• CD24
• GD2
• cell sub‐populations
• flow cytometry
• intervertebral disc
• notochordal
• nucleus pulposus

• Biotechnology and Biological Sciences Research Council
• Medical Research Council
• Versus Arthritis

• Humans
• Intervertebral Disc Degeneration/therapy
• Regenerative Medicine/methods
• Genetic Therapy/methods
• Intervertebral Disc/pathology
• Animals
• Cell- and Tissue-Based Therapy/methods
• Drug Delivery Systems

• Tie2
• nucleus pulposus
• spatial transcriptomics (ST)
• stem/progenitor cell
• tervertebral disc degeneration

• Animals
• Mice
• Nucleus Pulposus/metabolism
• Nucleus Pulposus/cytology
• Stem Cells/metabolism
• Transcriptome/genetics
• Cell Differentiation/genetics
• Intervertebral Disc Degeneration/genetics
• Intervertebral Disc Degeneration/metabolism
• Gene Expression Profiling/methods
• Disease Models, Animal

• 82002262 National Natural Science Foundation of China
• 92068104 National Natural Science Foundation of China
• 2020YFA0112900 National Key Research and Development Program of China
• 2022J06003 Fujian Natural Science Fund for Distinguished Young Scholars
• 2020J05008 Natural Science Foundation of Fujian Province
• 3502Z20214001 Project of Xiamen Cell Therapy Research center
• National Natural Science Foundation of China
• National Key Research and Development Program of China
• Natural Science Foundation of Fujian Province

• Disc degeneration
• Exosomes
• Extracellular vesicles
• In vivo
• Intervertebral disc
• Tie2

• Animals
• Intervertebral Disc Degeneration/therapy
• Extracellular Vesicles/transplantation
• Extracellular Vesicles/metabolism
• Mesenchymal Stem Cells/physiology
• Nucleus Pulposus/metabolism
• Rats, Sprague-Dawley
• Rats
• Humans
• Male
• Cells, Cultured
• Pain

• 22-199 ON Foundation
• "Patrizio Parisini" prize SICV/GIS

• FOXO1
• NSC117079
• NSC45586
• PHLPP
• intervertebral disc degeneration
• nucleus pulposus
• small molecule PHLPP inhibitor

• R01 AR078908 NIAMS NIH HHS
• R21 AR072222 NIAMS NIH HHS
• National Institute of Arthritis and Musculoskeletal and Skin Diseases

Intervertebral disc degeneration (IDD) is a natural progression of age-related processes. Associated with IDD, degenerative disc disease (DDD) is a pathologic condition implicated as a major cause of chronic lower back pain, which can have a severe impact on the quality of life of patients. As degeneration progression is associated with elevated levels of inflammatory cytokines, enhanced aggrecan and collagen degradation, and changes in the disc cell phenotype. The purpose of this study was to investigate the biological and cytological characteristics of rabbit nucleus pulposus mesenchymal stem cells (NPMSCs)—a key factor in IDD—and to determine the effect of the growth and differentiation factor-5 (GDF5) on the differentiation of rabbit NPMSCs transduced with a lentivirus vector.

An in vitro culture model of rabbit NPMSCs was established and NPMSCs were identified by flow cytometry (FCM) and quantitative real-time PCR (qRT-PCR). Subsequently, NPMSCs were randomly divided into three groups: a transfection group (the lentiviral vector carrying GDF5 gene used to transfect NPMSCs); a control virus group (the NPMSCs transfected with an ordinary lentiviral vector); and a normal group (the NPMSCs alone). FCM, qRT-PCR, and western blot (WB) were used to detect the changes in NPMSCs.

The GDF5-transfected NPMSCs displayed an elongated shape, with decreased cell density, and significantly increased GDF5 positivity rate in the transfected group compared to the other two groups (P < 0.01). The mRNA levels of Krt8, Krt18, and Krt19 in the transfected group were significantly higher in comparison with the other two groups (P < 0.01), and the WB results were consistent with that of qRT-PCR.

GDF5 could induce the differentiation of NPMSCs. The lentiviral vector carrying the GDF5 gene could be integrated into the chromosome genome of NPMSCs and promoted differentiation of NPMSCs into nucleus pulposus cells. Our findings advance the development of feasible and effective therapies for IDD.

The online version contains supplementary material available at 10.1186/s40001-021-00624-5.

• Growth and differentiation factor-5
• Intervertebral disc degeneration
• Lentivirus
• Nucleus pulposus mesenchymal stem cells
• Transfection

• differentiation
• fetal nucleus pulposus cell
• fetal stem cell
• fetal synovium-derived stem cell
• hypoxia

• R01 AR067747 NIAMS NIH HHS
• U54 GM104942 NIGMS NIH HHS

The treatment of intervertebral disc degeneration (IVDD) is still a huge challenge for clinical updated surgical techniques and basic strategies of intervertebral disc regeneration. Few studies have ever tried to combine surgery and cell therapy to bridge the gap between clinical and basic research. A prospective clinical study with a 72-month follow-up was conducted to assess the safety and feasibility of autologous discogenic cells transplantation combined with discectomy in the treatment of lumbar disc herniation (LDH) and to evaluate the regenerative ability of discogenic cells in IVDD. Forty patients with LDH who were scheduled to have discectomy enrolled in our study and were divided into the observed group (transplantation of autologous discogenic cells after discectomy) and control group (only-discectomy). Serial MRI and X-ray were used to evaluate the degenerative extent of index discs, and clinical scores were used to determine the symptomatic improvement. No adverse events were observed in the observed group, and seven patients in the control group underwent revisions. Both groups had significant improvement of all functional scores post-operatively, with the observed group improving more considerably at 36-month and 72-month follow-up. The height and water content of discs in both groups decreased significantly since 36 months post-op with the control group decreased more obviously. Discectomy combined with autologous discogenic cells transplantation is safe and feasible in the treatment of LDH. Radiological analysis demonstrated that discogenic cells transplantation could slow down the further degeneration of index discs and decrease the complications of discectomy.

• Diskectomy/adverse effects
• Diskectomy/methods
• Feasibility Studies
• Humans
• Intervertebral Disc Degeneration/diagnostic imaging
• Intervertebral Disc Degeneration/surgery
• Intervertebral Disc Displacement/diagnostic imaging
• Intervertebral Disc Displacement/surgery
• Prospective Studies
• Treatment Outcome

• National Natural Foundation of China
• Beijing Municipal Science & Technology Commission

Intervertebral disc (IVD) degeneration is considered to be the primary reason for low back pain (LBP), which has become more prevalent from 21 century, causing an enormous economic burden for society. However, in spite of remarkable improvements in the basic research of IVD degeneration (IVDD), the effects of clinical treatments of IVDD are still leaving much to be desired. Accumulating evidence has proposed the existence of endogenous stem/progenitor cells in the IVD that possess the ability of proliferation and differentiation. However, few studies have reported the biological properties and potential application of IVD progenitor cells in detail. Even so, these stem/progenitor cells have been consumed as a promising cell source for the regeneration of damaged IVD. In this review, we will first introduce IVD, describe its physiology and stem/progenitor cell niche, and characterize IVDSPCs between homeostasis and IVD degeneration. We will then summarize recent studies on endogenous IVDSPC-based IVD regeneration and exogenous cell-based therapy for IVDD. Finally, we will discuss the potential applications and future developments of IVDSPC-based repair of IVD degeneration.

• Chondrogenic differentiation
• Exosomes
• Intervertebral disc degeneration
• Nucleus pulposus-mesenchymal stem cells
• miR-15a

Intervertebral disc (IVD) degeneration and its inflammatory microenvironment ultimately led to discogenic pain, which is thought to originate in the nucleus pulposus (NP). In this study, key genes involved in NP tissue immune infiltration in lumbar disc herniation (LDH) were identified by bioinformatic analysis. Gene expression profiles were downloaded from the Gene Expression Omnibus (GEO) database. The CIBERSORT algorithm was used to analyze the immune infiltration into NP tissue between the LDH and control groups. Hub genes were identified by the WGCNA R package in Bioconductor and single-cell sequencing data was analyzed using R packages. Gene expression levels were evaluated by quantitative real-time polymerase chain reaction. The immune infiltration profiles varied significantly between the LDH and control groups. Compared with control tissue, LDH tissue contained a higher proportion of regulatory T cells and macrophages, which are associated with the macrophage polarization process. The most significant module contained three hub genes and four subclusters of NP cells. Functional analysis of these genes was performed, the hub gene expression pattern was confirmed by PCR, and clinical features of the patients were investigated. Finally, we identified TGF-β and MAPK signaling pathways as crucial in this process and these pathways may provide diagnostic markers for LDH. We hypothesize that the hub genes expressed in the specific NP subclusters, along with the infiltrating macrophages play important roles in the pathogenesis of IVD degeneration and ultimately, disc herniation.

• intervertebral disc degeneration
• lumbar disc herniation
• macrophages
• nucleus pulposus
• single-cell sequencing (SCS)

• microRNA-124-3p
• nucleus pulposus-like cells
• precartilaginous stem cells

Previous work showed a link between Tie2⁺ nucleus pulposus progenitor cells (NPPC) and disc degeneration. However, NPPC remain difficult to maintain in culture. Here, we report whole tissue culture (WTC) combined with fibroblast growth factor 2 (FGF2) and chimeric FGF (cFGF) supplementation to support and enhance NPPC and Tie2 expression. We also examined the role of PI3K/Akt and MEK/ERK pathways in FGF2 and cFGF-induced Tie2 expression. Young herniating nucleus pulposus tissue was used. We compared WTC and standard primary cell culture, with or without 10 ng/mL FGF2. PI3K/Akt and MEK/ERK signaling pathways were examined through western blotting. Using WTC and primary cell culture, Tie2 positivity rates were 7.0 ± 2.6% and 1.9 ± 0.3% (p = 0.004), respectively. Addition of FGF2 in WTC increased Tie2 positivity rates to 14.2 ± 5.4% (p = 0.01). FGF2-stimulated expression of Tie2 was reduced 3-fold with the addition of the MEK inhibitor PD98059 (p = 0.01). However, the addition of 1 μM Akt inhibitor, 124015-1MGCN, only reduced small Tie2 expression (p = 0.42). cFGF similarly increased the Tie2 expression, but did not result in significant phosphorylation in both the MEK/ERK and PI3K/Akt pathways. WTC with FGF2 addition significantly increased Tie2 maintenance of human NPPC. Moreover, FGF2 supports Tie2 expression via MEK/ERK and PI3K/Akt signals. These findings offer promising tools and insights for the development of NPPC-based therapeutics.

• Akt
• ERK
• Tie2 receptor
• basic fibroblast growth factor
• chimera fibroblast growth factor
• intervertebral disc
• nucleus pulposus
• nucleus pulposus progenitor cell
• type II collagen
• whole tissue culture

• Adolescent
• Adult
• Cells, Cultured
• Collagen Type II/biosynthesis
• Collagen Type II/genetics
• Female
• Fibroblast Growth Factor 1/genetics
• Fibroblast Growth Factor 2/genetics
• Fibroblast Growth Factor 2/pharmacology
• Flavonoids/pharmacology
• Humans
• Intervertebral Disc Displacement/pathology
• MAP Kinase Signaling System/drug effects
• Male
• Nucleus Pulposus/cytology
• Nucleus Pulposus/drug effects
• Nucleus Pulposus/metabolism
• Phosphatidylinositol 3-Kinases/physiology
• Proto-Oncogene Proteins c-akt/antagonists & inhibitors
• Proto-Oncogene Proteins c-akt/physiology
• Receptor, TIE-2/biosynthesis
• Receptor, TIE-2/genetics
• Recombinant Fusion Proteins/pharmacology
• Signal Transduction/drug effects
• Stem Cells/drug effects
• Stem Cells/metabolism
• Young Adult

• disc regeneration
• intervertebral disc degeneration
• intradiscal injection
• mesenchymal stem cells
• stem cell

• GATA binding protein 4
• cartilage endplate stem cells
• differentiation
• exosome
• intervertebral disk degeneration
• transforming growth factor-β1

• adipogenesis
• alginate bead
• angiopoietin‐1 receptor
• chondrogenesis
• differentiation
• flow cytometry
• intervertebral disk
• microenvironment
• nucleus pulposus
• osteogenesis
• qPCR
• three‐dimensional culture
• tissue‐specific progenitor cells

Intervertebral disk (IVD) degeneration is one of the most common musculoskeletal disease. Current clinical treatment paradigms for IVD degeneration cannot completely restore the structural and biomechanical functions of the IVD. Bio-therapeutic techniques focused on progenitor/stem cells, especially IVD progenitor cells, provide promising options for the treatment of IVD degeneration. Endogenous repair is an important self-repair mechanism in IVD that can allow the IVD to maintain a long-term homeostasis. The progenitor cells within IVD play a significant role in IVD endogenous repair. Improving the adverse microenvironment in degenerative IVD and promoting progenitor cell migration might be important strategies for implementation of the modulation of endogenous repair of IVD. Here, we not only reviewed the research status of treatment of degenerative IVD based on IVD progenitor cells, but also emphasized the concept of endogenous repair of IVD and discussed the potential new research direction of IVD endogenous repair.

• endogenous repair strategy
• intercellular communication
• intervertebral disk – degeneration
• microenvironment
• progenitor/stem cell

To date, there has been no effective treatment for intervertebral disc degeneration (IDD). Nucleus pulposus-derived mesenchymal stem cells (NPMSCs) showed encouraging results in IDD treatment, but the overexpression of reactive oxygen species (ROS) impaired the endogenous repair abilities of NPMSCs. 6-gingerol (6-GIN) is an antioxidant and anti-inflammatory reagent that might protect NPMSCs from injury.

To investigate the effect of 6-GIN on NPMSCs under oxidative conditions and the potential mechanism.

The cholecystokinin-8 assay was used to evaluate the cytotoxicity of hydrogen peroxide and the protective effects of 6-GIN. ROS levels were measured by 2´7´-dichlorofluorescin diacetate analysis. Matrix metalloproteinase (MMP) was detected by the tetraethylbenzimidazolylcarbocyanine iodide assay. TUNEL assay and Annexin V/PI double-staining were used to determine the apoptosis rate. Additionally, autophagy-related proteins (Beclin-1, LC-3, and p62), apoptosis-associated proteins (Bcl-2, Bax, and caspase-3), and PI3K/Akt signaling pathway-related proteins (PI3K and Akt) were evaluated by Western blot analysis. Autophagosomes were detected by transmission electron microscopy in NPMSCs. LC-3 was also detected by immunofluorescence. The mRNA expression of collagen II and aggrecan was evaluated by real-time polymerase chain reaction (RT-PCR), and the changes in collagen II and MMP-13 expression were verified through an immunofluorescence assay.

6-GIN exhibited protective effects against hydrogen peroxide-induced injury in NPMSCs, decreased hydrogen peroxide-induced intracellular ROS levels, and inhibited cell apoptosis. 6-GIN could increase Bcl-2 expression and decrease Bax and caspase-3 expression. The MMP, Annexin V-FITC/PI flow cytometry and TUNEL assay results further confirmed that 6-GIN treatment significantly inhibited NPMSC apoptosis induced by hydrogen peroxide. 6-GIN treatment promoted extracellular matrix (ECM) expression by reducing the oxidative stress injury-induced increase in MMP-13 expression. 6-GIN activated autophagy by increasing the expression of autophagy-related markers (Beclin-1 and LC-3) and decreasing the expression of p62. Autophagosomes were visualized by transmission electron microscopy. Pretreatment with 3-MA and BAF further confirmed that 6-GIN-mediated stimulation of autophagy did not reduce autophagosome turnover but increased autophagic flux. The PI3K/Akt pathway was also found to be activated by 6-GIN. 6-GIN inhibited NPMSC apoptosis and ECM degeneration, in which autophagy and the PI3K/Akt pathway were involved.

6-GIN efficiently decreases ROS levels, attenuates hydrogen peroxide-induced NPMSCs apoptosis, and protects the ECM from degeneration. 6-GIN is a promising candidate for treating IDD.

• Nucleus pulposus-derived mesenchymal stem cells
• 6-Gingerol
• Intervertebral disc degeneration
• Oxidative stress
• Autophagy
• Apoptosis

• Intervertebral disc degeneration
• isolation and purification; method; cloning cylinder
• mesenchymal stem cells
• nucleus pulposus

• Cell recruitment
• Chemokines
• Disc disease
• Ex vivo model
• Microbeads
• Regeneration

Low back pain has become more prevalent in recent years, causing enormous economic burden for society and government. Common therapies used in clinics including conservative treatment and surgery can only relieve pain. Subsequent cell-based treatment such as mesenchymal stem cell transplantation poses problems such as short duration of therapeutic effect and tumorigenesis. Recently, the discovery and identification of stem cell niche and stem/progenitor cells in intervertebral disc bring increased attention to endogenous repair strategy. Therefore, we review the studies involving endogenous repair strategy and present the characteristics and current status of this treatment. Meanwhile, we also discuss the strategy and perspective of endogenous repair strategy in future.

• Low back pain
• Intervertebral disc degeneration
• Stem cell niche
• Stem/progenitor cell
• Endogenous repair strategy
• Stem cell treatment

Puerarin (PUR), an 8-C-glucoside of daidzein extracted from Pueraria plants, is closely related to autophagy, reduced reactive oxygen species (ROS) production, and anti-inflammatory effects, but its effects on human nucleus pulposus mesenchymal stem cells (NPMSCs) have not yet been identified. In this study, NPMSCs were cultured in a compression apparatus to simulate the microenvironment of the intervertebral disc under controlled pressure (1.0 MPa), and we found that cell viability was decreased and apoptosis level was gradually increased as compression duration was prolonged. After PUR administration, apoptosis level evaluated by flow cytometry and caspase-3 activity was remitted, and protein levels of Bas as well as cleaved caspase-3 were decreased, while elevated Bcl-2 level was identified. Moreover, ATP production detection, ROS, and JC-1 fluorography as well as quantitative analysis suggested that PUR could attenuate intercellular ROS accumulation and mitochondrial dysfunction. Besides, the rat tail compression model was utilized, which indicated that PUR could restore impaired nucleus pulposus degeneration induced by compression. The PI3K/Akt pathway was identified to be deactivated after compression stimulation by western blot, and PUR could rescue the phosphorylation of Akt, thus reactivating the pathway. The effects of PUR, such as antiapoptosis, cell viability restoration, antioxidation, and mitochondrial maintenance, were all counteracted by application of the PI3K/Akt pathway inhibitor (LY294002). Summarily, PUR could alleviate compression-induced apoptosis and cell death of human NPMSCs in vitro as well as on the rat compression model and maintain intracellular homeostasis by stabilizing mitochondrial membrane potential and attenuating ROS accumulation through activating the PI3K/Akt pathway.

• annulus fibrosus
• auto-immune response
• immune privilege
• intervertebral disc
• nucleus pulposus

• organ culture
• msc migration
• msc homing
• disc cell survival
• disc cell proliferation
• ivd regeneration
• tie2
• cd202
• disc progenitor cells
• human mesenchymal stem cells

• 3D co-culture
• ZMPSTE24
• bone marrow-derived mesenchymal stem cells
• nucleus pulposus
• senescence

Low back pain (LBP) in one of the most disabling symptoms affecting nearly 80% of the population worldwide. Its primary cause seems to be intervertebral disc degeneration (IDD): a chronic and progressive process characterized by loss of viable cells and extracellular matrix (ECM) breakdown within the intervertebral disc (IVD) especially in its inner region, the nucleus pulposus (NP). Over the last decades, innovative biological treatments have been investigated in order to restore the original healthy IVD environment and achieve disc regeneration. Mesenchymal stem cells (MSCs) have been widely exploited in regenerative medicine for their capacity to be easily harvested and be able to differentiate along the osteogenic, chondrogenic, and adipogenic lineages and to secrete a wide range of trophic factors that promote tissue homeostasis along with immunomodulation and anti-inflammation. Several in vitro and preclinical studies have demonstrated that MSCs are able to acquire a NP cell-like phenotype and to synthesize structural components of the ECM as well as trophic and anti-inflammatory mediators that may support resident cell activity. However, due to its unique anatomical location and function, the IVD presents distinctive features: avascularity, hypoxia, low glucose concentration, low pH, hyperosmolarity, and mechanical loading. Such conditions establish a hostile microenvironment for both resident and exogenously administered cells, which limited the efficacy of intradiscal cell therapy in diverse investigations. This review is aimed at describing the characteristics of the healthy and degenerated IVD microenvironment and how such features influence both resident cells and MSC viability and biological activity. Furthermore, we focused on how recent research has tried to overcome the obstacles coming from the IVD microenvironment by developing innovative cell therapies and functionalized bioscaffolds.

• Anti-catabolic factors
• Cell supplementation
• Degenerative disc disease
• Drug delivery systems
• Endogenous repair
• Pro-anabolic factors

• Biomaterials, chemokines
• Disc degenerative disease
• Drug delivery systems
• Growth factors
• Low back pain
• Progenitor cells
• Regenerative medicine
• Stem cells
• miRNA

• Animals
• Cell- and Tissue-Based Therapy
• Humans
• Intervertebral Disc Degeneration/metabolism
• Intervertebral Disc Degeneration/therapy
• Mesenchymal Stem Cell Transplantation
• Regeneration

• differentiation
• intervertebral disc
• nuclear factor-κB signaling pathway
• nucleus pulposus stem cell
• tumor necrosis factor-α

• Herniation
• Intervertebral disc
• Low back pain

• Costs and Cost Analysis
• Humans
• Intervertebral Disc/surgery
• Intervertebral Disc Degeneration
• Intervertebral Disc Displacement/surgery
• Low Back Pain/drug therapy
• Lumbar Vertebrae/surgery
• Neck Pain
• Regeneration
• Risk Factors
• Spinal Fusion
• Total Disc Replacement

• development
• stem cell
• tissue‐specific progenitor cells

Cell therapy for the treatment of intervertebral disc degeneration (IDD) faces serious barriers since tissue-specific adult cells such as nucleus pulposus cells (NPCs) have limited proliferative ability and poor regenerative potential; in addition, it is difficult for exogenous adult stem cells to survive the harsh environment of the degenerated intervertebral disc. Endogenous repair by nucleus pulposus mesenchymal stem cells (NPMSCs) has recently shown promising regenerative potential for the treatment of IDD. Notochordal cells (NCs) and NC-conditioned medium (NCCM) have been proven to possess regenerative ability for the treatment of IDD, but this approach is limited by the isolation and passaging of NCs. Our previous study demonstrated that modified notochordal cell-rich nucleus pulposus (NC-rich NP) has potential for the repair of IDD. However, whether this can protect NPMSCs during IDD has not been evaluated.

In the current study, tumor necrosis factor (TNF)-α was used to mimic the inflammatory environment of IDD. Human NPMSCs were cocultured with NC-rich NP explants from healthy rabbit lumbar spine with or without TNF-α. Cell proliferation and senescence were analyzed to investigate the effect of NC-rich NP explants on TNF-α-treated NPMSCs. The expression of mRNA encoding proteins related to matrix macromolecules (such as aggrecan, Sox-9, collagen Iα, and collagen IIα), markers related to the nucleus pulposus cell phenotype (including CA12, FOXF1, PAX1, and HIF-1α), and senescence markers (such as p16, p21, and p53), senescence-associated proinflammatory cytokines (IL-6), and extracellular proteases (MMP-13, ADAMTS-5) was assessed. The protein expression of CA12 and collagen II was also evaluated.

After a 7-day treatment, the NC-rich NP explant was found to enhance cell proliferation, decrease cellular senescence, promote glycosaminoglycan (GAG), collagen II, and CA12 production, upregulate the expression of extracellular matrix (ECM)-related genes (collagen I, collagen II, SOX9, and ACAN), and enhance the expression of nucleus pulposus cell (NPC) markers (HIF-1α, FOXF1, PAX1, and CA12).

Modified NC-rich NP explants can attenuate TNF-α-induced degeneration and senescence of NPMSCs in vitro. Our findings provide new insights into the therapeutic potential of NC-rich NP for the treatment of IDD.

• Intervertebral disc degeneration
• Notochordal cell-rich nucleus pulposus explants
• Nucleus pulposus mesenchymal stem cells
• Senescence
• TNF-α

• biologic therapies
• culture systems
• stem cell
• tissue‐specific progenitor cells