p16 deficiency attenuates intervertebral disc degeneration by adjusting oxidative stress and nucleus pulposus cell cycle

Identification and Validation of Circadian Rhythm-Related Genes Involved in Intervertebral Disc Degeneration and Analysis of Immune Cell Infiltration via Machine Learning

Background

Low back pain is a significant burden worldwide, and intervertebral disc degeneration (IVDD) is identified as the primary cause. Recent research has emphasized the significant role of circadian rhythms (CRs) and immunity in affecting intervertebral discs (IVD). However, the influence of circadian rhythms and immunity on the mechanism of IVDD remains unclear. This study aimed to identify and validate key rhythm-related genes in IVDD and analyze their correlation with immune cell infiltration.

Methods

Two gene expression profiles related to IVDD and rhythm-related genes were obtained from the Gene Expression Omnibus and GeneCards databases to identify differentially expressed rhythm-related genes (DERGs). Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) and gene set enrichment analysis (GSEA) were conducted to explore the biological functions of these genes. LASSO regression and SVM algorithms were employed to identify hub genes. We subsequently investigated the correlation between hub rhythm-related genes and immune cell infiltration. Finally, nucleus pulposus-derived mesenchymal stem cells (NPMSCs) were isolated from normal and degenerative human IVD tissues. Hub rhythm-related genes expression in NPMSCs was confirmed by real-time quantitative PCR (RT-qPCR).

Results

Six hub genes related to CRs (CCND1, FOXO1, FRMD8, NTRK2, PRRT1, and TFPI) were screened out. Immune infiltration analysis revealed that the IVDD group had significantly more M0 macrophages and significantly fewer follicular helper T cells than those of the control group. Specifically, M0 macrophages were significantly associated with FRMD8, PRRT1, and TFPI. T follicular helper cells were significantly associated with FRDM8, FOXO1, and CCND1. We further confirmed that CCND1, FRMD8, NTRK2, and TFPI were dysrhythmic within NPMSCs from degenerated IVD in vitro.

Conclusion

Six genes (CCND1, FOXO1, FRMD8, NTRK2, PRRT1 and TFPI) linked to circadian rhythms associated with IVDD progression, together with immunity. The identification of these DEGs may provide new insights for the diagnosis and treatment of IVDD.

Engineering Intervertebral Disc Regeneration: Biomaterials, Cell Sources and Animal Models

Intervertebral disc (IVD) degeneration is an age-related problem triggering chronic spinal issues, such as low back pain and IVD herniation. Standard surgical treatment for such spinal issues is the removal of the degenerated or herniated IVD and fusion of adjacent vertebrae to stabilise the joint and locally decompress the spinal cord and/or nerve roots to relieve pain. However, a key challenge of current surgical strategies is the increasing risk of adjacent segment degeneration due to the disruption of native biomechanics of the functional spinal unit, dominated by the loss of the IVD. In the past two decades, research has focused on developing a number of bioengineering approaches to repair and regenerate the IVD; in particular, tissue engineering of the IVD, using bioscaffolds and stem cells represents a promising area. This review highlights the current tissue engineering approaches utilising biomaterials, animal models and cell sources for IVD regeneration and discusses future opportunities.

Role of oxidative stress in intervertebral disc degeneration: mechanisms, pathogenesis, and therapeutic strategies

Intervertebral disc degeneration (IDD) is a prevalent and debilitating spinal condition, characterised by the progressive degradation of disc structure and function, often accompanied by pain. Despite our increasing understanding of IDD, the precise mechanisms underlying its development and potential therapeutic targets remain incompletely understood. Recent research has highlighted that oxidative stress, along with immune abnormalities, mechanical loading imbalances, and metabolic disruptions, play a pivotal role in IDD initiation and progression. Oxidative stress in IDD results from an overproduction of reactive oxygen species (ROS) and a compromised ability to eliminate them, disrupting the redox homeostasis within the intervertebral disc. This disturbance in redox balance leads to extracellular matrix degradation (ECM), induces cellular apoptosis, and worsens the damage to disc tissues. This review provides a comprehensive overview of the pathophysiological processes of IDD, with a particular focus on the role of oxidative stress. Additionally, we explore current advancements in therapeutic strategies targeting oxidative stress, including antioxidant drugs, biomaterials, and stem cell-based approaches, offering promising avenues for the management and treatment of IDD.

Upregulated CEMIP promotes intervertebral disc degeneration via AP-1-mediated change in chromatin accessibility

BACKGROUND

Intervertebral disc degeneration (IDD), a chronic and multifactorial skeletal disorder, is the primary cause of low back pain. It results in reduced disc height and nucleus pulposus hydration due to proteoglycan loss and nucleus pulposus cells (NPCs) dysfunction within a hypoxic microenvironment. Metabolic dysregulation initiates catabolic processes, leading to extracellular matrix (ECM) degradation and compromising disc biomechanical integrity. Emerging evidence highlights epigenetic modifications as pivotal in IDD, influencing NPC gene expression transcriptionally and post-transcriptionally.

METHODS

In order to understand the epigenetic underpinnings of IDD, our study provided a comprehensive profile of chromatin accessibility changes in degenerated NPCs using Assay for Transposase-Accessible Chromatin with high-throughput sequencing (ATAC-seq).

RESULTS

With motif enrichment analysis, we identified the activator protein-1 (AP-1) transcription factor critical in driving the chromatin accessibility changes during IDD. Integrative ATAC-seq and transcriptional profiling revealed cell migration-inducing protein (CEMIP) as a key biomarker and contributor to IDD, exhibiting marked upregulation in IDD. Furthermore, we demonstrated that the AP-1 family, especially, c-Fos, orchestrates the upregulation of CEMIP. Elevated CEMIP plasma levels correlated with clinical IDD severity, and CEMIP knockout mice demonstrated improved IDD.

CONCLUSIONS

Mechanistically, CEMIP disrupted ECM homeostasis through its regulation of high molecular weight hyaluronic acid (HMW-HA) degradation, and its contribution to fibrotic changes. Our findings highlight CEMIP's vital role in IDD and identify the AP-1 family as a critical regulator of IDD, providing new potential therapeutic targets for novel IDD interventions.

KEY POINTS

Integrative ATAC-seq and transcriptional profiling revealed CEMIPas a key biomarker and contributor to IDD, exhibiting marked upregulation in IDD. Further, we demonstrated that the AP-1 family, especially, c-Fos, orchestrates the upregulation of CEMIP. Elevated CEMIP plasma levels correlated with clinical IDD severity, and CEMIP knockout mice demonstrated improved IDD. Mechanistically, CEMIP disrupted extracellular matrix homeostasis through its regulation of high molecular weight hyaluronic acid degradation, and its contribution to fibrotic changes. Our findings offer new avenues for IDD treatment strategies, with the potential to alleviate the global burden of back pain.

REDOX Imbalance and Oxidative Stress in the Intervertebral Disc: The Effect of Mechanical Stress and Cigarette Smoking on ER Stress and Mitochondrial Dysfunction

Low back pain is a widespread condition that significantly impacts quality of life, with intervertebral disc degeneration (IDD) being a major contributing factor. However, the underlying mechanisms of IDD remain poorly understood, necessitating further investigation. Environmental risk factors, such as mechanical stress and cigarette smoke, elevate reactive oxygen species levels from both endogenous and exogenous sources, leading to redox imbalance and oxidative stress. The endoplasmic reticulum (ER) and mitochondria, two key organelles responsible for protein folding and energy production, respectively, are particularly vulnerable to oxidative stress. Under oxidative stress conditions, ER stress and mitochondrial dysfunction occur, resulting in unfolded protein response activation, impaired biosynthetic processes, and disruptions in the tricarboxylic acid cycle and electron transport chain, ultimately compromising energy metabolism. Prolonged and excessive ER stress can further trigger apoptosis through ER-mitochondrial crosstalk. Given the unique microenvironment of the intervertebral disc (IVD)-characterized by hypoxia, glucose starvation, and region-specific cellular heterogeneity-the differential effects of environmental stressors on distinct IVD cell populations require further investigation. This review explores the potential mechanisms through which environmental risk factors alter IVD cell activities, contributing to IDD progression, and discusses future therapeutic strategies aimed at mitigating disc degeneration.

CDKN2A Low cancer cells outcompete macrophages for microenvironmental zinc to drive immunotherapy resistance

Approximately 50% of cancers exhibit decreased CDKN2A expression ( CDKN2A Low ), which is linked to immune checkpoint blockade (ICB) resistance. While CDKN2A is traditionally recognized as a tumor suppressor and cell cycle regulator, we have previously put forth a new paradigm demonstrating its role in intracellular metabolic reprogramming. Whether the metabolic derangement due to CDKN2A loss alters metabolites within the tumor microenvironment (TME) and how that affects the immune compartment and ICB response has never been investigated. Here we found that CDKN2A Low cancer cells reorganize zinc compartmentalization by upregulating the zinc importer SLC39A9 in the plasma membrane, leading to intracellular zinc accumulation in cancer cells and concurrent zinc depletion in the TME. This competition for zinc results in zinc-starved tumor-associated macrophages (TAMs), leading to reduced phagocytic activity. Increasing zinc in TAMs through multiple approaches, including a dietary intervention that increases availability of TME zinc, re-educates these TAMs to a pro-phagocytic phenotype. Remarkably, both knockdown of Slc39a9 in cancer cells or providing a high zinc diet sensitizes Cdkn2a Low tumors to ICB. TAMs, not T cells, are indispensable for ICB response. Clinically, TAMs from CDKN2A Low cancer patients have decreased zinc signatures, corresponding to reduced phagocytosis signatures. Moreover, patients with low circulating zinc levels have reduced time-to-event outcomes compared to those with higher zinc levels. Our work reveals a previously unrecognized mechanism through which CDKN2A Low cancer cells outcompete TAMs for zinc, directly disrupting their function and ICB efficacy.

Stone L, Haglund L. 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.

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.

Fuzi decoction ameliorates intervertebral disc degeneration through ferroptosis modulation by suppressing NF-κB pathway

BACKGROUND AND OBJECTIVES

Intervertebral disc degeneration (IVDD) is a complex condition that necessitates the development of novel therapeutic strategies. The objective of this study was to investigate the therapeutic potential of Fuzi decoction (FZD) in the treatment of IVDD by examining its bioactive components, target genes, molecular interactions, pathways, and therapeutic efficacy.

METHODS

Bioactive ingredients with an oral bioavailability (OB) of ≥ 30 % and drug likeness (DL) of ≥ 0.18 were identified using the Traditional Chinese Medicine Systems Pharmacology (TCMSP) database. Target genes associated with IVDD were retrieved from various databases, and a Venn diagram was employed to determine the common targets between IVDD and FZD. Subsequent network analyses, including ingredient-target-disease networks and protein-protein interaction (PPI) networks, were constructed. Functional enrichment analyses, such as Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG), were conducted to delineate the biological processes, pathways, and potential mechanisms. Molecular docking was utilized to validate the interactions between FZD ingredients and target genes. In vitro assays using nucleus pulposus cells (NPCs) evaluated the effects of FZD-containing serum (FCS) on extracellular matrix (ECM) degradation, ferroptosis, and NF-κB pathway modulation. Additionally, rat models were used to confirm the therapeutic effects of FZD on IVDD.

RESULTS

FZD was found to contain 77 bioactive ingredients and 108 related targets, with 101 common targets identified between IVDD and FZD. Network analyses pinpointed key ingredients and targets, with a particular focus on PTGS2 and IL1B as central to IVDD. Enrichment analyses revealed pathways related to reactive oxygen species and NF-κB signaling. Molecular docking confirmed robust interactions between core ingredients and target proteins. Pharmacological findings were substantiated by in vitro and in vivo experiments, demonstrating that FCS alleviated IL-1β-induced ECM degradation and ferroptosis by inhibiting the NF-κB pathway in NPCs.

CONCLUSIONS

FZD demonstrates efficacy in alleviating IVDD by regulating ECM degradation and ferroptosis through the suppression of the NF-κB signaling pathway. These findings suggest that FZD may be a promising therapeutic agent for the treatment of IVDD, offering insights into its multifaceted mechanisms and molecular interactions for potential clinical application.

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.

Multiple outcomes of the germline p16INK4a mutation affecting senescence and immunity in human skin

The integrated behaviour of multiple senescent cell types within a single human tissue leading to the development of malignancy is unclear. Patients with Familial Melanoma Syndrome (FMS) have heterozygous germline defects in the CDKN2A gene coding for the cyclin inhibitor p16INK4a. Melanocytes within skin biopsies from FMS patients express significantly less p16INK4a but express higher levels of the DNA-damage protein 𝛾H2AX a than fibroblastic cells. However, patient fibroblasts also exhibit defects since senescent cells do not increase in the skin during ageing and fibroblasts isolated from the skin of patients have increased replicative capacity compared to control fibroblasts in vitro, culminating in abnormal nuclear morphology. Patient derived fibroblasts also secreted less SASP than control cells. Predisposition of FMS patients to melanoma may therefore result from integrated dysregulation of senescence in multiple cell types in vivo. The inherently greater levels of DNA damage and the overdependence of melanocytes on p16 for cell cycle inhibition after DNA damage makes them exquisitely susceptible to malignant transformation. This may be accentuated by senescence-related defects in fibroblasts, in particular reduced SASP secretion that hinders recruitment of T cells in the steady state and thus reduces cutaneous immunosurveillance in vivo.

MicroSphere 3D Structures Delay Tissue Senescence through Mechanotransduction

The extracellular matrix (ECM) stores signaling molecules and facilitates mechanical and biochemical signaling in cells. However, the influence of biomimetic "rejuvenation" ECM structures on aging- and degeneration-related cellular activities and tissue repair is not well understood. We combined physical extrusion and precise "on-off" alternating cross-linking methods to create anisotropic biomaterial microgels (MicroRod and MicroSphere) and explored how they regulate the cell activities of the nucleus pulposus (NP) and their potential antidegenerative effects on intervertebral discs. NP cells exhibited aligned growth along the surface of the MicroRod, enhanced proliferation, and reduced apoptosis. This suggests an adaptive cellular response involving adhesion and mechanosensing, which causes cytoskeletal extension via environmental cues. NP cells maintain nuclear membrane integrity through the YAP/TAZ pathway, which activates the cGAS-STING pathway to rectify the aging mechanisms. In vivo, MicroRod carries NP cells and reduces inflammatory factor and protease secretion in degenerated intervertebral discs, inhibiting degeneration and promoting NP tissue regeneration. Our findings highlight the role of mechanical stress in maintaining cellular activity and antiaging effects in harsh environments, providing a foundation for further research and development of antidegenerative biomaterials.

The mTOR pathway is involved in the process of platelet-rich plasma improving intervertebral disc degeneration

Objectives

Platelet-rich plasma (PRP) contains multiple growth hormones that may stimulate tissue repair. We aimed to assess PRP's efficacy and explore possible mechanisms using the intervertebral disc degeneration (IDD) model.

Materials and Methods

A total of 48 male Sprague-Dawley (SD) rats were randomly divided into three groups: sham, IDD+PBS, and IDD+PRP (n=16, respectively). IL-1β (10 ng/ml) was used to establish a humanized IDD model in human lumbar nucleus pulposus (NP) tissues from 36 patients with degenerative disc disease. These NP cells were randomly divided into three groups: sham, IDD+PBS, and IDD+PRP (n=12, respectively). RT-PCR and western blot were used to detect the expression of aggrecan, collagen II, IL-1β, IL-6, TNF-α, Bcl-2, cleaved-Caspase 3, Bax and Akt/mTOR/p70S6K signaling pathway. A related assay kit was used to detect MDA, SOD, and GSH.

Results

PRP affected the expression of aggrecan, collagen II, IL-1β, IL-6, TNF-α, MDA, SOD, GSH, Bcl-2, cleaved-Caspase 3, and Bax in IDD rats. Compared with the IDD+PBS group, the expression of p-mTOR, p-p70/S6K, and p-Akt was much lower in the rat IDD+PRP group (P<0.05). Similarly, with PRP treatment in the humanized IDD model, the expression of p-mTOR, p-p70/S6K, and p-Akt was also inhibited.

Conclusion

PRP may be a potential therapy for IDD via the mTOR signaling pathway in regulating and affecting extracellular matrix degradation, inflammatory factors, oxidative stress, and apoptosis.

Sirt1 blocks nucleus pulposus and macrophages crosstalk by inhibiting RelA/Lipocalin 2 axis

Background

Intervertebral disc degeneration (IVDD) stands as a primary pathophysiological driver of low back pain, yet no therapeutic intervention effectively arrests its progression. Evidence shows that certain Sirt1 agonists may confer protective effects on intervertebral discs, but the underlying mechanisms remain unclear. This study aims to delineate the interaction between Sirt1 and the inflammatory microenvironment, offering potential novel avenues for IVDD prevention and treatment.

Methods

In vitro IL-1β-induced nucleus pulposus cells (NPCs) degenerative model and in vivo a mouse annulus fibrosus needle puncture model in Sirt1 transgenic (Sirt1TG) and the same litter WT mice were used to investigate the role of Sirt1 in homeostasis and inflammation. Mechanistic insights were obtained through RNA sequencing, co-immunoprecipitation (Co-IP), luciferase assays, and chromatin immunoprecipitation-(ChIP)-PCR. A co-culture system of Raw264.7 and NPCs was employed to assess the involvement of Lipocalin 2.

Results

Our study demonstrated reduced Sirt1 expression in degenerating human nucleus pulposus (NP) tissue. Both in vitro and in vivo data revealed that NP-specific overexpression of Sirt1 inhibited extracellular matrix degradation and inflammation. Mechanistically, Sirt1 suppressed the acetylation of RelA/p65 at lysine 310 and phosphorylation at serine 536, with the C-terminus of Sirt1 and the RHD-NLS domain of RelA mediating to their interaction. Furthermore, NPCs-derived Lipocalin 2 was identified as a cytokine involved in macrophage chemotaxis and M1 polarization to exacerbate inflammation.

Conclusion

Our work revealed that Sirt1 negatively regulates Lipocalin 2, thereby ameliorating the inflammatory milieu and blocking NPCs and macrophages crosstalk.

The Translational Potential of this Article

This study illuminates the crucial role and molecular mechanisms of Sirt1 in regulating the NP microenvironment. These insights shed light on strategies for the prevention and treatment of IVDD-related herniation and low back pain. By pinpointing specific biological targets, the screening of smallmolecule compounds with significant clinical implications can be facilitated. This translational innovation promises to optimize cells communication within intervertebral disc microenvironment via localized drug delivery, potentially improving patient outcomes and satisfaction following spinal fusion or discectomy surgeries.

Nanotechnology-Enhanced Pharmacotherapy for Intervertebral Disc Degeneration Treatment

Intervertebral disc degeneration (IDD) is a primary contributor to chronic back pain and disability globally, with current therapeutic approaches often proving inadequate due to the complex nature of its pathophysiology. This review assesses the potential of nanoparticle-driven pharmacotherapies to address the intricate challenges presented by IDD. We initially analyze the primary mechanisms driving IDD, with particular emphasis on mitochondrial dysfunction, oxidative stress, and the inflammatory microenvironment, all of which play pivotal roles in disc degeneration. Then, we evaluate the application of metal-phenolic and catalytic nanodots in targeting mitochondrial defects and alleviating oxidative stress within the degenerative disc environment. Additionally, multifunctional and stimuli-responsive nanoparticles are explored for their capacity to provide precise targeting and controlled therapeutic release, offering improved localization and sustained delivery. Finally, we outline future research directions and identify emerging trends in nanoparticle-based therapies, highlighting their potential to significantly advance IDD treatment by overcoming the limitations of conventional therapeutic modalities and enabling more effective, targeted management strategies.

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.

Oxidative stress and cell senescence as drivers of ageing: Chicken and egg

Oxidative stress and cell senescence are both important drivers of ageing and age-associated disease and disability. In vitro, they are closely interconnected in a chicken-and-egg relationship: Not only is oxidative stress an important cause of cell senescence, but senescent cells are also sources of oxidative stress, obscuring cause-effect relationships during the ageing process. We hypothesize that cell senescence is a significant cause of tissue and systemic oxidative stress during ageing. This review aims to critically summarize the available evidence for this hypothesis. After summarizing the cellular feedback mechanisms that make oxidative stress an integral part of the senescent phenotype, it critically reviews the existing evidence for a role of senescent cells as causes of oxidative stress during mammalian ageing in vivo, focussing on results from intervention experiments. It is concluded that while the available data are in agreement with this hypothesis, they are still too scarce to support a robust conclusion.

Reference intervals of adjacent disc height in fresh osteoporotic vertebral compression fractures and the association with postoperative adjacent segment complications: a quantitative study in Chinese postmenopausal women

BACKGROUND

Preoperative adjacent disc height (DH) was found as an independent risk factor for adjacent segment degeneration (ASD) after percutaneous kyphoplasty (PKP), indicating the preoperative status of the adjacent intervertebral discs may be closely related to adjacent segment complications. To establish the reference intervals (RIs) for adjacent DH of fresh osteoporotic vertebral compression fracture (OVCF) in Chinese postmenopausal women, and investigate the association with adjacent segment complications after PKP.

METHODS

Consecutive inpatients diagnosed with fresh OVCF between November 2015 and August 2023 were reviewed. The enrolled patients were divided into subgroups based on injured vertebral level; then, the cranial and caudal DH were measured. The characteristics of DH among subgroups were identified, and specific RIs were established using the indirect Hoffmann method. The associations between DH and adjacent segment complications were assessed using multivariate analysis.

RESULTS

The DH of the cranial disc was significantly lower than the corresponding caudal disc in all vertebral levels, which showed an increasing trend from T11 to L4. The RIs of DH were as follows: T11 (cranial), 2.14-5.14 mm; T11 (caudal), 2.64-5.89 mm; T12 (cranial), 2.69-5.77 mm; T12 (caudal), 3.18-6.57 mm; L1 (cranial), 3.05-6.59 mm; L1 (caudal), 3.40-8.29 mm; L2 (cranial), 3.68-8.36 mm; L2 (caudal), 4.57-9.78 mm; L3 (cranial), 4.53-8.92 mm; L3 (caudal), 5.26-10.07 mm; L4 (cranial), 4.70-11.42 mm; and L4 (caudal), 5.52-12.12 mm. Increased risks of adjacent segment complications after PKP were observed in patients with decreased adjacent DH.

CONCLUSION

The estimated vertebral level and disc level-specific RIs for adjacent DH of fresh OVCF were established in the Chinese postmenopausal women population. A decrease in adjacent DH posed high risks of adjacent segment complications after PKP for treating OVCF.

S1P regulates intervertebral disc aging by mediating endoplasmic reticulum-mitochondrial calcium ion homeostasis

As the aging process progresses, age-related intervertebral disc degeneration (IVDD) is becoming an emerging public health issue. Site-1 protease (S1P) has recently been found to be associated with abnormal spinal development in patients with mutations and has multiple biological functions. Here, we discovered a reduction of S1P in degenerated and aging intervertebral discs, primarily regulated by DNA methylation. Furthermore, through drug treatment and siRNA-mediated S1P knockdown, nucleus pulposus cells were more prone to exhibit degenerative and aging phenotypes. Conditional KO of S1P in mice resulted in spinal developmental abnormalities and premature aging. Mechanistically, S1P deficiency impeded COP II-mediated transport vesicle formation, which leads to protein retention in the endoplasmic reticulum (ER) and subsequently ER distension. ER distension increased the contact between the ER and mitochondria, disrupting ER-to-mitochondria calcium flow and resulting in mitochondrial dysfunction and energy metabolism disturbance. Finally, using 2-APB to inhibit calcium ion channels and the senolytic drug dasatinib and quercetin (D + Q) partially rescued the aging and degenerative phenotypes caused by S1P deficiency. In conclusion, our findings suggest that S1P is a critical factor in causing IVDD in the process of aging and highlight the potential of targeting S1P as a therapeutic approach for age-related IVDD.

Role of oxidative stress in mitochondrial dysfunction and their implications in intervertebral disc degeneration: Mechanisms and therapeutic strategies

Background

Intervertebral disc degeneration (IVDD) is widely recognized as one of the leading causes of low back pain. Intervertebral disc cells are the main components of the intervertebral disc (IVD), and their functions include synthesizing and secreting collagen and proteoglycans to maintain the structural and functional stability of the IVD. In addition, IVD cells are involved in several physiological processes. They help maintain nutrient metabolism balance in the IVD. They also have antioxidant and anti-inflammatory effects. Because of these roles, IVD cells are crucial in IVDD. When IVD cells are subjected to oxidative stress, mitochondria may become damaged, affecting normal cell function and accelerating degenerative changes. Mitochondria are the energy source of the cell and regulate important intracellular processes. As a key site for redox reactions, excessive oxidative stress and reactive oxygen species can damage mitochondria, leading to inflammation, DNA damage, and apoptosis, thus accelerating disc degeneration.

Aim of review

Describes the core knowledge of IVDD and oxidative stress. Comprehensively examines the complex relationship and potential mechanistic pathways between oxidative stress, mitochondrial dysfunction and IVDD. Highlights potential therapeutic targets and frontier therapeutic concepts. Draws researchers' attention and discussion on the future research of all three.

Key scientific concepts of review

Origin, development and consequences of IVDD, molecular mechanisms of oxidative stress acting on mitochondria, mechanisms of oxidative stress damage to IVD cells, therapeutic potential of targeting mitochondria to alleviate oxidative stress in IVDD.

The translational potential of this article

Targeted therapeutic strategies for oxidative stress and mitochondrial dysfunction are particularly critical in the treatment of IVDD. Using antioxidants and specific mitochondrial therapeutic agents can help reduce symptoms and pain. This approach is expected to significantly improve the quality of life for patients. Individualized therapeutic approaches, on the other hand, are based on an in-depth assessment of the patient's degree of oxidative stress and mitochondrial functional status to develop a targeted treatment plan for more precise and effective IVDD management. Additionally, we suggest preventive measures like customized lifestyle changes and medications. These are based on understanding how IVDD develops. The aim is to slow down the disease and reduce the chances of it coming back. Actively promoting clinical trials and evaluating the safety and efficacy of new therapies helps translate cutting-edge treatment concepts into clinical practice. These measures not only improve patient outcomes and quality of life but also reduce the consumption of healthcare resources and the socio-economic burden, thus having a positive impact on the advancement of the IVDD treatment field.

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.

Knocking down EGR1 inhibits nucleus pulposus cell senescence and mitochondrial damage through activation of PINK1-Parkin dependent mitophagy, thereby delaying intervertebral disc degeneration

Mitophagy plays a crucial role in maintaining the homeostasis of intervertebral disc (IVD). Early Growth Response 1 (EGR1), a conservative transcription factor, is commonly upregulated under oxidative stress conditions and participates in regulating cellular senescence, apoptosis, and inflammatory responses. However, the specific role of EGR1 in nucleus pulposus (NP) cell senescence and mitophagy remains unclear. In this study, through bioinformatics analysis and validation using human tissue specimens, we found that EGR1 is significantly upregulated in IVD degeneration (IDD). Further experimental results demonstrate that knockdown of EGR1 inhibits TBHP-induced NP cell senescence and mitochondrial dysfunction while promoting the activation of mitophagy. The protective effect of EGR1 knockdown on NP cell senescence and mitochondrion disappears upon inhibition of mitophagy with mdivi1. Mechanistic studies reveal that EGR1 suppresses NP cell senescence and mitochondrial dysfunction by modulating the PINK1-Parkin dependent mitophagy pathway. Additionally, EGR1 knockdown delays acupuncture-induced IDD in rats. In conclusion, our study demonstrates that under TBHP-induced oxidative stress, EGR1 knockdown mitigates NP cell senescence and mitochondrial dysfunction through the PINK1-Parkin dependent mitophagy pathway, thereby alleviating IDD.

New perspectives on YTHDF2 O-GlcNAc modification in the pathogenesis of intervertebral disc degeneration

This study investigates the potential molecular mechanisms by which O-GlcNAc modification of YTHDF2 regulates the cell cycle and participates in intervertebral disc degeneration (IDD). We employed transcriptome sequencing to identify genes involved in IDD and utilized bioinformatics analysis to predict key disease-related genes. In vitro mechanistic validation was performed using mouse nucleus pulposus (NP) cells. Changes in reactive oxygen species (ROS) and cell cycle were assessed through flow cytometry and CCK-8 assays. An IDD mouse model was also established for in vivo mechanistic validation, with changes in IDD severity measured using X-rays and immunohistochemical staining. Bioinformatics analysis revealed differential expression of YTHDF2 in NP cells of normal and IDD mice, suggesting its potential as a diagnostic gene for IDD. In vitro cell experiments demonstrated that YTHDF2 expression and O-GlcNAcylation were reduced in NP cells under H2O2 induction, leading to inhibition of the cell cycle through decreased stability of CCNE1 mRNA. Further, in vivo animal experiments confirmed a decrease in YTHDF2 expression and O-GlcNAcylation in IDD mice, while overexpression or increased O-GlcNAcylation of YTHDF2 promoted CCNE1 protein expression, thereby alleviating IDD pathology. YTHDF2 inhibits its degradation through O-GlcNAc modification, promoting the stability of CCNE1 mRNA and the cell cycle to prevent IDD formation.

Novel biomarkers associated with oxidative stress and immune infiltration in intervertebral disc degeneration based on bioinformatics approaches

BACKGROUND

The etiology of intervertebral disc degeneration (IVDD), a prevalent degenerative disease in the elderly, remains to be fully elucidated. The objective of this study was to identify immune infiltration and oxidative stress (OS) biomarkers in IVDD, aiming to provide further insights into the intricate pathogenesis of IVDD.

METHODS

The Gene Expression microarrays were obtained from the Gene Expression Omnibus (GEO) database. We conducted enrichment analysis of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) terms. Subsequently, the R language packages CIBERSORT, MCPcounter, and WGCNA were employed to compare immune infiltration levels between IVDD samples and control samples. A protein-protein interaction (PPI) network was constructed using the Search Tools for the Retrieval of Interacting Genes (STRING) database to identify significant gene clusters. To identify hub genes, we employed Cytoscape's Molecular Complex Detection (MCODE) plug-in. The mRNA levels of hub genes in the cell model were validated by qPCR, while Western blotting was used to validate their protein levels.

RESULTS

The GSE70362 dataset from the GEO database identified a total of 1799 genes that were differentially expressed. Among these, 43 genes were found to be differentially expressed and also associated with OS. The differentially expressed genes associated with OS and the immune-related module genes identified through WGCNA were further intersected, resulting in the identification of 10 key genes that were differentially expressed and played crucial roles in both immune response and OS. Subsequently, we validated four diagnostic markers (PPIA, MAP3K5, PXN, and JAK2) using the GSE122429 external dataset. In a cellular model of OS in NP cells, we have identified the upregulation of PPIA and PXN genes, which could serve as novel markers for IVDD.

CONCLUSION

The study successfully identified and validated differentially expressed genes associated with oxidative stress and immune infiltration in IVDD samples compared to normal ones. Notably, the newly discovered biomarkers PPIA and PXN have not been previously reported in IVDD-related research.

A novel spherical GelMA-HAMA hydrogel encapsulating APET×2 polypeptide and CFIm25-targeting sgRNA for immune microenvironment modulation and nucleus pulposus regeneration in intervertebral discs

METHODS

Single-cell transcriptomics and high-throughput transcriptomics were used to screen factors significantly correlated with intervertebral disc degeneration (IDD). Expression changes of CFIm25 were determined via RT-qPCR and Western blot. NP cells were isolated from mouse intervertebral discs and induced to degrade with TNF-α and IL-1β. CFIm25 was knocked out using CRISPR-Cas9, and CFIm25 knockout and overexpressing nucleus pulposus (NP) cell lines were generated through lentiviral transfection. Proteoglycan expression, protein expression, inflammatory factor expression, cell viability, proliferation, migration, gene expression, and protein expression were analyzed using various assays (alcian blue staining, immunofluorescence, ELISA, CCK-8, EDU labeling, transwell migration, scratch assay, RT-qPCR, Western blot). The GelMA-HAMA hydrogel loaded with APET×2 polypeptide and sgRNA was designed, and its effects on NP regeneration were assessed through in vitro and mouse model experiments. The progression of IDD in mice was evaluated using X-ray, H&E staining, and Safranin O-Fast Green staining. Immunohistochemistry was performed to determine protein expression in NP tissue. Proteomic analysis combined with in vitro and in vivo experiments was conducted to elucidate the mechanisms of hydrogel action.

RESULTS

CFIm25 was upregulated in IDD NP tissue and significantly correlated with disease progression. Inhibition of CFIm25 improved NP cell degeneration, enhanced cell proliferation, and migration. The hydrogel effectively knocked down CFIm25 expression, improved NP cell degeneration, promoted cell proliferation and migration, and mitigated IDD progression in a mouse model. The hydrogel inhibited inflammatory factor expression (IL-6, iNOS, IL-1β, TNF-α) by targeting the p38/NF-κB signaling pathway, increased collagen COLII and proteoglycan Aggrecan expression, and suppressed NP degeneration-related factors (COX-2, MMP-3).

CONCLUSION

The study highlighted the crucial role of CFIm25 in IDD and introduced a promising therapeutic strategy using a porous spherical GelMA-HAMA hydrogel loaded with APET×2 polypeptide and sgRNA. This innovative approach offers new possibilities for treating degenerated intervertebral discs.

POSTN promotes nucleus pulposus cell senescence and extracellular matrix metabolism via activing Wnt/β-catenin and NF-κB signal pathway in intervertebral disc degeneration

BACKGROUND

Intervertebral disc (IVD) degeneration (IVDD) is a prevalent condition contributing to back pain and disability. Periostin (POSTN) has emerged as a potential molecular marker and therapeutic target in IVDD, prompting further investigation into its role and mechanisms.

METHODS

This study employs bioinformatics analysis combined with experimental validation to explore the role of POSTN in IVDD. Gene expression datasets from the GEO database were analyzed to identify genes associated with IVDD, and the effects of POSTN on rat nucleus pulposus (NP) cells senescence and extracellular matrix (ECM) metabolism were assessed both in vitro and in vivo.

RESULTS

Elevated POSTN expression was observed in degenerated discs from IVDD patients, correlating with disease severity. In vitro experiments demonstrated that POSTN promotes NP cells senescence and ECM metabolism in a dose- and time-dependent manner. In vivo studies confirmed that POSTN inhibition can ameliorate the progression of IVDD. Further mechanistic insights revealed that POSTN may exert its effects by activating the NF-κB and Wnt/β-catenin signaling pathways.

CONCLUSION

POSTN plays a significant role in the pathogenesis of IVDD, with its upregulated expression closely linked to NP cells senescence and ECM metabolism. Targeting POSTN could offer a novel therapeutic strategy for IVDD. Additionally, the study predicts small molecules that may inhibit POSTN expression, providing potential candidates for the development of new drug treatments.

Progress in the study of molecular mechanisms of intervertebral disc degeneration

Degenerative intervertebral disc disease (IVDD) is one of the main spinal surgery, conditions, which markedly increases the incidence of low back pain and deteriorates the patient's quality of life, and it imposes significant social and economic burdens. The molecular pathology of IVDD is highly complex and multilateral however still not ompletely understood. New findings indicate that IVDD is closely associated with inflammation, oxidative stress, cell injury and extracellular matrix metabolismdysregulation. Symptomatic management is the main therapeutic approach adopted for IVDD, but it fails to address the basic pathological changes and the causes of the disease. However, research is still focusing on molecular aspects in terms of gene expression, growth factors and cell signaling pathways in an attempt to identify specific molecular targets for IVDD treatment. The paper summarizes the most recent achievements in molecularunderstanding of the pathogenesis of IVDD and gives evidence-based recommendations for clinical practice.

Cellular senescence in acute kidney injury: Target and opportunity

Acute kidney injury (AKI) is a common clinical disease with a high incidence and mortality rate. It typically arises from hemodynamic alterations, sepsis, contrast agents, and toxic drugs, instigating a series of events that culminate in tissue and renal damage. This sequence of processes often leads to acute renal impairment, prompting the initiation of a repair response. Cellular senescence is an irreversible arrest of the cell cycle. Studies have shown that renal cellular senescence is closely associated with AKI through several mechanisms, including the promotion of oxidative stress and inflammatory response, telomere shortening, and the down-regulation of klotho expression. Exploring the role of cellular senescence in AKI provides innovative therapeutic ideas for both the prevention and treatment of AKI. Furthermore, it has been observed that targeted removal of senescent cells in vivo can efficiently postpone senescence, resulting in an enhanced prognosis for diseases associated with senescence. This article explores the effects of common anti-senescence drugs senolytics and senostatic and lifestyle interventions on renal diseases, and mentions the rapid development of mesenchymal stem cells (MSCs). These studies have taken senescence-related research to a new level. Overall, this article comprehensively summarizes the studies on cellular senescence in AKI, aiming is to elucidate the relationship between cellular senescence and AKI, and explore treatment strategies to improve the prognosis of AKI.

Inhibition of MAGL attenuates Intervertebral Disc Degeneration by Delaying nucleus pulposus senescence through STING

Intervertebral disc degeneration (IVDD) stands as the primary cause of low back pain (LBP). A significant contributor to IVDD is nucleus pulposus cell (NPC) senescence. However, the precise mechanisms underlying NPC senescence remain unclear. Monoacylglycerol lipase (MAGL) serves as the primary enzyme responsible for the hydrolysis of 2-arachidonoylglycerol (2-AG), breaking down monoglycerides into glycerol and fatty acids. It plays a crucial role in various pathological processes, including pain, inflammation, and oxidative stress. In this study, we utilized a lipopolysaccharide (LPS)-induced NPC senescence model and a rat acupuncture-induced IVDD model to investigate the role of MAGL in IVDD both in vitro and in vivo. Initially, our results showed that MAGL expression was increased 2.41-fold and 1.52-fold within NP tissues from IVDD patients and rats induced with acupuncture, respectively. This increase in MAGL expression was accompanied by elevated expression of p16INK4α. Following this, it was noted that the suppression of MAGL resulted in a notable decrease in the quantity of SA-β-gal-positive cells and hindered the manifestation of p16INK4α and the inflammatory factor IL-1β in NPCs. MAGL inhibition promotes type II collagen (Col-2) expression and inhibits matrix metalloproteinase 13 (MMP13), thereby restoring the balance of extracellular matrix (ECM) metabolism both in vitro and in vivo. A significant role for STING has also been demonstrated in the regulation of NPC senescence by MAGL. The expression of the STING protein was reduced by 57% upon the inhibition of MAGL. STING activation can replicate the effects of MAGL and substantially increase LPS-induced inflammation while accelerating the senescence of NPCs. These results strongly indicate that the inhibition of MAGL can significantly suppress nucleus pulposus senescence via its interaction with STING, consequently restoring the balance of ECM metabolism. This insight provides new perspectives for potential treatments for IVDD.

Kongensin a attenuates intervertebral disc degeneration by inhibiting TAK1-mediated PANoptosis of nucleus pulposus cells

Low back pain (LBP) is most commonly caused by intervertebral disc degeneration (IVDD). Pyroptosis, apoptosis, and necroptosis are crucial in IVDD pathogenesis; however, possible simultaneous occurrence in IVDD and co-regulation between the pathways and the regulatory mechanisms have not been investigated. PANoptosis is a regulated cell death (RCD) pathway with the key characteristics of pyroptosis, apoptosis, and necroptosis. This study revealed that tert-butyl hydroperoxide (TBHP) altered the expression of key proteins involved in PANoptosis in nucleus pulposus cells (NPCs). Furthermore, the natural product Kongensin A (KA), which has potential anti-necrotic and anti-inflammatory properties, inhibited PANoptosis. TAK1, often referred to as mitogen-activated protein kinase kinase kinase 7 (Map3k7), is a key regulator of innate immunity, cell death, inflammation, and cellular homeostasis; however, the physiological roles and regulatory mechanisms underlying IVDD remain unclear. In this study, we discovered that KA can upregulate TAK1 expression in NPCs, -which inhibits PANoptosis by suppressing oxidative stress. In conclusion, our results suggest that KA inhibits PANoptosis and delays IVDD progression in NPCs by upregulating TAK1 expression to maintain mitochondrial redox balance. Consequently, targeting TAK1 may be a promising therapeutic approach for IVDD therapy.

Dynamics of N6-methyladenosine modification during aging and their potential roles in the degeneration of intervertebral disc

Background

The N6-methyladenosine (m6A) dynamics in the progression of intervertebral disc (IVD) aging remain largely unknown. This study aimed to explore the distribution and pattern of m6A modification in nucleus pulpous (NP) tissues of rats at different ages.

Methods

Histological staining and MRI were performed to evaluate the degeneration of IVD. The expression of m6A modifiers was analyzed using qRT-PCR and western blot. Subsequently, methylated RNA immunoprecipitation next generation sequencing and RNA-seq were conducted to identify differences in m6A methylome and transcriptome of NP tissues.

Results

Compared to 2-month-old rats, we found significant changes in the global m6A level and the expression of Mettl3 and FTO in NP tissues from 20-month-old rats. During the progression of NP aging, there were 1126 persistently differentially m6A peaks within 931 genes, and 51 persistently differentially expressed genes. GO and KEGG analyses showed that these m6A peaks and m6A modified genes were mainly engaged in the biological processes and pathways of intervertebral disc degermation (IDD), such as extracellular matrix metabolism, angiogenesis, inflammatory response, mTOR and AMPK signaling pathways. Meanwhile, conjoint analyses and Venn diagram revealed a total of 405 aging related genes contained significant methylation and expression levels in 20-month-old rats in contrast to 2-month-old and 10-month-old rats. Moreover, it was found that four aging related genes with hypermethylated modification including BUB1, CA12, Adamts1, and Adamts4 depicted differentially expressed at protein level, of which BUB1 and CA12 were decreased, while Adamts1 and Adamts4 were increased during the progression of NP aging.

Conclusion

Collectively, this study elucidated the distribution and pattern of m6A modification during the aging of IVD. Furthermore, the m6A modified genes were involved in the IDD related biological processes and pathways. These findings may provide novel insights into the mechanisms and therapies of IDD from the perspective of aging.

Mechanisms and therapeutic strategies for senescence-associated secretory phenotype in the intervertebral disc degeneration microenvironment

As a permanent state of cell cycle arrest, cellular senescence has become an important factor in aging and age-related diseases. As a central regulator of physiology and pathology associated with cellular senescence, the senescence associated secretory phenotype can create an inflammatory and catabolic environment through autocrine and paracrine ways, ultimately affecting tissue microstructure. As an age-related disease, the correlation between intervertebral disc degeneration and cellular senescence has been confirmed by many studies. Various pathological factors in the microenvironment of intervertebral disc degeneration promote senescent cells to produce and accumulate and express excessive senescence associated secretory phenotype. In this case, senescence associated secretory phenotype has received considerable attention as a potential target for delaying or treating disc degeneration. Therefore, we reviewed the latest research progress of senescence associated secretory phenotype, related regulatory mechanisms and intervertebral disc cell senescence treatment strategies. It is expected that further understanding of the underlying mechanism between cellular senescence pathology and intervertebral disc degeneration will help to formulate reasonable senescence regulation strategies, so as to achieve ideal therapeutic effects.

The translational potential of this article

Existing treatment strategies often fall short in addressing the challenge of repairing intervertebral disc Intervertebral disc degeneration（IVD） degeneration. The accumulation of senescent cells and the continuous release of senescence-associated secretory phenotype (SASP) perpetually impede disc homeostasis and hinder tissue regeneration. This impairment in repair capability presents a significant obstacle to the practical clinical implementation of strategies for intervertebral disc degeneration. As a result, we present a comprehensive overview of the latest advancements in research, the associated regulatory mechanisms, and strategies for treating SASP in IVD cells. This article aims to investigate effective interventions for delaying the onset and progression of age-related intervertebral disc degeneration. In an era where the aging population is becoming increasingly prominent, this endeavor holds paramount practical and translational significance.

Comparative Analysis of Autophagy and Apoptosis in Disc Degeneration: Understanding the Dynamics of Temporary-Compression-Induced Early Autophagy and Sustained-Compression-Triggered Apoptosis

The purpose of this study was to investigate the initiation of autophagy activation and apoptosis in nucleus pulposus cells under temporary compression (TC) and sustained compression (SC) to identify ideal research approaches in intervertebral disc degeneration. Various techniques were used: radiography (X-ray), magnetic resonance imaging (MRI), transmission electron microscope (TEM), H&E staining, Masson's trichrome staining, immunohistochemistry (IHC) (LC3, beclin-1, and cleaved caspase-3), and real-time polymerase chain reaction (RT-qPCR) for autophagy-related (beclin-1, LC3, and P62) and apoptosis-related (caspase-3 and PARP) gene expression analysis. X-ray and MRI revealed varying degrees of disc degeneration, ranging from moderate to severe in both groups. The severity was directly linked to compression duration, with SC resulting in notably severe central NP cell degeneration. Surprisingly, TC also caused similar, though less severe, degeneration. Elevated expression of LC3 and beclin-1 was identified after 6 weeks, but it notably declined after 12 weeks. Central NP cells in both groups exhibited increased expression of cleaved caspase-3 that was positively correlated with the duration of SC. TC showed fewer apoptotic markers compared to SC. LC3, beclin-1, and P62 mRNA expression peaked after 6 weeks and declined after 12 weeks in both groups. Cleaved caspase-3 and PARP expression peaked in SC, positively correlating with longer compression duration, while TC showed lower levels of apoptosis gene expression. Furthermore, TEM results revealed different events of the autophagic degradation process after 2 weeks of compression. TCmay be ideal for studying early triggered autophagy-mediated degeneration, while SC may be ideal for studying late or slower-triggered apoptosis-mediated degeneration.

A comparison of bone microarchitectural and transcriptomic changes in murine long bones in response to hindlimb unloading and aging

Age- and disuse-related bone loss both result in decreases in bone mineral density, cortical thickness, and trabecular thickness and connectivity. Disuse induces changes in the balance of bone formation and bone resorption like those seen with aging. There is a need to experimentally compare these two mechanisms at a structural and transcriptomic level to better understand how they may be similar or different. Bone microarchitecture and biomechanical properties were compared between 6- and 22-month-old C57BL/6 J male control mice and 6-month-old mice that were hindlimb unloaded (HLU) for 3 weeks. Epiphyseal trabecular bone was the compartment most affected by HLU and demonstrated an intermediate bone phenotype between age-matched controls and aged controls. RNA extracted from whole-bone marrow-flushed tibiae was sequenced and analyzed. Differential gene expression analysis additionally included 4-month-old male mice unloaded for 3 weeks compared to age-matched controls. Gene ontology analysis demonstrated that there were age-dependent differences in differentially expressed genes in young adult mice. Genes related to downregulation of cellular processes were most affected in 4-month-old mice after disuse whereas those related to mitochondrial function were most affected in 6-month-old mice. Cell-cycle transition was downregulated with aging. A publicly available dataset (GSE169292) from 3-month female C57BL/6 N mice unloaded for 7 days was included in ingenuity pathway analysis (IPA) with the other datasets. IPA was used to identify the leading canonical pathways and upstream regulators in each HLU age group. IPA identified "Senescence Pathway" as the second leading canonical pathway enriched in mice exposed to HLU. HLU induced activation of the senescence pathway in 3-month and 4-month-old mice but inhibited it in 6-month-old mice. In conclusion, we demonstrate that hindlimb unloading and aging initiate similar changes in bone microarchitecture and gene expression. However, aging is responsible for more significant transcriptome and tissue-level changes compared to hindlimb unloading.

Disassembly of the TRIM56-ATR complex promotes cytoDNA/cGAS/STING axis-dependent intervertebral disc inflammatory degeneration

As the leading cause of disability worldwide, low back pain (LBP) is recognized as a pivotal socioeconomic challenge to the aging population and is largely attributed to intervertebral disc degeneration (IVDD). Elastic nucleus pulposus (NP) tissue is essential for the maintenance of IVD structural and functional integrity. The accumulation of senescent NP cells with an inflammatory hypersecretory phenotype due to aging and other damaging factors is a distinctive hallmark of IVDD initiation and progression. In this study, we reveal a mechanism of IVDD progression in which aberrant genomic DNA damage promoted NP cell inflammatory senescence via activation of the cyclic GMP-AMP synthase/stimulator of IFN genes (cGAS/STING) axis but not of absent in melanoma 2 (AIM2) inflammasome assembly. Ataxia-telangiectasia-mutated and Rad3-related protein (ATR) deficiency destroyed genomic integrity and led to cytosolic mislocalization of genomic DNA, which acted as a powerful driver of cGAS/STING axis-dependent inflammatory phenotype acquisition during NP cell senescence. Mechanistically, disassembly of the ATR-tripartite motif-containing 56 (ATR-TRIM56) complex with the enzymatic liberation of ubiquitin-specific peptidase 5 (USP5) and TRIM25 drove changes in ATR ubiquitination, with ATR switching from K63- to K48-linked modification, c thereby promoting ubiquitin-proteasome-dependent dynamic instability of ATR protein during NP cell senescence progression. Importantly, an engineered extracellular vesicle-based strategy for delivering ATR-overexpressing plasmid cargo efficiently diminished DNA damage-associated NP cell senescence and substantially mitigated IVDD progression, indicating promising targets and effective approaches to ameliorate the chronic pain and disabling effects of IVDD.

Bushen Huoxue Formula Inhibits IL-1β-Induced Apoptosis and Extracellular Matrix Degradation in the Nucleus Pulposus Cells and Improves Intervertebral Disc Degeneration in Rats

Background

The method of action of Bushen Formula (BSHXF) in the treatment of intervertebral disc degeneration (IVDD) was uncovered in this work using in vivo and in vitro tests. To clarify the mechanism of action of BSHXF, we validated the rat intervertebral disc degeneration model and the nucleus pulposus cell degeneration model.

Methods

In an in vivo model of IVDD the study explores the impact of BSHXF on mitochondrial function, pro-inflammatory cytokines, pro-apoptotic factors, and matrix metalloproteinases. Additionally, it evaluates the induced degeneration of nucleus pulposus (NP) cells in an in vitro model stimulated by interleukin-1 β (IL-1β). The study measures the effects of BSHXF on both the inflammatory response and mitochondrial function.

Results

The MRI results showed that BSHXF reduced intervertebral disc volume reduction and degradation of NP tissue. HE, SO-FG and immunofluorescence further confirmed the protective effect of BSHXF on degenerative intervertebral discs. BSHXF reduced the inflammatory levels of IL-6 IL-1β and TNF-α in degenerative intervertebral disc tissue. Meanwhile, JC-1, mPTP and ROS detection revealed that BSHXF can restore mitochondrial function by regulating the expression of antioxidant proteins, playing a protective role in NP cells. Finally, the WB results showed that BSHXF can alleviate IL-1β mediate the degeneration of NP cells. BSHXF can alleviate NP cell apoptosis by inhibiting the expression of bax, cleaved caspase-3, caspase-3, and cyt-c, and increasing the expression of Bcl-2.

Conclusion

This study reveals that BSHXF inhibits the development of inflammatory factors, which may play a significant role in intervertebral disc degeneration. This implies that BSHXF is a suitable herbal medication for future research into inflammatory cytokine treatment.

Autophagy-related risk signature based on CDNK2A to facilitate survival prediction of patients with endometrial cancer

BACKGROUND

Autophagy plays an important role in immunity and inflammation. The present study aimed to explore the prognostic significance of autophagy-related genes (ARGs) in endometrial cancer (EC) using bioinformatics.

METHODS

The list of ARGs was obtained from the Human Autophagy Database. The differentially expressed ARGs (DEARGs) between the EC and normal endometrial tissue samples were screened from The Cancer Genome Atlas database. Cox regression analysis was performed on the DEARGs to screen the prognostic ARGs and construct risk signatures for overall survival (OS) and progression-free survival (PFS). The hub ARGs were identified from a protein-protein interaction network, and CDKN2A was obtained from the intersection of prognostic ARGs and hub ARGs. The association of CDKN2A expression with clinical characteristics and immune infiltration were analyzed. Finally, the role of CDKN2A in autophagy was confirmed in EC cell lines.

RESULTS

CDKN2A, PTK6 and DLC1 were used to establish risk signatures for predicting the survival of EC patients. Receiver operating characteristic curve analysis indicated that the risk signatures can accurately predict both OS and PFS. CDKN2A was the only hub prognostic ARG, and showed significant association with the age, survival status, grade, histological type, body mass index and FIGO (i.e. International Federation of Gynecology and Obstetrics) stage (p < 0.05). Furthermore, CDKN2A expression was also correlated with the infiltration of immune cells, indicating that CDKN2A might play a critical role in regulating the immune microenvironment and immune responses in EC. In addition, silencing of CDKN2A gene promoted autophagy in the HEC-1A cell line and upregulated the expression levels of autophagy-related proteins.

CONCLUSIONS

CDKN2A is a prognostic factor and therapeutic target in EC, and is likely associated with the tumor immune landscape and autophagy.

Has-miR-300-GADD45B promotes melanoma growth via cell cycle

Response to oncogenic factors like UV, GADD45 family in skin participates in scavenging ROS, DNA repair and cell cycle control. Because of this, the previous study of the chronic UVB injury model has found that hsa-miR-300 can conduct intercellular transport by exosomes and target regulation of GADD45B. Whether the hsa-miR-300-GADD45B still regulates tumor development by cell cycle pathway is unclear. Through transcriptomic analysis of primary (n=39) and metastatic (n=102) melanoma, it was confirmed that in metastatic samples, some of the 97 down-regulated genes participate in maintaining skin homeostasis while 42 up-regulated genes were enriched in cancer-related functions. Furthermore, CDKN1A, CDKN2A, CXCR4 and RAD51 in the melanoma pathway, were also differentially expressed between normal skin and melanoma. CDKN1A and CDKN2A were also found to be involved in TP53-dependent cell cycle regulation. In conclusion, it was speculated that CDKN1A, CDKN2A, TP53, GADD45B and hsa-miR-300 may have regulatory relationships. It was demonstrated that there is a bidirectional regulation between hsa-miR-300 and TP53. In addition, miR-300 can regulate CDKN1A by GADD45B/TP53 and promote melanoma growth by accelerating the cell cycle transition from G1/S to G2 phase.

Cellular senescence and frailty: a comprehensive insight into the causal links

Senescent cells may have a prominent role in driving inflammation and frailty. The impact of cellular senescence on frailty varies depending on the assessment tool used, as it is influenced by the criteria or items predominantly affected by senescent cells and the varying weights assigned to these items across different health domains. To address this challenge, we undertook a thorough review of all available studies involving gain- or loss-of-function experiments as well as interventions targeting senescent cells, focusing our attention on those studies that examined outcomes based on the individual frailty phenotype criteria or specific items used to calculate two humans (35 and 70 items) and one mouse (31 items) frailty indexes. Based on the calculation of a simple "evidence score," we found that the burden of senescent cells related to musculoskeletal and cerebral health has the strongest causal link to frailty. We deem that insight into these mechanisms may not only contribute to clarifying the role of cellular senescence in frailty but could additionally provide multiple therapeutic opportunities to help the future development of a desirable personalized therapy in these extremely heterogeneous patients.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Multifunctional injectable hydrogels with controlled delivery of bioactive factors for efficient repair of intervertebral disc degeneration

Millions of people worldwide suffer from intervertebral disc degeneration (IVDD), which imposes a significant socioeconomic burden on society. There is an urgent clinical demand for more effective treatments for IVDD because conventional treatments can only alleviate the symptoms rather than preventing the progression of IVDD. Hydrogels, a class of elastic biomaterials with good biocompatibility, are promising candidates for intervertebral disc repair and regeneration. In recent years, various hydrogels have been investigated in vitro and in vivo for the repair of intervertebral discs, some of which are ready for clinical testing. This review summarizes the latest findings and developments in using bioactive factors-released bioactive injectable hydrogels for the repair and regeneration of intervertebral discs. It focuses on the analysis and summary of the use of multifunctional injectable hydrogels to delivery bioactive factors (cells, exosomes, growth factors, genes, drugs) for disc regeneration, providing guidance for future study. Finally, we discussed and analyzed the optimal timing for the application of controlled-release hydrogels in the treatment of IVDD to meet the high standards required for intervertebral disc regeneration and precision medicine.

Hindlimb Unloading Induces Bone Microarchitectural and Transcriptomic Changes in Murine Long Bones in an Age-Dependent Manner

Age and disuse-related bone loss both result in decreases in bone mineral density, cortical thickness, and trabecular thickness and connectivity. Disuse induces physiological changes in bone like those seen with aging. Bone microarchitecture and biomechanical properties were compared between 6- and 22-month-old C57BL/6J male control mice and 6-month-old mice that were hindlimb unloaded (HLU) for 3 weeks. Epiphyseal trabecular bone was the compartment most affected by HLU and demonstrated an intermediate bone phenotype between age-matched controls and aged controls. RNA extracted from whole-bone marrow-flushed tibiae was sequenced and analyzed. Differential gene expression analysis additionally included 4-month-old male mice unloaded for 3 weeks compared to age-matched controls. Gene ontology analysis demonstrated that there were age-dependent differences in differentially expressed genes. Genes related to downregulation of cellular processes were most affected in 4-month-old mice after disuse whereas those related to mitochondrial function were most affected in 6- month-old mice. Cell-cycle transition was downregulated with aging. A publicly available dataset (GSE169292) from 3-month female C57BL/6N mice unloaded for 7 days was included in ingenuity pathway analysis with the other datasets. IPA was used to identify the leading canonical pathways and upstream regulators in each HLU age group. IPA identified "Senescence Pathway" as the second leading canonical pathway enriched in mice exposed to HLU. HLU induced activation of the senescence pathway in 3- month and 4-month-old mice but inhibited it in 6-month-old mice. In conclusion, we demonstrate that hindlimb unloading and aging initiate similar changes in bone microarchitecture and gene expression. However, aging is responsible for more significant transcriptome and tissue-level changes compared to hindlimb unloading.

Highlights

Epiphyseal trabecular bone is most susceptible to hindlimb unloading.Hindlimb unloaded limbs resemble an intermediate phenotype between age-matched and aged controls.Hindlimb unloading induces gene expression changes that are age dependent and may lead to inflammation and/or mitochondrial dysfunction depending on context.Younger mice (3-4 months) activate the senescence pathway upon hindlimb unloading, whereas skeletally mature (6 months) mice inhibit it.

Screening of miR-15a-5p as a potential biomarker for intervertebral disc degeneration through RNA-sequencing

Low back pain (LBP) is a prevalent clinical condition that imposes substantial economic burdens on society. Intervertebral disc degeneration (IVDD) is recognized as a major contributing factor to LBP. Recent studies have highlighted the pivotal role of microRNAs (miRNAs) in regulating the onset and progression of IVDD. Understanding the involvement of miRNAs in IVDD will expand our knowledge of the underlying mechanisms and potentially identify novel therapeutic targets for managing LBP. However, the pathological process of IVDD and the miRNA-mediated pathomechanism in IVDD remain unclear. Herein, we comprehensively analyzed and divided the pathological process of IVDD into three stages based on the analysis by Risbud and colleagues. Results showed that IVDD was especially associated with cell death, oxidative stress, inflammatory and immune response, and extracellular matrix (ECM) metabolism. Subsequently, we obtained human normal and degenerative nucleus pulposus tissues, which were visually confirmed through histological staining techniques such as HE and TUNEL staining. RNA sequencing was then performed on these tissue samples. Additionally, miRNA (GSE116726) and mRNA (GSE56081/GSE70362/GSE23130/GSE34095) datasets were collected from the GEO database. Our analysis revealed that miR-15a-5p was significantly upregulated IVDD, as validated by both RNA sequencing and qRT-PCR experiments. To further refine our findings, bioinformatics analysis was conducted, merging the targets of miR-15a-5p and multiple mRNA datasets, ultimately identifying the overlapping IVDD-associated mRNAs. Notably, many cuproptosis-related genes (CRGs), ferroptosis-related genes, oxidative stress-related genes, and immunity-related genes were potential targets of miR-15a-5p. The miR-15a-5p-mRNA network was constructed using Cytoscape software. Additionally, PPI, functional, and pathway enrichment analyses of the CRGs were also performed. We found that MTF1, one of the CRGs, was highly expressed in IVDD and primarily localized in the nucleus of nucleus pulposus cells. These findings suggest that miR-15a-5p is a potential biomarker in IVDD, and targeting the miR-15a-5p-mRNA signaling pathway may be a promising strategy for treating IVDD diseases.

Lysine methylation of PPP1CA by the methyltransferase SUV39H2 disrupts TFEB-dependent autophagy and promotes intervertebral disc degeneration

Impaired transcription factor EB (TFEB) function and deficient autophagy activity have been shown to aggravate intervertebral disc (IVD) degeneration (IDD), yet the underlying mechanisms remain less clear. Protein posttranslational modifications (PTMs) are critical for determining TFEB trafficking and transcriptional activity. Here, we demonstrate that TFEB activity is controlled by protein methylation in degenerated nucleus pulposus cells (NPCs), even though TFEB itself is incapable of undergoing methylation. Specifically, protein phosphatase 1 catalytic subunit alpha (PPP1CA), newly identified to dephosphorylate TFEB, contains a K141 mono-methylated site. In degenerated NPCs, increased K141-methylation of PPP1CA disrupts its interaction with TEFB and subsequently blocks TEFB dephosphorylation and nuclear translocation, which eventually leads to autophagy deficiency and NPC senescence. In addition, we found that the PPP1CA-mediated targeting of TFEB is facilitated by the protein phosphatase 1 regulatory subunit 9B (PPP1R9B), which binds with PPP1CA and is also manipulated by K141 methylation. Further proteomic analysis revealed that the protein lysine methyltransferase suppressor of variegation 3-9 homologue 2 (SUV39H2) is responsible for the K141 mono-methylation of PPP1CA. Targeting SUV39H2 effectively mitigates NPC senescence and IDD progression, providing a potential therapeutic strategy for IDD intervention.

Senescence-associated alterations in the extracellular matrix: deciphering their role in the regulation of cellular function

The extracellular matrix (ECM) is a dynamic structural network that provides a physical scaffolding, as well as biochemical factors that maintain normal tissue homeostasis and thus its disruption is implicated in many pathological conditions. On the other hand, senescent cells express a particular secretory phenotype, affecting the composition and organization of the surrounding ECM and modulating their microenvironment. As accumulation of senescent cells may be linked to the manifestation of several age-related conditions, senescence-associated ECM alterations may serve as targets for novel anti-aging treatment modalities. Here, we will review characteristic changes in the ECM elicited by cellular senescence and we will discuss the complex interplay between ECM and senescent cells, in relation to normal aging and selected age-associated pathologies.

Kartogenin-enhanced dynamic hydrogel ameliorates intervertebral disc degeneration via restoration of local redox homeostasis

INTRODUCTION

Over-activation of oxidative stress due to impaired antioxidant functions in nucleus pulpous (NP) has been identified as a key factor contributing to intervertebral disc degeneration (IVDD). While Kartogenin (KGN) has previously demonstrated antioxidant properties on articular cartilage against osteoarthritis, its effects on NP degeneration have yet to be fully understood.

OBJECTIVES

This study aimed to investigate the protective effects of KGN on nucleus pulpous cells (NPCs) against an inflammatory environment induced by interleukin (IL)-1β, as well as to explore the therapeutic potential of KGN-enhanced dynamic hydrogel in preventing IVDD.

METHODS

NPCs were isolated from rat caudal IVDs and subjected to treatment with KGN at varying concentrations (ranging from 0.01 to 1 ​μM) in the presence of IL-1β. The expression of extracellular matrix (ECM) anabolism markers was quantitatively assessed at both the mRNA and protein levels. Additionally, intracellular reactive oxygen species and antioxidant enzyme expression were evaluated, along with the role of nuclear factor erythroid 2-related factor 2 (NRF2). Based on these findings, a dynamic self-healing hydrogel loaded with KGN was developed through interconnecting networks. Subsequently, KGN-enhanced dynamic hydrogel was administered into rat caudal IVDs that had undergone puncture injury, followed by radiographic analysis and immunohistochemical staining to evaluate the therapeutic efficacy.

RESULTS

In vitro treatments utilizing KGN were observed to maintain ECM synthesis and inhibit catabolic activities in IL-1β-stimulated NPCs. The mechanism behind this protective effect of KGN on NPCs was found to involve the asctivation of NRF2 and downstream antioxidant enzymes, including glutathione peroxidase 1 and heme oxygenase 1. This was further supported by the loss of both antioxidant and anabolic effects upon pharmacological inhibition of NRF2. Furthermore, a self-healing hydrogel was developed and loaded with KGN to achieve localized and sustained release of the compound. The injection of KGN-enhanced hydrogel effectively ameliorated the degradation of NP ECM and mitigated inflammation in a rat model of puncture-induced IVDD.

CONCLUSIONS

Our results indicate that KGN exhibits potential as a therapeutic agent for NP degeneration, and that KGN-enhanced dynamic hydrogel represents a novel approach for treating IVDD by restoring redox homeostasis in NP.The translational potential of this article: The dysregulation of oxidant and antioxidant balance has been shown to impede the repair and regeneration of NP, thereby hastening the progression of IVDD following injury. The present investigation has demonstrated that the sustained release of KGN promotes the synthesis of ECM in vitro and mitigates the progression of IVDD in vivo by restoring redox equilibrium, thereby presenting a novel therapeutic candidate based on the antioxidant properties of KGN for the treatment of IVDD.

Nacre Extract from Pearl Oyster Shell Prevents D-Galactose-Induced Brain and Skin Aging

Pearl oyster shells comprise two layers, a prismatic and nacreous layer, of calcium carbonate. The nacreous layer has been used in Chinese medicine since ancient times. In this study, we investigated the effects of the extract from the nacreous layer of pearl oysters (nacre extract) on D-galactose-induced brain and skin aging. Treatment with nacre extract led to the recovery of D-galactose-induced memory impairment, as examined using the Barnes maze, novel object recognition, and Y-maze tests. A histological study showed that nacre extract suppressed D-galactose-induced neuronal cell death and the expression of B cell lymphoma 2 (Bcl-2)-associated X protein (Bax), which causes apoptosis in the hippocampus. In addition, the expression levels of brain-derived neurotrophic factor, which counteracts age-related brain dysfunction, and nicotinamide adenine dinucleotide-dependent deacetylase (sirtuin 1), which delays aging and extends lifespan, increased after nacre extract treatment. Moreover, the nacre extract showed anti-aging effects against D-galactose-induced skin aging; it suppressed D-galactose-induced wrinkle formation, decreased skin moisture, decreased epidermal thickness, and destroyed collagen arrangement associated with aging. Furthermore, the nacre extract suppressed oxidative stress associated with aging in the brain and skin by upregulating the expression of catalase and superoxide dismutase. The expression level of the cellular senescence marker p16, which is induced by oxidative stress, was elevated in the hippocampus and skin epidermal layer of D-galactose-treated mice, and it was suppressed by the administration of nacre extract. These results show that the nacre extract can suppress D-galactose-induced aging by enhancing anti-oxidant activity and suppressing p16 expression. Thus, the nacre extract may be an effective anti-aging agent.

A Redox Homeostasis Modulatory Hydrogel with GLRX3+ Extracellular Vesicles Attenuates Disc Degeneration by Suppressing Nucleus Pulposus Cell Senescence

Characterized by nucleus pulposus (NP) cell senescence and extracellular matrix (ECM) degradation, disc degeneration is a common pathology for various degenerative spinal disorders. To date, effective treatments for disc degeneration are absent. Here, we found that Glutaredoxin3 (GLRX3) is an important redox-regulating molecule associated with NP cell senescence and disc degeneration. Using a hypoxic preconditioning method, we developed GLRX3⁺ mesenchymal stem cell-derived extracellular vehicles (EVs-GLRX3), which enhanced the cellular antioxidant defense, thus preventing reactive oxygen species (ROS) accumulation and senescence cascade expansion in vitro. Further, a disc tissue-like biopolymer-based supramolecular hydrogel, which was injectable, degradable, and ROS-responsive, was proposed to deliver EVs-GLRX3 for treating disc degeneration. Using a rat model of disc degeneration, we demonstrated that the EVs-GLRX3-loaded hydrogel attenuated mitochondrial damage, alleviated the NP senescence state, and restored ECM deposition by modulating the redox homeostasis. Our findings suggested that modulation of redox homeostasis in the disc can rejuvenate NP cell senescence and thus attenuate disc degeneration.

BSHXF-medicated serum combined with ADSCs regulates the TGF-β1/Smad pathway to repair oxidatively damaged NPCs and its component analysis

ETHNOPHARMACOLOGICAL RELEVANCE

Lower back pain (LBP) is a common and frequent clinical condition, and intervertebral disc degeneration (IDD) is recognized as the leading cause of LBP, typically manifested by increased nucleus pulposus cell (NPC) senescence and death. In recent years, the treatment of IDD with stem cell injections has had great potential compared to surgical treatment. Combining the two may achieve better results, as BuShenHuoXueFang (BSHXF) is an herbal formula that improves the survival rate of transplanted stem cells and enhances their efficacy.

AIM OF THE STUDY

We aimed to qualitatively and quantitatively analyze BSHXF-medicated serum and investigate the molecular mechanism of BSHXF-mediated serum in promoting the differentiation of adipose mesenchymal stem cells (ADSCs) into NPCs and delaying the senescence of NPCs by regulating the TGF-β1/Smad pathway.

MATERIALS AND METHODS

In this study, an ultrahigh-performance liquid chromatography-quadrupole-time-of-flight mass spectrometer (UPLC-Q-TOF-MS) was used to establish a method for the analysis of rat serum samples to track the active components in vivo; the oxidative damage model of NPCs was induced by T-BHP, and a Transwell chamber was used to construct a coculture system of ADSCs and NPCs. Flow cytometry was used to determine the cell cycle; SA-β-Gal staining was used to assess cell senescence; ELISA was used to detect IL-1β, IL-6 inflammatory factors, CXCL-1, CXCL-3, CXCL-10 chemokines, and TGF-β1 in the supernatants of ADSCs and NPCs. WB was used to detect COL2A1, COL1A1, and Aggrecan in ADSCs to assess the manifestation of NP differentiation in ADSCs, and the WB method was used to detect COL2A1, COL1A1, Aggrecan, p16, p21, p53, and p-p53 protein expression in NPCs to reflect the cellular senescence status and to detect TGF-β1, Smad2, Smad3, p- Smad2, and p- Smad3 protein expression in NPCs to reflect the pathway condition.

RESULTS

We finally identified 70 blood components and their metabolites, including 38 prototypes, from the BSHXF-medicated serum. Compared with that in the nonmedicated serum group, the TGF-β1/Smad pathway was activated in the medicated serum group, ADSCs moved toward NPC characteristics, the number of NPCs in the S/G2M phase increased, the number of senescent NPCs decreased, IL-1β and IL-6 inflammatory factors in the Transwell decreased, CXCL-1, CXCL-3, and CXCL-10 chemokines decreased, and the expression of p16, p21, p53 and p-p53 proteins in NPCs was inhibited.

CONCLUSION

By regulating the TGF-β1/Smad pathway, BSHXF-medicated serum promoted ADSCs to NPCs, effectively alleviated the cycle blockage of NPCs after oxidative damage, encouraged the growth and proliferation of NPCs, delayed the aging of NPCs, improved the deteriorating microenvironment around NPCs, and repaired oxidatively damaged NPCs. The combination of BSHXF or its compounds with ADSCs has great potential for the treatment of IDD in the future.

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

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