Therapy For Intervertebral Disc Degeneration Research Articles

Effects of hydrostatic pressure, osmotic pressure, and confinement on extracellular matrix associated responses in the nucleus pulposus cells ex vivo

Spinal movement in both upright and recumbent positions generates changes in physicochemical stresses including hydrostatic pressure (HP), deviatoric stress, and confinement within the intradiscal compartment. The nucleus pulposus (NP) of the intervertebral disc is composed of highly negatively charged extracellular matrix (ECM), which increases osmotic pressure (OP) and generates tissue swelling. In pursuing regenerative therapies for intervertebral disc degeneration, the effects of HP on the cellular responses of NP cells and the ECM environment remain incompletely understood. We hypothesized that anabolic turnover of ECM in NP tissue is maintained under HP and confinement. We first clarified the effects of the relationships among HP, OP, and confinement on swelling NP explants isolated from bovine caudal intervertebral discs over 12 hours. We found that the application of confinement and constant HP significantly inhibits the free swelling of NP (p < 0.01) and helps retain the sulfated glycosaminoglycan. Since confinement and HP inhibited swelling, we incubated confined NPs under HP in high-osmolality medium mimicking ECM-associated OP for 7 days and demonstrated the effects of HP on metabolic turnover of ECM molecules in NP cells. The aggrecan core protein gene was significantly upregulated under confinement and constant HP compared to confinement and no HP (p < 0.01). We also found that confinement and constant HP helped to significantly retain smaller cell area (p < 0.01) and significantly prevent the severing of actin filaments compared to no confinement and HP (p < 0.01). Thus, we suggest that NP's metabolic turnover and cellular responses are regulated by the configuration of intracellular actin and fibrillar ECMs under HP.

Anti-Stress and Anti-ROS Effects of MnOx-Functionalized Thermosensitive Nanohydrogel Protect BMSCs for Intervertebral Disc Degeneration Repair.

Stem cell transplantation is proven to be a promising strategy for intervertebral disc degeneration (IDD) repair. However, replicative senescence of bone marrow-derived mesenchymal stem cells (BMSCs), shear damage during direct injection, mechanical stress, and the reactive oxygen species (ROS)-rich microenvironment in degenerative intervertebral discs (IVDs) cause significant cellular damage and limit the therapeutic efficacy. Here, an injectable manganese oxide (MnOx)-functionalized thermosensitive nanohydrogel is proposed for BMSC transplantation for IDD therapy. The MnOx-functionalized thermosensitive nanohydrogel not only successfully protects BMSCs from shear force and mechanical stress before and after injection, but also repairs the harsh high-ROS environment in degenerative IVDs, thus effectively increasing the viability of BMSCs and resident nucleus pulposus cells (NPCs). The MnOx-functionalized thermosensitive nanohydrogel provides mechanical protection for stem cells and helps to remove endogenous ROS, providing a promising stem cell delivery platform for the treatment of IDD.

A2AR regulate inflammation through PKA/NF-κB signaling pathways in intervertebral disc degeneration

BackgroundReduction of inflammatory damage and inhibition of nucleus pulposus (NP) apoptosis are considered to be the main effective therapy idea to reverse the intervertebral disc degeneration (IDD) and alleviate the chronic low back pain. The adenosine A2A receptor (A2AR), as a member of G protein-coupled receptor families, plays an important role in the anti-inflammation and relieving pain. So far, the impact of A2AR on IDD therapy is unclear. The aim of this study was to explore the role of Adenosine A2A receptor (A2AR) in the intervertebral disc degeneration (IDD) and clarify potential mechanism.Materials and methodsIL-1β and acupuncture was used to establish IDD model rats. A2AR agonist CGS-21680 and A2AR antagonist SCH442416 were used to investigate the therapeutical effects for IDD. Histological examination, western blotting analysis and RT-PCR were employed to evaluate the the association between A2AR and cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) pathway.ResultsA2AR activity of the intervertebral disc tissues was up-regulated in feedback way, and cAMP, PKA and CREB expression were also increased. But in general, IL-1β-induced IDD promoted the significant up-regulation the expression of inflammatory factors. The nucleus pulposus (NP) inflammation was exacerbated in result of MMP3 and Col-II decline through activating NF-κB signaling pathway. A2AR agonist CGS-21680 exhibited a disc protective effect through significantly increasing A2AR activity, then further activated cAMP/PKA signaling pathway with attenuating the release of TNF-α and IL-6 via down-regulating NF-κB. In contrast, SCH442416 inhibited A2AR activation, consistent with lower expression levels of cAMP and PKA, further leading to the acceleration of IDD.ConclusionsThe activation of A2AR can prevent inflammatory responses and mitigates degradation of IDD thus suggest a potential novel therapeutic strategy of IDD.

A Chitosan Scaffold Supports the Enhanced and Prolonged Differentiation of HiPSCs into Nucleus Pulposus-like Cells.

Intervertebral disc degeneration (IDD) is a progressive condition and stands as one of the primary causes of low back pain. Cell therapy that uses nucleus pulposus (NP)-like cells derived from human induced pluripotent stem cells (hiPSCs) holds great promise as a treatment for IDD. However, the conventional two-dimensional (2D) monolayer cultures oversimplify cell-cell interactions, leading to suboptimal differentiation efficiency and potential loss of phenotype. While three-dimensional (3D) culture systems like Matrigel improve hiPSC differentiation efficiency, they are limited by animal-derived materials for translation, poorly defined composition, short-term degradation, and high cost. In this study, we introduce a new 3D scaffold fabricated using medical-grade chitosan with a high degree of deacetylation. The scaffold features a highly interconnected porous structure, near-neutral surface charge, and exceptional degradation stability, benefiting iPSC adhesion and proliferation. This scaffold remarkably enhances the differentiation efficiency and allows uninterrupted differentiation for up to 25 days without subculturing. Notably, cells differentiated on the chitosan scaffold exhibited increased cell survival rates and upregulated gene expression associated with extracellular matrix secretion under a chemically defined condition mimicking the challenging microenvironment of intervertebral discs. These characteristics qualify the chitosan scaffold-cell construct for direct implantation, serving as both a structural support and a cellular source for enhanced stem cell therapy for IDD.

PHLDA2 overexpression facilitates senescence and apoptosis via the mitochondrial route in human nucleus pulposus cells by regulating Wnt/β-catenin signalling pathway.

Low back pain is a common clinical symptom of intervertebral disc degeneration (IVDD), which seriously affects the quality of life of the patients. The abnormal apoptosis and senescence of nucleus pulposus cells (NPCs) play important roles in the pathogenesis of IVDD. PHLDA2 is an imprinted gene related to cell apoptosis and tumour progression. However, its role in NPC degeneration is not yet clear. Therefore, this study was set to explore the effects of PHLDA2 on NPC senescence and apoptosis and the underlying mechanisms. The expression of PHLDA2 was examined in human nucleus pulposus (NP) tissues and NPCs. Immunohistochemical staining, magnetic resonance imaging imaging and western blot were performed to evaluate the phenotypes of intervertebral discs. Senescence and apoptosis of NPCs were assessed by SA-β-galactosidase, flow cytometry and western blot. Mitochondrial function was investigated by JC-1 staining and transmission electron microscopy. It was found that the expression level of PHLDA2 was abnormally elevated in degenerated human NP tissues and NPCs. Furthermore, knockdown of PHLDA2 can significantly inhibit senescence and apoptosis of NPCs, whereas overexpression of PHLDA2 can reverse senescence and apoptosis of NPCs in vitro. In vivo experiment further confirmed that PHLDA2 knockdown could alleviate IVDD in rats. Knockdown of PHLDA2 could also reverse senescence and apoptosis in IL-1β-treated NPCs. JC-1 staining indicated PHLDA2's knockdown impaired disruption of the mitochondrial membrane potential and also ameliorated superstructural destruction of NPCs as showed by transmission electron microscopy. Finally, we found the PHLDA2 knockdown promoted Collagen-II expression and suppressed MMP3 expression in NPCs by repressing wnt/β-catenin pathway. In conclusion, the results of the present study showed that PHLDA2 promotes IL-1β-induced apoptosis and senescence of NP cells via mitochondrial route by activating the Wnt/β-catenin pathway, and suggested that therapy targeting PHLDA2 may provide valuable insights into possible IVDD therapies.

Circular RNA KIAA0564 Serves as a Competitive Endogenous RNA for MicroRNA-424-5p, Mediating the Expression of Lysine Demethylase 4a, Thereby Facilitating Intervertebral Disc Degeneration.

A growing body of research has confirmed the involvement of circular RNAs (circRNAs) in the regulation of intervertebral disc degeneration (IDD) progression. However, the underlying molecular networks remain largely elusive. This study aimed to explore whether a novel circRNA, named circKIAA0564, affects nucleus pulposus (NP) cell injury and to elucidate its molecular mechanism. Both in vivo and in vitro IDD models were established, and the expression patterns of circKIAA0564/miR-424-5p/lysine demethylase 4a (KDM4A) were evaluated through quantitative reverse transcription PCR and Western blot analysis. Actinomycin D, RNase R, and Northern blotting were utilized to assess the circular structure of circKIAA0564. The Cell Counting Kit-8, flow cytometry, enzyme-linked immunosorbent assay, commercial assay kits, Western blotting, and reactive oxygen species (ROS) probes were employed to assess the inflammatory and oxidative stress status in NP cells and tissues. Hematoxylin and eosin and TUNEL staining were used to evaluate pathological damage in mouse NP tissues. RNA immunoprecipitation and dual-luciferase reporter assays were conducted to assess the direct targeting relationships among circKIAA0564, miR-424-5p, and KDM4A. CircKIAA0564 was found to be abnormally overexpressed in IDD, functioning as a novel circRNA. Knockdown of circKIAA0564 ameliorated interleukin-1 beta (IL-1β)-induced inflammation and oxidative stress in NP cells. The therapeutic effect of circKIAA0564 knockdown on NP cells was reversed by the silencing of miR-424-5p. Overexpression of circKIAA0564 exacerbated IL-1β-induced NP cell injury, a process that was reversed by knockdown of KDM4A. CircKIAA0564 activated the toll-like receptor 4 (TLR4)/nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB)/NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) signaling pathway by regulating the miR-424-5p/KDM4A axis. CircKIAA0564 exacerbates IL-1β-induced inflammation and oxidative stress in NP cells by competitively binding miR-424-5p, thereby mediating KDM4A and activating the TLR4/NF-κB/NLRP3 signaling pathway. These findings provide robust data support for targeted therapy of IDD and the development of future pharmaceuticals.

Injectable Hydrogel Based on Enzymatic Initiation of Keratin Methacrylate for Controlled Exosome Release in Intervertebral Disc Degeneration Therapy

AbstractThe treatment of intervertebral disc degeneration (IVDD) using bone marrow mesenchymal stem cell‐derived exosomes has shown success in alleviating inflammation and restoring the extracellular matrix (ECM), however, challenges persist due to the deficiency in mechanical support and controlled release. Herein, a carbon‐carbon double bond modified keratin (KeMA) is synthesized by 2‐isocyanatoethyl modification for exosomes wrapping. This injectable KeMA hydrogel, initiated by a biocompatible glucose/ glucose oxidase/ horse radish peroxidase enzymatic cascade reaction with acetylacetone and N‐vinylpyrrolidone, displayed rapid gelation, resembling nucleus pulposus (NP) elasticity, and excellent cytocompatibility. In vitro studies showcased that the exosomes‐loaded KeMA hydrogel (Exo@KeMA) enhanced exosome release kinetics, suppressed inflammation, fostered extracellular matrix (ECM) regeneration, and reinstated NP biomechanics. RNA‐seq analysis indicated Exo@KeMA's effects involved PI3K‐Akt signaling for matrix regeneration and NF‐κB signaling inhibition for anti‐inflammation. In vivo IVDD rat models demonstrated Exo@KeMA attenuated inflammation, maintained NP water content, preserved disc height, and promoted structural regeneration. This research introduces an injectable KeMA hydrogel as a promising therapy for IVDD, by facilitating biomechanics restoration, anti‐inflammatory response, and ECM regeneration.

Identification and validation of ferroptosis-related lncRNA signature in intervertebral disc degeneration

Low back pain influences people of every age and is one of the major contributors to the global cost of illness. Intervertebral disc degeneration (IVDD) is a major contributor to low back pain, but its pathogenesis is unknown. Recently, ferroptosis has been shown to have a substantial role in modulating IVDD progression. However, the function of ferroptosis-related long non-coding RNAs (lncRNAs) has rarely been reported in IVDD. Consequently, the research was conducted to explore the ferroptosis-related lncRNA signature in the IVDD occurrence and development. We analyzed two datasets (GSE167199 and GSE167931) archived in the NCBI Gene Expression Omnibus (GEO) public database. We screened differentially expressed genes (DEGs) and differentially expressed lncRNAs (DELncs) in these datasets using the limma package. Ferroptosis-related genes (FRGs) were derived from the FerrDb V2 website and the intersection of DEGs and FRGs was considered as differentially expressed ferroptosis-related genes (DFGs). These genes were then subjected to Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analysis. Correlations between DFGs and DELncs were shown by Pearson test to determine differential expression of ferroptosis-related lncRNAs. The Pearson test showed that CPEB1-HTR2A-AS1 and ACSL3-DNAJC27-AS1 pairs had correlation coefficients over 0.9. Twenty ferroptosis-related lncRNAs were identified and validated in IVDD. Eight of these lncRNAs were upregulated in IVDD nucleus pulposus cells, including HTR2A-AS1, MIF-AS1, SLC8A1-AS1, LINC00942, DUXAP8, LINC00161, LUCAT1 and LINC01615. Twelve were downregulated in IVDD nucleus pulposus cells, including DNAJC27-AS1, H19, LINC01588, LINC02015, FLNC1, CARMN, PRKG1-AS1, APCDD1L-DT, LINC00839, LINC00536, LINC00710 and LINC01535. Eighteen of the 20 lncRNAs (excluding H19 and LUCAT1) were identified as ferroptosis-related lncRNAs for the first time and verified in IVDD. We have identified a ferroptosis-related lncRNA signature involved in IVDD and revealed a close relationship between CPEB1 and HTR2A-AS1, and between ACSL3 and DNAJC27-AS1. Our findings indicate that ferroptosis-related lncRNAs are a new target set for the early detection and therapy of IVDD.

EXTRACELLULAR VESICLES FROM TIE2-OVEREXPRESSING NUCLEUS PULPOSUS PROGENITORS FOR INTERVERTEBRAL DISC REGENERATION: AN IN VITRO STUDY

Despite promising results in attempting intervertebral disc regeneration, intradiscal cell transplantation is affected by several drawbacks, including poor viability in the harsh disc environment, low cost-effectiveness, and immunogenic/tumorigenic concerns. Recently, the development of cell-free approaches is gaining increasing interest in the field, with a particular regard towards extracellular vesicles (EVs). Nucleus pulposus cell (NPC) progenitors characterized by Tie2 expression have shown a higher chondrogenic differentiation potential compared to MSCs. The aim of this study was to investigate the putative regenerative effects of EVs isolated from Tie2-overexpressing NPC progenitors on degenerative NPCs.NPCs were isolated from young donors and underwent an optimized culture protocol to maximize Tie2 expression (NPCsTie2+) or a standard protocol (NPCsSTD). Following EV characterization, NPC isolated from patients affected by intervertebral disc degeneration (IDD) were treated with either NPCsTie2+-EVs or NPCsSTD-EVs. Cell proliferation and viability were assessed with the CCK-8 assay. Cell apoptosis and necrosis were evaluated with the Annexin V/PI assay. Cell senescence was investigated with b-galactosidase staining. EV uptake was assessed with PKH26 staining of EVs under confocal microscopy.Treatment with EVs isolated from young NPC donors significantly increased degenerative NPC viability, especially in samples treated with NPCsTie2+-EVs. Likewise, NPCsTie2+-EVs significantly reduced cell senescence and did not show to exert necrotic nor apoptotic effects on recipient cells. Furthermore, EV uptake was successfully observed in all treated cells.NPCsTie2+-EVs demonstrated to significantly enhance degenerative NPC viability, senescence and apoptosis. The use of committed progenitors naturally residing the in the nucleus pulposus may optimize EV regenerative properties and constitute the basis for a new therapy for IDD.

Integrated metagenomic and metabonomic mechanisms for the therapeutic effects of Duhuo Jisheng decoction on intervertebral disc degeneration.

Intervertebral disc degeneration (IVDD) is a prevalent orthopedic condition with lower back pain as the predominant clinical presentation that challenges clinical treatment with few therapeutic options. Duhuo Jisheng Decoction (DHJSD) has been proven effective in the therapy of IVDD, but the precise underlying mechanisms remain not fully elucidated. The current study was designed to test our hypothesis that DHJSD may systematically correct the phenotypic disruption of the gut microbiota and changes in the serum metabolome linked to IVDD. Analysis of the active ingredients of DHJSD by ultra high performance liquid chromatography. An integrated metagenomic and metabonomic approach was used to analyze feces and blood samples from normal and IVDD rats. Compared to the control group, fiber ring pinning on the caudal 3 to caudal 5 segments of the rats caused IVDD and significantly altered the compositions of the intestinal microbiota and serum metabolites. Integrated analysis revealed commonly-altered metabolic pathways shared by both intestinal microbiota and serum metabolome of the IVDD rats. DHJSD inhibited the degenerative process and restored the compositions of the perturbed gut microbiota, particularly the relative abundance of commensal microbes of the Prevotellaceae family. DHJSD also corrected the altered metabolic pathways involved in the metabolism of glycine, serine, threonine, valine, the citric acid cycle, and biosynthesis of leucine and isoleucine. DHJSD inhibited the disc degeneration process by an integrated metagenomic and metabonomic mechanism to restore the microbiome profile and normalize the metabonomic pathways.

Melatonin alleviates oxidative stress-induced injury to nucleus pulposus-derived mesenchymal stem cells through activating PI3K/Akt pathway

BackgroundThe changes in the microenvironment of degenerative intervertebral discs cause oxidative stress injury and excessive apoptosis of intervertebral disc endogenous stem cells. The purpose of this study was to explore the possible mechanism of the protective effect of melatonin on oxidative stress injury in NPMSCs induced by H2O2. MethodsThe Cell Counting Kit-8 assay was used to evaluate the cytotoxicity of hydrogen peroxide and the protective effects of melatonin. ROS content was detected by 2′7′-dichlorofluorescin diacetate (DCFH-DA). Mitochondrial membrane potential (MMP) was detected by the JC-1assay. Transferase mediated d-UTP Nick end labeling (TUNEL) and Annexin V/PI double staining were used to determine the apoptosis rate. Additionally, apoptosis-associated proteins and PI3K/Akt signaling pathway-related proteins were evaluated by immunofluorescence, immunoblotting and PCR. ECMs were evaluated by RT‒PCR and immunofluorescence. In vivo, X-ray, Magnetic resonance imaging (MRI) and Histological analyses were used to evaluate the protective effect of melatonin. ResultsMelatonin had an obvious protective effect on NPMSCs treated with 0–10 μM melatonin for 24 h. In addition, melatonin also had obvious protective effects on mitochondrial dysfunction, decreased membrane potential and cell senescence induced by H2O2. More importantly, melatonin could significantly reduce the apoptosis of nucleus pulposus mesenchymal stem cells induced by H2O2 by regulating the expression of apoptosis-related proteins and decreasing the rate of apoptosis. After treatment with melatonin, the PI3K/Akt pathway was significantly activated in nucleus pulposus mesenchymal stem cells, while the protective effect was significantly weakened after PI3K-IN-1 treatment. In vivo, the results of X-ray, MRI and histological analyses showed that therapy with melatonin could partially reduce the degree of intervertebral disc degeneration. ConclusionOur research demonstrated that melatonin can effectively alleviate the excessive apoptosis and mitochondrial dysfunction of nucleus pulposus mesenchymal stem cells induced by oxidative stress via the PI3K/Akt pathway, which provides a novel idea for the therapy of intervertebral disc degeneration. The translational potential of this articleThis study indicates that melatonin can effectively alleviate the excessive apoptosis and mitochondrial dysfunction of NPMSCs through activating the PI3K/Akt pathway. Melatonin might serve as a promising candidate for the prevention and treatment of Intervertebral disc degeneration disease (IVDD) in the future.

Activation of the Nrf-2 pathway by pinocembrin safeguards vertebral endplate chondrocytes against apoptosis and degeneration caused by oxidative stress

AimThe occurrence and progression of intervertebral disc degeneration (IDD) are significantly influenced by the cartilaginous endplate (CEP). Pinocembrin (PIN), a type of flavonoid present in propolis and botanicals, demonstrates both antioxidant and anti-inflammatory characteristics, which could potentially be utilized in management. Therefore, it is crucial to investigate how PIN protects against CEP degeneration and its mechanisms, offering valuable insights for IDD therapy. Materials and methodsTo investigate the protective impact of PIN in vivo, we created the IDD mouse model through bilateral facet joint transection. In vitro, an IDD pathological environment was mimicked by applying TBHP to treat endplate chondrocytes. Key findingsIn vivo, compared with the IDD group, the mouse in the PIN group effectively mitigates IDD progression and CEP calcification. In vitro, the activation of the Nrf-2 pathway improves the process of Parkin-mediated autophagy in mitochondria and decreases ferroptosis in chondrocytes. This enhancement promotes cell survival by addressing the imbalance of redox during pathological conditions related to IDD. Knocking down Nrf-2 with siRNA fails to provide protection to endplate chondrocytes against apoptosis and degeneration. SignificanceThe Nrf-2-mediated activation of mitochondrial autophagy and suppression of ferroptosis play a crucial role in safeguarding against oxidative stress-induced degeneration and calcification of CEP through the protective function of PIN. To sum up, this research offers detailed explanations about how PIN can protect against apoptosis and calcification in CEP, providing valuable information about the development of IDD and suggesting possible treatment approaches.

Wharton's Jelly mesenchymal stromal cell-derived extracellular vesicles promote nucleus pulposus cell anabolism in an in vitro 3D alginate-bead culture model.

Intradiscal transplantation of mesenchymal stromal cells (MSCs) has emerged as a promising therapy for intervertebral disc degeneration (IDD). However, the hostile microenvironment of the intervertebral disc (IVD) may compromise the survival of implanted cells. Interestingly, studies reported that paracrine factors, such as extracellular vesicles (EVs) released by MSCs, may regenerate the IVD. The aim of this study was to investigate the therapeutic effects of Wharton's Jelly MSC (WJ-MSC)-derived EVs on human nucleus pulposus cells (hNPCs) using an in vitro 3D alginate-bead culture model. After EV isolation and characterization, hNPCs isolated from surgical specimens were encapsulated in alginate beads and treated with 10, 50, and 100 μg/mL WJ-MSC-EVs. Cell proliferation and viability were assessed by flow cytometry and live/dead staining. Nitrite and glycosaminoglycan (GAG) content was evaluated through Griess and 1,9-dimethylmethylene blue assays. hNPCs in alginate beads were paraffin-embedded and stained for histological analysis (hematoxylin-eosin and Alcian blue) to assess extracellular matrix (ECM) composition. Gene expression levels of catabolic (MMP1, MMP13, ADAMTS5, IL6, NOS2), anabolic (ACAN), and hNPC marker (SOX9, KRT19) genes were analyzed through qPCR. Collagen type I and type II content was assessed with Western blot analysis. Treatment with WJ-MSC-EVs resulted in an increase in cell content and a decrease in cell death in degenerated hNPCs. Nitrite production was drastically reduced by EV treatment compared to the control. Furthermore, proteoglycan content was enhanced and confirmed by Alcian blue histological staining. EV stimulation attenuated ECM degradation and inflammation by suppressing catabolic and inflammatory gene expression levels. Additionally, NPC phenotypic marker genes were also maintained by the EV treatment. WJ-MSC-derived EVs ameliorated hNPC growth and viability, and attenuated ECM degradation and oxidative stress, offering new opportunities for IVD regeneration as an attractive alternative strategy to cell therapy, which may be jeopardized by the harsh microenvironment of the IVD.

Signaling Mechanisms of Stem Cell Therapy for Intervertebral Disc Degeneration.

Low back pain is the leading cause of disability worldwide. Intervertebral disc degeneration (IDD) is the primary clinical risk factor for low back pain and the pathological cause of disc herniation, spinal stenosis, and spinal deformity. A possible approach to improve the clinical practice of IDD-related diseases is to incorporate biomarkers in diagnosis, therapeutic intervention, and prognosis prediction. IDD pathology is still unclear. Regarding molecular mechanisms, cellular signaling pathways constitute a complex network of signaling pathways that coordinate cell survival, proliferation, differentiation, and metabolism. Recently, stem cells have shown great potential in clinical applications for IDD. In this review, the roles of multiple signaling pathways and related stem cell treatment in IDD are summarized and described. This review seeks to investigate the mechanisms and potential therapeutic effects of stem cells in IDD and identify new therapeutic treatments for IDD-related disorders.

A Review: Methodologies to Promote the Differentiation of Mesenchymal Stem Cells for the Regeneration of Intervertebral Disc Cells Following Intervertebral Disc Degeneration.

Intervertebral disc (IVD) degeneration (IDD), a highly prevalent pathological condition worldwide, is widely associated with back pain. Treatments available compensate for the impaired function of the degenerated IVD but typically have incomplete resolutions because of their adverse complications. Therefore, fundamental regenerative treatments need exploration. Mesenchymal stem cell (MSC) therapy has been recognized as a mainstream research objective by the World Health Organization and was consequently studied by various research groups. Implanted MSCs exert anti-inflammatory, anti-apoptotic, and anti-pyroptotic effects and promote extracellular component production, as well as differentiation into IVD cells themselves. Hence, the ultimate goal of MSC therapy is to recover IVD cells and consequently regenerate the extracellular matrix of degenerated IVDs. Notably, in addition to MSC implantation, healthy nucleus pulposus (NP) cells (NPCs) have been implanted to regenerate NP, which is currently undergoing clinical trials. NPC-derived exosomes have been investigated for their ability to differentiate MSCs from NPC-like phenotypes. A stable and economical source of IVD cells may include allogeneic MSCs from the cell bank for differentiation into IVD cells. Therefore, multiple alternative therapeutic options should be considered if a refined protocol for the differentiation of MSCs into IVD cells is established. In this study, we comprehensively reviewed the molecules, scaffolds, and environmental factors that facilitate the differentiation of MSCs into IVD cells for regenerative therapies for IDD.

Regulatory Effect of Inflammatory Mediators in Intervertebral Disc Degeneration.

Intervertebral disc degeneration (IDD) is a major contributor to back, neck, and radicular pain. It is related to changes in tissue structure and function, including the breakdown of the extracellular matrix (ECM), aging, apoptosis of the nucleus pulposus, and biomechanical tissue impairment. Recently, an increasing number of studies have demonstrated that inflammatory mediators play a crucial role in IDD, and they are being explored as potential treatment targets for IDD and associated disorders. For example, interleukins (IL), tumour necrosis factor-α (TNF-α), chemokines, and inflammasomes have all been linked to the pathophysiology of IDD. These inflammatory mediators are found in high concentrations in intervertebral disc (IVD) tissues and cells and are associated with the severity of LBP and IDD. It is feasible to reduce the production of these proinflammatory mediators and develop a novel therapy for IDD, which will be a hotspot of future research. In this review, the effects of inflammatory mediators in IDD were described.

Tissue-Engineered Injectable Gelatin-Methacryloyl Hydrogel-Based Adjunctive Therapy for Intervertebral Disc Degeneration.

Gelatin-methacryloyl (GelMA) hydrogels are photosensitive with good biocompatibility and adjustable mechanical properties. The GelMA hydrogel composite system is a prospective therapeutic material based on a tissue engineering platform for treating intervertebral disc (IVD) degeneration (IVDD). The potential application value of the GelMA hydrogel composite system in the treatment of IVDD mainly includes three aspects: first, optimization of the current clinical treatment methods, including conservative treatment and surgical treatment; second, regeneration of IVD cells to reverse or repair IVDD; and finally, IVDD instead of injury plays a biomechanical role. In this paper, we summarized and analyzed the preparation of GelMA hydrogels and their excellent biological characteristics as carriers and comprehensively demonstrated the research status and prospects of GelMA hydrogel composite systems in IVDD treatment. In addition, the challenges facing the application of GelMA hydrogel composite systems and the progress of research on new hydrogels modified by GelMA hydrogels are presented. Hopefully, this study will provide theoretical guidance for the future application of GelMA hydrogel composite systems in IVDD.

Mesenchymal stem cell-derived secretome enhances nucleus pulposus cell metabolism and modulates extracellular matrix gene expression in vitro.

Introduction: Intradiscal mesenchymal stromal cell (MSC) therapies for intervertebral disc degeneration (IDD) have been gaining increasing interest due to their capacity to ameliorate intervertebral disc metabolism and relieve low back pain (LBP). Recently, novel investigations have demonstrated that most of MSC anabolic effects are exerted by secreted growth factors, cytokines, and extracellular vesicles, collectively defined as their secretome. In this study, we aimed to evaluate the effect of bone-marrow-MSCs (BM-MSCs) and adipose-derived stromal cells (ADSCs) secretomes on human nucleus pulposus cells (hNPCs) in vitro. Methods: BM-MSCs and ADSCs were characterized according to surface marker expression by flow cytometry and multilineage differentiation by Alizarin red, Red Oil O and Alcian blue staining. After isolation, hNPCs were treated with either BM-MSC secretome, ADSC secretome, interleukin (IL)-1β followed by BM-MSC secretome or IL-1β followed by ADSC secretome. Cell metabolic activity (MTT assay), cell viability (LIVE/DEAD assay), cell content, glycosaminoglycan production (1,9-dimethylmethylene blue assay), extracellular matrix and catabolic marker gene expression (qPCR) were assessed. Results: 20% BM-MSC and ADSC secretomes (diluted to normal media) showed to exert the highest effect towards cell metabolism and were then used in further experiments. Both BM-MSC and ADSC secretomes improved hNPC viability, increased cell content and enhanced glycosaminoglycan production in basal conditions as well as after IL-1β pretreatment. BM-MSC secretome significantly increased ACAN and SOX9 gene expression, while reducing the levels of IL6, MMP13 and ADAMTS5 both in basal conditions and after in vitro inflammation with IL-1β. Interestingly, under IL-1β stimulation, ADSC secretome showed a catabolic effect with decreased extracellular matrix markers and increased levels of pro-inflammatory mediators. Discussion: Collectively, our results provide new insights on the biological effect of MSC-derived secretomes on hNPCs, with intriguing implications on the development of cell-free approaches to treat IDD.

Research trends and hotspots of mesenchymal stromal cells in intervertebral disc degeneration: a scientometric analysis.

Mesenchymal stromal cells (MSCs) are important potential candidates for regenerative therapy for intervertebral disc degeneration (IDD). This scientometric study aimed to summarize the main research trends, identify current research hotspots, and measure the networks of the contributors and their scientific productivity. A total of 1102 publications regarding MSC in IDD were recognized from January 2000 to April 2022. The number of records every year followed an overall uptrend with fluctuations. The main trend of research demonstrated the practice of gradually applying MSC-based therapy to IDD with the assistance of advances in biomaterials and IDD pathology. A recent focus on MSC-derived exosomes and notochordal cells was detected. The basic studies in this field were mainly contributed to by Japan, the USA, and European countries, while China dominated in the number of recent publications. Tokai University with Daisuke Sakai was the most productive contributor. Cell biology, tissue engineering, and biomaterials were the categories with deep engagement in research of this field.

PH-Responsive Delivery of H2 through Ammonia Borane-Loaded Hollow Polydopamine for Intervertebral Disc Degeneration Therapy.

An imbalance in oxidative and inflammatory regulation is the main contributor to intervertebral disc degeneration (IDD). Hydrogen (H2) therapy is a promising antioxidation and anti-inflammatory approach. However, the key to the treatment is how to maintain the long-term effective H2 concentration in the intervertebral disc (IVD). Therefore, we developed a pH-responsive delivery of H2 through ammonia borane-loaded hollow polydopamine (AB@HPDA) for IDD therapy, which has sufficient capacity to control long-term H2 release in an acid-dependent manner in degenerative IVD. The characterization, toxicity, and pH-responsive H2 release of AB@HPDA was detected in vitro. The metabolization of AB@HPDA in the degenerated IVD was tested by in vivo imaging. The therapeutic effect of AB@HPDA on IDD was tested in vivo by X-ray, MRI, water content of the disc, and histological changes. Nuclear extracellular matrix (ECM) components, oxidative stress, and inflammation were also tested to explore potential therapeutic mechanisms. AB@HPDA has good biocompatibility at concentrations less than 500 μg/mL. The H2 release of AB@HPDA was pH responsive. Therefore, AB@HPDAs can provide efficient hydrogen therapy with controlled H2 release in response to the acidic degenerated IVD microenvironment. The metabolization of AB@HPDA in IVD was slow and lasted up to 11 days. HPDA and AB@HPDA significantly inhibited IDD, as tested by X-ray, MRI, disc water content, and histology (P < 0.05). pH-responsive H2 delivery through AB@HPDAs has the potential to efficiently treat IDD by inhibiting ECM degradation and rebalancing oxidative stress and inflammation in degenerative IVDs.