Treatment of Intervertebral Disc Degeneration

Unlocking the potential of exosomes: a breakthrough in the theranosis of degenerative orthopaedic diseases

Degenerative orthopaedic diseases pose a notable worldwide public health issue attributable to the global aging population. Conventional medical approaches, encompassing physical therapy, pharmaceutical interventions, and surgical methods, face obstacles in halting or reversing the degenerative process. In recent times, exosome-based therapy has gained widespread acceptance and popularity as an effective treatment for degenerative orthopaedic diseases. This therapeutic approach holds the potential for "cell-free" tissue regeneration. Exosomes, membranous vesicles resulting from the fusion of intracellular multivesicles with the cell membrane, are released into the extracellular matrix. Addressing challenges such as the rapid elimination of natural exosomes in vivo and the limitation of drug concentration can be effectively achieved through various strategies, including engineering modification, gene overexpression modification, and biomaterial binding. This review provides a concise overview of the source, classification, and preparation methods of exosomes, followed by an in-depth analysis of their functions and potential applications. Furthermore, the review explores various strategies for utilizing exosomes in the treatment of degenerative orthopaedic diseases, encompassing engineering modification, gene overexpression, and biomaterial binding. The primary objective is to provide a fresh viewpoint on the utilization of exosomes in addressing bone degenerative conditions and to support the practical application of exosomes in the theranosis of degenerative orthopaedic diseases.

Evodiamine ameliorates intervertebral disc degeneration through the Nrf2 and MAPK pathways

Degradation of extracellular matrix (ECM), reactive oxygen species (ROS) production, and inflammation are critical players in the pathogenesis of intervertebral disc degeneration (IDD). Evodiamine exerts functions in inhibiting inflammation and maintaining mitochondrial antioxidant functions. However, the biological functions of evodiamine and its related mechanisms in IDD progression remain unknown. The IDD-like conditions in vivo were stimulated via needle puncture. Hematoxylin and eosin staining, Safranin O/Fast Green staining and Alcian staining were performed to determine the degenerative status. The primary nucleus pulposus cells (NPCs) were isolated from Sprague-Dawley rats and then treated with tert-butyl peroxide (TBHP) to induce cellular senescence and oxidative stress. The cell viability was assessed by cell counting kit-8 assays. The mitochondria-derived ROS in NPCs was evaluated by MitoSOX staining. The mitochondrial membrane potential in NPCs was identified by JC-1 staining and flow cytometry. The expression of collagen II in NPCs was measured by immunofluorescence staining. The levels of mRNAs and proteins were measured by RT-qPCR and western blotting. The Nrf2 expression in rat nucleus pulposus tissues was measured by immunohistochemistry staining. Evodiamine alleviated TBHP-induced mitochondrial dysfunctions in NPCs. The enhancing effect of TBHP on the ECM degradation was reversed by evodiamine. The TBHP-stimulated inflammatory response was ameliorated by evodiamine. Evodiamine alleviated the IDD process in the puncture-induced rat model. Evodiamine promoted the activation of Nrf2 pathway and inactivated the MAPK pathway in NPCs. In conclusion, evodiamine ameliorates the progression of IDD by inhibiting mitochondrial dysfunctions, ECM degradation and inflammation via the Nrf2/HO-1 and MAPK pathways.

Regulatory mechanism of FCGR2A in macrophage polarization and its effects on intervertebral disc degeneration

Intervertebral disc degeneration (IDD) poses a significant health burden, necessitating a deeper understanding of its molecular underpinnings. Transcriptomic analysis reveals 485 differentially expressed genes (DEGs) associated with IDD, underscoring the importance of immune regulation. Weighted gene co-expression network analysis (WGCNA) identifies a yellow module strongly correlated with IDD, intersecting with 197 DEGs. Protein-protein interaction (PPI) analysis identifies ITGAX, MMP9 and FCGR2A as hub genes, predominantly expressed in macrophages. Functional validation through in vitro and in vivo experiments demonstrates the pivotal role of FCGR2A in macrophage polarization and IDD progression. Mechanistically, FCGR2A knockdown suppresses M1 macrophage polarization and NF-κB phosphorylation while enhancing M2 polarization and STAT3 activation, leading to ameliorated IDD in animal models. This study sheds light on the regulatory function of FCGR2A in macrophage polarization, offering novel insights for IDD intervention strategies. KEY POINTS: This study unveils the role of FCGR2A in intervertebral disc (IVD) degeneration (IDD). FCGR2A knockdown mitigates IDD in cellular and animal models. Single-cell RNA-sequencing uncovers diverse macrophage subpopulations in degenerated IVDs. This study reveals the molecular mechanism of FCGR2A in regulating macrophage polarization. This study confirms the role of the NF-κB/STAT3 pathway in regulating macrophage polarization in IDD.

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.

Causal associations between gut microbiota with intervertebral disk degeneration, low back pain, and sciatica: a Mendelian randomization study

PURPOSE

Although studies have suggested that gut microbiota may be associated with intervertebral disk disease, their causal relationship is unclear. This study aimed to investigate the causal relationship between the gut microbiota and its metabolic pathways with the risk of intervertebral disk degeneration (IVDD), low back pain (LBP), and sciatica.

METHODS

Genetic variation data for 211 gut microbiota taxa at the phylum to genus level were obtained from the MiBioGen consortium. Genetic variation data for 105 taxa at the species level and 205 metabolic pathways were obtained from the Dutch Microbiome Project. Genetic variation data for disease outcomes were obtained from the FinnGen consortium. The causal relationships between the gut microbiota and its metabolic pathways and the risk of IVDD, LBP, and sciatica were evaluated via Mendelian randomization (MR). The robustness of the results was assessed through sensitivity analysis.

RESULTS

Inverse variance weighting identified 46 taxa and 33 metabolic pathways that were causally related to IVDD, LBP, and sciatica. After correction by weighted median and MR-PRESSO, 15 taxa and nine pathways remained stable. After FDR correction, only the effect of the genus_Eubacterium coprostanoligenes group on IVDD remained stable. Sensitivity analyses showed no evidence of horizontal pleiotropy, heterogeneity, or reverse causation.

CONCLUSION

Some microbial taxa and their metabolic pathways are causally related to IVDD, LBP, and sciatica and may serve as potential intervention targets. This study provides new insights into the mechanisms of gut microbiota-mediated development of intervertebral disk disease.

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.

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

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

Bioinformatics-based discovery of intervertebral disc degeneration biomarkers and immune-inflammatory infiltrates

Background

Intervertebral disc degeneration (IVDD) is a common chronic disease in orthopedics, and its molecular mechanisms are still not well explained.

Aim

This study's objective was to bioinformatics-based discovery of IVDD biomarkers and immune-inflammatory infiltrates.

Materials and Methods

The IVDD illness gene collection was gathered from GeneCards, DisGeNet, and gene expression profiles were chosen from the extensive Gene Expression Omnibus database (GSE124272, GSE150408, and GSE153761). The STRING database was used to create a network of protein-protein interactions, while the Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) databases were used for functional enrichment analysis. Using hub genes, the immune cell infiltration between IVDD patient samples and control tissues was examined. Finally, quantitative polymerase chain reaction and Western blot experiments were used to verify the expression of hub genes.

Results

A total of 27 differentially expressed hub genes were identified by bioinformatics. According to GO and KEGG analyses, hub genes were prominent in immunological responses, chemokine-mediated signaling pathways, and inflammatory responses, with the key signaling pathways engaged in cellular senescence, apoptosis, Th1 and Th2 cell differentiation, and Th17 cell differentiation. Immune cell infiltration research revealed that T cells, lymphocytes, B cells, and NK cells were decreased in IVDD patients while monocytes, neutrophils, and CD8 T cells were increased. The expression levels of the senescence hub genes SP1, VEGFA, IL-6, and the apoptosis key gene CASP3 were considerably greater in the IVDD model group than in the control group, according to in vitro validation.

Conclusion

In conclusion, the cellular senescence signaling pathway, the apoptosis signaling pathway, and associated hub genes play significant roles in the development and progression of IVDD, this finding may help direct future research on the senescence signaling route in 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.

Involvement of DJ-1 in the pathogenesis of intervertebral disc degeneration via hexokinase 2-mediated mitophagy

Intervertebral disc degeneration (IDD) is an important pathological basis for degenerative spinal diseases and is involved in mitophagy dysfunction. However, the molecular mechanisms underlying mitophagy regulation in IDD remain unclear. This study aimed to clarify the role of DJ-1 in regulating mitophagy during IDD pathogenesis. Here, we showed that the mitochondrial localization of DJ-1 in nucleus pulposus cells (NPCs) first increased and then decreased in response to oxidative stress. Subsequently, loss- and gain-of-function experiments revealed that overexpression of DJ-1 in NPCs inhibited oxidative stress-induced mitochondrial dysfunction and mitochondria-dependent apoptosis, whereas knockdown of DJ-1 had the opposite effect. Mechanistically, mitochondrial translocation of DJ-1 promoted the recruitment of hexokinase 2 (HK2) to damaged mitochondria by activating Akt and subsequently Parkin-dependent mitophagy to inhibit oxidative stress-induced apoptosis in NPCs. However, silencing Parkin, reducing mitochondrial recruitment of HK2, or inhibiting Akt activation suppressed DJ-1-mediated mitophagy. Furthermore, overexpression of DJ-1 ameliorated IDD in rats through HK2-mediated mitophagy. Taken together, these findings indicate that DJ-1 promotes HK2-mediated mitophagy under oxidative stress conditions to inhibit mitochondria-dependent apoptosis in NPCs and could be a therapeutic target for IDD.

Reviving Intervertebral Discs: Treating Degeneration Using Advanced Delivery Systems

Intervertebral disc degeneration (IVDD) is commonly associated with many spinal problems, such as low back pain, and significantly impacts a patient's quality of life. However, current treatments for IVDD, which include conservative and surgical methods, are limited in their ability to fully address degeneration. To combat IVDD, delivery-system-based therapy has received extensive attention from researchers. These delivery systems can effectively deliver therapeutic agents for IVDD, overcoming the limitations of these agents, reducing leakage and increasing local concentration to inhibit IVDD or promote intervertebral disc (IVD) regeneration. This review first briefly introduces the structure and function of the IVD, and the related pathophysiology of IVDD. Subsequently, the roles of drug-based and bioactive-substance-based delivery systems in IVDD are highlighted. The former includes natural source drugs, nonsteroidal anti-inflammatory drugs, steroid medications, and other small molecular drugs. The latter includes chemokines, growth factors, interleukin, and platelet-rich plasma. Additionally, gene-based and cell-based delivery systems are briefly involved. Finally, the limitations and future development of the combination of therapeutic agents and delivery systems in the treatment of IVDD are discussed, providing insights for future research.

Therapeutic effect and mechanism of Yougui Wan in rats with intervertebral disk degeneration

OBJECTIVE

To explore the potential mechanism of Yougui Wan on deformed lumbar intervertebral disk structure in rats.

METHODS

Thirty male Sprague-Dawley rats were randomly divided into 3 groups, with 10 rats in each group. The animals in the blank control group were healthy rats without specific treatment, and those in the model group and traditional Chinese medicine (TCM) group were used to establish the intervertebral disk degeneration (IDD) model by puncturing the annulus. Four weeks after modeling, rats in the TCM group were administered Yougui Wan by gavage for 2 consecutive weeks. Serum interleukin-6 (IL-10), macrophage migration inhibitory factor (MIF) and tumor necrosis factor alpha (TNF-α) levels were measured by ELISA, and the protein expression levels of collagen II and Notch1 in intervertebral disk tissues were examined by Western blotting. Apoptosis was detected by the TUNEL method.

RESULTS

Compared with those in the blank group, IL-10, MIF and TNF-α levels in the model group and TCM group were increased (P < 0.05), the protein expression levels of collagen II were decreased, and the protein expression levels of Notch1 were increased. Compared with those in the model group, the levels of IL-10 in the TCM group were increased (P < 0.05), the levels of MIF and TNF-α were decreased (P < 0.05), the protein expression levels of collagen II were increased, and the protein expression levels of Notch1 were decreased.

CONCLUSION

Yougui Wan can inhibit the inflammatory response in IDD rats, reduce the degradation of extracellular matrix, reduce apoptosis in nucleus pulposus cells, and alleviate intervertebral disk degeneration. The mechanism may be related to the regulation of the Notch signaling pathway.

Hydrogel-Based Strategies for Intervertebral Disc Regeneration: Advances, Challenges and Clinical Prospects

Millions of people worldwide suffer from low back pain and disability associated with intervertebral disc (IVD) degeneration. IVD degeneration is highly correlated with aging, as the nucleus pulposus (NP) dehydrates and the annulus fibrosus (AF) fissures form, which often results in intervertebral disc herniation or disc space collapse and related clinical symptoms. Currently available options for treating intervertebral disc degeneration are symptoms control with therapy modalities, and/or medication, and/or surgical resection of the IVD with or without spinal fusion. As such, there is an urgent clinical demand for more effective disease-modifying treatments for this ubiquitous disorder, rather than the current paradigms focused only on symptom control. Hydrogels are unique biomaterials that have a variety of distinctive qualities, including (but not limited to) biocompatibility, highly adjustable mechanical characteristics, and most importantly, the capacity to absorb and retain water in a manner like that of native human nucleus pulposus tissue. In recent years, various hydrogels have been investigated in vitro and in vivo for the repair of intervertebral discs, some of which are ready for clinical testing. In this review, we summarize the latest findings and developments in the application of hydrogel technology for the repair and regeneration of intervertebral discs.

N-cadherin Alleviates Apoptosis and Senescence of Nucleus Pulposus Cells via Suppressing ROS-dependent ERS in the Hyper-osmolarity Microenvironment

The in-situ osmolarity is an important physicochemical factor that regulates cell fate of nucleus pulposus cells (NPCs). Our previous studies demonstrated that reduced N-cadherin (NCDH) expression in nucleus pulposus cells is associated with cellular damage under hyper-osmolarity microenvironment. This study was aimed at exploring the impacts of NCDH on senescence and apoptosis of NPCs, as well as the potential molecular mechanism. By comparing NPCs from patients with lumbar fractures and lumbar disc herniation, we identified a correlation between decreased NCDH expression and increased endoplasmic reticulum stress (ERS), resulting in undesirable cell fate (senescence and apoptosis). After blocking Reactive oxygen species (ROS) or ERS, it was indicated that hyper-osmolarity microenvironment induced ERS was ROS-dependent. Further results demonstrated the correlation in rat NPCs. Upregulation of NCDH expression reduced ROS-dependent ERS, thus limiting undesirable cell fates in vitro. This was further confirmed through the rat tail acupuncture injection model. NCDH overexpression successfully mitigated ERS, preserved extracellular matrix production and alleviating intervertebral disc degeneration in vivo. Together, NCDH can alleviate senescence and apoptosis of NPCs by suppressing ROS-dependent ERS via the ATF4-CHOP signaling axis in the hyper-osmolarity microenvironment, thus highlighting the therapeutic potential of NCDH in combating degenerative disc diseases.

Increased Expression of Inflammatory Cytokines and Discogenic Neck Pain

OBJECTIVE

Although neck pain has become a serious economic and social problem worldwide, the etiology remains poorly understood. The aim of current study is to explore the possible pathogenesis of discogenic neck pain by analyzing the relationship between inflammatory cytokines and discogenic neck pain and provide a valuable reference for the prevention and treatment of discogenic neck pain.

METHODS

A total of 111 cervical disc samples were collected between October 1, 2021, and October 1, 2022: 38 samples from the discogenic neck pain group, 41 samples from the symptomatic control group, and 32 samples from the normal control group. The concentration of nitric oxide (NO), interleukin (IL)-1, interleukin (IL)-6, and tumor necrosis factor alpha (TNF-α) was determined using the enzyme-linked immunosorbent assay in each sample, and the degeneration degree of the target discs were evaluated using T2-weighted sagittal magnetic resonance imaging (MRI) according to the Miyazaki disc degeneration grading system. Whether the differences among the three groups were statistically significant was tested using one-way analysis of variance and an unpaired t-test, respectively.

RESULTS

The differences of the baseline characteristics were not statistically significant between the discogenic neck pain group and the symptomatic control group (p > 0.05). The expression of inflammatory cytokines in disc samples from the discogenic neck pain group (NO: 9.89 ± 1.75, IL-1β: 10.74 ± 1.92, IL-6:31.65 ± 2.46, and TNF-α: 5.96 ± 1.91) was increased in comparison with the disc samples from both the symptomatic control group (NO: 7.15 ± 2.78, IL-1β: 8.03 ± 1.87, IL-6: 25.79 ± 2.12, and TNF-α: 4.18 ± 2.87) and the normal control group (NO: 6.11 ± 1.37, IL-1β: 5.84 ± 2.25, IL-6: 20.65 ± 1.26, and TNF-α: 2.05 ± 0.58). The differences were statistically significant (p < 0.001). Further, there were no statistical differences in the degree of degeneration between discogenic neck pain group and symptomatic control group.

CONCLUSIONS

The increased expression of inflammatory cytokines in diseased cervical intervertebral discs might play a key role in the pathogenesis of discogenic neck pain. Although inflammation is involved in intervertebral disc degeneration, there is no linear positive correlation between the concentration of inflammatory cytokines and the degree of disc degeneration.

Mesenchymal stem cell exosomes inhibit nucleus pulposus cell apoptosis via the miR-125b-5p/TRAF6/NF-κB pathway axis

Intervertebral disc degeneration (IVDD) is the pathological basis of a range of degenerative spinal diseases and is the primary cause of lower back pain. Mesenchymal stem cell (MSC) transplantation inhibits IVDD progression. However, the specific mechanisms that underlie these effects remain unclear. In this study, candidate microRNAs (miRNAs) are screened using bioinformatics and high-throughput sequencing. TNF-α is used to induce nucleus pulposus cell (NPC) degeneration. MSC-derived exosomes (MSC-exosomes) are obtained using high-speed centrifugation and identified by transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA) and western blot analysis. Cell viability is determined by CCK-8 assay. Flow cytometry and TUNEL assays are used to detect cell apoptosis. The expression levels of miR-125b-5p are detected by RT-qPCR, and a dual-luciferase gene reporter assay confirms the downstream target genes of miR-125b-5p. Protein expression is determined by western blot analysis. Rat models are used to validate the function of miR-125b-5p in MSC-exosomes. The results show that miR-125b-5p is expressed at low levels in degenerated disc tissues compared with that in normal disc tissues; however, it is highly expressed in MSC-exosomes. Furthermore, MSC-exosomes are efficiently taken up by NPCs while miR-125b-5p is delivered into NPCs; thus, MSC-exosomes act as inhibitors of apoptosis in NPCs. Overexpression of miR-125b-5p downregulates TRAF6 expression and inhibits NF-κB activation. However, TRAF6 overexpression reverses these effects of miR-125b-5p. We demonstrate that MSC-exosomes attenuate IVDD in vivo by delivering miR-125b-5p. MSC-exosomes can deliver miR-125b-5p to target TRAF6, inhibit NF-κB activation, and attenuate the progression of IVDD.

Comprehensive analysis of senescence-related genes and immune infiltration in intervertebral disc degeneration: a meta-data approach utilizing bulk and single-cell RNA sequencing data

Objectives: This study aims to identify the key senescence genes and potential regulatory mechanisms that contribute to the etiology of intervertebral disc degeneration (IDD). Method: We analyzed GSE34095 and GSE70362 datasets, identifying key senescence-related differentially expressed genes (DEGs) in IDD using lasso regression. Risk scores classified patients into high- and low-risk groups. We compared pathways, functions, and immune infiltration between these groups. Diagnostic ability was assessed using ROC curves and a nomogram predicted IDD incidence. In single-cell dataset GSE165722, we evaluated expression of key senescence-related DEGs. Results: We identified 12 key senescence-related DEGs distinguishing high- and low-risk IDD patients. Enrichment analysis revealed cellular stress response, apoptotic signaling pathway, and protein kinase activation differences. Immune cell analysis showed elevated eosinophils in low-risk group and increased effector memory CD8 T, central memory CD4 T, myeloid-derived suppressor, natural killer, monocyte, Type 1 T helper, plasmacytoid dendritic, and natural killer T cells in high-risk group. A nomogram using AUC >0.75 genes (CXCL8, MAP4K4, MINK1, and TNIK) predicted IDD incidence with good diagnostic power. High senescence scores were observed in neutrophils. Conclusion: Our diagnostic model, based on key senescence-related DEGs and immune cell infiltration, offers new insights into IDD pathogenesis and immunotherapy strategies.

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.

Analysis of global research hotspots and trends in immune cells in intervertebral disc degeneration: A bibliometric study

Intervertebral disc degeneration is an important pathological basis for spinal degenerative diseases. The imbalance of the immune microenvironment and the involvement of immune cells has been shown to lead to nucleus pulposus cells death. This article presents a bibliometric analysis of studies on immune cells in IDD in order to clarify the current status and hotspots. We searched the WOSCC, Scopus and PubMed databases from 01/01/2001 to 08/03/2023. We analyzed and visualized the content using software such as Citespace, Vosviewer and the bibliometrix. This study found that the number of annual publications is increasing year on year. The journal study found that Spine had the highest number of articles and citations. The country/regions analysis showed that China had the highest number of publications, the USA had the highest number of citations and total link strength. The institutional analysis found that Shanghai Jiao Tong University and Huazhong University of Science Technology had the highest number of publications, Tokai University had the highest citations, and the University of Bern had the highest total link strength. Sakai D and Risbud MV had the highest number of publications. Sakai D had the highest total link strength, and Risbud MV had the highest number of citations. The results of the keyword analysis suggested that the current research hotspots and future directions continue to be the study of the mechanisms of immune cells in IDD, the therapeutic role of immune cells in IDD and the role of immune cells in tissue engineering for IDD.

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.

Mitochondrial dysfunction: a new molecular mechanism of intervertebral disc degeneration

OBJECTIVE

Intervertebral disc degeneration (IVDD) is a chronic degenerative orthopedic illness that causes lower back pain as a typical clinical symptom, severely reducing patients' quality of life and work efficiency, and imposing a significant economic burden on society. IVDD is defined by rapid extracellular matrix breakdown, nucleus pulposus cell loss, and an inflammatory response. It is intimately related to the malfunction or loss of myeloid cells among them. Many mechanisms have been implicated in the development of IVDD, including inflammatory factors, oxidative stress, apoptosis, cellular autophagy, and mitochondrial dysfunction. In recent years, mitochondrial dysfunction has become a hot research topic in age-related diseases. As the main source of adenosine triphosphate (ATP) in myeloid cells, mitochondria are essential for maintaining myeloid cell survival and physiological functions.

METHODS

We searched the PUBMED database with the search term "intervertebral disc degeneration and mitochondrial dysfunction" and obtained 82 articles, and after reading the abstracts and eliminating 30 irrelevant articles, we finally obtained 52 usable articles.

RESULTS

Through a review of the literature, it was discovered that IVDD and cellular mitochondrial dysfunction are also linked. Mitochondrial dysfunction contributes to the advancement of IVDD by influencing a number of pathophysiologic processes such as mitochondrial fission/fusion, mitochondrial autophagy, cellular senescence, and cell death.

CONCLUSION

We examine the molecular mechanisms of IVDD-associated mitochondrial dysfunction and present novel directions for quality management of mitochondrial dysfunction as a treatment approach to IVDD.

Does vertebral osteoporosis delay or accelerate lumbar disc degeneration? A systematic review

The effect of vertebral osteoporosis on disc degeneration is still debated. The purpose of this study was to provide a systematic review of studies in this area to further reveal the relationship between the two. Relevant studies were searched in electronic databases, and studies were screened according to inclusion and exclusion criteria, and finally, basic information of the included studies was extracted and summarized. This study was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. A total of 34 publications spanning 24 years were included in our study. There were 19 clinical studies, including 12 prospective studies and 7 retrospective studies. Of these, 7 considered vertebral osteoporosis to be positively correlated with disc degeneration, 8 considered them to be negatively correlated, and 4 considered them to be uncorrelated. Two cadaveric studies were included, one considered the two to be negatively correlated and one considered them not to be correlated. Seven animal studies were included, of which five considered a positive correlation between vertebral osteoporosis and disc degeneration and two considered a negative correlation between the two. There were also 6 studies that used anti-osteoporosis drugs for intervention, all of them were animal studies. Five of them concluded that vertebral osteoporosis was positively associated with disc degeneration, and the remaining one concluded that there was no correlation between the two. Our systematic review shows that the majority of studies currently consider an association between vertebral osteoporosis and disc degeneration, but there is still a huge disagreement whether this association is positive or negative. Differences in observation time and follow-up time may be one of the reasons for the disagreement. A large number of clinical and basic studies are still needed in the future to further explore the relationship between the two.

Can extracellular vesicles be considered as a potential frontier in the treatment of intervertebral disc disease?

As a global public health problem, low back pain (LBP) caused by intervertebral disc degeneration (IDD) seriously affects patients' quality of life. In addition, the prevalence of IDD tends to be younger, which brings a huge burden to individuals and society economically. Current treatments do not delay or reverse the progression of IDD. The emergence of biologic therapies has brought new hope for the treatment of IDD. Among them, extracellular vesicles (EVs), as nanoscale bioactive substances that mediate cellular communication, have now produced many surprising results in the research of the treatment of IDD. This article reviews the mechanisms and roles of EVs in delaying IDD and describes the prospects and challenges of EVs.

How to enhance the ability of mesenchymal stem cells to alleviate intervertebral disc degeneration

Intervertebral disc (ID) degeneration (IDD) is one of the main causes of chronic low back pain, and degenerative lesions are usually caused by an imbalance between catabolic and anabolic processes in the ID. The environment in which the ID is located is harsh, with almost no vascular distribution within the disc, and the nutrient supply relies mainly on the diffusion of oxygen and nutrients from the blood vessels located under the endplate. The stability of its internal environment also plays an important role in preventing IDD. The main feature of disc degeneration is a decrease in the number of cells. Mesenchymal stem cells have been used in the treatment of disc lesions due to their ability to differentiate into nucleus pulposus cells in a nonspecific anti-inflammatory manner. The main purpose is to promote their regeneration. The current aim of stem cell therapy is to replace the aged and metamorphosed cells in the ID and to increase the content of the extracellular matrix. The treatment of disc degeneration with stem cells has achieved good efficacy, and the current challenge is how to improve this efficacy. Here, we reviewed current treatments for disc degeneration and summarize studies on stem cell vesicles, enhancement of therapeutic effects when stem cells are mixed with related substances, and improvements in the efficacy of stem cell therapy by adjuvants under adverse conditions. We reviewed the new approaches and ideas for stem cell treatment of disc degeneration in order to contribute to the development of new therapeutic approaches to meet current challenges.

Role of arachidonic acid metabolism in intervertebral disc degeneration: identification of potential biomarkers and therapeutic targets via multi-omics analysis and artificial intelligence strategies

BACKGROUND

Intervertebral disc degeneration (IVDD) is widely recognized as the primary etiological factor underlying low back pain, often necessitating surgical intervention as the sole recourse in severe cases. The metabolic pathway of arachidonic acid (AA), a pivotal regulator of inflammatory responses, influences the development and progression of IVDD.

METHODS

Initially, a comparative analysis was conducted to investigate the relationship between AA expression patterns and different stages of IVDD using single-cell sequencing (scRNA-seq) data. Additionally, three machine learning methods (LASSO, random forest, and support vector machine recursive feature elimination) were employed to identify hub genes associated with IVDD. Subsequently, a novel artificial intelligence prediction model was developed for IVDD based on an artificial neural network algorithm and validated using an independent dataset. The identified hub genes were further subjected to functional enrichment, immune infiltration, and Connectivity Map analysis. Moreover, external validation was performed using flow cytometry and real-time reverse transcription polymerase chain reaction analysis.

RESULTS

Both scRNA-seq and bulk RNA-seq data revealed a positive correlation between the severity of IVDD and the AA metabolic pathway. They also revealed increased AA metabolic activity in macrophages and neutrophils, as well as enhanced intercellular communication with nucleus pulposus cells. Utilizing advanced machine learning algorithms, five hub genes (AKR1C3, ALOX5, CYP2B6, EPHX2, and PLB1) were identified, and an incipient diagnostic model was developed with an AUC of 0.961 in the training cohort and 0.72 in the validation cohort. An in-depth exploration of the functionality of these hub genes revealed their notable association with inflammatory responses and immune cell infiltration. Lastly, AH6809 was found to delay IVDD by inhibiting AKR1C3.

CONCLUSIONS

This study offers comprehensive insights into potential biomarkers and small molecules associated with the early pathogenesis of IVDD. The identified biomarkers and the developed integrated diagnostic model hold great promise in predicting the onset of early IVDD. AH6809 was established as a therapeutic target for AKR1C3 in the treatment of IVDD, as evidenced by computer simulations and biological experiments.

Machine learning algorithm predicts fibrosis-related blood diagnosis markers of intervertebral disc degeneration

BACKGROUND

Intervertebral disc cell fibrosis has been established as a contributing factor to intervertebral disc degeneration (IDD). This study aimed to identify fibrosis-related diagnostic genes for patients with IDD.

METHODS

RNA-sequencing data was downloaded from Gene Expression Omnibus (GEO) database. The diagnostic genes was identified using Random forest based on the differentially expressed fibrosis-related genes (DE-FIGs) between IDD and control samples. The immune infiltration states in IDD and the regulatory network as well as potential drugs targeted diagnostic genes were investigated. Quantitative Real-Time PCR was conducted for gene expression valifation.

RESULTS

CEP120 and SPDL1 merged as diagnostic genes. Substantial variations were observed in the proportions of natural killer cells, neutrophils, and myeloid-derived suppressor cells between IDD and control samples. Further experiments indicated that AC144548.1 could regulate the expressions of SPDL1 and CEP120 by combininghsa-miR-5195-3p and hsa-miR-455-3p, respectively. Additionally, transcription factors FOXM1, PPARG, and ATF3 were identified as regulators of SPDL1 and CEP120 transcription. Notably, 56 drugs were predicted to target these genes. The down-regulation of SPDL1 and CEP120 was also validated.

CONCLUSION

This study identified two diagnostic genes associated with fibrosis in patients with IDD. Additionally, we elucidated their potential regulatory networks and identified target drugs, which offer a theoretical basis and reference for further study into fibrosis-related genes involved in IDD.

Mechanisms of inhibition of nucleus pulposus cells pyroptosis through SDF1/CXCR4-NFkB-NLRP3 axis in the treatment of intervertebral disc degeneration by Duhuo Jisheng Decoction

Intervertebral disc degeneration (IVDD) is one of the leading causes of lower back pain and the most common health problem in the world. Inflammasomes, which is mainly caused by NLRP3, mediated nucleus pulposus pyroptosis has been discovered to be strongly related to IVDD. In addition, Duhuo Jisheng Decoction (DHJSD) has anti-inflammatory and regulatory effects on NLRP3 inflammasome, but the molecular mechanism of whether DHJSD can regulate pyroptosis through NLRP3 to treat IVDD is unclear. In this study, we used a bioinformatics way to discover the molecular mechanism of DHJSD regulation of pyroptosis in IVDD, and validated our predictions through vitro and vivo experiments. Through bioinformatics, we found that NLRP3, GSDMD, IL-1βand other hub proteins of pyroptosis were highly expressed in IVDD SD rats, and network pharmacology discovered that DHJSD may control cellular senescence, apoptosis, and pyroptosis in order to treat IVDD. Additional findings demonstrated that DHJSD could successfully treat IVDD brought on by imaging and histomorphological analysis. Western blot showed that NLRP3, a key protein of pyroptosis, was elevated in rat degenerated nucleus pulposus tissue and lipopolysaccharide-treated Nucleus pulposus Cells (NPCs), and that DHJSD intervention was effective in reducing LPS-induced inflammatory responses and further suppressing the expression of pyroptosis related proteins to improve IVDD. The specific mechanism is that DHJSD inhibits NPCs pyroptosis via the SDF-1/CXCR4-NF-kB-NLRP3 axis. In conclusion, we revealed the intrinsic mechanism of DHJSD regulation of NPCs pyroptosis to improve IVDD and its intrinsic value for IVDD treatment.

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.

Review: Discogenic Back Pain: Update on Treatment

Purpose of Review

Lower back pain (LBP) has a lifetime prevalence of 80% in the United States population. Discogenic back pain (DBP), a subcategory of LBP, occurs as a result of the interverbal disc degeneration without disc herniation. Diagnosis relies on history, physical exam, and imaging such as MRI, provocative discography, or CT discography.

Recent Findings

Treatment of DBP involves a multifaceted approach with an emphasis on conservative measures including behavioral modification, pharmacologic management, and other non-pharmacologic interventions with invasive therapy reserved for select patients. Due to the paucity of data on the treatment of DBP, treatment also relies on data derived from treatment of chronic LBP (CLBP).

Summary

Despite the scarcity of data for the treatment of DBP, treatments do exist with varying efficacy for DBP. Novel techniques such as the use of biologics may provide another avenue for treatment though further studies are needed to better evaluate the most efficacious regimen for both novel and existing treatments.

Umbilical cord mesenchymal stem cells for regenerative treatment of intervertebral disc degeneration

Intervertebral disc degeneration is thought to be a major contributor to low back pain, the etiology of which is complex and not yet fully understood. To compensate for the lack of drug and surgical treatment, mesenchymal stem cells have been proposed for regenerative treatment of intervertebral discs in recent years, and encouraging results have been achieved in related trials. Mesenchymal stem cells can be derived from different parts of the body, among which mesenchymal stem cells isolated from the fetal umbilical cord have excellent performance in terms of difficulty of acquisition, differentiation potential, immunogenicity and ethical risk. This makes it possible for umbilical cord derived mesenchymal stem cells to replace the most widely used bone marrow-derived and adipose tissue derived mesenchymal stem cells as the first choice for regenerating intervertebral discs. However, the survival of umbilical cord mesenchymal stem cells within the intervertebral disc is a major factor affecting their regenerative capacity. In recent years biomaterial scaffolds in tissue engineering have aided the survival of umbilical cord mesenchymal stem cells by mimicking the natural extracellular matrix. This seems to provide a new idea for the application of umbilical cord mesenchymal stem cells. This article reviews the structure of the intervertebral disc, disc degeneration, and the strengths and weaknesses of common treatment methods. We focus on the cell source, cell characteristics, mechanism of action and related experiments to summarize the umbilical cord mesenchymal stem cells and explore the feasibility of tissue engineering technology of umbilical cord mesenchymal stem cells. Hoping to provide new ideas for the treatment of disc degeneration.

USP24-dependent stabilization of Runx2 recruits a p300/NCOA3 complex to transactivate ADAMTS genes and promote degeneration of intervertebral disc in chronic inflammation mice

BACKGROUND

Intervertebral disc degeneration (IDD) naturally occurs during the aging process. Its occurrence is closely related to chronic inflammation; however, the causal relationship between them is controversial. This study aimed to investigate if inflammation would promote IDD incidence and explore the underlying mechanism.

METHODS

A chronic inflammation mouse model was established by intraperitoneal injection of lipopolysaccharide (LPS). Enzyme-linked immunosorbent assay was performed to determine proinflammatory cytokines in serum. Histological staining was used to evaluate the degeneration of IVDs. Immunoblots and RT-qPCR analyses were performed to measure protein and mRNA expression levels. Immunoprecipitation, mass spectrometry, and co-immunoprecipitation assays were used to determine the assembly of protein complex.

RESULTS

We found that an inflammatory microenvironment activated p38 kinase, which phosphorylated the Runx2 transcription factor at the Ser28 site. The phosphorylated Runx2 (pRunx2) then recruited a deubiquitinase, ubiquitin-specific peptidase 24 (USP24), which stabilized pRunx2 and protected it from ubiquitin-dependent proteasomal degradation. The stabilized pRunx2 recruited histone acetyltransferase p300 and nuclear receptor coactivator 3 (NCOA3) to assemble a complex. This NCOA3-p300-pRunx2 complex then transactivated the expression of 13 ADAMTS (a disintegrin and metalloproteinase with thrombospondin motif) genes, thereby promoting the degradation of extracellular matrix (ECM) in intervertebral discs (IVDs) and causing IDD. Administration of either a p38 inhibitor (doramapimod), a NCOA3 inhibitor (bufalin), or a p300 inhibitor (EML425) significantly decreased the expression of the 13 ADAMTS genes and slowed the degeneration of IVDs.

CONCLUSION

In summary, our results demonstrate that USP24 protects pRunx2 from proteasomal degradation under chronic inflammation conditions, enabling pRunx2 to transactivate ADAMTS genes and degrade ECM. Our findings provide direct evidence that chronic inflammation triggers IDD and offer a therapeutic strategy for retarding IDD in patients with chronic inflammation.

T2 mapping of lumbar intervertebral disc: quantitative evaluation of degeneration in relation to Pfirrmann grading system and a template for intervertebral disc segmentation

Background

To assess the feasibility of using T2 relaxation time mapping at 3 Tesla (3T) magnetic resonance imaging (MRI) for detection and classification of lumbar intervertebral disc degeneration, introducing an objective model of disc segmentation for accurate disc assessment.

Materials and Methods

The present study is a single-center prospective evaluation including 185 lumbar intervertebral discs from a cohort of 37 patients with chronic lower back pain. For the quantitative classification of disc degeneration, three regions of interest (ROIs) were drawn on T2 maps, and the Pfirrmann grading system was used for qualitative assessment. Intergroup evaluation was performed with paired t-tests. Analysis of variance (ANOVA) was used to compare the mean value of T2 mapping, and Tukey's multiple comparison test was applied to determine differences in mean values of T2 mapping among the Pfirrmann categories.

Results

The ANOVA test analysis of ROIs showed that there is a statistically significant difference (p <0.001) among average T2 relaxation time mapping values in different Pfirrmann score groups, and Tukey's multiple comparison tests revealed that mean values of T2 map among the different grades of Pfirrmann differ from the rest (p <0.001) except grade V. Paired t-tests revealed significant differences in mean values of T2 map between different ROIs.

Conclusion

This study showed that quantitative T2 mapping of the lumbar intervertebral discs at 3T MRI may overcome the subjective element of qualitative classification systems for degenerative intervertebral disc disease. Also, a new template of disc segmentation with more ROIs would be more sensitive for the assessment of disc degeneration. HIPPOKRATIA 2023, 27 (2):75-81.

Pan-cancer analysis of the intervertebral-disc-degeneration-related innate immunity gene NAIP

BACKGROUND

Intervertebral disc degeneration (IDD) is a progressive chronic condition that commonly causes low back pain. Cancer is among the primary reasons for deaths worldwide. Our purpose was to identify the characteristic genes of IDD and explore the potential association between IDD and cancer.

METHODS

Immune cell infiltration and differentially expressed analysis were conducted utilizing data from the GSE124272 database. Enrichment analysis of differentially expressed genes (DEGs) was performed to explore the possible mechanisms underlying IDD development. Moreover, weighted gene correlation network analysis (WGCNA) was applied to select IDD-related hub genes. The immune-related key genes were determined by intersecting DEGs, IDD-related hub genes, and immune genes. Subsequently, machine learning models based on these genes were built to identify and verify the characteristic genes. RNA sequencing and clinical data of 33 carcinoma categories were obtained from the Cancer Genome Atlas (TCGA). The association between NAIP expression and prognosis was calculated using the Kaplan-Meier analysis. To gain a deeper understanding of the impact of NAIP in tumor immunotherapy, the association between NAIP and immune infiltration and two immunotherapeutic biomarkers were explored. Ultimately, the association between NAIP and immunotherapeutic response was investigated utilizing two independent cohorts.

RESULTS

NAIP was identified as an immune-related characteristic gene between IDD and normal intervertebral disc tissue. In certain carcinoma categories, NAIP expression levels were elevated (4/33) and significantly correlated to the respective tumor stage (4/21). Survival analysis revealed that the expression levels of NAIP have prognostic significance in different cancer types. Generally, NAIP presented a strong association with immune cell infiltration and modulators. NAIP may influence immunotherapy effects through tumor mutational burden and microsatellite instability. No remarkable association between NAIP and immunotherapy response was found in either cohort.

CONCLUSION

Our study is the first to identify NAIP as an immune-related characteristic gene. Pan-cancer analysis revealed that NAIP could serve as a novel clinical prognostic marker and therapeutic target for a variety of carcinoma categories, reducing the risk of IDD in tumor patients.

Identification of a potential novel biomarker in intervertebral disk degeneration by bioinformatics analysis and experimental validation

Background

Intervertebral disk degeneration (IVDD) is a major cause of low back pain and one of the most common health problems all over the world. However, the early diagnosis of IVDD is still restricted. The purpose of this study is to identify and validate the key characteristic gene of IVDD and analyze its correlation with immune cell infiltration.

Methods

3 IVDD-related gene expression profiles were downloaded from the Gene Expression Omnibus database to screen for differentially expressed genes (DEGs). Gene Ontology (GO) and gene set enrichment analysis (GSEA) were conducted to explore the biological functions. Two machine learning algorithms were used to identify characteristic genes, which were tested to further find the key characteristic gene. The receiver operating characteristic curve was performed to estimate the clinical diagnostic value of the key characteristic gene. The excised human intervertebral disks were obtained, and the normal nucleus pulposus (NP) and degenerative NP were carefully separated and cultured in vitro. The expression of the key characteristic gene was validated by real-time quantitative PCR (qRT-PCR). The related protein expression in NP cells was detected by Western blot. Finally, the correlation was investigated between the key characteristic gene and immune cell infiltration.

Results

A total of 5 DEGs, including 3 upregulated genes and 2 downregulated genes, were screened between IVDD and control samples. GO enrichment analysis showed that DEGs were enriched to 4 items in BP, 6 items in CC, and 13 items in MF. They mainly included the regulation of ion transmembrane transport, transporter complex, and channel activity. GSEA suggested that the cell cycle, DNA replication, graft versus host disease, and nucleotide excision repair were enriched in control samples, while complement and coagulation cascades, Fc γ R-mediated phagocytosis, neuroactive ligand-receptor interaction, the NOD-like receptor signaling pathway, gap junctions, etc., were enriched in IVDD samples. Furthermore, ZNF542P was identified and tested as key characteristic gene in IVDD samples through machine learning algorithms and showed a good diagnostic value. The results of qRT-PCR showed that compared with normal NP cells, the expression of ZNF542P gene was decreased in degenerated NP cells. The results of Western blot suggested that compared with normal NP cells, the expression of NLRP3 and pro Caspase-1 was increased in degenerated NP cells. Finally, we found that the expression of ZNF542P was positively related to the proportions of T cells gamma delta (γδT cells).

Conclusion

ZNF542P is a potential biomarker in the early diagnosis of IVDD and may be associated with the NOD-like receptor signaling pathway and the infiltration of γδT cells.

Aging, cell senescence, the pathogenesis and targeted therapies of intervertebral disc degeneration

Intervertebral disc degeneration (IVDD) refers to the aging and degenerative diseases of intervertebral disc components such as nucleus pulposus, annulus fibrosus, and cartilage endplate, and is the main cause of chronic low back pain. Over the past few years, many researchers around the world concerned that the degeneration of nucleus pulposus (NP) cells plays the main role in IVDD. The degeneration of NP cells is caused by a series of pathological processes, including oxidative stress, inflammatory response, apoptosis, abnormal proliferation, and autophagy. Interestingly, many studies have found a close relationship between the senescence of NP cells and the progression of NP degeneration. The classical aging pathways also have been confirmed to be involved in the pathological process of IVDD. Moreover, several anti-aging drugs have been used to treat IVDD by inhibiting NP cells senescence, such as proanthocyanidins, resveratrol and bone morphogenetic protein 2. Therefore, this article will systematically list and discuss aging, cell senescence, the pathogenesis and targeted therapies of IVDD, in order to provide new ideas for the treatment of IVDD in the future.

Comparison of Analgesic Efficacy between Epidural and Perineural Administration of Autologous Conditioned Serum in the Conservative Treatment of Low Back Pain Due to Lumbar Degenerative Disc Disease: A Randomized, Open-Label, Controlled Clinical Trial

Lumbar degenerative disc disease (LDDD) is widely acknowledged as a significant contributor to low back pain (LBP), which is a prevalent and debilitating health condition affecting millions of individuals worldwide. The pathogenesis of LDDD and associated pain mechanisms are thought to be mediated by inflammatory mediators. Autologous conditioned serum (ACS, Orthokine) may be used for symptomatic treatment of LBP due to LDDD. This study aimed to compare the analgesic efficacy and safety of two routes of ACS administration, perineural (periarticular) and epidural (interlaminar), in the conservative treatment of LBP. This study used an open-label, randomized, controlled trial protocol. A group of 100 patients were enrolled in the study and randomly allocated into two comparative groups. Group A (n = 50) received the epidural (interlaminar) approach-2 ultrasound-guided injections as control intervention (each containing two doses of ACS-8 mL). Group B (n = 50) received the perineural (periarticular) approach-2 ultrasound-guided injections as experimental intervention at 7-day intervals (the same volume of ACS). Assessments consisted of an initial assessment (IA) and control assessments at 4 (T1), 12 (T2), and 24 (T3) weeks after the last intervention. Primary outcomes comprised Numeric Rating Scale (NRS), Oswestry Disability Index (ODI), Roland Morris Questionnaire (RMQ), and Euro Quality of Life-5 Dimensions-5 Levels (EQ-5D-5L): Index, Visual Analogue Scale (VAS), and Level Sum Score (LSS). Secondary outcomes included differences between groups in specific endpoints for the above-mentioned questionnaires. In conclusion, this study revealed that both perineural (periarticular) and epidural ACS injections tended to perform in a very similar way. Both routes of Orthokine application show significant improvement in the primary clinical parameters, such as pain and disability, and therefore, both methods can be considered equally effective in managing LBP due to LDDD.

Cellular senescence - Molecular mechanisms of intervertebral disc degeneration from an immune perspective

Intervertebral disc degeneration (IVDD) is a frequent and intractable chronic condition in orthopedics that causes enormous discomfort in patients' lives and thoughts, as well as a significant economic burden on society and the nation. As a result, understanding the pathophysiology of IVDD is critical. The pathophysiology of IVDD has been linked to numerous variables, including oxidative stress, apoptosis, matrix metalloproteinases, and inflammatory factors. Cellular senescence has recently attracted a lot of attention in the study of age-related diseases. It has been discovered that IVDD is intimately linked to human senescence, in which nucleus pulposus cell senescence may play a significant role. Previously, our group did a comprehensive and systematic clarification of the pathogenesis of IVDD from an immune perspective and discovered that the fundamental pathogenesis of IVDD is inflammatory upregulation and nucleus pulposus cell death caused by an imbalance in the immune microenvironment. In this review, we will treat nucleus pulposus cell senescence as a novelty point to clarify the pathophysiology of IVDD and further explore the probable relationship between senescence and immunity along with the dysregulation of the immunological microenvironment to propose new therapeutic approaches for IVDD.

Intervertebral disc degeneration and osteoarthritis: a common molecular disease spectrum

Intervertebral disc degeneration (IDD) and osteoarthritis (OA) affecting the facet joint of the spine are biomechanically interdependent, typically occur in tandem, and have considerable epidemiological and pathophysiological overlap. Historically, the distinctions between these degenerative diseases have been emphasized. Therefore, research in the two fields often occurs independently without adequate consideration of the co-dependence of the two sites, which reside within the same functional spinal unit. Emerging evidence from animal models of spine degeneration highlight the interdependence of IDD and facet joint OA, warranting a review of the parallels between these two degenerative phenomena for the benefit of both clinicians and research scientists. This Review discusses the pathophysiological aspects of IDD and OA, with an emphasis on tissue, cellular and molecular pathways of degeneration. Although the intervertebral disc and synovial facet joint are biologically distinct structures that are amenable to reductive scientific consideration, substantial overlap exists between the molecular pathways and processes of degeneration (including cartilage destruction, extracellular matrix degeneration and osteophyte formation) that occur at these sites. Thus, researchers, clinicians, advocates and policy-makers should consider viewing the burden and management of spinal degeneration holistically as part of the OA disease continuum.

Constitutive and conditional gene knockout mice for the study of intervertebral disc degeneration: Current status, decision considerations, and future possibilities

There have been an increasing number of patients with degenerative disc diseases due to the aging population. In light of this, studies on the pathogenesis of intervertebral disc degeneration have become a hot topic, and gene knockout mice have become a valuable tool in this field of research. With the development of science and technology, constitutive gene knockout mice can be constructed using homologous recombination, zinc finger nuclease, transcription activator-like effector nuclease technology and clustered regularly interspaced short palindromic repeats/Cas9 (CRISPR/Cas9) system, and conditional gene knockout mice can be constructed using the Cre/LoxP system. The gene-edited mice using these techniques have been widely used in the studies on disc degeneration. This paper reviews the development process and principles of these technologies, functions of the edited genes in disc degeneration, advantages, and disadvantages of different methods and possible targets of the specific Cre recombinase in intervertebral discs. Recommendations for the choice of suitable gene-edited model mice are presented. At the same time, possible technological improvements in the future are also discussed.

Mechanical stimulation promotes MSCs healing the lesion of intervertebral disc annulus fibrosus

Mesenchymal stem cells (MSCs) and scaffolds offer promising perspectives for annulus fibrosus (AF) repair. The repair effect was linked to features of the local mechanical environment related to the differentiation of MSCs. In this study, we established a Fibrinogen-Thrombin-Genipin (Fib-T-G) gel which is sticky and could transfer strain force from AF tissue to the human mesenchymal stem cells (hMSCs) embedded in the gel. After the Fib-T-G biological gel was injected into the AF fissures, the histology scores of intervertebral disc (IVD) and AF tissue showed that Fib-T-G gel could better repair the AF fissure in caudal IVD of rats, and increase the expression of AF-related proteins including Collagen 1 (COL1), Collagen 2 (COL2) as well as mechanotransduction-related proteins including RhoA and ROCK1. To clarify the mechanism that sticky Fib-T-G gel induces the healing of AF fissures and the differentiation of hMSCs, we further investigated the differentiation of hMSCs under mechanical strain in vitro. It was demonstrated that both AF-specific genes, including Mohawk and SOX-9, and ECM markers (COL1, COL2, aggrecan) of hMSCs were up-regulated in the environment of strain force. Moreover, RhoA/ROCK1 proteins were also found to be significantly up-regulated. In addition, we further -demonstrated that the fibrochondroinductive effect of the mechanical microenvironment process could be significantly blocked or up-regulated by inhibiting the RhoA/ROCK1 pathway or overexpressing RhoA in MSCs, respectively. Summarily, this study will provide a therapeutic alternative to repair AF tears and provide evidence that RhoA/ROCK1 is vital for hMSCs response to mechanical strain and AF-like differentiation.

Nucleus pulposus cell-derived efficient microcarrier for intervertebral disc tissue engineering

Adipose-derived stem cells (ADSCs) show great potential for the treatment of intervertebral disc (IVD) degeneration. An ideal carrier is necessary to transplant ADSCs into degenerated IVDs without influencing cell function. Nucleus pulposus cells (NPCs) can synthesize and deposit chondroitin sulfate and type II collagen which are NP-specific extracellular matrix (ECM) and can also regulate the NP-specific differentiation of stem cells. Bioscaffolds fabricated based on the ECM synthesis functions of NPCs have possible roles in cell transplantation and differentiation induction, but it has not been studied. In this study, we first aggregated NPCs into pellets, and then, NPC-derived efficient microcarriers (NPCMs) were fabricated by pellet cultivation under specific conditions and optimized decellularization. Thirdly, we evaluated the microstructure, biochemical composition, biostability and cytotoxicity of the NPCMs. Finally, we investigated the NP-specific differentiation of ADSCs induced by the NPCMsin vitroand NP regeneration induced by the ADSC-loaded NPCMs in a rabbit model. The results indicated that the injectable NPCMs retained maximal ECM and minimal cell nucleic acid after optimized decellularization and had good biostability and no cytotoxicity. The NPCMs also promoted the NP-specific differentiation of ADSCsin vitro. In addition, the results of MRI, x-ray, and the structure and ECM content of NP showed that the ADSCs-loaded NPCMs can partly restored the degenerated NPin vivo. Our injectable NPCMs regenerated the degenerated NP and provide a simplified and efficient strategy for treating IVD degeneration.

Endplate role in the degenerative disc disease: A brief review

The degenerative disease of the intervertebral disc is nowadays an important health problem, which has still not been understood and solved adequately. The vertebral endplate is regarded as one of the vital elements in the structure of the intervertebral disc. Its constituent cells, the chondrocytes in the endplate, may also be involved in the process of the intervertebral disc degeneration and their role is central both under physiological and pathological conditions. They main functions include a role in homeostasis of the extracellular environment of the intervertebral disc, metabolic support and nutrition of the discal nucleus and annulus beneath and the preservation of the extracellular matrix. Therefore, it is understandable that the cells in the endplate have been in the centre of research from several viewpoints, such as development, degeneration and growth, reparation and remodelling, as well as treatment strategies. In this article, we briefly review the importance of vertebral endplate, which are often overlooked, in the intervertebral disc degeneration.

Regulatory roles of noncoding RNAs in intervertebral disc degeneration as potential therapeutic targets (Review)

Intervertebral disc degeneration (IDD) is the leading cause of lower back pain, which is one of the primary factors that lead to disability and pose a serious economic burden. The key pathological processes involved are extracellular matrix degradation, autophagy, apoptosis, and inflammation of nucleus pulposus cells. Non-coding RNAs (ncRNAs), including microRNAs, long ncRNAs and circular RNAs, are key regulators of the aforementioned processes. ncRNAs are differentially expressed in tissues of the intervertebral disc between healthy individuals and patients and participate in the pathological progression of IDD via a complex pattern of gene regulation. However, the regulatory mechanisms of ncRNAs in IDD remain unclear. The present review summarizes the latest insights into the regulatory role of ncRNAs in IDD and sheds light on potentially novel therapeutic strategies for IDD that may be implemented in the future.

Method for the Isolation of "RNA-seq-Quality" RNA from Human Intervertebral Discs after Mortar and Pestle Homogenization

The problem of isolating high-quality total RNA from intervertebral discs has no recognized solution yet. This is due to the extremely low content of live cells in the samples and the voluminous intercellular matrix. A variety of published protocols focused on isolating RNA from articular cartilage have recommended the use of expensive equipment, enzymatic matrix cleavage, or cell culture. In our study, we used a combination of the traditional QIAzol protocol (Qiagen, Germany) and RNEasy column purification (Qiagen, Germany) to obtain high-quality RNA from post-surgical intervertebral disc fragments. Only a mortar and a pestle were used for grinding, making our method particularly accessible. The isolated RNA with a RIN of ~7 is suitable for studying the expression profile of chondrocytes in situ. RNA-seq analysis of three samples demonstrated cell type ratios to be mostly relevant to intervertebral disc tissues, with over 70% of the chondrocytes of the three subtypes having an admixture of blood-related cells.

Application of mesenchymal stem cell-derived exosomes from different sources in intervertebral disc degeneration

Intervertebral disc degeneration (IVDD) is a main cause of lower back pain, leading to psychological and economic burdens to patients. Physical therapy only delays pain in patients but cannot eliminate the cause of IVDD. Surgery is required when the patient cannot tolerate pain or has severe neurological symptoms. Although surgical resection of IVD or decompression of the laminae eliminates the diseased segment, it damages adjacent normal IVD. There is also a risk of re-protrusion after IVD removal. Cell therapy has played a crucial role in the development of regenerative medicine. Cell transplantation promotes regeneration of degenerative tissue. However, owing to the lack of vascular structure in IVD, sufficient nutrients cannot be provided for transplanted mesenchymal stem cells (MSCs). In addition, dead cells release harmful substances that aggravate IVDD. Extracellular vesicles (EVs) have been extensively studied as an emerging therapeutic approach. EVs generated by paracrine MSCs retain the potential of MSCs and serve as carriers to deliver their contents to target cells to regulate target cell activity. Owing to their double-layered membrane structure, EVs have a low immunogenicity and no immune rejection. Therefore, EVs are considered an emerging therapeutic modality in IVDD. However, they are limited by mass production and low loading rates. In this review, the structure of IVD and advantages of EVs are introduced, and the application of MSC-EVs in IVDD is discussed. The current limitations of EVs and future applications are described.

Researches on Stem and Progenitor Cells in Intervertebral Discs: An Analysis of the Scientific Landscape

Low back pain (LBP) is a common clinical symptom, and the prevalence is ranged from 60% to 70%. With the deepening of basic research, the development of intervertebral disc regeneration-oriented cell therapy, especially stem and progenitor cells therapy, showed good research prospects and was expected to become new methods of treatment for LBP. Our study is aimed at analyzing the scientific output of stem and progenitor cells in intervertebral discs and at driving future research into new publications. Researches focused on this file were searched from the Science Citation Index Expanded (SCI-E) of the Web of Science (WOS) core collection database and were screened according to inclusion criteria. We evaluated and visualized the results, including annual publications, citations, authors, organizations, countries, research directions, funds, and journals by bibliometric website, VOSviewer, and Citespace softwares on May 27, 2022. A total of 450 original articles and reviews were included, and the overall trend of the number of publications rapidly increased. In worldwide, China and the USA were the leading countries for research production. The retrieved 450 publications received 14322 citations, with an average of 31.83 citations and an H-index of 62. The most high-yield author, organization, country, research directions, funds, and journals were Chen QX from Zhejiang University, Zhejiang University, China, Cell Biology, National Natural Science Foundation of China, and Spine, respectively. Keywords cluster analysis showed the research hotspots in the future, including “human intervertebral disc”, “adipose-derived mesenchymal stem cell”, “intervertebral disc degeneration”, “degenerative disc model”, “nucleus pulposus regeneration”, “human cartilage”, “3d culture”, “shrinkage-free preparation”, and “polylactide disc”. Furthermore, with accumulating evidence demonstrating the role of stem and progenitor cells in intervertebral discs, “microenvironment”, “activation”, “intervertebral disc degeneration”, and “oxidative stress” are becoming the research frontiers and trends.

Significance of Immune-Related Genes in the Diagnosis and Classification of Intervertebral Disc Degeneration

Background

With the extensive development of intervertebral disc degeneration (IDD) research, IDD has been found to be a complex disease associated with immune-related gene (IRGs) changes. Nonetheless, the roles of IRGs in IDD are unclear.

Methods

In our study, 11 IRGs were chosen using differential analysis between nondisc degeneration and degenerative patients from the GEO database. Then, we utilized a random forest (RF) model to screen six candidate IRGs to predict the risk of IDD. A nomogram was developed on the basis of six candidate IRGs, and DCA showed that patients could benefit from the nomogram. Based on the selected significant IRGs, a consensus clustering approach was used to differentiate disc degeneration patients into two immune patterns (immune cluster A and B). The PCA algorithm was constructed to compute immune scores for every sample, to quantify immune patterns. The immune scores of immune cluster B patients were higher than those of immune cluster A.

Results

Through differential expression analysis between healthy and IDD samples, 11 significant IRGs (CTSS, S100Z, STAT3, KLRK1, FPR1, C5AR2, RLN1, IFGR2, IL2RB, IL17RA, and IL6R) were recognized through significant IRGs. The “Reverse Cumulative Distribution of Residual” and “Boxplots of Residual” indicate that the RF model has minimal residuals. The majority of samples in the model have relatively small residuals, demonstrating that the model is better. Besides, the nomogram model was constructed based on importance and the IRGs with importance scores greater than 2 (FPR1, RLN1, S100Z, IFNGR2, KLRK1, and CTSS). The nomogram model revealed that decision-making based on an established model might be beneficial for IDD patients, and the predictive power of the nomogram model was significant. In addition, we identified two different immune cluster patterns (immune cluster A and immune cluster B) based on the 11 IRGs. We found that immune cluster A had significantly higher levels of MDSC, neutrophil, plasmacytoid dendritic cell, and type 17 T helper cell expression than immune cluster B. And we calculated the score for each sample to quantify the gene patterns. The patients in immune cluster B or gene cluster B had higher immune scores than those in immune cluster A or gene cluster A.

Conclusion

In conclusion, IRGs play an extremely significant role in the occurrence of IDD. Our study of immune patterns may guide the strategies of prevention and treatment for IDD in the future.