Plasmacytoid dendritic cells and memory T cells infiltrate true sequestrations stronger than subligamentous sequestrations: evidence from flow cytometric analysis of disc infiltrates

Machine learning-based diagnostic model of lymphatics-associated genes for new therapeutic target analysis in intervertebral disc degeneration

Background

Low back pain resulting from intervertebral disc degeneration (IVDD) represents a significant global social problem. There are notable differences in the distribution of lymphatic vessels (LV) in normal and pathological intervertebral discs. Nevertheless, the molecular mechanisms of lymphatics-associated genes (LAGs) in the development of IVDD remain unclear. An in-depth exploration of this area will help to reveal the biological and clinical significance of LAGs in IVDD and may lead to the search for new therapeutic targets for IVDD.

Methods

Data sets were obtained from the Gene Expression Omnibus (GEO) database. Following quality control and normalization, the datasets (GSE153761, GSE147383, and GSE124272) were merged to form the training set, with GSE150408 serving as the validation set. LAGs from GeneCards, MSigDB, Gene Ontology, and KEGG database. The Venn diagram was employed to identify differentially expressed lymphatic-associated genes (DELAGs) that were differentially expressed in the normal and IVDD groups. Subsequently, four machine learning algorithms (SVM-RFE, Random Forest, XGB, and GLM) were used to select the method to construct the diagnostic model. The receiver operating characteristic (ROC) curve, nomogram, and Decision Curve Analysis (DCA) were used to evaluate the model effect. In addition, we constructed a potential drug regulatory network and competitive endogenous RNA (ceRNA) network for key LAGs.

Results

A total of 15 differentially expressed LAGs were identified. By comparing four machine learning methods, the top five genes of importance in the XGB model (MET, HHIP, SPRY1, CSF1, TOX) were identified as lymphatics-associated gene diagnostic signatures. This signature was used to predict the diagnosis of IVDD with strong accuracy and an area under curve (AUC) value of 0.938. Furthermore, the diagnostic model was validated in an external dataset (GSE150408), with an AUC value of 0.772. The nomogram and DCA further prove that the diagnosis model has good performance and predictive value. Additionally, drug regulatory networks and ceRNA networks were constructed, revealing potential therapeutic drugs and post-transcriptional regulatory mechanisms.

Conclusion

We developed and validated a lymphatics-associated genes diagnostic model by machine learning algorithms that effectively identify IVDD patients. These five key LAGs may be potential therapeutic targets for IVDD patients.

Investigating the characteristics of mild intervertebral disc degeneration at various age stages using single-cell genomics

Introduction: Intervertebral disc degeneration often occurs in the elderly population, but in recent years, there has been an increasing incidence of disc degeneration in younger individuals, primarily with mild degeneration. Methods: In order to explore the underlying mechanisms of disc degeneration in both young and aging individuals, we collected four types of nucleus pulposus (NP) single-cell sequencing samples for analysis based on Pfirrmann grading: normal-young (NY) (Grade I), normal-old (NO) (Grade I), mild degenerative-young (MY) (Grade II-III), and mild degenerative-old (MO) (Grade II-III). Results: We found that most NP cells in NO and MY samples exhibited oxidative stress, which may be important pathogenic factors in NO and MY groups. On the other hand, NP cells in MO group exhibited endoplasmic reticulum stress. In terms of inflammation, myeloid cells were mainly present in the degenerative group, with the MY group showing a stronger immune response compared to the MO group. Interestingly, dendritic cells in the myeloid lineage played a critical role in the process of mild degeneration. Discussion: Our study investigated the molecular mechanisms of intervertebral disc degeneration from an age perspective, providing insights for improving treatment strategies for patients with disc degeneration at different age groups.

ANGPTL4 May Regulate the Crosstalk Between Intervertebral Disc Degeneration and Type 2 Diabetes Mellitus: A Combined Analysis of Bioinformatics and Rat Models

Introduction

The crosstalk between intervertebral disc degeneration (IVDD) and type 2 diabetes mellitus (T2DM) has been investigated. However, the common mechanism underlying this phenomenon has not been clearly elucidated. This study aimed to explore the shared gene signatures of IVDD and T2DM.

Methods

The expression profiles of IVDD (GSE27494) and T2DM (GSE20966) were acquired from the Gene Expression Omnibus database. Five hub genes including ANGPTL4, CCL2, CCN3, THBS2, and INHBA were preliminarily screened. GO (Gene Ontology) enrichment analysis, functional correlation analysis, immune filtration, Transcription factors (TFs)-mRNA-miRNA coregulatory network, and potential drugs prediction were performed following the identification of hub genes. RNA sequencing, in vivo and in vitro experiments on rats were further performed to validate the expression and function of the target gene.

Results

Five hub genes (ANGPTL4, CCL2, CCN3, THBS2, and INHBA) were identified. GO analysis demonstrated the regulation of the immune system, extracellular matrix (ECM), and SMAD protein signal transduction. There was a strong correlation between hub genes and different functions, including lipid metabolism, mitochondrial function, and ECM degradation. The immune filtration pattern grouped by disease and the expression of hub genes showed significant changes in the immune cell composition. TFs-mRNA-miRNA co-expression networks were constructed. In addition, pepstatin showed great drug-targeting relevance based on potential drugs prediction of hub genes. ANGPTL4, a gene that mediates the inhibition of lipoprotein lipase activity, was eventually determined after hub gene screening, validation by different datasets, RNA sequencing, and experiments.

Discussion

This study screened five hub genes and ANGPTL4 was eventually determined as a potential target for the regulation of the crosstalk in patients with IVDD and T2DM.

Early Versus Delayed Microdiscectomy for Chronic Sciatica Lasting 4-12 Months Secondary to Lumbar Disc Herniation: A Secondary Analysis of a Randomized Controlled Trial

OBJECTIVES

To compare the effect of delaying surgery on clinical outcome in patients with chronic sciatica secondary to lumbar disc herniation.

METHODS

Patients with sciatica lasting 4-12 months and lumbar disc herniation at the L4-L5 or L5-S1 level were randomized to undergo microdiscectomy (early surgery) or to receive 6 months of nonoperative treatment followed by surgery if needed (delayed surgery). Outcomes were leg pain, Oswestry Disability Index score (ODI), back pain, SF-36 physical component (PCS) and mental component (MCS) summary scores, employment, and satisfaction measured preoperatively and at 6 weeks, 3 months, 6 months, and 1 year after surgery.

RESULTS

Of the 64 patients in the early surgery group, 56 underwent microdiscectomy an average of 3 ± 2 weeks after enrollment. Of the 64 patients randomized to nonoperative care, 22 patients underwent delayed surgery an average of 53 ± 24 weeks after enrollment. The early surgery group experienced less leg pain than the delayed surgery group, which was the primary outcome, at 6 months after surgery (early surgery 2.8 ± .4 vs delayed surgery 4.8 ± .7; difference, 2.0; 95% confidence interval, .5-3.5). The overall estimated mean difference between groups significantly favored early surgery for leg pain, ODI, SF36-PCS, and back pain. The adverse event rate was similar between groups.

CONCLUSIONS

Patients presenting with chronic sciatica treated with delayed surgery after prolonging standardized non-operative care have inferior outcomes compared to those that undergo expedited surgery.

Single-cell RNA-seq analysis reveals that immune cells induce human nucleus pulposus ossification and degeneration

Background and aims

Determining the transcriptomes and molecular mechanism underlying human degenerative nucleus pulposus (NP) is of critical importance for treating intervertebral disc degeneration (IDD). Here, we aimed to elucidate the detailed molecular mechanism of NP ossification and IDD using single-cell RNA sequencing.

Methods

Single-cell RNA-seq and bioinformatic analysis were performed to identify NP cell populations with gene signatures, biological processes and pathways, and subpopulation analysis, RNA velocity analysis, and cell-to-cell communication analysis were performed in four IDD patients. We also verified the effects of immune cells on NP ossification using cultured NP cells and a well-established rat IDD model.

Results

We identified five cell populations with gene expression profiles in degenerative NP at single-cell resolution. GO database analysis showed that degenerative NP-associated genes were mainly enriched in extracellular matrix organization, immune response, and ossification. Gene set enrichment analysis showed that rheumatoid arthritis signaling, antigen processing and presentation signaling were activated in the blood cell cluster. We revealed that stromal cells, which are progenitor cells, differentiated toward an ossification phenotype and delineated interactions between immune cells (macrophages and T cells) and stromal cells. Immune factors such as TNF-α, CD74 and CCL-3 promoted the differentiation of stromal cells toward an ossification phenotype in vitro. Blocking TNF-α with a specific inhibitor successfully reversed NP ossification and modified NP morphology in vivo.

Conclusion

Our study revealed an increase in macrophages and T cells in degenerative NP, which induced stromal cell differentiation toward an ossification phenotype, and contributed to the identification of a novel therapeutic target to delay IDD.

Identifification and validation of ferroptosis signatures and immune infifiltration characteristics associated with intervertebral disc degeneration

Ferroptosis and immune infiltration play an important role in the pathogenesis of intervertebral disc degeneration (IDD). However, there is still a lack of comprehensive analysis on the interaction between ferroptosis-related genes (FRGs) and immune microenvironment in IDD patients. Therefore, this study aims to explore the correlation between FRGs characteristics and immune infiltration in the progression of IDD. The expression profiles (GSE56081 and GSE70362) and FRGs were downloaded from the comprehensive gene expression omnibus (GEO) and FerrDb database, respectively, and the differences were analyzed using R. The intersection of IDD related differential genes (DEGs) and FRGs was taken as differentially expressed FRGs (DE-FRGs) and GO and KEGG enrichment analysis was conducted. Then, we used least absolute shrinkage and selection operator (LASSO) regression algorithm and support vector machine (SVM) algorithm to screen feature genes and draw ROC curve judge the diagnostic value of key DE-FRGs. Then CIBERSORT algorithm is used to evaluate the infiltration of immune cells and analyze the correlation between key DE-FRGs and immune infiltration. Based on the analysis results, we conducted single gene GSEA analysis on key DE-FRGs. RT-PCR and immunohistochemistry further verified the clinical value of the results of biochemical analysis and screening. Seven key DE-FRGs were screened, including the upregulated genes NOX4 and PIR, and the downregulated genes TIMM9, ATF3, ENPP2, FADS2 and TFAP2A. Single gene GSEA analysis further elucidates the role of DE-FRGs in IDD associated with ferroptosis. Correlation analysis showed that seven key DE-FRGs were closely related to immune infiltration in the development of IDD. Finally, RT-PCR and immunohistochemical staining showed that NOX4, ENPP2, FADS2 and TFAP2A were statistically significant differences. In this study, we explored the connection between ferroptosis related characteristics and immune infiltration in IDD, and confirmed that NOX4, ENPP2, FADS2, and TFAP2A may become biomarkers and potential therapeutic targets for IDD.

Update on the roles of macrophages in the degeneration and repair process of intervertebral discs

Intervertebral disc (IVD) degeneration is the common cause of lumbar degenerative diseases, causing severe social and economic burden. The process of IVD degeneration involves a complex of pathologic changes on both extracellular matrix degradation and resident cell apoptosis. In recent years, there is increasing evidence that macrophages play vital roles during the damage and repair process of IVD degeneration. Nevertheless, the interactions between macrophages and IVD are not well understood, even if the IVD has long been regarded as the immune privileged site. Therefore, this review mainly focuses on the progress and obstacles of studies investigating the blood supply, immune response and especially macrophages during the IVD degeneration process.

Heterogeneous macrophages contribute to the pathology of disc herniation induced radiculopathy

BACKGROUND CONTEXT

Macrophages play important roles in the progression of intervertebral disc herniation and radiculopathy.

PURPOSE

To better understand the roles of macrophages in this process, we developed a new mouse model that mimics human radiculopathy.

STUDY DESIGN/SETTING

A preclinical randomized animal study.

METHODS

Three types of surgeries were performed in randomly assigned Balb/c mice. These were spinal nerve exposure, traditional anterior disc puncture, and lateral disc puncture with nerve exposure (n=16/group). For the nerve exposure group, the left L5 spinal nerve was exposed without disc injury. For the traditional anterior puncture, L5/6 disc was punctured by an anterior approach as previously established. For lateral puncture with nerve exposure, the left L5 spinal nerve was exposed by removing the psoas major muscle fibers, and the L5/6 disc was punctured laterally on the left side with a 30G needle, allowing the nucleus to protrude toward the L5 spinal nerve. Mechanical hyperalgesia (pain sensitivity) of hind paws was assessed with electronic von Frey assay on alternative day for up to 2 weeks. MRI, histology, and immunostaining were performed to confirm disc herniation and inflammation.

RESULTS

Ipsilateral pain in the lateral puncture with nerve exposure group was significantly greater than the other groups. Pro-inflammatory cytokines IL-1β and IL-6 were markedly elevated at the hernia sites of both puncture groups and the spinal nerve of lateral puncture with never exposure group on postoperative day 7. Heterogeneous populations of macrophages were detected in the infiltration tissue of this mouse model and in tissue from patients undergone discectomy.

CONCLUSIONS

We have established a new mouse model that mimics human radiculopathy and demonstrated that a mixed phenotype of macrophages contribute to the pathogenesis of acute discogenic radiculopathy.

CLINICAL SIGNIFICANCE

This study provides a clinically relevant in vivo animal model to elucidate complex interactions of disc herniation and radicular pain, which may present opportunities for the development of macrophage-anchored therapeutics to manage radiculopathy.

The inflammatory response in the regression of lumbar disc herniation

Lumbar disc herniation (LDH) is highly associated with inflammation in the context of low back pain. Currently, inflammation is associated with adverse symptoms related to the stimulation of nerve fibers that may lead to pain. However, inflammation has also been indicated as the main factor responsible for LDH regression. This apparent controversy places inflammation as a good prognostic indicator of spontaneous regression of LDH. This review addresses the molecular and cellular mechanisms involved in LDH regression, including matrix remodeling and neovascularization, in the scope of the clinical decision on conservative versus surgical intervention. Based on the evidence, a special focus on the inflammatory response in the LDH context is given, particularly in the monocyte/macrophage role. The phenomenon of spontaneous regression of LDH, extensively reported in the literature, is therefore analyzed here under the perspective of the modulatory role of inflammation.