Degenerative disc disease of herniated intervertebral discs is associated with extracellular matrix remodeling, vimentin-positive cells and cell death

The proteomic landscape of extracellular vesicles derived from human intervertebral disc cells

Background

Extracellular vesicles (EVs) function as biomarkers and are crucial in cell communication and regulation, with therapeutic potential for intervertebral disc (IVD)-related low back pain (LBP). EV cargo is often affected by tissue health, which may affect the therapeutic potential. There is currently limited knowledge of how the cargo of IVD cell-derived EVs varies with tissue health and how differences in proteomic profile affect the predicted biological functions.

Methods

Our study purified EVs from human IVD cell conditioned media by size-exclusion chromatography. Nanoparticle tracking analysis was conducted to measure EV size and concentration. Transmission electron microscopy and Western blot were performed to examine EV structure and markers. Tandem mass tag-mass spectrometry was conducted to determine protein cargo.

Results

Most EVs were exosomes and intermediate microvesicles with an increasing amount linked to disease progression. Of the proteins detected, 88.6% were shared across the non-degenerate, mildly-degenerate, and degenerate samples. GO and KEGG analyses revealed that cargo from the mildly-degenerate samples was the most distinct, with the proteins in high abundance strongly associated with extracellular matrix (ECM) organization and structure. Shared proteins, highly expressed in the non-degenerate and degenerate samples, showed strong associations with cell adhesion, ECM-receptor interaction, and vesicle-mediated transport, respectively.

Conclusions

Our findings indicate that EVs from IVD cells from tissue with different degrees of degeneration share a majority of the cargo proteins. However, the level of expression differs with degeneration grade. Cargo from the mildly-degenerate samples exhibits the most differences. A better understanding of changes in EV cargo in the degenerative process may provide novel information related to molecular mechanisms underlying IVD degeneration and suggest new potential treatment modalities for IVD-related LBP.

Bone Mesenchymal Stem Cells Inhibit Oxidative Stress-Induced Pyroptosis in Annulus Fibrosus Cells to Alleviate Intervertebral Disc Degeneration Based on Matric Hydrogels

Intervertebral disc degeneration (IVDD) is the primary cause of low back pain. Stem cell transplantation may be a possible approach to promote IVDD. This study was aimed to investigate the role of bone mesenchymal stem cells (BMSCs) in IVDD and the molecular mechanism. Annulus fibrosus cells (AFCs) were treated with tert-butyl hydroperoxide (TBHP) to induce oxidative stress injury. AFC biological functions were analyzed using a lactate dehydrogenase kit, enzyme-linked immunosorbent assay, flow cytometry, and western blot. The molecular mechanisms of BMSC functions were assessed using quantitative real-time PCR, western blot, immunoprecipitation (IP), co-IP, GST pull-down, and cycloheximide treatment. Furthermore, the impacts of BMSCs in IVDD progression in vivo were evaluated by magnetic resonance imaging (MRI) and H&E analysis. BMSCs inhibited TBHP-induced inflammation and pyroptosis in AFCs. Knockdown of SIRT1 reversed the effects on inflammation and pyroptosis of BMSCs. Moreover, SIRT1 promoted the deacetylation of ASC rather than NLRP3. SIRT1 interacted with ASC to reduce its protein stability, thereby negatively regulating ASC protein levels. In addition, BMSCs alleviated LPS-induced IVDD based on matrix hydrogels. BMSCs inhibited oxidative stress-induced pyroptosis and inflammation in AFCs, thereby alleviating IVDD, suggesting that BMSCs may contribute to treating intervertebral disc generation.

Repair of annulus fibrosus defects using decellularized annulus fibrosus matrix/chitosan hybrid hydrogels

Degenerative disc disease is the leading cause of lower back and leg pain, considerably impacting daily life and incurring substantial medical expenses for those affected. The development of annulus fibrosus tissue engineering offers hope for treating this condition. However, the current annulus fibrosus tissue engineering scaffolds fail to accurately mimic the natural biological environment of the annulus fibrosus, resulting in limited secretion of extracellular matrix produced by the seeded cells and poor biomechanical properties of the constructed biomimetic annulus fibrosus tissue. This inability to match the biomechanical performance of the natural annulus fibrosus hinders the successful treatment of annulus fibrosus defects. In this study, we fabricated decellularized annulus fibrosus matrix (DAFM)/chitosan hydrogel-1 (DAFM: Chitosan 6:2) and DAFM/chitosan hydrogel-2 (DAFM: Chitosan 4:4) by varying the ratio of DAFM to chitosan. Rat annulus fibrosus (AF)-derived stem cells were cultured on these hydrogel scaffolds, and the cell morphology, AF-related gene expression, and Interleukin-6 (IL-6) levels were investigated. Additionally, magnetic resonance imaging, Hematoxylin and eosin staining, and Safranine and Fast Green staining were performed to evaluate the repair effect of the DAFM/chitosan hydrogels in vivo. The gene expression results showed that the expression of Collagen type I (Col-I), Collagen type I (Col-II), and aggrecan by annulus fibrosus stem cells (AFSCs) cultured on the DAFM/chitosan-1 hydrogel was higher compared with the DAFM/chitosan-2 hydrogel. Conversely, the expression of metalloproteinase-9 (MMP-9) and IL-6 was lower on the DAFM/chitosan-1 hydrogel compared with the DAFM/chitosan-2 hydrogel. In vivo, both the DAFM/chitosan-1 and DAFM/chitosan-2 hydrogels could partially repair large defects of the annulus fibrosus in rat tail vertebrae. In conclusion, the DAFM/chitosan-1 hydrogel could be regarded as a candidate scaffold material for the repair of annulus fibrosus defects, offering the potential for improved treatment outcomes.

Single-cell RNA-seq analysis reveals the Wnt/Ca2+ signaling pathway with inflammation, apoptosis in nucleus pulposus degeneration

BACKGROUND

Increasing studies have shown degeneration of nucleus pulposus cells (NPCs) as an critical part of the progression of intervertebral disc degeneration (IVDD). However, there are relatively few studies on single-cell transcriptome contrasts in human degenerated NPCs. Moreover, differences in Wnt/Ca2+ signaling in human degenerated nucleus pulposus cells have not been elucidated. The aim of this study is to investigate the differential expression of Wnt/Ca2+ signaling pathway between normal and degenerated nucleus pulposus cells in humans and try to investigate its mechanism.

METHODS

We performed bioinformatics analysis using our previously published findings to construct single cell expression profiles of normal and degenerated nucleus pulposus. Then, in-depth differential analysis was used to characterize the expression of Wnt/Ca2+ signaling pathway between normal and degenerated nucleus pulposus cells in humans.

RESULTS

The obtained cell data were clustered into five different chondrocytes clusters, which chondrocyte 4 and chondrocyte 5 mainly accounted for a high proportion in degenerated nucleus pulposus tissues, but rarely in normal nucleus pulposus tissues. Genes associated within the Wnt/Ca2+ signaling pathway, such as Wnt5B, FZD1, PLC (PLCB1), CaN (PPP3CA) and NAFATC1 are mainly present in chondrocyte 3, chondrocyte 4 and chondrocyte 5 from degenerated nucleus pulposus tissues. In addition, as a receptor that activates Wnt signaling pathway, LRP5 is mainly highly expressed in chondrocyte 5 of degenerated nucleus pulposus cells. Six genes, ANGPTL4, PTGES, IGFBP3, GDF15, TRIB3 and TNFRSF10B, which are associated with apoptosis and inflammatory responses, and are widespread in chondrocyte 4 and chondrocyte 5, may be closely related to degenerative of nucleus pulposus cells.

CONCLUSIONS

Single-cell RNA sequencing revealed differential expression of Wnt/Ca2+ signaling in human normal and degenerated nucleus pulposus cells, and this differential expression may be closely related to the abundance of chondrocyte 4 and chondrocyte 5 in degenerated nucleus pulposus cells. In degenerated nucleus pulposus cells, LRP5 activate Wnt5B, which promotes nucleus pulposus cell apoptosis and inflammatory response by regulating the Wnt/Ca2+ signaling pathway, thereby promoting disc degeneration. ANGPTL4, IGFBP3, PTGES in chondrocyte 4 and TRIB3, GDF15, TNFRSF10B in chondrocyte 5 may play an important role in this process.

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

Background and aims

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

Methods

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

Results

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

Conclusion

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

PLAGL2 induces nucleus pulposus cell apoptosis via regulating RASSF5 expression and thus accelerates intervertebral disc degeneration

Excessive apoptosis of nucleus pulposus (NP) cells is the main pathological change in intervertebral disc degeneration (IVDD) progression. Pleomorphic adenoma gene like-2 (PLAGL2) plays a key role in cell apoptosis, however, the effect of PLAGL2 on IVDD has not been clarified yet. In this study, we established mouse IVDD models via the annulus fibrosis needle puncture, TUNEL and safranin O staining were used to verify the successful establishment of IVDD models, and PLAGL2 expression was detected in disc tissues. Then, NP cells isolated from disc tissues were used to construct PLAGL2 knockdown cells. PLAGL2 expression in NP cells was analyzed with qRT-PCR and Western blot. The impact of PLAGL2 on the viability, apoptosis, and mitochondria function of NP cells was evaluated by MTT assay, TUNEL, JC1 staining, and flow cytometry assay. Additionally, the regulatory mechanism of PLAGL2 was further assessed. We found that PLAGL2 was upregulated in IVDD disc tissues and serum deprivation (SD)-stimulated NP cells. PLAGL2 knockdown inhibited apoptosis and mitochondria damage in NP cells. Moreover, knockdown of PLAGL2 downregulated the expression of downstream apoptosis-related factors RASSF5, Nip3, and p73. Mechanically, PLAGL2 transcriptionally activated RASSF5 via binding to its promoter. In general, our findings indicate that PLAGL2 induces apoptosis in NP cells and aggravates IVDD progression. This study provides a promising therapeutic target for IVDD treatment.

Whole-transcriptome sequencing identifies key differentially expressed circRNAs/lncRNAs/miRNAs/mRNAs and linked ceRNA networks in adult degenerative scoliosis

Background

Adult degenerative scoliosis (ADS) is forecast to be a prevalent disabling condition in an aging society. Universally, its pathogenesis is perceived as intervertebral disc degeneration (IDD), however, a thought-provoking issue is why precisely a subset of patients with disc degeneration develop ADS. Exploring the diversities between common IDD and ADS would contribute to unraveling the etiological mechanisms of ADS. Therefore, we aimed to integrate the circRNA, lncRNA, miRNA, and mRNA expression profiles from normal adults (Normal), patients with lumbar disc herniation (LDH), and ADS by whole transcriptome sequencing, which identifies critical functional ncRNA and ceRNA networks and crosstalk between the various transcripts.

Methods

The fresh whole blood samples (n = 3/group) were collected from ADS patients, LDH patients, and healthy volunteers (Normal group), which were examined for mRNA, miRNA, lncRNA, and circRNA expression and screened for differentially expressed (DE) ncRNAs. Then, Gene Ontology (GO) and KEGG analyses were performed for gene annotation and enrichment pathways on the DE RNAs, which were constructed as a lncRNA-miRNA-mRNA network. Eventually, DE RNAs were validated by qRT-PCR targeting disc nucleus pulposus (NP) tissue in ADS and LDH group (n = 10/group).

Results

Compared to the LDH group, we identified 3322 DE mRNAs, 221 DE lncRNAs, 20 DE miRNAs, and 15 DE circRNAs in the ADS. In contrast to Normal, 21 miRNAs and 19 circRNAs were differentially expressed in the ADS. The expression of multiple differentially expressed ncRNAs was confirmed by qRT-PCR analysis to be consistent with the sequencing results. In addition, GO, and KEGG analysis demonstrated that most DE mRNAs and ncRNAs target genes are involved in various biological processes, including Endocytosis, Apoptosis, Rap1 signaling pathway, Notch signaling pathway, and others. The constructed lncRNA-miRNA-mRNA co-expression network was primarily related to angiogenesis and regulation.

Conclusion

By focusing on comparing asymmetric and symmetric disc degeneration, whole-transcriptome sequencing and bioinformatics analysis systematically screened for key ncRNAs in the development of ADS, which provided an abundance of valuable candidates for the elucidation of regulatory mechanisms. The DE ncRNAs and the lncRNA-miRNA-mRNA network are intrinsically involved in the regulation of mediator and angiogenesis, which may contribute to the insight into the pathogenesis of ADS.

Interleukin-18 Inhibition Protects Against Intervertebral Disc Degeneration via the Inactivation of Caspase-3/9 Dependent Apoptotic Pathways

BACKGROUND

The present study was designed to identify and understand the potential effectiveness of therapeutic target in intervertebral disc degeneration (IVDD) and its regulation mechanism.

METHODS

The role and mechanism of interleukin-18 (IL-18) in the disease were investigated. The IVDD degenerative nucleus pulposus (NP) tissues from the human and mouse models were used.A total of three groups of Male BALB/c mice were randomly made i.e control, IVDD, and IVDD+Ad-shIL-18 groups. After Ad-shIL-18 transfection, the expression of ECM synthesis related protein Aggrecan (ACAN) and Collagen II, apoptotic effector Caspases (Caspase-3, 8, 9, 12 and Cleaved-Caspase 3, 8, 9, 12), pro-apoptotic gene Bax and anti-apoptotic factors Bcl-2 in NP cells of the human were evaluated.

RESULTS

The results of our study revealed that the mRNA and protein expression levels of IL-18 were notably increased in the NP tissues of IVDD patients and mice models. In the IVDD mice model, Ad-sh-IL-18 treatment reversed the IVDD progression. The levels of Aggrecan and Collagen II, contributing to ECM degradation in NP cells, were also significantly increased. Additionally, Ad-sh-IL-18 could inhibit the NP cell's apoptosis via regulating the caspase-3/9 pathway.

CONCLUSION

The IL-18 knockdown via the caspase-3/9 pathway, might reduce the NP cell's death as well as the imbalance between catabolism and anabolism of ECM in IVDD.

Single-Cell RNA-Seq Analysis of Cells from Degenerating and Non-Degenerating Intervertebral Discs from the Same Individual Reveals New Biomarkers for Intervertebral Disc Degeneration

In this study, we used single-cell transcriptomic analysis to identify new specific biomarkers for nucleus pulposus (NP) and inner annulus fibrosis (iAF) cells, and to define cell populations within non-degenerating (nD) and degenerating (D) human intervertebral discs (IVD) of the same individual. Cluster analysis based on differential gene expression delineated 14 cell clusters. Gene expression profiles at single-cell resolution revealed the potential functional differences linked to degeneration, and among NP and iAF subpopulations. GO and KEGG analyses discovered molecular functions, biological processes, and transcription factors linked to cell type and degeneration state. We propose two lists of biomarkers, one as specific cell type, including C2orf40, MGP, MSMP, CD44, EIF1, LGALS1, RGCC, EPYC, HILPDA, ACAN, MT1F, CHI3L1, ID1, ID3 and TMED2. The second list proposes predictive IVD degeneration genes, including MT1G, SPP1, HMGA1, FN1, FBXO2, SPARC, VIM, CTGF, MGST1, TAF1D, CAPS, SPTSSB, S100A1, CHI3L2, PLA2G2A, TNRSF11B, FGFBP2, MGP, SLPI, DCN, MT-ND2, MTCYB, ADIRF, FRZB, CLEC3A, UPP1, S100A2, PRG4, COL2A1, SOD2 and MT2A. Protein and mRNA expression of MGST1, vimentin, SOD2 and SYF2 (p29) genes validated our scRNA-seq findings. Our data provide new insights into disc cells phenotypes and biomarkers of IVD degeneration that could improve diagnostic and therapeutic options.

IGF Signaling in Intervertebral Disc Health and Disease

Low back pain (LBP) is a common musculoskeletal symptom, which brings a lot of pain and economic loss to patients. One of the most common causes of LBP is intervertebral disc degeneration (IVDD). However, pathogenesis is still debated, and therapeutic options are limited. Insulin-like growth factor (IGF) signaling pathways play an important role in regulating different cell processes, including proliferation, differentiation, migration, or cell death, which are critical to the homeostasis of tissues and organs. The IGF signaling is crucial in the occurrence and progression of IVDD. The activation of IGF signaling retards IVDD by increasing cell proliferation, promoting extracellular matrix (ECM) synthesis, inhibiting ECM decomposition, and preventing apoptosis and senescence of disc cells. However, abnormal activation of IGF signaling may promote the process of IVDD. IGF signaling is currently considered to have a promising treatment prospect for IVDD. An in-depth understanding of the role of IGF signaling in IVDD may help find a novel approach for IVDD treatment.

MiR-1260b protects against LPS-induced degenerative changes in nucleus pulposus cells through targeting TCF7L2

Nucleus pulposus (NP) cells play a critical role in maintaining intervertebral disc integrity through producing the components of extracellular matrix (ECM). NP cell dysfunction, including senescence and hyper-apoptosis, has been regarded as critical events during intervertebral disc degeneration development. In the present study, we found that Transcription Factor 7-Like 2 (TCF7L2) was overexpressed within degenerative intervertebral disc tissue samples, and TCF7L2 silencing improved lipopolysaccharide (LPS)-induced repression on NP cell proliferation, ECM synthesis, and LPS-induced NP cell senescence. miR-1260b directly targeted TCF7L2 and inhibited TCF7L2 expression. miR-1260b overexpression improved LPS-induced degenerative changes in NP cells; more importantly, TCF7L2 overexpression significantly reversed the effects of miR-1260b overexpression on LPS-stimulated degenerative changes within NP cells. For the first time, we demonstrated the function of the miR-1260b/TCF7L2 axis on the phenotypic maintenance of chondrocyte-like NP cells and ECM synthesis by NP cells under LPS stimulation.

Irigenin reduces the expression of caspase-3 and matrix metalloproteinases, thus suppressing apoptosis and extracellular matrix degradation in TNF-α-stimulated nucleus pulposus cells

Irigenin, an isoflavonoid isolated from the rhizome of Belamcanda chinensis, possess various pharmacological effects. However, the effect and mechanism of irigenin on intervertebral disc degeneration (IDD) remain unclear. The potential targets of irigenin or disease were predicted using PharmMapper or GeneCards databases, respectively. The overlapping targets were inputted into the String database to establish protein-protein interaction (PPI) network. The overlapping targets were also submitted to DAVID webserver to perform gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses. Nucleus pulposus (NP) cells were exposed to 10 ng/mL tumor necrosis factor-α (TNF-α) to establish a cell model of IDD. Cell viability, LDH content, apoptosis and caspase-3 activity were evaluated by CCK-8, LDH release, TUNEL, and caspase-3 activity assays, respectively. The expression of collagen II, aggrecan, matrix metalloproteinase (MMP)-2, MMP-3, MMP-9, and MMP-13 were detected by qRT-PCR and western blot analyses. The network analysis revealed that MMP-2, MMP-3, MMP-9, MMP-13, caspase-3 (CASP3), vitamin D receptor (VDR), insulin-like growth factor 1 (IGF1), and transforming growth factor beta2 (TGFB2) play key roles in the effect of irigenin against IDD. TNF-α stimulation inhibited cell viability and increased LDH content, apoptosis, caspase-3 expression and caspase-3 activity in NP cells, which were reversed by irigenin treatment. TNF-α stimulation inhibited the expression of collagen II and aggrecan and upregulated MMPs (MMP-2, MMP-3, MMP-9, and MMP-13) in NP cells, while such changes were abolished by irigenin treatment. In conclusion, irigenin suppressed apoptosis and ECM degradation in TNF-α-stimulated NP cells by reducing the expression of caspase-3 and MMPs.

Antioxidant Effects of Resveratrol in Intervertebral Disk

Intervertebral disk (IVD) degeneration (IVDD) can cause various spinal degenerative diseases. Cumulative evidence has indicated that IVDD can result from inflammation, apoptosis, autophagy, biomechanical changes and other factors. Currently, lack of conservative treatment for degenerative spinal diseases leads to an urgent demand for clinically applicable medication to ameliorate the progression of IVDD. Resveratrol (3,5,4'-trihydroxy-trans-stilbene), a polyphenol compound extracted from red wine or grapes, has shown protective effects on IVD, alleviating the progression of IVDD. Resveratrol has been demonstrated as a scavenger of free radicals both in vivo and in vitro. The antioxidant effects of resveratrol are likely attributed to its regulation on mitochondrial dysfunction or the elimination of reactive oxygen species. This review will summarize the mechanisms of the reactive oxygen species production and elaborate the mechanisms of resveratrol in retarding IVDD progression, providing a comprehensive understanding of the antioxidant effects of resveratrol in IVD.

HOXC13-AS Induced Extracellular Matrix Loss via Targeting miR-497-5p/ADAMTS5 in Intervertebral Disc

Background/Aims: LncRNAs are a new modulator in the development of intervertebral disc degeneration. However, the functional role and mechanism of HOXC13-AS in intervertebral disc degeneration remain unclear. Methods: qRT-PCR analysis was performed to measure the relative expression levels of HOXC13-AS and miR-497-5p, and the levels of IL-1β, IL-6, and TNF-α in the medium supernatant were analyzed by ELISA. The related mechanism between HOXC13-AS and miR-497-5p was detected by luciferase assays. Results: The results revealed that TNF-α and IL-1β induced HOXC13-AS expression in NP cells. HOXC13-AS was overexpressed in IDD specimens compared to control specimens, and higher expression of HOXC13-AS was correlated with high Pfirrmann scores. Ectopic expression of HOXC13-AS promoted MMP-3 and ADAMTS4 and inhibited aggrecan and collagen II expression in NP cells. Furthermore, overexpression of HOXC13-AS increased the expression of inflammatory cytokines, including IL-1β, IL-6, and TNF-α. Our results demonstrated that TNF-α and IL-1β induced ADAMTS5 expression and suppressed miR-497-5p expression. miR-497-5p was downregulated in IDD specimens compared to control specimens, and the lower expression of miR-497-5p was correlated with high Pfirrmann scores. The miR-497-5p level was negatively proportional to HOXC13-AS expression in IDD specimens. Luciferase analysis data indicated that ADAMTS5 was a direct target gene of miR-497-5p. HOXC13-AS induced inflammatory cytokine expression and ECM degradation by modulating miR-497-5p/ADAMTS5. Conclusion: HOXC13-AS may be a treatment target for IDD.

Long non-coding RNA RP11-81H3.2 suppresses apoptosis by targeting microRNA-1539/COL2A1 in human nucleus pulposus cells

Intervertebral disk degeneration (IDD) is a severe health problem that results in lower back pain and disability. Previous evidence has indicated that excessive apoptosis of nucleus pulposus (NP) cell is involved in the occurrence and development of IDD. However, the underlying mechanisms regulating NP cell apoptosis are unclear. The present study aimed to investigate the function of a novel long non-coding RNA RP11-81H3.2 in modulating NP cell apoptosis and the potential underlying mechanisms. The results demonstrated that the RP11-81H3.2 expression levels were significantly decreased in NP tissues from patients with IDD compared with those from healthy controls, and that lower expression levels were associated with higher-grade disk degeneration. Functionally, RP11-81H3.2 silencing promoted apoptosis and decreased the viability of NP cells derived from tissue samples of patients with IDD, whereas RP11-81H3.2 overexpression induced opposite effects. Bioinformatics analysis, luciferase assays and reverse transcription-quantitative PCR revealed that microRNA (miR)-1539 was a direct target of RP11-81H3.2. A mechanistic analysis demonstrated that RP11-81H3.2 functioned as an RNA sink to downregulate miR-1539, which led to the upregulation of collagen type 2 α 1 chain (COL2A1), a target of miR-1539. Collectively, the present results suggested that lower RP11-81H3.2 expression levels were associated with higher-grade IDD, and that RP11-81H3.2 inhibited NP cell apoptosis by decreasing the levels of miR-1539 to increase COL2A1 expression levels. The present study identified a beneficial role of RP11-81H3.2 against NP cell apoptosis.

Current Progress in the Endogenous Repair of Intervertebral Disk Degeneration Based on 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.

Mechanical Regulation of Apoptosis in the Cardiovascular System

Apoptosis is a highly conserved physiological process of programmed cell death which is critical for proper organism development, tissue maintenance, and overall organism homeostasis. Proper regulation of cell removal is crucial, as both excessive and reduced apoptotic rates can lead to the onset of a variety of diseases. Apoptosis can be induced in cells in response to biochemical, electrical, and mechanical stimuli. Here, we review literature on specific mechanical stimuli that regulate apoptosis and the current understanding of how mechanotransduction plays a role in apoptotic signaling. We focus on how insufficient or excessive mechanical forces may induce apoptosis in the cardiovascular system and thus contribute to cardiovascular disease. Although studies have demonstrated that a broad range of mechanical stimuli initiate and/or potentiate apoptosis, they are predominantly correlative, and no mechanisms have been established. In this review, we attempt to establish a unifying mechanism for how various mechanical stimuli initiate a single cellular response, i.e. apoptosis. We hypothesize that the cytoskeleton plays a central role in this process as it does in determining myriad cell behaviors in response to mechanical inputs. We also describe potential approaches of using mechanomedicines to treat various diseases by altering apoptotic rates in specific cells. The goal of this review is to summarize the current state of the mechanobiology field and suggest potential avenues where future research can explore.

CircGLCE alleviates intervertebral disc degeneration by regulating apoptosis and matrix degradation through the targeting of miR-587/STAP1

The purpose of this study was to identify a specific circular RNA and to investigate its regulatory mechanism in intervertebral disc degeneration (IDD). CircGLCE was selected after microarray analyses and was further analysed by RT-qPCR and FISH. CircGLCE was found to stably exist in the cytoplasm of nucleus pulposus (NP) cells. It was downregulated in IDD. After silencing CircGLCE, its function was assessed with RT-qPCR, immunofluorescence analysis and flow cytometry. Knockdown of CircGLCE promoted apoptosis and induced the expression of matrix-degrading enzymes in NP cells. CircGLCE served as a miR-587 sponge in NP cells. Inhibiting miR-587 counteracted the IDD-enhancing effect caused by silencing CircGLCE. STAP1 served as the miRNA target that mediated the functions of miR-587. In an IDD mouse model, the in vivo effects of overexpressing CircGLCE on IDD were confirmed by imaging techniques, TUNEL staining, FISH, western blotting, H&E staining and immunohistochemistry. Thus, CircGLCE attenuates IDD by inhibiting the apoptosis of NP cells and ECM degradation through the targeting of miR-587/STAP1. CircGLCE may be a potential therapeutic target for IDD treatments.

Mesenchymal stem cells regulate inflammatory milieu within degenerative nucleus pulposus cells via p38 MAPK pathway

It has been established that excessive apoptosis of nucleus pulposus cells (NPCs) are responsible for pathogenesis of human intervertebral disc degeneration (IDD). The present study aimed to shed light on the molecular mechanisms underlying the protective effects of mesenchymal stem cells (MSCs) on NPCs in an inflammatory environment. NPCs were treated with TNF-α to induce inflammation and then co-cultured with Wharton's Jelly-derived MSCs (WJ-MSCs)without direct interaction. The levels of inflammation markers (IL-1β, IL-6 and IL-8) in NPCs were detected by performing enzyme-linked immunosorbent assay (ELISA), and expression of metalloproteases and aggrecan, as well as the activity of p38 MAPK pathway were determined through immunoblotting. SB-203580 was used to inhibit p38 signaling, prior to evaluation of the effects of Wharton's Jelly-derived MSCs (WJ-MSCs) on inflammatory response within the co-cultured NPCs. After TNF-α treatment, the levels of inflammatory cytokines, MMP-3, and MMP-13 in NPCs were increased whereas aggrecan was decreased, which was then dramatically reversed by WJ-MSCs co-culture. Likewise, WJ-MSCs suppressed TNF-α-induced phosphorylation of p38 MAPK signaling components including p38, ASK-1, MKK-3 and MKK-6. Blocking p38 MAPK pathway enhanced the anti-inflammatory impact of WJ-MSCs, and there was no significant difference between NPCs co-cultured with WJ-MSCs or the cells cultured alone. WJ-MSCs co-culture mitigate TNF-α-induced inflammatory response and ECM degeneration in NPCs, the major pathological events are implicated in IDD development, probably by suppressing the p38 MAPK signaling cascade.

Updated Understanding of the Degenerative Disc Diseases - Causes Versus Effects - Treatments, Studies and Hypothesis

BACKGROUND

In this review we survey medical treatments and research strategies, and we discuss why they have failed to cure degenerative disc diseases or even slow down the degenerative process.

OBJECTIVE

We seek to stimulate discussion with respect to changing the medical paradigm associated with treatments and research applied to degenerative disc diseases.

METHOD PROPOSAL

We summarize a Biological Transformation therapy for curing chronic inflammations and degenerative disc diseases, as was previously described in the book Biological Transformations controlled by the Mind Volume 1.

PRELIMINARY STUDIES

A single-patient case study is presented that documents complete recovery from an advanced lumbar bilateral discopathy and long-term hypertrophic chronic rhinitis by application of the method proposed.

CONCLUSION

Biological transformations controlled by the mind can be applied by men and women in order to improve their quality of life and cure degenerative disc diseases and chronic inflammations illnesses.

LINC01121 induced intervertebral disc degeneration via modulating miR-150-5p/MMP16 axis

BACKGROUND

Growing evidence indicates that Long noncoding RNAs contribute to cell differentiation, invasion, metabolism, proliferation and metastasis. However, the potential role of LINC01121 in progression of intervertebral disc degeneration (IDD) remains unclear.

METHODS

LINC01121, matrix metalloprotease (MMP)-16 and miR-150-5p expression was determined by a quantitative-reverse transcriptase-polymerase chain reaction assay. Inflammatory cytokines level was measured by an enzyme-linked immunosorbent assay and cell counting kit-8 analysis was used to assess cell proliferation. MMP-16-specific binding with miR-150-5p was verified with a luciferase reporter assay.

RESULTS

We noted that interleukin (IL)-1β and tumor necrosis factor (TNF)-α treatment enhanced LINC01121 and MMP-16 expression in nucleus pulposus (NP) cells. LINC01121 was higher in IDD specimens compared to that in control specimens. Higher expression of LINC01121 was correlated with disc degeneration degree. Ectopic expression of LINC01121 enhanced cell proliferation and promoted ki-67, MMP-3 and ADAMTS5 expression and also suppressed collagen II expression in NP cells. We observed that overexpression of LINC01121 increased the secretion of three inflammatory cytokines, including IL-6, TNF-α and IL-1β. We found that ectopic expression of LINC01121 decreased the miR-150-5p level in NP cells. Luciferase reporter data confirmed that MMP-16 was one direct target of miR-150-5p. Overexpression of miR-150-5p inhibited MMP-16 level and elevated the expression of LINC01121 enhanced MMP-16 level. We also found that MMP-16 was up-regulated in IDD specimens compared to that in control specimens. Higher expression of MMP-16 was correlated with disc degeneration degree. Interestingly, MMP-16 expression was positively related to LINC01121 in IDD specimens. Finally, overexpression of LINC01121 regulated cell growth, extracellular matrix degradation and inflammatory cytokine secretion via modulating MMP-16.

CONCLUSIONS

our data suggested LINC01121 may be a new therapeutic target for IDD.

X irradiation induced colonic mucosal injury and the detection of apoptosis through PARP-1/p53 regulatory pathway

This study aimed to explore whether PARP-1 regulatory pathway mediated X irradiation induced cell cycle arrest and apoptosis or not. In this regard, colonic mucosal injury caused by whole-body X-irradiation induced apoptosis through PARP-1, caspase 3 and p53 regulatory pathway were evaluated in experimental rat models. Eighteen Wistar albino rats were divided into three groups. Two radiation groups received 8.3 Gy dose of whole-body X-irradiation as a single dose and the control group received physiological saline intraperitoneally. Radiation groups were sacrificed after 6 h and 4 days of irradiation. PARP-1 and caspase 3 expression in the nuclei of colonic crypt cells significantly increased 6 h after irradiation, and declined 4 days after irradiation. In conflict with other studies that reported p53 as not being expressed widely in colonic mucosa, in our study the expressions of p53 were elevated both in the cytoplasm and in the nucleus of the crypt cells, especially 6 h after irradiation. In the radiation groups, colonic mucosal injury score was significantly elevated compared with that of the control group. Our data demonstrated that PARP-1, caspase-3 and p53 expression increased in colonic mucosa 6 h after irradiation.

Resveratrol Combined with 17β-Estradiol Prevents IL-1β Induced Apoptosis in Human Nucleus Pulposus Via The PI3K/AKT/Mtor and PI3K/AKT/GSK-3β Pathway

BACKGROUNDS

Nucleus pulposus (NP) apoptosis is mainly charged for the pathological process of Intervertebral disc degeneration (IVDD). Our previous study revealed that Resveratrol (RSV) combined with 17β-estradiol (E2) was more effective in cutting down IL-1β induced NP cell apoptosis via PI3K/AKT pathway. The present study further evaluated the effect of RSV and E2 in the anti-apoptosis process of IVDD.

METHODS

Human nucleus pulposus (NP) cells culture system and IL-1β inducing apoptosis model were constructed in this research. RSV and E2 were used to inhibit apoptosis. FACS (Fluorescence-activated cell sorting) and CCK-8 (Cell Counting Kit-8) assays were respectively used to determine apoptotic incidence and cell viability of NP cells. Quantitative RT-PCR was used to determine expression of target genes in mRNA level, and western blot analysis was performed to detect the changes of related protein expression.

RESULTS

RSV combined with E2 attenuated IL-1β-induced cell apoptosis and recovered cell viability. Blockers for mTOR and GSK-3β abated the effect of RSV and E2. RSV combined with E2 obviously increased activated P-mTOR and P-GSK-3β, which contributes to the downregulation of caspase-3. Activated P-NF-kappa B was not involved in the anti-apoptosis process of RSV and E2.

CONCLUSION

Combination of Resveratrol and 17β-estradiol efficiently resisted IL-1β induced apoptosis of NP cell, mainly through PI3K/AKT/mTOR/caspase-3 and PI3K/AKT/GSK-3β pathway.

Suppression of miR-203-3p inhibits lipopolysaccharide induced human intervertebral disc inflammation and degeneration through upregulating estrogen receptor α

Accumulating evidence demonstrates that estrogen receptor α (ERα) and microRNAs (miRNAs) play crucial roles in intervertebral disc degeneration (IDD). However, the specific miRNA that related with ERα during IDD development remains unknown. Therefore, we aimed to explore the role of ERα-related miRNA in the IDD model. Nucleus pulposus (NP) cells were isolated from IDD patients. ERα-related miRNAs were selected and verified in NP tissues from IDD patients using quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Also, the related cytokine mRNA levels were detected by qRT-PCR. Protein levels were determined by Western blot. The concentrations of inflammatory cytokines in culture supernatants were detected by enzyme-linked immunosorbent assay. MiR-203-3p was found to be upregulated in NP tissues of high-grade IDD patients compared with low-grade IDD patients, and negatively associated with ERα expression. MiR-203-3p directly targeted ERα in NP cells of IDD patients. After lipopolysaccharides (LPS) stimulation, miR-203-3p expression increased, while ERα expression decreased in NP cells. MiR-203-3p inhibition suppressed the effect of LPS on ERα expression and IDD related genes, while ERα downregulation rescued the effect of LPS. In conclusion, suppression the expression of miR-203-3p could inhibit LPS-induced human intervertebral disc inflammation and degeneration through upregulating ERα.

Circular RNAs in nucleus pulposus cell function and intervertebral disc degeneration

Intervertebral disc degeneration (IDD) is a common cause of low back pain, which inflicts more global disability than any other condition. Although IDD was deemed to be a natural process that comes with ageing, a growing body of evidence suggested that both genetic and environmental factors could modify the development of IDD. In this connection, aberrant function of nucleus pulposus cells has been implicated in IDD pathogenesis. Circular RNAs are a novel class of endogenous non-coding RNAs that play crucial regulatory roles in diverse cellular processes. Recently, deregulation of circRNAs in nucleus pulposus cells was found to functionally participate in IDD development. In this review, we summarize the current knowledge regarding the deregulation of circRNAs in IDD in relation to their actions on nucleus pulposus cell functions, including cell proliferation, apoptosis and extracellular matrix synthesis/degradation. The potential clinical utilities of circRNAs as therapeutic targets for the management of IDD are also discussed.

Long non-coding RNA HOTAIR modulates intervertebral disc degenerative changes via Wnt/β-catenin pathway

BACKGROUND

Intervertebral disc degeneration (IDD) has a complicated and enigmatic pathogenic process. Accumulating evidence shows that long non-coding RNAs (LncRNAs) play a role in the pathogenesis of IDD. This study aimed to investigate the expression and role of the LncRNA HOTAIR in IDD pathogenesis.

METHODS

Nucleus pulposus (NP) tissue samples from 10 patients with idiopathic scoliosis and 10 patients with lumbar disc herniation were collected. qRT-PCR was used to assess the expression of HOTAIR and ECM-related genes; western blotting was used to detect the expression of senescence biomarkers, apoptosis-related proteins, and Wnt/β-catenin pathway; flow cytometry was used to detect apoptosis; and the MTT assay was used to determine cell proliferation. Moreover, a classic needle-punctured rat tail model was used to investigate the role of HOTAIR in IDD in vivo.

RESULTS

The results showed that the expression of HOTAIR significantly increased during IDD progression. The overexpression of HOTAIR was found to induce nucleus pulposus (NP) cell senescence, apoptosis, and extracellular matrix (ECM) degradation. HOTAIR silencing by RNA interference in NP cells prevented interleukin-1β-induced NP cell senescence, apoptosis, and ECM degradation. Furthermore, we found that the Wnt/β-catenin pathway played a role in regulating HOTAIR to induce these changes in NP cells. Moreover, HOTAIR inhibition in a rat model effectively attenuated IDD symptoms in vivo.

CONCLUSIONS

Our findings confirmed that HOTAIR promoted NP cell senescence, apoptosis, and ECM degradation via the activation of the Wnt/β-catenin pathway, while silencing HOTAIR attenuated this degeneration process, indicating a potential therapeutic target against IDD.

Knockdown of miR-222 inhibits inflammation and the apoptosis of LPS-stimulated human intervertebral disc nucleus pulposus cells

It has been demonstrated that miR‑222 is upregulated in human intervertebral disc (IVD) degeneration tissues; however, the underlying mechanisms remain unclear. In this study, we aimed to elucidate the mechanisms of action of miR‑222 in IVD tissues. Nucleus pulposus (NP) cells were treated with lipopolysaccharide (LPS) to simulate IVD degeneration. The expression level of miR‑222 was detected by reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) in cells and tissues. Cell apoptosis was analyzed by flow cytometry. Additionally, western blot analysis was used to determine the levels of Toll‑like receptor 4 (TLR4), Iκβ‑alpha (IκBα) and p65. Interleukin (IL)‑1β, tumor necrosis factor‑α (TNF‑α) and IL‑6 protein expression levels were determined by enzyme‑linked immunosorbent assay (ELISA). The target gene of miR‑222 was determined by TargetScan7.2 and dual luciferase reporter gene analysis. Western blot analysis and RT‑qPCR were used to determine the mRNA and protein levels of tissue inhibitor of metalloproteinase 3 (TIMP3). The mRNA expression level of miR‑222 was found to be increased in IVD tissues and in LPS‑stimulated cells, and its expression was positively associated with the clinical MRI grade. In vitro, apoptosis was promoted/inhibited by miR‑222 mimics/inhibitors. Transfection with miR‑222 mimics/inhibitors significantly increased/decreased the production of TNF‑α, IL‑1β and IL‑6 and suppressed/enhanced collagen II and aggrecan expression. The protein levels of TLR4, p‑IκΒα and p‑p65 were upregulated/downregulated by transfection with the mimics/inhibitors. In addition, it was demonstrated that TIMP3 was a direct target gene of miR‑222, and was negatively regulated by miR‑222 in NP cells. The silencing of TIMP3 reversed the inhibitory effects of miR‑222 inhibitor on cell apoptosis, which was induced by LPS. Thus, on the whole, the findings of this study demonstrate that miR‑222 functions as a promoter of IVD development, partly via the regulation of TIMP3.

Upregulated miR-154 promotes ECM degradation in intervertebral disc degeneration

Intervertebral disc degeneration (IDD), a common global health issue, is a major cause for low back pain (LBP). Given the complex etiology of IDD, micro RNA (miRNA) recently has been demonstrated to play essential roles in the progression of IDD. Therefore, this study aims to investigate functions of the miR-154, which is well-documented in a series of cell activities, IDD, and other relevant mechanisms. Lumbar nucleus pulposus (NP) samples were collected from patients with IDD and the control group. After solexa sequencing and bioinformatical analysis, the results showed that miR-154 was increased in NP cells of patients with IDD. Inhibition of miR-154 increased type II collagen and aggrecan and decreased mRNA expressions of collagenase-3 (MMP13) and aggrecanase-1 (ADAMTS4), whereas overexpression of miR-154 reversed such effects in NP cells. In addition, the luciferase reporter assay revealed that fibroblast growth factor 14 (FGF14) is a direct target of miR-154 and that the overexpression of FGF14 leads to similar effects as inhibition of miR-154 did. In conclusion, the results suggested that miR-154 participates in the development of IDD and its effects are mediated via targeting FGF14. Thus, miR-154 may be thought as a potential etiological factor for IDD and may provide insights into a therapeutic target to treat IDD.

Evaluation of a Cost-Effective Novel Diagnostic Method for Lumbar Herniated Disc with Knee-Osteoarthritis: A Randomized Sample Study

The aim of this study was to determine a cost-effective diagnostic method for lumbar herniated disc with knee osteoarthritis (LHD-KOA) based on aberrant outcome measures, levels of biomarkers, and examination of the lower-extremity. Data were separately analyzed for each cohort suffering with LHD-KOA (n=108; 59.82±7.15years) and without LHD-KOA (n=108; 58.81±7.61years), and findings were confirmed with radiological images. The aberrant-leg-features (bilateral: knee gaps between the short head of biceps femoris and the surface of the bed, diameters of calves and thighs, angles of straight leg raising, knee-flexion and -extension in a supine position) and biochemical parameters (Interleukin-10, Tumor necrosis factor-alpha, C-reactive protein, creatine kinase-muscle, and Aldolase-A), and outcome measures, Western Ontario and McMaster Universities osteoarthritis index (WOMAC), knee-injury osteoarthritis outcomes scale (KOOS), Oswestry disability index (ODI), and body mass index (BMI)for participants with and without LHD-KOA were evaluated with appropriate techniques. All the subjects underwent standardized physical examination and completed a questionnaire. The risk ratios and mean± standard deviations of biomarkers, anatomical features, and outcome measures of the experimental subjects were highly significant compared to controls (p<0.0001). Results suggest that monitoring the studied aberrant outcome measures, biomarkers, and lower-anatomical features may be a cost-effective diagnostic tool for LHD-KOA. Further research is recommended for an alternative treatment protocol for LHD-KOA.

Molecular Detection and Assessment of Intervertebral Disc Degeneration via a Collagen Hybridizing Peptide

During aging, wear, and tear of intervertebral discs, human discs undergo a series of morphological and biochemical changes. Degradation of extracellular matrix proteins, e.g., collagen, arises as an important contributor and accelerator in this process. Existing methods to detect collagen degradation at the tissue level include histology and immunohistochemistry. Unfortunately, most of these methods only depict overall collagen content without the ability to specifically discern degraded collagen and to assess the severity of degeneration. To fill this technological gap, we developed a robust and simple approach to detect and assess early disc degeneration with a collagen hybridizing peptide (CHP) that hybridizes with the flawed triple helix structure in degraded collagen. Intriguingly, the CHP signal in mouse lumbar discs exhibited a linear incremental pattern with age. This finding was corroborated with histological analysis based on established methods. When comparing this analysis, a positive linear correlation was found between CHP fluorescence intensity and the histological score with a regression value of r ² = 0.9478. In degenerative mouse discs elicited by pro-inflammatory stimuli (IL-1β and LPS) ex vivo, the newly developed approach empowered prediction of the severity of disc degeneration. We further demonstrated higher CHP signals in a degenerative human disc tissue when compared to a normal sample. These findings also resonated with histological analysis. This approach lays a solid foundation for specific detection and assessment of intervertebral disc degeneration at the molecular level and will promote development of future disc regeneration strategies.

miRNA-155 expression and role in pathogenesis in spinal tuberculosis-induced intervertebral disc destruction

The current study aimed to investigate microRNA-155 (miR-155) expression in spinal tuberculosis-induced intervertebral disc destruction and its regulatory role in disease pathogenesis. A total of 26 patients with intervertebral disc destruction induced by spinal tuberculosis and 31 healthy individuals were included. Reverse transcription-quantitative polymerase chain reactions, western blot analysis and ELISA were performed to detect mRNA and protein expression levels. A bioinformatics analysis was applied to predict the upstream regulator of matrix metalloproteinase (MMP)13, which was confirmed by dual-luciferase reporter assay. Compared with the control group, mRNA and protein expression levels of MMP13 were significantly increased in the intervertebral disc of patients with spinal tuberculosis. However, miR-155 expression in the intervertebral disc of patients with spinal tuberculosis was significantly decreased compared with the control group. Dual-luciferase reporter assays suggested that miR-155 bound to the 3′-untranslated region of MMP13 to regulate gene expression. In primary annulus fibrosus cells, upregulated miR-155 expression significantly decreased MMP13 expression in the cells and culture supernatant, whereas it increased type II collagen expression. Upregulated MMP13 expression in the intervertebral disc in patients with spinal tuberculosis may be correlated with downregulated miR-155 expression. miR-155 may regulate expression levels of associated proteins in the intervertebral disc via modulating MMP13 expression, which contributes to the disease pathogenesis. The results of the current study may provide the theoretical basis for the diagnosis and treatment of disc damages caused by spinal tuberculosis.

Long non-coding RNAs in nucleus pulposus cell function and intervertebral disc degeneration

Intervertebral disc degeneration (IDD) is the major cause of low back pain which incurs a significant public-health and economic burden. The aetiology of IDD is complex, with developmental, genetic, biomechanical and biochemical factors contributing to the disease development. Deregulated phenotypes of nucleus pulposus cells, including aberrant differentiation, apoptosis, proliferation and extracellular matrix deposition, are involved in the initiation and progression of IDD. Non-coding RNAs, including long non-coding RNAs (lncRNAs), have recently been identified as important regulators of gene expression. Research into their roles in IDD has been very active over the past 5 years. Our review summarizes current research regarding the roles of deregulated lncRNAs (eg, RP11-296A18.3, TUG1, HCG18) in modulating nucleus pulposus cell functions in IDD. These exciting findings suggest that specific modulation of lncRNAs or their downstream signalling pathways might be an attractive approach for developing novel therapeutics for IDD.

microRNA-665 promotes the proliferation and matrix degradation of nucleus pulposus through targeting GDF5 in intervertebral disc degeneration

Growing evidences suggested that microRNAs (miRNAs) played important roles in the development of intervertebral disc degeneration (IDD). However, the expression level and function of miR-665 in IDD remain unknown. In this study, we showed that the expression level of miR-665 was upregulated in degenerative human NP samples. In addition, miR-665 expression level gradually increased with the exacerbation of disc degeneration grade. Moreover, miR-665 expression level was positively associated with the Pfirrmann grade. Ectopic expression of miR-665 promoted NP cell growth. Furthermore, miR-665 overexpression decreased aggrecan and Col II expression and ectopic expression of miR-665 increased MMP-3 and MMP-13 expression in NP cell. We identified growth differentiation factor 5 (GDF5) was a direct target gene of miR-665 in NP cell and enforced expression of miR-665 decreased GDF5 expression. Elevated expression of miR-665 enhanced NP cell proliferation and decreased aggrecan and Col II expression. In addition, ectopic expression of miR-665 increased MMP-3 and MMP-13 expression through inhibiting GDF5 expression in NP cells. These results suggested that dysregulated miR-665 expression might act an important role in the development of IDD.

Spermidine promotes nucleus pulposus autophagy as a protective mechanism against apoptosis and ameliorates disc degeneration

Spermidine has therapeutic effects in many diseases including as heart diastolic function, myopathic defects and neurodegenerative disorders via autophagy activation. Autophagy has been found to mitigate cell apoptosis in intervertebral disc degeneration (IDD). Accordingly, we theorize that spermidine may have beneficial effects on IDD via autophagy stimulation. In this study, spermidine's effect on IDD was evaluated in tert‐butyl hydroperoxide (TBHP)‐treated nucleus pulposus cells of SD rats in vitro as well as in a puncture‐induced rat IDD model. We found that autophagy was actuated by spermidine in nucleus pulposus cells. In addition, spermidine treatment weakened the apoptotic effects of TBHP in nucleus pulposus cells. Spermidine increased the expression of anabolic proteins including Collagen‐II and aggrecan and decreased the expression of catabolic proteins including MMP13 and Adamts‐5. Additionally, autophagy blockade using 3‐MA reversed the beneficial impact of spermidine against nucleus pulposus cell apoptosis. Autophagy was thus important for spermidine's therapeutic effect on IDD. Spermidine‐treated rats had an accentuated T2‐weighted signal and a diminished histological degenerative grade than vehicle‐treated rats, showing that spermidine inhibited intervertebral disc degeneration in vivo. Thus, spermidine protects nucleus pulposus cells against apoptosis through autophagy activation and improves disc, which may be beneficial for the treatment of IDD.

An ultrastructural study of chondroptosis: programmed cell death in degenerative intervertebral discs in vivo

Apoptosis has been regarded to mediate intervertebral disc degeneration (IDD); however, the basic question of how the apoptotic bodies are cleared in the avascular intervertebral disc without phagocytes, which are essential to apoptosis, remains to be elucidated. Our goals were to investigate the ultrastructure of nucleus pulposus (NP) cells undergoing chondroptosis, a variant of apoptotic cell death, in a rabbit annular needle-puncture model of IDD. Experimental IDD was induced by puncturing discs with a 16-G needle in New Zealand rabbits. At 4 and 12 weeks after puncture, progressive degeneration was demonstrated by X-ray, magnetic resonance imaging and histological staining. TUNEL staining suggested a significant increase in the apoptosis index in the degenerated NP. However, the percentage of apoptotic cells with the classic ultrastructure morphology was much less than that with chondroptotic ultrastructure morphology under transmission electron microscopy (TEM). The chondroptotic cells from the early to late stage were visualized under TEM. In addition, the percentage of chondroptotic cells was significantly enhanced in the degenerated NP. Furthermore, 'paralyzed' cells were found in the herniated tissue. Western blotting revealed an increase in caspase3 expression in the degenerated NP. The expression of the Golgi protein (58K) was increased by the fourth week after puncture but decreased later. These findings indicate that chondroptosis is a major type of programmed cell death in the degenerated rabbit NP that may be related to the progressive development of IDD.

A novel culture platform for fast proliferation of human annulus fibrosus cells

Tissue engineering provides a promising approach to treat degenerative disc disease, which usually requires a large quantity of seed cells. A simple and reliable in vitro culture system to expand seed cells in a timely fashion is necessary to implement the application clinically. Here, we sought to establish a cost-effective culture system for expanding human annulus fibrosus cells using extracellular matrix (ECM) proteins as culture substrates. Cells were cultured onto a plastic surface coated with various types of ECMs, including fibronectin, vitronectin, collagen type I, gelatin and cell-free matrix deposited by human nucleus pulposus cells. AF cell morphology, growth, adhesion and phenotype (anabolic and catabolic markers) were assessed by microscopy, real-time RT-PCR, western blotting, zymography, immunofluorescence staining and biochemical assays. Fibronectin, collagen and gelatin promoted cell proliferation and adhesion in a dose-dependent manner. Fibronectin elevated mRNA expression of proteoglycan and enhanced glycosaminoglycan production. Both collagen and gelatin increased protein expression of type II collagen. Consistent with increased cell adhesion, collagen and fibronectin promoted formation of focal adhesion complexes in the cell-matrix junction, suggesting enhanced binding of the actin network with both ECM substrates. On the other hand, fibronectin, collagen and gelatin decreased expression of matrix metalloproteinase-2 and matrix metalloproteinase-9 in media. Finally, a mixture of fibronectin (1.7 μg/mL) and collagen (1.3 μg/mL) was identified as the most promising in vitro culture substrate system in promoting proliferation and maintaining anabolic-catabolic balance. Our method provides a simple and cost-effective platform for tissue engineering applications in intervertebral disc research.

Macrophage Inhibition Factor-Mediated CD74 Signal Modulate Inflammation and Matrix Metabolism in the Degenerated Cartilage Endplate Chondrocytes by Activating Extracellular Signal Regulated Kinase 1/2

STUDY DESIGN

The macrophage inhibition factor (MIF)-mediated CD74 dependent extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation were associated with inflammatory activity and matrix metabolism in human degenerated cartilage endplate (CEP). Anabolic/catabolic factors in pathogenesis of CEP degeneration were evaluated.

OBJECTIVE

To study the effect of MIF-mediated CD74 dependent ERK1/2 activation on the CEP degeneration.

SUMMARY OF BACKGROUND DATA

MIF-CD74 signal is closely related to the CEP degeneration by inducing the secretion of inflammatory cytokines. ERK1/2-mediated inflammatory pathway also plays a crucial role in the intervertebral disc degeneration. The role of the ERK1/2 pathway in CEP chondrocytes response to MIF-CD74 signal has, however, not been fully elucidated.

METHODS

Chondrocytes were exposed to MIF, with or without ERK1/2 inhibition; CD74 interfered chondrocytes were also exposed to MIF, with or without ERK inhibition. mRNAs were isolated for real-time polymerase chain reaction measurement of gene expression. Western blotting was carried out to analyze the protein expression.

RESULTS

ERK1/2 expression was significantly increased by MIF. MIF modulates metabolism in CEP chondrocytes and decreased by its inhibitor PD98059. ERK1/2 expression was significantly decreased by CD74siRNA. Inflammatory cytokines expression was significantly increased by MIF-induced ERK1/2 activation and significantly suppressed by PD98059. On the contrary, matrix expression was significantly decreased by MIF-induced ERK1/2 activation and reversed by PD98059. CD74siRNA decreased the CD74 expression in chondrocytes. Inflammatory cytokines and matrix expression were not induced by MIF in CD74 interfered chondrocytes.

CONCLUSION

These results show that MIF-CD74 signal elicits an imbalance between anabolic and catabolic metabolism in CEP chondrocytes via ERK signal pathway. ERK inhibition could exert therapeutic effect against the harmful effects of MIF-CD74 signal in CEP degeneration.

LEVEL OF EVIDENCE

N/A.

AGEs induce ectopic endochondral ossification in intervertebral discs

Ectopic calcifications in intervertebral discs (IVDs) are known characteristics of IVD degeneration that are not commonly reported but may be implicated in structural failure and dysfunctional IVD cell metabolic responses. This study investigated the novel hypothesis that ectopic calcifications in the IVD are associated with advanced glycation end products (AGEs) via hypertrophy and osteogenic differentiation. Histological analyses of human IVDs from several degeneration stages revealed areas of ectopic calcification within the nucleus pulposus and at the cartilage endplate. These ectopic calcifications were associated with cells positive for the AGE methylglyoxal-hydroimidazolone-1 (MG-H1). MG-H1 was also co-localised with Collagen 10 (COL10) and Osteopontin (OPN) suggesting osteogenic differentiation. Bovine nucleus pulposus and cartilaginous endplate cells in cell culture demonstrated that 200 mg/mL AGEs in low-glucose media increased ectopic calcifications after 4 d in culture and significantly increased COL10 and OPN expression. The receptor for AGE (RAGE) was involved in this differentiation process since its inhibition reduced COL10 and OPN expression. We conclude that AGE accumulation is associated with endochondral ossification in IVDs and likely acts via the AGE/RAGE axis to induce hypertrophy and osteogenic differentiation in IVD cells. We postulate that this ectopic calcification may play an important role in accelerated IVD degeneration including the initiation of structural defects. Since orally administered AGE and RAGE inhibitors are available, future investigations on AGE/RAGE and endochondral ossification may be a promising direction for developing non-invasive treatment against progression of IVD degeneration.

Temporal Analyses of the Response of Intervertebral Disc Cells and Mesenchymal Stem Cells to Nutrient Deprivation

Much emphasis has been placed recently on the repair of degenerate discs using implanted cells, such as disc cells or bone marrow derived mesenchymal stem cells (MSCs). This study examines the temporal response of bovine and human nucleus pulposus (NP) cells and MSCs cultured in monolayer following exposure to altered levels of glucose (0, 3.15, and 4.5 g/L) and foetal bovine serum (0, 10, and 20%) using an automated time-lapse imaging system. NP cells were also exposed to the cell death inducers, hydrogen peroxide and staurosporine, in comparison to serum starvation. We have demonstrated that human NP cells show an initial “shock” response to reduced nutrition (glucose). However, as time progresses, NP cells supplemented with serum recover with minimal evidence of cell death. Human NP cells show no evidence of proliferation in response to nutrient supplementation, whereas MSCs showed greater response to increased nutrition. When specifically inducing NP cell death with hydrogen peroxide and staurosporine, as expected, the cell number declined. These results support the concept that implanted NP cells or MSCs may be capable of survival in the nutrient-poor environment of the degenerate human disc, which has important clinical implications for the development of IVD cell therapies.

Current trends in biologics delivery to restore intervertebral disc anabolism

Low back pain is generally attributed to intervertebral disc (IVD) degeneration. This is a multifactorial disease induced by genetic and environmental factors and that progresses with aging. Disc degeneration is characterized by a limited ability of IVD cells to produce functional matrix while producing abnormal amounts of matrix-degrading enzymes. The prolonged imbalance between anabolism and catabolism in degenerative discs alters their composition and hydration. In turn, this results in increased angiogenesis and the loss of the disc's ability to maintain its aneural condition. Inflammation in the IVD, in particular the presence of pro-inflammatory cytokines, was found to favor innervation and also sensitization of the nociceptive pathways, thereby exacerbating degenerative symptoms. In this review, we discuss anti-inflammatory approaches to encounter disc catabolism, potential treatments to lower discogenic pain and pro-anabolic approaches in the form of protein delivery, gene therapy and cell delivery, to trigger regeneration in the IVD.

MicroRNA-93 regulates collagen loss by targeting MMP3 in human nucleus pulposus cells

OBJECTIVES

Degenerated disc disease is one of the most common medical conditions in patients suffering from low back pain. Recent studies have shown that microRNAs can regulate cell function in many pathological conditions. The aim of this study was to investigate expression and role of miR-93 in disc degeneration.

MATERIALS AND METHODS

Quantitative RT-PCR was employed to investigate level of miR-93 in degenerative nucleus pulposus (NP) tissues. Then, functional analysis of miR-93 in regulating collagen II expression was performed. Subsequently, western blotting and luciferase reporter assay were used to detect the target gene.

RESULTS

We showed that miR-93 was significantly down-regulated in degenerative NP tissues and its levels were associated with grade of disc degeneration. Overexpression of miR-93 stimulated type II collagen expression in NP cells. Moreover, MMP3 was identified as a putative target of miR-93. MiR-93 inhibited MMP3 expression by directly targeting its 3'UTR, and this was abolished by miR-93 binding site mutations. Additionally, restoration of MMP3 in miR-93-overexpressed NP cells reversed effects of type II collagen expression. Expression of MMP3 inversely correlated with miR-93 expression in degenerative NP tissues.

CONCLUSIONS

Taken together, we demonstrated that miR-93 contributed to abnormal NP cell type II collagen expression by targeting MMP3, involved in intervertebral disc degeneration.

MicroRNA in intervertebral disc degeneration

Aetiology of intervertebral disc degeneration (IDD) is complex, with genetic, developmental, biochemical and biomechanical factors contributing to the disease process. It is becoming obvious that epigenetic processes influence evolution of IDD as strongly as the genetic background. Deregulated phenotypes of nucleus pulposus cells, including differentiation, migration, proliferation and apoptosis, are involved in all stages of progression of human IDD. Non-coding RNAs, including microRNAs, have recently been recognized as important regulators of gene expression. Research into roles of microRNAs in IDD has been very active over the past 5 years. Our review summarizes current research enlightenment towards understanding roles of microRNAs in regulating nucleus pulposus cell functions in IDD. These exciting findings support the notion that specific modulation of microRNAs may represent an attractive approach for management of IDD.

Investigating conversion of endplate chondrocytes induced by intermittent cyclic mechanical unconfined compression in three-dimensional cultures

Mechanical stimulation is known to regulate the calcification of endplate chondrocytes. The Ank protein has a strong influence on anti-calcification by transports intracellular inorganic pyrophosphate (PPi) to the extracellular matrix. It is known that TGF-β1 is able to induce Ank gene expression and protect chondrocyte calcification. Intermittent cyclic mechanical tension (ICMT) could induce calcification of endplate chondrocytes by decrease the expression of Ank gene. In this study, we investigated the relation of intermittent cyclic mechanical unconfined compression (ICMC) and Ank gene expression. We found that ICMC decreased the Ank gene expression in the endplate chondrocytes, and there was an decreased in the TGF-β1 expression after ICMC stimulation. The Ank gene expression significantly increased when treated by transforming growth factor alpha 1 (TGF-β1) in a dose-dependent manner and decreased when treated by SB431542 (ALK inhibitor) in a dose-dependent manner. Our results implicate that ICMC-induced downregulation of Ank gene expression may be regulated by TGF-β1 in end-plate chondrocytes.

Extra-virgin olive oil diet and mild physical activity prevent cartilage degeneration in an osteoarthritis model: an in vivo and in vitro study on lubricin expression

Mediterranean diet includes a relatively high fat consumption mostly from monounsaturated fatty acids mainly provided by olive oil, the principal source of culinary and dressing fat. The beneficial effects of olive oil have been widely studied and could be due to its phytochemicals, which have been shown to possess anti-inflammatory properties. Lubricin is a chondroprotective glycoprotein and it serves as a critical boundary lubricant between opposing cartilage surfaces. A joint injury causes an initial flare of cytokines, which decreases lubricin expression and predisposes to cartilage degeneration such as osteoarthritis. The aim of this study was to evaluate the role of extra-virgin olive oil diet and physical activity on inflammation and expression of lubricin in articular cartilage of rats after injury. In this study we used histomorphometric, histological, immunocytochemical, immunohistochemical, western blot and biochemical analysis for lubricin and interleukin-1 evaluations in the cartilage and in the synovial fluid. We report the beneficial effect of physical activity (treadmill training) and extra-virgin olive oil supplementation, on the articular cartilage. The effects of anterior cruciate ligament transection decrease drastically the expression of lubricin and increase the expression of interleukin-1 in rats, while after physical activity and extra-virgin olive oil supplemented diet, the values return to a normal level compared to the control group. With our results we can confirm the importance of the physical activity in conjunction with extra-virgin olive oil diet in medical therapy to prevent osteoarthritis disease in order to preserve the articular cartilage and then the entire joint.

Migration inhibitory factor enhances inflammation via CD74 in cartilage end plates with Modic type 1 changes on MRI

BACKGROUND

Type 1 Modic changes are characterized by edema, vascularization, and inflammation, which lead to intervertebral disc degeneration. Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine closely related to the inflammatory cytokines detected in degenerative intervertebral disc tissues. However, the existence and role of MIF and its receptor CD74 in intervertebral disc degeneration have not been elucidated.

QUESTIONS/PURPOSES

We asked whether (1) MIF and its receptor CD74 are expressed in cartilage end plates with Type 1 Modic changes, (2) MIF is associated with cartilage end plate degeneration, (3) the MIF antagonist (S, R)-3(4-hydroxyphenyl)-4, 5-dihydro-5-isoxazole acetic acid methyl ester (ISO-1) suppresses MIF-induced inflammatory cytokine release, and (4) inflammatory cytokines are released by cartilage end plate chondrocytes via CD74 by activating the CD74 antibody (CD74Ab).

METHODS

We examined MIF and CD74 expression by human cartilage end plate chondrocytes and tissues with Type 1 Modic changes from eight patients using immunocytofluorescence and immunohistochemistry. MIF production by the chondrocytes was assessed by ELISA and PCR. We compared cytokine release by chondrocytes treated with MIF in the presence or absence of exogenous ISO-1 by ELISA. Cytokine release by chondrocytes after treatment with CD74Ab was determined by ELISA.

RESULTS

MIF was expressed in degenerated human cartilage end plate tissues and chondrocytes. Lipopolysaccharide and tumor necrosis factor α (TNF-α) upregulated MIF expression and increased MIF secretion in chondrocytes in a dose-dependent manner. MIF increased the secretion of IL-6, IL-8, and prostaglandin E2 (PGE2) in a dose-dependent manner. ISO-1 reduced the secretion of IL-6, IL-8, and PGE2. CD74Ab activated CD74 and induced release of inflammatory cytokines.

CONCLUSIONS

Chondrocytes in cartilage end plate with Type 1 Modic changes express MIF and its receptor CD74. MIF might promote the inflammatory response through CD74. MIF-induced cytokine release appears to be suppressed by ISO-1, and CD74Ab could induce cytokine release.

CLINICAL RELEVANCE

The MIF/CD74 pathway may represent a crucial target for treating disc degeneration since inhibiting the function of MIF with its antagonist ISO-1 can reduce MIF-induced inflammation and exert potent therapeutic effects.

Histochemistry as a unique approach for investigating normal and osteoarthritic cartilage

In this review article, we describe benefits and disadvantages of the established histochemical methods for studying articular cartilage tissue under normal, pathological and experimental conditions. We illustrate the current knowledge on cartilage tissue based on histological and immunohistochemical aspects, and in conclusion we provide a short overview on the degeneration of cartilage, such as osteoarthritis. Adult articular cartilage has low capacity to repair itself, and thus even minor injuries may lead to progressive damage and osteoarthritic joint degeneration, resulting in significant pain and disability. Numerous efforts have been made to implement the knowledge in the study of cartilage in the last years, and histochemistry proved to be an especially powerful tool to this aim.

Platelet-rich plasma induces annulus fibrosus cell proliferation and matrix production

PURPOSE

Platelet-rich plasma (PRP) contains growth factors and creates a 3D structure upon clotting; PRP or platelet lysate (PL) might be considered for annulus fibrosus (AF) repair.

METHODS

Bovine AF cells were cultured with 25% PRP, 50% PRP, 25% PL, 50% PL, or 10% FBS. After 2 and 4 days, DNA, glycosaminoglycan (GAG), and mRNA levels were analyzed. Histology was performed after injection of PRP into an AF defect in a whole disc ex vivo.

RESULTS

By day 4, significant increases in DNA content were observed in all treatment groups. All groups also showed elevated GAG synthesis, with highest amounts at 50% PL. Collagen I and II expression was similar between groups; aggrecan, decorin, and versican expression was highest at 25% PL. Injection of PRP into the AF defect resulted in an increased matrix synthesis.

CONCLUSIONS

Platelet-rich preparations increased the matrix production and cell number and may therefore be considered to promote AF repair.

Degenerative grade affects the responses of human nucleus pulposus cells to link-N, CTGF, and TGFβ3

STUDY DESIGN

Cells isolated from moderately and severely degenerated human intervertebral disks (IVDs) cultured in an alginate scaffold.

OBJECTIVE

To compare the regenerative potential of moderately versus severely degenerated cells using 3 proanabolic stimulants.

SUMMARY OF BACKGROUND DATA

Injection of soluble cell signaling factors has potential to slow the progression of IVD degeneration. Although degenerative grade is thought to be an important factor in targeting therapeutic interventions it remains unknown whether cells in severely degenerated IVDs have impaired metabolic functions compared to lesser degenerative levels or if they are primarily influenced by the altered microenvironment.

METHODS

Nucleus pulposus (NP) cells were cultured in alginate for 21 days and treated with 3 different proanabolic stimulants: a growth factor/anti-inflammatory combination of transforming growth factor β3 (TGFβ3)+dexamethasone (Dex), or matricellular proteins connective tissue growth factor (CTGF) or Link-N. They were assayed for metabolic activity, DNA content, glycosaminoglycan, and qRT-PCR gene profiling.

RESULTS

Moderately degenerated cells responded to stimulation with increased proliferation, decreased IL-1β, MMP9, and COL1A1 expression, and upregulated HAS1 as compared with severely degenerated cells. TGFβR1 (ALK5) receptors were expressed at greater levels in moderately than severely degenerated cells. TGFβ3+Dex had a notable stimulatory effect on moderately degenerated NP cells with increased anabolic gene expression and decreased COL1A1 and ADAMTS5 gene expression. Link-N and CTGF had similar responses in all assays, and both treatments upregulated IL-1β expression and had a more catabolic response than TGFβ3+Dex, particularly in the more severely degenerated group. All groups, including different degenerative grades, produced similar amounts of glycosaminoglycan.

CONCLUSIONS

Proanabolic stimulants alone had limited capacity to overcome the catabolic and proinflammatory cytokine expression of severely degenerated NP cells and likely require additional anti-inflammatory treatments. Moderately degenerated NP cells had greater TGFβ receptor 1 expression and better responded to anabolic stimulation.

Post-traumatic caspase-3 expression in the adjacent areas of growth plate injury site: a morphological study

The epiphyseal plate is a hyaline cartilage plate that sits between the diaphysis and the epiphysis. The objective of this study was to determine the impact of an injury in the growth plate chondrocytes through the study of histological morphology, immunohistochemistry, histomorphometry and Western Blot analyses of the caspase-3 and cleaved PARP-1, and levels of the inflammatory cytokines, Interleukin-6 (IL-6) and Tumor Necrosis Factor alpha (TNF-α), in order to acquire more information about post-injury reactions of physeal cell turnover. In our results, morphological analysis showed that in experimental bones, neo-formed bone trabeculae-resulting from bone formation repair-invaded the growth plate and reached the metaphyseal bone tissue (bone bridge), and this could result in some growth arrest. We demonstrated, by ELISA, increased expression levels of the inflammatory cytokines IL-6 and TNF-α. Immunohistochemistry, histomorphometry and Western Blot analyses of the caspase-3 and cleaved PARP-1 showed that the physeal apoptosis rate of the experimental bones was significantly higher than that of the control ones. In conclusion, we could assume that the inflammation process causes stress to chondrocytes that will die as a biological defense mechanism, and will also increase the survival of new chondrocytes for maintaining cell homeostasis. Nevertheless, the exact stimulus leading to the increased apoptosis rate, observed after injury, needs additional research to understand the possible contribution of chondrocyte apoptosis to growth disturbance.