Fucoxanthin ameliorates endoplasmic reticulum stress and inhibits apoptosis and alleviates intervertebral disc degeneration in rats by upregulating Sirt1

Endoplasmic reticulum stress (ERS) and apoptosis of nucleus pulposus (NP) cells are considered to be the main pathological factors of intervertebral disc degeneration (IDD). Fucoxanthin (FX), a marine carotenoid extracted from microalgae, has antioxidant, anti-inflammatory, and anticancer properties. The aim of this study was to investigate the effect of FX on NP cells induced by oxidative stress and its molecular mechanism. Primary NP cells of the lumbar vertebrae of rats were extracted and tested in vitro. qRT-PCR, western blot, immunofluorescence, and TUNEL staining were used to detect apoptosis, ERS, extracellular matrix (ECM), and Sirt1-related pathways. In vivo experiments, the recovery of IDD rats was determined by X-ray, hematoxylin and eosin, Safranin-O/Fast Green, Alcian staining, and immunohistochemistry. Our study showed that oxidative stress induced ERS, apoptosis, and ECM degradation in NP cells. After the use of FX, the expression of Sirt1 was up-regulated, the activation of PERK-eIF2α-ATF4-CHOP was decreased, and apoptosis and ECM degradation were decreased. At the same time, FX improved the degree of disc degeneration in rats in vivo. Our study demonstrates the effect of FX on improving IDD in vivo and in vitro, suggesting that FX may be a potential drug for the treatment of IDD.

Injectable, self-healing hydrogels based on gelatin, quaternized chitosan, and laponite as localized celecoxib delivery system for nucleus pulpous repair

Utilization of injectable hydrogels stands as a paradigm of minimally invasive intervention in the context of intervertebral disc degeneration treatment. Restoration of nucleus pulposus (NP) function exerts a profound influence in alleviating back pain. This study introduces an innovative class of injectable shear-thinning hydrogels, founded on quaternized chitosan (QCS), gelatin (GEL), and laponite (LAP) with the capacity for sustained release of the anti-inflammatory drug, celecoxib (CLX). First, synthesis of Magnesium-Aluminum-Layered double hydroxide (LDH) was achieved through a co-precipitation methodology, as a carrier for celecoxib and a source of Mg ions. Intercalation of celecoxib within LDH layers (LDH-CLX) was verified through a battery of analytical techniques, including FTIR, XRD, SEM, EDAX, TGA and UV-visible spectroscopy confirmed a drug loading efficiency of 39.22 ± 0.09 % within LDH. Then, LDH-CLX was loaded in the optimal GEL-QCS-LAP hydrogel under physiological conditions. Release behavior (15 days profile), mechanical properties, swelling ratio, and degradation rate of the resulting composite were evaluated. A G* of 15-47 kPa was recorded for the hydrogel at 22-40 °C, indicating gel stability in this temperature range. Self-healing properties and injectability of the composite were proved by rheological measurements. Also, ex vivo injection into intervertebral disc of sheep, evidenced in situ forming and NP cavity filling behavior of the hydrogel. Support of GEL-QCS-LAP/LDH-CLX (containing mg2+ ions) for viability and proliferation (from ~94 % on day 1 to ~134 % on day 7) of NP cells proved using MTT assay, DAPI and Live/Dead assays. The hydrogel could significantly upregulate secretion of glycosaminoglycan (GAG, from 4.68 ± 0.1 to 27.54 ± 1.0 μg/ml), when LHD-CLX3% was loaded. We conclude that presence of mg2+ ion and celecoxib in the hydrogel can lead to creation of a suitable environment that encourages GAG secretion. In conclusion, the formulated hydrogel holds promise as a minimally invasive candidate for degenerative disc repair.

Cyanidin attenuates the apoptosis of rat nucleus pulposus cells and the degeneration of intervertebral disc via the JAK2/STAT3 signal pathway in vitro and in vivo

CONTEXT

Cyanidin has been shown to have therapeutic potential in osteoarthritis. However, it is unclear whether cyanidin prevents the progression of intervertebral disc degeneration (IVDD).

OBJECTIVE

This study evaluates the effects of cyanidin on IVDD in vitro and in vivo.

MATERIALS AND METHODS

Nucleus pulposus cells (NPCs) isolated from lumbar IVD of 4-week-old male Sprague-Dawley (SD) rats were exposed to 20 ng/mL IL-1β, and then treated with different doses (0-120 µM) of cyanidin for 24 h. SD rats were classified into three groups (n = 8) and treated as follows: control (normal saline), IVDD (vehicle), IVDD + cyanidin (50 mg/kg). Cyanidin was administered intraperitoneally for 8 weeks.

RESULTS

The IC₅₀ of cyanidin for NPCs was 94.78 µM, and cyanidin had no toxicity at concentrations up to 500 mg/kg in SD rats. Cyanidin inhibited the apoptosis of NPCs induced by IL-1β (12.73 ± 0.61% vs. 18.54 ± 0.60%), promoted collagen II (0.82-fold) and aggrecan (0.81-fold) expression, while reducing MMP-13 (1.02-fold) and ADAMTS-5 (1.40-fold) expression. Cyanidin increased the formation of autophagosomes in IL-1β-induced NPCs, and promoted LC3II/LC3I (0.83-fold) and beclin-1 (0.85-fold) expression, which could be reversed by chloroquine. Cyanidin inhibited the phosphorylation of JAK2 (0.47-fold) and STAT3 (0.53-fold) in IL-1β-induced NPCs. The effects of cyanidin could be enhanced by AG490. Furthermore, cyanidin mitigated disc degeneration in IVDD rats in vivo.

DISCUSSION AND CONCLUSIONS

Cyanidin improved the function of NPCs in IVDD by regulating the JAK2/STAT3 pathway, which may provide a novel alternative strategy for IVDD. The mechanism of cyanidin improving IVDD still needs further work for in-depth investigation.

Does oseltamivir protect human chondrocyte and nucleus pulposus cells from degeneration by inhibiting senescence and proinflammation mediated by the NLRP3 inflammasome and NF-κB?

OBJECTIVE

Recent drug design studies suggest that inflammation is among the most important factors in the development of both intervertebral disc (IVD) degeneration (IVDD) and osteoarthritis (OA) due to cartilage damage. This study aimed to investigate whether the anti-inflammatory drug oseltamivir has a toxic effect on IVD and cartilage tissue cells. It assessed what effect oseltamivir has on hypoxia-inducible factor (HIF)-1 alpha (HIF1α), which plays an important role in anabolic pathways in IVD and cartilage tissue. In addition, the study analyzed whether oseltamivir could inhibit the release of inflammatory interleukin-1 beta (IL-1β) via the nuclear factor kappa-B (NF-κB) signaling pathway by activating the nucleotide-binding oligomerization domain and leucine-rich repeat protein-3 (NLRP3) inflammasome.

MATERIALS AND METHODS

Human lumbar IVD (n = 8) tissues were isolated for annulus fibrosus (AF) and nucleus pulposus (NP) primary cell cultures, and human tibial and femoral cartilage tissues (n = 8) were isolated for primary chondrocyte cultures. Untreated groups served as the control and oseltamivir-treated groups as the study sample. Cell viability and cytotoxicity were evaluated at 0, 24, 48, and 72 h in all groups for changes in HIF-1α, IL-1β, NF-κB, and the NLRP3-inflammasome protein expressions using Western blotting. The α significance value was < 0.05.

RESULTS

In the oseltamivir-treated groups, cell proliferation decreased in both AF/NP cell and chondrocyte cultures obtained from IVD cartilage tissues. After Western blotting analysis, changes were observed in the protein expressions of HIF-1α, IL-1β, NF-κB, and the NLRP3 inflammasome in both AF/NP cells and chondrocytes. The results were statistically significant (p < 0.05).

CONCLUSIONS

Oseltamivir treatment may be a promising regenerative strategy to manage IVDD and osteoarthritic cartilage tissues.

Tanshinone IIA and Astragaloside IV Inhibit miR-223/JAK2/STAT1 Signalling Pathway to Alleviate Lipopolysaccharide-Induced Damage in Nucleus Pulposus Cells

Astragaloside IV (AS IV) and tanshinone (TS IIA) are the main natural components of Salvia miltiorrhiza and Radix Astragali, respectively. The amalgam of TS IIA and AS IV has potential therapeutic value in many inflammation-related diseases. However, the aftereffect of TS IIA and AS IV for lumbar disc herniation is not clear. Although the function of miR-223 in the inflammation-related JAK/STAT pathway is unknown, it is particularly expressed in human degenerative nucleus pulposus cells. This study has investigated the efficacy of the combined application of TS IIA and AS IV in the treatment of intervertebral disc nucleus pulposus cells (NP cells) injured by lipopolysaccharide (LPS). After miR-223 inhibitor imitated NP cells, the state of the JAK family and STAT family was recognized by Western blotting (Western blot, WB) and reverse transcriptase quantitative polymerase chain reaction (qPCR). The shRNA lentivirus interference vector targeting the STAT family was constructed, and the NP cell line stably interfering with the STAT gene was established after transfection. The expression of TNF-α, IL-6, MMP-9, MMP-3, caspase-1, and caspase-3 was detected by lipopolysaccharide (WTNP cells), control virus NP cells, STAT downregulation NP cells, enzyme-linked immunosorbent assay (ELISA), Western blot, and qPCR, respectively. The cell survival rate was detected by flow cytometry and TUNEL staining reverse transcriptase-polymerase chain reaction (qPCR). NP cells were treated with TS IIA and AS IV which had been made into different concentrations, and then, the expression of miR-223, p-STAT1, and p-JAK families was detected by WB Western blotting and qPCR. MiR-223 selectively acts on JAK2/STAT1 pathway, increases the expression of TNF-α, IL-6, MMP-9, MMP-3, caspase3-1, and caspase-3, and induces apoptosis, which can be eliminated by silencing STAT1. TS IIA combined with AS IV could inhibit the expression of miR-223, p-STAT1, and p-JAK2 in NP cells, and they showed a dose-dependent tendency to p-STAT1 and p-JAK2. This study shows that miR-223 promotes the inflammatory response and induces cell injury of NP cells by acting on the JAK2/STAT1 pathway, and the combination of TS IIA and AS IV may protect NP cells by downregulating miR-223 and inhibiting the expression of JAK2 and STAT1.

MicroRNA‑25 protects nucleus pulposus cells against apoptosis via targeting SUMO2 in intervertebral disc degeneration

It has been reported that microRNA (miRNA/miR)‑25 is downregulated in patients with intervertebral disc degeneration (IVDD). However, the potential role of miR‑25 in IVDD remains unclear. Therefore, the present study aimed to investigate the effects of miR‑25 on human intervertebral disc nucleus pulposus cells (NPCs). The expression levels of miR‑25 and those of small ubiquitin‑related modifier 2 (SUMO2) were determined in human nucleus pulposus (NP) tissues by reverse transcription‑quantitative PCR (RT‑qPCR) and western blot analyses. Subsequently, the potential interaction between miR‑25 and SUMO2 was validated via dual‑luciferase reporter assay and RNA pull‑down assay with biotinylated miRNA. The effects of miR‑25 on NPC proliferation and apoptosis were evaluated using Cell Counting Kit‑8 assay, 5‑ethynyl‑2'‑deoxyuridine incorporation assay, and flow cytometry. The results showed that miR‑25 was downregulated in patients with IVDD. In addition, miR‑25 increased the proliferation of NPCs and inhibited their apoptosis. Furthermore, the current study verified that miR‑25 could directly target SUMO2 and regulate its expression via the p53 signaling pathway. Additionally, the effects of miR‑25 on NPCs were abrogated following SUMO2 overexpression. Overall, the results of the present study demonstrated that miR‑25 could promote the proliferation and inhibit the apoptosis of NPCs via targeting SUMO2, suggesting that miR‑25 may be a potential target in the treatment of IVDD.

Ozone as Modulator of Resorption and Inflammatory Response in Extruded Nucleus Pulposus Herniation. Revising Concepts

Ozone therapy has been used to treat disc herniation for more than four decades. There are several papers describing results and mechanism of action. However, it is very important to define the characteristics of extruded disc herniation. Although ozone therapy showed excellent results in the majority of spinal diseases, it is not yet fully accepted within the medical community. Perhaps it is partly due to the fact that, sometimes, indications are not appropriately made. The objective of our work is to explain the mechanisms of action of ozone therapy on the extruded disc herniation. Indeed, these mechanisms are quite different from those exerted by ozone on the protruded disc herniation and on the degenerative disc disease because the inflammatory response is very different between the various cases. Extruded disc herniation occurs when the nucleus squeezes through a weakness or tear in the annulus. Host immune system considers the nucleus material to be a foreign invader, which triggers an immune response and inflammation. We think ozone therapy modulates this immune response, activating macrophages, which produce phagocytosis of extruded nucleus pulposus. Ozone would also facilitate the passage from the M1 to M2 phase of macrophages, going from an inflammatory phase to a reparative phase. Further studies are needed to verify the switch of macrophages.

Platelet-rich plasma attenuates intervertebral disc degeneration via delivering miR-141-3p-containing exosomes

Oxidative stress mediated apoptotic and pyroptotic cell death contributes to intervertebral disc (IVD) degeneration, and platelet-rich plasma (PRP) exerts protective effects to attenuate IVD degeneration. Hence, the present study aimed to validate this issue and uncover the potential underlying mechanisms. The mice and cellular models for IVD degeneration were established by using puncture method and H2O2 exposure, respectively, and we evidenced that NLRP3-mediated cell pyroptosis, apoptosis and inflammatory responses occurred during IVD degeneration progression in vitro and in vivo. Then, the PRP-derived exosomes (PRP-exo) were isolated and purified, and we noticed that both PRP-exo and ROS scavenger (NAC) reversed the detrimental effects of H2O2 treatment on the nucleus pulposus (NP) cells. Further results supported that PRP-exo exerted its protective effects on H2O2 treated NP cells by modulating the Keap1-Nrf2 pathway. Mechanistically, PRP-exo downregulated Keap1, resulting in the release of Nrf2 from the Keap1-Nrf2 complex, which further translocated from cytoplasm to nucleus to achieve its anti-oxidant biological functions, and H2O2 treated NP cells with Nrf2-deficiency did not respond to PRP-exo treatment. In addition, miR-141-3p was enriched in PRP-exo, and miR-141-3p targeted the 3' untranslated region (3'UTR) of Keap1 mRNA for its degradation, leading to Nrf2 translocation. Furthermore, overexpression of miR-141-3p ameliorated the cytotoxic effects of H2O2 on NP cells, which were abrogated by upregulating Keap1 and silencing Nrf2. Taken together, we concluded that PRP secreted exosomal miR-141-3p to activate the Keap1-Nrf2 pathway, which helped to slow down IVD degeneration.

MiRNA-495-3p Attenuates TNF-α Induced Apoptosis and Inflammation in Human Nucleus Pulposus Cells by Targeting IL5RA

Intervertebral disc degeneration (IVDD) is considered to be the fundamental cause of the occurrence and development of lumbar disc herniation (LDH). The degeneration of IVDD is mainly caused by the participation of inflammatory factors. Thus, it is of great significance to analyze the pathogenesis of IVDD, which may guide clinical prevention and treatment of LDH. Our current study aims to identify the role of miR-495-3p in LDH and to further unravel the underlying mechanisms. Results in the current study showed that TNF-α treatment markedly inhibited cell viability of HNPC, increased the IL-1β level, and decreased the mRNA level of miR-495-3p in HNPC in a time-dependent manner. Up-regulation of miR-495-3p promoted cell proliferation and inhibited inflammation and apoptosis in TNF-α-induced HNPCs. To investigate the underlying molecular mechanism through which miR-495-3p regulates TNF-α-induced inflammation and apoptosis in HNPCs, we explored the possible target gene of miR-495-3p. Bioinformatics analysis indicated that IL5RA, which is an important gene for TNF-α-induced HNPC injury, was also a target gene of miR-495-3p. A luciferase reporter assay was applied to test and verify the direct target association between miR-495-3p and IL5RA. The results discovered that down-regulation of miR-495-3p markedly reversed the anti-apoptosis and anti-inflammation of sh-IL5RA. In short, the present study evaluated the roles of miR-495-3p and IL5RA in IVDD development and progression. All the data indicated that miRNA-495-3p may play a protective role via inhibiting inflammation and apoptosis in human nucleus pulposus cells by targeting IL5RA pathway. Therefore, miRNA-495-3p may be a potential agent for LDH, and our study may provide a novel strategy in LDH treatment.

Morin attenuates pyroptosis of nucleus pulposus cells and ameliorates intervertebral disc degeneration via inhibition of the TXNIP/NLRP3/Caspase-1/IL-1β signaling pathway

Intervertebral disc degeneration (IDD) is a major cause of lower back pain (LBP), a condition that causes a heavy economic burden globally. The production of cytokines, including interleukin (IL)-1β and tumor necrosis factor (TNF) α, is increased in the degenerating intervertebral disc. Thioredoxin-interacting protein (TXNIP) participates in NLRP3 inflammasome-dependent pyroptosis in liver. Therefore, we hypothesized that TXNIP maypromote pyroptosis via NLRP3/Caspase-1/IL-1β signaling pathway in nucleus pulposus (NP) cell. This study examined the effects of TXNIP on IDD, explored the underlying mechanisms of action and find Morin which is the inhibitor of TXNIP can attenuates pyroptosis of nucleus pulposus cells and ameliorates intervertebral disc degeneration. Our findings indicate that TXNIP promote pyroptosis via NLRP3/Caspase-1/IL-1β signaling pathway in NP cell. Morin considerably inhibited the TXNIP/NLRP3/Caspase-1 signaling pathway in vitro. In vivo. Our data show that TXNIP can aggravates intervertebral disc degeneration and morin may be a useful therapeutic agent for IDD.

Augmented Chondroitin Sulfate Proteoglycan Has Therapeutic Potential for Intervertebral Disc Degeneration by Stimulating Anabolic Turnover in Bovine Nucleus Pulposus Cells under Changes in Hydrostatic Pressure

Nucleus pulposus (NP) cells are exposed to changes in hydrostatic pressure (HP) and osmotic pressure within the intervertebral disc. We focused on main disc matrix components, chondroitin sulfate proteoglycan (CSPG) and hyaluronan (HA) to elucidate the capability of augmented CSPG to enhance the anabolism of bovine NP (bNP) cells under repetitive changes in HP at high osmolality. Aggrecan expression with CSPG in the absence of HP was significantly upregulated compared to the no-material control (phosphate buffer saline) under no HP at 3 days, and aggrecan expression with CSPG under HP was significantly higher than the control with HA under HP at 12 days. Collagen type I expression under no HP was significantly lower with CSPG than in controls at 3 days. Although matrix metalloproteinase 13 expression under HP was downregulated compared to no HP, it was significantly greater with HA than the control and CSPG, even under HP. Immunohistology revealed the involvement of mechanoreceptor of transient receptor potential vanilloid-4 activation under HP, suggesting an HP transduction mechanism. Addition of CSPG had anabolic and anti-fibrotic effects on bNP cells during the early culture period under no HP; furthermore, it showed synergy with dynamic HP to increase bNP-cell anabolism at later time points.

TRIM21 drives intervertebral disc degeneration induced by oxidative stress via mediating HIF-1α degradation

The onset and progression of intervertebral disc degeneration (IVDD) is strictly associated with oxidative stress. TRIM21 (Tripartite motif-containing protein 21), a ubiquitin E3 ligase, has been shown to play an essential role in liver redox homeostasis; however, whether TRIM21 is involved in IVDD, especially in oxidative stress-induced IVDD, is unknown. Here, we reported that TRIM21 was upregulated in nucleus pulposus (NPs) with increasing severity of IVDD, and that oxidative stress was a stimulator of TRIM21 expression. Furthermore, we found that TRIM21 deficiency significantly protected NP cells from degeneration induced by oxidative stress as well as ameliorated disc degeneration in aged mice. Mechanistically, TRIM21 facilitated NP cells degeneration induced by oxidative stress via HIF-1α. TRIM21 could physically interact with HIF-1α and facilitated its degradation via its ubiquitylating activity. Taken together, these findings revealed that TRIM21 drived IVDD induced by oxidative stress by increasing HIF-1α degradation. These findings implicates the potential of TRIM21 as a therapeutic target in IVDD, especially in oxidative stress-induced IVDD.

Neuropeptide Y prevents nucleus pulposus cells from cell apoptosis and IL‑1β‑induced extracellular matrix degradation

Intervertebral disc degeneration (IDD) is characterized by excessive inflammatory reaction, and neuropeptide Y (NPY) was reported to have anti-inflammatory effect. However, the effect of NPY on NP cells has not been investigated up to date. This study aimed to clarify the role of NPY on the process of IDD. Fourteen fresh human lumbar intervertebral discs were harvested, and degeneration-related proteins were examined. Pfirrmann grading system was used to evaluate IDD. Rat nucleus pulposus (NP) cells were used to investigate the effect of NPY on the proliferation, apoptosis, and extracellular matrix (ECM) in NP cell induced by IL-1βin vitro. The expression levels of NPY and its receptors (type 1 receptor, Y1R, and type 2 receptor, Y2R) were detected via immunohistochemical analysis, western blot, and quantitative real-time polymerase chain reaction (qRT-PCR). Cell viability and proliferation were explored using cell counting kit-8 assay, western blot, and immunofluorescence analysis. Cell apoptosis was investigated by Hoechst staining, JC-1 Staining, annexin V-FITC/PI double staining, and western blot. The secretion of NPY from NP cells was determined via enzyme-linked immunosorbent assay (ELISA). The expression of anabolic and catabolic gene was analyzed by qRT-PCR, western blot, immunofluorescence analysis, and ELISA. The expression of Y2R was significantly increased in both human degenerative intervertebral discs and IL-1β-induced NP cells. Although no positive results for NPY indicated by western blot both in vivo and in vitro, ELISA results demonstrated that the secretion of NPY from NP cells was increased by low-concentration IL-1β, but was decreased when the concentration of IL-1β was 30 ng/ml and above. In addition, NPY could promote NP cells proliferation and protect NP cells against IL‑1β‑induced apoptosis via suppressing mitochondrial-mediated apoptosis pathway. What's more, NPY can suppress the expression of catabolic gene and ameliorate IL-1β- induced matrix degeneration in NP cells. In conclusion, NPY could promote NP cell proliferation and alleviate IL‑1β‑induced cell apoptosis via mitochondrial pathway. In addition, NPY can suppress the expression of ECM‑catabolic proteinases and ameliorate IL-1β- induced ECM degeneration in vitro.

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.

Involvement of oxidative stress-induced annulus fibrosus cell and nucleus pulposus cell ferroptosis in intervertebral disc degeneration pathogenesis

Ferroptosis is a necrotic form of regulated cell death that was associated with lipid peroxidation and free iron-mediated Fenton reactions. It has been reported that iron deficiency had been implicated in the pathogenesis of intervertebral disc degeneration (IVDD) by activating apoptosis. However, the role of ferroptosis in the process of IVDD has not been illuminated. Here, we demonstrate the involvement of ferroptosis in IVDD pathogenesis. Our in vitro models show the changes in protein levels of ferroptosis marker and enhanced lipid peroxidation level during oxidative stress. Safranin O staining, hematoxylin-eosin staining, and immunohistochemical were used to assess the IVDD after 8 weeks of surgical procedure in vivo. Treatment with ferrostatin-1, deferoxamine, and RSL3 demonstrate the role of ferroptosis in tert-butyl hydroperoxide (TBHP)-treated annulus fibrosus cells (AFCs) and nucleus pulposus cells (NPCs). Ferritinophagy, nuclear receptor coactivator 4 (NCOA4)-mediated ferritin selective autophagy, is originated during the process of ferroptosis in response to TBHP treatment. Knockdown and overexpression NCOA4 further prove TBHP may induce ferroptosis of AFCs and NPCs in an autophagy-dependent way. These findings support a role for oxidative stress-induced ferroptosis in the pathogenesis of IVDD.

Expression and role of Sphingosine 1-phosphate receptors in intervertebral disc degeneration

BACKGROUND

IVD degeneration is a widespread problem all over the world, which a variety of inflammatory cytokines have been implicated in, while Sphingosine 1-phosphate (S1P) is an important lipid mediator that may play a role in IVD degeneration.

OBJECTIVE

To study the expression and role of S1PRs in the intervertebal disc (IVD) degeneration to enhance understanding of disc degeneration.

METHODS

Degenerated and normal IVD were harvested from patients through surgery. Expression of S1P receptor subtypes was evaluated using real-time PCR, immunohistochemistry, and western blotting. The effect of S1PR on inflammation induced by interleukin-1β in nucleus pulposus (NP) cells was also assessed by real time PCR and western blotting.

RESULTS

The nucleus pulposus mainly expressed the S1PR1/2/3, and the expression decreased in the severe degenerated nucleus pulposus cells. The ligand, S1P, inhibited the up-regulation of matrix metallopeptidase-3 (MMP-3) and ADAM metallopeptidase with thrombospondin type 1 motif 4 (ADAMTS4) induced by IL-1β.

CONCLUSIONS

The results show that an the expression of S1PRs in degenerative discs is down-regulated as degeneration, and S1P can inhibit the inflammation response induced by IL-1β in NP cells, implicating that S1P/S1PR may contribute to IVD degeneration.

Avidin grafted dextran nanostructure enables a month-long intra-discal retention

Low back pain is often the direct result of degeneration of the intervertebral disc. A wide range of therapeutics including anti-catabolic, pro-anabolic factors and chemo-attractants that can stimulate resident cells and recruit endogenous progenitors are under consideration. The avascular nature and the dense matrix of this tissue make it challenging for systemically administered drugs to reach their target cells inside the nucleus pulposus (NP), the central gelatinous region of the intervertebral disc (IVD). Therefore, local intra-discal injection of therapeutic drugs directly into the NP is a clinically relevant delivery approach, however, suffers from rapid and wide diffusion outside the injection site resulting in short lived benefits while causing systemic toxicity. NP has a high negative fixed charge density due to the presence of negatively charged aggrecan glycosaminoglycans that provide swelling pressures, compressive stiffness and hydration to the tissue. This negative fixed charge density can also be used for enhancing intra-NP residence time of therapeutic drugs. Here we design positively charged Avidin grafted branched Dextran nanostructures that utilize long-range binding effects of electrostatic interactions to bind with the intra-NP negatively charged groups. The binding is strong enough to enable a month-long retention of cationic nanostructures within the NP following intra-discal administration, yet weak and reversible to allow movement to reach cells dispersed throughout the tissue. The branched carrier has multiple sites for drug conjugation and can reduce the need for multiple injections of high drug doses and minimize associated side-effects, paving the way for effective clinical translation of potential therapeutics for treatment of low back pain and disc degeneration.

Duhuo jisheng decoction suppresses matrix degradation and apoptosis in human nucleus pulposus cells and ameliorates disc degeneration in a rat model

ETHNOPHARMACOLOGICAL RELEVANCE

The lower back pain (LBP) caused by intervertebral disc (IVD) degeneration brings a heavy burden to society. A classic treatment method of Chinese medicine, fangji-duhuo jisheng decoction (DHJSD), has been effective in the clinical treatment of LBP, although the underlying mechanism remains unknown.

AIM OF THE STUDY

In this work, the main objective was to study the effects of DHJSD on in vitro IVD degeneration of human nucleus pulposus (NP) cells after pressure treatment and on an in vivo interrupted IVD degeneration rat model.

MATERIALS AND METHODS

The effects of DHJSD on the viability of NP cells were detected using Cell Counting Kit-8. RT-qPCR, western blotting, TUNEL assay, transmission electron microscopy, and immunofluorescence staining were performed to explore the molecular mechanism underlying protection against compression-induced matrix degradation and apoptosis in NP cells by DHJSD. Furthermore, the effects of DHJSD on IVD degeneration in a rat IDD model were also determined.

RESULTS

We found that DHJSD increased the viability of NP cells in a concentration- and time-dependent manner. Furthermore, DHJSD significantly reduced compression-induced NP matrix degeneration and apoptosis, activated autophagy, and inhibited the p38/MAPK signaling pathway in NP cells subjected to compression. Autophagy inhibitor 3-MA and p38/MAPK signaling pathway activator anisomycin reversed the beneficial effects of DHJSD in NP cells, indicating that DHJSD protects against IVD degeneration by autophagy activation and P38/MAPK signaling pathway inhibition. Furthermore, DHJSD treatment effectively delayed IVD degeneration in a puncture-induced IDD rat model.

CONCLUSIONS

DHJSD prevents compression-induced matrix degradation and cell apoptosis through regulating autophagy and the P38/MAPK signaling pathway. The mechanism underlying the effects of DHSJD elucidated in this study provides a new direction for LBP treatment.

Ginsenoside Rd inhibits IL-1β-induced inflammation and degradation of intervertebral disc chondrocytes by increasing IL1RAP ubiquitination

Many compounds of ginsenosides show anti-inflammatory properties. However, their anti-inflammatory effects in intervertebral chondrocytes in the presence of inflammatory factors have never been shown. Increased levels of pro-inflammatory cytokines are generally associated with the degradation and death of chondrocytes; therefore, finding an effective and nontoxic substance that attenuates the inflammation is worthwhile. In this study, chondrocytes were isolated from the nucleus pulposus tissues, and the cells were treated with ginsenoside compounds and IL-1β, alone and in combination. Cell viability and death rate were assessed by CCK-8 and flow cytometry methods, respectively. PCR, western blot, and immunoprecipitation assays were performed to determine the mRNA and protein expression, and the interactions between proteins, respectively. Monomeric component of ginsenoside Rd had no toxicity at the tested range of concentrations. Furthermore, Rd suppressed the inflammatory response of chondrocytes to interleukin (IL)-1β by suppressing the increase in IL-1β, tumor necrosis factor (TNF)-α, IL-6, COX-2, and inducible nitric oxide synthase (iNOS) expression, and retarding IL-1β-induced degradation of chondrocytes by improving cell proliferation characteristics and expression of aggrecan and COL2A1. These protective effects of Rd were associated with ubiquitination of IL-1 receptor accessory protein (IL1RAP), blocking the stimulation of IL-1β to NF-κB. Bioinformatics analysis showed that NEDD4, CBL, CBLB, CBLC, and ITCH most likely target IL1RAP. Rd increased intracellular ITCH level and the amount of ITCH attaching to IL1RAP. Thus, IL1RAP ubiquitination promoted by Rd is likely to occur by up-regulation of ITCH. In summary, Rd inhibited IL-1β-induced inflammation and degradation of intervertebral disc chondrocytes by increasing IL1RAP ubiquitination.

Core-Shell-Shell Nanoparticles for NIR Fluorescence Imaging and NRET Swelling Reporting of Injectable or Implantable Gels

Injectable gels that support load are desirable for restoring the mechanical properties of degenerated load-bearing tissue. As these gels become increasingly sophisticated, the need to remotely image them and monitor their swelling increases. However, imaging such gels and monitoring their swelling using noninvasive means is challenging. Here, we use a very low concentration of near-infrared (NIR) core-shell-shell (CSS) reporter nanoparticles to both image and monitor swelling changes of two load-supporting gels. The load-supporting injectable gel consisted of covalently interlinked pH-responsive microgel (MG) particles. The latter gel was not cytotoxic and is termed a doubly cross-linked microgel (DX MG). Inclusion of a complementary fluorescent dye enabled ratiometric monitoring of gel swelling changes in response to pH via nonradiative resonance energy transfer (NRET). In addition, changes in the CSS nanoparticle emission intensity provided a NIR-only method that could also be used to monitor gel swelling. The gel was able to be imaged using NIR light, after being subcutaneously injected into a tissue model. To demonstrate versatility of our approach, CSS and the dye were included within a model implantable gel (poly(acrylamide/acrylic acid)) and fluorescent detection of swelling investigated. Because the concentrations of the reporting species were too low to affect the mechanical properties, our approach to remote gel imaging and swelling monitoring has good potential for application in injectable gels and implants.

Highly compressive and stretchable poly(ethylene glycol) based hydrogels synthesised using pH-responsive nanogels without free-radical chemistry

Poly(ethylene glycol) (PEG) based hydrogels are amongst the most studied synthetic hydrogels. However, reports on PEG-based hydrogels with high mechanical strength are limited. Herein, a class of novel, well-defined PEG-based nanocomposite hydrogels with tunable mechanical strength are synthesised via ring-opening reactions of diglycidyl ethers with carboxylate ions. The pH responsive crosslinked polyacid nanogels (NG) in the dispersed phase act as high functionality crosslinkers which covalently bond to the poly(ethylene glycol) diglycidyl ethers (PEGDGE) as the continuous matrix. A series of NG-x-PEG-y-z gels are prepared where x, y and z are concentrations of NGs, PEGDGE and the PEGDGE molecular weight, respectively. The hydrogel compositions and nano-structural homogeneity of the NGs have strong impact on the enhancement of mechanical properties which enables property tuning. Based on this design, a highly compressive PEG-based nanocomposite hydrogel (NG-13-PEG-20-6000) exhibits a compressive stress of 24.2 MPa, compressive fracture strain greater than 98% and a fracture energy density as high as 1.88 MJ m-3. The tensile fracture strain is 230%. This is amongst one of the most compressive PEG-based hydrogels reported to-date. Our chemically crosslinked gels are resilient and show highly recoverable dissipative energy. The cytotoxicity test shows that human nucleus pulposus (NP) cells remained viable after 8 days of culture time. The overall results highlight their potential for applications as replacements for intervertebral discs or articular cartilages.

Polydatin suppresses nucleus pulposus cell senescence, promotes matrix homeostasis and attenuates intervertebral disc degeneration in rats

Intervertebral disc degeneration (IVDD) is one of the major causes of low back pain. Polydatin (PD) has been shown to exert multiple pharmacological effects on different diseases; here, we test the therapeutic potential of PD for IVDD. In in-vitro experiments, we confirmed PD is nontoxic to nucleus pulposus cells (NPCs) under the concentration of 400 μmol/L. Furthermore, PD was able to decrease the level of senescence in TNF-α-treated NPCs, as indicated by β-gal staining as well as senescence markers p53 and p16 expression. In the aspect of extracellular matrix (ECM), PD not only reduced metalloproteinase 3 (MMP-3), metalloproteinase 13 (MMP-13) and a disintegrin-like and metalloproteinase thrombospondin type 1 motif 4 (ADAMTS-4) expression, but also increased aggrecan and collagen II levels. Mitochondrion is closely related to cellular senescence and ECM homeostasis; mechanistically, we found PD may rescue TNF-α-induced mitochondrial dysfunction, and it may also promote Nrf2 expression and activity. Silencing Nrf2 partly abolished the protective effects of PD on mitochondrial homeostasis, senescence and ECM homeostasis in TNF-α-treated NPCs. Correspondingly, PD ameliorated IVDD in rat model by promoting Nrf2 activity, preserving ECM and inhibiting senescence in nucleus pulposus cells. To sum up, our study suggests that PD exerts protective effects in NPCs against IVDD and reveals the underlying mechanism of PD on Nrf2 activation in NPCs.

Honokiol alleviates the degeneration of intervertebral disc via suppressing the activation of TXNIP-NLRP3 inflammasome signal pathway

Intervertebral disc degeneration (IVDD) is a multifactorial disease and responsible for many spine related disorders, causes disability in the workforce and heavy social costs all over the world. Honokiol, a low molecular weight natural product, could penetrate into and distribute in IVDs to achieve therapeutic effect in a rat tail model. Therefore, the present study was undertaken to examine the antiinflammatory, antioxidation and IVD-protective effect of honokiol using nucleus pulposus cells and investigate its mechanisms to provide a new basis for future clinical treatment of IVDD. In the current study, we demonstrated that honokiol inhibits the H₂O₂-induced apoptosis (caspase-9, caspase-3, and bax), levels of oxidative stress mediators (ROS, MDA), expression of inflammatory mediators (Interleukin-6, COX-2, and iNOS), major matrix degrading proteases (MMP-3, MMP-13, ADAMTS5, and ADAMTS4) associated with nucleus pulposus degradation. Furthermore, we found nucleus pulposus protective ability of honokiol by up-regulating extra cellular matrix anabolic factors like type II collagen (Col II) and SOX9 in nucleus pulposus. We also found that honokiol suppressed the phosphorylation of NF-kB and JNK, and activation of TXNIP-NLRP3 inflammasome in H₂O₂-stimulated nucleus pulposus cells, thereby inhibiting the activation of downstream inflammatory mediators such as Interleukin-1β. Furthermore, honokiol showed a cartilage protective effect in the progression of IVDD in a rat model induced by puncture. Thus, our results demonstrate that honokiol inhibited the H₂O₂ induced apoptosis, oxidative stress, and inflammatory responses through the depression of TXNIP/NLRP3/caspase-1/ Interleukin - 1β signaling axis and the activation of NF-kB and JNK. Honokiol possess nucleus pulposus protective properties and may be of value in suppressing the pathogenesis of IVDD.

Melatonin resists oxidative stress-induced apoptosis in nucleus pulposus cells

AIMS

Intervertebral disc degeneration (IVDD) is thought to be the major cause of low back pain (LBP), which is still in lack of effective etiological treatment. Oxidative stress has been demonstrated to participate in the impairment of nucleus pulposus cells (NPCs). As the most important neuroendocrine hormone in biological clock regulation, melatonin (MLT) is also featured by good antioxidant effect. In this study, we investigated the effect and mechanisms of melatonin on oxidative stress-induced damage in rat NPCs.

MAIN METHODS

Cytotoxicity of H₂O₂ and protecting effect of melatonin were analyzed with Cell Counting kit-8 (CCK-8). Cell apoptosis rate was detected by Annexin V-FITC/PI staining. DCFH-DA probe was used for the reactive oxygen species (ROS) detection. The mitochondrial membrane potential (MMP) changes were analyzed with JC-1 probe. Intracellular oxidation product and reductants were measured through enzymatic reactions. Extracellular matrix (ECM) and apoptosis associated proteins were analyzed with Western blot assays.

KEY FINDINGS

Melatonin preserved cell viability of NPCs under oxidative stress. The apoptosis rate, ROS level and malonaldehyde (MDA) declined with melatonin. MLT/H₂O₂ group showed higher activities of GSH and SOD. The fall of MMP receded and the expression of ECM protein increased with treatment of melatonin. The mitochondrial pathway of apoptosis was inhibited by melatonin.

SIGNIFICANCE

Melatonin alleviated the oxidative stress-induced apoptosis of NPCs. Melatonin could be a promising alternative in treatment of IVDD.

Antioxidant functionalized polymer capsules to prevent oxidative stress

Polymeric capsules exhibit significant potential for therapeutic applications as microreactors, where the bio-chemical reactions of interest are efficiently performed in a spatial and time defined manner due to the encapsulation of an active biomolecule (e.g., enzyme) and control over the transfer of reagents and products through the capsular membrane. In this work, catalase loaded polymer capsules functionalized with an external layer of tannic acid (TA) are fabricated via a layer-by-layer approach using calcium carbonate as a sacrificial template. The capsules functionalised with TA exhibit a higher scavenging capacity for hydrogen peroxide and hydroxyl radicals, suggesting that the external layer of TA shows intrinsic antioxidant properties, and represents a valid strategy to increase the overall antioxidant potential of the developed capsules. Additionally, the hydrogen peroxide scavenging capacity of the capsules is enhanced in the presence of the encapsulated catalase. The capsules prevent oxidative stress in an in vitro inflammation model of degenerative disc disease. Moreover, the expression of matrix metalloproteinase-3 (MMP-3), and disintegrin and metalloproteinase with thrombospondin motif-5 (ADAMTS-5), which represents the major proteolytic enzymes in intervertebral disc, are attenuated in the presence of the polymer capsules. This platform technology exhibits potential to reduce oxidative stress, a key modulator in the pathology of a broad range of inflammatory diseases.

STATEMENT OF SIGNIFICANCE

Oxidative stress damages important cell structures leading to cellular apoptosis and senescence, for numerous disease pathologies including cancer, neurodegeneration or osteoarthritis. Thus, the development of biomaterials-based systems to control oxidative stress has gained an increasing interest. Herein, polymer capsules loaded with catalase and functionalized with an external layer of tannic acid are fabricated, which can efficiently scavenge important reactive oxygen species (i.e., hydroxyl radicals and hydrogen peroxide) and modulate extracellular matrix activity in an in vitro inflammation model of nucleus pulposus. The present work represents accordingly, an important advance in the development and application of polymer capsules with antioxidant properties for the treatment of oxidative stress, which is applicable for multiple inflammatory disease targets.

[Effect of heme oxygenase 1 on the apoptosis of human degenerated nucleus pulposus cells induced by tumor necrosis factor α]

Objective

To investigate the effect of heme oxygenase 1 (HO-1) on the apoptosis of human degenerated nucleus pulposus (NP) cells induced by tumor necrosis factor α (TNF-α), and explore its possible molecular mechanism.

Methods

The intervertebral disc tissues were derived from patients with lumbar intervertebral disc herniation. Then, the NP cells were cultured in vitro and the third generation of NP cells were used for subsequent experiments. Cell counting kit 8 (CCK-8) method was used to observe the proliferative effect of TNF-α on the NP cells in vitro at the concentration of 10, 20, 50, 100, and 200 ng/mL. The most apropriate concentration was selected according to the result of CCK-8. The NP cells were cultured with basal medium (control group), TNF-α (TNF-α group), TNF-α and CoPP 10 μmol/L (CoPP group), and TNF-α and ZnPP 15 μmol/L (ZnPP group), respectively. After cultured, the cell poptosis was detected by Hoechst staining and flow cytometry; the expression of cleaved Caspase-3, epithelial membrane protein 1 (EMP-1), HO-1, and p-P65 proteins were detected by Western blot. In order to further explore the potential molecular mechanisms of HO-1 for cell apoptosis, the NP cells were cultured with TNF-α (TNF-α stimulated group), TNF-α and pyrrolidine dithiocarbamate (PDTC) 5 μmol/L (TNF-α+PDTC stimulated group), respectively. Then the cell apoptosis rate was measured by flow cytometry at 24 hours after cultured.

Results

The optimal concentration of TNF-α was 100 ng/mL. Hoechst staining showed that a few apoptotic cells could be observed in control group and CoPP group; the apoptosis-like nucleis were observed in TNF-α group and ZnPP group, which was the most significant in ZnPP group. Flow cytometry showed that the cell apoptosis rates of TNF-α group, CoPP group, and ZnPP group were significantly increased when compared with the control group ( P<0.05). Compared with TNF-α group, the cell apoptosis rate in CoPP group decreased ( P<0.05), while in ZnPP group it increased ( P<0.05). Western blot showed that the expression of HO-1 protein in TNF-α group was decreased, and the expressions of cleaved Caspase-3, EMP-1, and p-P65 proteins were increased when compared with the control group ( P<0.05). Compared with TNF-α group, the expression of HO-1 protein in CoPP group increased, and the expressions of cleaved Caspase-3, EMP-1, and p-P65 proteins were reduced ( P<0.05); the expression of HO-1 protein in ZnPP group decreased ( P<0.05), the expressions of cleaved Caspase-3 and EMP-1 proteins increased ( P<0.05), and the expression of p-P65 protein was not significantly changed ( P>0.05). Compared with TNF-α stimulated group, the cell apoptosis rate in TNF-α+PDTC stimulated group was significantly reduced ( t=3.076, P=0.031).

Conclusion

HO-1 can inhibit the apoptosis of degerated NP cells induced by TNF-α, and its mechanism effect is by inhibiting the nuclear factor кB signaling pathway.

Resveratrol increases nucleus pulposus matrix synthesis through activating the PI3K/Akt signaling pathway under mechanical compression in a disc organ culture

Disc nucleus pulposus (NP) matrix homeostasis is important for normal disc function. Mechanical overloading seriously decreases matrix synthesis and increases matrix degradation. The present study aims to investigate the effects of resveratrol on disc NP matrix homeostasis under a relatively high-magnitude mechanical compression and the potential mechanism underlying this process. Porcine discs were perfusion-cultured and subjected to a relatively high-magnitude mechanical compression (1.3 MPa at a frequency of 1.0 Hz for 2 h once per day) for 7 days in a mechanically active bioreactor. The non-compressed discs were used as controls. Resveratrol was added along with culture medium to observe the effects of resveratrol on NP matrix synthesis under mechanical load respectively. NP matrix synthesis was evaluated by histology, biochemical content (glycosaminoglycan (GAG) and hydroxyproline (HYP)), and expression of matrix macromolecules (aggrecan and collagen II). Results showed that this high-magnitude mechanical compression significantly decreased NP matrix content, indicated by the decreased staining intensity of Alcian Blue and biochemical content (GAG and HYP), and the down-regulated expression of NP matrix macromolecules (aggrecan and collagen II). Further analysis indicated that resveratrol partly stimulated NP matrix synthesis and increased activity of the PI3K/Akt pathway in a dose-dependent manner under mechanical compression. Together, resveratrol is beneficial for disc NP matrix synthesis under mechanical overloading, and the activation of the PI3K/Akt pathway may participate in this regulatory process. Resveratrol may be promising to regenerate mechanical overloading-induced disc degeneration.

Pramlintide regulation of extracellular matrix (ECM) and apoptosis through mitochondrial-dependent pathways in human nucleus pulposus cells

Pramlintide, an approved analog of amylin, is responsible for regulating the physiology of energy homeostasis. The goals of this study were to investigate the roles of pramlintide in the regulation of cell survival and matrix metabolism, and further explore their underlying mechanisms, in human nucleus pulposus (NP) cells. NP cells were treated with different concentrations of pramlintide in normoxic or hypoxic conditions. Cell viability, LAC concentration, calcium concentration, mitochondrial membrane potential (ΔΨm), MMPs proteins, and apoptotic related proteins were detected. The results indicate that pramlintide could improve NP cell proliferation, glycolytic activity, and the ECM synthesis under hypoxia, which is evident from the increased precipitation of proteoglycans; increased expression of AGG, Col2, and SOX9 proteins; and decreased expression of MMP3, MMP9, and MMP13 proteins, which are Ca²⁺-dependent enzymes. And, pramlintide could facilitate the survival of NP cells through mitochondrial-mediated, Bcl-2/caspase-3-dependent apoptosis. In addition, activation of AKT-AMPK/mTOR signaling pathway is also observed by the treatment. These findings demonstrate that pramlintide may play a pivotal role in reversing intervertebral disk degeneration and may relieve the impairment of ECM metabolism and NP cells survival through mitochondrial-dependent apoptotic signaling pathway, thus offering a novel potential pharmacological treatment strategy.

Hypoxia-inducible factor-lα mediates aggrecan and collagen Π expression via NOTCH1 signaling in nucleus pulposus cells during intervertebral disc degeneration

Although hypoxia-inducible factor-lα (HIF-lα) has been reported to have an important role in the metabolism and synthesis of the extracellular matrix (ECM) of nucleus pulposus cells (NPCs), the underlying mechanism has not been fully clarified. Here, we show for the first time that NOTCH1 expression is decreased in NPs isolated from degenerated human intervertebral discs (IVDs), as well as in the NPs of NP-specific HIF-1α^-/- mice. Our study reveals that overexpression of HIF-1α leads to increased expression of NOTCH1, the NOTCH1 ligand JAGGED1, and its target gene hairy and enhancer of split-1 (HES1), while also upregulating collagen Π and aggrecan expression in human NPCs. Importantly, these changes in expression are significantly suppressed by the NOTCH1 inhibitor DAPT. In parallel with changes in collagen Π and aggrecan expression, inhibition of the HIF-1α-NOTCH1 pathway altered ECM turnover by suppressing expression of the matrix metalloproteinases MMP1 and MMP13, while increasing the expression of tissue inhibitor of metalloproteinase-1 (TIMP1). Lastly, activation of NOTCH1 via JAGGED1 in human NPCs isolated from degenerated IVDs restored collagen Π and aggrecan expression. Therefore, our study shows that HIF-1α regulates collagen Π and aggrecan expression through NOTCH1 signaling and implicate NOTCH1 as a potential therapeutic target in disc degeneration.

Notochordal cell-derived conditioned medium protects human nucleus pulposus cells from stress-induced apoptosis

BACKGROUND CONTEXT

Degenerative disc disease (DDD) remains without an effective therapy and presents a costly burden to society.

PURPOSE

Based upon prior reports concerning the effects of notochordal cell-conditioned medium (NCCM) on disc cells, we performed a proof of principle study to determine whether NCCM could reduce cytotoxic stress-induced apoptosis in human disc nucleus pulposus (NP) cells.

STUDY DESIGN/SETTING

This is an "in vitro" fundamental or basic science study.

METHODS

Nucleus pulpous cells derived from 15 patients undergoing spinal surgery were treated with interleukin (IL)-1β and Fas ligand or etoposide in the presence of NCCM. We determined pro- or antiapoptotic events using activated caspase assays and determined genomic regulation of apoptosis using polymerase chain reaction arrays validated using Western blotting methods. We interrogated cellular apoptotic regulation using JC-1 dye and flow cytometry and performed enzyme-linked immunosorbent assays to evaluate NP inflammatory cytokine secretion.

RESULTS

Notochordal cell-conditioned medium inhibits cytotoxic stress-induced caspase-9 and -3/7 activities and maintains the mitochondrial membrane potential in human NP cells, thereby suppressing the intrinsic apoptotic pathway. Gene expression analysis revealed the X-linked inhibitor of apoptosis protein as a key player responsible for evading etoposide-induced apoptosis in the presence of NCCM, and we verified these data using Western blotting. Enzyme-linked immunosorbent assay results revealed distinct differences in IL-6 and IL-8 secretions by NP cells in response to etoposide in the presence of NCCM.

CONCLUSIONS

Here we demonstrate for the first time that NCCM reduces cytotoxic stress-induced apoptosis in human NP cells. Soluble factors present in NCCM could be harnessed for the development of novel therapeutics for the treatment of DDD.

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.