRT1 agonist reduced the effects of miR-494 overexpression on cell apoptosis in an SCI model, whereas treatment with a p53 agonist reduced the effects of miR-494 knockdown on cell apoptosis in an SCI model. Together, these findings suggested that SIRT1 may inhibit apoptosis of SCI in vivo and in vitro through the p53 signaling pathway, whereas miR-494 suppressed SIRT1 and induced apoptosis.

Fibronectin induced ITGβ1/FAK-dependent apoptotic pathways determines the fate of degenerative NP cells

Intervertebral disc (IVD) degeneration is caused by a decrease in nucleus pulposus (NP) cells, due mainly to apoptosis. Focal adhesion kinase (FAK) is involved in the integrin (ITG)-mediated control of cell adhesion and anoikis (apoptosis). To explore the involvement of ITGβ1/FAK-dependent apoptotic pathways in disc degeneration, histological, and molecular biological studies on the protein expression of fibronectin (FN), ITGβ1, and syndecan 4 (SYND4) in non-degenerative and degenerative NP tissues were conducted. Degenerative NP cells were isolated and cultured in the presence of SYND4 and/or ITGβ1, with or without an FAK inhibitor. The effects of upregulation or knockdown of ITGβ1 gene expression were also examined. The TUNEL assay was used to determine the percentage of apoptotic cells. Western blotting was used to detect the expression of SYND4, ITGβ1, FAK, and downstream pathway proteins. The results showed that extracellular FN was degraded during the IVD degeneration process, detrimentally affecting the function, and survival of NP cells. The apoptotic rate was increased by ITGβ1 activation, but partially reduced by FN. After ITGβ1 knockdown, the FAK/PI3 K/AKT axis was activated in the ITGβ1/FAK-dependent pathways, resulting in increased cell adherence capacity and decreased anoikis. FN rescued the degenerative NP cells from anoikis through the FAK-dependent signaling pathways. In conclusion, the extracellular matrix protein FN is essential for maintaining the function and survival of NP cells through ITGβ1/FAK-dependent apoptotic pathways during disc degeneration. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:439-448, 2019.

Roles of miR-494 in Intervertebral Disk Degeneration and the Related Mechanism

OBJECTIVE

In this study, we focused on the regulatory roles of miR-494 in the pathogenesis of intervertebral disk degeneration (IDD) and the related mechanism.

METHODS

First, rat IDD models were established, and the expression levels of miR-494 in IDDs of the rats were examined. Next, human nucleus pulposus (NP) cells were cultured and transfected with miR-494 mimics and inhibitors, and the roles of miR-494 on the proliferation and apoptosis of cells were determined using MTT cell proliferation assay and flow cytometry methods. Furthermore, the targeting relationship between miR-494 and neuro-oncological ventral antigen 1 (NOVA1) was examined by dual luciferase reporter assay. Finally, the expression of NOVA1, Caspase-3, Bcl-2-associated X protein (BAX), and B-cell lymphoma-2 (BCL-2) was examined using real-time quantitative polymerase chain reaction and western blot methods.

RESULTS

The results demonstrated that the expression of miR-494 was significantly upregulated in IDD rats. Moreover, transfection of miR-494 inhibitors induced a significant increase in the proliferation and marked decrease in the apoptosis of the degenerated human NP cells. Transfection of miR-494 mimics has shown the opposite effects. Furthermore, NOVA1 has been confirmed as a target of miR-494, and the expressions of NOVA1 were significantly downregulated in IDD rats. In addition, transfection of miR-494 inhibitors significantly decreased the expression of Caspase-3 and BAX and markedly increased the expression of NOVA1 and BCL-2. Transfection of miR-494 mimics has shown the opposite effects.

CONCLUSIONS

miR-494 was upregulated in IDD, and miR-494 might regulate the proliferation and apoptosis of NP cells through targeting NOVA1.

Transcription factor 7-like 2 controls matrix degradation through nuclear factor κB signaling and is repressed by microRNA-155 in nucleus pulposus cells

AIM

TCF7L2, a key transcription factor in the canonical Wnt pathway, plays a vital role in the matrix degradation of chondrocytes. However, it is unknown whether TCF7L2 is important in the matrix metabolism of inner gel-like nucleus pulposus (NP) cells; thus, the aim of this study was to explore the effect and mechanism of TCF7L2 in this process.

METHODS

Western blotting and immunofluorescence analyses were used to observe TCF7L2 expression in rat and human NP tissues. Real-time PCR and western blotting were performed to detect the expression of TCF7L2 stimulated by inflammatory cytokines. Dual luciferase reporter assay, real-time PCR, western blotting and knockdown experiments were performed to demonstrate the role of NF-κB signaling in matrix regulation by TCF7L2 and the regulation of TCF7L2 by miR-155 in intervertebral disc degeneration.

KEY FINDINGS

TCF7L2 is present in rat and human NP tissues and is expressed in the nucleus of NP cells. TCF7L2 is refractory to stimulation of rat and human NP cells with the inflammatory cytokines TNF-α and IL-1β, in contrast to the results in other cell types. Loss-of-function experiments using TCF7L2 siRNA or lentiviral shTCF7L2 showed that TCF7L2 knockdown suppresses matrix degradation through p65/NF-κB signaling in the absence and presence of TNF-α. In addition, TCF7L2 expression is repressed by miR-155 overexpression and promoted by miR-155 inhibition.

SIGNIFICANCE

Overall, these results demonstrate that the suppression of TCF7L2, which is modulated by miR-155, inhibits matrix degradation through p65/NF-κB signaling. TCF7L2 suppression may have therapeutic potential in intervertebral disc degeneration.

Spermidine promotes nucleus pulposus autophagy as a protective mechanism against apoptosis and ameliorates disc degeneration

Spermidine has therapeutic effects in many diseases including as heart diastolic function, myopathic defects and neurodegenerative disorders via autophagy activation. Autophagy has been found to mitigate cell apoptosis in intervertebral disc degeneration (IDD). Accordingly, we theorize that spermidine may have beneficial effects on IDD via autophagy stimulation. In this study, spermidine's effect on IDD was evaluated in tert‐butyl hydroperoxide (TBHP)‐treated nucleus pulposus cells of SD rats in vitro as well as in a puncture‐induced rat IDD model. We found that autophagy was actuated by spermidine in nucleus pulposus cells. In addition, spermidine treatment weakened the apoptotic effects of TBHP in nucleus pulposus cells. Spermidine increased the expression of anabolic proteins including Collagen‐II and aggrecan and decreased the expression of catabolic proteins including MMP13 and Adamts‐5. Additionally, autophagy blockade using 3‐MA reversed the beneficial impact of spermidine against nucleus pulposus cell apoptosis. Autophagy was thus important for spermidine's therapeutic effect on IDD. Spermidine‐treated rats had an accentuated T2‐weighted signal and a diminished histological degenerative grade than vehicle‐treated rats, showing that spermidine inhibited intervertebral disc degeneration in vivo. Thus, spermidine protects nucleus pulposus cells against apoptosis through autophagy activation and improves disc, which may be beneficial for the treatment of IDD.

Prolactin inhibits the progression of intervertebral disc degeneration through inactivation of the NF-κB pathway in rats

Intervertebral disc degeneration (IVDD) is one of the key predisposing factors for low back pain. Although the exact mechanism remains unclear, inflammatory response and nucleus pulposus (NP) apoptosis are known to play important roles in this process. Prolactin protects against inflammation-associated chondrocyte apoptosis in arthritis. Based on prior studies, we hypothesized that prolactin might have therapeutic effects on IVDD by inhibiting the apoptosis of degenerative human disc NP cells. An experimental model of IVDD was established in 3-month-old Sprague-Dawley rats by submitting them to percutaneous disc puncture with a 20-gauge needle on levels 7–8 and 8–9 of the coccygeal vertebrae. Then the rats were injected with 20 or 200 ng prolactin on a weekly basis. Radiologic and histologic analyses were performed on days 4, 7, 14, and 28. The expression of prolactin and its receptor was analyzed in human tissue obtained from symptomatic patients undergoing microencoscopy discectomy, or from scoliosis patients undergoing deformity correction surgery. The results showed that intradiscal injection of prolactin maintained disc height and the mean signal intensity of the punctured disc. Histological analysis indicated that prolactin treatment significantly retained the complete structure of the NP and annulus fibrosus compared with the vehicle group. In addition, more collagen II, but fewer collagen I-containing tissues were detected in the prolactin treatment groups compared to the vehicle group. Moreover, low levels of tumor necrosis factor-α, interleukin-1β, cleaved-caspase 3, and TUNEL staining were observed in the prolactin treatment groups. We also demonstrated that prolactin impaired puncture-induced inflammation and cell apoptosis by downregulating activation of the NF-κB pathway. The degenerated NP tissues from patients had decreased expression of prolactin and its receptor, whereas expression was increased in the NP tissues removed from scoliosis patients. These results suggest that prolactin may be a novel therapeutic target for the treatment of IVDD.

The role of lncRNA MALAT1 in intervertebral degenerative disc disease

Intervertebral degenerative disc disease (IDDD) is a common disease in clinic that causes pain and heavy financial burden on patients with poor prognosis. However, the pathogenesis of IDDD is not clear. Long non-coding RNA (LncRNA) is involved in regulating various body growth and pathological processes by affecting cell proliferation, differentiation, and apoptosis. However, the role of lncRNAs in IDDD is rarely reported. This study aims to investigate the role and mechanism of lncRNA MALAT1 in the development of IDDD. The nucleus pulposus of the intervertebral disc were collected and the primary nucleus pulposus cells were isolated and cultured. The cells were divided into three groups, including IDDD group, empty plasmid group transfected by pcDNA3.1, or MALAT1 group transfected by pcDNA3.1-MALAT1. MALAT1 expression was detected by real-time PCR. Cell proliferation was assessed by MTT assay. Caspase 3 activity was tested by the activity detection kit. IL-1 and IL-6 levels were analyzed by ELISA. The expression of MALAT1 in IDDD nucleus pulposus cells was significantly lower than that in control group (P < 0.05). The expression of MALAT1 was significantly increased after transfection with pcDNA3.1-MALAT1 plasmid in IDDD nucleus pulposus cells, which obviously inhibited cell proliferation, enhanced Caspase 3 activity, and promoted the secretion of IL-1 and IL-6 compared with IDDD group (P < 0.05). MALAT1 level decreased in IDDD nucleus pulposus cells. Upregulation of MALAT1 expression restrained IDDD through suppressing inflammation; inhibiting nucleus pulposus cell apoptosis, and promoting cell proliferation.