Comparison of cellular response in bovine intervertebral disc cells and articular chondrocytes: effects .of lipopolysaccharide on proteoglycan metabolism

Identification of Critical Genes and Proteins for Stent Restenosis Induced by Esophageal Benign Hyperplasia in Esophageal Cancer

This study was conducted to explore the potential genes and proteins associated with esophagus benign hyperplasia induced by esophageal stents. Five patients with esophageal cancer subjected to esophageal stent placement were enrolled in this study. Long non-coding RNA (lncRNA) sequencing and tandem mass tag quantitative proteomics analysis were performed by using the collected hyperplastic samples and adjacent non-hyperplastic tissues. Differentially expressed (DE) RNAs and proteins were analyzed, followed by functional enrichment analysis, protein-protein interaction (PPI) network analysis, and competitive endogenous RNA (ceRNA) network construction. Venn analysis was performed to extract the overlaps between DE mRNAs and DE proteins and the expression correlations between DE mRNA and proteins were analyzed. Results showed that total 642 DE RNAs (457 mRNA and 185 lncRNAs) and 256 DE proteins were detected. DE mRNAs (such as MAOB, SDR16C5, and FOSL1) were enriched in oxidation-reduction process-associated functions. PPI network was comprised of 175 nodes and 425 edges. VEGFA was a significant node with the highest degree. LncRNA-mRNA network with three subnetworks (C1, C2, C3) was constructed for lncRNAs with more than 15 gene targets. RP11-58O9.2 was a significant lncRNA with the most target genes and RP11-667F14.1 regulated more than 20 targets. FOSL1 was a common target of the two lncRNAs. Function analysis showed that DE lncRNAs were involved in the HTLV-I infection (RP11-58O9.2 and RP11-667F14.1) and IL-17 signaling pathways (RP11-5O24.1 and RP11-58O9.2). Total 11 DE mRNAs were overlapped with DE proteins, among which MAOB and SDR16C5 showed positive correlations between mRNA and protein expression. Function analysis showed that MAOB was enriched in oxidation-reduction process and its protein was closely related with response to lipopolysaccharide. VEGFA, FOSL1, MAOB, SDR16C5, RP11-58O9.2, RP11-667F14.1, and RP11-288A5.2 may be served as genetic targets for preventing stent restenosis in esophageal cancer.

Hypo-Osmotic Loading Induces Expression of IL-6 in Nucleus Pulposus Cells of the Intervertebral Disc Independent of TRPV4 and TRPM7

Painful intervertebral disc (IVD) degeneration is an age-related process characterized by reduced tissue osmolarity, increased catabolism of the extracellular matrix, and elevated levels of pro-inflammatory molecules. With the aging population and constantly rising treatment costs, it is of utmost importance to identify potential therapeutic targets and new pharmacological treatment strategies for low back pain. Transient receptor potential (TRP) channels are a family of Ca²⁺ permeable cell membrane receptors, which can be activated by multitude of stimuli and have recently emerged as contributors to joint disease, but were not investigated closer in the IVD. Based on the gene array screening, TRPC1, TRPM7, and TRPV4 were overall the most highly expressed TRP channels in bovine IVD cells. We demonstrated that TRPV4 gene expression was down-regulated in hypo-osmotic condition, whereas its Ca²⁺ flux increased. No significant differences in Ca²⁺ flux and gene expression were observed for TRPM7 between hypo- and iso-osmotic groups. Upon hypo-osmotic stimulation, we overall identified via RNA sequencing over 3,000 up- or down-regulated targets, from which we selected aggrecan, ADAMTS9, and IL-6 and investigated whether their altered gene expression is mediated through either the TRPV4 or TRPM7 channel, using specific activators and inhibitors (GSK1016790A/GSK2193874 for TRPV4 and Naltriben/NS8593 for TRPM7). GSK1016790A induced the expression of IL-6 under iso-osmotic condition, alike to hypo-osmotic stimulation alone, indicating that this effect might be TRPV4-mediated. However, using the TRPV4 blocker GSK2193874 failed to prevent the increase of IL-6 under hypo-osmotic condition. A treatment with TRPM7-activator did not cause significant changes in the gene expression of tested targets. In conclusion, while TRPV4 and TRPM7 are likely involved in osmosensing in the IVD, neither of them mediates hypo-osmotically-induced gene expression changes of aggrecan, ADAMTS9, and IL-6.

MicroRNA-223 inhibits lipopolysaccharide-induced inflammatory response by directly targeting Irak1 in the nucleus pulposus cells of intervertebral disc

This study was aimed to research the effect of miR-223 on the inflammatory responses induced by lipopolysaccharide (LPS) in nucleus pulposus (NP) cells of rat intervertebral disc. Isolated rat NP cells were induced by LPS. Reverse transcriptase quantitative real-time polymerase chain reaction was used to detect gene expression. To detect protein expression, Western blot and enzyme-linked immunosorbent assay experiments were applied. The putative targeting relationship between miR-223 and Irak1 was determined using dual-luciferase reporter gene assay. We found that miR-223 was downregulated in LPS-induced NP cells. MiR-223 upregulated the expression of extracellular matrix-related genes (Aggrecan and Collagen II). Matrix degrading enzymes (ADAMTS4, ADAMTS5, MMP3 and MMP13), NO reaction-associated proteins (PGE2, COX-2 and INOS) and the expression of nuclear factor (NF)-κB signaling-related proteins were downregulated after miR-233 overexpression. In addition, luciferase reporter assays demonstrated that miR-223 directly targeted Irak1. MiR-223 overexpression could inhibit NF-κB signaling by targeting Irak1, and finally suppress the LPS-induced inflammation in NP cells. © 2018 IUBMB Life, 70(6):479-490, 2018.

Time-dependent proteomic and genomic alterations in Toll-like receptor-4-activated human chondrocytes: increased expression of lamin A/C and annexins

Activation of Toll-like receptor-4 (TLR-4) in articular chondrocytes increases the catabolic compartment and leads to matrix degradation during the development of osteoarthritis. In this study, we determined the proteomic and genomic alterations in human chondrocytes during lipopolysaccharide (LPS)-induced inflammation to elucidate the underlying mechanisms and consequences of TLR-4 activation. Human chondrocytes were cultured with LPS for 12, 24, and 36 h to induce TLR-4 activation. The TLR-4-induced inflammatory response was confirmed by real-time PCR analysis of increased interleukin-1 beta (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF-α) expression levels. In TLR-4-activated chondrocytes, proteomic changes were determined by two-dimensional electrophoresis and matrix-assisted laser desorption/ionization-mass spectroscopy analysis, and genomic changes were determined by microarray and gene ontology analyses. Proteomics analysis identified 26 proteins with significantly altered expression levels; these proteins were related to the cytoskeleton and oxidative stress responses. Gene ontology analysis indicated that LPS treatment altered specific functional pathways including ‘chemotaxis’, ‘hematopoietic organ development’, ‘positive regulation of cell proliferation’, and ‘regulation of cytokine biosynthetic process’. Nine of the 26 identified proteins displayed the same increased expression patterns in both proteomics and genomics analyses. Western blot analysis confirmed the LPS-induced increases in expression levels of lamin A/C and annexins 4/5/6. In conclusion, this study identified the time-dependent genomic, proteomic, and functional pathway alterations that occur in chondrocytes during LPS-induced TLR-4 activation. These results provide valuable new insights into the underlying mechanisms that control the development and progression of osteoarthritis.

Sesamin inhibits lipopolysaccharide-induced inflammation and extracellular matrix catabolism in rat intervertebral disc

Intervertebral disc (IVD) degeneration contributes to most spinal degenerative diseases, while treatment inhibiting IVD degeneration is still in the experimental stage. Sesamin, a bioactive component extracted from sesame, has been reported to exert chondroprotective and anti-inflammatory effects. Here, we analyzed the anti-inflammatory and anti-catabolic effects of sesamin on rat IVD in vitro and ex vivo. Results show that sesamin significantly inhibits the lipopolysaccharide (LPS)-induced expression of catabolic enzymes (MMP-1, MMP-3, MMP-13, ADAMTS-4, ADAMTS-5) and inflammation factors (IL-1β, TNF-α, iNOS, NO, COX-2, PGE2) in a dose-dependent manner in vitro. It is also proven that migration of macrophages induced by LPS can be inhibited by treatment with sesamin. Organ culture experiments demonstrate that sesamin protects the IVD from LPS-induced depletion of the extracellular matrix ex vivo. Moreover, sesamin suppresses LPS-induced activation of the mitogen-activated protein kinase (MAPK) pathway through inhibiting phosphorylation of JNK, the common downstream signaling pathway of LPS and IL-1β, which may be the potential mechanism of the effects of sesamin. In light of our results, sesamin protects the IVD from inflammation and extracellular matrix catabolism, presenting positive prospects in the treatment of IVD degenerative diseases.

Crocin exerts anti-inflammatory and anti-catabolic effects on rat intervertebral discs by suppressing the activation of JNK

As intervertebral disc (IVD) degeneration has been proven to contribute to low back pain (LBP), drug treatment aiming at attenuating IVD degeneration may prove to be benefiical. Crocin, a bioactive component of saffron, has been found to exert anti-inflammatory effects on cartilage. In the present study, the anti-inflammatory and anti-catabolic effects of crocin on rat IVDs were analyzed in vitro and ex vivo. Nucleus pulposus (NP) cells were isolated from the lumbar IVDs of Sprague-Dawley rats. The NP cells were first treated with various concentrations of crocin, and then stimulated with lipopolysaccharide (LPS) to induce inflammation. Subsequently, RT-qPCR and enzyme-linked immunosorbent assay were carried out to measure the expression levels of catabolic enzymes, pro-inflammatory factors and the components of the extracellular matrix (ECM). In addition, western blot analysis was also used to investigate the related signaling pathways. The whole spinal motion segment (vertebra-IVD-vertebra section) of the rats was isolated and cultured in the presence or absence of LPS and crocin for 7 days. The ex vivo effects of crocin on the ECM of the IVD structures were determined by histological and biochemical analysis. In vitro, crocin significantly inhibited the LPS-induced overexpression of catabolic enzymes [matrix metalloproteinase (MMP)-1, MMP-3, MMP-13, a disintegrin-like and metalloprotease (reprolysin type) with thrombospondin type 1 motif (ADAMTS)-4 and ADAMTS‑5], pro-inflammatory factors [interleukin (IL)-1β, tumor necrosis factor (TNF)-α, IL-6 and inducible nitric oxide synthase (iNOS)] and Toll-like receptor (TLR)‑2 in a concentration-dependent manner. Notably, crocin partly prevented the downregulation of aggrecan and type II collagen (collagen‑II). Moreover, crocin suppressed the LPS-induced activation of the mitogen-activated protein kinase (MAPK) pathway by inhibiting the phosphorylation of c-Jun N-terminal kinase (JNK). Ex vivo experiments demonstrated that crocin protected the rat IVDs from the LPS-induced depletion of the ECM components, including proteoglycan and collagen-II. In conclusion, crocin effectively suppressed the degeneration-related inflammation and catabolism in rat IVDs in vitro and ex vivo, suggesting that crocin has potential for use as a therapuetic strategy in the treatment of LBP.

Anti-inflammatory effects of hydrophilic and lipophilic statins with hyaluronic acid against LPS-induced inflammation in porcine articular chondrocytes

The objective of the study is to understand the therapeutic effects of lipophilic (simvastatin) and hydrophilic statins (pravastatin) combined with/without hyaluronic acid for osteoarthritis by an in vitro LPS-induced inflammatory model of articular chondrocytes. HA in combination with different doses of simvastatin or pravastatin were used. Beside cytotoxicity, the influence of statins on NO production, pro-inflammatory cytokine, inflammatory mediators, and NF-κB p50 protein were analyzed. Finally, TUNEL assay was performed to detect DNA strand breakage. Two statins were less able to lower NF-κB activity when they were administrated along without HA. The gene expression demonstrates that simvastatin and pravastatin had the ability to decrease pro-inflammatory and inflammatory mediator levels. High dose simvastatin with or without HA down regulated inflammatory cytokines, but resulted in higher cytotoxicity. TUNEL assay confirms the regulatory effect of statins with or without HA over the apoptosis of chondrocytes, especially in hydrophilic statins. The significant down-regulation of inflammatory mediators suggests that intra-articular injection of HA in combination with statins might feasibly slow the progress of osteoarthritis. Administration of simvastatin or pravastatin with hyaluronic acid may produce beneficial effects for OA treatment, but with better results when hydrophilic statin was used.

Lactoferricin mediates anti-inflammatory and anti-catabolic effects via inhibition of IL-1 and LPS activity in the intervertebral disc

The catabolic cytokine interleukin-1 (IL-1) and endotoxin lipopolysaccharide (LPS) are well-known inflammatory mediators involved in degenerative disc disease, and inhibitors of IL-1 and LPS may potentially be used to slow or prevent disc degeneration in vivo. Here, we elucidate the striking anti-catabolic and anti-inflammatory effects of bovine lactoferricin (LfcinB) in the intervertebral disc (IVD) via antagonism of both IL-1 and LPS-mediated catabolic activity using in vitro and ex vivo analyses. Specifically, we demonstrate the biological counteraction of LfcinB against IL-1 and LPS-mediated proteoglycan (PG) depletion, matrix-degrading enzyme production, and enzyme activity in long-term (alginate beads) and short-term (monolayer) culture models using bovine and human nucleus pulposus (NP) cells. LfcinB significantly attenuates the IL-1 and LPS-mediated suppression of PG production and synthesis, and thus restores PG accumulation and pericellular matrix formation. Simultaneously, LfcinB antagonizes catabolic factor mediated induction of multiple cartilage-degrading enzymes, including MMP-1, MMP-3, MMP-13, ADAMTS-4, and ADAMTS-5, in bovine NP cells at both mRNA and protein levels. LfcinB also suppresses the catabolic factor-induced stimulation of oxidative and inflammatory factors such as iNOS, IL-6, and toll-like receptor-2 (TLR-2) and TLR-4. Finally, the ability of LfcinB to antagonize IL-1 and LPS-mediated suppression of PG is upheld in an en bloc intradiscal microinjection model followed by ex vivo organ culture using both mouse and rabbit IVD tissue, suggesting a potential therapeutic benefit of LfcinB on degenerative disc disease in the future.

Toll-Like Receptor 4 (TLR4) expression and stimulation in a model of intervertebral disc inflammation and degeneration

STUDY DESIGN

We measured the expression and responses of Toll-Like Receptor 4 (TLR4) activation in the intervertebral disc (IVD) in vitro and in vivo. We hypothesize that stimulation of the IVD with the TLR4 ligand lipopolysaccharide (LPS) results in upregulation of a coordinated set of proinflammatory mediators and inhibition of matrix expression, both consistent with a molecular profile of degeneration.

OBJECTIVE

To characterize early inflammatory and morphological changes induced by TLR4 activation in the IVD.

SUMMARY OF BACKGROUND DATA

TLR4 is a pattern recognition receptor activated in innate immunity that has been implicated in disease mechanisms of inflammatory cartilaginous degeneration. However, no study to date has examined the expression and responses of TLR4 in the IVD.

METHODS

IVD cells were stimulated with LPS in a dose-dependent manner, and inflammatory cytokine levels were measured by quantitative reverse transcription-polymerase chain reaction. Histological and inflammatory changes due to in vivo injection of LPS into the rat caudal IVD were measured by enzyme-linked immunosorbent assay and immunoblotting.

RESULTS

Baseline TLR4 expression in IVD tissue varied according to cell type. LPS stimulation resulted in significant increases in tumor necrosis factor α (TNF)-α, interleukin (IL)-1β, IL-6, and nitric oxide levels and significant inhibition in aggrecan and collagen-2. Intradiscal injection of LPS was found to cause moderate degenerative changes in the IVD, with increases in tissue levels of IL-1β, TNF-α, high mobility group box 1 protein (HMGB1), and macrophage migration inhibitory factor (MIF).

CONCLUSION

This study provides the first evidence that IVD cells express TLR4 and are responsive to TLR4 activation by upregulating a coordinated set of inflammatory cytokines. This study suggests that intradiscal injection of LPS offers a model for triggering inflammation of the IVD, demonstrating that inflammatory insults alone may potentially trigger degenerative changes of the IVD.

Variations in gene and protein expression in canine chondrodystrophic nucleus pulposus cells following long-term three-dimensional culture

Intervertebral disc (IVD) degeneration greatly affects quality of life. The nucleus pulposus (NP) of chondrodystrophic dog breeds (CDBs) is similar to the human NP, because the cells disappear with age and are replaced by fibrochondrocyte-like cells. However, because IVD develops as early as within the first year of life, we used canines as a model to investigate in vitro the mechanisms underlying IVD degeneration. Specifically, we evaluated the potential of a three-dimensional (3D) culture of healthy NP as an in vitro model system to investigate the mechanisms of IVD degeneration. Agarose hydrogels were populated with healthy NP cells from beagles after performing magnetic resonance imaging, and mRNA expression profiles and pericellular extracellular matrix (ECM) protein distribution were determined. After 25 days of 3D culture, there was a tendency for redifferentiation into the native NP phenotype, and mRNA levels of Col2A1, COMP, and CK18 were not significantly different from those of freshly isolated cells. Our findings suggest that long-term 3D culture promoted chondrodystrophic NP redifferentiation through reconstruction of the pericellular microenvironment. Further, lipopolysaccharide (LPS) induced expression of TNF-α, MMP3, MMP13, VEGF, and PGES mRNA in the 3D cultures, creating a molecular milieu that mimics that of degenerated NP. These results suggest that this in vitro model represents a reliable and cost-effective tool for evaluating new therapies for disc degeneration.

Cells scaffold complex for Intervertebral disc Anulus Fibrosus tissue engineering: in vitro culture and product analysis

The study was designed to investigate feasibility of tissue culture in vitro utilizing static culture method. Annulus fibrosus cells obtained from spine of rabbits were cultured. Results showed that fibrous tissue infiltration could be detected in shallow layer. With extended time, tissue infiltration depth increased, but there were still a large amount of holes in central part. Fibrous tissue infiltration was detected in the control side products and inner infiltration wasn't obvious. Hydroxyproline content of the control side products gradually increased with extended culture time. Hydroxyproline content of the control side products in the third and fourth month was significantly higher than that in the first month, but lower than those of the experimental side products and normal annulus fibrosus cells. DNA content of the control side products in the third and fourth month was significantly increased compared to the first month. DNA content of the control side products at each phase point was significantly lower than that of the experimental side and normal annulus fibrosus cells. Furthermore, there was lower expression levels of the type I, II collagen mRNA and protein in the experimental side scaffolds compared to the control side product. This study demonstrates the successful formation of Intervertebral disc Anulus Fibrosus in vitro by static culture method.

Toll-like receptor adaptor signaling molecule MyD88 on intervertebral disk homeostasis: in vitro, ex vivo studies

MyD88 is an adapter protein that links toll-like receptors (TLRs) and Interleukin-1 receptors (IL-1Rs) with downstream signaling molecules. The MyD88 has been found to be an essential mediator in the development of osteoarthritis in articular cartilage. However, the role of the MyD88 pathway has yet to be elucidated in the intervertebral disk (IVD). Using in vitro techniques, we analyzed the effect of MyD88 pathway-specific inhibition on the potent inflammatory and catabolic mediator LPS and IL-1 in bovine and human nucleus pulposus (NP) cells by assessing matrix-degrading enzyme expression, including matrix metalloproteases (MMPs) and a disintegrin-like and metalloprotease with thrombospondin motifs (ADAMTS family). We also analyzed inhibition of MyD88 in the regulation of inducible nitric oxide synthase and TLR-2. Finally, we used an ex vivo organ culture model to assess the effects of MyD88 inhibitor (MyD88i) on catabolic factor-induced disk degeneration in mice lumbar disks. In bovine NP cells, MyD88i potently antagonizes LPS- or IL-1-mediated induction of cartilage-degrading enzyme production, including MMP-1, MMP-13, ADAMTS-4, and ADAMTS-5. MyD88i also attenuates the LPS- or IL-1-mediated induction of iNOS and TLR-2 gene expression. Our ex vivo findings reveal inhibition of MyD88 via counteraction of IL-1-mediated proteoglycan depletion. The findings from this study demonstrate the potent anti-inflammatory and anti-catabolic effects of inhibition of MyD88 pathway inhibition on IVD homeostasis, suggesting a potential therapeutic benefit of a MyD88i in degenerative disk disease in the future.

Using 18F-FDG microPET imaging to measure the inhibitory effects of Clematis chinensis Osbeck on the pro-inflammatory and degradative mediators associated with inflammatory arthritis

AIM OF THE STUDY

This study examined the modulating effects of Clematis chinensis Osbeck (Ranunculaeae) on pro-inflammatory and degradative mediators associated with inflammatory arthritis.

MATERIALS AND METHODS

Primary human chondrocytes (PHC) were stimulated with IL-1β or lipopolysaccharide (LPS) to induce the enhanced release of prostaglandin E(2) (PGE(2)), metalloproteinase (MMP-3 and -13), and cyclooxygenase-2 (COX-2) protein expression. The (18)F-FDG microPET imaging system was used to evaluate the anti-arthritic effects of Clematis chinensisin vivo.

RESULTS

The acetone extracted Clematis chinensis (CC6) contained the most total saponins compared to other solvent's extracts and showed significant and dose-dependent inhibitory effects on PGE(2), MMP-3, -13, and COX-2 productions by LPS-stimulated PHC. Furthermore, CC6 also exerted inhibitory effects on 2-(18)F-fluoro-2-deoxy-d-glucose ((18)F-FDG) uptake when assessed by positron emission tomography (PET) uptake in the joints and serum PGE(2) of rabbits with knee joints injected with LPS.

CONCLUSION

The results suggest the significant chondroprotective effects of Clematis chinensis are through its anti-inflammatory and MMPs inhibitory abilities. Meanwhile, we established a new analysis method to evaluate the Chinese herbal anti-arthritic effects.

Icariin protects murine chondrocytes from lipopolysaccharide-induced inflammatory responses and extracellular matrix degradation

Septic arthritis is an inflammatory arthropathy characterized by degeneration of articular cartilage. Icariin, the main active flavonoid glucoside isolated from Epimedium pubescens, is used as antirheumatics (or antiinflammatory), tonics, and aphrodisiacs in traditional Chinese medicine. In this study, we used lipopolysaccharide (LPS) to simulate the in vitro inflammatory response of chondrocytes during septic arthritis. Our hypothesis is that the icariin can protect chondrocytes from LPS-induced inflammation and extracellular matrix degradation. The inflammation of neonatal mice chondrocytes was induced by LPS and the antiinflammatory effects were examined. The synthesis of nitric oxide was analyzed, whereas the titer of glycosaminoglycan and total collagen were measured and the gene expressions (including inducible nitric oxide synthase [iNOS], matrix metalloproteinase [MMP]-1, MMP-3, and MMP-13) were evaluated. The results showed that the viability of chondrocytes, extracellular matrix synthesis, was significantly decreased, whereas nitric oxide synthesis was significantly increased in the presence of 10(-5) g/mL LPS. Icariin pretreatment can partially reverse these effects. The up-regulated expressions of MMP-1, 3, 13, cyclooxygenase-2 (COX-2), and iNOS genes by LPS treatment were also significantly down-regulated by the pretreatment of icariin to 1.8%, 0.056%, 7.7%, 3.1%, and 5.3% of the LPS-positive control sample, respectively. Our results demonstrate that icariin is a safe anabolic agent of chondrocytes. Icariin may exert its protective effects through inhibition of nitric oxide and MMP synthesis, and may then reduce the extracellular matrix destruction.

Differentiation of rodent bone marrow mesenchymal stem cells into intervertebral disc-like cells following coculture with rat disc tissue

This study aimed to evaluate whether rat mesenchymal stem cells (rMSCs) could be differentiated in vitro into disc-like cells by coculturing with intervertebral disc tissue. rMSCs were cultured with rodent intervertebral disc for up to 30 days in transwell plates. The differentiation of rMSCs was evaluated by immunostaining, Western blot, real-time RT-PCR, Northern blot, and electron microscopy. The potentials of multilineage differentiation and proteoglycan and collagen synthesis were also investigated. rMSCs underwent morphological changes to form three-dimensional micromasses and expressed collagen-2, aggrecan, and sox-9 at RNA and protein levels after 14 days of coculture. These changes were not detected in the samples of rMSCs cultured alone. Cocultured rMSCs also showed other characteristic features of disc-like cells, including the extracellular matrix formation, and proteoglycan and collagen synthesis. In addition, cellular contact between cocultured rMSCs and disc tissue was observed by electron microscopy. Committed rMSCs still retained their differentiation ability into mesoderm lineages of adipocytes or osteocytes when the local environment was altered. This study supports that MSCs are a promising source for cell therapy and tissue engineering in disc regeneration, and highlights that rMSCs can be induced into nucleus pulposus-like cells in vitro under the direct influence of intact disc tissue.

Chondrocyte acting as phagocyte to internalize polyethylene wear particles and leads to the elevations of osteoarthritis associated NO and PGE2

It remains a mystery about the role of chondrocyte or cartilage on the co-existence of ultra-high molecular weight polyethylene (UHMWPE) wear particles from partial joint arthroplasty. An inverted co-culture system was performed to investigate the interactions between chondrocytes and UHMWPE wear particles. It was first time observed that chondrocytes can engulf UHMWPE particles and release osteoarthritis associated pro-inflammatory factors. TEM observation and flow cytometric analysis demonstrated the phagocytosis of particles by chondrocytes. It was found that polyethylene particles may reduce the viability of chondrocytes, and enhance the secretion of nitric oxide (NO) and PGE(2). In conclusion, all these phenomena may contribute to further cartilage degeneration after partial joint arthroplasty surgery. It is first identified in this study that the chondrocyte acts as phagocyte to internalize wear particles and leads to the elevations of precursor mediators of osteoarthritis.