The Potential Role of Cytokines in Diabetic Intervertebral Disc Degeneration

Pathophysiology and emerging therapeutic strategies for cervical spondylosis: The role of pro-inflammatory mediators, kinase inhibitors, and Organogel based drug delivery systems

Cervical spondylosis is a prevalent ailment characterized by chronic wear and degenerative changes affecting the cervical spine, leading to various clinical syndromes such as axial neck pain, cervical myelopathy, and cervical radiculopathy. The pathophysiology of the development of cervical alterations is multifaceted, with alterations in the normal physiology and pathogenesis of intervertebral disc degeneration. The involvement of pro-inflammatory mediators, such as interleukin-1, tumor necrosis factor-α, interleukin-4, interleukin-6, and interleukin-10, in the pathological processes associated with intervertebral disc degeneration offers potential therapeutic targets. The review also introduces kinase inhibitors as potential treatments for cervical spondylosis. Protein kinase inhibitors, including mitogen-activated protein kinase (MAPK), Janus kinase (JAK), and spleen tyrosine kinase (SYK), are explored for their anti-inflammatory properties. The article discusses their potential in modulating inflammatory signaling cascades and presents them as attractive candidates for treating immune-mediated disorders. Inhibitors of Nuclear Factor-κB, p38 MAPK, Jun-N terminal kinase (JNK), and Extracellular signal-regulated kinase (ERK) have shown efficacy in suppressing inflammatory responses, offering potential avenues for intervention in this prevalent condition. Organogels are semi-solid materials formed by trapping an organic solvent within a three-dimensional cross-linked network. They hold considerable potential in drug delivery, especially in enhancing drug solubility, facilitating controlled release, and improving skin penetration. These properties of organogels can help treat or alleviate the symptoms of cervical spondylosis.

Can Treatment with Human Mesenchymal Stem Cells Rescue the Degenerative Disc Phenotype? An in Vitro Pilot Study of Induced Cytokine Expression

BACKGROUND CONTEXT

Given the relatively low cell density in degenerative discs, strategies intended to bolster disc cellularity through stem cell injections have come into clinical use. Stem cell therapy is meant to provide a source of viable disc cells that can promote a healthy disc phenotype. Nevertheless, there is a limited understanding of the mechanisms through which stem cell therapy impacts degeneration.

PURPOSE

The objectives of this pilot study were: 1) to evaluate gene expression changes associated with an in vitro induced degenerative phenotype in human nucleus pulposus (NP) cells, 2) to co-culture these degenerative NP cells with human mesenchymal stem cells (hMSCs) and investigate the impact this has on gene expression, 3) to investigate possible mechanisms by which hMSCs may impact the degenerative phenotype.

STUDY DESIGN

Laboratory study.

METHODS

NP cells were isolated and cultured from patients undergoing anterior lumbar interbody fusion for degenerative disc disease. A degenerative phenotype was induced in cultured NP cells by treatment with an inflammatory protocol (10pg/ml IL-1β and 100pg/ml TNF-α) for 7 days. Gene expression of Treated NP cells was compared to Untreated NP cells via reverse transcriptase polymerase chain reaction. NP cells were then co-cultured with hMSCs in vitro and treated with the inflammatory protocol. Gene expression of Treated NP cells co-cultured with hMSCs was compared to Treated NP cells alone. Preliminary co-culture data demonstrated that IL-10 was uniquely and dramatically upregulated. Therefore, gene expression of Treated NP cells exposed to IL-10 for 24 hours was compared to Treated NP cells alone.

RESULTS

Treated NP cells compared to Control NP cells showed upregulation of numerous pro-inflammatory cytokines, including CXCL5, IL-8, and IL-6 and downregulation of several anti-inflammatory cytokines, including IL-10. After co-culture of Treated NP cells with hMSCs, a significant increase in gene expression was identified in IL-10 (+15.34 fold), BMP-6 (+2.32 fold), and LIF (+2.14 fold). A significant decrease in gene expression (p < 0.05) was seen in CCL7 (-2.03) and CXCL12 (-1.67). Exposure of Treated NP cells to IL-10 resulted in upregulation of COL-2 (+1.55 fold, p=0.013) and downregulation of IL-8 (-1.4 fold), CXCL-5 (-1.58 fold,), and MMP-3 (-2.02 fold).

CONCLUSION

This in vitro pilot study shows that co-culture of degenerative phenotype NP cells with hMSCs produces multiple gene regulatory changes associated with an anti-inflammatory phenotype. Additionally, exposure of degenerative phenotype NP cells to IL-10 produces gene regulation associated with both anti-inflammatory and pro-extracellular matrix effects.

CLINICAL SIGNIFICANCE

These findings provide mechanistic support for the use of stem cell therapy as a strategy to decrease the pro-inflammatory molecular environment associated with disc degeneration. Additionally, given the challenges with the viability of hMSCs in the disc microenvironment, IL-10 may be another potential candidate for future targeted therapies for disc degeneration.

E74-like ETS transcription factor 3 expression and regulation in human intervertebral disc

Background

Intervertebral disc degeneration (IVDD) is one of the main causes of chronic low back pain. The degenerative process is often initiated by an imbalance between catabolic and anabolic pathways. Despite the large socio-economic impact, the initiation and progress of disc degeneration are poorly understood. Although intervertebral disc (IVD) and articular joint are not identical, their degenerative roads are remarkably similar. We, and another authors, previously demonstrated that E-74-like factor 3 (ELF3), a transcription factor induced by inflammatory mediators in various cell types including chondrocytes, is a central contributing factor for cartilage degradation. Thus, we aim to explore, for the first time, the expression, modulation, and the role of ELF3 in human IVD cells.

Methods

The presence of ELF3 in healthy and degenerated IVD tissues was initially determined by immunohistochemistry in annulus fibrosus (AF) and nucleus pulposus (NP). mRNA and protein expression were measured, respectively, by RT-qPCR and Western blot in AF and NP IVD cells harvested from healthy individuals and IVDD patients. Overexpression of ELF3 was performed by transfection of AF IVDD cells with pESE-1: ELF3 expression vector or pCI: empty vector.

Results

Our results unveiled, for the first time, the expression of ELF3 in IVD tissues. ELF3 is notably upregulated in degenerated tissues compared to those from healthy patients. In addition, the stimulation of IVDD AF cells with various proinflammatory stimuli, showed marked increase in both mRNA and protein expression of ELF3. ELF3 overexpression in AF IVDD cells resulted in the upregulation of proinflammatory and catabolic genes such as PTGS2, NOS2, LCN2, IL-6, MMP13, and ADAMTS-5; whereas, ELF3 silencing resulted in the opposite results.

Conclusions

Our results support a novel role for ELF3 as a pro-inflammatory and pro-catabolic transcriptional mediator, whose targeting in IVD tissues might be of potential therapeutic relevance in disc degeneration.

Integration of bioinformatics and multi-layered experimental validation reveals novel functions of acetylation-related genes in intervertebral disc degeneration

BACKGROUND

The molecular mechanisms underlying intervertebral disc degeneration (IDD) remain poorly understood. The purpose of this work is to elucidate key molecules and investigate the roles of acetylation-related RNAs and their associated pathways in IDD.

METHOD

Datasets GSE70362 and GSE124272 were obtained from the Gene Expression Omnibus (GEO) and combined to investigate differentially expressed genes (DEGs) associated with acetylation in IDD patients compared to healthy controls. Critical genes were pinpointed by integrating GO, KEGG and PPI networks. Furthermore, CIBERSORTx analysis was used to investigate the differences in immune cell infiltration between different groups and the biological processes (BP), cellular components (CC) and molecular functions (MF) were calculated by GSEA and GSVA. In addition, The single-cell database GSE165722 was incorporated to validate the specific expression patterns of hub genes in cells and identify distinct cell subtypes. This provides a theoretical basis for a more in-depth understanding of the roles played by critical cell subtypes in the process of IDD. Subsequently, tissues from IVD with varying degrees of degeneration were collected to corroborate the key DEGs using western blot, RT-qPCR, and immunofluorescence staining.

RESULTS

By integrating various datasets and references, we identified a total of 1620 acetylation-related genes. These genes were subjected to a combined analysis with the DEGs from the databases included in this study, resulting in the discovery of 358 acetylation-related differentially expressed genes (ARDEGs). A comparative analysis with differentially expressed genes obtained from three databases yielded 19 ARDEGs. The PPI network highlighted the top 10 genes (IL1B, LAMP1, PPIA, SOD2, LAMP2, FBL, MBP, SELL, IRF1 and KHDRBS1) based on their protein interaction relationships. CIBERSORTx immune infiltration analysis revealed a moderate positive correlation between the gene IL1β and Mast.cells.activated, as well as a similar correlation between the gene IRF1 and Mast.cells.activated. Single-cell dataset was used to identify cell types and illustrate the distribution of hub genes in different cell types. The two cell types with the highest AUCell scores (Neutrophils and Monocytes) were further explored, leading to the subdivision of Neutrophils into two new cell subtypes: S100A9-type Neutrophils and MARCKS-type Neutrophils. Monocytes were labeled as HLA-DRA9-type Monocytes and IGHG3-type Monocytes. Finally, molecular biology techniques were employed to validate the expression of the top 10 hub genes. Among them, four genes (IL1β, SOD2, LAMP2, and IRF1) were confirmed at the gene level, while two (IL1β and SOD2) were validated at the protein level.

CONCLUSION

In this study, we carried out a thorough analysis across three databases to identify and compare ARDEGs between IDD patients and healthy individuals. Furthermore, we validated a subset of these genes using molecular biology techniques on clinical samples. The identification of these differently expressed genes has the potential to offer new insights for diagnosing and treating IDD.

Diabetes Mellitus and Intervertebral Disc Degeneration: A Meta-Analysis

BACKGROUND

Diabetes mellitus (DM) has been related to a higher risk of intervertebral disc degeneration (IVDD). However, the previous studies showed inconsistent results. We performed a systematic review and meta-analysis to comprehensively investigate the association between DM and IVDD in adult population.

METHODS

Observational studies relevant to the aim of the meta-analysis were retrieved by search of electronic databases including PubMed, Web of Science, and Embase. A random-effects model was used to combine the data by incorporating the influence of between-study heterogeneity.

RESULTS

Eleven observational studies involving 2,881,170 adults were included. Among them, 1,211,880 had DM. Compared to those with normoglycemia, patients with DM were associated with a higher odds ratio of IVDD (OR: 1.68, 95% confidence interval: 1.24 to 2.29, P<0.001; I2=98%). Further sensitivity analysis excluding database studies with IVDD diagnosed via International Classification of Diseases codes showed consistent results (odds ratio: 1.47, 95% confidence interval: 1.06 to 2.02, P=0.02) with no statistical heterogeneity (I2=0%). Subgroup analyses showed a stronger association between DM and IVDD in cohort studies than that in cross-sectional studies, in studies evaluating overall IVDD than that evaluating lumbar disc degeneration, and in studies that adjusted age and body mass index than that did not (P for subgroup differences all <0.05). Subgroup analyses according to study country and quality score did not significantly affect the association.

CONCLUSIONS

DM may be associated with IVDD in adult population, which seems to be independent of age and body mass index.

Causal relationship of interferon-γ and interleukin-18 upstream of intervertebral disc degeneration pathogenesis: a two-sample Mendelian randomization study

Introduction

Intervertebral disc degeneration (IVDD) is a complex disease caused by genetic and environmental factors, but its pathogenesis is still unclear. Although studies of inflammatory cytokines have been used in recent years to unravel the biological mechanisms of a variety of diseases, such analyses have not yet been applied to IVDD. Therefore, we used a Mendelian Randomization approach to explore the potential mechanisms underlying the pathogenesis of IVDD.

Methods

We obtained GWAS data from publicly available databases for inflammatory cytokines and IVDD, respectively, and explored the causal relationship between individual inflammatory cytokines and IVDD using instrumental variable (IV) analysis. We primarily used IVW methods to assess causality, while sensitivity, heterogeneity and multidirectionality analyses were performed for positive results (p < 0.05). All analyses were performed using R software.

Results

In our study, we performed a two-sample MR analysis of 41 inflammatory cytokines to identify metabolites causally associated with IVDD. Ultimately, 2 serum metabolites associated with IVDD were identified (pval<0.05), IFN-γ and IL-18. sensitivity, heterogeneity, and Pleiotropy test analyses were performed for all results.

Conclusion

Our study identified a causal relationship between IFN-γ and IL-18 and IVDD. It is valuable for the monitoring and prevention of IVDD and the exploration of targeted drugs. However, more evidence is needed to validate our study.

Bioenergetic dysfunction in the pathogenesis of intervertebral disc degeneration

Intervertebral disc (IVD) degeneration is a frequent cause of low back pain and is the most common cause of disability. Treatments for symptomatic IVD degeneration, including conservative treatments such as analgesics, physical therapy, anti-inflammatories and surgeries, are aimed at alleviating neurological symptoms. However, there are no effective treatments to prevent or delay IVD degeneration. Previous studies have identified risk factors for IVD degeneration such as aging, inflammation, genetic factors, mechanical overload, nutrient deprivation and smoking, but metabolic dysfunction has not been highlighted. IVDs are the largest avascular structures in the human body and determine the hypoxic and glycolytic features of nucleus pulposus (NP) cells. Accumulating evidence has demonstrated that intracellular metabolic dysfunction is associated with IVD degeneration, but a comprehensive review is lacking. Here, by reviewing the physiological features of IVDs, pathological processes and metabolic changes associated with IVD degeneration and the functions of metabolic genes in IVDs, we highlight that glycolytic pathway and intact mitochondrial function are essential for IVD homeostasis. In degenerated NPs, glycolysis and mitochondrial function are downregulated. Boosting glycolysis such as HIF1α overexpression protects against IVD degeneration. Moreover, the correlations between metabolic diseases such as diabetes, obesity and IVD degeneration and their underlying molecular mechanisms are discussed. Hyperglycemia in diabetic diseases leads to cell senescence, the senescence-associated phenotype (SASP), apoptosis and catabolism of extracellualr matrix in IVDs. Correcting the global metabolic disorders such as insulin or GLP-1 receptor agonist administration is beneficial for diabetes associated IVD degeneration. Overall, we summarized the recent progress of investigations on metabolic contributions to IVD degeneration and provide a new perspective that correcting metabolic dysfunction may be beneficial for treating IVD degeneration.

Cell Reprogramming Strategies for Treating Osteoarthritis and Intervertebral Disc Degeneration

Osteoarthritis (OA) and intervertebral disc degeneration (IVDD) are the most common degenerative bone and joint diseases, posing a major threat to patients' physical and mental health due to the occurrence of chronic pain and disability. Within this context, the absence of efficacious therapies has led to a growing interest in regenerative medicine. In particular, as a method that can erase the memory of differentiation and re-endow cells with pluripotency, cell reprogramming technologies have ushered in a new era of personalized therapy, which not only show great potential for the treatment of degenerative osteoarthropathies but also promise to achieve tissue regenerative and repair. However, compared to other areas of research, reprogramming technologies to treat OA and IVDD are still in the preliminary stages and require further investigation. This paper briefly introduces the characteristics of cell reprogramming; summarizes the pathological mechanisms of reprogramming to improves energy metabolism, aging, inflammation, oxidative stress, and immune imbalance in OA and IVDD under the background of microenvironment and immunity; highlights the significant advantages of reprogramming-derived cells compared to embryonic stem cells and mesenchymal stem cells, based on these advances, providing important strategies for its development and clinical application in OA and IVDD.

Hypoxic Conditioning: A Potential Perioperative Strategy to Reduce Abdominal Aortic Occlusion-Related Injury in Mouse Proximal and Distal Organs

This study aimed to investigate the impact of abdominal aortic occlusion (AAO)- induced injury on the kidney, lower limb muscles, heart, and brain in mice, and the potential protective effects of hypoxic postconditioning (HyC). The experimental design employed an abdominal aortic occlusion (AAO) model, and involved three groups of mice: sham, AAO, and AAO+HyC. Ten minutes after the AAO model, mice were subjected to hypoxic treatment lowering oxygen concentration to 5% within 45 minutes, and then returned to a normal oxygen environment. Hematoxylin- eosin (HE) stain was used for Histopathological examinations, and Quantibody Mouse Array was used for detecting apoptosis and inflammation-related protein expression. Histopathological examinations showed that HyC mitigated pathological damage to proximal organs (kidneys and lower limb muscles), distal organs (heart and brain), and reduced inflammatory cell infiltration. Expression of apoptosis- and inflammation-related proteins in brain and heart tissues were also evaluated. HyC significantly increased cellular inhibitor of apoptosis 2 (cIAP2) in the brain and Bcl-2 and insulin-like growth factor 2 (IGF-2) in the heart. Additionally, HyC regulated the expression of several inflammation-related factors in both brain and heart tissues. Although further investigation is needed, particularly in human subjects, this study highlights the potential of HyC as a promising therapeutic strategy for reducing AAO-associated organ damage.

Confirmatory study of the usefulness of quantum molecular resonance and microdissectomy for the treatment of lumbar radiculopathy in a prospective cohort at 6 months follow-up

OBJECTIVES

Low back pain is a common musculoskeletal complaint and while prognosis is usually favorable, some patients experience persistent pain despite conservative treatment and invasive treatment to target the root cause of the pain may be necessary. The aim of this study is to evaluate patient outcomes after treatment of lumbar radiculopathy (LR) with quantum molecular resonance radiofrequency coblation disc decompression and percutaneous microdiscectomy with grasper forceps (QMRG).

METHODS

This prospective cohort study was carried out in two Spanish hospitals on 58 patients with LR secondary to a contained hydrated lumbar disc hernia or lumbar disc protrusion of more than 6 months of evolution, which persisted despite conservative treatment with analgesia, rehabilitation, and physiotherapy, and/or epidural block, in the previous 2 years. Patients were treated with QMRG and the outcomes were measured mainly using the Douleur Neuropathique en 4 Questions, Numeric Rating Scale, Oswestry Disability Index, SF12: Short Form 12 Health Survey, Patient Global Impression of Improvement, Clinical Global Impression of Improvement, and Medical Outcomes Study Sleep Scale.

RESULTS

Patients who received QMRG showed significant improvement in their baseline scores at 6 months post-treatment. The minimal clinically important difference (MCID) threshold was met by 26-98% of patients, depending on the outcome measure, for non-sleep-related outcomes, and between 17 and 62% for sleep-related outcome measures. Of the 14 outcome measures studied, at least 50% of the patients met the MCID threshold in 8 of them.

CONCLUSION

Treatment of LR with QMRG appears to be effective at 6 months post-intervention.

Genetically predicted triglycerides mediate the relationship between type 2 diabetes Mellitus and intervertebral disc degeneration

BACKGROUND

To validate the causal relationship between type 2 diabetes mellitus (T2DM) and intervertebral disc degeneration (IVDD) and to identify and quantify the role of triglycerides (TGs) as potential mediators.

METHODS

A two-sample Mendelian randomization (MR) analyses of T2DM (61,714 cases and 1178 controls) and IVDD (20,001 cases and 164,682 controls) was performed using genome-wide association studies (GWAS). Moreover, two-step MR was employed to quantify the proportionate impact of TG-mediated T2DM on IVDD.

RESULTS

MR analysis showed that T2DM increased IVDD risk (OR: 1.0466, 95% CI 1.0049-1.0899, P = 0.0278). Reverse MR analyses demonstrated that IVDD does not affect T2DM risk (P = 0.1393). The proportion of T2DM mediated through TG was 11.4% (95% CI 5.5%-17.4%).

CONCLUSION

This work further validates the causality between T2DM and IVDD, with a part of the effect mediated by TG, but the greatest impacts of T2DM on IVDD remain unknown. Further studies are needed to identify other potential mediators.

Does Vitamin K2 Influence the Interplay between Diabetes Mellitus and Intervertebral Disc Degeneration in a Rat Model?

Intervertebral disc (IVD) degeneration is a common cause of low back pain in diabetes mellitus type 2 (T2DM) patients. Its pathogenesis and the vitamin (vit.) K2 influence on this disease remain unclear. Lumbar motion segments of male Zucker Diabetes Fatty (ZDF) rats (non-diabetic [control] and diabetic; fed without or with vit. K2) were used. Femur lengths and vertebral epiphyseal cross-section areas were measured. IVDs were histopathologically examined. Protein synthesis and gene expression of isolated IVD fibrochondrocytes were analyzed. T2DM rats showed histopathological IVD degeneration. Femur lengths and epiphyseal areas were smaller in T2DM rats regardless of vit. K2 feeding. Fibrochondrocytes synthesized interleukin (IL)-24 and IL-10 with no major differences between groups. Alpha smooth muscle actin (αSMA) was strongly expressed, especially in cells of vit. K2-treated animals. Gene expression of aggrecan was low, and that of collagen type 2 was high in IVD cells of diabetic animals, whether treated with vit. K2 or not. Suppressor of cytokine signaling (Socs)3 and heme oxygenase (Hmox)1 gene expression was highest in the cells of diabetic animals treated with vit. K2. Vit. K2 influenced the expression of some stress-associated markers in IVD cells of diabetic rats, but not that of IL-10 and IL-24.

Matrix Stiffness Activating YAP/TEAD1-Cyclin B1 in Nucleus Pulposus Cells Promotes Intervertebral Disc Degeneration

Intervertebral disc degeneration is a leading cause of disability in the elderly population. Rigid extracellular matrix is a critical pathological feature of disc degeneration, leading to aberrant nucleus pulposus cells (NPCs) proliferation. However, the underlying mechanism is unclear. Here, we hypothesize that increased matrix stiffness induces proliferation and thus degenerative phenotypes of NPCs through YAP/TEAD1 signaling pathway. We established hydrogel substrates to mimic stiffness of degenerated human nucleus pulposus tissues. RNA-sequencing identified differentially expressed genes between primary rat NPCs cultured on rigid and soft hydrogels. Dual luciferase assay and gain- and loss-function experiments evaluated the correlation between YAP/TEAD1 and Cyclin B1. Furthermore, single-cell RNA-sequencing of human NPCs was performed to identify specific cell clusters with high YAP expression. Matrix stiffness increased in severely degenerated human nucleus pulposus tissues (p < 0.05). Rigid substrate enhanced rat NPCs proliferation mainly through Cyclin B1, which was directly targeted and positively regulated by YAP/TEAD1. Depletion of YAP or Cyclin B1 arrested G2/M phase progression of rat NPCs and reduced fibrotic phenotypes including MMP13 and CTGF (p < 0.05). Fibro NPCs with high YAP expression were identified in human tissues and responsible for fibrogenesis during degeneration. Furthermore, inhibition of YAP/TEAD interaction by verteporfin suppressed cell proliferation and alleviated degeneration in the disc needle puncture model (p < 0.05). Our results demonstrate that elevated matrix stiffness stimulates fibro NPCs proliferation through YAP/TEAD1-Cyclin B1 axis, indicating a therapeutic target for disc degeneration.

Cytokine Imbalance as a Biomarker of Intervertebral Disk Degeneration

The intervertebral disk degeneration (IDD) and its associated conditions are an important problem in modern medicine. The onset of IDD may be in childhood and adolescence in patients with a genetic predisposition. IDD progresses with age, leading to spondylosis, spondylarthrosis, intervertebral disk herniation, and spinal stenosis. The purpose of this review is an attempt to summarize the data characterizing the patterns of production of pro-inflammatory and anti-inflammatory cytokines in IDD and to appreciate the prognostic value of cytokine imbalance as its biomarker. This narrative review demonstrates that the problem of evaluating the contribution of pro-inflammatory and anti-inflammatory cytokines to the maintenance or alteration of cytokine balance may be a new key to unlocking the mystery of IDD development and new therapeutic strategies for the treatment of IDD in the setting of acute and chronic inflammation. The presented data support the hypothesis that cytokine imbalance is one of the most important biomarkers of IDD.