Low back pain patients with Modic type 1 changes exhibit distinct bacterial and non-bacterial subtypes

Relationship Between Lumbar Multifidus Morphometry and Pain/Disability in Individuals With Chronic Nonspecific Low Back Pain After Considering Demographics, Fear-Avoidance Beliefs, Insomnia, and Spinal Degenerative Changes

Background

Although individuals with chronic low back pain (CLBP) show increased fatty infiltration in the lumbar multifidus muscle (LMM), it remains unclear whether LMM changes are related to clinical outcomes (such as pain and disability) after considering confounders (spinal phenotypes, fear-avoidance beliefs [FABs] and insomnia). This study examined: (1) differences in confounders and LMM characteristics between individuals with and without CLBP; and (2) associations between confounders, LMM parameters, and clinical outcomes in the CLBP group alone.

Methods

Participants (CLBP = 70 and asymptomatic people = 67) underwent lumbar magnetic resonance imaging. Outcome measures comprised the numeric pain rating scale, the Roland-Morris Disability Questionnaire, the Fear-Avoidance Beliefs Questionnaire (FABQ), and the Insomnia Severity Index (ISI) Scale. LMM morphometry at L3-S1 (cross-sectional area, total volume, and fatty infiltration) was measured using a customized MATLAB program. Spinal phenotypes (disc degeneration, high-intensity zones, Modic changes [MCs], Schmorl's nodes, facet joint degeneration [FJD], and facet tropism [FT]) were scored. The between-group differences were analyzed using linear mixed models and chi-squared/Fisher's exact tests. Univariate and multivariate analyses evaluated associations between clinical outcomes and other outcome measures in the CLBP group.

Results

The CLBP group demonstrated more severe disc degeneration and FJD at all levels, and greater FT at L5/S1 than asymptomatic participants (p < 0.05). The average LMM total volume at L3/4 and the percentage of fatty infiltration in LMM in the L3-S1 region were greater in the CLBP group than in asymptomatic counterparts (p < 0.05). The presence of MC at L4 and FJD at L4/5 and L4-S1 was significantly related to pain intensity in the CLBP group. Similarly, FABQ-Work and ISI scores were significantly related to pain intensity (explaining 37% of the variance in pain).

Conclusions

The CLBP group displays more fatty infiltration in the LMM, but their LMM morphometric parameters are unrelated to pain/disability after considering spinal phenotypes, FABs, and insomnia.

In-silico proteomic analysis of the role of IL-4 and IL-10 in IVD degeneration: Protein-protein interaction networks for candidate prioritisation

Protein-protein interaction (PPI) networks provide a static map of functional protein interactions, which when combined with algorithms, can prioritize key protein candidates which experimental studies cannot capture. This study, aimed to construct knowledge-based nucleus pulposus (NP)-specific PPI networks which could be deployed to investigate complex protein interactions in human NP cells and tissues following IL-4 and IL-10 stimulation. NP-specific PPI networks were developed based on mass spectrometry (MS) and secretome datasets from human NP cells. These networks were validated using in vitro and ex vivo experimental data sets. Genes Underlying Inheritance Linked Disorders (GUILD) genome-wide network-based prioritization framework was employed for protein candidate prediction under no treatment baseline and IL-4, IL-10 and IL-1β single or combined stimulating scenarios. These secretome-based in vitro PPI networks were able to reproduce the no-treatment candidate prioritization baseline. Whereby within NP cells from discs isolated due to traumatic injury biglycan was identified whilst in degenerate samples decorin was highlighted. Furthermore, experimentally observed IL-4 pleiotropic behaviour was predicted by IL-1 receptor-like 1 prioritization. PPI network-based IL-4 and IL-10 conditions offered novel insights of potential candidates, including collagen IV and fibroblast growth factor intracellular binding protein (FIBP) as key candidates within IL-4 activation pathways, whereas urocortin 3 and neural growth factor were identified following IL-10 stimulation. Additionally, MS based PPI network propagation offered a more extensive, module-based structure networks with lower edge degree and biological variability. Overall, multiple proteomic experimental approaches are required to successfully validate in-silico prediction models to understand the complex interactions between the plethora of proteins involved in IVD degeneration.

Modic changes: From potential molecular mechanisms to future research directions (Review)

Low back pain (LBP) is a leading cause of disability worldwide. Although not all patients with Modic changes (MCs) experience LBP, MC is often closely associated with LBP and disc degeneration. In clinical practice, the focus is usually on symptoms related to MC, which are hypothesized to be associated with LBP; however, the link between MC and nerve compression remains unclear. In cases of intervertebral disc herniation, nerve compression is often the definitive cause of symptoms. Recent advances have shed light on the pathophysiology of MC, partially elucidating its underlying mechanisms. The pathogenesis of MC involves complex bone marrow‑disc interactions, resulting in bone marrow inflammation and edema. Over time, hematopoietic cells are gradually replaced by adipocytes, ultimately resulting in localized bone marrow sclerosis. This process creates a barrier between the intervertebral disc and the bone marrow, thereby enhancing the stability of the vertebral body. The latest understanding of the pathophysiology of MC suggests that chronic inflammation plays a significant role in its development and hypothesizes that the complement system may contribute to its pathological progression. However, this hypothesis requires further research to be confirmed. The present review we proposed a pathological model based on current research, encompassing the transition from Modic type 1 changes (MC1) to Modic type 2 changes (MC2). It discussed key cellular functions and their alterations in the pathogenesis of MC and outlined potential future research directions to further elucidate its mechanisms. Additionally, it reviewed the current clinical staging and pathogenesis of MC, recommended the development of an updated staging system and explored the prospects of integrating emerging artificial intelligence technologies.

Inflammation and macrophage polarization are associated with Modic change type in lumbar radiculopathy

Introduction

Lumbar disc herniation (LDH) typically manifests as sciatica, attributed to nerve root mechanical compression and/or inflammation. Modic changes (MC), classified as type I or type II, are deemed to represent endplate vascular insufficiency and are hypothesized to create an inflammatory environment. Macrophages infiltrating disc tissue can be polarized into pro-inflammatory M1 or anti-inflammatory M2 phenotypes.

Research question

This study aims to investigate the interplay among inflammatory cells, including M1 and M2 macrophages, Modic Changes, and hernia size and type in patients suffering from sciatica due to a LDH.

Material and methods

This prospective cohort study selected patients undergoing microdiscectomy for LDH. Macrophage infiltration (CD68, CD192, CD163), MC classification on MRI, and hernia parameters were analyzed.

Results

132 out of 187 patients demonstrated macrophages in the lumbar disc tissue. Most samples demonstrated severe inflammation (50 %), and most macrophages were of the M1 phenotype (48 %). MC were present in 45 % of patients, and only 19 % of these demonstrated MC type I. MC type I were highly associated with both severe (p = 0.016) and M1 macrophage-dominant inflammation (p = 0.048). Larger and non-contained herniations associated with increased inflammation (p = 0.029/p = 0.002), while larger herniations associated with the presence of MC type II (p = 0.027).

Discussion and conclusions

This study elucidates a close association of MC type I and M1 macrophage. MC type II were observed more often in patients with larger HNPs. This is indicative for MC typing as an important factor in prediction modelling and it suggests the potential for personalized treatment strategies.

Role of macrophage in intervertebral disc degeneration

Intervertebral disc degeneration is a degenerative disease where inflammation and immune responses play significant roles. Macrophages, as key immune cells, critically regulate inflammation through polarization into different phenotypes. In recent years, the role of macrophages in inflammation-related degenerative diseases, such as intervertebral disc degeneration, has been increasingly recognized. Macrophages construct the inflammatory microenvironment of the intervertebral disc and are involved in regulating intervertebral disc cell activities, extracellular matrix metabolism, intervertebral disc vascularization, and innervation, profoundly influencing the progression of disc degeneration. To gain a deeper understanding of the inflammatory microenvironment of intervertebral disc degeneration, this review will summarize the role of macrophages in the pathological process of intervertebral disc degeneration, analyze the regulatory mechanisms involving macrophages, and review therapeutic strategies targeting macrophage modulation for the treatment of intervertebral disc degeneration. These insights will be valuable for the treatment and research directions of intervertebral disc degeneration.

Preclinical development and characterisation of PP353, a formulation of linezolid for intradiscal administration

Introduction

Bacterial infection of the intervertebral disc can lead to vertebral endplate edema known as Modic changes, with associated chronic low back pain. Oral antimicrobial therapy has shown efficacy but relies on prolonged dosing and may not be optimal in terms of patient outcome, side effects, or antibiotic stewardship. There is no antibiotic formulation approved for intradiscal administration. Here, we describe the development and preclinical characterization of a formulation of linezolid, a suspension of 50 mg/mL micronized powder, for intradiscal administration.

Methods

Micronization, particle size analysis, Franz cell diffusion assays, ex vivo bioassay, and estimates of gelling temperature were used to optimize the composition and properties of the formulation. Performance of the formulation was assessed using sheep to characterize the pharmacokinetics and a model of intradiscal infection was developed to demonstrate efficacy. Suitability for human administration was demonstrated in a Good Laboratory Practice (GLP) local tolerance study.

Results

Micronized linezolid, formulated as a powder suspension using a vehicle containing poloxamer 407 and iohexol, provided a temperature-dependent radio-opaque gel that was suitable for image-guided percutaneous intradiscal administration. Efficacy in a sheep model of intradiscal Staphylococcus aureus infection was demonstrated. The formulation provides a high level of sheep disc tissue exposure, with Cmax of 6500 μg/g and limited systemic exposure, with a plasma Cmax of 0.04 μg/mL per 0.1 mL dose (5 mg of linezolid). Deconvolution of plasma linezolid pharmacokinetics correlated with linezolid remaining in the disc over time. Observations from a GLP local tolerance study with the linezolid formulation were of a minor nature and related to the intradiscal administration procedure.

Conclusions

Linezolid can be formulated for image-guided percutaneous intradiscal administration. The formulation is now in a Phase 1b clinical trial to evaluate safety, pharmacokinetics, and efficacy in patients with CLBP and suspected bacterial infection.

Proteomic analysis of serum in a population-based cohort did not reveal a biomarker for Modic changes

Introduction

Modic changes (MC) are bone marrow lesions of vertebral bones, which can be detected with magnetic resonance imaging (MRI) adjacent to degenerated intervertebral discs. Defined by their appearance on T1 and T2 weighted images, there are three interconvertible types: MC1, MC2, and MC3. The inter-observer variability of the MRI diagnosis is high, therefore a diagnostic serum biomarker complementing the MRI to facilitate diagnosis and follow-up would be of great value.

Methods

We used a highly sensitive and reproducible proteomics approach: DIA/SWATH-MS to find serum biomarkers in a subset of the Northern Finland Birth Cohort 1966. Separately, we measured a panel of factors involved in inflammation and angiogenesis to confirm some potential biomarkers published before with an ELISA-based method called V-Plex.

Results

We found neither an association between the serum concentrations of the proteins detected with DIA/SWATH-MS with the presence of MC, nor a correlation with the size of the MC lesions. We did not find any association between the factors measured with the V-Plex and the presence of MC or their size.

Conclusion

Altogether, our study suggests that a robust and generally usable biomarker to facilitate the diagnosis of MC cannot readily be found in serum.

The Expression of Toll-like Receptors in Cartilage Endplate Cells: A Role of Toll-like Receptor 2 in Pro-Inflammatory and Pro-Catabolic Gene Expression

INTRODUCTION

The vertebral cartilage endplate (CEP), crucial for intervertebral disc health, is prone to degeneration linked to chronic low back pain, disc degeneration, and Modic changes (MC). While it is known that disc cells express toll-like receptors (TLRs) that recognize pathogen- and damage-associated molecular patterns (PAMPs and DAMPs), it is unclear if CEP cells (CEPCs) share this trait. The CEP has a higher cell density than the disc, making CEPCs an important contributor. This study aimed to identify TLRs on CEPCs and their role in pro-inflammatory and catabolic gene expression.

METHODS

Gene expression of TLR1-10 was measured in human CEPs and expanded CEPCs using quantitative polymerase chain reaction. Additionally, surface TLR expression was measured in CEPs grouped into non-MC and MC. CEPCs were stimulated with tumor necrosis factor alpha, interleukin 1 beta, small-molecule TLR agonists, or the 30 kDa N-terminal fibronectin fragment. TLR2 signaling was inhibited with TL2-C29, and TLR2 protein expression was measured with flow cytometry.

RESULTS

Ex vivo analysis found all 10 TLRs expressed, while cultured CEPCs lost TLR8 and TLR9 expression. TLR2 expression was significantly increased in MC1 CEPCs, and its expression increased significantly after pro-inflammatory stimulation. Stimulation of the TLR2/6 heterodimer upregulated TLR2 protein expression. The TLR2/1 and TLR2/6 ligands upregulated pro-inflammatory genes and matrix metalloproteases (MMP1, MMP3, and MMP13), and TLR2 inhibition inhibited their upregulation. Endplate resorptive capacity of TLR2 activation was confirmed in a CEP explant model.

CONCLUSIONS

The expression of TLR1-10 in CEPCs suggests that the CEP is susceptible to PAMP and DAMP stimulation. Enhanced TLR2 expression in MC1, and generally in CEPCs under inflammatory conditions, has pro-inflammatory and pro-catabolic effects, suggesting a potential role in disc degeneration and MC.

Can Hematological Inflammatory Indices Be Used to Differentiate Modic Type 1 Changes from Brucella Spondylodiscitis?

Background and Objectives: Differentiation between brucella spondylodiscitis and Modic type I changes (MC1) includes difficulties. Hematological inflammatory indices (HII) such as neutrophil to lymphocyte ratio (NLR) and aggregate index of systemic inflammation (AISI) are suggested as indicators of inflammation and infection and have diagnostic, prognostic, and predictive roles in various diseases. This study aimed to evaluate differences between brucella spondylodiscitis and MC1 in terms of HII. Materials and Methods: Thirty-five patients with brucella spondylodiscitis and thirty-seven with MC1 were enrolled in the study. Brucella spondylodiscitis and MC1 were diagnosed by microbiological, serological, and radiological diagnostic tools. HII (NLR, MLR, PLR, NLPR, SII, SIRI, AISI) were derived from baseline complete blood count. Results: The two groups were similar for age (p = 0.579) and gender (p = 0.092), leukocyte (p = 0.127), neutrophil (p = 0.366), lymphocyte (p = 0.090), and monocyte (p = 0.756) scores. The Brucella spondylodiscitis group had significantly lower pain duration (p < 0.001), higher CRP and ESR levels (p < 0.001), and lower platelet count (p = 0.047) than the MC1 group. The two groups had similarity in terms of HII: NLR (p = 0.553), MLR (p = 0.294), PLR (p = 0.772), NLPR (p = 0.115), SII (p = 0.798), SIRI (p = 0.447), and AISI (p = 0.248). Conclusions: Increased HII can be used to differentiate infectious and non-infectious conditions, but this may be invalid in brucellosis. However, pain duration, CRP and ESR levels, and platelet count may be useful to distinguish brucella spondylodiscitis from MC1.

Intervertebral disc microbiome in Modic changes: Lack of result replication underscores the need for a consensus in low-biomass microbiome analysis

Introduction

The emerging field of the disc microbiome challenges traditional views of disc sterility, which opens new avenues for novel clinical insights. However, the lack of methodological consensus in disc microbiome studies introduces discrepancies. The aims of this study were to (1) compare the disc microbiome of non-Modic (nonMC), Modic type 1 change (MC1), and MC2 discs to findings from prior disc microbiome studies, and (2) investigate if discrepancies to prior studies can be explained with bioinformatic variations.

Methods

Sequencing of 16S rRNA in 70 discs (24 nonMC, 25 MC1, and 21 MC2) for microbiome profiling. The experimental setup included buffer contamination controls and was performed under aseptic conditions. Methodology and results were contrasted with previous disc microbiome studies. Critical bioinformatic steps that were different in our best-practice approach and previous disc microbiome studies (taxonomic lineage assignment, prevalence cut-off) were varied and their effect on results were compared.

Results

There was limited overlap of results with a previous study on MC disc microbiome. No bacterial genera were shared using the same bioinformatic parameters. Taxonomic lineage assignment using "amplicon sequencing variants" was more sensitive and detected 48 genera compared to 22 with "operational taxonomic units" (previous study). Increasing filter cut-off from 4% to 50% (previous study) reduced genera from 48 to 4 genera. Despite these differences, both studies observed dysbiosis with an increased abundance of gram-negative bacteria in MC discs as well as a lower beta-diversity. Cutibacterium was persistently detected in all groups independent of the bioinformatic approach, emphasizing its prevalence.

Conclusion

There is dysbiosis in MC discs. Bioinformatic parameters impact results yet cannot explain the different findings from this and a previous study. Therefore, discrepancies are likely caused by different sample preparations or true biologic differences. Harmonized protocols are required to advance understanding of the disc microbiome and its clinical implications.

Bacterial growth in patients with low back pain and Modic changes: protocol of a multicentre, case-control biopsy study

INTRODUCTION

Bacterial infection and Modic changes (MCs) as causes of low back pain (LBP) are debated. Results diverged between two randomised controlled trials examining the effect of amoxicillin with and without clavulanic acid versus placebo on patients with chronic LBP (cLBP) and MCs. Previous biopsy studies have been criticised with regard to methods, few patients and controls, and insufficient measures to minimise perioperative contamination. In this study, we minimise contamination risk, include a control group and optimise statistical power. The main aim is to compare bacterial growth between patients with and without MCs.

METHODS AND ANALYSIS

This multicentre, case-control study examines disc and vertebral body biopsies of patients with cLBP. Cases have MCs at the level of tissue sampling, controls do not. Previously operated patients are included as a subgroup. Tissue is sampled before antibiotic prophylaxis with separate instruments. We will apply microbiological methods and histology on biopsies, and predefine criteria for significant bacterial growth, possible contamination and no growth. Microbiologists, surgeons and pathologist are blinded to allocation of case or control. Primary analysis assesses significant growth in MC1 versus controls and MC2 versus controls separately. Bacterial disc growth in previously operated patients, patients with large MCs and growth from the vertebral body in the fusion group are all considered exploratory analyses.

ETHICS AND DISSEMINATION

The Regional Committees for Medical and Health Research Ethics in Norway (REC South East, reference number 2015/697) has approved the study. Study participation requires written informed consent. The study is registered at ClinicalTrials.gov (NCT03406624). Results will be disseminated in peer-reviewed journals, scientific conferences and patient fora.

TRIAL REGISTRATION NUMBER

NCT03406624.

The role of the complement system in disc degeneration and Modic changes

Disc degeneration and vertebral endplate bone marrow lesions called Modic changes are prevalent spinal pathologies found in chronic low back pain patients. Their pathomechanisms are complex and not fully understood. Recent studies have revealed that complement system proteins and interactors are dysregulated in disc degeneration and Modic changes. The complement system is part of the innate immune system and plays a critical role in tissue homeostasis. However, its dysregulation has also been associated with various pathological conditions such as rheumatoid arthritis and osteoarthritis. Here, we review the evidence for the involvement of the complement system in intervertebral disc degeneration and Modic changes. We found that only a handful of studies reported on complement factors in Modic changes and disc degeneration. Therefore, the level of evidence for the involvement of the complement system is currently low. Nevertheless, the complement system is tightly intertwined with processes known to occur during disc degeneration and Modic changes, such as increased cell death, autoantibody production, bacterial defense processes, neutrophil activation, and osteoclast formation, indicating a contribution of the complement system to these spinal pathologies. Based on these mechanisms, we propose a model how the complement system could contribute to the vicious cycle of tissue damage and chronic inflammation in disc degeneration and Modic changes. With this review, we aim to highlight a currently understudied but potentially important inflammatory pathomechanism of disc degeneration and Modic changes that may be a novel therapeutic target.