Hypoxia Differentially Affects Chondrogenic Differentiation of Progenitor Cells from Different Origins

Background and Objectives

Ear cartilage malformations are commonly encountered problems in reconstructive surgery, since cartilage has low self-regenerating capacity. Malformations that impose psychological and social burden on one's life are currently treated using ear prosthesis, synthetic implants or autologous flaps from rib cartilage. These approaches are challenging because not only they request high surgical expertise, but also they lack flexibility and induce severe donor-site morbidity. Through the last decade, tissue engineering gained attention where it aims at regenerating human tissues or organs in order to restore normal functions. This technique consists of three main elements, cells, growth factors, and above all, a scaffold that supports cells and guides their behavior. Several studies have investigated different scaffolds prepared from both synthetic or natural materials and their effects on cellular differentiation and behavior.

Methods and Results

In this study, we investigated a natural scaffold (alginate) as tridimensional hydrogel seeded with progenitors from different origins such as bone marrow, perichondrium and dental pulp. In contact with the scaffold, these cells remained viable and were able to differentiate into chondrocytes when cultured in vitro. Quantitative and qualitative results show the presence of different chondrogenic markers as well as elastic ones for the purpose of ear cartilage, upon different culture conditions.

Conclusions

We confirmed that auricular perichondrial cells outperform other cells to produce chondrogenic tissue in normal oxygen levels and we report for the first time the effect of hypoxia on these cells. Our results provide updates for cartilage engineering for future clinical applications.

The benefit of combining curcumin, bromelain and harpagophytum to reduce inflammation in osteoarthritic synovial cells

BACKGROUND

Osteoarthritis (OA) is the most common form of arthritis, affecting millions of people worldwide and characterised by joint pain and inflammation. It is a complex disease involving inflammatory factors and affecting the whole joint, including the synovial membrane. Since drug combination is widely used to treat chronic inflammatory diseases, a similar strategy of designing plant-derived natural products to reduce inflammation in OA joints may be of interest. In this study, we characterised the response of OA synovial cells to lipopolysaccharide (LPS) and investigated the biological action of the combination of curcumin, bromelain and harpagophytum in this original in vitro model of osteoarthritis.

METHODS

Firstly, human synovial cells from OA patients were stimulated with LPS and proteomic analysis was performed. Bioinformatics analyses were performed using Cytoscape App and SkeletalVis databases. Additionally, cells were treated with curcumin, bromelain and harpagophytum alone or with the three vegetal compounds together. The gene expression involved in inflammation, pain or catabolism was determined by RT-PCR. The release of the encoded proteins by these genes and of prostaglandin E2 (PGE2) were also assayed by ELISA.

RESULTS

Proteomic analysis demonstrated that LPS induces the expression of numerous proteins involved in the OA process in human OA synovial cells. In particular, it stimulates inflammation through the production of pro-inflammatory cytokines (Interleukin-6, IL-6), catabolism through an increase of metalloproteases (MMP-1, MMP-3, MMP-13), and the production of pain-mediating neurotrophins (Nerve Growth Factor, NGF). These increases were observed in terms of mRNA levels and protein release. LPS also increases the amount of PGE2, another inflammation and pain mediator. At the doses tested, vegetal extracts had little effect: only curcumin slightly counteracted the effects of LPS on NGF and MMP-13 mRNA, and PGE2, IL-6 and MMP-13 release. In contrast, the combination of curcumin with bromelain and harpagophytum reversed lots of effects of LPS in human OA synovial cells. It significantly reduced the gene expression and/or the release of proteins involved in catabolism (MMP-3 and -13), inflammation (IL-6) and pain (PGE2 and NGF).

CONCLUSION

We have shown that the stimulation of human OA synovial cells with LPS can induce protein changes similar to inflamed OA synovial tissues. In addition, using this model, we demonstrated that the combination of three vegetal compounds, namely curcumin, bromelain and harpagophytum, have anti-inflammatory and anti-catabolic effects in synovial cells and may thus reduce OA progression and related pain.

Description of Joint Alterations Observed in a Family Carrying p.Asn453Ser COMP Variant: Clinical Phenotypes, In Silico Prediction of Functional Impact on COMP Protein and Stability, and Review of the Literature

The role of genetics in the development of osteoarthritis is well established but the molecular bases are not fully understood. Here, we describe a family carrying a germline mutation in COMP (Cartilage Oligomeric Matrix Protein) associated with three distinct phenotypes. The index case was enrolled for a familial form of idiopathic early-onset osteoarthritis. By screening potential causal genes for osteoarthritis, we identified a heterozygous missense mutation of COMP (c.1358C>T, p.Asn453Ser), absent from genome databases, located on a highly conserved residue and predicted to be deleterious. Molecular dynamics simulation suggests that the mutation destabilizes the overall COMP protein structure and consequently the calcium releases from neighboring calcium binding sites. This mutation was once reported in the literature as causal for severe multiple epiphyseal dysplasia (MED). However, no sign of dysplasia was present in the index case. The mutation was also identified in one of her brothers diagnosed with MED and secondary osteoarthritis, and in her sister affected by an atypical syndrome including peripheral inflammatory arthritis of unknown cause, without osteoarthritis nor dysplasia. This article suggests that this mutation of COMP is not only causal for idiopathic early-onset osteoarthritis or severe MED, but can also be associated to a broad phenotypic variability with always joint alterations.

Co-Treatment with the Epigenetic Drug, 3-Deazaneplanocin A (DZNep) and Cisplatin after DZNep Priming Enhances the Response to Platinum-Based Therapy in Chondrosarcomas

Simple Summary

Chondrosarcoma is a rare bone tumor characterized by the secretion of a cartilage-like extracellular matrix. Its treatment poses major challenges, since chondrosarcoma is resistant to chemotherapy and radiotherapy. Consequently, chondrosarcoma treatment has been limited over the past 30 years, and consists in the surgical resection of the tumor. Increasing evidence suggests that future cancer therapies will be enhanced by the combination of epigenetic and conventional antitumor agents, leading to further investigations to combine 3-Deazaneplanocin A (DZNep), an epigenetic drug, with existing antitumoral agents. We show by in vitro and in vivo experiments that an optimised DZNep/cisplatin combination reduces chondrosarcoma viability and induces apoptosis more effectively than each of the drugs alone. These results demonstrate the potential use of this epigenetic-chemotherapeutic combination approach for further studies and management of chondrosarcoma treatment.

Abstract

Background: We have previously shown that 3-Deazaneplanocin A (DZNep) induces apoptosis in chondrosarcomas. Herein, we tested whether the combination of this epigenetic drug to a standard anticancer therapy may enhance the response to each drug in these bone tumors. Methods: Two chondrosarcoma cell lines (SW1353 and JJ012) were cultured in the presence of DZNep and/or cisplatin. Cell growth was evaluated by counting viable cells, and apoptosis was determined by Apo2.7 expression by flow cytometry. In vivo, the antitumoral effect of the DZNep/cisplatin combination was assessed through measurements of tumor volume of JJ012 xenografts in nude mice. Results: In vitro, the DZNep/cisplatin combination reduced cell survival and increased apoptosis compared to each drug alone in chondrosarcomas, but not in normal cells (chondrocytes). This enhancement of the antitumoral effect of the DZNep/cisplatin combination required a priming incubation with DZNep before the co-treatment with DZNep/cisplatin. Furthermore, in the chondrosarcoma xenograft mice model, the combination of both drugs more strongly reduced tumor growth and induced more apoptosis in tumoral cells than each of the drugs alone. Conclusion: Our results show that DZNep exposure can presensitize chondrosarcoma cells to a standard anticancer drug, emphasizing the promising clinical utilities of epigenetic-chemotherapeutic drug combinations in the future treatment of chondrosarcomas.

Cell-penetrating, antioxidant SELENOT mimetic protects dopaminergic neurons and ameliorates motor dysfunction in Parkinson's disease animal models

Parkinson's disease (PD) is a neurodegenerative disorder characterized by motor dysfunction for which there is an unmet need for better treatment options. Although oxidative stress is a common feature of neurodegenerative diseases, notably PD, there is currently no efficient therapeutic strategy able to tackle this multi-target pathophysiological process. Based on our previous observations of the potent antioxidant and neuroprotective activity of SELENOT, a vital thioredoxin-like selenoprotein, we designed the small peptide PSELT from its redox active site to evaluate its antioxidant properties in vivo, and its potential polyfunctional activity in PD models. PSELT protects neurotoxin-treated dopaminergic neurons against oxidative stress and cell death, and their fibers against neurotoxic degeneration. PSELT is cell-permeable and acts in multiple subcellular compartments of dopaminergic neurons that are vulnerable to oxidative stress. In rodent models of PD, this protective activity prevented neurodegeneration, restored phosphorylated tyrosine hydroxylase levels, and led to improved motor skills. Transcriptomic analysis revealed that gene regulation by PSELT after MPP+ treatment negatively correlates with that occurring in PD, and positively correlates with that occurring after resveratrol treatment. Mechanistically, a major impact of PSELT is via nuclear stimulation of the transcription factor EZH2, leading to neuroprotection. Overall, these findings demonstrate the potential of PSELT as a therapeutic candidate for treatment of PD, targeting oxidative stress at multiple intracellular levels.

EZH2 inhibition reduces cartilage loss and functional impairment related to osteoarthritis

Histone methyltransferase EZH2 is upregulated during osteoarthritis (OA), which is the most widespread rheumatic disease worldwide, and a leading cause of disability. This study aimed to assess the impact of EZH2 inhibition on cartilage degradation, inflammation and functional disability. In vitro, gain and loss of EZH2 function were performed in human articular OA chondrocytes stimulated with IL-1β. In vivo, the effects of EZH2 inhibition were investigated on medial meniscectomy (MMX) OA mouse model. The tissue alterations were assayed by histology and the functional disabilities of the mice by actimetry and running wheel. In vitro, EZH2 overexpression exacerbated the action of IL-1β in chondrocytes increasing the expression of genes involved in inflammation, pain (NO, PGE2, IL6, NGF) and catabolism (MMPs), whereas EZH2 inhibition by a pharmacological inhibitor, EPZ-6438, reduced IL-1β effects. Ex vivo, EZH2 inhibition decreased IL-1β-induced degradation of cartilage. In vivo, intra-articular injections of the EZH2 inhibitor reduced cartilage degradation and improved motor functions of OA mice. This study demonstrates that the pharmacological inhibition of the histone methyl-transferase EZH2 slows the progression of osteoarthritis and improves motor functions in an experimental OA model, suggesting that EZH2 could be an effective target for the treatment of OA by reducing catabolism, inflammation and pain.

Heterogeneity of chondrosarcomas response to irradiations with X-rays and carbon ions: A comparative study on five cell lines

Objectives

Chondrosarcomas are malignant bone tumors considered as resistant to radiotherapy. To unravel mechanisms of resistance, we compared biological responses of several chondrosarcomas to X-ray irradiations in normoxia and hypoxia. Since hadrontherapy with Carbon-ions gave interesting clinical outcomes, we also investigated this treatment in vitro.

Methods

Five human chondrosarcoma cell lines were used and cultured in normoxia or hypoxia. Their sensitivities to irradiations were determined by carrying out survival curves. DNA damage was monitored by γH2AX expression. Apoptosis was assessed by cell cycle analysis and Apo2.7 expression, and by evaluating PARP cleavage. Senescence was evaluated using SA β-galactosidase assay. Necrosis, and autophagy, were evaluated by RIP1 and beclin-1 expression, respectively. Mutations in relevant biological pathways were screened by whole-exome sequencing.

Results

X-ray radiations induced death in some chondrosarcomas by both apoptosis and senescence (CH2879), or by either of them (SW1353 and JJ012), whereas no death was observed in other cell lines (FS090 and 105KC). Molecularly, p21 was overexpressed when senescence was elicited. Genetic analysis allowed to identify putative genes (such as TBX3, CDK2A, HMGA2) permitting to predict cell response to irradiations. Unexpectedly, chronic hypoxia did not favor radioresistance in chondrosarcomas, and even increased the radiosensitivity of JJ012 line. Finally, we show that carbon ions triggered more DNA damages and death than X-rays.

Conclusions

Chondrosarcomas have different response to irradiation, possibly due to their strong genetic heterogeneity. p21 expression is suggested as predictive of X-ray-induced senescence. Surprisingly, hypoxia does not increase the radioresistance of chondrosarcomas, but as expected Carbon ion beams are more effective that X-rays in normoxia, whereas their efficiency was also variable depending on cell lines.

Development of a simple osteoarthritis model useful to predict in vitro the anti-hypertrophic action of drugs

Osteoarthritis (OA) is characterized by cartilage degradation, inflammation, and hypertrophy. Therapies are mainly symptomatic and aim to manage pain. Consequently, medical community is waiting for new treatments able to reduce OA process. This study aims to develop an in vitro simple OA model useful to predict drug ability to reduce cartilage hypertrophy. Human primary OA chondrocytes were incubated with transforming growth factor beta 1 (TGF-β1). Hypertrophy was evaluated by Runx2, type X collagen, MMP13, and VEGF expression. Cartilage anabolism was investigated by Sox9, aggrecan, type II collagen, and glycosaminoglycan expression. In chondrocytes, TGF-β1 increased expression of hypertrophic genes and activated canonical WNT pathway, while it decreased dramatically cartilage anabolism, suggesting that this treatment could mimic some OA features in vitro. Additionally, EZH2 inhibition, that has been previously reported to decrease cartilage hypertrophy and reduce OA development in vivo, attenuated COL10A1 and MMP13 upregulation and SOX9 downregulation induced by TGF-β1 treatment. Similarly, pterosin B (an inhibitor of Sik3), and DMOG (a hypoxia-inducible factor prolyl hydroxylase which mimicks hypoxia), repressed the expression of hypertrophy markers in TGF-β stimulated chondrocytes. In conclusion, we established an innovative OA model in vitro. This cheap and simple model will be useful to quickly screen new drugs with potential anti-arthritic effects, in complementary to current inflammatory models, and should permit to accelerate development of efficient treatments against OA able to reduce cartilage hypertrophy.

The Antitumoral Effect of the S-Adenosylhomocysteine Hydrolase Inhibitor, 3-Deazaneplanocin A, is Independent of EZH2 but is Correlated with EGFR Downregulation in Chondrosarcomas

BACKGROUND/AIMS

3-Deazaneplanocin, DZNep, has been reported to inhibit the EZH2 histone methylase and to induce cell apoptosis in chondrosarcomas (CS). The present study aims to confirm the therapeutic potential of EZH2 inhibitors and investigate the molecular mechanisms of DZNep in chondrosarcomas.

METHODS

CS cell lines and primary cultures were used. Apoptosis was investigated using PARP cleavage, caspase 3/7 activity, or Apo2.7 expression. S-adenosylhomocysteine (SAH) and S-adenosylmethionine (SAM) were quantified by UHPLC-MS/MS. Differentially expressed genes in treated-chondrosarcomas and chondrocytes were researched by microarray analysis.

RESULTS

DZNep induced apoptosis in chondrosarcomas both in vivo and in vitro. However, this effect was not correlated to EZH2 expression nor activity, and EZH2 knock-down by siRNA did not reduce CS viability. Additionally, the reduction of H3K27me3 induced by GSK126 or tazemetostat (EPZ-6438) did not provoke chondrosarcoma death. However, as expected, DZNep induced SAH accumulation and reduced SAM:SAH ratio. Further, microarray analysis suggests a key role of EGFR in antitumoral effect of DZNep, and pharmacological inhibition of EGFR reduced chondrosarcoma survival.

CONCLUSION

EZH2 is not an adequate target for chondrosarcoma treatment. However, DZNep induces apoptosis in chondrosarcomas in vitro and in vivo, by a mechanism likely mediated though EGFR expression. Consequently, it would be worth initiating clinical trials to evaluating efficiency to S-adenosylhomocysteine hydrolase or EGFR inhibitors in patients with chondrosarcomas.

Antiproliferative effect of the histone demethylase inhibitor GSK-J4 in chondrosarcomas

Chondrosarcoma (CS) is the second most common malignant bone sarcoma. Its treatment remains an issue, because this tumor is radio- and chemo-resistant. In the present study, we investigated the antitumoral potential of GSK-J4, a small molecule described as an inhibitor of histone demethylases UTX and JMJD3 (KDM6A and KDM6B), alone or in combination with cisplatin in CSs. Human CS-derived cell lines were treated with GSK-J4 in the presence or not of cisplatin. Survival curves were established and cell proliferation and cycle were evaluated by flow cytometry using dividing cell tracking technique utilizing carboxyfluorescein succinimidyl ester labeling, or DNA staining by propidium iodide. Apoptosis and senescence were also investigated. GSK-J4 decreased proliferation of CS cells. Additionally, it induced apoptosis in CH2879 and JJ012 cells, but not in SW1353 CSs. In addition, its association with cisplatin decreased cell proliferation more than drugs alone, whereas it did not increase apoptosis compared to cisplatin alone. Interestingly, GSK-J4 alone as well as in association with cisplatin did not affect chondrocyte survival or proliferation. In conclusion, this study suggests that demethylase inhibitors may be useful in improving therapy for CS in reducing its proliferation.

Epigenetic dynamic during endochondral ossification and articular cartilage development

Within the last decade epigenetics has emerged as fundamental regulator of numerous cellular processes, including those orchestrating embryonic and fetal development. As such, epigenetic factors play especially crucial roles in endochondral ossification, the process by which bone tissue is created, as well during articular cartilage formation. In this review, we summarize the recent discoveries that characterize how DNA methylation, histone post-translational modifications and non-coding RNA (e.g., miRNA and lcnRNA) epigenetically regulate endochondral ossification and chondrogenesis.

Modulation of Skin Inflammatory Response by Active Components of Silymarin

In this study, we compared selected silymarin components, such as quercetin (QE), 2,3-dehydrosilybin (DHS) and silybin (SB), with the anti-inflammatory drug indomethacin (IND) in terms of their wound healing potential. In view of the fact that pathological cutaneous wound healing is associated with persistent inflammation, we studied their anti-inflammatory activity against inflammation induced by bacterial lipopolysaccharide (LPS). We investigated the regulation of crucial pro-inflammatory transcription factors—nuclear factor kappa-B (NF-κB) and activator protein 1 (AP-1)—as well as the expression of downstream inflammatory targets by Western blotting, real-time PCR (RT-PCR), electrophoretic mobility shift assay (EMSA), and/or enzyme-linked immunosorbent assay (ELISA) in vitro using primary normal human dermal fibroblasts (NHDF). We demonstrated the greater ability of DHS to modulate the pro-inflammatory cytokines production via the NF-κB and AP-1 signaling pathways when compared to other tested substances. The prolonged exposure of LPS-challenged human dermal fibroblasts to DHS had both beneficial and detrimental consequences. DHS diminished interleukin-6 (IL-6) and interleukin-8 (IL-8) secretion but induced the significant upregulation of IL-8 mRNA associated with NF-κB and AP-1 activation. The observed conflicting results may compromise the main expected benefit, which is the acceleration of the healing of the wound via a diminished inflammation.

Evaluation of the impact of S-adenosylmethionine-dependent methyltransferase inhibitor, 3-deazaneplanocin A, on tissue injury and cognitive function in mice

Cancer patients display cognitive impairment due, at least partly, to the treatments. Additionally, chemotherapeutic treatments can lead to organ injury, limiting their use, and are likely to have negative impacts on patients’ quality of life. The aim of this study was to investigate the toxicity of 3-Deazaneplanocin A (DZNep) on several tissues and organs, as well as on cognitive functions. DZNep is an inhibitor of S-adenosylmethionine-dependent methyltransferase (in particular of the histone methyltransferase EZH2) which showed antitumoral functions in preclinical trials but whose effects on behavior and on organs (side effects) are not known.

Chronic injections of DZNep were performed intraperitoneally in male NMRI mice (2 mg/kg; i.p.; three times per week) during 8 weeks. A follow-up of body weight was assessed during all experiments. Histological analysis were performed on several organs. EZH2 expression and H3K27me3 were assayed by western-blot. Several behavioral tests were performed during treatment and 2 weeks after. A particular focus was made on spontaneous locomotor activity, cognitive functions (spontaneous alternation and recognition memory), and anxiety- and depression-related behavior. Hematological modifications were also assessed.

Chronic DZNep treatment transiently reduced animal growth. It had no effect on most organs but provoked a reversible splenomegaly, and persistent testis reduction and erythropoiesis. DZNep administration did not alter animal behavior.

In conclusion, this study is encouraging for the use of DZNep for cancer treatment. Indeed, it has no effect on animal behavior, conferring an advantageous safety, and induces irreversible side effects limited on testis which are unfortunately found in most chemotherapy treatments.

Identification of an easy to use 3D culture model to investigate invasion and anticancer drug response in chondrosarcomas

Background

Cytotoxic efficacy of anticancer drugs has been widely studied with monolayer-cultured cancer cells. However, the efficacy of drugs under two-dimensional (2D) culture condition usually differs from that of three-dimensional (3D) one. In the present study, an in vitro tumor tissue model was constructed using alginate hydrogel, and in vitro cytotoxic efficacy of two anticancer drugs (cisplatin and DZNep) was investigated in chondrosarcomas, and compared to in vivo response.

Methods

Three cell lines derived from human chondrosarcomas, CH2879, JJ012 and SW1353, were embedded in alginate hydrogel. Proliferation and survival were assayed by ATP measurement using Cell Titer-Glo luminescent cell viability assay kit, and by counting viable cells in beads. Collagen and COMP expression was determined by RT-PCR. Invasion/migration was estimated by counting cells leaving alginate beads and adhering to culture dish. Then, chondrosarcoma response to cisplatin and DZNep was compared between cells cultured in monolayer or embedded in alginate, and using chondrosarcoma xenografts in nude mice.

Results

Chondrosarcomas survived at least for 8 weeks, after embedment in alginate. However, only CH2879 cells could proliferate. Also, this cell line is more invasive than SW1353 and JJ012, which was coherent with the grade of their respective primary tumors. Furthermore, the expression of type II collagen was higher in chondrosarcomas cultured in 3D than in 2D. Interestingly, this 3D culture system allows to validate the absence of response of chondrosarcomas to cisplatin, and to predict the efficiency of DZNep to reduce chondrosarcoma growth in vivo.

Conclusions

This study validates alginate beads as a relevant 3D model to study cancer biology and tumor responses to biological treatments.

Hypoxia inducible factor 1 alpha down-regulates type i collagen through Sp3 transcription factor in human chondrocytes

Cartilage engineering is one challenging issue in regenerative medicine. Low oxygen tension or hypoxia inducible factor-1 (HIF-1α) gene therapy are promising strategies in the field of cartilage repair. Previously, we showed that hypoxia and its mediator HIF-1 regulate matrix genes expression (collagens and aggrecan). Here, we investigated the molecular mechanism involved in the regulation of type I collagen (COL1A1) by HIF-1 in human articular chondrocytes. We show that HIF-1α reduces COL1A1 transcription, through a distal promoter (-2300 to -1816 bp upstream transcription initiation site), containing two GC boxes that bind Sp transcription factors (Sp1/Sp3). Sp1 acts as a positive regulator but is not induced by HIF-1. COL1A1 inhibition caused by HIF-1 implies only Sp3, which accumulates and competes Sp1 binding on COL1A1 promoter. Additionally, Sp3 ectopic expression inhibits COL1A1, while Sp3 knockdown counteracts the downregulation of COL1A1 induced by HIF-1. In conclusion, we established a new regulatory model of COL1A1 regulation by HIF-1, and bring out its relationship with Sp3 transcription factor. In a fundamental level, these findings give insights in the mechanisms controlling COL1A1 gene expression. This may be helpful to improve strategies to impair type I collagen expression during chondrocyte differentiation for cartilage engineering. © 2016 IUBMB Life, 68(9):756-763, 2016.

Histone H3 Lysine 27 demethylases Jmjd3 and Utx are required for T-cell differentiation

Although histone H3 lysine 27 trimethylation (H3K27Me3) is associated with gene silencing, whether H3K27Me3 demethylation affects transcription and cell differentiation in vivo has remained elusive. To investigate this, we conditionally inactivated the two H3K27Me3 demethylases, Jmjd3 and Utx, in non-dividing intrathymic CD4(+) T-cell precursors. Here we show that both enzymes redundantly promote H3K27Me3 removal at, and expression of, a specific subset of genes involved in terminal thymocyte differentiation, especially S1pr1, encoding a sphingosine-phosphate receptor required for thymocyte egress. Thymocyte expression of S1pr1 was not rescued in Jmjd3- and Utx-deficient male mice, which carry the catalytically inactive Utx homolog Uty, supporting the conclusion that it requires H3K27Me3 demethylase activity. These findings demonstrate that Jmjd3 and Utx are required for T-cell development, and point to a requirement for their H3K27Me3 demethylase activity in cell differentiation.

TOL19-001 reduces inflammation and MMP expression in monolayer cultures of tendon cells

Background

Tendinopathies are tendon conditions associated with degeneration and disorganization of the matrix collagen fibers, tendon cells apoptosis and inflammation through up-regulation of proinflammatory cytokines, matrix metalloproteinase (MMP) expression, and prostaglandin E₂ (PGE₂) production. Currently, the pharmacological treatment is mainly based on non-steroidal anti-inflammatory drugs (NSAIDs) use and corticosteroid injections, which both can lead to numerous side effects for patients. TOL19-001 is a diet supplementary composed mostly of spirulina and glucosamine sulfate whose antioxidant properties could be helpful to treat tendinopathies while avoiding taking NSAIDs. In this study we developed an in vitro model of tendinopathy in order to evaluate the therapeutic potential of TOL19-001.

Methods

Tendon cells were cultured on monolayer and treated with interleukin-1β (IL-1β) or ciprofloxacin (CIP), and then, MMPs, PGE2 and collagen expression was evaluated by RT-PCR or Elisa. In addition, a cotreatment with increased doses of TOL19-001 was done. Toxicity of TOL19-001 was evaluated using a metabolic activity assay.

Results

This study demonstrates that IL-1β mimics some aspects of tendinopathies with PGE2 induction, MMP expression (mostly MMP1 and MMP3), and increases of type III/I collagen ratio. CIP, meanwhile, leads to an increase of MMP2 and p65 mRNA, whereas it reduces TIMP1 expression. Scleraxis expression was also increased by CIP whereas it was decreased by IL-1β treatment. Besides, TOL19-001 cotreatment suppresses tendon cell inflammation in vitro, marked by the downregulation of PGE2, MMPs and type III collagen in IL-1β stimulated-cells. TOL19-001 also represses CIP induced-changes.

Conclusions

These findings indicate that TOL19-001 exerts anti-inflammatory effects on tendon cells, which might explain why TOL19-001 diet may improve tendon function in patients with tendon injury. Future research is required to determine TOL19-001 effect on injured or overused tendons in vivo.

Anti-inflammatory effects of an injectable copolymer of fatty acids (Ara 3000 beta®) in joint diseases

Background

In inflammatory joint disease, such as osteoarthritis or arthritis, there is an increased level of pro-inflammatory cytokines, such as interleukin-1β. These cytokines stimulate the expression and release of matrix metalloproteases (MMP), leading to the degradation of cartilage extracellular matrix and subsequently mobility difficulty and suffering for patients. The aim of this study was to examine the therapeutic potential of a fatty acid copolymer in in vitro and in vivo models of cartilage inflammation.

Methods

Inflammation was mimicked in vitro by treatment of human articular chondrocytes with interleukin-1β. Effects of a co-treatment with a copolymer of fatty acids (Ara 3000 beta®) were determined by evaluating MMP production by RT-PCR and ELISA, NO release by Griess assay, and PGE2 expression by ELISA. In addition, in vivo analysis (evolution of weight and edema) were also performed after injection of Freund adjuvant in rats treated or not with the copolymer of fatty acids.

Results

The copolymer of fatty acids clearly reduces inflammation in joint. In vitro, it impairs IL1 stimulated-MMP production and release, as well as the release of NO and PGE2 and the activation of NFκB. Furthermore, in vivo experiments using adjuvant induced-arthritis corroborates the anti-inflammatory effects of the copolymer of fatty acids, with a reduction of edemas, erythemas and ankylosis in arthritic rats.

Conclusions

The results support the hypothesis that a copolymer of fatty acids, such as Ara 3000 beta®, is a powerful anti-inflammatory compounds, suggesting that it has a potential for preventing cartilage degradation associated with chronic inflammatory joint disease.

Type II TGFβ receptor modulates chondrocyte phenotype

Aging is one of the major risk factors of osteoarthritis. This pathology during which chondrocytes undergo modifications of their phenotype may result from alteration of transforming growth factor β (TGFβ) signaling. This study investigates the role of TGFβ response in the process of chondrocyte dedifferentiation/redifferentiation. Dedifferentiation was induced by successive passages of human articular chondrocytes, whereas their redifferentiation was performed by three-dimensional culture in alginate. Human mesenchymal stem cells were obtained from bone marrow and differentiated into chondrocyte-like phenotype by three-dimensional culture, embedded in the same scaffold. Protein and mRNA levels were analyzed by Western blot and real-time reverse transcription PCR. Regulatory mechanism was investigated using specific inhibitors (mithramycin), mRNA silencing or decoy oligonucleotides, and expression vectors. Chondrocyte dedifferentiation interfered with TGFβ signaling by decreasing TβRII mRNA and protein levels and subsequent TGFβ response. TβRII ectopic expression in passaged chondrocytes permitted to increase the expression of several matrix genes, such as aggrecan or type II collagen. Redifferentiation of passaged chondrocytes permitted to restore, at least in part, TβRII expression and was related to differentiation of human bone marrow mesenchymal stem cells toward chondrocytes, where both specific protein 1 (Sp1) and TβRII mRNA levels were increased. Moreover, Sp1 manipulation by silencing or ectopic expression and pharmacologic inhibition revealed a link between expression levels of this transcriptional factor, which is crucial for constitutive expression of TβRII in cartilage, and TGFβ response. Therefore, these data permit us to suggest an important role of TβRII expression in the maintenance of chondrocyte phenotype, which is altered with age, and bring new insights in our understanding of chondrogenesis process.

Enhanced hyaline cartilage matrix synthesis in collagen sponge scaffolds by using siRNA to stabilize chondrocytes phenotype cultured with bone morphogenetic protein-2 under hypoxia

Cartilage healing by tissue engineering is an alternative strategy to reconstitute functional tissue after trauma or age-related degeneration. However, chondrocytes, the major player in cartilage homeostasis, do not self-regenerate efficiently and lose their phenotype during osteoarthritis. This process is called dedifferentiation and also occurs during the first expansion step of autologous chondrocyte implantation (ACI). To ensure successful ACI therapy, chondrocytes must be differentiated and capable of synthesizing hyaline cartilage matrix molecules. We therefore developed a safe procedure for redifferentiating human chondrocytes by combining appropriate physicochemical factors: hypoxic conditions, collagen scaffolds, chondrogenic factors (bone morphogenetic protein-2 [BMP-2], and insulin-like growth factor I [IGF-I]) and RNA interference targeting the COL1A1 gene. Redifferentiation of dedifferentiated chondrocytes was evaluated using gene/protein analyses to identify the chondrocyte phenotypic profile. In our conditions, under BMP-2 treatment, redifferentiated and metabolically active chondrocytes synthesized a hyaline-like cartilage matrix characterized by type IIB collagen and aggrecan molecules without any sign of hypertrophy or osteogenesis. In contrast, IGF-I increased both specific and noncharacteristic markers (collagens I and X) of chondrocytes. The specific increase in COL2A1 gene expression observed in the BMP-2 treatment was shown to involve the specific enhancer region of COL2A1 that binds the trans-activators Sox9/L-Sox5/Sox6 and Sp1, which are associated with a decrease in the trans-inhibitors of COL2A1, c-Krox, and p65 subunit of NF-kappaB. Our procedure in which BMP-2 treatment under hypoxia is associated with a COL1A1 siRNA, significantly increased the differentiation index of chondrocytes, and should offer the opportunity to develop new ACI-based therapies in humans.

Molecular mechanism of hypoxia-induced chondrogenesis and its application in in vivo cartilage tissue engineering

Cartilage engineering is one of the most challenging issue in regenerative medicine, due to its limited self-ability to repair. Here, we assessed engineering of cartilage tissue starting from human bone marrow (hBM) stem cells under hypoxic environment and delineated the mechanism whereby chondrogenesis could be conducted without addition of exogenous growth factors. hBM stem cells were cultured in alginate beads and chondrogenesis was monitored by chondrocyte phenotypic markers. Activities and roles of Sox and HIF-1α transcription factors were investigated with complementary approaches of gain and loss of function and provided evidences that HIF-1α is essential for hypoxic induction of chondrogenesis. Thereafter, hBM cells and human articular chondrocytes (HAC) underwent chondrogenesis by 3D and hypoxic culture for 7 days or by ectopic expression of HIF-1α. After subcutaneous implantation of 3 weeks into athymic mice, tissue analysis showed that hypoxia or HIF-1α overexpression is effective and sufficient to induce chondrocyte phenotype in hBM cells, without use of exogenous growth factors. Therefore, this study brings interesting data for a simple and affordable system in biotechnology of cartilage engineering.

Asporin expression is highly regulated in human chondrocytes

A significant association between a polymorphism in the D repeat of the gene encoding asporin and osteoarthritis, the most frequent of articular diseases, has been recently reported. The goal of the present study was to investigate the expression of this new class I small leucine-rich proteoglycan (SLRP) in human articular chondrocytes. First, we studied the modulation of asporin (ASPN) expression by cytokines by Western blot and reverse transcription-polymerase chain reaction. Interleukin-1β and tumor necrosis factor-α downregulated ASPN, whereas transforming growth factor-β1 (when incubated in a serum-free medium) upregulated it. Similarly to proinflammatory cytokines, chondrocyte dedifferentiation induced by a successive passages of cells was accompanied by a decreased asporin expression, whereas their redifferentiation by three-dimensional culture restored its expression. Finally, we found an important role of the transcription factor Sp1 in the regulation of ASPN expression. Sp1 ectopic expression increased ASPN mRNA level and promoter activity. In addition, using gene reporter assay and electrophoretic mobility shift assay, we showed that Sp1 mediated its effect through a region located between -473 and -140 bp upstream of the transcription start site in ASPN gene. In conclusion, this report is the first study on the regulation of asporin expression by different cytokines in human articular chondrocytes. Our data indicate that the expression of this gene is finely regulated in cartilage and suggest a major role of Sp1.

Modulation of transforming growth factor beta signalling pathway genes by transforming growth factor beta in human osteoarthritic chondrocytes: involvement of Sp1 in both early and late response cells to transforming growth factor beta

Introduction

Transforming growth factor beta (TGFβ) plays a central role in morphogenesis, growth, and cell differentiation. This cytokine is particularly important in cartilage where it regulates cell proliferation and extracellular matrix synthesis. While the action of TGFβ on chondrocyte metabolism has been extensively catalogued, the modulation of specific genes that function as mediators of TGFβ signalling is poorly defined. In the current study, elements of the Smad component of the TGFβ intracellular signalling system and TGFβ receptors were characterised in human chondrocytes upon TGFβ1 treatment.

Methods

Human articular chondrocytes were incubated with TGFβ1. Then, mRNA and protein levels of TGFβ receptors and Smads were analysed by RT-PCR and western blot analysis. The role of specific protein 1 (Sp1) was investigated by gain and loss of function (inhibitor, siRNA, expression vector).

Results

We showed that TGFβ1 regulates mRNA levels of its own receptors, and of Smad3 and Smad7. It modulates TGFβ receptors post-transcriptionally by affecting their mRNA stability, but does not change the Smad-3 and Smad-7 mRNA half-life span, suggesting a potential transcriptional effect on these genes. Moreover, the transcriptional factor Sp1, which is downregulated by TGFβ1, is involved in the repression of both TGFβ receptors but not in the modulation of Smad3 and Smad7. Interestingly, Sp1 ectopic expression permitted also to maintain a similar expression pattern to early response to TGFβ at 24 hours of treatment. It restored the induction of Sox9 and COL2A1 and blocked the late response (repression of aggrecan, induction of COL1A1 and COL10A1).

Conclusions

These data help to better understand the negative feedback loop in the TGFβ signalling system, and enlighten an interesting role of Sp1 to regulate TGFβ response.

Interleukin-1beta up-regulation of Smad7 via NF-kappaB activation in human chondrocytes

OBJECTIVE

We have previously shown that interleukin-1beta (IL-1beta) impairs transforming growth factor beta (TGFbeta) signaling through TGFbeta receptor type II (TGFbetaRII) down-regulation and Smad7 up-regulation. This mechanism could account for the reduced responsiveness of osteoarthritic chondrocytes to TGFbeta and the cartilage breakdown linked to this disease. The aim of this study was to investigate the molecular mechanism underlying the IL-1beta-induced stimulation of Smad7 in human articular chondrocytes.

METHODS

Human articular chondrocytes were treated with IL-1beta in the presence of TGFbeta1, pyrrolidine dithiocarbamate (a repressor of the NF-kappaB pathway), or cycloheximide. Then, steady-state messenger RNA and protein levels were estimated by real-time reverse transcription-polymerase chain reaction and immunocytology. In addition, transient transfections of p65 expression vector or p65-targeted short hairpin RNA were performed to define the effect of NF-kappaB on Smad7 expression.

RESULTS

TGFbetaRII overexpression restored the TGFbeta response of human articular chondrocytes. However, this effect was transient, implying that a secondary mechanism was responsible for the alteration of the TGFbeta response with long-term exposure to IL-1beta. Moreover, IL-1beta caused a late induction of the inhibitory Smad7. This effect was direct, since it did not require de novo synthesis. In addition, we established, by experiments with gain/loss of function, that the up-regulation of Smad7 by IL-1beta is mediated through the NF-kappaB pathway, especially the p65 subunit.

CONCLUSION

These findings clarify the regulatory process of IL-1beta on Smad7 expression. Understanding the molecular basis of IL-1beta induction of Smad7 and the reduction of chondrocyte responsiveness to TGFbeta provides new insights into the molecular mechanisms of osteoarthritis and may facilitate the identification of novel approaches for its treatment.

Chondroitin sulfate modulation of matrix and inflammatory gene expression in IL-1beta-stimulated chondrocytes--study in hypoxic alginate bead cultures

OBJECTIVE

To determine the effect of avian chondroitin sulfate (CS) on interleukin-1beta (IL-1beta)-induced expression of genes related to catabolic, anabolic and inflammatory aspects in chondrocytes cultured in hypoxic alginate beads.

DESIGN

Articular chondrocytes from bovine metacarpal joint were isolated and cultured in alginate beads, using low oxygen atmosphere (5% O2). After 1-week exposure to CS (1, 10 and 100microg/ml), they were treated by recIL-1beta (10ng/ml) for 24 or 48h, in the presence of CS. RNA was extracted and used to determine, by quantitative reverse transcription-polymerase chain reaction, the steady-state levels of mRNAs encoding several genes related to anabolic, catabolic and inflammatory aspects. Glycosaminoglycan (GAG) synthesis was also assayed by 35S-sulfate incorporation.

RESULTS

CS decreased IL-1beta-induced expression of matrix metalloproteases-1, -3 and -13 and aggrecanases-1 and -2. It slightly enhanced the aggrecan core protein mRNA and the GAG synthesis. Inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) mRNA levels were found to be reduced by CS treatment. However, no CS-induced decrease of NO was observed in IL-1beta-treated chondrocytes, whereas prostaglandin E2 production was diminished in correlation with the COX-2 mRNA amounts. Furthermore, CS was capable of counteracting IL-1beta-depressed expression of transforming growth factor-beta (TGF-beta) receptors.

CONCLUSIONS

CS can repress expression of genes encoding proteolytic enzymes involved in cartilage degradation. It also inhibits IL-1beta-induced expression of the pro-inflammatory genes iNOS and COX-2 and restores TGF-beta receptors I and II (TGF-betaRI and RII) mRNA levels. These data suggest that CS may exert both chondroprotective and anti-inflammatory limited effects on articular cartilage that could have long-term beneficial action on the osteoarthritic process.

NFkappaB mediates IL-1beta-induced down-regulation of TbetaRII through the modulation of Sp3 expression

We previously showed that interleukin-1beta (IL-1beta) down-regulation of type II TGFbeta receptor (TbetaRII) involves NFkappaB pathway and requires de novo synthesis of a yet unknown protein. Here, we demonstrate that this effect is mediated through Sp1 site located at position -25 of human TbetaRII promoter. Inhibition of transcription factors binding (decoy oligonucleotides or mithramycin) abolished IL-1beta effect. EMSA and ChIP revealed that this treatment induced Sp3 binding to cis-sequence whereby IL-1beta exerts its transcriptional effects whereas it decreased that of Sp1. Moreover, although the cytokine did not modulate Sp1 expression, it increased that of Sp3 via NFkappaB pathway. Experiments of gain and loss of function clearly showed that Sp3 inhibited TbetaRII expression whereas its silencing abolished IL-1beta effect. In addition, both Sp1 and Sp3 were found to interact with NFkappaB, which therefore may indirectly interact with TbetaRII pro moter. Altogether, these data suggest that IL-1beta decreases TbetaRII expression by inducing Sp3 via NFkappaB and its binding on core promote at the expense of Sp1, which could explain the loss of cell responsiveness in certain conditions. These findings bring new insights in the knowledge of the interference between two antagonistic transduction pathways involved in multiple physiopathological processes.

Interleukin-1beta impairment of transforming growth factor beta1 signaling by down-regulation of transforming growth factor beta receptor type II and up-regulation of Smad7 in human articular chondrocytes

OBJECTIVE

Extracellular matrix deposition is tightly controlled by a network of regulatory cytokines. Among them, interleukin-1beta (IL-1beta) and transforming growth factor beta1 (TGFbeta1) have been shown to play antagonistic roles in tissue homeostasis. The purpose of this study was to determine the influence of IL-1beta on TGFbeta receptor type II (TGFbetaRII) regulation and TGFbeta1 responsiveness in human articular chondrocytes.

METHODS

TGFbeta1-induced gene expression was analyzed through plasminogen activator inhibitor 1 and p3TP-Lux induction. Receptor-activated Smad (R-Smad) phosphorylation, TGFbeta receptors, and Smad expression were determined by Western blotting and real-time reverse transcription-polymerase chain reaction techniques. Signaling pathways were investigated using specific inhibitors, messenger RNA (mRNA) silencing, and expression vectors.

RESULTS

IL-1beta down-regulated TGFbetaRII expression at both the protein and mRNA levels and led to inhibition of the TGFbeta1-induced gene expression and Smad2/3 phosphorylation. Moreover, IL-1beta strongly stimulated the expression of inhibitory Smad7. TGFbetaRII overexpression abolished the loss of TGFbeta1 responsiveness induced by IL-1beta. The decrease in TGFbetaRII required de novo protein synthesis and involved both the NF-kappaB and JNK pathways.

CONCLUSION

We demonstrate that IL-1beta impairs TGFbeta1 signaling through down-regulation of TGFbetaRII, which is mediated by the p65/NF-kappaB and activator protein 1/JNK pathways, and secondarily through the up-regulation of Smad7. These findings show that there is cross-talk in the signaling of 2 regulatory cytokines involved in inflammation.

Comparative effects of 2 antioxidants, selenomethionine and epigallocatechin-gallate, on catabolic and anabolic gene expression of articular chondrocytes

OBJECTIVE

. To determine the effects of selenomethionine (Se-met) and epigallocatechin-gallate (EGCg) on gene expression, activation of mitogen-activating kinases, and DNA binding of nuclear factor-kappaB (NF-kappaB) and apolipoprotein-1 (AP-1) in articular chondrocytes.

METHODS

Chondrocytes, cultured in low-oxygen tension, were pretreated with L-selenomethionine or EGCg for 24 h, followed by interleukin 1 (IL-1beta) for 1 h (nuclear and cytoplasmic extracts) or 24 h (RNA extraction). Reverse transcription-polymerase chain reaction was performed to determine mRNA levels of matrix metalloproteinases (MMP-1, -3, -13), aggrecanases (-1, -2), IL-1beta, inducible nitric oxide synthase, cyclooxygenases (-1, -2), type II collagen and aggrecan, and transforming growth factor-beta (TGF-beta1, -2, -3) and their receptors I and II. Activity of mitogen-activating protein kinases (MAPK) was assayed by Western blot and AP-1/NF-kB DNA binding by electrophoretic mobility shift assay.

RESULTS

Pretreatment with 0.5 microM Se-met prevented IL-1beta-induced MMP-1 and aggrecanase-1 expression, and reduced the cytokine inhibitory effect on type II collagen, aggrecan core protein, and TGF-beta receptor II (TGF-betaRII) mRNA levels. EGCg was more efficient in modulating the effects of IL-1beta on the genes studied. Whereas EGCg inhibited the IL-1beta-activated MAPK, NF-kappaB, and AP-1, Se-met stimulated that signaling pathway. This could account for the differential effects exerted by these antioxidants on chondrocytes.

CONCLUSION

Our data provide insights into the mechanisms whereby ECGg and selenium modulate chondrocyte metabolism. Despite their differential mechanisms of action, the 2 compounds may exert global beneficial effects on articular cartilage.