Expression and role of connective tissue growth factor in painful disc fibrosis and degeneration

Efficacy and safety of allogeneic mesenchymal precursor cells with and without hyaluronic acid for treatment of chronic low back pain: A prospective, randomized, double blind, concurrent-controlled 36-month study

BACKGROUND CONTEXT

Low back pain (LBP) associated with degenerative disc disease (DDD) is a serious condition resulting in significant morbidity, disability, and reduced quality of life for millions of people each year. Patients who fail to improve with conservative/noninvasive treatments including physical therapy and nonopioid analgesic medications have limited options, which include opioid analgesics with their associated significant risks; epidural steroid injections with limited supporting evidence; or surgical interventions such as spine fusion or artificial disc replacement. A safe, minimally invasive, nonopioid treatment that provides prolonged improvement in pain, function, and quality of life is needed for such patients.

PURPOSE

Evaluate the efficacy and safety of a single injection of mesenchymal precursor cells (MPCs) with or without hyaluronic acid (HA) compared to an intradiscal saline injection through 36 months follow-up in subjects with chronic low back pain (CLBP) associated with moderate DDD (mDDD).

STUDY DESIGN/SETTING

A prospective, multicenter, randomized, double-blind, concurrent-controlled study conducted at 49 clinical sites.

SUBJECT SAMPLE

A total of 404 subjects with CLBP associated with mDDD at one level from L1 to S1 received MPCs without HA (MPC), MPCs with HA (MPC+HA), or saline control (control) treatment.

OUTCOME MEASURES

Subjects were clinically and radiographically evaluated at 1, 3, 6, 12, 18, 24, and 36 months postinjection. Clinical evaluation included adverse events, neurologic evaluation, laboratory tests, LBP intensity measured by Visual Analog Scale (VAS), Oswestry Disability Index (ODI) and EQ-5D-5L Index. Radiographic assessments used Magnetic Resonance (MR) imaging and X-ray imaging studies.

METHODS

The primary efficacy endpoint was a composite responder analysis for overall treatment success at both 12 and 24 months that was comprised of:[1] at least a 50% reduction from baseline in low back pain VAS score (average pain over 24 h);[2] at least a 15-point decrease from baseline in ODI score; and[3] no adjudicated posttreatment interventions at the treated level. To assess superiority, a Bayesian analysis used a probability threshold of 0.9875. Additional analyses were performed on a prespecified subpopulation of subjects with CLBP duration at baseline less than the median baseline duration of 68 months (CLBPLTM). Statistical assessments included least squares (LS) mean, LS mean change from baseline (CFB) using the mixed model for repeated measures (MMRM) and categorical responder analyses using stratified Cochran Mantel Haenszel row means score test with p<.05 defined as statistically significant. This study was conducted under a US Food and Drug Administration (FDA) Investigational New Drug (IND) application sponsored and funded by Mesoblast.

RESULTS

All treatment groups showed substantial improvement from baseline in LS Mean LBP and ODI. The primary efficacy endpoint for the trial did not reach significance for either treatment group compared to control in all subjects. Furthermore, none of the secondary endpoints showed a significant difference between treatment and control in all subjects. While the primary and secondary responder efficacy endpoints were not reached, MPC+HA significantly reduced LS mean LBP compared to control at 12 and 24 months in all subjects. The results observed in all subjects were enhanced for MPC+HA and MPC in the prespecified CLBPLTM subgroup with MPC+HA having significantly greater reduction in LBP at all time points compared to control and MPC having significantly greater reduction in LBP at 6, 12 and 36 months. In the CLBPLTM subgroup, MPC+HA also showed significantly greater proportion of pain responders at 12, 24 and 36 compared to control. MPC+HA also showed significantly greater function improvement at 12 and 18 months compared to control in the CLBPLTM subgroup. Furthermore, MPC+HA subjects in the CLBPLTM subgroup showed significantly greater improvement in quality of life (QOL) compared to control at 12, 24 and 36 months. MPC+HA baseline opioid users had greater reduction in daily average morphine equivalent dose (MED) compared to control at 6 through 36 months. Furthermore, significantly more MPC+HA baseline opioid users (27.8%) were not taking opioids at 36 months compared to (7.8%) control. The injection procedure and MPC treatment were well tolerated with no appreciable differences in Treatment Emergent Adverse Events (TEAEs). No Serious Adverse Events (SAEs) were related to the treatment or procedure. The number of subjects that received posttreatment interventions (PTI) at the treated level were comparable among groups.

CONCLUSIONS

While the primary and secondary efficacy endpoints were not met in all subjects, MPC+HA treatment showed a significant reduction in pain compared to control that was enhanced in subjects with CLBP duration less than 68 months. Intra-discal injection of MPC+HA is a minimally invasive nonopioid therapy that appears to be safe and demonstrates reduction in pain through 24 months compared to control with enhanced results in subjects with mDDD that have had CLBP less than 68 months.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Identifying the protective effects of miR-874-3p/ATF3 axis in intervertebral disc degeneration by single-cell RNA sequencing and validation

Intervertebral disc degeneration (IVDD) severely affects the work and the quality of life of people. We previously demonstrated that silencing activation transcription factor 3 (ATF3) blocked the IVDD pathological process by regulating nucleus pulposus cell (NPC) ferroptosis, apoptosis, inflammation, and extracellular matrix (ECM) metabolism. Nevertheless, whether miR-874-3p mediated the IVDD pathological process by targeting ATF3 remains unclear. We performed single-cell RNA sequencing (scRNA-seq) and bioinformatics analysis to identify ATF3 as a key ferroptosis gene in IVDD. Then, Western blotting, flow cytometry, ELISA, and animal experiments were performed to validate the roles and regulatory mechanisms of miR-874-3p/ATF3 signalling axis in IVDD. ATF3 was highly expressed in IVDD patients and multiple cell types of IVDD rat, as revealed by scRNA-seq and bioinformatics analysis. GO analysis unveiled the involvement of ATF3 in regulating cell apoptosis and ECM metabolism. Furthermore, we verified that miR-874-3p might protect against IVDD by inhibiting NPC ferroptosis, apoptosis, ECM degradation, and inflammatory response by targeting ATF3. In vivo experiments displayed the protective effect of miR-874-3p/ATF3 axis on IVDD. These findings propose the potential of miR-874-3p and ATF3 as biomarkers of IVDD and suggest that targeting the miR-874-3p/ATF3 axis may be a therapeutic target for IVDD.

Roles of Chemokines in Intervertebral Disk Degeneration

PURPOSE OF REVIEW

Intervertebral disc degeneration is the primary etiology of low back pain and radicular pain. This review examines the roles of crucial chemokines in different stages of degenerative disc disease, along with interventions targeting chemokine function to mitigate disc degeneration.

RECENT FINDINGS

The release of chemokines from degenerated discs facilitates the infiltration and activation of immune cells, thereby intensifying the inflammatory cascade response. The migration of immune cells into the venous lumen is concomitant with the emergence of microvascular tissue and nerve fibers. Furthermore, the presence of neurogenic factors secreted by disc cells and immune cells stimulates the activation of pain-related cation channels in the dorsal root ganglion, potentially exacerbating discogenic and neurogenic pain and intensifying the degenerative cascade response mediated by chemokines. Gaining a deeper comprehension of the functions of chemokines and immune cells in these processes involving catabolism, angiogenesis, and injury detection could offer novel therapeutic avenues for managing symptomatic disc disease.

Does vertebral osteoporosis delay or accelerate lumbar disc degeneration? A systematic review

The effect of vertebral osteoporosis on disc degeneration is still debated. The purpose of this study was to provide a systematic review of studies in this area to further reveal the relationship between the two. Relevant studies were searched in electronic databases, and studies were screened according to inclusion and exclusion criteria, and finally, basic information of the included studies was extracted and summarized. This study was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. A total of 34 publications spanning 24 years were included in our study. There were 19 clinical studies, including 12 prospective studies and 7 retrospective studies. Of these, 7 considered vertebral osteoporosis to be positively correlated with disc degeneration, 8 considered them to be negatively correlated, and 4 considered them to be uncorrelated. Two cadaveric studies were included, one considered the two to be negatively correlated and one considered them not to be correlated. Seven animal studies were included, of which five considered a positive correlation between vertebral osteoporosis and disc degeneration and two considered a negative correlation between the two. There were also 6 studies that used anti-osteoporosis drugs for intervention, all of them were animal studies. Five of them concluded that vertebral osteoporosis was positively associated with disc degeneration, and the remaining one concluded that there was no correlation between the two. Our systematic review shows that the majority of studies currently consider an association between vertebral osteoporosis and disc degeneration, but there is still a huge disagreement whether this association is positive or negative. Differences in observation time and follow-up time may be one of the reasons for the disagreement. A large number of clinical and basic studies are still needed in the future to further explore the relationship between the two.

Ccn2a-FGFR1-SHH signaling is necessary for intervertebral disc homeostasis and regeneration in adult zebrafish

Intervertebral disc (IVD) degeneration is the primary cause of back pain in humans. However, the cellular and molecular pathogenesis of IVD degeneration is poorly understood. This study shows that zebrafish IVDs possess distinct and non-overlapping zones of cell proliferation and cell death. We find that, in zebrafish, cellular communication network factor 2a (ccn2a) is expressed in notochord and IVDs. Although IVD development appears normal in ccn2a mutants, the adult mutant IVDs exhibit decreased cell proliferation and increased cell death leading to IVD degeneration. Moreover, Ccn2a overexpression promotes regeneration through accelerating cell proliferation and suppressing cell death in wild-type aged IVDs. Mechanistically, Ccn2a maintains IVD homeostasis and promotes IVD regeneration by enhancing outer annulus fibrosus cell proliferation and suppressing nucleus pulposus cell death through augmenting FGFR1-SHH signaling. These findings reveal that Ccn2a plays a central role in IVD homeostasis and regeneration, which could be exploited for therapeutic intervention in degenerated human discs.

Current Perspectives on Nucleus Pulposus Fibrosis in Disc Degeneration and Repair

A growing body of evidence in humans and animal models indicates an association between intervertebral disc degeneration (IDD) and increased fibrotic elements in the nucleus pulposus (NP). These include enhanced matrix turnover along with the abnormal deposition of collagens and other fibrous matrices, the emergence of fibrosis effector cells, such as macrophages and active fibroblasts, and the upregulation of the fibroinflammatory factors TGF-β1 and IL-1/-13. Studies have suggested a role for NP cells in fibroblastic differentiation through the TGF-βR1-Smad2/3 pathway, inflammatory activation and mechanosensing machineries. Moreover, NP fibrosis is linked to abnormal MMP activity, consistent with the role of matrix proteases in regulating tissue fibrosis. MMP-2 and MMP-12 are the two main profibrogenic markers of myofibroblastic NP cells. This review revisits studies in the literature relevant to NP fibrosis in an attempt to stratify its biochemical features and the molecular identity of fibroblastic cells in the context of IDD. Given the role of fibrosis in tissue healing and diseases, the perspective may provide new insights into the pathomechanism of IDD and its management.

Fibroblasts: the neglected cell type in peripheral sensitisation and chronic pain? A review based on a systematic search of the literature

Chronic pain and its underlying biological mechanisms have been studied for many decades, with a myriad of molecules, receptors and cell types known to contribute to abnormal pain sensations. Besides an obvious role for neurons, immune cells like microglia, macrophages and T cells are also important drivers of persistent pain. While neuroinflammation has therefore been widely studied in pain research, there is one cell type that appears to be rather neglected in this context: the humble fibroblast. Fibroblasts may seem unassuming but actually play a major part in regulating immune cell function and driving chronic inflammation. Here, our aim was to determine the breadth and quality of research that implicates fibroblasts in chronic pain conditions and models.

OBJECTIVES

We set out to analyse the current literature on this topic-using systematic screening and data extraction methods to obtain a balanced view on what has been published.

METHODS

We categorised the articles we included-stratifying them according to what was investigated, the estimated quality of results and any common conclusions.

RESULTS

We found that there has been surprisingly little research in this area: 134 articles met our inclusion criteria, only a tiny minority of which directly investigated interactions between fibroblasts and peripheral neurons.

CONCLUSIONS

Fibroblasts are a ubiquitous cell type and a prominent source of many proalgesic mediators in a wide variety of tissues. We think that they deserve a more central role in pain research and propose a new, testable model of how fibroblasts might drive peripheral neuron sensitisation.

Inhibition of RhoA/MRTF-A signaling alleviates nucleus pulposus fibrosis induced by mechanical stress overload

PURPOSE/AIM

: Intervertebral disc degeneration (IDD) is the leading cause of lower back pain, and clinically useful drugs for IDD are unavailable. Mechanical stress overload-induced fibrosis plays a critical role in IDD. RhoA/MRTF-A signaling is known to regulate tissue fibrosis; however, the effect of RhoA/MRTF-A on the development of IDD is unclear.

MATERIALS AND METHODS

: The expression of aggrecan, collagen I, collagen II, MMP-12, CTGF, and MRTF-A in nucleus pulposus (NP) samples from IDD patients and controls was detected by immunohistochemical staining. Primary nucleus pulposus cells (NPCs) were isolated and cultured to establish an overload strain model treated with or without CCG-1423. The protein levels of RhoA, ROCK2, MRTF-A, CTGF, and MMP-12 as well as fibrosis-associated proteins were detected by western blotting and immunofluorescence.

RESULTS

: Collagen I, MMP-12, and CTGF were significantly upregulated, and aggrecan and collagen II were significantly downregulated in the IDD samples. The cellular localization of MRTF-A was associated with intervertebral disc (IVD) degeneration. Overloaded strain enhanced the nuclear translocation of MRTF-A and changed the NPC morphology from spindle-shaped to long strips. Additional experiments showed that RhoA, ROCK2, MRTF-A, SRF, MMP-12, and CTGF were upregulated; however, aggrecan and collagen II were downregulated in NPCs under overload strain. CCG-1423, a RhoA/MRTF-A pathway inhibitor, reversed strain-induced fibrosis.

CONCLUSION

: Mechanical stress activates RhoA/MRTF-A signaling to promote extracellular matrix (ECM) degeneration in the NP, which is associated with the development of IDD. Our findings suggest that the RhoA/MRTF-A inhibitor CCG-1423 can alleviate NPC degeneration caused by overload stress and has potential as a therapeutic agent for IDD.

Ferroptosis: A potential target for the intervention of intervertebral disc degeneration

Ferroptosis, an iron-dependent form of programmed cell death marked by phospholipid peroxidation, is regulated by complex cellular metabolic pathways including lipid metabolism, iron balance, redox homeostasis, and mitochondrial activity. Initial research regarding the mechanism of ferroptosis mainly focused on the solute carrier family 7 member 11/glutathione/glutathione peroxidase 4 (GPX4) signal pathway. Recently, novel mechanisms of ferroptosis, independent of GPX4, have been discovered. Numerous pathologies associated with extensive lipid peroxidation, such as drug-resistant cancers, ischemic organ injuries, and neurodegenerative diseases, are driven by ferroptosis. Ferroptosis is a new therapeutic target for the intervention of IVDD. The role of ferroptosis in the modulation of intervertebral disc degeneration (IVDD) is a significant topic of interest. This is a novel research topic, and research on the mechanisms of IVDD and ferroptosis is ongoing. Herein, we aim to review and discuss the literature to explore the mechanisms of ferroptosis, the relationship between IVDD and ferroptosis, and the regulatory networks in the cells of the nucleus pulposus, annulus fibrosus, and cartilage endplate to provide references for future basic research and clinical translation for IVDD treatment.

Single-cell RNA-seq analysis identifies unique chondrocyte subsets and reveals involvement of ferroptosis in human intervertebral disc degeneration

OBJECTIVE

Nucleus pulposus (NP) plays a central role in disc degeneration pathogenesis, however, as a heterogeneous tissue, cell subsets in NP and their corresponding biological process in intervertebral disc degeneration (IVDD) are unreported.

METHOD

Nucleus pulposus were isolated from normal control and IVDD, and then subjected to single-cell RNA sequencing (scRNA-seq). Unsupervised clustering of the cells based on the gene expression profiles using the Seurat package and passed to tSNE for clustering visualization. Rat model of disc degeneration was built to validate the pathways identified by scRNA-Seq.

RESULTS

Seven chondrocyte subsets were revealed in NP based on differential gene expression, among which 4 subsets (C1-C4) were reported for the first time. Furthermore, GO and KEGG analyses discovered that ferroptosis pathways were enriched. Rat model of disc degeneration was built (n = 6/group, control vs. model) to validate the pathways identified by scRNA-Seq. Iron levels of NP were significantly higher in model group than control group (means 0.712 vs. 0.248, respectively, mg/gpro, p = 0.0026), and the levels of Heme Oxygenase 1 (HO-1) were also elevated in model group (means 14.33 vs. 5.16 IOD, respectively, p = 0.0002). However, the levels of ferritin light chain (FTL) were significantly decreased in model group compared to control group (means 26.17 vs. 9.00 FTL⁺ cell number, respectively, p = 0.0011).

CONCLUSIONS

Novel chondrocyte subsets in nucleus pulposus were discovered through scRNA-Seq, which provided novel insight to understand the pathological change during the development of IVDD. Ferroptosis participated in disc degeneration pathogenesis and it might serve as a new target for intervening IVDD.

The circular RNA circ-GRB10 participates in the molecular circuitry inhibiting human intervertebral disc degeneration

Intervertebral disc degeneration (IDD) is the most common degenerative disease all over the word. Our previous study confirmed that the downregulated circ-GRB10 directly interacts with miR-328-5p, which modulate ERBB2 and leads to the degeneration of intervertebral disc; however, the underpinning mechanism of circ-GRB10 dysregulation remains unclear. We identified that FUS and demonstrated that circ-GBR10 biosynthesis in nucleus pulposus (NP) cells was promoted by FUS, whose expression was controlled by miR-141-3p. In addition, ERBB2 downregulation led to decreased Erk1/2 phosphorylation which enhanced miR-141-3p production in NP cells. In vivo data indicated that circ-GRB10 inhibited IDD in rat model. The present study revealed that miR-141-3p and FUS are key factors that regulate circ-GRB10 synthesis in NP cells. In addition, circ-GBR10 participates in the molecular circuitry that controls human IDD development. These findings provide a basis for further functional, diagnostic and therapeutic studies of circ-GRB10 in IDD.

Optimization of a rat lumbar IVD degeneration model for low back pain

INTRODUCTION

Intervertebral disc (IVD) degeneration is often associated with low back pain and radiating leg pain. The purpose of this study is to develop a reproducible and standardized preclinical model of painful lumbar IVD degeneration by evaluation of structural and behavioral changes in response to IVD injury with increasing needle sizes. This model can be used to develop new therapies for IVD degeneration.

METHODS

Forty-five female Sprague Dawley rats underwent anterior lumbar disc needle puncture at levels L4-5 and L5-6 under fluoroscopic guidance. Animals were randomly assigned to four different experimental groups: needle sizes of 18 Gauge (G), 21G, 23G, and sham control. To monitor the progression of IVD degeneration and pain, the following methods were employed: μMRI, qRT-PCR, histology, and biobehavioral analysis.

RESULTS

T1- and T2-weighted μMRI analysis showed a correlation between the degree of IVD degeneration and needle diameter, with the most severe degeneration in the 18G group. mRNA expression of markers for IVD degeneration markers were dysregulated in the 18G and 21G groups, while pro-nociceptive markers were increased in the 18G group only. Hematoxylin and Eosin (H&E) and Alcian Blue/Picrosirius Red staining confirmed the most pronounced IVD degeneration in the 18G group. Randall-Selitto and von Frey tests showed increased hindpaw sensitivity in the 18G group.

CONCLUSION

Our findings demonstrate that anterior disc injury with an 18G needle creates severe IVD degeneration and mechanical hypersensitivity, while the 21G needle results in moderate degeneration with no increased pain sensitivity. Therefore, needle sizes should be selected depending on the desired phenotype for the pre-clinical model.

Mechanosensitive transcriptional coactivators MRTF-A and YAP/TAZ regulate nucleus pulposus cell phenotype through cell shape

Cells of the adult nucleus pulposus (NP) are critically important in maintaining overall disc health and function. NP cells reside in a soft, gelatinous matrix that dehydrates and becomes increasingly fibrotic with age. Such changes result in physical cues of matrix stiffness that may be potent regulators of NP cell phenotype and may contribute to a transition toward a senescent and fibroblastic NP cell with a limited capacity for repair. Here, we investigate the mechanosignaling cues generated from changes in matrix stiffness in directing NP cell phenotype and identify mechanisms that can potentially preserve a biosynthetically active, juvenile NP cell phenotype. Using a laminin-functionalized polyethylene glycol hydrogel, we show that when NP cells form rounded, multicell clusters, they are able to maintain cytosolic localization of myocardin-related transcription factor (MRTF)-A, a coactivator of serum-response factor (SRF), known to promote fibroblast-like behaviors in many cells. Upon preservation of a rounded shape, human NP cells similarly showed cytosolic retention of transcriptional coactivator Yes-associated protein (YAP) and its paralogue PDZ-binding motif (TAZ) with associated decline in activation of its transcription factor TEA domain family member-binding domain (TEAD). When changes in cell shape occur, leading to a more spread, fibrotic morphology associated with stronger F-actin alignment, SRF and TEAD are up-regulated. However, targeted deletion of either cofactor was not sufficient to overcome shape-mediated changes observed in transcriptional activation of SRF or TEAD. Findings show that substrate stiffness-induced promotion of F-actin alignment occurs concomitantly with a flattened, spread morphology, decreased NP marker expression, and reduced biosynthetic activity. This work indicates cell shape is a stronger indicator of SRF and TEAD mechanosignaling pathways than coactivators MRTF-A and YAP/TAZ, respectively, and may play a role in the degeneration-associated loss of NP cellularity and phenotype.-Fearing, B. V., Jing, L., Barcellona, M. N., Witte, S. E., Buchowski, J. M., Zebala, L. P., Kelly, M. P., Luhmann, S., Gupta, M. C., Pathak, A., Setton, L. A. Mechanosensitive transcriptional coactivators MRTF-A and YAP/TAZ regulate nucleus pulposus cell phenotype through cell shape.

Stem Cell Therapies for Treatment of Discogenic Low Back Pain: a Comprehensive Review

PURPOSE OF REVIEW

Discogenic low back pain (DLBP) stems from pathology in one or more intervertebral discs identified as the root cause of the pain. It is the most common type of chronic low back pain (LBP), representing 26-42% of attributable cases.

RECENT FINDINGS

The clinical presentation of DLBP includes increased pain when sitting, coughing, or sneezing, and experiencing relief when standing or ambulating. Dermatomal radiation of pain to the lower extremity and neurological symptoms including numbness, motor weakness, and urinary or fecal incontinence are signs of advanced disease with disc prolapse, nerve root compression, or spinal stenosis. Degenerative disc disease is caused by both a decrease in disc nutrient supply causing decreased oxygen, lowered pH, and lessened ability of the intervertebral disc (IVD) to respond to increased load or injury; moreover, changes in the extracellular matrix composition cause weakening of the tissue and skewing the extracellular matrix's (ECM) harmonious balance between catabolic and anabolic factors for cell turnover in favor of catabolism. Thus, the degeneration of the disc causes a shift from type II to type I collagen expression by NP cells and a decrease in aggrecan synthesis leads to dehydrated matrix cells ultimately with loss of swelling pressure needed for mechanical support. Cell-based therapies such as autologous nucleus pulposus cell re-implantation have in animal models and human trials shown improvements in LBP score, retention of hydration in IVD, and increased disc height. Percutaneously delivered multipotent mesenchymal stem cell (MSC) therapy has been proposed as a potential means to uniquely ameliorate discogenic LBP holistically through three mechanisms: mitigation of primary nociceptive disc pain, slow or reversal of the catabolic metabolism, and restoration of disc tissue. Embryonic stem cells (ESCs) can differentiate into cells of all three germ layers in vitro, but their use is hindered related to ethical concerns, potential for immune rejection after transplantation, disease, and teratoma formation. Another similar approach to treating back pain is transplantation of the nucleus pulposus, which, like stem cell therapy, seeks to address the underlying cause of intervertebral disc degeneration by aiming to reverse the destructive inflammatory process and regenerate the proteoglycans and collagen found in healthy disc tissue. Preliminary animal models and clinical studies have shown mesenchymal stem cell implantation as a potential therapy for IVD regeneration and ECM restoration via a shift towards favorable anabolic balance and reduction of pain.

Osmolarity and calcium regulate connective tissue growth factor (CTGF/CCN2) expression in nucleus pulposus cells

OBJECTIVE

The objective of our study was to verify the hypothesis that the expression of connective tissue growth factor (CTGF/CCN2), a key molecule essential for the maintenance of nucleus pulposus (NP) matrix homeostasis, is regulated by osmolarity and intracellular calcium in NP cells.

METHODS

Gene and protein expression levels of CCN2 were assessed using quantitative real-time PCR and western blot. Transfections and dual luciferase assays were performed to measure the effect of hyperosmolarity, tonicity enhancer binding protein (TonEBP) and Ca²⁺-calcineurin (Cn)-NFAT signaling on CCN2 promoter activity.

RESULTS

Cultured in hyperosmotic media, there was a significant decrease in the levels of CCN2 promoter activity, gene and protein expression in NP cells. The JASPAR database was used to analyze the construction of human CCN2 promoter, we found conserved TonE and NFAT binding sites. We then investigated whether TonEBP controlled CCN2 expression. Forced expression of TonEBP in NP cells showed that TonEBP negatively regulated CCN2 promoter activity, while suppression of TonEBP induced CCN2 promoter activity and expression. We then examined if Ca²⁺-Cn-NFAT signaling participated in the regulation of CCN2 expression. Co-expression of CCN2 reporter with individual NFAT1-4 expression plasmids and/or calcineurin A/B constructs suggested this signaling pathway played a role in the regulation of CCN2expression in NP cells.

CONCLUSIONS

Results of these studies illustrated that the expression of CCN2 in NP cells was regulated by the NFAT family through a signaling pathway network involving both activator (Ca²⁺-Cn-NFAT signaling) and suppressor (Hyperosmolarity-TonEBP) molecules.

SDF1/CXCR4 axis plays a role in angiogenesis during the degeneration of intervertebral discs

Low back pain (LBP) is a ubiquitous disease affecting quality of life. The ingrowth of new blood vessels is an important pathological feature of LBP, but its underlying mechanisms are poorly understood. The present study aimed to investigate the influence and relative mechanism of stromal cell derived factor 1 (SDF1) on the angiogenesis of degenerated intervertebral discs. The expression of SDF1 in nucleus pulposus cells (NPCs) was upregulated and downregulated by virus transfection, and the NPCs were allocated to either the downregulation (Down), degeneration (D) or upregulation (Up) group according to the expression of SDF1. The different groups of NPCs or NPC conditioned media were co-cultured with vascular endothelial cells (VECs) under different conditions. A Cell Counting Kit-8 (CCK-8) assay, a Transwell migration assay and a tube formation assay were conducted to evaluate the influence on angiogenesis. The results showed that SDF1 was significantly up- and downregulated in the Up and Down groups, respectively. Each group of NPCs or their conditioned medium was co-cultured with VECs; the CCK-8, Transwell migration and tube formation assays showed that cell viability, chemotactic migration and the tube formation ability of VECs increased with the rise in SDF1. The aforementioned results were significantly different between each group. After adding the CXCR4 inhibitor, AMD3100, the viability, migration and tube formation of VECs were suppressed in the D and Up groups, and there was a significant difference compared with the prior to the addition of the inhibitor, while there was a declining tendency in the Down group and no significant difference following addition of the inhibitor. The results demonstrated that SDF1 is expressed in human NPCs, and the SDF1/CXCR4 axis can influence the viability, migration and tube formation of VECs and may play an important role in the angiogenesis of human degenerated discs.

SDF1/CXCR7 Signaling Axis Participates in Angiogenesis in Degenerated Discs via the PI3K/AKT Pathway

Degenerative disc disease (DDD) is the main cause of low back pain, and the ingrowth of new blood vessels is one of its pathological features. The stromal cell-derived factor 1 (SDF1)/CXCR7 signaling axis plays a role in these physiological and pathological activities. The aims of this study were to explore whether this signaling axis participates in the angiogenesis of degenerated intervertebral discs (IVDs) and to define its underlying mechanism. In this study, we cocultured human nucleus pulposus cells (NPCs) and vascular endothelial cells (VECs) and regulated the expression of SDF1/CXCR7 to investigate the effect of VEC angiogenesis by NPCs. The results revealed that angiogenesis was enhanced with increased SDF1 and that angiogenesis was weakened with the inhibition of CXCR7. We found that PI3K/AKT was involved in the downstream pathway in the coculture. VEC angiogenesis induction by NPCs was enhanced with an increase in pAKT or a decrease in PTEN. We conclude that the SDF1/CXCR7 signaling axis plays a role in the angiogenesis of degenerated IVD through the PI3K/AKT pathway.

Preclinical development of a microRNA-based therapy for intervertebral disc degeneration

Understanding the molecular mechanisms regulating the maintenance and destruction of intervertebral disc may lead to the development of new therapies for intervertebral disc degeneration (IDD). Here we present evidence from miRNA microarray analyses of clinical data sets along with in vitro and in vivo experiments that miR-141 is a key regulator of IDD. Gain- and loss-of-function studies show that miR-141 drives IDD by inducing nucleus pulposus (NP) apoptosis. Furthermore, miR-141 KO in mice attenuated spontaneous and surgically induced IDD. Mechanistically, miR-141 promotes IDD development by targeting and depleting SIRT1, a negative regulator of NF-κB pathway. Therapeutically, upregulation or downregulation of miR-141 by nanoparticle delivery in IDD model aggravated or alleviated experimental IDD, respectively. Our findings reveal a novel mechanism by which miR-141, in part, promotes IDD progression by interacting with SIRT1/NF-κB pathway. Blockade of miR-141 in vivo may serve as a potential therapeutic approach in the treatment of IDD.

Intervertebral disk degeneration (IDD) is characterized by changes in the nucleus pulposus (NP) extra cellular matrix that compromise disk structural integrity. In a miRNA screen of human IDD patient NP tissue, the authors identify deregulated miR-141 and show that direct injection of nanoparticle-coupled miR-141 into the NP alleviates IDD in mice.

CCN family member 2/connective tissue growth factor (CCN2/CTGF) is regulated by Wnt-β-catenin signaling in nucleus pulposus cells

Background

The aims of this study were to investigate the gene expression of CCN family members in rat intervertebral disc (IVD) cells and to examine whether Wnt–β-catenin signaling regulates the expression of CCN family 2 (CCN2)/connective tissue growth factor (CTGF) in rat nucleus pulposus (NP) cells.

Methods

The gene expression of CCN family members were assessed in rat IVD cells using real-time reverse transcription polymerase chain reaction (RT-PCR). The expression pattern of CCN2 was also assessed in rat IVD cells using western blot and immunohistochemical analyses. Gain-of-function and loss-of-function experiments were performed to identify the mechanisms by which Wnt–β-catenin signaling influences the activity of the CCN2 promoter. To further determine if the mitogen-activated protein kinase (MAPK) pathway is required for the Wnt–β-catenin signaling-induced regulation of CCN2 expression in the NP cells, CCN2 expression was analyzed by reporter assay, RT-PCR and western blot analysis.

Results

CCN2 messenger RNA (mRNA) and protein were expressed in rat IVDs. Expression of CCN2 was significantly higher than for mRNA of other CCN family members in both rat NP and annulus fibrosus (AF) cells. The relative activity of the CCN2 promoter decreased 24 h after treatment with 6-bromoindirubin-3′-oxime (1.0 μM) (0.773 (95% 0.735, 0.812) P = 0.0077) in NP cells. In addition, treatment with the WT–β-catenin vector (500 ng) significantly decreased CCN2 promoter activity (0.688 (95% 0.535, 0.842) P = 0.0063), whereas β-catenin small interfering RNA (500 ng) significantly increased CCN2 promoter activity (1.775 (95% 1.435, 2.115) P < 0.001). Activation of Wnt–β-catenin signaling decreased the expression of CCN2 mRNA and protein by NP cells. Regulation of CCN2 by Wnt–β-catenin signaling involved the MAPK pathway in rat NP cells.

Conclusions

This study shows that Wnt–β-catenin signaling regulates the expression of CCN2 through the MAPK pathway in NP cells. Understanding the balance between Wnt–β-catenin signaling and CCN2 is necessary for developing therapeutic alternatives for the treatment of IVD degeneration.

Electronic supplementary material

The online version of this article (10.1186/s13075-018-1723-8) contains supplementary material, which is available to authorized users.

Association of IL10 and TGFB single nucleotide polymorphisms with intervertebral disc degeneration in Iranian population: a case control study

Background

Considered as one of the major causes of low back pain, Intervertebral disc degeneration (IVDD) is caused by several genetic and environmental factors. As inflammation plays an important role in disc degeneration, the genetic changes in both inflammatory and anti-inflammatory genes may play causative roles in IVDD as well. Therefore, the interactions between inflammatory and anti-inflammatory cytokines and also other components of disc matrix would determine the degree of tissue destruction in disc degeneration. However, there is still controversy regarding the exact role of inflammation and disc homeostasis imbalance in pathophysiology of IVDD. Therefore, current study was conducted to investigate the role of IL-10 and TGF-β single nucleotide polymorphisms (SNP) in Iranian IVDD patients.

Methods

Seventy-six IVDD patients and 140 healthy controls were enrolled in this study. Genomic DNA from peripheral leukocytes was tested for 3 SNPs in IL10 (L-10 -1082G/A (rs1800896), IL-10 -819C/T (rs1800871), IL-10 -592A/C (rs1800872)) and 2 SNPs in TGF-β (TGF-β Codon 10 C/T (rs1982037), and TGF-β Codon 25 C/T (rs1800471) genes through PCR-SSP method. The extracted genomic DNA was genotyped for the aforementioned SNPs of interest using specific primers, which were coated in the cytokines KITs and based on the PCR-SSP method for sequencing.

Results

The ‘T’ allele of IL-10 -819C/T and the ‘C’ allele of IL-10 -592A/C were more prevalent among patients, whereas the ‘C’ and ‘A’ alleles of respective SNPs were significantly more frequent in controls. The genotypes including ‘CT’ of IL-10 -819C/T, ‘CA’ of IL-10 -592A/C, and ‘GA’ of IL-10 -1082A/G were more common among patients, while the ‘CC’ genotype of both IL-10 -819C/T and IL-10 -592A/C SNPs were more frequent in controls. In addition, the IL-10 haplotypes including ‘ACC’, ‘ATA’, and ‘ACA’ were significantly associated with disease. Meanwhile, the ‘TC’ haplotype of TGF-β was more common among patients as well.

Conclusions

The IL-10 SNPs were significantly associated with IVDD in Iranian population; which proposes that genomic alterations of anti-inflammatory cytokines could lead to homeostasis imbalance in intervertebral discs and degenerative changes.

Injectable nanofibrous spongy microspheres for NR4A1 plasmid DNA transfection to reverse fibrotic degeneration and support disc regeneration

Safe and efficient gene therapy is highly desired for controlling pathogenic fibrosis of nucleus pulposus (NP) tissue, which would result in intervertebral disc (IVD) degeneration and disability if left untreated. In this work, a hyperbranched polymer (HP) with high plasmid DNA (pDNA) binding affinity and negligible cytotoxicity is synthesized, which can self-assemble into nano-sized polyplexes with a "double shell" structure that can transfect pDNA into NP cells with very high efficiency. These polyplexes are then encapsulated in biodegradable nanospheres (NS) to enable two-stage delivery: 1) temporally-controlled release of pDNA-carrying polyplexes and 2) highly efficient delivery of pDNA into cells by the released polyplexes. These biodegradable NS are co-injected with nanofibrous spongy microspheres (NF-SMS) to localize the cellular transfection of the pDNA encoding orphan nuclear receptor 4A1 (NR4A1), which was recently reported as a therapeutic agent to delay pathogenic fibrosis. It is shown that HP can transfect human NP cells efficiently in vitro with low cytotoxicity. The two-stage delivery system is able to present the polyplexes over a sustained time period (more than 30 days) in the tail of a rat. The NR4A1 pDNA carried by the HP polyplexes is found to therapeutically reduce the pathogenic fibrosis of NP tissue in a rat-tail degeneration model. In conclusion, the combination of the two-stage NR4A1 pDNA delivery NS and NF-SMS is able to repress fibrosis and to support IVD regeneration.

Mechanosignaling activation of TGFβ maintains intervertebral disc homeostasis

Intervertebral disc (IVD) degeneration is the leading cause of disability with no disease-modifying treatment. IVD degeneration is associated with instable mechanical loading in the spine, but little is known about how mechanical stress regulates nucleus notochordal (NC) cells to maintain IVD homeostasis. Here we report that mechanical stress can result in excessive integrin αvβ6-mediated activation of transforming growth factor beta (TGFβ), decreased NC cell vacuoles, and increased matrix proteoglycan production, and results in degenerative disc disease (DDD). Knockout of TGFβ type II receptor (TβRII) or integrin αv in the NC cells inhibited functional activity of postnatal NC cells and also resulted in DDD under mechanical loading. Administration of RGD peptide, TGFβ, and αvβ6-neutralizing antibodies attenuated IVD degeneration. Thus, integrin-mediated activation of TGFβ plays a critical role in mechanical signaling transduction to regulate IVD cell function and homeostasis. Manipulation of this signaling pathway may be a potential therapeutic target to modify DDD.

Surgical anatomy, radiological features, and molecular biology of the lumbar intervertebral discs

The intervertebral disc (IVD) is a joint unique in structure and functions. Lying between adjacent vertebrae, it provides both the primary support and the elasticity required for the spine to move stably. Various aspects of the IVD have long been studied by researchers seeking a better understanding of its dynamics, aging, and subsequent disorders. In this article, we review the surgical anatomy, imaging modalities, and molecular biology of the lumbar IVD. Clin. Anat. 30:251-266, 2017. © 2017 Wiley Periodicals, Inc.

A regenerative approach towards recovering the mechanical properties of degenerated intervertebral discs: Genipin and platelet-rich plasma therapies

Degenerative disc disease, associated with discrete structural changes in the peripheral annulus and vertebral endplate, is one of the most common pathological triggers of acute and chronic low back pain, significantly depreciating an individual's quality of life and instigating huge socioeconomic costs. Novel emerging therapeutic techniques are hence of great interest to both research and clinical communities alike. Exogenous crosslinking, such as Genipin, and platelet-rich plasma therapies have been recently demonstrated encouraging results for the repair and regeneration of degenerated discs, but there remains a knowledge gap regarding the quantitative degree of effectiveness and particular influence on the mechanical properties of the disc. This study aimed to investigate and quantify the material properties of intact (N = 8), trypsin-denatured (N = 8), Genipin-treated (N = 8), and platelet-rich plasma-treated (N = 8) discs in 32 porcine thoracic motion segments. A poroelastic finite element model was used to describe the mechanical properties during different treatments, while a meta-model analytical approach was used in combination with ex vivo experiments to extract the poroelastic material properties. The results revealed that both Genipin and platelet-rich plasma are able to recover the mechanical properties of denatured discs, thereby affording promising therapeutic modalities. However, platelet-rich plasma-treated discs fared slightly, but not significantly, better than Genipin in terms of recovering the glycosaminoglycans content, an essential building block for healthy discs. In addition to investigating these particular degenerative disc disease therapies, this study provides a systematic methodology for quantifying the detailed poroelastic mechanical properties of intervertebral disc.

miR-221 attenuates the osteogenic differentiation of human annulus fibrosus cells

BACKGROUND

In the moderate and end stages of intervertebral disc (IVD) degeneration, endochondral ossifications are found in the IVD.

PURPOSE

The aim of this study was to investigate whether endochondral ossification in the late stages of disc degeneration is due to the differentiation of resident progenitor cell in the annulus fibrosus (AF) and the potential signaling pathways in vitro.

STUDY DESIGN

This is an in vitro study of AF cell osteogenic differentiation and possible mechanisms

METHODS

Normal annulus fibrosus (NAF) and degenerated annulus fibrosus (DAF) cells were isolated from tissue removed surgically from juvenile patients with idiopathic scoliosis and adult patients with degenerative scoliosis. Osteogenic differentiation was investigated using quantitative reverse transcription polymerase chain reaction (RT-PCR) and histology. The effects of miR-221 on osteogenesis were measured by overexpression of miR-221 with lentivirus. BMP2 and phospho-Smad proteins were detected by Western blotting.

RESULTS

Both NAF and DAF cells underwent osteogenic differentiation, which was confirmed by detecting mineralization of the cell cultures and by an increase in the expression mRNAs for BMP2, runx2, alkaline phosphatase (ALP), and osteocalcin. DAF cells exhibited increased osteogenic differentiation potential over the NAF cells. By contrast to the elevated phospho-Smads, the basal level of miR-221 significantly decreased in DAF cells compared with that in NAF cells. Cultures of both cell types in osteogenic medium showed a decrease in miR-221 expression, and overexpression of miR-221 markedly decreased the level of BMP2, phospho-Smads, and the expression of osteogenic genes in DAF cells. The osteogenic potential of DAF cells diminished by the overexpression of miR-221.

CONCLUSION

Compared with NAF cells, AF cells from degenerated discs have a greater tendency for osteogenic differentiation, which involves the BMP-Smad pathways and can be regulated by miR-221. These observations may be developed into a therapeutic to prevent the endochondral ossification.

Chronic sciatic nerve compression induces fibrosis in dorsal root ganglia

In the present study, pathological alterations in neurons of the dorsal root ganglia (DRG) were investigated in a rat model of chronic sciatic nerve compression. The rat model of chronic sciatic nerve compression was established by placing a 1 cm Silastic tube around the right sciatic nerve. Histological examination was performed via Masson's trichrome staining. DRG injury was assessed using Fluoro Ruby (FR) or Fluoro Gold (FG). The expression levels of target genes were examined using reverse transcription-quantitative polymerase chain reaction, western blot and immunohistochemical analyses. At 3 weeks post-compression, collagen fiber accumulation was observed in the ipsilateral area and, at 8 weeks, excessive collagen formation with muscle atrophy was observed. The collagen volume fraction gradually and significantly increased following sciatic nerve compression. In the model rats, the numbers of FR-labeled DRG neurons were significantly higher, relative to the sham-operated group, however, the numbers of FG-labeled neurons were similar. In the ipsilateral DRG neurons of the model group, the levels of transforming growth factor-β1 (TGF-β1) and connective tissue growth factor (CTGF) were elevated and, surrounding the neurons, the levels of collagen type I were increased, compared with those in the contralateral DRG. In the ipsilateral DRG, chronic nerve compression was associated with significantly higher levels of phosphorylated (p)-extracellular signal-regulated kinase 1/2, and significantly lower levels of p-c-Jun N-terminal kinase and p-p38, compared with those in the contralateral DRGs. Chronic sciatic nerve compression likely induced DRG pathology by upregulating the expression levels of TGF-β1, CTGF and collagen type I, with involvement of the mitogen-activated protein kinase signaling pathway.

Annulus fibrosus cell characteristics are a potential source of intervertebral disc pathogenesis

In the end stage of intervertebral disc degeneration, cartilage, bone, endothelial cells, and neurons appear in association with the worsening condition. The origin of the abnormal cells is not clear. This study investigated the properties of progenitor cells in the annulus fibrosus (AF) using one in vitro and two in vivo models. Cultivation of rabbit AF cells with chondrogenic media significantly increased expressions of collagen and aggrecan. Upon exposure to osteogenic conditions, the cultures showed increased mineralization and expression of osteopontin, runx2, and bmp2 genes. Two models were used in the in vivo subcutaneous implantation experiments: 1) rabbit AF tissue in a demineralized bone matrix (DBM) cylinder (DBM/AF), and, 2) rat intact and needle punctured lumbar discs. Bone formation in the AF tissue was detected and hypertrophic chondrocytes and osteoblasts were present 1 month after implantation of the DBM/AF to nude mice. In addition to collagen I and II, immunostaining shows collagen X and osteocalcin expression in DBM/AF specimens 4 months after implantation. Similar changes were detected in the injured discs. Almost the entire needle punctured disc had ossified at 6 months. The results suggest that AF cells have characteristics of progenitor cells and, under appropriate stimuli, are capable of differentiating into chondrocytes and osteoblasts in vitro as well as in vivo. Importantly, these cells may be a target for biological treatment of disc degeneration.

Intervertebral discs from spinal nondeformity and deformity patients have different mechanical and matrix properties

BACKGROUND CONTEXT

It is well-established that disc mechanical properties degrade with degeneration. However, prior studies utilized cadaveric tissues from donors with undefined back pain history. Disc degeneration may present with pain at the affected motion segment, or it may be present in the absence of back pain. The mechanical properties and matrix quantity of discs removed and diagnosed for degeneration with patient chronic pain may be distinct from those with other diagnoses, such as spinal deformity.

PURPOSE

To test the hypothesis that discs from nondeformity segments have inferior mechanical properties than deformity discs owing to differences in matrix quality.

STUDY DESIGN/SETTING

In vitro study comparing the mechanical and matrix properties of discs from surgery patients with spinal nondeformity and deformity.

METHODS

We analyzed nucleus and annulus samples (8-11 specimens per group) from surgical discectomy patients as part of a fusion or disc replacement procedure. Tissues were divided into two cohorts: nondeformity and deformity. Dynamic indentation tests were used to determine energy dissipation, indentation modulus, and viscoelasticity. Tissue hydration at a physiologic pressure was assessed by equilibrium dialysis. Proteoglycan, collagen, and collagen cross-link content were quantified. Matrix structure was assessed by histology.

RESULTS

We observed that energy dissipation was significantly higher in the nondeformity nucleus than in the deformity nucleus. Equilibrium dialysis experiments showed that annulus swelling was significantly lower in the nondeformity group. Consistent with this, we observed that the nondeformity annulus had lower proteoglycan and higher collagen contents.

CONCLUSIONS

Our data suggest that discs from nondeformity discs have subtle differences in mechanical properties compared with deformity discs. These differences were partially explained by matrix biochemical composition for the annulus, but not for the nucleus. The results of this study suggest that compromised matrix quality and diminished mechanical properties are features that potentially accompany discs of patients undergoing segmental fusion or disc replacement for disc degeneration and chronic back pain. These features have previously been implicated in pain via instability or reduced motion segment stiffness.

CCN2 suppresses catabolic effects of interleukin-1β through α5β1 and αVβ3 integrins in nucleus pulposus cells: implications in intervertebral disc degeneration

The objective of the study was to examine the regulation of CCN2 by inflammatory cytokines, IL-1β, and TNF-α and to determine whether CCN2 modulates IL-1β-dependent catabolic gene expression in nucleus pulposus (NP) cells. IL-1β and TNF-α suppress CCN2 mRNA and protein expression in an NF-κB-dependent but MAPK-independent manner. The conserved κB sites located at -93/-86 and -546/-537 bp in the CCN2 promoter mediated this suppression. On the other hand, treatment of NP cells with IL-1β in combination with CCN2 suppressed the inductive effect of IL-1β on catabolic genes, including MMP-3, ADAMTS-5, syndecan 4, and prolyl hydroxylase 3. Likewise, silencing of CCN2 in human NP cells resulted in elevated basal expression of several catabolic genes and inflammatory cytokines like IL-6, IL-4, and IL-12 as measured by gene expression and cytokine protein array, respectively. Interestingly, the suppressive effect of CCN2 on IL-1β was independent of modulation of NF-κB signaling. Using disintegrins, echistatin, and VLO4, peptide inhibitors to αvβ3 and α5β1 integrins, we showed that CCN2 binding to both integrins was required for the inhibition of IL-1β-induced catabolic gene expression. It is noteworthy that analysis of human tissues showed a trend of altered expression of these integrins during degeneration. Taken together, these results suggest that CCN2 and inflammatory cytokines form a functional negative feedback loop in NP cells that may be important in the pathogenesis of disc disease.

[Biotechnological therapies for the treatment of back pain: alternatives to corticosteroids]

In recent years, it is increasingly clear that back pain is not only caused by biomechanical problems. Currently, biologically-based local therapy concepts for the treatment of affected spinal regions as an alternative to the standard treatment with steroids are in development or in early stages of clinical application. The common features of these new therapies are to intervene in the regulation of homeostasis at various key points at the affected region and specifically to suppress or block catabolic influences as well as to provide with anti-inflammatory substances and growth factors. These include on one hand the genetically produced Biologicals such as TNF-α inhibitors and cytokine antagonists and on the other hand therapies with autologous blood preparations (Autologous Conditioned Serum [ACS], and Platelet Rich Plasma formulations [PRP]). This article presents the individual methods, gives an overview of developments and results of various studies and discusses current recommendations.

Pathophysiology, diagnosis, and treatment of discogenic low back pain

Discogenic low back pain is a serious medical and social problem, and accounts for 26%-42% of the patients with chronic low back pain. Recent studies found that the pathologic features of discs obtained from the patients with discogenic low back pain were the formation of the zones of vascularized granulation tissue, with extensive innervation in fissures extending from the outer part of the annulus into the nucleus pulposus. Studies suggested that the degeneration of the painful disc might originate from the injury and subsequent repair of annulus fibrosus. Growth factors such as basic fibroblast growth factor, transforming growth factor β1, and connective tissue growth factor, macrophages and mast cells might play a key role in the repair of the injured annulus fibrosus and subsequent disc degeneration. Although there exist controversies about the role of discography as a diagnostic test, provocation discography still is the only available means by which to identify a painful disc. A recent study has classified discogenic low back pain into two types that were annular disruption-induced low back pain and internal endplate disruption-induced low back pain, which have been fully supported by clinical and theoretical bases. Current treatment options for discogenic back pain range from medicinal anti-inflammation strategy to invasive procedures including spine fusion and recently spinal arthroplasty. However, these treatments are limited to relieving symptoms, with no attempt to restore the disc's structure. Recently, there has been a growing interest in developing strategies that aim to repair or regenerate the degenerated disc biologically.

Inflammatory cytokines induce NOTCH signaling in nucleus pulposus cells: implications in intervertebral disc degeneration

The objective of the study was to investigate how inflammatory cytokines, IL-1β, and TNF-α control NOTCH signaling activity in nucleus pulposus (NP) cells. An increase in expression of selective NOTCH receptors (NOTCH1 and -2), ligand (JAGGED2), and target genes (HES1, HEY1, and HEY2) was observed in NP cells following cytokine treatment. A concomitant increase in NOTCH signaling as evidenced by induction in activity of target gene HES1 and HEY1 promoters and reporter 12xCSL was seen. Moreover, treatment increased activity of a 2-kb NOTCH2 promoter. Treatment of cells with NF-κB and MAPK inhibitors abolished the inductive effect of cytokines on NOTCH2 promoter and its expression. Gain and loss-of-function studies confirmed the inductive effect of p65 on NOTCH2 promoter activity. In contrast, p50 blocked the cytokine induction of promoter activity. Supporting promoter studies, lentiviral delivery of sh-p65, and sh-IKKβ significantly decreased cytokine dependent change in NOTCH2 expression. Interestingly, MAPK signaling showed an isoform-specific control of NOTCH2 promoter; p38α/β2/δ, ERK1, and ERK2 contributed to cytokine dependent induction, whereas p38γ played no role. Analysis of human NP tissues showed that NOTCH1 and -2 and HEY2 expression correlated with each other. Moreover, expression of NOTCH2 and IL-1β as well as the number of cells immunopositive for NOTCH2 significantly increased in histologically degenerate discs compared with non-degenerate discs. Taken together, these results explain the observed dysregulated expression of NOTCH genes in degenerative disc disease. Thus, controlling IL-1β and TNF-α activities during disc disease may restore NOTCH signaling and nucleus pulposus cell function.

Molecular regulation of CCN2 in the intervertebral disc: lessons learned from other connective tissues

Connective tissue growth factor (CCN2/CTGF) plays an important role in extracellular matrix synthesis, especially in skeletal tissues such as cartilage, bone, and the intervertebral disc. As a result there is a growing interest in examining the function and regulation of this important molecule in the disc. This review discusses the regulation of CCN2 by TGF-β and hypoxia, two critical determinants that characterize the disc microenvironment, and discusses known functions of CCN2 in the disc. The almost ubiquitous regulation of CCN2 by TGF-β, including that seen in the disc, emphasizes the importance of the TGF-β-CCN2 relationship, especially in terms of extracellular matrix synthesis. Likewise, the unique cross-talk between CCN2 and HIF-1 in the disc highlights the tissue and niche specific mode of regulation. Taken together the current literature supports an anabolic role for CCN2 in the disc and its involvement in the maintenance of tissue homeostasis during both health and disease. Further studies of CCN2 in this tissue may reveal valuable targets for the biological therapy of disc degeneration.

Increased periostin gene expression in degenerative intervertebral disc cells

BACKGROUND CONTEXT

Disc degeneration is a multifactorial disease that may cause clinical symptoms such as chronic back pain or radiculopathy in the extremities. Periostin, an extracellular matrix protein involved in the process of fibrosis, expressed in tissues subjected to mechanical stress such as intervertebral disc. However, the expression of periostin during disc degeneration has not yet been studied.

PURPOSE

The aim of this study is to elucidate the difference in gene expression profiles between degenerative and nondegenerative intervertebral discs for a better understanding of disc degeneration.

STUDY DESIGN

Degenerative and nondegenerative nucleus pulposus cells were isolated from elderly patients with degenerative disc disease and younger patients with adolescent idiopathic scoliosis, respectively.

METHODS

Affymetrix GeneChip Human arrays were used to derive gene expression profiles for disc degeneration, and gene expressions of periostin and other degeneration-related markers were confirmed by reverse transcription-polymerase chain reaction (RT-PCR), real-time RT-PCR, and western blot analysis. Immunohistochemical analysis of periostin and Gomori trichrome stain was performed to show the relationship of periostin, fibrosis, and disc degeneration. The mechanical stress experiment was designed to demonstrate the relationship of periostin, stress, and disc degeneration.

RESULTS

Fourteen genes were identified to express at significantly different levels between degenerative and nondegenerative groups. An increase of periostin gene expression was observed in human degenerative nucleus pulposus cells for the messenger RNA and protein levels. Histological examination demonstrated an increased positive staining of periostin in degenerative discs from human tissues and rat needle-punctured tails and more fibrosis with architectural disorder and fragmentation in human degenerative disc as compared with nondegenerative discs. The expression of periostin was significantly induced by stress in human degenerative nucleus pulposus cells but not in nondegenerative cells.

CONCLUSIONS

This study demonstrates for the first time an upregulation of periostin in addition to the expression levels of Type I collagen and matrix metalloproteinase-2 in human disc degeneration. It suggests that periostin may be a candidate gene that shows promise as a new prognostic marker and a therapeutic target that is worth further study to expand our knowledge of its role in disc degeneration.

Expression of leptin, leptin receptor, and connective tissue growth factor in degenerative disk lesions in the wrist

PURPOSE

The purpose of this study was to identify whether leptin and connective tissue growth factor (CTGF) occur in the degenerative fibrocartilage disk and whether cartilage cells express leptin receptors.

METHODS

The study included 23 patients diagnosed with degenerative articular disk tears of the triangular fibrocartilage (TFC) (Palmer type 2C). Patients were divided into 2 groups based on ulna length: 1 group consisted of patients with an ulna-positive variance (group A), and the other group included patients with ulna-negative or -neutral variance (group B). After arthroscopic debridement of the TFC, histologic sections of biopsy specimens were prepared. The biopsy specimens were immunohistochemically analyzed, and the quantity of leptin-, CTGF-, and leptin receptor-positive cells was assessed.

RESULTS

Cells positive for leptin, leptin receptor, and CTGF were found. The number of cells positive for leptin was significantly increased in specimens of patients with an ulna-negative variance (group B). In contrast, no significant difference was found for leptin receptor and CTGF in biopsy specimens of patients with ulna-positive or ulna-negative/neutral variance. The inner, middle, and outer zones of the disk do not express significantly different quantities of marker-positive cells.

CONCLUSIONS

Degenerative fibrocartilage disk tissue cells exhibit leptin receptors and are exposed to the markers leptin and CTGF, providing evidence of a local paracrine system and regenerative processes. Cells of disks from patients with an ulna-neutral/negative length express significantly higher numbers of leptin-positive cells.

LEVEL OF EVIDENCE

Level II, diagnostic study.

Spinal manipulation or mobilization for radiculopathy: a systematic review

In this systematic review, we present a comprehensive and up-to-date systematic review of the literature as it relates to the efficacy and effectiveness of spinal manipulation or mobilization in the management of cervical, thoracic, and lumbar-related extremity pain. There is moderate quality evidence that spinal manipulation is effective for the treatment of acute lumbar radiculopathy. The quality of evidence for chronic lumbar spine-related extremity symptoms and cervical spine-related extremity symptoms of any duration is low or very low. At present, no evidence exists for the treatment of thoracic radiculopathy. Future high-quality studies should address these conditions.

Healing of a painful intervertebral disc should not be confused with reversing disc degeneration: implications for physical therapies for discogenic back pain

BACKGROUND

Much is known about intervertebral disc degeneration, but little effort has been made to relate this information to the clinical problem of discogenic back pain, and how it might be treated.

METHODS

We re-interpret the scientific literature in order to provide a rationale for physical therapy treatments for discogenic back pain.

INTERPRETATION

Intervertebral discs deteriorate over many years, from the nucleus outwards, to an extent that is influenced by genetic inheritance and metabolite transport. Age-related deterioration can be accelerated by physical disruption, which leads to disc "degeneration" or prolapse. Degeneration most often affects the lower lumbar discs, which are loaded most severely, and it is often painful because nerves in the peripheral anulus or vertebral endplate can be sensitised by inflammatory-like changes arising from contact with blood or displaced nucleus pulposus. Surgically-removed human discs show an active inflammatory process proceeding from the outside-in, and animal studies confirm that effective healing occurs only in the outer anulus and endplate, where cell density and metabolite transport are greatest. Healing of the disc periphery has the potential to relieve discogenic pain, by re-establishing a physical barrier between nucleus pulposus and nerves, and reducing inflammation.

CONCLUSION

Physical therapies should aim to promote healing in the disc periphery, by stimulating cells, boosting metabolite transport, and preventing adhesions and re-injury. Such an approach has the potential to accelerate pain relief in the disc periphery, even if it fails to reverse age-related degenerative changes in the nucleus.

Regulation of CCN2/connective tissue growth factor expression in the nucleus pulposus of the intervertebral disc: role of Smad and activator protein 1 signaling

OBJECTIVE

To investigate transforming growth factor beta (TGFbeta) regulation of connective tissue growth factor (CTGF) expression in cells of the nucleus pulposus of rats, mice, and humans.

METHODS

Real-time reverse transcription-polymerase chain reaction and Western blot analyses were used to measure CTGF expression in the nucleus pulposus. Transfections were used to measure the effects of Smads 2, 3, and 7 and activator protein 1 (AP-1) on TGFbeta-mediated CTGF promoter activity.

RESULTS

CTGF expression was lower in neonatal rat discs than in skeletally mature rat discs. An increase in CTGF expression and promoter activity was observed in rat nucleus pulposus cells after TGFbeta treatment. Deletion analysis indicated that promoter constructs lacking Smad and AP-1 motifs were unresponsive to treatment. Analysis showed that full-length Smad3 and the Smad3 MH-2 domain alone increased CTGF activity. Further evidence of Smad3 and AP-1 involvement was seen when DN-Smad3, SiRNA-Smad3, Smad7, and DN-AP-1 suppressed TGFbeta-mediated activation of the CTGF promoter. When either Smad3 or AP-1 sites were mutated, CTGF promoter induction by TGFbeta was suppressed. We also observed a decrease in the expression of CTGF in discs from Smad3-null mice as compared with those from wild-type mice. Analysis of human nucleus pulposus samples indicated a trend toward increasing CTGF and TGFbeta expression in the degenerated state.

CONCLUSION

TGFbeta, through Smad3 and AP-1, serves as a positive regulator of CTGF expression in the nucleus pulposus. We propose that CTGF is a part of the limited reparative response of the degenerated disc.

Multipotential differentiation of human anulus fibrosus cells: an in vitro study

BACKGROUND

The existence of fibrocartilage, bone-like tissues, nerves, and blood vessels in the anulus fibrosus during intervertebral disc degeneration has been well documented. Migration of differentiated cells from outside the intervertebral disc has been hypothesized as a possible mechanism for the formation of these tissues. We hypothesized that the normal anulus fibrosus tissue contains multipotent progenitor cells, which are able to differentiate into cartilage and/or fibrocartilage cells, osteoblasts, neurons, and blood vessel cells.

METHODS

We isolated anulus fibrosus cells from the nondegenerative intervertebral discs of adolescent (thirteen to sixteen-year-old) patients with idiopathic scoliosis and cultured the cells in vitro in induction media containing different stimuli. Immunophenotypic analysis of cell surface markers was performed by flow cytometry. Expression of markers of adipogenesis, osteogenesis, chondrogenesis, neurogenesis, and differentiation into endothelial lineages was determined with use of immunostaining, cytohistological staining, and reverse transcription-polymerase chain reaction.

RESULTS

Anulus fibrosus cells expressed several of the cell surface antigens that are sometimes associated with mesenchymal stem cells, including CD29, CD49e, CD51, CD73, CD90, CD105, CD166, CD184, and Stro-1, and two neuronal stem cell markers, nestin and neuron-specific enolase. Furthermore, varying the stimulants added to the induction media determined whether anulus fibrosus cells differentiated into adipocytes, osteoblasts, chondrocytes, neurons, or endothelial cells.

CONCLUSIONS

Anulus fibrosus cells isolated from nondegenerative intervertebral discs can differentiate into adipocytes, osteoblasts, chondrocytes, neurons, and endothelial cells in vitro.