Nucleus pulposus cells upregulate PI3K/Akt and MEK/ERK signaling pathways under hypoxic conditions and resist apoptosis induced by serum withdrawal

Dynamics of CD44+ bovine nucleus pulposus cells with inflammation

Intervertebral Disc (IVD) degeneration has been associated with a chronic inflammatory response, but knowledge on the contribution of distinct IVD cells, namely CD44, to the progression of IVD degeneration remains elusive. Here, bovine nucleus pulposus (NP) CD44 cells were sorted and compared by gene expression and proteomics with the negative counterpart. NP cells were then stimulated with IL-1b (10 ng/ml) and dynamics of CD44 gene and protein expression was analyzed upon pro-inflammatory treatment. The results emphasize that CD44 has a multidimensional functional role in IVD metabolism, ECM synthesis and production of neuropermissive factors. CD44 widespread expression in NP was partially associated with CD14 and CD45, resulting in the identification of distinct cell subsets. In conclusion, this study points out CD44 and CD44-based cell subsets as relevant targets in the modulation of the IVD pro-inflammatory/degenerative cascade.

Resequencing Analyses Revealed Genetic Diversity and Selection Signatures during Rabbit Breeding and Improvement

Domestication has shaped the diverse characteristics of rabbits, including coat color, fur structure, body size, and various physiological traits. Utilizing whole-genome resequencing (DNBSEQ-T7), we analyzed the genetic diversity, population structure, and genomic selection across 180 rabbits from 17 distinct breeds to uncover the genetic basis of these traits. We conducted whole-genome sequencing on 17 rabbit breeds, identifying 17,430,184 high-quality SNPs and analyzing genomic diversity, patterns of genomic variation, population structure, and selection signatures related to coat color, coat structure, long hair, body size, reproductive capacity, and disease resistance. Through PCA and NJ tree analyses, distinct clusters emerged among Chinese indigenous rabbits, suggesting varied origins and domestication histories. Selective sweep testing pinpointed regions and genes linked to domestication and key morphological and economic traits, including those affecting coat color (TYR, ASIP), structure (LIPH), body size (INSIG2, GLI3), fertility (EDNRA, SRD5A2), heat stress adaptation (PLCB1), and immune response (SEC31A, CD86, LAP3). Our study identified key genomic signatures of selection related to traits such as coat color, fur structure, body size, and fertility; these findings highlight the genetic basis underlying phenotypic diversification in rabbits and have implications for breeding programs aiming to improve productive, reproductive, and adaptive traits. The detected genomic signatures of selection also provide insights into rabbit domestication and can aid conservation efforts for indigenous breeds.

The mitochondrial UPR induced by ATF5 attenuates intervertebral disc degeneration via cooperating with mitophagy

Intervertebral disc degeneration (IVDD) is an aging disease that results in a low quality of life and heavy socioeconomic burden. The mitochondrial unfolded protein response (UPRmt) take part in various aging-related diseases. Our research intents to explore the role and underlying mechanism of UPRmt in IVDD. Nucleus pulposus (NP) cells were exposed to IL-1β and nicotinamide riboside (NR) served as UPRmt inducer to treat NP cells. Detection of ATP, NAD + and NADH were used to determine the function of mitochondria. MRI, Safranin O-fast green and Immunohistochemical examination were used to determine the degree of IVDD in vivo. In this study, we discovered that UPRmt was increased markedly in the NP cells of human IVDD tissues than in healthy controls. In vitro, UPRmt and mitophagy levels were promoted in NP cells treated with IL-1β. Upregulation of UPRmt by NR and Atf5 overexpression inhibited NP cell apoptosis and further improved mitophagy. Silencing of Pink1 reversed the protective effects of NR and inhibited mitophagy induced by the UPRmt. In vivo, NR might attenuate the degree of IDD by activating the UPRmt in rats. In summary, the UPRmt was involved in IVDD by regulating Pink1-induced mitophagy. Mitophagy induced by the UPRmt might be a latent treated target for IVDD.

Differential efficacy of two small molecule PHLPP inhibitors to promote nucleus Pulposus cell health

Background

Intervertebral disc (IVD) degeneration is associated with chronic back pain. We previously demonstrated that the phosphatase pleckstrin homology domain and leucine-rich repeat protein phosphatase (PHLPP) 1 was positively correlated with IVD degeneration and its deficiency decelerated IVD degeneration in both mouse IVDs and human nucleus pulposus (NP) cells. Small molecule PHLPP inhibitors may offer a translatable method to alleviate IVD degeneration. In this study, we tested the effectiveness of the two PHLPP inhibitors NSC117079 and NSC45586 in promoting a healthy NP phenotype.

Methods

Tail IVDs of 5-month-old wildtype mice were collected and treated with NSC117079 or NSC45586 under low serum conditions ex vivo. Hematoxylin & eosin staining was performed to examine IVD structure and NP cell morphology. The expression of KRT19 was analyzed through immunohistochemistry. Cell apoptosis was assessed by TUNEL assay. Human NP cells were obtained from patients with IVD degeneration. The gene expression of KRT19, ACAN, SOX9, and MMP13 was analyzed via real time qPCR, and AKT phosphorylation and the protein expression of FOXO1 was analyzed via immunoblot.

Results

In a mouse IVD organ culture model, NSC45586, but not NSC117079, preserved vacuolated notochordal cell morphology and KRT19 expression while suppressing cell apoptosis, counteracting the degenerative changes induced by serum deprivation, especially in males. Likewise, in degenerated human NP cells, NSC45586 increased cell viability and the expression of KRT19, ACAN, and SOX9 and reducing the expression of MMP13, while NSC117079 treatment only increased KRT19 expression. Mechanistically, NSC45586 treatment increased FOXO1 protein expression in NP cells, and inhibiting FOXO1 offset NSC45586-induced regenerative potential, especially in males.

Conclusions

Our study indicates that NSC45586 was effective in promoting NP cell health, especially in males, suggesting that PHLPP plays a key role in NP cell homeostasis and that NSC45586 might be a potential drug candidate in treating IVD degeneration.

Lipid metabolism disorder promotes the development of intervertebral disc degeneration

Lipid metabolism is a complex process that maintains the normal physiological function of the human body. The disorder of lipid metabolism has been implicated in various human diseases, such as cardiovascular diseases and bone diseases. Intervertebral disc degeneration (IDD), an age-related degenerative disease in the musculoskeletal system, is characterized by high morbidity, high treatment cost, and chronic recurrence. Lipid metabolism disorder may promote the pathogenesis of IDD, and the potential mechanisms are complex. Leptin, resistin, nicotinamide phosphoribosyltransferase (NAMPT), fatty acids, and cholesterol may promote the pathogenesis of IDD, while lipocalin, adiponectin, and progranulin (PGRN) exhibit protective activity against IDD development. Lipid metabolism disorder contributes to extracellular matrix (ECM) degradation, cell apoptosis, and cartilage calcification in the intervertebral discs (IVDs) by activating inflammatory responses, endoplasmic reticulum (ER) stress, and oxidative stress and inhibiting autophagy. Several lines of agents have been developed to target lipid metabolism disorder. Inhibition of lipid metabolism disorder may be an effective strategy for the therapeutic management of IDD. However, an in-depth understanding of the molecular mechanism of lipid metabolism disorder in promoting IDD development is still needed.

Signaling Mechanisms of Stem Cell Therapy for Intervertebral Disc Degeneration

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

CX3CL1/CX3CR1 axis alleviates inflammation and apoptosis in human nucleus pulpous cells via M2 macrophage polarization

CX3C chemokine ligand 1 (CX3CL1) belongs to the CX3C chemokine family and is involved in various disease processes. However, its role in intervertebral disc degeneration (IDD) remains to be elucidated. In the present study, western blotting, reverse transcription-quantitative PCR and ELISA assays were used to assess target gene expression. In addition, immunofluorescence and TUNEL staining were used to assess macrophage infiltration, monocyte migration and apoptosis. The present study aimed to reveal if and how CX3CL1 regulates IDD progression by exploring its effect on macrophage polarization and apoptosis of human nucleus pulposus cells (HNPCs). The data showed that CX3CL1 bound to CX3C motif chemokine receptor 1 (CX3CR1) promoted the M2 phenotype polarization via JAK2/STAT3 signaling, followed by increasing the secretion of anti-inflammatory cytokines from HNPCs. In addition, HNPC-derived CX3CL1 promoted M2 macrophage-derived C-C motif chemokine ligand 17 release thereby reducing the apoptosis of HNPCs. In clinic, the reduction of mRNA and protein levels CX3CL1 in degenerative nucleus pulposus tissues (NPs) was measured. Increased M1 macrophages and pro-inflammatory cytokines were found in NPs of IDD patients with low CX3CL1 expression. Collectively, these findings suggested that the CX3CL1/CX3CR1 axis alleviates IDD by reducing inflammation and apoptosis of HNPCs via macrophages. Therefore, targeting CX3CL1/CX3CR1 axis is expected to produce a new therapeutic approach for IDD.

The Neuroprotective Activities of the Novel Multi-Target Iron-Chelators in Models of Alzheimer's Disease, Amyotrophic Lateral Sclerosis and Aging

The concept of chelation therapy as a valuable therapeutic approach in neurological disorders led us to develop multi-target, non-toxic, lipophilic, brain-permeable compounds with iron chelation and anti-apoptotic properties for neurodegenerative diseases, such as Parkinson's disease (PD), Alzheimer's disease (AD), age-related dementia and amyotrophic lateral sclerosis (ALS). Herein, we reviewed our two most effective such compounds, M30 and HLA20, based on a multimodal drug design paradigm. The compounds have been tested for their mechanisms of action using animal and cellular models such as APP/PS1 AD transgenic (Tg) mice, G93A-SOD1 mutant ALS Tg mice, C57BL/6 mice, Neuroblastoma × Spinal Cord-34 (NSC-34) hybrid cells, a battery of behavior tests, and various immunohistochemical and biochemical techniques. These novel iron chelators exhibit neuroprotective activities by attenuating relevant neurodegenerative pathology, promoting positive behavior changes, and up-regulating neuroprotective signaling pathways. Taken together, these results suggest that our multifunctional iron-chelating compounds can upregulate several neuroprotective-adaptive mechanisms and pro-survival signaling pathways in the brain and might function as ideal drugs for neurodegenerative disorders, such as PD, AD, ALS, and aging-related cognitive decline, in which oxidative stress and iron-mediated toxicity and dysregulation of iron homeostasis have been implicated.

Colorectal Cancer: The Contribution of CXCL12 and Its Receptors CXCR4 and CXCR7

Simple Summary

Many signaling pathways are involved in cancer progression, and among these pathways, the CXCL12 axis and its two receptors CXCR4 and CXCR7 are well described for many cancers. This review presents the current knowledge on the role played by each of the actors of this axis in colorectal cancer and on its consideration in the development of new therapeutic strategies.

Abstract

Colorectal cancer is one of the most common cancers, and diagnosis at late metastatic stages is the main cause of death related to this cancer. This progression to metastasis is complex and involves different molecules such as the chemokine CXCL12 and its two receptors CXCR4 and CXCR7. The high expression of receptors in CRC is often associated with a poor prognosis and aggressiveness of the tumor. The interaction of CXCL12 and its receptors activates signaling pathways that induce chemotaxis, proliferation, migration, and cell invasion. To this end, receptor inhibitors were developed, and their use in preclinical and clinical studies is ongoing. This review provides an overview of studies involving CXCR4 and CXCR7 in CRC with an update on their targeting in anti-cancer therapies.

Self-Assembling Peptide Hydrogels as Functional Tools to Tackle Intervertebral Disc Degeneration

Low back pain (LBP), caused by intervertebral disc (IVD) degeneration, is a major contributor to global disability. In its healthy state, the IVD is a tough and well-hydrated tissue, able to act as a shock absorber along the spine. During degeneration, the IVD is hit by a cell-driven cascade of events, which progressively lead to extracellular matrix (ECM) degradation, chronic inflammation, and pain. Current treatments are divided into palliative care (early stage degeneration) and surgical interventions (late-stage degeneration), which are invasive and poorly efficient in the long term. To overcome these limitations, alternative tissue engineering and regenerative medicine strategies, in which soft biomaterials are used as injectable carriers of cells and/or biomolecules to be delivered to the injury site and restore tissue function, are currently being explored. Self-assembling peptide hydrogels (SAPHs) represent a promising class of de novo synthetic biomaterials able to merge the strengths of both natural and synthetic hydrogels for biomedical applications. Inherent features, such as shear-thinning behaviour, high biocompatibility, ECM biomimicry, and tuneable physiochemical properties make these hydrogels appropriate and functional tools to tackle IVD degeneration. This review will describe the pathogenesis of IVD degeneration, list biomaterials requirements to attempt IVD repair, and focus on current peptide hydrogel materials exploited for this purpose.

GSK-3β inhibition protects human nucleus pulposus cell against oxidative stress-inducing apoptosis through mitochondrial pathway

BACKGROUND

Oxidative stress in the intervertebral disc leads to nucleus pulposus (NP) degeneration by inducing cell apoptosis. However, the molecular mechanisms underlying this process remain unclear. Increasing evidence indicates that GSK-3β is related to cell apoptosis induced by oxidative stress. In this study, we explored whether GSK-3β inhibition protects human NP cell against apoptosis under oxidative stress.

METHODS AND RESULTS

Immunofluorescence staining was used to show the expression of GSK-3β in human NP cells (NPCs). Flow cytometry, mitochondrial staining and western blot (WB) were used to detect apoptosis of treated NPCs, changes of mitochondrial membrane potential and the expression of mitochondrial apoptosis-related proteins using GSK-3β specific inhibitor SB216763. Co-Immunoprecipitation (Co-IP) was used to demonstrate the interaction between GSK-3β and Bcl-2. We delineated the protective effect of GSK-3β specific inhibitor SB216763 on human NPCs apoptosis induced by oxidative stress in vitro. Further, we showed SB216763 exert the protective effect by preservation of the mitochondrial membrane potential and inhibition of caspase 3/7 activity during oxidative injury. The detailed mechanism underlying the antiapoptotic effect of GSK-3β inhibition was also studied by analyzing mitochondrial apoptosis pathway in vitro.

CONCLUSIONS

We concluded that the GSK-3β inhibitor SB216763 protected mitochondrial membrane potential to delay nucleus pulposus cell apoptosis by inhibiting the interaction between GSK-3β and Bcl-2 and subsequently reducing cytochrome c(Cyto-C) release and caspase-3 activation. Together, inhibition of GSK-3β using SB216763 in NPCs may be a favorable therapeutic strategy to slow intervertebral disc degeneration.

Development of a library of laminin-mimetic peptide hydrogels for control of nucleus pulposus cell behaviors

The nucleus pulposus (NP) of the intervertebral disc plays a critical role in distributing mechanical loads to the axial skeleton. Alterations in NP cells and, consequently, NP matrix are some of the earliest changes in the development of disc degeneration. Previous studies demonstrated a role for laminin-presenting biomaterials in promoting a healthy phenotype for human NP cells from degenerated tissue. Here we investigate the use of laminin-mimetic peptides presented individually or in combination on a poly(ethylene) glycol hydrogel as a platform to modulate the behaviors of degenerative human NP cells. Data confirm that NP cells attach to select laminin-mimetic peptides that results in cell signaling downstream of integrin and syndecan binding. Furthermore, the peptide-functionalized hydrogels demonstrate an ability to promote cell behaviors that mimic that of full-length laminins. These results identify a set of peptides that can be used to regulate NP cell behaviors toward a regenerative engineering strategy.

Effect of Whole Tissue Culture and Basic Fibroblast Growth Factor on Maintenance of Tie2 Molecule Expression in Human Nucleus Pulposus Cells

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

Salvianolic Acid B Protects Intervertebral Discs from Oxidative Stress-Induced Degeneration via Activation of the JAK2/STAT3 Signaling Pathway

OBJECTIVE

To evaluate the influence of salvianolic acid B (SAB), an antioxidant derived from Danshen, on intervertebral disc degeneration (IDD) and its possible molecular mechanisms.

METHODS

Sixty adult rats were randomly grouped (control, IDD, and SAB IDD groups). IDD was induced using needle puncture. The rats received daily administration of SAB (20 mg/kg) in the SAB IDD group while the other two groups received only distilled water. The extent of IDD was evaluated using MRI after 3 and 6 weeks and histology after 6 weeks. Oxidative stress was assessed using the ELISA method. In in vitro experiments, nucleus pulposus cells (NPCs) were treated with H2O2 (100 μM) or SAB+H2O2, and levels of oxidative stress were measured. Cell apoptosis was assessed by flow cytometry, expression levels of Bcl-2, Bax, and cleaved caspase-3 proteins. Cell proliferation rate was assessed by EdU analysis. Pathway involvement was determined by Western blotting while the influence of the pathway on NPCs was explored using the pathway inhibitor AG490.

RESULTS

The data demonstrate that SAB attenuated injury-induced IDD and oxidative stress, caused by activation of the JAK2/STAT3 signaling pathway in vivo. Oxidative stress induced by H2O2 was reversed by SAB in vitro. SAB reduced the increased cell apoptosis, cleaved caspase-3 expression, and caspase-3 activity induced by H2O2. Reduced cell proliferation and decreased Bcl-2/Bax ratio induced by H2O2 were rescued by SAB. Additionally, the JAK2/STAT3 pathway was activated by SAB, while AG490 counteracted this effect.

CONCLUSION

The results suggest that SAB protects intervertebral discs from oxidative stress-induced degeneration by enhancing proliferation and attenuating apoptosis via activation of the JAK2/STAT3 signaling pathway.

Multiscale Regulation of the Intervertebral Disc: Achievements in Experimental, In Silico, and Regenerative Research

Intervertebral disc (IVD) degeneration is a major risk factor of low back pain. It is defined by a progressive loss of the IVD structure and functionality, leading to severe impairments with restricted treatment options due to the highly demanding mechanical exposure of the IVD. Degenerative changes in the IVD usually increase with age but at an accelerated rate in some individuals. To understand the initiation and progression of this disease, it is crucial to identify key top-down and bottom-up regulations' processes, across the cell, tissue, and organ levels, in health and disease. Owing to unremitting investigation of experimental research, the comprehension of detailed cell signaling pathways and their effect on matrix turnover significantly rose. Likewise, in silico research substantially contributed to a holistic understanding of spatiotemporal effects and complex, multifactorial interactions within the IVD. Together with important achievements in the research of biomaterials, manifold promising approaches for regenerative treatment options were presented over the last years. This review provides an integrative analysis of the current knowledge about (1) the multiscale function and regulation of the IVD in health and disease, (2) the possible regenerative strategies, and (3) the in silico models that shall eventually support the development of advanced therapies.

Ref-1 protects against FeCl3-induced thrombosis and tissue factor expression via the GSK3β-NF-κB pathway

Arterial thrombosis and its associated diseases are considered to constitute a major healthcare problem. Arterial thrombosis, defined as blood clot formation in an artery that interrupts blood circulation, is associated with many cardiovascular diseases. Oxidative stress is one of many important factors that aggravates the pathophysiological process of arterial thrombosis. Apurinic/apyrimidinic endonuclease 1/redox factor-1 (Ref-1) has a multifunctional role in cells that includes the regulation of oxidative stress and anti-inflammatory function. The aim of this study was to investigate the therapeutic effect of adenovirus-mediated Ref-1 overexpression on arterial thrombosis induced by 60% FeCl₃ solution in rats. Blood flow was measured to detect the time to occlusion, thrombus formation was detected by hematoxylin and eosin staining, reactive oxygen species (ROS) levels were detected by high-performance liquid chromatography, and the expression of tissue factor and other proteins was detected by Western blot. FeCl₃ aggravated thrombus formation in carotid arteries and reduced the time to artery occlusion. Ref-1 significantly delayed arterial obstruction via the inhibition of thrombus formation, especially by downregulating tissue factor expression through the Akt-GSK3β-NF-κB signaling pathway. Ref-1 also reduced the expression of vascular inflammation markers ICAM-1 and VCAM-1, and reduced the level of ROS that contributed to thrombus formation. The results showed that adenovirus-mediated Ref-1 overexpression reduced thrombus formation in the rat carotid artery. In summary, Ref-1 overexpression had anti-thrombotic effects in a carotid artery thrombosis model and could be a target for the treatment of arterial thrombosis.

Small molecule-based treatment approaches for intervertebral disc degeneration: Current options and future directions

Low back pain (LBP) is a major reason for disability, and symptomatic intervertebral disc (IVD) degeneration (IDD) contributes to roughly 40% of all LBP cases. Current treatment modalities for IDD include conservative and surgical strategies. Unfortunately, there is a significant number of patients in which conventional therapies fail with the result that these patients remain suffering from chronic pain and disability. Furthermore, none of the current therapies successfully address the underlying biological problem - the symptomatic degenerated disc. Both spinal fusion as well as total disc replacement devices reduce spinal motion and are associated with adjacent segment disease. Thus, there is an unmet need for novel and stage-adjusted therapies to combat IDD. Several new treatment options aiming to regenerate the IVD are currently under investigation. The most common approaches include tissue engineering, growth factor therapy, gene therapy, and cell-based treatments according to the stage of degeneration. Recently, the regenerative activity of small molecules (low molecular weight organic compounds with less than 900 daltons) on IDD was demonstrated. However, small molecule-based therapy in IDD is still in its infancy due to limited knowledge about the mechanisms that control different cell signaling pathways of IVD homeostasis. Small molecules can act as anti-inflammatory, anti-apoptotic, anti-oxidative, and anabolic agents, which can prevent further degeneration of disc cells and enhance their regeneration. This review pursues to give a comprehensive overview of small molecules, focusing on low molecular weight organic compounds, and their potential utilization in patients with IDD based on recent in vitro, in vivo, and pre-clinical studies.

Role of autophagy in intervertebral disc and cartilage function: implications in health and disease

The intervertebral disc and cartilage are specialized, extracellular matrix-rich tissues critical for absorbing mechanical loads, providing flexibility to the joints, and longitudinal growth in the case of growth plate cartilage. Specialized niche conditions in these tissues, such as hypoxia, are critical in regulating cellular activities including autophagy, a lysosomal degradation pathway that promotes cell survival. Mounting evidence suggests that dysregulation of autophagic pathways underscores many skeletal pathologies affecting the spinal column, articular and growth plate cartilages. Many lysosomal storage disorders characterized by the accumulation of partially degraded glycosaminoglycans (GAGs) due to the lysosomal dysfunction thus affect skeletal tissues and result in altered ECM structure. Likewise, pathologies that arise from mutations in genes encoding ECM proteins and ECM processing, folding, and post-translational modifications, result in accumulation of misfolded proteins in the ER, ER stress and autophagy dysregulation. These conditions evidence reduced secretion of ECM proteins and/or increased secretion of mutant proteins, thereby impairing matrix quality and the integrity of affected skeletal tissues and causing a lack of growth and degeneration. In this review, we discuss the role of autophagy and mechanisms of its regulation in the intervertebral disc and cartilages, as well as how dysregulation of autophagic pathways affects these skeletal tissues.

Calcium Phosphate Cement Causes Nucleus Pulposus Cell Degeneration through the ERK Signaling Pathway

While calcium phosphate cement (CPC) is recognized as one of the most likely substitutes for the conventional Polymethylmethacrylate (PMMA), there are very few studies about its intradiscal leakage consequences. Herein, the goal of our study was to examine the effect of CPC particles on the ERK (extracellular regulatory kinase) pathway in human nucleus pulposus cell (HNPC) degeneration. Different concentrations of CPC particles (0.00‰, 0.01‰, 0.05‰, 0.1‰ v/v) were added to human nucleus pulposus cell cultures. After 10 days of treatment, HNPC biological behaviors and degeneration degree were analyzed by CCK-8 assay, crystal violet staining, flow cytometer and western blot. The effect of CPC on the ERK pathway was also analyzed by western blot. After activating the ERK path by overexpressing Ras, HNPCs’ biological behaviors and degeneration degree were analyzed again. We found that CPC particles had a negative effect on human nucleus pulposus cells (HNPCs), which are mainly reflected in cell growth and the cell cycle. After activation of the ERK signaling pathway, the negative effects of CPC on cell growth and the cell cycle were significantly reduced and the degeneration degree of HNPCs was reversed. CPC particles can probably block the activation of the ERK pathway, thus causing the HNPCs’ degeneration.

Melatonin Protects Intervertebral Disc from Degeneration by Improving Cell Survival and Function via Activation of the ERK1/2 Signaling Pathway

Melatonin, a neuroendocrine hormone secreted by the pineal body, has a positive effect on intervertebral disc degeneration. The present study is aimed at investigating the biological role of melatonin in intervertebral disc degeneration and its underlying mechanism. A human nucleus pulposus cell (NPC) line was exposed to melatonin at different concentrations. Cell proliferation was measured by CCK-8 assay. Cell cycle and apoptosis were analyzed by flow cytometry. Western blot was performed to measure the protein expression of indicated genes. A rabbit model of intervertebral disc degeneration was established to detect the role and mechanism of melatonin on intervertebral disc degeneration. Our study showed that melatonin promoted NPC viability and inhibited cell arrest. Furthermore, melatonin treatment led to the upregulation of collagen II and aggrecan and downregulation of collagen X. Moreover, melatonin significantly elevated the activity of the ERK signaling pathway. Inhibition of the ERK1/2 signals reversed the role of melatonin in the regulation of NPCs both in vitro and in vivo. Melatonin increased NPC viability through inhibition of cell cycle arrest and apoptosis. Moreover, melatonin promoted the secretion of functional factors influencing the nucleus pulposus cell physiology and retarded cell degeneration. Our results suggest that melatonin activated the ERK1/2 signaling pathway, thereby affecting the biological properties of the intervertebral disc degeneration.

PTEN promotes intervertebral disc degeneration by regulating nucleus pulposus cell behaviors

Intervertebral disc degeneration (IDD) is induced by multiple factors including increased apoptosis, decreased survival, and reduced extracellular matrix (ECM) synthesis in the nucleus pulposus (NP) cells. The tumor suppressor phosphatase and tensin homolog deleted from chromosome 10 (PTEN) is the only known lipid phosphatase counteracting the PI3K/AKT pathway. Loss of PTEN leads to activated PI3K/AKT signaling, which plays a key role in a variety of cancers. However, the role of PTEN/PI3K/AKT signaling nexus in IDD remains unknown. Here, we report that PTEN is overexpressed in degenerative NP, which correlates with inactivated AKT. Using the PTEN knockdown approach by lentivirus-mediated short interfering RNA gene transfer technique, we report that PTEN decreases survival but induces apoptosis and senescence of NP cells. PTEN also inhibits expression and production of ECM components including collagen II, aggrecan, and proteoglycan. Furthermore, PTEN modulates the expression of ECM regulatory molecules SOX-9 and matrix metalloproteinase-3 (MMP-3). Using small-molecule AKT inhibitor GDC-0068, we confirm that PTEN regulates NP cell behaviors through its direct targeting of PI3K/AKT. These findings demonstrate for the first time that PTEN/PI3K/AKT signaling axis plays an important role in the pathogenesis of IDD. Targeting PTEN using gene therapy may represent a promising therapeutic approach against disc degenerative diseases.

Phlpp1 is associated with human intervertebral disc degeneration and its deficiency promotes healing after needle puncture injury in mice

Back pain is a leading cause of global disability and is strongly associated with intervertebral disc (IVD) degeneration (IDD). Hallmarks of IDD include progressive cell loss and matrix degradation. The Akt signaling pathway regulates cellularity and matrix production in IVDs and its inactivation is known to contribute to a catabolic shift and increased cell loss via apoptosis. The PH domain leucine-rich repeat protein phosphatase (Phlpp1) directly regulates Akt signaling and therefore may play a role in regulating IDD, yet this has not been investigated. The aim of this study was to investigate if Phlpp1 has a role in Akt dysregulation during IDD. In human IVDs, Phlpp1 expression was positively correlated with IDD and the apoptosis marker cleaved Caspase-3, suggesting a key role of Phlpp1 in the progression of IDD. In mice, 3 days after IVD needle puncture injury, Phlpp1 knockout (KO) promoted Akt phosphorylation and cell proliferation, with less apoptosis. At 2 and 8 months after injury, Phlpp1 deficiency also had protective effects on IVD cellularity, matrix production, and collagen structure as measured with histological and immunohistochemical analyses. Specifically, Phlpp1-deletion resulted in enhanced nucleus pulposus matrix production and more chondrocytic cells at 2 months, and increased IVD height, nucleus pulposus cellularity, and extracellular matrix deposition 8 months after injury. In conclusion, Phlpp1 has a role in limiting cell survival and matrix degradation in IDD and research targeting its suppression could identify a potential therapeutic target for IDD.

Prognostic value of EGFR 19-del and 21-L858R mutations in patients with non-small cell lung cancer

Previous studies have demonstrated a significant difference in clinical characteristics between patients with non-small cell lung cancer (NSCLC) harboring exon 19 deletion (19-del) and an exon point mutation (21-L858R) in EGFR. The present retrospective study aimed to investigate the differential prognosis in patients with NSCLC harboring exon 19-del and 21-L858R mutations. The clinical and follow-up data of 137 patients treated at the Zhongnan Hospital of Wuhan University (Wuhan, Hubei, China) between August 2012 and August 2016, who were diagnosed with stage IIIB-IV NSCLC harboring either exon 19-del or 21-L858R mutations, were analyzed. The patients were divided into the first-line tyrosine kinase inhibitor (TKI), first-line chemotherapy and second-line TKI treatment groups. The median progression-free survival (PFS) time of patients harboring the exon 19-del mutation was significantly improved compared with that in patients harboring the 21-L858R mutation (11.3 vs. 8.8 months, respectively; P=0.017) following first-line TKI treatments. However, no significant difference in the median PFS time was observed between the exon 19-del and 21-L858R groups following the first-line chemotherapy or second-line TKI treatment. In patients with the exon 19-del, first-line TKI treatment achieved an increased objective response rate (ORR; 51.9 vs. 18.5%; P=0.004) and disease control rate (96.2 vs. 77.8%; P=0.030), and a longer PFS time (11.3 vs. 8.0 months; P=0.034) compared with that in the patients following first-line chemotherapy. First- and second-line TKI treatment achieved a similar PFS time (11.3 vs. 11.0 months, respectively; P=0.140). However, in patients with the 21-L858R mutation, the first-line TKI therapy and first-line chemotherapy groups exhibited a similar PFS time (8.8 vs. 3.5 months, respectively; P=0.063), while the second-line TKI treatment group exhibited a significantly longer PFS time compared with the first-line TKI treatment group (13.6 vs. 8.8 months, respectively; P=0.030). There was a differential sensitivity to treatment between patients harboring the exon 19-del and 21-L858R mutations. Therefore, chemotherapy may increase the sensitivity to TKIs in patients harboring the 21-L858R mutation.

Effects of Oxygen Concentration and Culture Time on Porcine Nucleus Pulposus Cell Metabolism: An in vitro Study

Low back pain is a common ailment that affects millions of individuals each year and is linked to degeneration of the intervertebral discs in the spine. Intervertebral disc degeneration is known to result from an imbalance in anabolic and catabolic activity by disc cells. Due to the avascular nature of the intervertebral disc, oxygen deficiency may occur in the central nucleus pulposus (NP). The resulting hypoxia affects matrix regulation and energy metabolism of disc cells, although the mechanisms are not fully understood. This study investigates in vitro glucose consumption and gene expression by NP cells over time under varying oxygen tensions. Notochordal porcine NP cells were cultured in agarose discs at 21, 5, or 1% oxygen tension for 1, 5, or 10 days. The expression of 10 key matrix genes, as well as Brachyury (T), by NP cells was analyzed using RT-PCR. Glucose consumption was measured using a two-point method. Results show that culture time and oxygen tension significantly affect glucose consumption rates by porcine NP cells. There were also significant changes in T expression based on oxygen level and culture time. The 1% oxygen tension had a significantly higher T expression on day 10 than the other two groups, which may indicate a better maintenance of the notochordal phenotype. MMP 1 and 13 expression increased over time for all groups, while only the 5% group showed an increase over time for MMP 3. TIMP expression followed the direction of MMPs but to a lesser magnitude. Five percent and twenty-one percent oxygen tensions led to decreases in anabolic gene expression while 1% led to increases. Oxygen concentration and culture time significantly impacted glucose consumption rate and the gene expression of matrix regulatory genes with hypoxic conditions most accurately maintaining the proper NP phenotype. This information is valuable not only for understanding disc pathophysiology, but also for harnessing the potential of notochordal NP cells in therapeutic applications.

Serum and nutrient deprivation increase autophagic flux in intervertebral disc annulus fibrosus cells: an in vitro experimental study

PURPOSE

The loss of nutrient supply is a suspected contributor of intervertebral disc degeneration. However, the extent to which low nutrition affects disc annulus fibrosus (AF) cells is unknown as nutrient deprivation has mainly been investigated in disc nucleus pulposus cells. Hence, an experimental study was designed to clarify the effects of limited nutrients on disc AF cell fate, including autophagy, the process by which cells recycle their own damaged components.

METHODS

Rabbit disc AF cells were cultured in different media with varying serum concentrations under 5% oxygen. Cellular responses to changes in serum and nutrient concentrations were determined by measuring proliferation and metabolic activity. Autophagic flux in AF cells was longitudinally monitored using imaging cytometry and Western blotting for LC3, HMGB1, and p62/SQSTM1. Apoptosis (TUNEL staining and cleaved caspase-3 immunodetection) and cellular senescence (senescence-associated β-galactosidase assay and p16/INK4A immunodetection) were measured.

RESULTS

Markers of apoptosis and senescence increased, while cell proliferation and metabolic activity decreased under the withdrawal of serum and of nutrients other than oxygen, confirming cellular stress. Time-dependent increases in autophagy markers, including LC3 puncta number per cell, LC3-II expression, and cytoplasmic HMGB1, were observed under conditions of reduced nutrition, while an autophagy substrate, p62/SQSTM1, decreased over time. Collectively, these findings suggest increased autophagic flux in disc AF cells under serum and nutrient deprivation.

CONCLUSION

Disc AF cells exhibit distinct responses to serum and nutrient deprivation. Cellular responses include cell death and quiescence in addition to reduced proliferation and metabolic activity, as well as activation of autophagy under conditions of nutritional stress. These slides can be retrieved under Electronic Supplementary Material.

Urolithin A Inhibits the Catabolic Effect of TNFα on Nucleus Pulposus Cell and Alleviates Intervertebral Disc Degeneration in vivo

Low back pain (LBP) is a common worldwide disease that causes an enormous social economic burden. Intervertebral disc degeneration (IDD) is considered as a major cause of LBP. The process of IDD is complicated and involves both inflammation and senescence. The production of pro-inflammatory cytokines, including tumor necrosis factor (TNF)α and interleukin (IL)-1β, is increased in the degenerating intervertebral disc, inducing extracellular matrix degradation. Urolithin A (UA) is a metabolite compound resulting from the degradation of ellagitannins by gut bacteria. UA has been reported to be useful for the treatment of diseases associated with inflammation, senescence, and oxidative damage. Therefore, we hypothesized that UA may be an effective treatment for IDD. This study examined the effects of UA on IDD in vitro and in vivo and explored their underlying mechanisms. Our findings indicated that UA could attenuate cellular senescence induced by hydrogen peroxide in nucleus pulposus cells. UA treatment decreased TNFα-induced matrix metalloproteinase production and the loss of collagen II. At the molecular level, UA considerably blocked the phosphorylation of the extracellular signal-regulated kinase, c-JUN N-terminal kinase, and Akt pathways. In vivo study illustrated that UA treatment could ameliorate IDD in a needle-punctured rat tail model, which was evaluated by X-ray imaging, magnetic resonance imaging, and histological analysis. Thus, the results of our study revealed that UA may be a useful therapeutic agent for the treatment of IDD.

Resveratrol enhances matrix biosynthesis of nucleus pulposus cells through activating autophagy via the PI3K/Akt pathway under oxidative damage

The decrease in nucleus pulposus (NP) matrix production is a classic feature during disc degeneration. Resveratrol (RSV) is reported to play protective effects under many pathological factors.The present study aims to study the effects of RSV on NP matrix homeostasis under oxidative damage and the potential mechanism. Rat NP cells were exposed to H₂O₂ solution to create an oxidative damage. RSV and the 3-methyladenine (3-MA) were added along with the culture medium to respectively investigate the role of RSV and cellular autophagy. NP matrix synthesis was evaluated by the expression of macromolecules (aggrecan and collagen II) and glycosaminoglycan (GAG) content. Activation of cellular autophagy was assessed by the expression of several molecular markers. Additionally, activity of the PI3K/Akt pathway was also evaluated to study its potential role. Compared with the control group (NP cells treated with H₂O₂), RSV significantly up-regulated expression of matrix macromolecules (aggrecan and collagen), promoted GAG production, and increased the expression of autophagy-related markers (Beclin-1 and LC-3). Further analysis showed that inhibition of autophagy by 3-MA partly attenuated NP matrix production. Additionally, RSV increased activity of the PI3K/Akt pathway compared with the control NP cells, but it was not affected by the addition of 3-MA. RSV plays a protective role in enhancing NP matrix synthesis under oxidative damage. Mechanistically, activation of the cellular autophagy via the PI3K/Akt pathway may participate in this process. RSV may be an effective drug to attenuate oxidative stress-induced disc degeneration.

Mechanotransduction and cell biomechanics of the intervertebral disc

Mechanical loading of the intervertebral disc (IVD) initiates cell-mediated remodeling events that contribute to disc degeneration. Cells of the IVD, nucleus pulposus (NP) and anulus fibrosus (AF), will exhibit various responses to different mechanical stimuli which appear to be highly dependent on loading type, magnitude, duration, and anatomic zone of cell origin. Cells of the NP, the innermost region of the disc, exhibit an anabolic response to low-moderate magnitudes of static compression, osmotic pressure, or hydrostatic pressure, while higher magnitudes promote a catabolic response marked by increased protease expression and activity. Cells of the outer AF are responsive to physical forces in a manner that depends on frequency and magnitude, as are cells of the NP, though they experience different forces, deformations, pressure, and osmotic pressure in vivo. Much remains to be understood of the mechanotransduction pathways that regulate IVD cell responses to loading, including responses to specific stimuli and also differences among cell types. There is evidence that cytoskeletal remodeling and receptor-mediated signaling are important mechanotransduction events that can regulate downstream effects like gene expression and posttranslational biosynthesis, all of which may influence phenotype and bioactivity. These and other mechanotransduction events will be regulated by known and to-be-discovered cell-matrix and cell-cell interactions, and depend on composition of extracellular matrix ligands for cell interaction, matrix stiffness, and the phenotype of the cells themselves. Here, we present a review of the current knowledge of the role of mechanical stimuli and the impact upon the cellular response to loading and changes that occur with aging and degeneration of the IVD.

Hypoxia suppresses serum deprivation-induced degradation of the nucleus pulposus cell extracellular matrix through the JNK and NF-κB pathways

Intervertebral disc (IVD) degeneration is associated with the imbalance between anabolism and catabolism of the nucleus pulposus (NP) extracellular matrix (ECM). Serum deprivation (SD) has been reported to exacerbate IVD degeneration; however, the effect of SD on ECM metabolism is not fully understood. Hypoxia plays important roles in maintaining the physiological functions of IVD cells; however, whether hypoxia has any effect on NP ECM production under conditions of SD is still unclear. In the current study, we established an in vitro SD model by exposing NP cells to serum-free medium. SD decreased the expression of aggrecan and collagen II, as well as the production of sulfated glycosaminoglycan (sGAG) in a time-dependent manner. However, hypoxia abolished SD-mediated down-regulation of aggrecan and collagen II expression via JNK1/2 activation. Moreover, hypoxia abolished SD-induced MMP-3 and MMP-13 expression by inhibiting NF-κB activation, p65 translocation, and MMP-3 and MMP-13 promoter activity. These results indicated that, hypoxia maintained ECM production under conditions of SD. This effect was elicited in part through JNK1/2-mediated up-regulation of matrix gene expression and down-regulation of MMP expression, through the inhibition of NF-κB. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2059-2066, 2017.

The role of angiopoietin-2 in nucleus pulposus cells during human intervertebral disc degeneration

Although evidence shows that intervertebral disc degeneration is generally characterized by angiogenesis, the role of angiopoietin has not been investigated. This study examined the presence of angiopoietin-1 (Ang-1) and angiopoietin-2 (Ang-2) within the native intervertebral disc (IVD) and elucidated their functions in the regulation of nucleus pulposus (NP) cells. Initial investigation of uncultured NP tissue revealed that Ang-1 and Ang-2 were expressed by native NP cells. Ang-2 expression was significantly increased in infiltrated and degenerate samples relative to normal samples. The ratio of Ang-2/Ang-1 in tissues from patients increased markedly with increasing age and level of degeneration of the IVD. The ratio of both Ang-2/Ang-1 mRNA and protein increased over time when cells were subjected to constant pressure at 1 Mpa in vitro. Our findings indicate that Ang-2 plays a role in suppressing cell adhesion and viability, and promotes the apoptosis of NP cells and that Ang-2 can inhibit the pathways stimulated by Ang-1 and fibronectin. Ang-2 release during IVD degeneration causes higher ratio of Ang-2 to Ang-1, further inhibits NP cell viability and adhesion, promoting apoptosis by blocking PI3K/Akt signaling. The present study therefore provides new insights into the role of the angiopoietin-Tie system in the pathogenesis of IVD degeneration.

The PI3K/Akt pathway: a critical player in intervertebral disc degeneration

Intervertebral disc degeneration (IDD) is thought to be the primary cause of low back pain, a severe public health problem worldwide. Current therapy for IDD aims to alleviate the symptoms and does not target the underlying pathological alternations within the disc. Activation of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway protects against IDD, which is attributed to increase of ECM content, prevention of cell apoptosis, facilitation of cell proliferation, induction or prevention of cell autophagy, alleviation of oxidative damage, and adaptation of hypoxic microenvironment. In the current review, we summarize recent progression on activation and negative regulation of the PI3K/Akt signaling pathway, and highlight its impact on IDD. Targeting this pathway could become an attractive therapeutic strategy for IDD in the near future.

In vitro extracellular matrix accumulation of nasal and articular chondrocytes for intervertebral disc repair

Chondrocyte based regenerative therapies for intervertebral disc repair such as Autologous Disc Cell Transplantation (ADCT, CODON) and allogeneic juvenile chondrocyte implantation (NuQu^®, ISTO Technologies) have demonstrated good outcomes in clinical trials. However concerns remain with the supply demand reconciliation and issues surrounding immunoreactivity which exist for allogeneic-type technologies. The use of stem cells is challenging due to high growth factor requirements, regulatory barriers and differentiation towards a stable phenotype. Therefore, there is a need to identify alternative non-disc cell sources for the development and clinical translation of next generation therapies for IVD regeneration. In this study, we compared Nasal Chondrocytes (NC) as a non-disc alternative chondrocyte source with Articular Chondrocytes (AC) in terms of cell yield, morphology, proliferation kinetics and ability to produce key extracellular matrix components under 5% and 20% oxygen conditions, with and without exogenous TGF-β supplementation. Results indicated that NC maintained proliferative capacity with high amounts of sGAG and lower collagen accumulation in the absence of TGF-β supplementation under 5% oxygen conditions. Importantly, osteogenesis and calcification was inhibited for NC when cultured in IVD-like microenvironmental conditions. The present study provides a rationale for the exploration of nasal chondrocytes as a promising, potent and clinically feasible autologous cell source for putative IVD repair strategies.

RNA Sequencing Reveals a Role of TonEBP Transcription Factor in Regulation of Pro-inflammatory Genes in Response to Hyperosmolarity in Healthy Nucleus Pulposus Cells: A HOMEOSTATIC RESPONSE?

Transcription factor tonicity-responsive enhancer-binding protein (TonEBP/NFAT5) is critical for osmo-adaptation and extracellular matrix homeostasis of nucleus pulposus (NP) cells in their hypertonic tissue niche. Recent studies implicate TonEBP signaling in inflammatory disease and rheumatoid arthritis pathogenesis. However, broader functions of TonEBP in the disc remain unknown. RNA sequencing was performed on NP cells with TonEBP knockdown under hypertonic conditions. 1140 TonEBP-dependent genes were identified and categorized using Ingenuity Pathway Analysis. Bioinformatic analysis showed enrichment of matrix homeostasis and cytokine/chemokine signaling pathways. C-C motif chemokine ligand 2 (CCL2), interleukin 6 (IL6), tumor necrosis factor (TNF), and nitric oxide synthase 2 (NOS2) were studied further. Knockdown experiments showed that TonEBP was necessary to maintain expression levels of these genes. Gain- and loss-of-function experiments and site-directed mutagenesis demonstrated that TonEBP binding to a specific site in the CCL2 promoter is required for hypertonic inducibility. Despite inhibition by dominant-negative TonEBP, IL6 and NOS2 promoters were not hypertonicity-inducible. Whole-disc response to hypertonicity was studied in an ex vivo organ culture model, using wild-type and haploinsufficient TonEBP mice. Pro-inflammatory targets were induced by hypertonicity in discs from wild-type but not TonEBP-haploinsufficient mice. Mechanistically, NF-κB activity increased with hypertonicity and was necessary for hypertonic induction of target genes IL6, TNF, and NOS2 but not CCL2 Although TonEBP maintains transcription of genes traditionally considered pro-inflammatory, it is important to note that some of these genes also serve anabolic and pro-survival roles. Therefore, in NP cells, this phenomenon may reflect a physiological adaptation to diurnal osmotic loading of the intervertebral disc.

Association Between Lumbar Disc Degeneration and Propionibacterium acnes Infection: Clinical Research and Preliminary Exploration of Animal Experiment

STUDY DESIGN

Clinical research and animal experiment.

OBJECTIVE

To investigate whether lumbar disc degeneration is associated with Propionibacterium acnes (P acnes) infection.

SUMMARY OF BACKGROUND DATA

The hypothesis that herniated discs may be infected with P acnes by way of bacteremia is remarkable. This may bring a tremendous change in treatment of lumbar disc herniation (LDH). However, this hypothesis is still controversial. Since P acnes isolated may be related to contamination.

METHODS

Nucleus pulposus from 22 patients (30 discs) with lumbar disc herniation was collected during discectomy, following aerobic and anaerobic cultures for 10 days.Twenty-four rabbits were divided into four groups. After L3-L6 being exposed, an incision was made into the three discs in groups A and B. While in groups C and D, two random segments were operated. Six weeks later, 0.05 mL of 5 × 10 CFU/mL P acnes was inoculated into operated discs in group A and sterile physiological saline in group B. In group C, 0.2 mL of 5 × 10 CFU/mL P acnes was injected through ear vein. Sterile saline was used in group D. Six weeks later, MRI was performed. Then, nucleus pulposus and paraspinal muscles were harvested for aerobic and anaerobic cultures.

RESULTS

Clinical research: Anaerobic cultures were positive in three cases: two coagulase-negative staphylococci, one particles chain bacterium. No P acnes was found. Staphylococcus epidermidis was isolated in one aerobic culture.Animal experiment: P acnes was found in 11 out of 18 (61%) discs in group A. There was no P acnes found in the other three groups.

CONCLUSION

Degenerated discs were suitable for P acnes growth. This research did not find the evidence of the symptomatic degenerated lumbar discs infected with P acnes or that P acnes could infect the degenerated lumbar discs by way of bacteremia.

LEVEL OF EVIDENCE

N/A.

Hypoxia regulates sumoylation pathways in intervertebral disc cells: implications for hypoxic adaptations

OBJECTIVE

To explore the hypoxic regulation of sumoylation pathways and cell viability in nucleus pulposus (NP) and annulus fibrosus (AF) cells.

DESIGN

Expression of small ubiquitin-like modifier (SUMO) molecules, SUMO E1 activating enzymes SAE1 and SAE2, SUMO E2 conjugating enzyme UBC9, and de-sumoylation enzyme sentrin/SUMO-specific proteases (SENP)1 was immunolocalized in rat intervertebral disc (IVD) cells. NP and AF cells were cultured in hypoxia and cell viability was evaluated by quantifying cell proliferation, cellular senescence, apoptosis, and cell cycle distribution. Hypoxic regulation of sumoylation pathways was studied by analyzing the transcription and expression of SUMO molecules and sumoylation enzymes. Loss of function study using SENP1 siRNA was performed to investigate the regulatory role of sumoylation on the function of hypoxia inducible factor 1α (HIF-1α) and the hypoxic tolerance of IVD cells.

RESULTS

Sumoylation pathways were expressed in IVD cells and localized predominantly in nuclei. Both NP and AF cells maintained viability under hypoxia and upregulated the expression of SENP1. In NP cells hypoxia transiently increased the expression of SUMO-1, SUMO-2/3, SAE2, and UBC9, whereas SUMO-1 was elevated while SUMO-2/3, SAE1, SAE2, and UBC9 were reduced by low oxygen tensions in AF cells. Although downregulation of SENP1 decreased the transcriptional activity of HIF-1α, the viability of disc cells showed no significant loss under hypoxia.

CONCLUSIONS

NP and AF cells equally tolerate oxygen deficiency, but differently regulate the sumoylation pathways under hypoxia. The distinct sumoylation dynamics may help extend our understanding of the cell-specific regulation of the molecular basis that promotes cell survival in the hypoxic IVD.

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.

High Glucose-Induced Oxidative Stress Mediates Apoptosis and Extracellular Matrix Metabolic Imbalances Possibly via p38 MAPK Activation in Rat Nucleus Pulposus Cells

Objectives. To investigate whether high glucose-induced oxidative stress is implicated in apoptosis of rat nucleus pulposus cells (NPCs) and abnormal expression of critical genes involved in the metabolic balance of extracellular matrix (ECM). Methods. NPCs were cultured with various concentrations of glucose to detect cell viability and apoptosis. Cells cultured with high glucose (25 mM) were untreated or pretreated with N-acetylcysteine or a p38 MAPK inhibitor SB 202190. Reactive oxygen species (ROS) production was evaluated. Activation of p38 MAPK was measured by Western blot. The expression of ECM metabolism-related genes, including type II collagen, aggrecan, SRY-related high-mobility-group box 9 (Sox-9), matrix metalloproteinase 3 (MMP-3), and tissue inhibitor of metalloproteinase 1 (TIMP-1), was analyzed by semiquantitative RT-PCR. Results. High glucose reduced viability of NPCs and induced apoptosis. High glucose resulted in increased ROS generation and p38 MAPK activation. In addition, it negatively regulated the expression of type II collagen, aggrecan, Sox-9, and TIMP-1 and positively regulated MMP-3 expression. These results were changed by pretreatment with N-acetylcysteine or SB 202190. Conclusions. High glucose might promote apoptosis of NPCs, trigger ECM catabolic pathways, and inhibit its anabolic activities, possibly through a p38 MAPK-dependent oxidative stress mechanism.

Grb2 depletion under non-stimulated conditions inhibits PTEN, promotes Akt-induced tumor formation and contributes to poor prognosis in ovarian cancer

In the absence of extracellular stimulation the adaptor protein growth factor receptor-bound protein (Grb2) and the phospholipase Plcγ1 compete for the same binding site on fibroblast growth factor receptor 2 (FGFR2). Reducing cellular Grb2 results in upregulation of Plcγ1 and depletion of the phospholipid PI(4,5)P2. The functional consequences of this event on signaling pathways are unknown. We show that the decrease in PI(4,5)P2 level under non-stimulated conditions inhibits PTEN activity leading to the aberrant activation of the oncoprotein Akt. This results in excessive cell proliferation and tumor progression in a xenograft mouse model. As well as defining a novel mechanism of Akt phosphorylation with important therapeutic consequences, we also demonstrate that differential expression levels of FGFR2, Plcγ1 and Grb2 correlate with patient survival. Oncogenesis through fluctuation in the expression levels of these proteins negates extracellular stimulation or mutation and defines them as novel prognostic markers in ovarian cancer.

NMMHC IIA inhibition impedes tissue factor expression and venous thrombosis via Akt/GSK3β-NF-κB signalling pathways in the endothelium

Non-muscle myosin heavy chain IIA (NMMHC IIA) has been shown to be involved in thrombus formation and inflammatory microparticle release in endothelial cells. However, the role of NMMHC IIA in regulating the expression of tissue factor (TF) and deep venous thrombosis remains to be elucidated. In the present study, endothelial cells were stimulated with tumour necrosis factor-α (TNF-α) to induce TF expression. Pretreatment with the NMMHC II inhibitor blebbistatin suppressed the mRNA and protein expressions as well as the procoagulant activity of TF in a dose-dependent manner. Blebbistatin enhanced Akt and GSK3β phosphorylation and inhibited NF-κB p65 nuclear translocation and IκBα degradation. These observations were similar to the effect of CHIR99021, a GSK3β inhibitor. TF downregulation by blebbistatin was antagonised by the PI3K inhibitor, wortmannin. Furthermore, siRNA knockdown of NMMHC IIA, but not IIB or IIC, inhibited TF expression, activated Akt/GSK3β and suppressed NF-κB signalling pathways, whereas the overexpression of NMMHC IIA increased TF expression. The binding of NMMHC IIA and TNF receptor 2 mediated signal internalisation in TNF-α-stimulated endothelial cells. Importantly, blebbistatin decreased endothelium NMMHC IIA and TF expression, deactivated GSK3β by inducing its phosphorylation, suppressed p65 nuclear translocation, and inhibited thrombus formation in a mouse deep venous thrombosis model.Our findings provide solid evidence that inhibition of NMMHC II, most likely NMMHC IIA, impedes TF expression and venous thrombosis via Akt/GSK3β-NF-κB signalling pathways in the endothelium both in vitro and in vivo. NMMHC IIA might be a potential novel target for the treatment of thrombotic disorders.

Advancing the cellular and molecular therapy for intervertebral disc disease

The healthy intervertebral disc (IVD) fulfils the essential function of load absorption, while maintaining multi-axial flexibility of the spine. The interrelated tissues of the IVD, the annulus fibrosus, the nucleus pulposus, and the cartilaginous endplate, are characterised by their specific niche, implying avascularity, hypoxia, acidic environment, low nutrition, and low cellularity. Anabolic and catabolic factors balance a slow physiological turnover of extracellular matrix synthesis and breakdown. Deviations in mechanical load, nutrient supply, cellular activity, matrix composition and metabolism may initiate a cascade ultimately leading to tissue dehydration, fibrosis, nerve and vessel ingrowth, disc height loss and disc herniation. Spinal instability, inflammation and neural sensitisation are sources of back pain, a worldwide leading burden that is challenging to cure. In this review, advances in cell and molecular therapy, including mobilisation and activation of endogenous progenitor cells, progenitor cell homing, and targeted delivery of cells, genes, or bioactive factors are discussed.

Mitogen-activated protein kinase and Akt pathways are involved in 4-n-nonyphenol induced apoptosis in mouse Sertoli TM4 cells

Nonylphenol (NP) is considered an important environmental toxicant, which may disrupt male reproductive system. The aim of this study was to investigate 4-n-nonylphenol (4-n-NP) induced apoptosis and its related mechanism in mouse Sertoli cell line, TM4 cells. Our results showed that NP treatment (0.1, 1, 10, 20 and 30 μM) decreased cell viability and induced apoptosis in the cells, accompanied by alteration of Bcl-2 family mRNA expression, activation of caspases-3, release of Ca(2+), and increase of reactive oxygen species (ROS) generation. Subsequently, it was found that the levels of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-PX) in the cells were markedly decreased, and maleic dialdehyde (MDA) content was increased by NP treatment. Then activation of the mitogen-activated protein kinases (MAPKs) pathways and inhibition of Akt pathway were simultaneously detected in NP challenged TM4 cells. Taken together, it was concluded that NP induced cytotoxicity and apoptosis in TM4 cells, and the apoptosis may be mediated via MAPKs and Akt pathways in addition to Ca(2+) release and ROS generation.

Roles of FGF-2 and TGF-beta/FGF-2 on differentiation of human mesenchymal stem cells towards nucleus pulposus-like phenotype

Human mesenchymal stem cells (MSCs) are reported to have the capability of differentiating towards nucleus pulposus (NP)-like phenotype under specific culture conditions. So far, the effects of fibroblast growth factor (FGF)-2 and the cocktail effects of transforming growth factor (TGF)-beta and FGF-2 on MSCs remain unclear. Therefore, we designed this study to clarify these effects. MSCs were cultured in conditioned medium containing FGF-2 or TGF-beta/FGF-2, and compared with basal or TGF-beta medium. The groups with FGF-2 showed the increase of cell proliferation. Functional gene markers and novel NP markers decreased in FGF-2 group, together with functional protein expression. Pho-ERK1/2 and pho-Smad3 differed significantly in the two conditioned groups. All these results suggest FGF-2 promotes MSCs' proliferation, synergistically with TGF-beta. However, FGF-2 plays a negative role in cartilage homeostasis. We also demonstrate that FGF-2 has no positive effect in differentiating MSCs into NP-like cells, but hinders the acceleration effect of TGF-beta.

Hypoxia facilitates the survival of nucleus pulposus cells in serum deprivation by down-regulating excessive autophagy through restricting ROS generation

Nucleus pulposus (NP) cells reside in a hypoxic environment in vivo, while the mechanisms of how NP cells maintain survival under hypoxia are not clear. Autophagy is an important physiological response to hypoxia and implicated in the survival regulation in most types of cells. This study was designed to investigate the role of autophagy in the survival of NP cells under hypoxia. We found that appropriate autophagy activity was beneficial to the survival of NP cells in serum deprivation, while excessive autophagy led to death of the NP cells. Hypoxia facilitated the survival of NP cells in serum deprivation by down-regulating excessive autophagy. Hypoxia down-regulated the autophagy activity of NP cells through restricting the production of reactive oxygen species (ROS) and inactivating the AMPK/mTOR signaling pathway, and possibly through a pathway involving HIF-1α. We believed that understanding the autophagy response of NP cells to hypoxia and its role in cell survival had important clinical significance in the prevention and treatment of degenerative discogenic diseases.

Responses and adaptations of intervertebral disc cells to microenvironmental stress: a possible central role of autophagy in the adaptive mechanism

Intervertebral discs comprise the largest avascular cartilaginous organ in the body, and its nutrient condition can be impaired by degeneration, aging and even metabolic disease. The unique microenvironment brings special stresses to various disc cell types, including nucleus pulposus cells, notochordal cells, annulus fibrosus cells and endplate chondrocytes. These cells experience nutrient starvation, acidic stress, hypoxic stress, hyperglycemic stress, osmotic stress and mechanical stress. Understanding the detailed responses and complex adaptive mechanisms of disc cells to various stresses might provide some clues to guide therapy for disc degeneration. By reviewing the published literatures describing disc cells under different hostile microenvironments, we conclude that these cells exhibit different responses to microenvironmental stresses with different mechanisms. Moreover, the interaction and combination of these stresses create a complex environment that synergistically increase or decrease influences on disc cells, compared with the effects of a single stress. Interestingly, most of these stresses activate autophagy, a self-protective mechanism by which dysfunctional protein and organelles are degraded. It is becoming clear that autophagy facilitates the cellular adaptation to stresses and might play a central role in regulating the adaptation of disc cells under stress. Therefore, autophagy modulation might be a potential therapeutic method to treat disc degeneration.

Leptin induces terminal differentiation of rat annulus fibrosus cells via activation of MAPK signaling

Both leptin and its receptor are expressed in rat annulus fibrosus (AF) cells. However, little is known about their role and mechanism during disc degeneration. The mitogen activating protein kinase (MAPK) pathway which mediates leptin-induced terminal differentiation of rat AF cells was analyzed using PCR, Western-blot and immunocytochemistry. It was found that leptin-induced AF cells terminal differentiation, which may be attributed to upregulated p38 and ERK1/2 phosphorylation, however, JNK phosphorylation was not observed. Specific inhibitors of p38 or ERK1/2, but not JNK, could inhibit the stimulative activity of leptin on collagen X and MMP-13 protein levels. This study, for the first time, shows that the MAPK pathway, especially p38 and ERK1/2 signaling, plays a distinct role in leptin-induced AF cells terminal differentiation.

SHH-dependent knockout of HIF-1 alpha accelerates the degenerative process in mouse intervertebral disc

Hypoxia-inducible factor-1alpha (HIF-1 alpha) has been reported to have an important role in the metabolism and synthesis of extracellular matrix of the nucleus pulposus cells (NPCs) and was assumed to be involved in the process of intervertebral disc degeneration. The objective of this study was to investigate the role of HIF-1alpha in disc degeneration in vivo using a conditional HIF-1alpha knockout (KO) mouse model. ShhCre transgenic mice were mated with HIF-1 alpha fl/fl mice to generate conditional HIF-1alpha KO mice (HIF-1alpha fl/fl-ShhCre+). Three mice of each genotype (Wide-type and HIF-1alpha KO) at the age of 3 days, 6, and 12 weeks were sacrificed after genotyping. Five lumbar disc samples were harvested from each mouse, with a total of 45 disc samples for each genotype. In situ hybridization and immunohistochemical analysis were used to check the efficacy of HIF-1alpha knockout. Histological grading of the disc degeneration was performed according to the classification system proposed by Boos et al. Picro-sirius red staining, Safranine O/fast green staining and immunohistochemical study were used to evaluate the expression of aggrecan, type-II collagen and vascular endothelial growth factor (VEGF). Histologic analysis revealed more NPC deaths and signs of degeneration in HIF-1alpha KO mice and the degeneration scores of HIF-1alpha KO mice were significantly higher than those of the Wide-type mice at the age of 6 weeks and 12 weeks. There were less expressions of aggrecan, type-II collagen and VEGF in the intervertebral discs of HIF1-alpha KO mice than in those of wild-type mice. Taken together, the results of our study indicated that HIF-1alpha is a pivotal contributor to NPC survival and the homeotasis of extracellular matrix through the HIF-1alpha/VEGF signaling pathway, and plays an important role in the development of disc degeneration.