Genetic Therapy for Intervertebral Disc Degeneration

Genkwanin alleviates intervertebral disc degeneration via regulating ITGA2/PI3K/AKT pathway and inhibiting apoptosis and senescence

Intervertebral disc degeneration (IVDD) is a progressive degenerative disease influenced by various factors. Genkwanin, a known anti-inflammatory flavonoid, has not been explored for its potential in IVDD management. This study aims to investigate the effects and mechanisms of genkwanin on IVDD. In vitro, cell experiments revealed that genkwanin dose-dependently inhibited Interleukin-1β-induced expression levels of inflammatory factors (Interleukin-6, inducible nitric oxide synthase, cyclooxygenase-2) and degradation metabolic protein (matrix metalloproteinase-13). Concurrently, genkwanin upregulated the expression of synthetic metabolism genes (type II collagen, aggrecan). Moreover, genkwanin effectively reduced the phosphorylation of phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin, mitogen-activated protein kinase (MAPK), and nuclear factor-κB (NF-κB) pathways. Transcriptome sequencing analysis identified integrin α2 (ITGA2) as a potential target of genkwanin, and silencing ITGA2 reversed the activation of PI3K/AKT pathway induced by Interleukin-1β. Furthermore, genkwanin alleviated Interleukin-1β-induced senescence and apoptosis in nucleus pulposus cells. In vivo animal experiments demonstrated that genkwanin mitigated the progression of IVDD in the rat model through imaging and histological examinations. In conclusion, This study suggest that genkwanin inhibits inflammation in nucleus pulposus cells, promotes extracellular matrix remodeling, suppresses cellular senescence and apoptosis, through the ITGA2/PI3K/AKT, NF-κB and MAPK signaling pathways. These findings indicate that genkwanin may be a promising therapeutic candidate for IVDD.

Effective delivery of miR-150-5p with nucleus pulposus cell-specific nanoparticles attenuates intervertebral disc degeneration

BACKGROUND

The use of gene therapy to deliver microRNAs (miRNAs) has gradually translated to preclinical application for the treatment of intervertebral disc degeneration (IDD). However, the effects of miRNAs are hindered by the short half-life time and the poor cellular uptake, owing to the lack of efficient delivery systems. Here, we investigated nucleus pulposus cell (NPC) specific aptamer-decorated polymeric nanoparticles that can load miR-150-5p for IDD treatment.

METHODS

The role of miR-150-5p during disc development and degeneration was examined by miR-150-5p knockout (KO) mice. Histological analysis was undertaken in disc specimens. The functional mechanism of miR-150-5p in IDD development was investigated by qRT-PCR assay, Western blot, coimmunoprecipitation and immunofluorescence. NPC specific aptamer-decorated nanoparticles was designed, and its penetration, stability and safety were evaluated. IDD progression was assessed by radiological analysis including X-ray and MRI, after the annulus fibrosus needle puncture surgery with miR-150-5p manipulation by intradiscal injection of nanoparticles. The investigations into the interaction between aptamer and receptor were conducted using mass spectrometry, molecular docking and molecular dynamics simulations.

RESULTS

We investigated NPC-specific aptamer-decorated polymeric nanoparticles that can bind to miR-150-5p for IDD treatment. Furthermore, we detected that nanoparticle-loaded miR-150-5p inhibitors alleviated NPC senescence in vitro, and the effects of the nanoparticles were sustained for more than 3 months in vivo. The microenvironment of NPCs improves the endo/lysosomal escape of miRNAs, greatly inhibiting the secretion of senescence-associated factors and the subsequent degeneration of NPCs. Importantly, nanoparticles delivering miR-150-5p inhibitors attenuated needle puncture-induced IDD in mouse models by targeting FBXW11 and inhibiting TAK1 ubiquitination, resulting in the downregulation of NF-kB signaling pathway activity.

CONCLUSIONS

NPC-targeting nanoparticles delivering miR-150-5p show favorable therapeutic efficacy and safety and may constitute a promising treatment for IDD.

Research on the role and mechanism of IL-17 in intervertebral disc degeneration

Intervertebral disc degeneration (IDD) is one of the primary causes of low back pain (LBP), which seriously affects patients' quality of life. In recent years, interleukin (IL)-17 has been shown to be highly expressed in the intervertebral disc (IVD) tissues and serum of patients with IDD, and IL-17A has been shown to promote IDD through multiple pathways. We first searched databases such as PubMed, Cochrane, Embase, and Web of Science using the search terms "IL-17 or interleukin 17″ and "intervertebral discs". The search period ranged from the inception of the databases to December 2023. A total of 24 articles were selected after full-text screening. The main conclusion of the clinical studies was that IL-17A levels are significantly increased in the IVD tissues and serum of IDD patients. The results from the in vitro studies indicated that IL-17A can activate signaling pathways such as the NF-κB and MAPK pathways; promote inflammatory responses, extracellular matrix degradation, and angiogenesis; and inhibit autophagy in nucleus pulposus cells. The main finding of the in vivo experiments was that puncture of animal IVDs resulted in elevated levels of IL-17A within the IVD, thereby inducing IDD. Clinical studies, in vitro experiments, and in vivo experiments confirmed that IL-17A is closely related to IDD. Therefore, drugs that target IL-17A may be novel treatments for IDD, providing a new theoretical basis for IDD therapy.

The Emerging Roles of Nanocarrier Drug Delivery System in Treatment of Intervertebral Disc Degeneration-Current Knowledge, Hot Spots, Challenges and Future Perspectives

Low back pain (LBP) is a common condition that has substantial consequences on individuals and society, both socially and economically. The primary contributor to LBP is often identified as intervertebral disc degeneration (IVDD), which worsens and leads to significant spinal problems. The conventional treatment approach for IVDD involves physiotherapy, drug therapy for pain management, and, in severe cases, surgery. However, none of these treatments address the underlying cause of the condition, meaning that they cannot fundamentally reverse IVDD or restore the mechanical function of the spine. Nanotechnology and regenerative medicine have made significant advancements in the field of healthcare, particularly in the area of nanodrug delivery systems (NDDSs). These approaches have demonstrated significant potential in enhancing the efficacy of IVDD treatments by providing benefits such as high biocompatibility, biodegradability, precise drug delivery to targeted areas, prolonged drug release, and improved therapeutic results. The advancements in different NDDSs designed for delivering various genes, cells, proteins and therapeutic drugs have opened up new opportunities for effectively addressing IVDD. This comprehensive review provides a consolidated overview of the recent advancements in the use of NDDSs for the treatment of IVDD. It emphasizes the potential of these systems in overcoming the challenges associated with this condition. Meanwhile, the insights and ideas presented in this review aim to contribute to the advancement of precise IVDD treatment using NDDSs.

Sympathetic Neurotransmitter, VIP, Delays Intervertebral Disc Degeneration via FGF18/FGFR2-Mediated Activation of Akt Signaling Pathway

Neuromodulation-related intervertebral disc degeneration (IVDD) is a novel IVDD pattern and are proposed recently. However, the mechanistic basis of neuromodulation and intervertebral disc (IVD) homeostasis remains unclear. Here, this study aimed to investigate the expression of postganglionic sympathetic nerve fiber-derived vasoactive intestinal peptide (VIP) system in human IVD tissue, and to assess the role of VIP-related neuromodulation in IVDD. Patient samples and in vitro cell experiments showed that the expression of receptors for VIP is negatively correlated with the severity of IVDD, and the administration of exogenous VIP can ameliorate interleukin 1β-induced nucleus pulposus (NP) cell apoptosis and inflammation. Further mRNA-seq analysis revealed that fibroblast growth factor 18- (FGF18)-mediated activation of V-akt murine thymoma viral oncogene homolog signaling pathway is involved in the protective effects of VIP on inflammation-induced NP cell degeneration. Further analysis identified VIP via its receptor vasoactive intestinal peptide receptor 2 can directly result in decreased expression of miR-15a-5p, which targeted FGF18. Finally, in vivo mice lumbar IVDD model confirmed that focally exogenous administration of VIP can effectively ameliorated the progression of IVDD, as shown by the radiological and histological analysis. In conclusion, these results indicated that sympathetic neurotransmitter, VIP, delayed IVDD via FGF18/FGFR2-mediated activation of V-akt murine thymoma viral oncogene homolog signaling pathway, which will broaden the horizon concerning how the neuromodulation correlates with IVDD and shed new light on novel therapeutical alternatives to IVDD.

Progress in regulating inflammatory biomaterials for intervertebral disc regeneration

Intervertebral disc degeneration (IVDD) is rising worldwide and leading to significant health issues and financial strain for patients. Traditional treatments for IVDD can alleviate pain but do not reverse disease progression, and surgical removal of the damaged disc may be required for advanced disease. The inflammatory microenvironment is a key driver in the development of disc degeneration. Suitable anti-inflammatory substances are critical for controlling inflammation in IVDD. Several treatment options, including glucocorticoids, non-steroidal anti-inflammatory drugs, and biotherapy, are being studied for their potential to reduce inflammation. However, anti-inflammatories often have a short half-life when applied directly and are quickly excreted, thus limiting their therapeutic effects. Biomaterial-based platforms are being explored as anti-inflammation therapeutic strategies for IVDD treatment. This review introduces the pathophysiology of IVDD and discusses anti-inflammatory therapeutics and the components of these unique biomaterial platforms as comprehensive treatment systems. We discuss the strengths, shortcomings, and development prospects for various biomaterials platforms used to modulate the inflammatory microenvironment, thus providing guidance for future breakthroughs in IVDD treatment.

Construction of circ_0071922-miR-15a-5p-mRNA network in intervertebral disc degeneration by RNA-sequencing

Background

Low back pain (LBP) is the main factor of global disease burden. Intervertebral disc degeneration (IVDD) has long been known as the leading reason of LBP. Increasing studies have verified that circular RNAs (circRNAs)-microRNAs (miRNAs)-mRNAs network is widely involved in the pathological processes of IVDD. However, no study was made to demonstrate the circRNAs-mediated ferroptosis, oxidative stress, extracellular matrix metabolism, and immune response in IVDD.

Methods

We collected 3 normal and 3 degenerative nucleus pulposus tissues to conduct RNA-sequencing to identify the key circRNAs and miRNAs in IVDD. Bioinformatics analysis was then conducted to construct circRNAs-miRNAs-mRNAs interaction network associated with ferroptosis, oxidative stress, extracellular matrix metabolism, and immune response. We also performed animal experiments to validate the therapeutic effects of key circRNAs in IVDD.

Results

We found that circ_0015435 was most obviously upregulated and circ_0071922 was most obviously downregulated in IVDD using RNA-sequencing. Then we observed that hsa-miR-15a-5p was the key downstream of circ_0071922, and hsa-miR-15a-5p was the top upregulated miRNA in IVDD. Bioinformatics analysis was conducted to predict that 56 immunity-related genes, 29 ferroptosis-related genes, 23 oxidative stress-related genes and 8 ECM-related genes are the targets mRNAs of hsa-miR-15a-5p. Then we constructed a ceRNA network encompassing 24 circRNAs, 6 miRNAs, and 101 mRNAs. Additionally, we demonstrated that overexpression of circ_0071922 can alleviate IVDD progression in a rat model.

Conclusions

The findings of this study suggested that circ_0071922-miR-15a-5p-mRNA signaling network might affect IVDD by modulating the nucleus pulposus cells ferroptosis, oxidative stress, ECM metabolism, and immune response, which is an effective therapeutic targets of IVDD.

Differential efficacy of two small molecule PHLPP inhibitors to promote nucleus Pulposus cell health

Background

Intervertebral disc (IVD) degeneration is associated with chronic back pain. We previously demonstrated that the phosphatase pleckstrin homology domain and leucine-rich repeat protein phosphatase (PHLPP) 1 was positively correlated with IVD degeneration and its deficiency decelerated IVD degeneration in both mouse IVDs and human nucleus pulposus (NP) cells. Small molecule PHLPP inhibitors may offer a translatable method to alleviate IVD degeneration. In this study, we tested the effectiveness of the two PHLPP inhibitors NSC117079 and NSC45586 in promoting a healthy NP phenotype.

Methods

Tail IVDs of 5-month-old wildtype mice were collected and treated with NSC117079 or NSC45586 under low serum conditions ex vivo. Hematoxylin & eosin staining was performed to examine IVD structure and NP cell morphology. The expression of KRT19 was analyzed through immunohistochemistry. Cell apoptosis was assessed by TUNEL assay. Human NP cells were obtained from patients with IVD degeneration. The gene expression of KRT19, ACAN, SOX9, and MMP13 was analyzed via real time qPCR, and AKT phosphorylation and the protein expression of FOXO1 was analyzed via immunoblot.

Results

In a mouse IVD organ culture model, NSC45586, but not NSC117079, preserved vacuolated notochordal cell morphology and KRT19 expression while suppressing cell apoptosis, counteracting the degenerative changes induced by serum deprivation, especially in males. Likewise, in degenerated human NP cells, NSC45586 increased cell viability and the expression of KRT19, ACAN, and SOX9 and reducing the expression of MMP13, while NSC117079 treatment only increased KRT19 expression. Mechanistically, NSC45586 treatment increased FOXO1 protein expression in NP cells, and inhibiting FOXO1 offset NSC45586-induced regenerative potential, especially in males.

Conclusions

Our study indicates that NSC45586 was effective in promoting NP cell health, especially in males, suggesting that PHLPP plays a key role in NP cell homeostasis and that NSC45586 might be a potential drug candidate in treating IVD degeneration.

Roles of Chemokines in Intervertebral Disk Degeneration

PURPOSE OF REVIEW

Intervertebral disc degeneration is the primary etiology of low back pain and radicular pain. This review examines the roles of crucial chemokines in different stages of degenerative disc disease, along with interventions targeting chemokine function to mitigate disc degeneration.

RECENT FINDINGS

The release of chemokines from degenerated discs facilitates the infiltration and activation of immune cells, thereby intensifying the inflammatory cascade response. The migration of immune cells into the venous lumen is concomitant with the emergence of microvascular tissue and nerve fibers. Furthermore, the presence of neurogenic factors secreted by disc cells and immune cells stimulates the activation of pain-related cation channels in the dorsal root ganglion, potentially exacerbating discogenic and neurogenic pain and intensifying the degenerative cascade response mediated by chemokines. Gaining a deeper comprehension of the functions of chemokines and immune cells in these processes involving catabolism, angiogenesis, and injury detection could offer novel therapeutic avenues for managing symptomatic disc disease.

Regulating pyroptosis by mesenchymal stem cells and extracellular vesicles: A promising strategy to alleviate intervertebral disc degeneration

Intervertebral disc degeneration (IVDD) is a main cause of low back pain (LBP), which can lead to disability and thus generate a heavy burden on society. IVDD is characterized by a decrease in nucleus pulposus cells (NPCs) and endogenous mesenchymal stem cells (MSCs), degradation of the extracellular matrix, macrophage infiltration, and blood vessel and nerve ingrowth. To date, the therapeutic approaches regarding IVDD mainly include conservative treatment and surgical intervention. However, both can only relieve symptoms rather than stop or revert the progression of IVDD, since the pathogenesis of IVDD is not yet clear. Pyroptosis, which is characterized by Caspase family dependence and conducted by the Gasdermin family, is a newly discovered mode of programmed cell death. Pyroptosis has been observed in NPCs, annulus fibrosus cells (AFCs), chondrocytes, MSCs, macrophages, vascular endothelial cells and neurons and may contribute to IVDD. MSCs are a kind of pluripotent stem cell that can be found in almost all tissues. MSCs have a strong ability to secrete extracellular vesicles (EVs), which contain exosomes, microvesicles and apoptotic bodies. EVs derived from MSCs play an important role in pyroptosis regulation and could be beneficial for alleviating IVDD. This review focuses on clarifying the regulation of pyroptosis to improve IVDD by MSCs and EVs derived from MSCs.

DNMT3a-mediated methylation of PPARγ promote intervertebral disc degeneration by regulating the NF-κB pathway

Intervertebral disc degeneration (IVDD) is a common chronic musculoskeletal disease that causes chronic low back pain and imposes an immense financial strain on patients. The pathological mechanisms underlying IVDD have not been fully elucidated. The development of IVDD is closely associated with abnormal epigenetic changes, suggesting that IVDD progression may be controlled by epigenetic mechanisms. Consequently, this study aimed to investigate the role of epigenetic regulation, including DNA methyltransferase 3a (DNMT3a)-mediated methylation and peroxisome proliferator-activated receptor γ (PPARγ) inhibition, in IVDD development. The expression of DNMT3a and PPARγ in early and late IVDD of nucleus pulposus (NP) tissues was detected using immunohistochemistry and western blotting analyses. Cellularly, DNMT3a inhibition significantly inhibited IL-1β-induced apoptosis and extracellular matrix (ECM) degradation in rat NP cells. Pretreatment with T0070907, a specific inhibitor of PPARγ, significantly reversed the anti-apoptotic and ECM degradation effects of DNMT3a inhibition. Mechanistically, DNMT3a modified PPARγ promoter hypermethylation to activate the nuclear factor-κB (NF-κB) pathway. DNMT3a inhibition alleviated IVDD progression. Conclusively, the results of this study show that DNMT3a activates the NF-κB pathway by modifying PPARγ promoter hypermethylation to promote apoptosis and ECM degradation. Therefore, we believe that the ability of DNMT3a to mediate the PPARγ/NF-κB axis may provide new ideas for the potential pathogenesis of IVDD and may become an attractive target for the treatment of IVDD.

Current status and development direction of immunomodulatory therapy for intervertebral disk degeneration

Intervertebral disk (IVD) degeneration (IVDD) is a main factor in lower back pain, and immunomodulation plays a vital role in disease progression. The IVD is an immune privileged organ, and immunosuppressive molecules in tissues reduce immune cell (mainly monocytes/macrophages and mast cells) infiltration, and these cells can release proinflammatory cytokines and chemokines, disrupting the IVD microenvironment and leading to disease progression. Improving the inflammatory microenvironment in the IVD through immunomodulation during IVDD may be a promising therapeutic strategy. This article reviews the normal physiology of the IVD and its degenerative mechanisms, focusing on IVDD-related immunomodulation, including innate immune responses involving Toll-like receptors, NOD-like receptors and the complement system and adaptive immune responses that regulate cellular and humoral immunity, as well as IVDD-associated immunomodulatory therapies, which mainly include mesenchymal stem cell therapies, small molecule therapies, growth factor therapies, scaffolds, and gene therapy, to provide new strategies for the treatment of IVDD.

Application and development of hydrogel biomaterials for the treatment of intervertebral disc degeneration: a literature review

Low back pain caused by disc herniation and spinal stenosis imposes an enormous medical burden on society due to its high prevalence and refractory nature. This is mainly due to the long-term inflammation and degradation of the extracellular matrix in the process of intervertebral disc degeneration (IVDD), which manifests as loss of water in the nucleus pulposus (NP) and the formation of fibrous disc fissures. Biomaterial repair strategies involving hydrogels play an important role in the treatment of intervertebral disc degeneration. Excellent biocompatibility, tunable mechanical properties, easy modification, injectability, and the ability to encapsulate drugs, cells, genes, etc. make hydrogels good candidates as scaffolds and cell/drug carriers for treating NP degeneration and other aspects of IVDD. This review first briefly describes the anatomy, pathology, and current treatments of IVDD, and then introduces different types of hydrogels and addresses "smart hydrogels". Finally, we discuss the feasibility and prospects of using hydrogels to treat IVDD.

The pathological mechanisms of circRNAs in mediating intervertebral disc degeneration

Lower back pain (LBP) is a worldwide health problem associated with significant economic and social burden. Intervertebral disc degeneration (IVDD) is a leading cause of LBP. Several studies show that the death of nucleus pulposus cells (NPCs), abnormal metabolism of the extracellular matrix (ECM), and inflammatory response are the key mechanisms behind the pathogenesis of IVDD. Circular RNAs (circRNAs) are key regulators of gene expression and play a significant role in regulating NPCs death, ECM homeostasis, and inflammatory response by acting as microRNAs (miRNAs) sponges in IVDD. However, the regulatory role of circRNAs in mediating IVDD remains unknown. This review comprehensively describes the normal anatomic structure and function of IVD, the pathogenesis of IVDD, the characteristics, synthesis, mechanisms, and function of circRNAs. Moreover, we highlighted the 23 circRNAs that mediate ECM metabolism, 16 circRNAs that mediate NPCs apoptosis, circ_0004354 and circ_0040039 that mediate NPCs pyroptosis, and 5 circRNAs that mediate inflammatory response in IVDD. In addition, this review presents suggestions for future studies, such as the need for further investigation on ferroptosis-related circRNAs in IVDD. This review could provide novel insights into the pathogenesis and treatment of IVDD.

Updates on Pathophysiology of Discogenic Back Pain

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

Psoralen synergizes with exosome-loaded SPC25 to alleviate senescence of nucleus pulposus cells in intervertebral disc degeneration

OBJECTIVE

To explore the mechanism of psoralen synergized with exosomes (exos)-loaded SPC25 on nucleus pulposus (NP) cell senescence in intervertebral disc degeneration (IVDD).

METHODS

IVDD cellular models were established on NP cells by tert-butyl hydroperoxide (TBHP) induction, followed by the treatment of psoralen or/and exos from adipose-derived stem cells (ADSCs) transfected with SPC25 overexpression vector (ADSCs-oe-SPC25-Exos). The viability, cell cycle, apoptosis, and senescence of NP cells were examined, accompanied by the expression measurement of aggrecan, COL2A1, Bcl-2, Bax, CDK2, p16, and p21.

RESULTS

After TBHP-induced NP cells were treated with psoralen or ADSCs-oe-SPC25-Exos, cell proliferation and the expression of aggrecan, COL2A1, Bcl-2, and CDK2 were promoted; however, the expression of Bax, p16, p21, and inflammatory factors was decreased, and cell senescence, cycle arrest, and apoptosis were inhibited. Of note, psoralen combined with ADSCs-oe-SPC25-Exos further decelerated NP cell senescence and cycle arrest compared to psoralen or ADSCs-oe-SPC25-Exos alone.

CONCLUSION

Combined treatment of psoralen and ADSCs-oe-SPC25-Exos exerted an alleviating effect on NP cell senescence, which may provide an insightful idea for IVDD treatment.

Screening of miR-15a-5p as a potential biomarker for intervertebral disc degeneration through RNA-sequencing

Low back pain (LBP) is a prevalent clinical condition that imposes substantial economic burdens on society. Intervertebral disc degeneration (IVDD) is recognized as a major contributing factor to LBP. Recent studies have highlighted the pivotal role of microRNAs (miRNAs) in regulating the onset and progression of IVDD. Understanding the involvement of miRNAs in IVDD will expand our knowledge of the underlying mechanisms and potentially identify novel therapeutic targets for managing LBP. However, the pathological process of IVDD and the miRNA-mediated pathomechanism in IVDD remain unclear. Herein, we comprehensively analyzed and divided the pathological process of IVDD into three stages based on the analysis by Risbud and colleagues. Results showed that IVDD was especially associated with cell death, oxidative stress, inflammatory and immune response, and extracellular matrix (ECM) metabolism. Subsequently, we obtained human normal and degenerative nucleus pulposus tissues, which were visually confirmed through histological staining techniques such as HE and TUNEL staining. RNA sequencing was then performed on these tissue samples. Additionally, miRNA (GSE116726) and mRNA (GSE56081/GSE70362/GSE23130/GSE34095) datasets were collected from the GEO database. Our analysis revealed that miR-15a-5p was significantly upregulated IVDD, as validated by both RNA sequencing and qRT-PCR experiments. To further refine our findings, bioinformatics analysis was conducted, merging the targets of miR-15a-5p and multiple mRNA datasets, ultimately identifying the overlapping IVDD-associated mRNAs. Notably, many cuproptosis-related genes (CRGs), ferroptosis-related genes, oxidative stress-related genes, and immunity-related genes were potential targets of miR-15a-5p. The miR-15a-5p-mRNA network was constructed using Cytoscape software. Additionally, PPI, functional, and pathway enrichment analyses of the CRGs were also performed. We found that MTF1, one of the CRGs, was highly expressed in IVDD and primarily localized in the nucleus of nucleus pulposus cells. These findings suggest that miR-15a-5p is a potential biomarker in IVDD, and targeting the miR-15a-5p-mRNA signaling pathway may be a promising strategy for treating IVDD diseases.

Identification and experimental validation of key extracellular proteins as potential targets in intervertebral disc degeneration

Aims

This study aimed, through bioinformatics analysis and in vitro experiment validation, to identify the key extracellular proteins of intervertebral disc degeneration (IDD).

Methods

The gene expression profile of GSE23130 was downloaded from the Gene Expression Omnibus (GEO) database. Extracellular protein-differentially expressed genes (EP-DEGs) were screened by protein annotation databases, and we used Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) to analyze the functions and pathways of EP-DEGs. STRING and Cytoscape were used to construct protein-protein interaction (PPI) networks and identify hub EP-DEGs. NetworkAnalyst was used to analyze transcription factors (TFs) and microRNAs (miRNAs) that regulate hub EP-DEGs. A search of the Drug Signatures Database (DSigDB) for hub EP-DEGs revealed multiple drug molecules and drug-target interactions.

Results

A total of 56 EP-DEGs were identified in the differential expression analysis. EP-DEGs were enriched in the extracellular structure organization, ageing, collagen-activated signalling pathway, PI3K-Akt signalling pathway, and AGE-RAGE signalling pathway. PPI network analysis showed that the top ten hub EP-DEGs are closely related to IDD. Correlation analysis also demonstrated a significant correlation between the ten hub EP-DEGs (p＜0.05), which were selected to construct TF-gene interaction and TF-miRNA coregulatory networks. In addition, ten candidate drugs were screened for the treatment of IDD.

Conclusion

The findings clarify the roles of extracellular proteins in IDD and highlight their potential as promising novel therapeutic targets.

Phosphorylation of KRT8 (keratin 8) by excessive mechanical load-activated PKN (protein kinase N) impairs autophagosome initiation and contributes to disc degeneration

Excessive mechanical load (overloading) is a well-documented pathogenetic factor for many mechano stress-induced pathologies, i.e. intervertebral disc degeneration (IDD). Under overloading, the balance between anabolism and catabolism within nucleus pulposus (NP) cells are badly thrown off, and NP cells undergo apoptosis. However, little is known about how the overloading is transduced to the NP cells and contributes to disc degeneration. The current study shows that conditional knockout of Krt8 (keratin 8) within NP aggravates load-induced IDD in vivo, and overexpression of Krt8 endows NP cells greater resistance to overloading-induced apoptosis and degeneration in vitro. Discovery-driven experiments shows that phosphorylation of KRT8 on Ser43 by overloading activated RHOA-PKN (protein kinase N) impedes trafficking of Golgi resident small GTPase RAB33B, suppresses the autophagosome initiation and contributes to IDD. Overexpression of Krt8 and knockdown of Pkn1 and Pkn2, at an early stage of IDD, ameliorates disc degeneration; yet only knockdown of Pkn1 and Pkn2, when treated at late stage of IDD, shows a therapeutic effect. This study validates a protective role of Krt8 during overloading-induced IDD and demonstrates that targeting overloading activation of PKNs could be a novel and effective approach to mechano stress-induced pathologies with a wider window of therapeutic opportunity.Abbreviations: AAV: adeno-associated virus; AF: anulus fibrosus; ANOVA: analysis of variance; ATG: autophagy related; BSA: bovine serum albumin; cDNA: complementary deoxyribonucleic acid; CEP: cartilaginous endplates; CHX: cycloheximide; cKO: conditional knockout; Cor: coronal plane; CT: computed tomography; Cy: coccygeal vertebra; D: aspartic acid; DEG: differentially expressed gene; DHI: disc height index; DIBA: dot immunobinding assay; dUTP: 2'-deoxyuridine 5'-triphosphate; ECM: extracellular matrix; EDTA: ethylene diamine tetraacetic acid; ER: endoplasmic reticulum; FBS: fetal bovine serum; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GPS: group-based prediction system; GSEA: gene set enrichment analysis; GTP: guanosine triphosphate; HE: hematoxylin-eosin; HRP: horseradish peroxidase; IDD: intervertebral disc degeneration; IF: immunofluorescence staining; IL1: interleukin 1; IVD: intervertebral disc; KEGG: Kyoto encyclopedia of genes and genomes; KRT8: keratin 8; KD: knockdown; KO: knockout; L: lumbar vertebra; LBP: low back pain; LC/MS: liquid chromatograph mass spectrometer; LSI: mouse lumbar instability model; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MMP3: matrix metallopeptidase 3; MRI: nuclear magnetic resonance imaging; NC: negative control; NP: nucleus pulposus; PBS: phosphate-buffered saline; PE: p-phycoerythrin; PFA: paraformaldehyde; PI: propidium iodide; PKN: protein kinase N; OE: overexpression; PTM: post translational modification; PVDF: polyvinylidene fluoride; qPCR: quantitative reverse-transcriptase polymerase chain reaction; RHOA: ras homolog family member A; RIPA: radio immunoprecipitation assay; RNA: ribonucleic acid; ROS: reactive oxygen species; RT: room temperature; TCM: rat tail compression-induced IDD model; TCS: mouse tail suturing compressive model; S: serine; Sag: sagittal plane; SD rats: Sprague-Dawley rats; shRNA: short hairpin RNA; siRNA: small interfering RNA; SOFG: safranin O-fast green; SQSTM1: sequestosome 1; TUNEL: terminal deoxynucleotidyl transferase dUTP nick end labeling; VG/ml: viral genomes per milliliter; WCL: whole cell lysate.

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.).

Intervertebral disc degeneration-Current therapeutic options and challenges

Degeneration of the intervertebral disc (IVD) is a normal part of aging. Due to the spine's declining function and the development of pain, it may affect one's physical health, mental health, and socioeconomic status. Most of the intervertebral disc degeneration (IVDD) therapies today focus on the symptoms of low back pain rather than the underlying etiology or mechanical function of the disc. The deteriorated disc is typically not restored by conservative or surgical therapies that largely focus on correcting symptoms and structural abnormalities. To enhance the clinical outcome and the quality of life of a patient, several therapeutic modalities have been created. In this review, we discuss genetic and environmental causes of IVDD and describe promising modern endogenous and exogenous therapeutic approaches including their applicability and relevance to the degeneration process.

Transcriptome-wide association study reveals candidate causal genes for lumbar spinal stenosis

Aims

Lumbar spinal stenosis (LSS) is a common skeletal system disease that has been partly attributed to genetic variation. However, the correlation between genetic variation and pathological changes in LSS is insufficient, and it is difficult to provide a reference for the early diagnosis and treatment of the disease.

Methods

We conducted a transcriptome-wide association study (TWAS) of spinal canal stenosis by integrating genome-wide association study summary statistics (including 661 cases and 178,065 controls) derived from Biobank Japan, and pre-computed gene expression weights of skeletal muscle and whole blood implemented in FUSION software. To verify the TWAS results, the candidate genes were furthered compared with messenger RNA (mRNA) expression profiles of LSS to screen for common genes. Finally, Metascape software was used to perform enrichment analysis of the candidate genes and common genes.

Results

TWAS identified 295 genes with permutation p-values < 0.05 for skeletal muscle and 79 genes associated for the whole blood, such as RCHY1 (P_TWAS = 0.001). Those genes were enriched in 112 gene ontology (GO) terms and five Kyoto Encyclopedia of Genes and Genomes pathways, such as 'chemical carcinogenesis - reactive oxygen species' (LogP value = -2.139). Further comparing the TWAS significant genes with the differentially expressed genes identified by mRNA expression profiles of LSS found 18 overlapped genes, such as interleukin 15 receptor subunit alpha (IL15RA) (P_TWAS = 0.040, P_mRNA = 0.010). Moreover, 71 common GO terms were detected for the enrichment results of TWAS and mRNA expression profiles, such as negative regulation of cell differentiation (LogP value = -2.811).

Conclusion

This study revealed the genetic mechanism behind the pathological changes in LSS, and may provide novel insights for the early diagnosis and intervention of LSS.

Development of a COX-2-Selective Fluorescent Probe for the Observation of Early Intervertebral Disc Degeneration

Cyclooxygenase-2 (COX-2) is a biomolecule known to be overexpressed in inflammation. Therefore, it has been considered a diagnostically useful marker in numerous studies. In this study, we attempted to assess the correlation between COX-2 expression and the severity of intervertebral disc (IVD) degeneration using a COX-2-targeting fluorescent molecular compound that had not been extensively studied. This compound, indomethacin-adopted benzothiazole-pyranocarbazole (IBPC1), was synthesized by introducing indomethacin—a compound with known selectivity for COX-2—into a phosphor with a benzothiazole-pyranocarbazole structure. IBPC1 exhibited relatively high fluorescence intensity in cells pretreated with lipopolysaccharide, which induces inflammation. Furthermore, we observed significantly higher fluorescence in tissues with artificially damaged discs (modeling IVD degeneration) compared to normal disc tissues. These findings indicate that IBPC1 can meaningfully contribute to the study of the mechanism of IVD degeneration in living cells and tissues and to the development of therapeutic agents.

Shape-memory collagen scaffold combined with hyaluronic acid for repairing intervertebral disc

BACKGROUND

Intervertebral disc degeneration (IVDD) is a common cause of chronic low back pain (LBP) and a socioeconomic burden worldwide. Conservative therapies and surgical treatments provide only symptomatic pain relief without promoting intervertebral disc (IVD) regeneration. Therefore, the clinical demand for disc regenerative therapies for disc repair is high.

METHODS

In this study, we used a rat tail nucleotomy model to develop mechanically stable collagen-cryogel and fibrillated collagen with shape-memory for use in minimally invasive surgery for effective treatment of IVDD. The collagen was loaded with hyaluronic acid (HA) into a rat tail nucleotomy model.

RESULTS

The shape-memory collagen structures exhibited outstanding chondrogenic activities, having completely similar physical properties to those of a typical shape-memory alginate construct in terms of water absorption, compressive properties, and shape-memorability behavior. The treatment of rat tail nucleotomy model with shape-memory collagen-cryogel/HA alleviated mechanical allodynia, maintained a higher concentration of water content, and preserved the disc structure by restoring the matrix proteins.

CONCLUSION

According to these results, the collagen-based structure could effectively repair and maintain the IVD matrix better than the controls, including HA only and shape-memory alginate with HA.

Docosahexaenoic acid alleviates the excessive degradation of extracellular matrix in the nucleus pulposus by reducing the content of lncRNA NEAT1 to prevent the progression of intervertebral disc degeneration

The pathogenesis of intervertebral disc degeneration (IVDD), as a multifactorial disease, has not been fully elucidated. However, damage to the stress-bearing system in the intervertebral disc (IVD) mediated by the excessive decomposition of extracellular matrix (ECM) in nucleus pulposus (NP) cells caused by local stimulation is widely considered the core pathological process underlying IVDD. Docosahexaenoic acid (DHA) plays a protective role in various chronic diseases. However, whether it can have such effects in IVDD has not been clearly reported. In recent years, in-depth research on the role of long non-coding RNA (lncRNA) nuclear-enriched transcript 1 (NEAT1) in various diseases has continuously emerged, but such research in the field of IVD is not sufficient. In this study, tert-butyl hydroperoxide (TBHP) was used to induce oxidative stress in human NP cells and construct a cell model of excessive ECM decomposition in vitro. A plasmid over-expressing lncRNA NEAT1 was introduced into human NP cells to establish an NP cell model. For this specific experiment, Cell Counting Kit 8 was used to explore the timing and concentration of DHA and TBHP activity. A common gene chip platform was also used to select potential lncRNAs. Western blot and immunofluorescence assays were used to detect the expression of ECM-related proteins in NP cells in each group. Quantitative real-time polymerase chain reaction was used to detect the expression of lncRNA NEAT1 in NP cells in each group. On this basis, we proved that DHA alleviates excessive degradation of the ECM in NP cells in response to oxidative stress by reducing the content of lncRNA NEAT1. In conclusion, our study reveals the mechanism through which DHA relieves excessive ECM decomposition in NP cells and provides a potential new idea for the treatment of IVDD in clinical practice.

Exploration of microRNA-106b-5p as a therapeutic target in intervertebral disc degeneration: a preclinical study

MicroRNA (miRNA) has emerge as a vital regulator in the pathogenesis of intervertebral disc degeneration (IDD). However, miR-106b-5p expression in the human nucleus pulposus (NP) and potential mechanisms remain to be elucidated. In this study, the aim was to verify the potential therapeutic mechanisms of miR-106b-5p for IDD. Key miRNAs were screened for in degenerative and normal human intervertebral disc samples. qRT-PCR and fluorescence in situ hybridization (FISH) were used to verify the miR-106b-5p differential expression. The targeting link between miR-106b-5p and Sirtuin 2 (SIRT2) was identified using the luciferase reporter assay and bioinformatics. Flow cytometry, EdU method, and cell scratching were all performed to determine the NP cell function and IDD models were constructed for in vivo experiments. SIRT2, MMP13, ADAMTS5, Col II, Aggrecan, Ras, ERK1/2, and p-ERK1/2 protein levels were assayed by western blotting. Overexpression of miR-106b-5p in NP cells decreased cell growth, induced apoptosis, hindered extracellular matrix formation, and increased the expression of matrix-degrading enzymes through the SIRT2/MAPK/ERK signaling pathway. Importantly, intradiscal delivery of antagomiR-106b-5p significantly attenuated IDD development. Our findings demonstrate that targeting miR-106b-5p in intervertebral disc has therapeutic effects on IDD.

Suppression of matrix degradation and amelioration of disc degeneration by a 970-nm diode laser via inhibition of the p38 MAPK pathway in a rabbit model

Intervertebral disc degeneration (IVDD) mainly manifests as an imbalance between the synthesis and degradation of cellular and extracellular matrix (ECM) components. The cytokine interleukin (IL)-1β-induced inflammatory response of intervertebral discs causes ECM degradation. The aim of this study was to investigate the effects of a 970-nm diode laser therapy (DLT) on inflammatory cytokine IL-1β and ECM degradation proteinases in nucleus pulposus (NP) tissues in a puncture-induced rabbit IVDD model. Thirty-six New Zealand white rabbits were randomly divided into six groups: the normal group, IVDD group, laser group, sham laser group, IVDD + anisomycin (p38MAPK signaling pathway agonist), and laser + anisomycin group. Effects of laser on IVDD progression were detected using radiographic and magnetic resonance imaging. Hematoxylin and eosin, Alcian blue, safranin O-fast green staining, western blotting, and immunohistochemistry staining were performed for the histological analysis and molecular mechanism underlying protection against puncture-induced matrix degradation in NP tissues by DLT. DLT reduced the degree of disc degeneration in the gross anatomy of the disc and increased the T2-weighted signal intensity of NP. Inflammatory cytokine IL-1β levels in the disc were significantly reduced after DLT suppressed the matrix-degrading proteinases MMP13 and ADAMTS-5 and upregulated the protein expression of collagen II and aggrecan. Moreover, it inhibited the p38MAPK signaling pathway in NP tissues in a puncture-induced rabbit IVDD model. DLT reduced puncture-induced overexpression of inflammatory cytokines, mainly IL-1β, thus inhibiting matrix degeneration of NP tissues and ameliorating IVDD. This may be related to inhibition of the p38 MAPK signaling pathway.

Bacteria in human lumbar discs - subclinical infection or contamination? Metabolomic evidence for colonization, multiplication, and cell-cell cross-talk of bacteria

BACKGROUND CONTEXT

The accumulating evidence associating sub-clinical infection with disc degeneration (DD) and the controversy of contamination versus infection mandates a further understanding of the microbial activity in the disc and host-microbiome interaction.

PURPOSE

To utilize a novel approach of metabolomics to probe the presence of bacterial metabolites involved in colonization, survival, and replication in human lumbar intervertebral discs (LIVD).

STUDY DESIGN

An observational case-control study.

PATIENT SAMPLE

Nucleus pulposus from the LIVD of three brain-dead voluntary organ donors (MRI normal and classified as controls) and of three patients undergoing surgery for disc degeneration (DD) (cases) were utilized.

METHODS

Untargeted metabolite profiling was carried out in six discs (3-controls and 3-cases) after extraction using methanol: acetonitrile: water (2:2:1) solvent system and acquired through HPLC-MS/MS platform using C18 reversed-phase column. From the total IVD metabolome, microbial metabolites were filtered by mapping against HMDB, ChEBI, SigMol, Siderophore database, ecdmb database, and PaMet databases. The biological functions of the metabolites were then studied by MSEA pipeline from Metaboanalyst, and the enrichment ratio, p-value, and Variably Importance Projection scores of the metabolites were calculated. Degeneration responsive changes in the abundance of the microbial metabolites were calculated based on the peak intensities between the control and cases.

RESULTS

Mass spectrometry identified a total of 17601 and 15003 metabolites, respectively, in the control and degenerated discs. Preliminary mapping of the above metabolites against HMDB indicated the multiple sources, and of these, 64 metabolites were of microbial origin, accounting for 1.6% of the total IVD metabolome. Principle Component Analysis and Orthogonal Partial Least Square-Discriminant Analysis (OPLS-DA) showed distinct clustered patterns between control and disc degene`ration, indicating a strong variation in concentration, peak, and spectral values of the 64 metabolites between controls and cases. After the exclusion of metabolites that were also associated with humans, drugs, and food, 39 metabolites specific to bacteria were isolated. Nine were primary metabolites related to bacterial growth and survival, and the remaining 30 were secondary metabolites related to different environmental stress response activities. The three significant pathways (p<.001) which were predominant in the bacterial metabolites were autoinducer-2 biosynthesis, peptidoglycan biosynthesis, and chorismate pathway. In addition, a significant fold change of >1.0 was found for nine metabolites which included (S)-14-Methyilhexadecanoic acid related to P. acnes, 9-OxoODE, and 13-OxoODE related to gut flora, vibriobactin - a siderophore, tuberculosinol and iso-tuberculosinol, virulence factors of M. tuberculosis. There was also upregulation of Autoinducer- 2, an important "Quorum sensing molecule" involved in bacterial cross-talk.

CONCLUSION

We identified several bacterial-specific metabolites participating in bacterial growth, survival, and cross-talk pathways. These were found in both groups but up-regulated in degenerated discs. The presence of Quorum sensing molecules and cell-cell interactions provides firm proof of colonization and growth. These findings indicate that the bacterial presence may not be mere contamination but could be colonization with a possible role in infection-mediated inflammation in DD.

CLINICAL SIGNIFICANCE

Proof of subclinical infection as an initiator of DD and documentation of exact germ and drug sensitivity will change the way millions of patients with non-specific low back pain (NSLBP) are treated across the world.

Application of platelet-rich plasma in spinal surgery

With the aging of the population and changes in lifestyle, the incidence of spine-related diseases is increasing, which has become a major global public health problem; this results in a huge economic burden on the family and society. Spinal diseases and complications can lead to loss of motor, sensory, and autonomic functions. Therefore, it is necessary to identify effective treatment strategies. Currently, the treatment of spine-related diseases includes conservative, surgical, and minimally invasive interventional therapies. However, these treatment methods have several drawbacks such as drug tolerance and dependence, adjacent spondylosis, secondary surgery, infection, nerve injury, dural rupture, nonunion, and pseudoarthrosis. Further, it is more challenging to promote the regeneration of the interstitial disc and restore its biomechanical properties. Therefore, clinicians urgently need to identify methods that can limit disease progression or cure diseases at the etiological level. Platelet-rich plasma (PRP), a platelet-rich form of plasma extracted from venous blood, is a blood-derived product. Alpha granules contain a large number of cytokines, such as platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF), epidermal growth factor, platelet factor 4 (PF-4), insulin-like growth factor-1 (IGF-1), and transforming growth factor-β (TGF-β). These growth factors allow stem cell proliferation and angiogenesis, promote bone regeneration, improve the local microenvironment, and enhance tissue regeneration capacity and functional recovery. This review describes the application of PRP in the treatment of spine-related diseases and discusses the clinical application of PRP in spinal surgery.

Application of single and cooperative different delivery systems for the treatment of intervertebral disc degeneration

Intervertebral disc (IVD) degeneration (IDD) is the most universal pathogenesis of low back pain (LBP), a prevalent and costly medical problem across the world. Persistent low back pain can seriously affect a patient's quality of life and even lead to disability. Furthermore, the corresponding medical expenses create a serious economic burden to both individuals and society. Intervertebral disc degeneration is commonly thought to be related to age, injury, obesity, genetic susceptibility, and other risk factors. Nonetheless, its specific pathological process has not been completely elucidated; the current mainstream view considers that this condition arises from the interaction of multiple mechanisms. With the development of medical concepts and technology, clinicians and scientists tend to intervene in the early or middle stages of intervertebral disc degeneration to avoid further aggravation. However, with the aid of modern delivery systems, it is now possible to intervene in the process of intervertebral disc at the cellular and molecular levels. This review aims to provide an overview of the main mechanisms associated with intervertebral disc degeneration and the delivery systems that can help us to improve the efficacy of intervertebral disc degeneration treatment.

Proanthocyanidins inhibit the apoptosis and aging of nucleus pulposus cells through the PI3K/Akt pathway delaying intervertebral disc degeneration

BACKGROUND

Low back pain is a common symptom of intervertebral disc degeneration (IDD), which seriously affects the quality of life of patients. The abnormal apoptosis and senescence of nucleus pulposus (NP) cells play important roles in the pathogenesis of IDD. Proanthocyanidins (PACs) are polyphenolic compounds with anti-apoptosis and anti-aging effects. However, their functions in NP cells are not yet clear. Therefore, this study was performed to explore the effects of PACs on NP cell apoptosis and aging and the underlying mechanisms of action.

METHODS

Cell viability was evaluated by cell counting kit-8 (CCK-8) assay. The apoptosis rate was determined TUNEL assays. Levels of apoptosis-associated molecules (Bcl-2, Bax, C-caspase-3 and Caspase-9) were evaluated via western blot. The senescence was observed through SA-β-gal staining and western blotting analysis was performed to observe the expression of senescence-related molecules (p-P53, P53, P21 and P16).

RESULTS

Pretreatment with PACs exhibited protective effects against IL-1β-induced NP cell apoptosis including apoptosis rate, expressions of proapoptosis and antiapoptosis related genes and protein. PACs could also alleviate the increase of p-p53, P21, and P16 in IL-1β-treated NP cells. SA-β-gal staining showed that IL-1β-induced senescence of NP cells was prevented by PACs pertreatment. In addition, PACs activated PI3K/Akt pathway in IL-1β-stimulated NP cells. However, these protected effects were inhibited after LY294002 treatment.

CONCLUSION

The results of the present study showed that PACs inhibit IL-1β-induced apoptosis and aging of NP cells by activating the PI3K/Akt pathway, and suggested that PACs have therapeutic potential for IDD.

The Nrf2 antioxidant defense system in intervertebral disc degeneration: Molecular insights

Intervertebral disc degeneration (IDD) is a common degenerative musculoskeletal disorder and is recognized as a major contributor to discogenic lower back pain. However, the molecular mechanisms underlying IDD remain unclear, and therapeutic strategies for IDD are currently limited. Oxidative stress plays pivotal roles in the pathogenesis and progression of many age-related diseases in humans, including IDD. Nuclear factor E2-related factor 2 (Nrf2) is a master antioxidant transcription factor that protects cells against oxidative stress damage. Nrf2 is negatively modulated by Kelch-like ECH-associated protein 1 (Keap1) and exerts important effects on IDD progression. Accumulating evidence has revealed that Nrf2 can facilitate the transcription of downstream antioxidant genes in disc cells by binding to antioxidant response elements (AREs) in promoter regions, including heme oxygenase-1 (HO-1), glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), and NADPH quinone dehydrogenase 1 (NQO1). The Nrf2 antioxidant defense system regulates cell apoptosis, senescence, extracellular matrix (ECM) metabolism, the inflammatory response of the nucleus pulposus (NP), and calcification of the cartilaginous endplates (EP) in IDD. In this review, we aim to discuss the current knowledge on the roles of Nrf2 in IDD systematically.

Insights into the activity of a protein that regulates gene expression and protects cells against oxidative stress could yield novel treatments for lower back pain. Intervertebral disc degeneration (IDD) is a common cause of lower back pain, but the molecular mechanisms underlying IDD are unclear, meaning treatment options are limited. Oxidative stress is implicated in IDD, and scientists have begun exploring the role of nuclear factor E2-related factor 2 (Nrf2), a master regulator of the body’s antioxidant responses, in regulating IDD progression. In a review of recent research, Weishi Li at Peking University Third Hospital, Beijing, China, and co-workers point out that boosting the activity of Nrf2-related signaling pathways alleviates oxidative stress in intervertebral disc cells. The researchers suggest that therapies based on non-coding RNAs may prove valuable in activating Nrf2 in IDD patients.

Hyperoside ameliorates TNF‑α‑induced inflammation, ECM degradation and ER stress‑mediated apoptosis via the SIRT1/NF‑κB and Nrf2/ARE signaling pathways in vitro

Intervertebral disc degeneration (IDD) is the main pathogenesis of numerous cases of chronic neck and back pain, and has become the leading cause of spinal-related disability worldwide. Hyperoside is an active flavonoid glycoside that exhibits anti-inflammation, anti-oxidation and anti-apoptosis effects. The purpose of the present study was to investigate the effect of hyperoside on tumor necrosis factor (TNF)-α-induced IDD progression in human nucleus pulposus cells (NPCs) and its potential mechanism. The activity and apoptosis of NPCs were detected by Cell Counting Kit-8 and flow cytometry analyses, respectively. The expression of interleukin (IL)-6 and IL-1β was detected with ELISA kits. Western blotting was used to detect the expression levels of proteins. The results showed that hyperoside effectively alleviated TNF-α-induced NPC apoptosis, and hyperoside treatment inhibited the upregulation of inducible nitric oxide synthase, cyclooxygenase-2, IL-1β and IL-6 in TNF-α-stimulated NPCs. Compared with the findings in the TNF-α group, the intervention of hyperoside attenuated the upregulated expression of aggrecan and collagen II, and downregulated the expressions of matrix metalloproteinase (MMP) 3, MMP13 and a disintegrin and metalloproteinase with thrombospondin motifs 5. In addition, hyperoside upregulated sirtuin-1 (SIRT1) and nuclear factor E2-related factor 2 (Nrf2) protein expression, and inhibition of SIRT1 or Nrf2 signaling reversed the protective effect of hyperoside on TNF-α-induced NPCs. In summary, hyperoside ameliorated TNF-α-induced inflammation, extracellular matrix degradation, and endoplasmic reticulum stress-mediated apoptosis, which may be associated with the regulation of the SIRT1/NF-κB and Nrf2/antioxidant responsive element signaling pathways by hyperoside.

Key LncRNAs Associated With Oxidative Stress Were Identified by GEO Database Data and Whole Blood Analysis of Intervertebral Disc Degeneration Patients

Background: Intervertebral disc degeneration (IDD) is a major cause of low back pain, but the onset and progression of IDD are unknown. Long non-coding RNA (lncRNA) has been validated to play a critical role in IDD, while an increasing number of studies have linked oxidative stress (OS) to the initiation and progression of IDD. We aim to investigate key lncRNAs in IDD through a comprehensive network of competing endogenous RNA (ceRNA) and to identify possible underlying mechanisms.

Methods: We downloaded IDD-related gene expression data from the Gene Expression Omnibus (GEO) database and obtained differentially expressed-lncRNAs (DE-lncRNA), -microRNAs (DE-miRNA), and -messenger RNAs (DE-mRNA) by bioinformatics analysis. The OS-related lncRNA-miRNA-mRNA ceRNA interaction axis was constructed and key lncRNAs were identified based on ceRNA theory. We performed gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses on mRNAs regulated by lncRNAs in the ceRNA network. Single sample gene set enrichment analysis (ssGSEA) was used to reveal the immune landscape. Expression of key lncRNAs in IDD was assessed by quantitative reverse transcription-polymerase chain reaction (qRT-PCR).

Results: In this study, 111 DE-mRNAs, 20 DE-lncRNAs, and 502 DE-miRNAs were identified between IDD patients and controls, and 16 OS-related DE-lncRNAs were also identified. The resulting lncRNA-miRNA-mRNA network consisted of eight OS-related DE-lncRNA nodes, 24 DE-miRNA nodes, 70 DE-mRNA nodes, and 183 edges. Functional enrichment analysis suggested that the ceRNA network may be involved in regulating biological processes related to cytokine secretion, lipid, and angiogenesis. We also identified four key lncRNAs, namely lncRNA GNAS-AS1, lncRNA MIR100HG, lncRNA LINC01359, and lncRNA LUCAT1, which were also found to be significantly associated with immune cells.

Conclusion: These results provide novel insights into the potential applications of OS-related lncRNAs in patients with IDD.

Irisin Ameliorates Intervertebral Disc Degeneration by Activating LATS/YAP/CTGF Signaling

Unbalanced metabolism of an extracellular matrix (ECM) in nucleus pulposus cells (NPCs) is widely acknowledged as the primary cause of intervertebral disc degeneration (IDD). Irisin, a novel myokine, is cleaved from fibronectin type III domain-containing 5 (FNDC5) and has recently been proven to regulate the metabolism of ECM. However, little is known about its potential on NPCs and the development of IDD. Therefore, this study sought to examine the protective effects and molecular mechanism of irisin on IDD in vivo and in vitro. Decreased expression levels of FNDC5 and anabolism markers (COL2A1 and ACAN) but increased levels of catabolism markers (ADAMTS4) were found in degenerative nucleus pulposus (NP) tissues. In a punctured-induced rat IDD model, irisin treatment was found to significantly slow the development of IDD, and in TNF-α-stimulated NPCs, irisin treatment partly reversed the disorder of ECM metabolism. In mechanism, RNA-seq results suggested that irisin treatment affected the Hippo signaling pathway. Further studies revealed that with irisin treatment, the phosphorylation levels of key factors (LATS and YAP) were downregulated, while the expression level of CTGF was upregulated. Moreover, CTGF knockdown partially eliminated the protective effects of irisin on the metabolism of ECM in NPCs, including inhibiting the anabolism and promoting the catabolism. Taken together, this study demonstrated that the expression levels of FNDC5 were decreased in degenerative NP tissues, while irisin treatment promoted the anabolism, inhibited the catabolism of the ECM in NPCs, and delayed the progression of IDD via LATS/YAP/CTGF signaling. These results shed light on the protective actions of irisin on NPCs, leading to the development of a novel therapeutic target for treating IDD.

Importance of Matrix Cues on Intervertebral Disc Development, Degeneration, and Regeneration

Back pain is one of the leading causes of disability worldwide and is frequently caused by degeneration of the intervertebral discs. The discs’ development, homeostasis, and degeneration are driven by a complex series of biochemical and physical extracellular matrix cues produced by and transmitted to native cells. Thus, understanding the roles of different cues is essential for designing effective cellular and regenerative therapies. Omics technologies have helped identify many new matrix cues; however, comparatively few matrix molecules have thus far been incorporated into tissue engineered models. These include collagen type I and type II, laminins, glycosaminoglycans, and their biomimetic analogues. Modern biofabrication techniques, such as 3D bioprinting, are also enabling the spatial patterning of matrix molecules and growth factors to direct regional effects. These techniques should now be applied to biochemically, physically, and structurally relevant disc models incorporating disc and stem cells to investigate the drivers of healthy cell phenotype and differentiation. Such research will inform the development of efficacious regenerative therapies and improved clinical outcomes.

Curcumenol Mitigates the Inflammation and Ameliorates the Catabolism Status of the Intervertebral Discs In Vivo and In Vitro via Inhibiting the TNFα/NFκB Pathway

Low back pain (LBP) caused by intervertebral disc degeneration (IVDD) is accredited to the release of inflammatory cytokines followed by biomechanical and structural deterioration. In our study, we used a plant-derived medicine, curcumenol, to treat IVDD. A cell viability test was carried out to evaluate the possibility of using curcumenol. RNA-seq was used to determine relative pathways involved with curcumenol addition. Using TNFα as a trigger of inflammation, the activation of the NF-κB signaling pathway and expression of the MMP family were determined by qPCR and western blotting. Nucleus pulposus (NP) cells and the rats’ primary NP cells were cultured. The catabolism status was evaluated by an ex vivo model. A lumbar instability mouse model was carried out to show the effects of curcumenol in vivo. In general, RNA-seq revealed that multiple signaling pathways changed with curcumenol addition, especially the TNFα/NF-κB pathway. So, the NP cells and primary NP cells were induced to suffer inflammation with the activated TNFα/NF-κB signaling pathway and increased expression of the MMP family, such as MMP3, MMP9, and MMP13, which would be mitigated by curcumenol. Owing to the protective effects of curcumenol, the height loss and osteophyte formation of the disc could be prevented in the lumbar instability mouse model in vivo.

Ultrashort time-to-echo T2* and T2* relaxometry for evaluation of lumbar disc degeneration: a comparative study

Background

To compare potential of ultrashort time-to-echo (UTE) T2* mapping and T2* values from T2*-weighted imaging for assessing lumbar intervertebral disc degeneration (IVDD),with Pfirrmann grading as a reference standard.

Methods

UTE-T2* and T2* values of 366 lumbar discs (L1/2-L5/S1) in 76 subjects were measured in 3 segmented regions: anterior annulus fibrosus, nucleus pulposus (NP), and posterior annulus fibrosus. Lumbar intervertebral discs were divided into 3 categories based on 5-level Pfirrmann grading: normal (Pfirrmann grade I),early disc degeneration (Pfirrmann grades II-III), and advanced disc degeneration (Pfirrmann grades IV-V). Regional differences between UTE-T2* and T2* relaxometry and correlation with degeneration were statistically analyzed.

Results

UTE-T2* and T2*value correlated negatively with Pfirrmann grades (P < 0.001). In NP, correlations with Pfirrmann grade were high with UTE-T2* values (r =  − 0.733; P < 0.001) and moderate with T2* values (r = -0.654; P < 0.001). Diagnostic accuracy of detecting early IVDD was better with UTE-T2* mapping than T2* mapping (P < 0.05),with receiver operating characteristic analysis area under the curve of 0.715–0.876.

Conclusions

UTE-T2* relaxometry provides another promising magnetic resonance imaging sequence for quantitatively evaluate lumbar IVDD and was more accurate than T2*mapping in the earlier stage degenerative process.

Intradiscal injection for the management of low back pain

Low back pain (LBP) is a common clinical problem and a major cause of physical disability, imposing a prominent socioeconomic burden. Intervertebral disc degeneration (IDD) has been considered the main cause of LBP. The current treatments have limited efficacy because they cannot address the underlying degeneration. With an increased understanding of the complex pathological mechanism of IDD, various medications and biological reagents have been used for intradiscal injection for the treatment of LBP. There is increasing clinical evidence showing the benefits of these therapies on symptomatic relief and their potential for disc repair and regeneration by targeting the disrupted pathways underlying the cause of the disease. A brief overview of the potential and limitations for these therapies are provided in this review, based on the recent and available data from clinical trials and systematic reviews. Finally, future perspectives are discussed.

Spheroid-Based Tissue Engineering Strategies for Regeneration of the Intervertebral Disc

Degenerative disc disease, a painful pathology of the intervertebral disc (IVD), often causes disability and reduces quality of life. Although regenerative cell-based strategies have shown promise in clinical trials, none have been widely adopted clinically. Recent developments demonstrated that spheroid-based approaches might help overcome challenges associated with cell-based IVD therapies. Spheroids are three-dimensional multicellular aggregates with architecture that enables the cells to differentiate and synthesize endogenous ECM, promotes cell-ECM interactions, enhances adhesion, and protects cells from harsh conditions. Spheroids could be applied in the IVD both in scaffold-free and scaffold-based configurations, possibly providing advantages over cell suspensions. This review highlights areas of future research in spheroid-based regeneration of nucleus pulposus (NP) and annulus fibrosus (AF). We also discuss cell sources and methods for spheroid fabrication and characterization, mechanisms related to spheroid fusion, as well as enhancement of spheroid performance in the context of the IVD microenvironment.

Circular RNA hsa_circ_0083756 promotes intervertebral disc degeneration by sponging miR-558 and regulating TREM1 expression

Objectives

Intervertebral disc degeneration (IVDD) is a leading cause of low back pain. Circular RNAs (circRNAs) have been demonstrated to exert vital functions in IVDD. However, the role and mechanism of hsa_circ_0083756 in the development of IVDD remain unclear.

Materials and methods

RT‐qPCR was performed to detect expressions of hsa_circ_0083756, miR‐558 and TREM1 in nucleus pulposus (NP) tissues and cells. CCK8 assay, flow cytometry, TUNEL assay, RT‐qPCR and WB were used to clarify the roles of hsa_circ_0083756 in NP cells proliferation and extracellular matrix (ECM) formation. Bioinformatics analyses, dual‐luciferase reporter gene experiment, RNA immunoprecipitation (RIP) assay and FISH assay were performed to predict and verify the targeting relationship between hsa_circ_0083756 and miR‐558, as well as that between miR‐558 and TREM1. Ultimately, the effect of hsa_circ_0083756 on IVDD was tested through anterior disc‐puncture IVDD animal model in rats.

Results

hsa_circ_0083756 was upregulated in degenerative NP tissues and cells. In vitro loss‐of‐function and gain‐of‐function studies suggested that hsa_circ_0083756 knockdown promoted, whereas hsa_circ_0083756 overexpression inhibited NP cells proliferation and ECM formation. Mechanistically, hsa_circ_0083756 acted as a sponge of miR‐558 and subsequently promoted the expression of TREM1. Furthermore, in vivo study indicated that silencing of hsa_circ_0083756 could alleviate IVDD in rats.

Conclusions

hsa_circ_0083756 promoted IVDD via targeting the miR‐558/TREM1 axis, and hsa_circ_0083756 may serve as a potential therapeutic target for the treatment of IVDD.

Tetrandrine reduces oxidative stress, apoptosis, and extracellular matrix degradation and improves intervertebral disc degeneration by inducing autophagy

Tetrandrine (TET) was reported to be an autophagy agonist, and the activating autophagy could delay intervertebral disc degeneration (IDD). Our study focused on exploring whether TET attenuated tert butyl hydrogen peroxide (TBHP)-induced nucleus pulposus (NP) cell injury and delayed rat IDD by inducing autophagy. In vitro, cytotoxicity was detected by MTT assay, ROS was measured with DCFH-DA probe, MDA, and SOD content was evaluated through ELISA, NP cell apoptosis was tested by flow cytometry, protein expression was detected by Western blot, in particular, LC3 expression was assessed by immunofluorescence. In vivo, pathological changes were estimated by HE and safranin-O staining, related protein expression was measured by immunohistochemistry, and the apoptosis was detected by TUNEL. Compared with the control group, oxidative stress, apoptosis, and extracellular matrix (ECM) degradation were increased, the expression of cleaved caspase-3,9, aggrecan and collagen II were reduced, and the expression of MMP13 and ADAMTS5 were up-regulated in TBHP-treated NP cells. Moreover, TET could reverse the effect of TBHP on NP cells. Further, TET enhanced autophagy in NP cells by amplifying the LC3 II/LC3 I/ratio and reducing p62 expression, which attenuated oxidative stress, apoptosis, and ECM degradation in TBHP-treated NP cells. In addition, in vivo, TET delayed rat IDD, increased the expression of LC3 and collagen II, and weakened apoptosis. TET inhibited oxidative stress, apoptosis, and ECM degradation in TBHP-treated NP cells by inducing autophagy, and alleviated IDD. These indicated that TET might be a potential candidate drug for the treatment of IDD.

High hydrostatic pressure (30 atm) enhances the apoptosis and inhibits the proteoglycan synthesis and extracellular matrix level of human nucleus pulposus cells via promoting the Wnt/β-catenin pathway

Hydrostatic pressure is known to regulate bovine nucleus pulposus cell metabolism, but its mechanism in human nucleus pulposus cells (HNPCs) remains obscure, which attracts our attention and becomes the focus in this study. Specifically, HNPCs were treated with SKL2001 (an agonist in the Wnt/β-catenin pathway) or XAV-939 (an inhibitor of the Wnt/β-catenin pathway), and pressurized under the hydrostatic pressure of 1, 3 and 30 atm. The viability, apoptosis and proteoglycan synthesis of treated HNPC were assessed by CCK-8, flow cytometry and radioisotope incorporation assays. The levels of extracellular matrix, Collagen-II, matrix metalloproteinase 3 (MMP3), Wnt-3a and β-catenin were measured by toluidine blue staining, immunocytochemistry and Western blot. Appropriate hydrostatic stimulation (3 atm) enhanced the viability and proteoglycan synthesis yet inhibited the apoptosis of HNPCs, which also up-regulated extracellular matrix and Collagen-II levels, and down-regulated MMP3, Wnt-3a and β-catenin levels in treated HNPCs. Furthermore, high hydrostatic pressure (30 atm) inhibited the viability and proteoglycan synthesis, and promoted the morphological change and apoptosis of HNPCs, which also down-regulated extracellular matrix and Collagen-II levels and up-regulated MMP3, Wnt-3a and β-catenin levels. Besides, SKL2001 reversed the effects of hydrostatic pressure (3 atm) on inhibiting Wnt-3a, β-catenin, and MMP3 levels and promoting Collagen-II level in HNPC; whereas, XAV-939 reversed the effects of high hydrostatic pressure (30 atm) on promoting MMP3, Wnt-3a, and β-catenin levels and inhibiting Collagen-II level and proteoglycan synthesis of HNPCs. Collectively, high hydrostatic pressure promoted the apoptosis and inhibited the viability of HNPCs via activating the Wnt/β-catenin pathway.

Advances and Prospects in Biomaterials for Intervertebral Disk Regeneration

Low-back and neck-shoulder pains caused by intervertebral disk degeneration are highly prevalent among middle-aged and elderly people globally. The main therapy method for intervertebral disk degeneration is surgical intervention, including interbody fusion, disk replacement, and diskectomy. However, the stress changes caused by traditional fusion surgery are prone to degeneration of adjacent segments, while non-fusion surgery has problems, such as ossification of artificial intervertebral disks. To overcome these drawbacks, biomaterials that could endogenously regenerate the intervertebral disk and restore the biomechanical function of the intervertebral disk is imperative. Intervertebral disk is a fibrocartilaginous tissue, primarily comprising nucleus pulposus and annulus fibrosus. Nucleus pulposus (NP) contains high water and proteoglycan, and its main function is absorbing compressive forces and dispersing loads from physical activities to other body parts. Annulus fibrosus (AF) is a multilamellar structure that encloses the NP, comprises water and collagen, and supports compressive and shear stress during complex motion. Therefore, different biomaterials and tissue engineering strategies are required for the functional recovery of NP and AF based on their structures and function. Recently, great progress has been achieved on biomaterials for NP and AF made of functional polymers, such as chitosan, collagen, polylactic acid, and polycaprolactone. However, scaffolds regenerating intervertebral disk remain unexplored. Hence, several tissue engineering strategies based on cell transplantation and growth factors have been extensively researched. In this review, we summarized the functional polymers and tissue engineering strategies of NP and AF to endogenously regenerate degenerative intervertebral disk. The perspective and challenges of tissue engineering strategies using functional polymers, cell transplantation, and growth factor for generating degenerative intervertebral disks were also discussed.

An Oxidative Stress-Related Gene Pair (CCNB1/PKD1), Competitive Endogenous RNAs, and Immune-Infiltration Patterns Potentially Regulate Intervertebral Disc Degeneration Development

Oxidative stress (OS) irreversibly affects the pathogenesis of intervertebral disc degeneration (IDD). Certain non-coding RNAs act as competitive endogenous RNAs (ceRNAs) that regulate IDD progression. Analyzing the signatures of oxidative stress-related gene (OSRG) pairs and regulatory ceRNA mechanisms and immune-infiltration patterns associated with IDD may enable researchers to distinguish IDD and reveal the underlying mechanisms. In this study, OSRGs were downloaded and identified using the Gene Expression Omnibus database. Functional-enrichment analysis revealed the involvement of oxidative stress-related pathways and processes, and a ceRNA network was generated. Differentially expressed oxidative stress-related genes (De-OSRGs) were used to construct De-OSRG pairs, which were screened, and candidate De-OSRG pairs were identified. Immune cell-related gene pairs were selected via immune-infiltration analysis. A potential long non-coding RNA-microRNA-mRNA axis was determined, and clinical values were assessed. Eighteen De-OSRGs were identified that were primarily related to intricate signal-transduction pathways, apoptosis-related biological processes, and multiple kinase-related molecular functions. A ceRNA network consisting of 653 long non-coding RNA-microRNA links and 42 mRNA-miRNA links was constructed. Three candidate De-OSRG pairs were screened out from 13 De-OSRG pairs. The abundances of resting memory CD4+ T cells, resting dendritic cells, and CD8+ T cells differed between the control and IDD groups. CD8+ T cell infiltration correlated negatively with cyclin B1 (CCNB1) expression and positively with protein kinase D1 (PKD1) expression. CCNB1-PKD1 was the only pair that was differentially expressed in IDD, was correlated with CD8+ T cells, and displayed better predictive accuracy compared to individual genes. The PKD1-miR-20b-5p-AP000797 and CCNB1-miR-212-3p-AC079834 axes may regulate IDD. Our findings indicate that the OSRG pair CCNB1-PKD1, which regulates oxidative stress during IDD development, is a robust signature for identifying IDD. This OSRG pair and increased infiltration of CD8+ T cells, which play important roles in IDD, were functionally associated. Thus, the OSRG pair CCNB1-PKD1 is promising target for treating IDD.

Advances in Tissue Engineering for Disc Repair

Intervertebral disc (IVD) degeneration is a leading cause of chronic low back pain (LBP) that results in serious disability and significant economic burden. IVD degeneration alters the disc structure and spine biomechanics, resulting in subsequent structural changes throughout the spine. Currently, treatments of chronic LBP due to IVD degeneration include conservative treatments, such as pain medication and physiotherapy, and surgical treatments, such as removal of herniated disc without or with spinal fusion. However, none of these treatments can completely restore a degenerated disc and its function. Thus, although the exact pathogenesis of disc degeneration remains unclear, there are studies examining the effectiveness of biological approaches, such as growth factor injection, gene therapy, and cell transplantation, in promoting IVD regeneration. Furthermore, tissue engineering using a combination of cell transplantation and biomaterials has emerged as a promising new approach for repair or restoration of degenerated discs. The main purpose of this review was to provide an overview of the current status of tissue engineering applications for IVD regenerative therapy by performing literature searches using PubMed. Significant advances in tissue engineering have opened the door to a new generation of regenerative therapies for the treatment of chronic discogenic LBP.