Cellular Senescence in Intervertebral Disc Aging and Degeneration: Molecular Mechanisms and Potential Therapeutic Opportunities

Macrophage Changes and High-Throughput Sequencing in Aging Mouse Intervertebral Disks

Background

Intervertebral disk (IVD) degeneration is associated with lower back pain and aging; however, the mechanisms underlying age-related changes and the changes in macrophage polarization in aging intervertebral disks require further elucidation. The aim of this study was to evaluate changes in macrophages, the differential expression of senescence genes, and their relationship with hub genes in IVDs during aging in mice.

Methods

Twenty-eight male wild C57 mice aged 4 weeks were divided into two groups. Four mice per group were selected for high-throughput sequencing and 10 for tail IVD immunohistochemical analysis. Adult and aged mouse IVD specimens were stained with hematoxylin-eosin, Fast Green, and Alcian Blue to determine collagen (Col) 1, Col2, proteoglycan, P16, P21, P53, CD11b, CD86, CD206, IL-1, TGF-β, and IL-4 expression. High-throughput sequencing was performed on adult and aged mouse IVD tissues.

Results

Aged mouse IVDs showed reduced height and marked degeneration, with decreased Col2 and proteoglycan expression and increased Col1 expression. The expression of senescence markers, senescence-associated IL-1, TGF-β, and IL-4, and macrophage-related markers, CD11b, CD86, and CD206, increased markedly with age. High-throughput sequencing revealed 1975 differentially expressed genes in adult and aged mice, with 797 genes showing upregulated expression (top five: Kcna7, Mmp9, Panx3, Myl10, and Bglap) and 1178 showing downregulated expression (top five: Srd5a2, Slc38a5, Gm47283, Npy, and Pcdh8). Gene Ontology and pathway enrichment analyses highlighted aging-related cellular components, biological processes, and metabolic pathways. The identified hub genes included Cox5a, Ndufs6, and Ndufb9.

Conclusions

Disk senescence and reduced height in aged mice are linked to upregulated expression of senescence-associated phenotypes and macrophage polarization markers. These findings suggest that macrophages and differential gene expression play key roles in age-related IVD degeneration, indicating that they can be used as potential targets for therapeutic intervention.

Baicalein-loaded porous silk fibroin microspheres modulate the senescence of nucleus pulposus cells through the NF-κB signaling pathway

Intervertebral disc degeneration (IVDD), an age-associated degenerative condition, significantly contributes to low back pain, thereby adversely affecting individual health and quality of life, while also imposing a substantial societal burden. Baicalein, a natural flavonoid derived from Scutellaria baicalensis Georgi, demonstrates a range of pharmacological activities, including antioxidant, anti-inflammatory, anti-tumor, and antibacterial properties. This positions it as a promising candidate for the treatment of IVDD through intradiscal drug delivery. However, local degenerative processes and the inherently low fluid exchange within the intervertebral disk are likely to affect drug retention. In this study, we developed baicalein-loaded porous silk fibroin microspheres to extend the drug release profile. Baicalein-loaded porous silk fibroin microspheres were prepared by electrostatic spraying. Subsequent characterization and evaluation of their intrinsic properties were conducted using nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), transmission electron microscopy(TEM), and fourier transform infrared spectroscopy (FTIR). The findings of our study demonstrated that baicalein-loaded porous silk fibroin microspheres exhibited a sustained drug release profile. Consequently, these microspheres effectively inhibited the senescence of nucleus pulposus cells (NPCs), which induced by Tert-butyl hydroperoxide (TBHP). Mechanistic investigation utilizing transcriptome sequencing revealed that the NF-κB signaling pathway is involved in the effects of baicalein-loaded porous silk fibroin microspheres. Furthermore, our findings demonstrated that the microspheres exhibited excellent biocompatibility in rats subcutaneous implantation model. Collectively, we developed a promising biomaterial for the treatment of IVDD, warranting further systematic preclinical investigation.

Guiqi Huoxue capsule alleviates cervical spondylosis in rats: Insights from 16S rRNA sequencing, lipidomics, and network pharmacology

ETHNOPHARMACOLOGICAL RELEVANCE

Cervical spondylosis (CS) is a common condition primarily caused by intervertebral disc degeneration (IVDD), adversely affecting quality of life. Traditional Chinese medicine believes that Qi deficiency and blood stasis are the main pathogenesis of CS. Guiqi Huoxue capsule (GQHX) has the effect of beneficial Qi tonifying kidneys and promoting blood circulation, which is mainly used in the clinical treatment of CS (Qi deficiency and blood stasis syndrome). However, the underlying mechanism of action has not been reported and clarified.

AIM OF THE STUDY

The aim of this study was to investigate the efficacy and underlying mechanisms of GQHX in CS rats.

MATERIALS AND METHODS

The CS rat model (Qi deficiency and blood stasis syndrome) was established by using IVDD and Ovariectomy (OVX) surgeries, along with qi deficiency and blood stasis modeling. The effects of GQHX on CS rats were evaluated by behavioral tests, blood indexes, H&E staining, and other means. Fatty acid profiles and gut microbiota were analyzed using lipidomics and 16S rRNA sequencing. The mechanism of action of GQHX was investigated by network pharmacology and western blotting.

RESULTS

GQHX reduced the symptoms of CS rats as confirmed by behavioral indicators, serum markers, and other measures of efficacy. Meanwhile, 16S rRNA sequencing and lipidomics results showed that GQHX regulated the abundance of Blautia and Muribaculaceae, influencing the production of various fatty acids (e.g. isobutyric, isovaleric, and linoleic acids). More importantly, network pharmacology and Western blot results suggested that GQHX could alleviate the clinical symptoms of CS by regulating the abnormal expression of AGE-RAGE, MAPK, and HIF-1 signaling pathways.

CONCLUSION

This study elucidated the role of GQHX in alleviating CS and highlighted the mechanisms involved, particularly the regulation of gut microbiota and lipid metabolism, as well as the AGE-RAGE, MAPK, and HIF-1 signaling pathways.

Transcription factor EP300 targets SIRT5 to promote autophagy of nucleus pulposus cells and attenuate intervertebral disc degeneration

BACKGROUND

Intervertebral disc degeneration (IVDD) is a prevalent spinal ailment and the leading cause of chronic low back pain. Understanding the exact pathogenesis of IVDD and developing targeted molecular drugs will be important in the future. Autophagy plays a key role in the metabolic processes and in the quality control of proteins in IVDD. However, the role of autophagy in the senescence of nucleus pulposus cell (NPC), the primary cells in the intervertebral disc responsible for maintaining the disc's structure and function, is not yet clear.

METHODS

Gene expression profiling data of human disc tissue were obtained from the Gene Expression Omnibus GSE15227, GSE23130, and GSE70362 datasets. Autophagy-related differentially expressed genes were identified from the Molecular Signatures Database (MSigDB) database. Weighted gene co-expression network analysis (WGCNA), receiver operating characteristic (ROC) curves, and least absolute shrinkage and selection operator (LASSO) regression identified an autophagy-related hub gene that encodes the E1A binding protein EP300 transcription factor in IVDD samples. Potential downstream target genes of EP300 were identified by bioinformatics analysis. The analysis identified sirtuin 5 (SIRT5) as a potential downstream target of EP300. Chromatin immunoprecipitation (ChIP)-qPCR, small interfering RNA (siRNA), and luciferase reporter gene assays were used to verify the interaction of EP300 and SIRT5 in vitro. For in vivo experiments, SIRT5 knockout mice and SIRT5-overexpressing adeno-associated virus serotype 5 (AAV5) were constructed to verify the effect of the EP300-SIRT5 signal axis on the progression of IVDD.

RESULTS

EP300 expression was reduced in the IVDD samples compared with its expression in healthy disc tissue samples. The reduced EP300 expression inhibited the occurrence of autophagy, which promoted NPC senescence. ChIP-qPCR and luciferase reporter gene assays showed that EP300 promoted SIRT5 expression by direct binding to its promoter. Activation of EP300 expression increased SIRT5 expression and significantly improved autophagy for inhibition of NPC senescence. In vivo experiments confirmed that knockdown of EP300 promoted NPC senescence and led to an exacerbation of IVDD, which was reversed by SIRT5 overexpression.

CONCLUSION

Our results provide the first evidence for the importance of EP300 and SIRT5 interactions in promoting IVDD development by inhibiting autophagy during IVDD. The EP300-SIRT5 signaling axis was identified as a promising target for therapy of IVDD based on autophagy genes.

Therapeutic effects of PDGF-AB/BB against cellular senescence in human intervertebral disc

Cellular senescence, characterized by a permanent state of cell cycle arrest and a secretory phenotype contributing to inflammation and tissue deterioration, has emerged as a target for age-related interventions. Accumulation of senescent cells is closely linked with intervertebral disc (IVD) degeneration, a prevalent age-dependent chronic disorder causing low back pain. Previous studies have highlighted that platelet-derived growth factor (PDGF) mitigated IVD degeneration through anti-apoptosis, anti-inflammation, and pro-anabolism. However, its impact on IVD cell senescence remains elusive. In this study, human NP and AF cells derived from aged, degenerated IVDs were treated with recombinant human (rh) PDGF-AB/BB for 5 days and changes of transcriptome profiling were examined through mRNA sequencing. NP and AF cells demonstrated similar but distinct responses to the treatment. However, the effects of PDGF-AB and BB on human IVD cells were comparable. Specifically, PDGF-AB/BB treatment resulted in downregulation of gene clusters related to neurogenesis and response to mechanical stimulus in AF cells while the downregulated genes in NP cells were mainly associated with metabolic pathways. In both NP and AF cells, PDGF-AB and BB treatment upregulated the expression of genes involved in cell cycle regulation, mesenchymal cell differentiation, and response to reduced oxygen levels, while downregulating the expression of genes related to senescence associated phenotype, including oxidative stress, reactive oxygen species (ROS), and mitochondria dysfunction. Network analysis revealed that PDGFRA and IL6 were the top hub genes in treated NP cells. Furthermore, in irradiation-induced senescent NP cells, PDGFRA gene expression was significantly reduced compared to non-irradiated cells. However, rhPDGF-AB/BB treatment increased PDGFRA expression and mitigated the senescence progression through increased cell population in the S phase, reduced SA-β-Gal activity, and decreased expression of senescence related regulators including P21, P16, IL6, and NF-κB. Our findings reveal a novel anti-senescence role of PDGF in the IVD, making it a promising potential candidate to delay aging-induced IVD degeneration.

Abstract Figure

Potential of N-acetylcysteine in the management of low back pain: a scoping review of studies in humans and animal models

Low back pain (LBP) is a common type of pain that causes disability and impairs cognitive function. With over 80% of adults estimated to experience LBP during their lifetime, this type of pain not only has a significant impact on the individual, but also on public health systems and national economies. Unfortunately, there is no single standard of care for patients with LBP. N-acetylcysteine (NAC), which is used clinically to treat acetaminophen overdose, has recently been tested as a potential treatment for LBP. NAC is inexpensive and commercially available, and it has an established tolerance and safety profile. However, NAC's efficacy in LBP has not been established. This scoping review presents a summary of studies investigating the effects of NAC and the potential benefits in LBP treatment, and highlights its potential molecular mechanisms and side effects. A systematic literature search in Pubmed/MEDLINE, Embase, Scopus, Science Direct, Web of Science, Cinahl, and Lilacs databases was conducted. The PRISMA-ScR checklist was used to ensure integrity of the review. The scoping review protocol was registered in the Open Science Framework. No limit was set on study language and publication date. In total, 2357 articles were located, of which 16 were included. The studies show that NAC has potential for LBP treatment, but data are derived only from a few clinical trials and preclinical studies. Thus, there is much to learn and more clinical studies should be performed before NAC can be clinically recommended for the treatment of LBP.

TNFR1-mediated senescence and lack of TNFR2-signaling limit human intervertebral disc cell repair potential in degenerative conditions

OBJECTIVE

To identify mechanisms and treatment targets in painful intervertebral disc (IVD) degeneration (IVDD) progression with a focus on pro-inflammatory tumor necrosis factor-alpha (TNFα)-receptor-1 (TNFR1) and pro-reparative TNFα receptor-2 (TNFR2) signaling.

DESIGN

IVDD tissues and cells from IVDD and autopsy subjects were analyzed with single-cell RNA-sequencing to identify cell populations expressing TNFR1 and TNFR2, and multiplexed array to identify inflammatory proteins in IVDD conditioned media (CM). Bulk RNA-seq evaluated inflammatory and cell cycle states of human annulus fibrosus (hAF) cells challenged with CM. hAF cell responses to TNFR1 and TNFR2 modulation were evaluated by treatment with TNFR1- and TNFR2-blocking antibodies and TNFR2-activator Atsttrin.

RESULTS

IVDD CM chemokines and cytokines were expressed primarily by a small macrophage population and at low levels by native IVD cells. CM-treated hAF cells exhibited TNFα-signaling responses with reduced metabolic rates (MTT: 0.75 [95%CI:0.67 to 0.82]), limited inflammatory responses (inferred from heatmap of 50 differentially expressed genes), and senescence (10.4% SA-β-Gal+ cells [95%CI:6.99 to 13.8]). TNFR1-inhibition sufficiently restored hAF cell metabolism to enable robust pro-inflammatory responses to the complex IVDD CM cytokine mixture (multiple assays,). TNFR2-staining was limited on human IVD cell membranes and TNFR2 modulation had no effect on hAF cells, together suggesting a lack of TNFR2-signaling in native IVD cells.

CONCLUSIONS

Secreted proteins from IVDD CM caused hAF cells to have reduced metabolic rates, attenuated inflammatory responses, and senescence indicating a TNFR1-dominated response with metabolic impairment. Meanwhile, human IVD cells lacked reparative TNFR2-signaling since its modulation caused no effects, to suggest enhanced TNFR2-signaling in IVD repair may need recruitment or delivery of macrophages or other TNFR2-expressing cells.

Senolytic treatment for low back pain

Senescent cells (SnCs) accumulate because of aging and external cellular stress throughout the body. They adopt a senescence-associated secretory phenotype (SASP) and release inflammatory and degenerative factors that actively contribute to age-related diseases, such as low back pain (LBP). The senolytics, o-vanillin and RG-7112, remove SnCs in human intervertebral discs (IVDs) and reduce SASP release, but it is unknown whether they can treat LBP. sparc-/- mice, with LBP, were treated orally with o-vanillin and RG-7112 as single or combination treatments. Treatment reduced LBP and SASP factor release and removed SnCs from the IVD and spinal cord. Treatment also lowered degeneration scores in the IVDs, improved vertebral bone quality, and reduced the expression of pain markers in the spinal cord. Together, our data suggest RG-7112 and o-vanillin as potential disease-modifying drugs for LBP and other painful disorders linked to cell senescence.

Causal Relationship Between Mitochondrial DNA Copy Number and Intervertebral Disc Degeneration: A Bidirectional 2-Sample Mendelian Randomization Study

OBJECTIVE

The causal relationship between mitochondrial DNA copy number (mtDNA-CN) and intervertebral disc degeneration (IVDD) remains unclear. The study aimed to investigate the causal relationship between mtDNA-CN and IVDD using Mendelian randomization (MR) analyses.

METHODS

The causal relationship between mtDNA-CN and IVDD was estimated using a bidirectional 2-sample MR method. The inverse-variance weighted method was employed as the main MR method. Sensitivity analyses were conducted to validate the robustness and reliability of the MR results.

RESULTS

The MR results by inverse-variance weighted revealed that genetically predicted mtDNA-CN was not associated with IVDD (odds ratio = 0.91; 95% confidence interval = 0.79-1.04; P = 0.1731). Similar results were observed in other 4 MR methods (P > 0.05). Heterogeneity was found in the analysis of IVDD on mtDNA-CN (P < 0.05), while no horizontal pleiotropy was observed (P > 0.05). Furthermore, the leave-one-out analysis indicated the robustness of MR results not biased by a single nucleotide polymorphism. Moreover, the reverse MR analysis did not reveal any significant causal association of IVDD on mtDNA-CN.

CONCLUSIONS

The study revealed that there is no causal relationship of mtDNA-CN on the risk of IVDD, nor does IVDD have a significant causal effect on mtDNA-CN. Although the study did not find a significant causal relationship, it provides valuable insights into the complex interplay between genetic factors and IVDD. Further research is needed to explore to better understand the underlying mechanisms of this condition.

Targeting Piezo1 channel to alleviate intervertebral disc degeneration

Background

Low back pain impacts over 600 million people worldwide, predominantly due to intervertebral disc degeneration. This study focuses on the role of Piezo1, a crucial mechanosensitive ion channel protein, in the pathology and potential treatment of disc degeneration.

Materials and methods

To investigate the effects of disc-specific Piezo1 deletion, we generated Aggrecan CreERT2 ; Piezo1 fl/fl mice and examined both lumbar spine instability (LSI)- and aging-induced disc degeneration. Additionally, the effect of pharmacological inhibition of Piezo1 was evaluated using GsMTx4, a potent Piezo1 antagonist, in an ex vivo model stimulated with IL-1β to induce disc degeneration. Assessments included histological examinations, immunofluorescence, and western blot analyses to thoroughly characterize the alterations in the intervertebral discs.

Results

Elevated expression of Piezo1 was detected in the nucleus pulposus (NP) of intervertebral discs with advanced disc degeneration in both aged mice and human patients. Inducible deletion of Piezo1 expression in aggrecan-expressing disc cells significantly reduced lumbar disc degeneration, decreased extracellular matrix (ECM) degradation, and lowered apoptosis in NP cells, observed in both aged mice and those undergoing LSI surgery. Excessive compression loading (CL) upregulated Piezo1 expression, induced ECM disruption, and increased apoptosis in NP cells, whereas inhibition of Piezo1 with GsMTx4 effectively mitigated these pathological changes. Furthermore, in ex vivo cultured mouse discs, GsMTx4 treatment significantly alleviated IL-1β-induced degenerative damages, restored ECM anabolism, and reduced apoptosis.

Conclusions

The findings suggest that Piezo1 plays a critical role in the development of disc degeneration and highlight its potential as a therapeutic target. Inhibiting Piezo1 could offer a novel strategy for treating or preventing this critical disease.

Translational potential of this article

This research highlights the involvement of Piezo1 in the development of intervertebral disc degeneration and emphasizes the potential for targeting Piezo1 as a therapeutic strategy to delay or reverse this condition.

The anti-oxidation related bioactive materials for intervertebral disc degeneration regeneration and repair

Intervertebral disc degeneration (IVDD) is a prevalent chronic spinal condition characterized by the deterioration of the intervertebral discs (IVD), leading to structural damage and associated pain. This degenerative process is closely linked to oxidative stress injury, which plays a pivotal role in its onset and progression. Oxidative stress in IVDD results from the excessive production of reactive oxygen species (ROS) and impaired ROS clearance mechanisms, disrupting the redox balance within the intervertebral disc. Consequently, oxidative stress contributes to the degradation of the extracellular matrix (ECM), promotes cell apoptosis, and exacerbates disc tissue damage. Current treatment options for IVDD face significant challenges in effectively alleviating the oxidative stress-induced damage and facilitating disc tissue repair. However, recent advancements in biomaterials have opened new avenues of hope for IVDD treatment by addressing oxidative stress. In this review, we first provide an overview of the pathophysiological process of IVDD and explore the mechanisms and pathways associated with oxidative stress injury. Then, we delve into the current research on antioxidant biomaterials employed in the treatment of IVDD, and outline the advantages and limitations of hydrogel, nanomaterials, polyphenol and inorganic materials. Finally, we propose the future research direction of antioxidant biomaterials in IVDD treatment. The main idea of this review is shown in Scheme 1.

MiRNA Let-7i-5p-Contained Small Extracellular Vesicles from Macrophages Induce Nucleus Pulposus Cell Senescence via Targeting LIN28A

Purpose

To investigate the role of macrophage-derived small extracellular vesicles (MΦ-sEVs) in nucleus pulposus (NP) cell (NPC) senescence and screen the pro-senescent micro-RNA (miRNA) in MΦ-sEVs and potential mRNA targets.

Methods

Bone marrow-derived macrophage (BMDM)-derived sEVs were isolated by differential centrifugation, and the phenotypes of MΦ-sEVs were identified. NPCs were treated with MΦ-sEVs, and cellular senescence levels were examined by senescence-associated β-galactosidase (SA‑β‑Gal) staining and Western blotting (WB). Activation of the senescence-associated secretory phenotype (SASP) was tested using qRT-PCR and cytometric bead arrays (CBA). LPS+IFNγ-MΦ-sEVs or IL-4-MΦ-sEVs were injected into the rat coccygeal NP tissues to determine the in vivo effects of MΦ-sEVs on intervertebral disc degeneration (IVDD) and NPC senescence. The miRNA levels in MΦ-sEVs were evaluated using PANDORA sequencing. NPCs were transfected with miRNA mimics or inhibitors to screen the miRNAs with pro-senescence effects.

Results

MΦ-sEVs displayed the cup-shaped morphology, with diameters mainly ranging from 40 to 200 nm. Both LPS+IFNγ-MΦ-sEVs and IL-4-MΦ-sEVs impaired NPC viability and accelerated NPC senescence. The expression levels of SASP and senescence-related proteins, including p16, p21, and p53, were elevated by MΦ-sEVs treatment. Animal experiments indicated that LPS+IFNγ-MΦ-sEVs or IL-4-MΦ-sEVs exacerbated IVDD with increased p16-positive cell ratio and activated SASP. PANDORA sequencing of MΦ-sEVs revealed high levels of let-7i-5p, which exerted pro-senescence effects by downregulating LIN28A expression. Inhibiting or silencing LIN28A by C1632 or specific siRNAs also triggered NPC senescence.

Conclusion

Both LPS+IFNγ-MΦ-sEVs and IL-4-MΦ-sEVs induced NPC senescence by delivering miRNA let-7i-5p to inhibit LIN28A.

Targeting skeletal interoception: a novel mechanistic insight into intervertebral disc degeneration and pain management

Despite being a leading cause of chronic pain and disability, the underlying mechanisms of intervertebral disc (IVD) degeneration (IVDD) remain unclear. Emerging evidence suggests that mechanosensation (the ability of the skeletal system to perceive mechanical and biochemical signals) mediated by abnormal mechanical loading plays a critical role in the regulation of IVD health. This review examines the complex interactions amongIVDs, intraosseous sensory mechanisms, and the central nervous system (CNS), with a particular focus on the roles of pathways such as PGE2/EP4, Wnt/β-catenin, and NF-κB. This review elucidates the manner in which mechanical stress and aberrant signaling disrupt the homeostasis of the nucleus pulposus (NP), cartilaginous endplate (CEP) and annulus fibrosus (AF), thereby driving degeneration and exacerbating pain. Furthermore, targeted therapeutic strategies, including the modulation of skeletal interoception and dynamic mechanical loading, present novel avenues for reversing IVDD progression. By integrating skeletal biology with spinal pathology, this work offers a novel perspective on the pathogenesis of IVDD and identifies promising strategies for clinical intervention. These findings highlight the potential of targeting skeletal interoception to mitigate IVDD and associated pain, paving the way for innovative, mechanism-driven therapies.

Senescent cells as a target for anti-aging interventions: From senolytics to immune therapies

Aging and age-related diseases are major drivers of multimorbidity and mortality worldwide. Cellular senescence is a hallmark of aging. The accumulation of senescent cells is causally associated with pathogenesis of various age-associated disorders. Due to their promise for alleviating age-related disorders and extending healthspan, therapeutic strategies targeting senescent cells (senotherapies) as a means to combat aging have received much attention over the past decade. Among the conventionally used approaches, one is the usage of small-molecule compounds to specifically exhibit cytotoxicity toward senescent cells or inhibit deleterious effects of the senescence-associated secretory phenotype (SASP). Alternatively, there are immunotherapies directed at surface antigens specifically upregulated in senescent cells (seno-antigens), including chimeric antigen receptor (CAR) therapies and senolytic vaccines. This review gives an update of the current status in the discovery and development of senolytic therapies, and their translational progress from preclinical to clinical trials. We highlight the current challenges faced by senotherapeutic development in the context of senescence heterogeneity, with the aim of offering novel perspectives for future anti-aging interventions aimed at enhancing healthy longevity.

The cross-talk between the cGAS-STING signaling pathway and chronic inflammation in the development of musculoskeletal disorders

Musculoskeletal disorders (MSDs) comprise diverse conditions affecting bones, joints, and muscles, leading to pain and loss of function, and are one of the most prevalent and major global health concerns. One of the hallmarks of MSDs is DNA damage. Once accumulated in the cytoplasm, the damaged DNA is sensed by the cyclic GMP-AMP synthase (cGAS)/stimulator of interferon genes (STING) pathway, which triggers the induction of type I interferons and inflammatory cytokines. Thus, this pathway connects the musculoskeletal and immune systems. Inhibitors of cGAS or STING have shown promising therapeutic effects in the pre-clinical models of several MSDs. Systemic, chronic, low-grade inflammation (SCLGI) underlies the development and maintenance of many MSDs. Failure to resolve SCLGI has been hypothesized to play a critical role in the development of chronic diseases, suggesting that the successful resolution of SCLGI will result in the alleviation of their related symptomatology. The process of inflammation resolution is feasible by specialized pro-resolving mediators (SPMs), which are enzymatically generated from dietary essential polyunsaturated fatty acids (PUFAs). The supplementation of SPMs or their stable, small-molecule mimetics and receptor agonists has revealed beneficial effects in inflammation-related animal models, including arthropathies, osteoporosis, and muscle dystrophy, suggesting a translational potential in MSDs. In this review, we substantiate the hypothesis that the use of cGAS-STING signaling pathway inhibitors together with SCLG-resolving compounds may serve as a promising new therapeutic approach for MSDs.

Collagenase Chemonucleolysis for Treating Cervical Disc Herniation: An Exploratory, Single-Arm, Open-Label, Multicenter Clinical Trial

INTRODUCTION

Cervical disc herniation (CDH) is the most common cause of cervical radiculopathy and causes persistent neck pain and neurological deficits. Collagenase chemonucleolysis has been successfully applied to treat lumbar disc herniation, which has a similar pathological mechanism to CDH. However, its application for CDH remains under-researched, and there is an even greater lack of high-quality clinical evidence. This study aims to evaluate the efficacy and safety of collagenase chemonucleolysis for treating CDH.

METHODS

Eligible patients with CDH underwent collagenase chemonucleolysis via anterior cervical intradiscal injection or epidural injection. The primary efficacy endpoint showed an excellent and good rate regarding the Odom criteria, which was not lower than the reference value (≥ 78%) at 6 months postoperatively. The secondary efficacy endpoints were the percentage reduction in Numeric Rating Scale (NRS) and Neck Disability Index (NDI) scores from baseline, which were not lower than the reference values (≥ 40%, ≥ 30%), and improvement in the 36-Item Short Form Health Survey (SF-36) score compared to the preoperative value. The pre- and postoperative CDH index of patients were also compared. Safety endpoints included the incidence of adverse events (AEs) and serious adverse events (SAEs).

RESULTS

An excellent and good rate regarding the Odom criteria 6 months postoperatively was 90.5% (133/147), which was significantly higher than 78% (P < 0.004, 95% confidence interval 85.7-95.2%). The reduction in NRS and NDI scores exceeded 40% (P < 0.001) and 30% (P < 0.001), respectively. The SF-36 scores at 3 months and 6 months postoperatively were significantly higher than those preoperatively (P < 0.001). A significant difference was observed in the pre- and postoperative CDH index (109.6 ± 119.1 vs. 70.8 ± 74.8, P < 0.001). The incidence of AEs was 22.5% (33/147), of which 97.8% were grade 1-2. No collagenase-related AEs and SAEs occurred.

CONCLUSION

Collagenase chemonucleolysis treatment for CDH exhibited favorable efficacy and safety and may be a better choice for patients in whom conservative treatment is ineffective.

TRIAL REGISTRATION

The trial was registered on www.Chictr.org.cn (ChiCTR2200063043).

The role of SASP in ischemic stroke: a deep dive into cellular mechanisms

Background

The escalating incidence of ischemic stroke (IS) exerts a heavy toll on global health. Aging, a prominent risk factor, implicates the senescence-associated secretory phenotype (SASP) in IS pathogenesis. We postulated that alterations in SASP-related factor expression during IS correlate with remodeling of intercellular interaction networks and disease advancement. The present study endeavored to preliminarily dissect the SASP-IS nexus via combined bulk and single-cell transcriptome analysis.

Methods

Aggregated expression profiles from human peripheral blood bulk chips and MCAO mouse single-cell sequencing data, followed by SASP gene analysis. Executed protein interaction network and enrichment assays. Investigated immune infiltration in stroke patients, managed quality control and annotation of single-cell data, cherry-picked central cells based on SASP scores, unearthed essential genes via enrichment analysis, conducted pseudo-time and intercellular communication studies, and prognosticated drugs for hub genes. Finally, authenticated core gene expression in serum of MCAO and Sham rats using real-time fluorescent polymerase chain reaction (RT-qPCR).

Results

Fourteen hub genes were discerned. Seven cell types were annotated in MCAO mouse peripheral blood single-cell data. Basophils exhibited the highest SASP scores, with Lcp1 upregulated and Ccl3 downregulated in basophils of the MCAO group. Enrichment analysis divulged a significant association of Ccl3 with the cell apoptosis pathway and Lcp1 with immune responses. The Ccl3 gene is pivotal in basophils and basophil-neutrophil crosstalk. Additionally, we forecasted nagrestipen's regulatory function on Ccl3. RT-qPCR demonstrated a marked elevation in Lcp1 mRNA and a pronounced reduction in Ccl3 in the MCAO group relative to the Sham group.

Conclusion

The Ccl3 gene in basophils and its immune cell interaction is a linchpin in the IS immune microenvironment. Ccl3 and Lcp1 might potentially modulate IS progression by influencing SASP, proffering novel prospects for IS clinical diagnosis and treatment.

Deciphering SPP1-related macrophage signaling in the pathogenesis of intervertebral disc degeneration

This study delved into the molecular mechanisms underlying mechanical stress-induced intervertebral disc degeneration (msi-IDD) through single-cell and high-throughput transcriptome sequencing in mouse models and patient samples. Results exhibited an upsurge in macrophage presence in msi-IDD intervertebral disc (IVD) tissues, with secreted phosphoprotein 1 (SPP1) identified as a pivotal driver exacerbating degeneration via the protein kinase RNA-like endoplasmic reticulum kinase/ activating transcription factor 4/ interleukin-10 (PERK/ATF4/IL-10) signaling axis. Inhibition of SPP1 demonstrated promising outcomes in mitigating msi-IDD progression in both in vitro and in vivo models. These findings underscore the therapeutic promise associated with the modulation of the PERK signaling pathway in IDD, shedding light on the pathogenesis of msi-IDD and proposing a promising avenue for intervention strategies.

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.

MARCHF8-mediated ubiquitination via TGFBI regulates NF-κB dependent inflammatory responses and ECM degradation in intervertebral disc degeneration

AIM

To explore the role of the hub gene Transforming Growth Factor Beta Induced (TGFBI) in Intervertebral disc degeneration (IDD) pathogenesis and its regulatory relationship with Membrane Associated Ring-CH-Type Finger 8 (MARCHF8).

BACKGROUND

IDD is a prevalent musculoskeletal disorder leading to spinal pathology. Despite its ubiquity and impact, effective therapeutic strategies remain to be explored.

OBJECTIVE

Identify key modules associated with IDD and understand the impact of TGFBI on nucleus pulposus (NP) cell behavior, extracellular matrix (ECM)-related proteins, and the Nuclear Factor kappa-light-chain-enhancer of Activated B cells (NF-κB) signaling pathway.

METHODS

The GSE146904 dataset underwent Weighted Gene Co-Expression Network Analysis (WGCNA) for key module identification and Differentially Expressed Genes (DEGs) screening. Intersection analysis, network analysis, and co-expression identified TGFBI as a hub gene. In vitro experiments delved into the interplay between TGFBI and MARCHF8 and their effects on NP cells.

RESULTS

WGCNA linked the MEturquoise module with IDD samples, revealing 145 shared genes among DEGs. In vitro findings indicated that MARCHF8 determines TGFBI expression. TGFBI boosts apoptosis and ECM breakdown in Lipopolysaccharide-stimulated (LPS-stimulated) NP cells. Altering TGFBI levels modulated these effects and the NF-κB signaling pathway, influencing inflammatory cytokine concentrations. Moreover, MARCHF8 ubiquitination controlled TGFBI expression.

CONCLUSION

TGFBI, modulated by MARCHF8, significantly influences IDD progression by affecting NP cell apoptosis, ECM degradation, and inflammation through the NF-κB signaling pathway.

Specific plasma biomarker signatures associated with patients undergoing surgery for back pain

BACKGROUND CONTEXT

Intervertebral disc degeneration (IDD) affects numerous people worldwide. The role of inflammation is increasingly recognized but remains incompletely resolved. Peripheral molecules could access neovascularized degenerated discs and contribute to the ongoing pathology.

PURPOSE

To assess a large array of plasma molecules in patients with IDD to identify biomarkers associated with specific spinal pathologies and prognostic biomarkers for the surgery outcome.

DESIGN

Prospective observational study combining clinical data and plasma measures.

PATIENT SAMPLE

Plasma samples were collected just before surgery. Extensive clinical data (age, sex, smoking status, Modic score, glomerular filtration rate, etc.) were extracted from clinical files from 83 patients with IDD undergoing spine surgery.

OUTCOME MEASURES

Recovery 2 months postsurgery as assessed by the treating neurosurgeon.

METHODS

Over 40 biological molecules were measured in patients' plasma using multiplex assays. Statistical analyses were performed to identify associations between biological and clinical characteristics (age, sex, Body Mass Index (BMI), smoking status, herniated disc, radiculopathy, myelopathy, stenosis, MODIC score, etc.) and plasma levels of biological molecules.

RESULTS

Plasma levels of Neurofilament Light chain (NfL) were significantly elevated in patients with myelopathy and spinal stenosis compared to herniated disc. Plasma levels of C- reactive protein (CRP), Neurofilament Light chain (NfL), and Serum Amyloid A (SAA) were negatively associated, while CCL22 levels were positively associated with an efficient recovery 2 months postsurgery.

CONCLUSIONS

Our results show that CRP and CCL22 plasma levels combined with the age of the IDD patient can predict the 2-month postsurgery recovery (Area Under the Curve [AUC]=0.883). Moreover, NfL could become a valuable monitoring tool for patients with spinal cord injuries.

Endplate chondrocyte-derived exosomal miR-128-3p mitigates intervertebral disc degeneration by targeting TRAF6 via the miR-128-3p/TRAF6 axis to suppress pyroptosis

Intervertebral disc degeneration (IVDD) is a leading cause of chronic back pain and significantly impacts quality of life. The pathogenesis of IVDD is largely driven by inflammation, pyroptosis, and extracellular matrix (ECM) degradation, which current therapies fail to adequately address. In this study, we explore the therapeutic potential of exosomes derived from endplate chondrocytes (EPCs), with a particular focus on the microRNA miR-128-3p. Our findings reveal that exosomes isolated from third-generation EPCs, enriched with miR-128-3p, exhibit potent anti-inflammatory and anti-pyroptotic effects in lipopolysaccharide-treated nucleus pulposus cells, which are key contributors to IVDD pathology. Specifically, we demonstrate that miR-128-3p delivered via EPC-derived exosomes directly targets TRAF6, effectively suppressing activation of the NF-κB signaling pathway, which is known to play a pivotal role in inflammation and ECM breakdown, leading to a marked reduction in pro-inflammatory cytokine release and mitigation of ECM degradation. Importantly, third-generation EPC exosomes, with higher levels of miR-128-3p, showed superior efficacy compared to fifth-generation EPCs, underscoring the critical role of miR-128-3p in mediating these protective effects. Our research highlights the promise of EPC-derived exosomes, particularly those rich in miR-128-3p, as a novel, cell-free therapeutic approach for IVDD. Unlike current treatments that focus primarily on symptom management, our approach targets key molecular pathways underlying IVDD progression, including inflammation, pyroptosis, and ECM degradation. By elucidating the miR-128-3p/TRAF6 axis, this study provides a foundation for the development of targeted, biologically based interventions aimed at halting or even reversing IVDD, thereby offering hope for more effective and lasting therapeutic options.

Mitochondrial quality control: the real dawn of intervertebral disc degeneration?

Intervertebral disc degeneration is the most common disease in chronic musculoskeletal diseases and the main cause of low back pain, which seriously endangers social health level and increases people's economic burden. Disc degeneration is characterized by NP cell apoptosis, extracellular matrix degradation and disc structure changes. It progresses with age and under the influence of mechanical overload, oxidative stress and genetics. Mitochondria are not only the energy factories of cells, but also participate in a variety of cellular functions such as calcium homeostasis, regulation of cell proliferation, and control of apoptosis. The mitochondrial quality control system involves many mechanisms such as mitochondrial gene regulation, mitochondrial protein import, mitophagy, and mitochondrial dynamics. A large number of studies have confirmed that mitochondrial dysfunction is a key factor in the pathological mechanism of aging and intervertebral disc degeneration, and balancing mitochondrial quality control is extremely important for delaying and treating intervertebral disc degeneration. In this paper, we first demonstrate the molecular mechanism of mitochondrial quality control in detail by describing mitochondrial biogenesis and mitophagy. Then, we describe the ways in which mitochondrial dysfunction leads to disc degeneration, and review in detail the current research on targeting mitochondria for the treatment of disc degeneration, hoping to draw inspiration from the current research to provide innovative perspectives for the treatment of disc degeneration.

Animal Models of Intervertebral Disc Diseases: Advantages, Limitations, and Future Directions

Animal models are valuable tools for studying the underlying mechanisms of and potential treatments for intervertebral disc diseases. In this review, we discuss the advantages and limitations of animal models of disc diseases, focusing on lumbar spinal stenosis, disc herniation, and degeneration, as well as future research directions. The advantages of animal models are that they enable controlled experiments, long-term monitoring to study the natural history of the disease, and the testing of potential treatments. However, they also have limitations, including species differences, ethical concerns, a lack of standardized protocols, and short lifespans. Therefore, ongoing research focuses on improving animal model standardization and incorporating advanced imaging and noninvasive techniques, genetic models, and biomechanical analyses to overcome these limitations. These future directions hold potential for improving our understanding of the underlying mechanisms of disc diseases and for developing new treatments. Overall, although animal models can provide valuable insights into pathophysiology and potential treatments for disc diseases, their limitations should be carefully considered when interpreting findings from animal studies.

Exploration and breakthrough in the mode of intervertebral disc cell death may lead to significant advances in treatments for intervertebral disc degeneration

Low back pain caused by intervertebral disc degeneration (IDD) has emerged as a significant global public health concern, with far-reaching consequences for patients' quality of life and healthcare systems. Although previous research have revealed that the mechanisms of intervertebral disc cell apoptosis, pyroptosis and necroptosis can aggravate IDD damage by mediating inflammation and promoting extracellular matrix degradation, but they cannot explain the connection between different cell death mechanisms and ion metabolism disorders. The latest study shows that cell death mechanisms such as cellular senescence, ferroptosis, and cuproptosis, and PANopotosis have similar roles in the progression of intervertebral disc degeneration, but not exactly the same damage mechanism. This paper summarizes the effects of various cell death patterns on the disease progression of IDD, related molecular mechanisms and signaling pathways, providing new perspectives and potential clinical intervention strategies for the prevention and treatment of IDD.

The pathogenesis and targeted therapies of intervertebral disc degeneration induced by cartilage endplate inflammation

Intervertebral disc degeneration (IVDD) is the leading cause of low back pain, where degeneration and death of nucleus pulposus cells within the intervertebral disc (IVD) can be obviously revealed. This degeneration can result in an imbalance in the extracellular matrix due to the loss of proteoglycans and water content, which can further lead to catabolic and anabolic dysfunction of the IVD. Recently, the dysfunction of cartilage endplate (CEP) during aging has drawn large attention due to its essential functions in contributing nutrient exchange and maintaining IVD homeostasis. Furthermore, the inflammation and disturbed homeostasis of CEP not only accelerate the degradation of nucleus pulposus extracellular matrix, but also exacerbate IVDD by causing nucleus pulposus cell death through other pathological factors. Here in this review, we summarized the possible pathological factors and the underlying mechanisms of the CEP inflammation-induced IVDD, including exosomes degeneration, CEP calcification, ferroptosis, mechanical changes, and cell senescence. Besides, changes of miRNAs, pain-related neural reflex arc and pathways associated with CEP inflammation-induced IVDD are also reviewed. In addition, new strategies specifically designed for CEP inflammation-induced IVDD are also discussed in the last section. We hope this paper can not only offer some new insights for advancing novel strategies for treating IVDD, but also serve as a valuable reference for researchers in this field.

Molecular mechanism of mechanical pressure induced changes in the microenvironment of intervertebral disc degeneration

BACKGROUND

Lower back pain, as a typical clinical symptom of spinal degenerative diseases, is emerging as a major social problem. According to recent researches, the primary cause of this problem is intervertebral disc degeneration (IVDD). IVDD is closely associated with factors such as age, genetics, mechanical stimulation (MS), and inadequate nutrition. In recent years, an increasing number of studies have further elucidated the relationship between MS and IVDD. However, the exact molecular mechanisms by which MS induces IVDD remain unclear, highlighting the need for in-depth exploration and study of the relationship between MS and IVDD.

METHODS

Search for relevant literature on IVDD and MS published from January 1, 2010, to the present in the PubMed database.

RESULTS

One of the main causes of IVDD is MS, and loading modalities have an impact on the creation of matrix metalloproteinase, the metabolism of the cellular matrix, and other biochemical processes in the intervertebral disc. Nucleus pulposus cell death induced by MS, cartilage end-plate destruction accompanied by pyroptosis, apoptosis, iron death, senescence, autophagy, oxidative stress, inflammatory response, and ECM degradation interact with one another to form a cooperative signaling network.

CONCLUSION

This review discusses the molecular mechanisms of the changes in the microenvironment of intervertebral discs caused by mechanical pressure, explores the interaction between mechanical pressure and IVDD, and provides new insights and approaches for the clinical prevention and treatment of IVDD.

Irisin in degenerative musculoskeletal diseases: Functions in system and potential in therapy

Degenerative musculoskeletal diseases are a class of diseases related to the gradual structural and functional deterioration of muscles, joints, and bones, including osteoarthritis (OA), osteoporosis (OP), sarcopenia (SP), and intervertebral disc degeneration (IDD). As the proportion of aging people around the world increases, degenerative musculoskeletal diseases not only have a multifaceted impact on patients, but also impose a huge burden on the medical industry in various countries. Therefore, it is crucial to find key regulatory factors and potential therapeutic targets. Recent studies have shown that irisin plays an important role in degenerative musculoskeletal diseases, suggesting that it may become a key molecule in the prevention and treatment of degenerative diseases of the musculoskeletal system. Therefore, this review provides a comprehensive description of the release and basic functions of irisin, and summarizes the role of irisin in OA, OP, SP, and IDD from a cellular and tissue perspective, providing comprehensive basis for clinical application. In addition, we summarized the many roles of irisin as a key information molecule in bone-muscle-adipose crosstalk and a regulatory molecule involved in inflammation, senescence, and cell death, and proposed the interesting possibility of irisin in degenerative musculoskeletal diseases.

Senescence in Intervertebral Disc Degeneration: A Comprehensive Analysis Based on Bioinformatic Strategies

BACKGROUND

Intervertebral disc degeneration (IDD) is a major cause for low back pain. Studies showed the association between senescence and degenerative diseases. Cell senescence can promote the occurrence and development of degenerative diseases through multiple mechanisms including inflammatory stress, oxidative stress and nutritional deprivation. The roles of senescence and senescence-associated genes (SAGs) remains unknown in IDD.

METHODS

Four differently expressed SAGs were identified as hub SAGs using "limma" package in R. We then calculated the immune infiltration of IDD patients, and investigated the relation between hub SAGs and immune infiltration. Enrichment analysis was performed to explore the functions of hub SAGs in IDD. Nomogram and LASSO model based on hub SAGs was constructed to predict the risk of severe degeneration (SD) for IDD patients. Subsequently, single cell analysis was conducted to describe the expression pattern of hub SAGs in intervertebral disc tissue.

RESULTS

We identified ASPH, CCND1, IGFBP3 and SGK1 as hub SAGs. Further analysis demonstrated that the hub SAGs might mediate the development of IDD by regulating immune infiltration and multiple pathways. The LASSO model based on the four hub SAGs showed good performance in predicting the risk of SD. Single cell analysis revealed that ASPH, CCND1 and SGK1 mainly expressed in nucleus pulposus cells, while IGFBP3 mainly expressed in epithelial cells. Eleven candidate drugs targeting hub SAGS were predicted for IDD patients through Comparative Toxicogenomics Database (CDT). PCR and immunohistochemical analysis showed that the levels of four hub SAGs were higher in SD than MD (mild degeneration) patients.

CONCLUSIONS

We performed a comprehensive analysis of SAGs in IDD, which revealed their functions and expression pattern in intervertebral disc tissue. Based on hub SAGs, we established a predictive model and explored the potential drugs. These findings provide new understandings of SAG mechanism and promising therapeutic strategies for IDD.

An anti-senescence hydrogel with pH-responsive drug release for mitigating intervertebral disc degeneration and low back pain

Oxidative stress and aging lead to progressive senescence of nucleus pulposus (NP) cells, resulting in intervertebral disc (IVD) degeneration (IVDD). In some cases, degenerative IVD can further cause low back pain (LBP). Several studies have confirmed that delaying and rejuvenating the senescence of NP cells can attenuate IVDD. However, the relatively closed tissue structure of IVDs presents challenges for the local application of anti-senescence drugs. Here, we prepared an anti-senescence hydrogel by conjugating phenylboronic acid-modified gelatin methacryloyl (GP) with quercetin to alleviate IVDD by removing senescent NP cells. The hydrogel exhibited injectability, biodegradability, prominent biocompatibility and responsive release of quercetin under pathological conditions. In vitro experiments demonstrated that the hydrogel could reduce the expression of senescence markers and restore the metabolic balance in senescent NP cells. In vivo studies validated that a single injection of the hydrogel in situ could maintain IVD tissue structure and alleviate sensitivity to noxious mechanical force in the rat models, indicating a potential therapeutic approach for ameliorating IVDD and LBP. This approach helps prevent potential systemic toxicity associated with systemic administration and reduces the morbidity resulting from repeated injections of free drugs into the IVD, providing a new strategy for IVDD treatment.

Mitochondrial transplantation: a promising strategy for treating degenerative joint diseases

The prevalence of age-related degenerative joint diseases, particularly intervertebral disc degeneration and osteoarthritis, is increasing, thereby posing significant challenges for the elderly population. Mitochondrial dysfunction is a critical factor in the etiology and progression of these disorders. Therapeutic interventions that incorporate mitochondrial transplantation exhibit considerable promise by increasing mitochondrial numbers and improving their functionality. Existing evidence suggests that exogenous mitochondrial therapy improves clinical outcomes for patients with degenerative joint diseases. This review elucidates the mitochondrial abnormalities associated with degenerative joint diseases and examines the mechanisms of mitochondrial intercellular transfer and artificial mitochondrial transplantation. Furthermore, therapeutic strategies for mitochondrial transplantation in degenerative joint diseases are synthesized, and the concept of engineered mitochondrial transplantation is proposed.

Application trends and strategies of hydrogel delivery systems in intervertebral disc degeneration: A bibliometric review

Hydrogels are widely used to explore emerging minimally invasive strategies for intervertebral disc degeneration (IVDD) due to their suitability as drug and cell delivery vehicles. There has been no review of the latest research trends and strategies of hydrogel delivery systems in IVDD for the last decade. In this study, we identify the application trends and strategies in this field through bibliometric analysis, including aspects such as publication years, countries and institutions, authors and publications, and co-occurrence of keywords. The results reveal that the literature in this field has been receiving increasing attention with a trend of growth annually. Subsequently, the hotspots of hydrogels in this field were described and discussed in detail, and we proposed the "four core factors", hydrogels, cells, cell stimulators, and microenvironmental regulation, required for a multifunctional hydrogel for IVDD. Finally, we discuss the popular and emerging mechanistic strategies of hydrogel therapy for IVDD in terms of five aspects: fundamental pathologic changes in IVDD, counteracting cellular senescence, counteracting cell death, improving organelle function, and replenishing exogenous cells. This study provides a reference and a new perspective for future research in this urgently needed field.

The JNK signaling pathway in intervertebral disc degeneration

Intervertebral disc degeneration (IDD) serves as the underlying pathology for various spinal degenerative conditions and is a primary contributor to low back pain (LBP). Recent studies have revealed a strong correlation between IDD and biological processes such as Programmed Cell Death (PCD), cellular senescence, inflammation, cell proliferation, extracellular matrix (ECM) degradation, and oxidative stress (OS). Of particular interest is the emerging evidence highlighting the significant involvement of the JNK signaling pathway in these fundamental biological processes of IDD. This paper explores the potential mechanisms through the JNK signaling pathway influences IDD in diverse ways. The objective of this article is to offer a fresh perspective and methodology for in-depth investigation into the pathogenesis of IDD by thoroughly examining the interplay between the JNK signaling pathway and IDD. Moreover, this paper summarizes the drugs and natural compounds that alleviate the progression of IDD by regulating the JNK signaling pathway. This paper aims to identify potential therapeutic targets and strategies for IDD treatment, providing valuable insights for clinical application.

Identification of cellular senescence-related genes and immune cell infiltration characteristics in intervertebral disc degeneration

Background

Intervertebral disc degeneration (IDD) progression involves multiple factors, including loss of nucleus pulposus cells and extracellular matrix as the basic pathological mechanism of degeneration, and is closely related to cellular senescence and immune cell infiltration. The aim of study was to identify critical cellular senescence-related genes and immune cell infiltration characteristics in IDD.

Methods

Four datasets, including GSE70362, GSE112216, GSE114169, and GSE150408, were downloaded from the Gene Expression Omnibus database. The senescence-related genes were acquired from the CellAge Database and intersected with differentially expressed genes (DEGs) between IDD and control samples for senescence-related DEGs (SRDEGs). Protein-protein interaction (PPI) network analysis was performed to obtain ten hub SRDEGs. A consensus cluster analysis based on these hub genes was performed to divide the patients into clusters. The functional enrichment, and immune infiltration statuses of the clusters were compared. Weighted gene co-expression network analysis was used to identified key gene modules. The overlapping genes from key modules, DEGs of clusters and hub SRDEGs were intersected to obtain potential biomarkers. To verify the expression of potential biomarkers, quantitative polymerase chain reaction (qPCR) and immunohistochemistry were performed by using human intervertebral disc tissues.

Results

In the GSE70362 dataset, a total of 364 DEGs were identified, of which 150 were upregulated and 214 were downregulated, and 35 genes were selected as SRDEGs. PPI analysis revealed ten hub SRDEGs and consensus cluster analysis divided the patients into two clusters. Compared to Cluster 2, Cluster 1 was highly enriched in extracellular matrix organization and various metabolic process. The level of Follicular T helper cells in the Cluster 1 was significantly higher than that in the Cluster 2. IGFBP3 and NQO1 were identified as potential biomarkers. The remaining 3 datasets, and the result of qPCR and immunohistochemistry showed that the expression levels of NQO1 and IGFBP3 in the degenerated group were higher than those in the control or treatment groups.

Conclusion

Senescence-related genes play a key role in the development and occurrence of IDD. IGFBP3 and NQO1 are strongly correlated with immune infiltration in the IDD and could become novel therapeutic targets that prevent the progression of IDD.

Apoptosis Signal-Regulated Kinase-1 Promotes Nucleus Pulposus Cell Senescence and Apoptosis to Regulate Intervertebral Disc Degeneration

This study investigated the role of apoptosis signal-regulated kinase-1 (ASK1) in intervertebral disc degeneration (IDD). The nucleus pulposus (NP) tissues of non-IDD and IDD patients were subjected to hematoxylin and eosin, Safranin O-fast green, and immunohistochemical staining. Quantitative real-time PCR was used to assess the ASK1 mRNA level within NP tissue samples and cells. The Cell Counting Kit-8 assay, senescence-associated β-galactosidase staining, and flow cytometry were conducted to assess the viability, senescence, and apoptosis of NP cells, respectively. Extracellular matrix-related factors were detected using Western blot analysis. Furthermore, the effect of ASK1 on the IDD rat model was evaluated. Finally, c-Jun N-terminal kinase (JNK) inhibitors were used to verify the effect of the JNK/p38 signaling on IDD. ASK1 mRNA and protein were up-regulated within NP tissue samples from the IDD group, IL-1β-stimulated NP cells, and IDD rats. ASK1 inhibition promoted cell viability and repressed the senescence and apoptosis of NP cells, promoted collagen II and aggrecan, inhibited matrix metalloproteinase 3/9 and a disintegrin and metalloproteinase with thrombospondin motifs 4/5 protein levels, and increased NP cells in rat intervertebral disc tissues. ASK1 overexpression exerted the opposite effects of ASK1 inhibition on NP cells. Additionally, JNK/p38 signaling suppression could reverse the ASK1 up-regulation-induced dysfunction. In conclusion, ASK1 facilitated the senescence and apoptosis of NP cells in promoting IDD progression via the JNK/p38 pathway.

Dysregulated lipid metabolism and intervertebral disc degeneration: the important role of ox-LDL/LOX-1 in endplate chondrocyte senescence and calcification

BACKGROUND

Lipid metabolism disorders are associated with degeneration of multiple tissues and organs, but the mechanism of crosstalk between lipid metabolism disorder and intervertebral disc degeneration (IDD) has not been fully elucidated. In this study we aim to investigate the regulatory mechanism of abnormal signal of lipid metabolism disorder on intervertebral disc endplate chondrocyte (EPC) senescence and calcification.

METHODS

Human intervertebral disc cartilage endplate tissue, cell model and rat hyperlipemia model were performed in this study. Histology and immunohistochemistry were used to human EPC tissue detection. TMT-labelled quantitative proteomics was used to detect differential proteins, and MRI, micro-CT, safranin green staining and immunofluorescence were performed to observe the morphology and degeneration of rat tail intervertebral discs. Flow cytometry, senescence-associated β-galactosidase staining, alizarin red staining, alkaline phosphatase staining, DCFH-DA fluorescent probe, and western blot were performed to detect the expression of EPC cell senescence, senescence-associated secretory phenotype, calcification-related proteins and the activation of cell senescence-related signaling pathways.

RESULTS

Our study found that the highly expressed oxidized low-density lipoprotein (ox-LDL) and Lectin-like oxidized low-density lipoprotein receptor 1 (LOX-1) in human degenerative EPC was associated with hyperlipidemia (HLP). TMT-labelled quantitative proteomics revealed enriched pathways such as cell cycle regulation, endochondral bone morphogenesis and inflammation. The rat model revealed that HLP could induce ox-LDL, LOX-1, senescence and calcification markers high expression in EPC. Moreover, we demonstrated that ox-LDL-induced EPCs senescence and calcification were dependent on the LOX-1 receptor, and the ROS/P38-MAPK/NF-κB signaling pathway was implicated in the regulation of senescence induced by ox-LDL/LOX-1 in cell model.

CONCLUSIONS

So our study revealed that ox-LDL/LOX-1-induced EPCs senescence and calcification through ROS/P38-MAPK/NF-κB signaling pathway, providing information on understanding the link between lipid metabolism disorders and IDD.

FSTL1 Accelerates Nucleus Pulposus Cell Senescence and Intervertebral Disc Degeneration Through TLR4/NF-κB Pathway

Intervertebral disc degeneration (IVDD) is a major contributor to low back pain (LBP), and inflammatory factors play crucial roles in its pathogenesis. Follistatin-like 1 (FSTL1) has been reported to induce an inflammatory response in chondrocytes, microglia and preadipocytes, but its role in the pathogenesis of nucleus pulposus cell (NPC) degeneration remains unclear. In this study, we mainly utilized an acidosis-induced NPC degeneration model and a rabbit puncture IVDD model to investigate the role of FSTL1 in IVDD both in vitro and in vivo. We confirmed that FSTL1 expression significantly increased in nucleus pulposus (NP) tissues from IVDD patients and rabbit puncture IVDD models. The expression levels of FSTL1 were significantly increased in all three models of NPC degeneration under harsh microenvironments. In addition, recombinant human FSTL1 (rh-FSTL1) was found to upregulate the expression of p16 and p21, increase the number of senescence-associated β-galactosidase (SA-β-gal)-positive cells, induce senescence-related secretory phenotypes (SASP), and downregulate extracellular matrix (ECM) protein expressions, leading to an imbalance in ECM metabolism destructions. Conversely, silencing of FSTL1 by small interfering RNA (siRNA) ameliorated senescence of NPCs associated with inflammation in IVDD. Furthermore, Toll-like receptor 4/nuclear factor-κB (TLR4/NF-κB) pathway plays a crucial role in regulating NPC senescence through FSTL1 regulation. Inhibition of TLR4 expression partly reversed the effects of rh-FSTL1 on NPC senescence-associated inflammation. Finally, rabbit IVDD model experiments demonstrated that the specific FSTL1 siRNA markedly repressed the development of IVDD. These findings may offer a therapeutic approach for mitigating inflammation-induced senescence associated with IVDD.

The regulatory mechanism of cyclic GMP-AMP synthase on inflammatory senescence of nucleus pulposus cell

BACKGROUND

Cellular senescence features irreversible growth arrest and secretion of multiple proinflammatory cytokines. Cyclic GMP-AMP synthase (cGAS) detects DNA damage and activates the DNA-sensing pathway, resulting in the upregulation of inflammatory genes and induction of cellular senescence. This study aimed to investigate the effect of cGAS in regulating senescence of nucleus pulposus (NP) cells under inflammatory microenvironment.

METHODS

The expression of cGAS was evaluated by immunohistochemical staining in rat intervertebral disc (IVD) degeneration model induced by annulus stabbing. NP cells were harvested from rat lumbar IVD and cultured with 10ng/ml IL-1β for 48 h to induce premature senescence. cGAS was silenced by cGAS specific siRNA in NP cells and cultured with IL-1β. Cellular senescence was evaluated by senescence-associated beta-galactosidase (SA-β-gal) staining and flow cytometry. The expression of senescence-associated secretory phenotype including IL-6, IL-8, and TNF-a was evaluated by ELISA and western blotting.

RESULTS

cGAS was detected in rat NP cells in cytoplasm and the expression was significantly increased in degenerated IVD. Culturing in 10ng/ml IL-1β for 48 h induced cellular senescence in NP cells with attenuation of G1-S phase transition. In senescent NP cells the expression of cGAS, p53, p16, NF-kB, IL-6, IL-8, TNF-α was significantly increased while aggrecan and collagen type II was reduced than in normal NP cells. In NP cells with silenced cGAS, the expression of p53, p16, NF-kB, IL-6, IL-8, and TNF-α was reduced in inflammatory culturing with IL-1β.

CONCLUSION

cGAS was increased by NP cells in degenerated IVD promoting cellular senescence and senescent inflammatory phenotypes. Targeting cGAS may alleviate IVD degeneration by reducing NP cell senescence.

Wharton's jelly-derived multifunctional hydrogels: New tools to promote intervertebral disc regeneration in vitro and ex vivo

The degeneration of intervertebral disc (IVD) is a disease of the entire joint between two vertebrae in the spine caused by loss of extracellular matrix (ECM) integrity, to date with no cure. The various regenerative approaches proposed so far have led to very limited successes. An emerging opportunity arises from the use of decellularized ECM as a scaffolding material that, directly or in combination with other materials, has greatly facilitated the advancement of tissue engineering. Here we focused on the decellularized matrix obtained from human umbilical cord Wharton's jelly (DWJ) which retains several structural and bioactive molecules very similar to those of the IVD ECM. However, being a viscous gel, DWJ has limited ability to retain ordered structural features when considered as architecture scaffold. To overcome this limitation, we produced DWJ-based multifunctional hydrogels, in the form of 3D millicylinders containing different percentages of alginate, a seaweed-derived polysaccharide, and gelatin, denatured collagen, which may impart mechanical integrity to the biologically active DWJ. The developed protocol, based on a freezing step, leads to the consolidation of the entire polymeric dispersion mixture, followed by an ionic gelation step and a freeze-drying process. Finally, a porous, stable, easily storable, and suitable matrix for ex vivo experiments was obtained. The properties of the millicylinders (Wharton's jelly millicylinders [WJMs]) were then tested in culture of degenerated IVD cells isolated from disc tissues of patients undergoing surgical discectomy. We found that WJMs with the highest percentage of DWJ were effective in supporting cell migration, restoration of the IVD phenotype (increased expression of Collagen type 2, aggrecan, Sox9 and FOXO3a), anti-inflammatory action, and stem cell activity of resident progenitor/notochordal cells (increased number of CD24 positive cells). We are confident that the DWJ-based formulations proposed here can provide adequate stimuli to the cells present in the degenerated IVD to restart the anabolic machinery.

BRD4 plays an antiaging role in the senescence of renal tubular epithelial cells

Background

Age-related kidney failure is often induced by a decrease in the bioavailability of tubular epithelial cells in elderly chronic kidney disease (CKD) patients. BRD4, an epigenetic regulator and a member of the bromodomain and extraterminal (BET) protein family, acts as a super-enhancer (SE) organizing and regulating genes expression during embryogenesis and cancer development. But the physiological function of BRD4 in normal cells has been less studied. This study aimed to research certain biological roles of BRD4 in the process of normal cell aging and discuss the potential mechanisms.

Methods

In this study, we investigated the biological functions of BRD4 proteins in the aging of renal tubular cells. At first, we used a D-galactose (D-gal) and BRD4 inhibitor (Abbv-075) to replicate kidney senescence in vivo. D-gal and Abbv-075 were then used to measure the aging-related changes, such as changes in cell cycle, β-galactosidase activity, cell migration, and p16 protein expression in vitro. At last, we knocked down and over-expressed BRD4 to investigate the aging-related physiological phenomena in renal tubular cells.

Results

In vitro, D-gal treatment induced noticeable aging-related changes such as inducing cell apoptosis and cell cycle arrest, increasing β-galactosidase activity as well as up-regulating p16 protein expression in primary human tubular epithelial cells. In the aging mice model, D-gal significantly induced renal function impairment and attenuated BRD4 protein expression. At the same time, the BRD4 inhibitor (Abbv-075) was able to mimic D-gal-induced cell senescence. In vivo, Abbv-075 also decreased kidney function and up-regulated p21 protein expression. When we knocked down the expression of BRD4, the senescence-associated β-galactosidase (SA-β-gal) activity increased dramatically, cell migration was inhibited, and the proportion of cells in the G0/G1 phase increased. Additionally, the knockdown also promoted the expression of the senescence-related proteins p16. When the renal tubular cells were overexpressed with BRD4, cell aging-related indicators were reversed in the D-gal-induced cell aging model.

Conclusions

BRD4 appears to have an active role in the aging of renal tubular cells in vivo and in vitro. The findings also suggest that BRD4 inhibitors have potential nephrotoxic effects for oncology treatment. BRD4 may be a potential therapeutic biomarker and drug target for aging-related kidney diseases, which warrants additional studies.

The Survival of Human Intervertebral Disc Nucleus Pulposus Cells under Oxidative Stress Relies on the Autophagy Triggered by Delphinidin

Delphinidin (Delp), a natural antioxidant, has shown promise in treating age-related ailments such as osteoarthritis (OA). This study investigates the impact of delphinidin on intervertebral disc degeneration (IVDD) using human nucleus pulposus cells (hNPCs) subjected to hydrogen peroxide. Various molecular and cellular assays were employed to assess senescence, extracellular matrix (ECM) degradation markers, and the activation of AMPK and autophagy pathways. Initially, oxidative stress (OS)-induced hNPCs exhibited notably elevated levels of senescence markers like p53 and p21, which were mitigated by Delp treatment. Additionally, Delp attenuated IVDD characteristics including apoptosis and ECM degradation markers in OS-induced senescence (OSIS) hNPCs by downregulating MMP-13 and ADAMTS-5 while upregulating COL2A1 and aggrecans. Furthermore, Delp reversed the increased ROS production and reduced autophagy activation observed in OSIS hNPCs. Interestingly, the ability of Delp to regulate cellular senescence and ECM balance in OSIS hNPCs was hindered by autophagy inhibition using CQ. Remarkably, Delp upregulated SIRT1 and phosphorylated AMPK expression while downregulating mTOR phosphorylation in the presence of AICAR (AMPK activator), and this effect was reversed by Compound C, AMPK inhibitor. In summary, our findings suggest that Delp can safeguard hNPCs from oxidative stress by promoting autophagy through the SIRT1/AMPK/mTOR pathway.

TNFR1-mediated senescence and lack of TNFR2-signaling limit human intervertebral disc cell repair in back pain conditions

Poor intervertebral disc (IVD) healing causes IVD degeneration (IVDD) and progression to herniation and back pain. This study identified distinct roles of TNFα-receptors (TNFRs) in contributing to poor healing in painful IVDD. We first isolated IVDD tissue of back pain subjects and determined the complex pro-inflammatory mixture contained many chemokines for recruiting inflammatory cells. Single-cell RNA-sequencing of human IVDD tissues revealed these pro-inflammatory cytokines were dominantly expressed by a small macrophage-population. Human annulus fibrosus (hAF) cells treated with IVDD-conditioned media (CM) underwent senescence with greatly reduced metabolic rates and limited inflammatory responses. TNFR1 inhibition partially restored hAF cell metabolism sufficiently to enable a robust chemokine and cytokine response to CM. We showed that the pro-reparative TNFR2 was very limited on hIVD cell membranes so that TNFR2 inhibition with blocking antibodies or activation using Atsttrin had no effect on hAF cells with CM challenge. However, TNFR2 was expressed in high levels on macrophages identified in scRNA-seq analyses, suggesting their role in repair responses. Results therefore point to therapeutic strategies for painful IVDD involving immunomodulation of TNFR1 signaling in IVD cells to enhance metabolism and enable a more robust inflammatory response including recruitment or delivery of TNFR2 expressing immune cells to enhance IVD repair.

MINK1 deficiency stimulates nucleus pulposus cell pyroptosis and exacerbates intervertebral disc degeneration

Intervertebral disc (IVD) degeneration, induced by aging and irregular mechanical strain, is highly prevalent in the elderly population, serving as a leading cause of chronic low back pain and disability. Evolving evidence has revealed the involvement of nucleus pulposus (NP) pyroptosis in the pathogenesis of IVD degeneration, while the precise regulatory mechanisms of NP pyroptosis remain obscure. Misshapen/Nck-interacting kinase (NIK)-related kinase 1 (MINK1), a serine-threonine protein kinase, has the potential to modulate the activation of NLRP3 inflammasome, indicating its pivotal role in governing pyroptosis. In this study, to assess the significance of MINK1 in NP pyroptosis and IVD degeneration, NP tissues from patients with varying degrees of IVD degeneration, and IVD tissues from both aging-induced and lumbar spine instability (LSI) surgery-induced IVD degeneration mouse models, with or without MINK1 ablation, were meticulously evaluated. Our findings indicated a notable decline in MINK1 expression in NP tissues of patients with IVD degeneration and both mouse models as degeneration progresses, accompanied by heightened matrix degradation and increased NP pyroptosis. Moreover, MINK1 ablation led to substantial activation of NP pyroptosis in both mouse models, and accelerating ECM degradation and intensifying the degeneration phenotype in mechanically stress-induced mice. Mechanistically, MINK1 deficiency triggered NF-κB signaling in NP tissues. Overall, our data illustrate an inverse correlation between MINK1 expression and severity of IVD degeneration, and the absence of MINK1 stimulates NP pyroptosis, exacerbating IVD degeneration by activating NF-κB signaling, highlighting a potential innovative therapeutic target in treating IVD degeneration.

Injectable Ozone-Rich Nanocomposite Hydrogel Loaded with D-Mannose for Anti-Inflammatory and Cartilage Protection in Osteoarthritis Treatment

Osteoarthritis (OA) is a dynamic condition characterized by cartilage damage and synovial inflammation. Ozone (O3) shows potential therapeutic effects owing to its anti-inflammatory properties; however, its high reactivity and short half-life substantially limit its effectiveness in OA treatment. In this study, an ozone-rich thermosensitive nanocomposite hydrogel loaded with D-mannose is developed for OA treatment. Briefly, O3 is encapsulated in nanoparticles (NPs) composed of perfluorotributylamine and fluorinated hyaluronic acid to improve its stability. Next, D-mannose is conjugated with α-amino of the hydroxypropyl chitin (HPCH) via Schiff base to prepare MHPCH. These nanoparticles are encapsulated in MHPCH to produce O3 NPs@MHPCH. In vitro cell experiments demonstrate that the O3 NPs@MHPCH treatment significantly reduced VEGF and inflammation levels, accompanied by a decrease in inflammatory factors such as IL-1β, IL-6, TNF-α, and iNOS. Furthermore, O3 NPs@MHPCH promotes the expression of collagen II and aggrecan and stimulates chondrocyte proliferation. Additionally, in vivo studies show that O3 NPs@MHPCH significantly alleviated OA by reducing synovial inflammation, cartilage destruction, and subchondral bone remodeling. O3 NPs@MHPCH offers a promising option for improving the efficacy of O3 therapy and reducing the risk of synovial inflammation and cartilage degeneration in OA.

PGC1α-Inducing Senomorphic Nanotherapeutics Functionalized with NKG2D-Overexpressing Cell Membranes for Intervertebral Disc Degeneration

Cellular senescence is a significant contributor to intervertebral disc aging and degeneration. However, the application of senotherapies, such as senomorphics targeting senescence markers and the senescence-associated secretory phenotype (SASP), remains limited due to challenges in precise delivery. Given that the natural killer group 2D (NKG2D) ligands are increased on the surface of senescent nucleus pulposus (NP) cells, the NKG2D-overexpressing NP cell membranes (NNPm) are constructed, which is expected to achieve a dual targeting effect toward senescent NP cells based on homologous membrane fusion and the NKG2D-mediated immunosurveillance mechanism. Then, mesoporous silica nanoparticles carrying a peroxisome proliferator-activated receptor-ɣ coactivator 1α (PGC1α)inducer (SP) are coated with NNPm (SP@NNPm) and it is found that SP@NNPm selectively targets senescent NP cells, and the SP cores exhibit pH-responsive drug release. Moreover, SP@NNPm effectively induces PGC1α-mediated mitochondrial biogenesis and mitigates senescence-associated markers induced by oxidative stress and the SASP, thereby alleviating puncture-induced senescence and disc degeneration. This dual-targeting nanotherapeutic system represents a novel approach to delivery senomorphics for disc degeneration treatment.

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

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

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

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

Irisin influences the in vitro differentiation of human mesenchymal stromal cells, promoting a tendency toward beiging adipogenesis

Mammals exhibit two distinct types of adipose depots: white adipose tissue (WAT) and brown adipose tissue (BAT). While WAT primarily functions as a site for energy storage, BAT serves as a thermogenic tissue that utilizes energy and glucose consumption to regulate core body temperature. Under specific stimuli such as exercise, cold exposure, and drug treatment, white adipocytes possess a remarkable ability to undergo transdifferentiation into brown-like cells known as beige adipocytes. This transformation process, known as the "browning of WAT," leads to the acquisition of new morphological and physiological characteristics by white adipocytes. We investigated the potential role of Irisin, a 12 kDa myokine that is secreted in mice and humans by skeletal muscle after physical activity, in inducing the browning process in mesenchymal stromal cells (MSCs). A subset of the MSCs possesses the remarkable capability to differentiate into different cell types such as adipocytes, osteocytes, and chondrocytes. Consequently, comprehending the effects of Irisin on MSC biology becomes a crucial factor in investigating antiobesity medications. In our study, the primary objective is to evaluate the impact of Irisin on various cell types engaged in distinct stages of the differentiation process, including stem cells, committed precursors, and preadipocytes. By analyzing the effects of Irisin on these specific cell populations, our aim is to gain a comprehensive understanding of its influence throughout the entire differentiation process, rather than solely concentrating on the final differentiated cells. This approach enables us to obtain insights into the broader effects of Irisin on the cellular dynamics and mechanisms involved in adipogenesis.

Prognostic value and potential mechanism of cellular senescence and tumor microenvironment in hepatocellular carcinoma: Insights from bulk transcriptomics and single-cell sequencing analysis

The high mortality rate and postoperative recurrence of hepatocellular carcinoma (HCC) contribute to the burden on society and healthcare. The prognostic value and underlying mechanisms of cellular senescence and tumor microenvironment (TME) in HCC remain unclear. Bulk transcriptomic data were obtained from 368 HCC samples in The Cancer Genome Atlas-liver hepatocellular carcinoma cohort and 64 samples from the GSE116174 dataset. Single-cell RNA sequencing (scRNA-seq) data of HCC were obtained from the GSE149614 dataset, including 18 tumor samples from 10 patients. Prognosis-related cellular senescence genes and immune cells were identified through univariate analysis. Least absolute shrinkage and selection operator regression analysis was performed to construct the CellAge score and TME score, both of which were identified as independent prognostic factors for HCC based on multivariate Cox analysis. The combined CellAge and TME scores showed improved prognostic stratification for HCC patients, as confirmed by multivariate Cox analysis (p < .001). The gene set enrichment analysis (GSEA) revealed enrichment of the extracellular matrix receptor interaction signaling pathway in the group with high CellAge scores and low TME scores, which exhibited a worse prognosis. Single-cell sequencing results revealed higher expression activity of the cAMP response element modulator (CREM) extended transcription factor in HCC cells and most immune cells, indicating its involvement in TME remodeling. Finally, the tumor immune dysfunction and exclusion (TIDE) analysis demonstrated that the combined scores could predict the outcomes of immune therapy in patients with HCC. In conclusion, cellular senescence contributes to TME remodeling in HCC, and the developed CellAge and TME scores serve as independent prognostic factors and predictors of immune therapy in HCC.

Impact of autophagy inhibition on intervertebral disc cells and extracellular matrix

Background

Intervertebral disc degeneration (IDD) is a leading contributor to low back pain (LBP). Autophagy, strongly activated by hypoxia and nutrient starvation, is a vital intracellular quality control process that removes damaged proteins and organelles to recycle them for cellular biosynthesis and energy production. While well-established as a major driver of many age-related diseases, autophagy dysregulation or deficiency has yet been confirmed to cause IDD.

Methods

In vitro, rat nucleus pulposus (NP) cells treated with bafilomycin A1 to inhibit autophagy were assessed for glycosaminoglycan (GAG) content, proteoglycan synthesis, and cell viability. In vivo, a transgenic strain (Col2a1-Cre; Atg7 fl/fl) mice were successfully generated to inhibit autophagy primarily in NP tissues. Col2a1-Cre; Atg7 fl/fl mouse intervertebral discs (IVDs) were evaluated for biomarkers for apoptosis and cellular senescence, aggrecan content, and histological changes up to 12 months of age.

Results

Here, we demonstrated inhibition of autophagy by bafilomycin produced IDD features in the rat NP cells, including increased apoptosis and cellular senescence (p21 CIP1) and decreased expression of disc matrix genes Col2a1 and Acan. H&E histologic staining showed significant but modest degenerative changes in NP tissue of Col2a1-Cre; Atg7 fl/fl mice compared to controls at 6 and 12 months of age. Intriguingly, 12-month-old Col2a1-Cre; Atg7 fl/fl mice did not display increased loss of NP proteoglycan. Moreover, markers of apoptosis (cleaved caspase-3, TUNEL), and cellular senescence (p53, p16 INK4a , IL-1β, TNF-α) were not affected in 12-month-old Col2a1-Cre; Atg7 fl/fl mice compared to controls. However, p21 CIP1and Mmp13 gene expression were upregulated in NP tissue of 12-month-old Col2a1-Cre; Atg7 fl/fl mice compared to controls, suggesting p21 CIP1-mediated cellular senescence resulted from NP-targeted Atg7 knockout might contribute to the observed histological changes.

Conclusion

The absence of overt IDD features from disrupting Atg7-mediated macroautophagy in NP tissue implicates other compensatory mechanisms, highlighting additional research needed to elucidate the complex biology of autophagy in regulating age-dependent IDD.