Retinoic acid combines with interleukin-1 to promote the degradation of collagen from bovine nasal cartilage: Matrix metalloproteinases-1 and -13 are involved in cartilage collagen breakdown

Substance P promotes transforming growth factor-β-induced collagen synthesis in human corneal fibroblasts

Corneal fibroblasts maintain homeostasis of the corneal stroma by mediating the synthesis and degradation of extracellular collagen, and these actions are promoted by transforming growth factor-β (TGF-β) and interleukin-1β (IL-1β), respectively. The cornea is densely innervated with sensory nerve fibers that are not only responsible for sensation but also required for physiological processes such as tear secretion and wound healing. Loss or dysfunction of corneal nerves thus impairs corneal epithelial wound healing and can lead to neurotrophic keratopathy. The sensory neurotransmitter substance P (SP) promotes corneal epithelial wound healing by enhancing the stimulatory effects of growth factors and fibronectin. We have now investigated the role of SP in collagen metabolism mediated by human corneal fibroblasts in culture. Although SP alone had no effect on collagen synthesis or degradation by these cells, it promoted the stimulatory effect of TGF-β on collagen type I synthesis without affecting that of IL-1β on the expression of matrix metalloproteinase-1. This effect of SP on TGF-β-induced collagen synthesis was accompanied by activation of p38 mitogen-activated protein kinase (MAPK) signaling and was attenuated by pharmacological inhibition of p38 or of the neurokinin-1 receptor. Our results thus implicate SP as a modulator of TGF-β-induced collagen type I synthesis by human corneal fibroblasts, and they suggest that loss of this function may contribute to the development of neurotrophic keratopathy.NEW & NOTEWORTHY This study investigates the role of substance P (SP) in collagen metabolism mediated by human corneal fibroblasts in culture. We found that, although SP alone had no effect on collagen synthesis or degradation by corneal fibroblasts, it promoted the stimulatory effect of transforming growth factor-β on collagen type I synthesis without affecting that of interleukin-1β on the expression of matrix metalloproteinase-1.

HDAC6 regulates NF-κB signalling to control chondrocyte IL-1-induced MMP and inflammatory gene expression

Elevated pro-inflammatory signalling coupled with catabolic metalloproteinase expression is a common feature of arthritis, leading to cartilage damage, deterioration of the joint architecture and the associated pain and immobility. Countering these processes, histone deacetylase inhibitors (HDACi) have been shown to suppress matrix metalloproteinase (MMP) expression, block cytokine-induced signalling and reduce the cartilage degradation in animal models of the arthritis. In order to establish which specific HDACs account for these chondro-protective effects an HDAC1-11 RNAi screen was performed. HDAC6 was required for both the interleukin (IL)-1 induction of MMP expression and pro-inflammatory interleukin expression in chondrocytes, implicating an effect on NF-κB signalling. Depletion of HDAC6 post-transcriptionally up-regulated inhibitor of κB (IκB), prevented the nuclear translocation of NF-κB subunits and down-regulated NF-κB reporter activation. The pharmacological inhibition of HDAC6 reduced MMP expression in chondrocytes and cartilage collagen release. This work highlights the important role of HDAC6 in pro-inflammatory signalling and metalloproteinase gene expression, and identifies a part for HDAC6 in the NF-κB signalling pathway. By confirming the protection of cartilage this work supports the inhibition of HDAC6 as a possible therapeutic strategy in arthritis.

Guggulipid ameliorates adjuvant-induced arthritis and liver oxidative damage by suppressing inflammatory and oxidative stress mediators

BACKGROUND

Arthritis is a common degenerative joint disease characterized by deterioration of articular cartilage, subchondral bone, and associated with immobility, pain and inflammation. The incessant action of reactive oxygen species (ROS) during progressive arthritis causes severe oxidative damage to vital organs and circulatory system.

PURPOSE

In this study we investigated the ability of guggulipid (GL), a lipid rich extract from the gum resin of the plant Commiphora whighitii to suppress the progressive arthritis and associated liver oxidative stress both in vivo and in vitro.

STUDY DESIGN/METHODS

The anti-arthritic ability of GL was demonstrated in vitro using IL-1β stimulated bovine nasal cartilage model and in vivo Freund's complete adjuvant-induced arthritic rat model. Collagen/proteoglycan degradation and pro-inflammatory mediators were monitored in the harvested culture medium of nasal cartilage by estimating the levels of matrix metalloproteinases (MMPs), hydroxy proline, glycosaminoglycans and inflammatory mediators. Further, anti-arthritic ability of GL was evaluated in vivo by measuring enzymatic and non-enzymatic mediators of cartilage degradation, inflammation and oxidative stress markers.

RESULTS

GL significantly inhibited the IL-1β stimulated cartilage degradation in vitro by mitigating the MMPs activity, collagen degradation and secretion of pro-inflammatory mediators. Further, GL significantly reduced the adjuvant-induced paw swelling and body weight loss in vivo. GL remarkably reduced the MMPs and hyaluronidases activities in serum and bone homogenate along with altered hematological parameters. GL also mitigated the elevated bone resorbing enzymes cathepsins, exoglycosidases and phosphatases. Additionally, GL effectively mitigated ROS and oxidative stress-mediators recuperating the altered serum/liver oxidative stress and liver damage incurred during arthritic progression.

CONCLUSION

In summary, the study clearly demonstrates the protective efficacy of GL against arthritis and its associated oxidative stress, particularly, liver oxidative damage. Hence, GL could be a potential alternative and complementary medicine to treat inflammatory joint diseases.

Role of Fat-Soluble Vitamins in Osteoarthritis Management

Osteoarthritis (OA) is a chronic degenerative joint disease, in which metabolic imbalance in bone is observed. The pathological mechanism of metabolic imbalance is not clear yet, but the nutritional factors, particularly the vitamins, might be intrinsic to the development and progression of OA. In this review article, we have explored databases such as PubMed, Scopus, and Google Scholar articles until the beginning of 2017 and reviewed the role of fat-soluble vitamins in pathological and therapeutic aspects of OA. Vitamin D plays an important role in the development and maintenance of the skeleton, as well as bone and cartilage metabolism, and its deficiency is implicated in the pathological process of OA. Vitamin E enhances chondrocyte growth and exhibits an anti-inflammatory activity, as well as plays an important role in the prevention of cartilage degeneration. In human OA cartilage, vitamin K deficiency produces abnormal growth plate calcification and inappropriate mineralization of cartilage. Thus, these fat-soluble vitamins play a key role in the pathophysiology of OA, and supplementation of these vitamins may provide innovative approaches for OA management. However, vitamin A has a different role, which is a regulator of cartilage and skeletal formation. When metabolite levels of vitamin A are elevated in synovial fluid, they appear to drive OA development. The role of inhibitors of vitamin A here remains unclear. More investigations are needed to examine the effects of fat-soluble vitamins on the various molecular pathways of OA, as well as to assess the efficacy and safety of their usage clinically.

Identifying chondroprotective diet-derived bioactives and investigating their synergism

Osteoarthritis (OA) is a multifactorial disease and nutrition is a modifiable factor that may contribute to disease onset or progression. A detailed understanding of mechanisms through which diet-derived bioactive molecules function and interact in OA is needed. We profiled 96 diet-derived, mainly plant-based bioactives using an in vitro model in chondrocytes, selecting four candidates for further study. We aimed to determine synergistic interactions between bioactives that affected the expression of key genes in OA. Selected bioactives, sulforaphane, apigenin, isoliquiritigenin and luteolin, inhibited one or more interleukin-1-induced metalloproteinases implicated in OA (MMP1, MMP13, ADAMTS4, ADAMTS5). Isoliquiritigenin and luteolin showed reactive oxygen species scavenging activity in chondrocytes whereas sulforaphane had no effect and apigenin showed only a weak trend. Sulforaphane inhibited the IL-1/NFκB and Wnt3a/TCF/Lef pathways and increased TGFβ/Smad2/3 and BMP6/Smad1/5/8 signalling. Apigenin showed potent inhibition of the IL-1/NFκB and TGFβ/Smad2/3 pathways, whereas luteolin showed only weak inhibition of the IL-1/NFκB pathway. All four bioactives inhibited cytokine-induced aggrecan loss from cartilage tissue explants. The combination of sulforaphane and isoliquiritigenin was synergistic for inhibiting MMP13 gene expression in chondrocytes. We conclude that dietary-derived bioactives may be important modulators of cartilage homeostasis and synergistic relationships between bioactives may have an anti-inflammatory and chondroprotective role.

Matriptase Induction of Metalloproteinase-Dependent Aggrecanolysis In Vitro and In Vivo: Promotion of Osteoarthritic Cartilage Damage by Multiple Mechanisms

Objective

To assess the ability of matriptase, a type II transmembrane serine proteinase, to promote aggrecan loss from the cartilage of patients with osteoarthritis (OA) and to determine whether its inhibition can prevent aggrecan loss and cartilage damage in experimental OA.

Methods

Aggrecan release from human OA cartilage explants and human stem cell–derived cartilage discs was evaluated, and cartilage‐conditioned media were used for Western blotting. Gene expression was analyzed by real‐time polymerase chain reaction. Murine OA was induced by surgical destabilization of the medial meniscus, and matriptase inhibitors were administered via osmotic minipump or intraarticular injection. Cartilage damage was scored histologically and aggrecan cleavage was visualized immunohistochemically using specific neoepitope antibodies.

Results

The addition of soluble recombinant matriptase promoted a time‐dependent release of aggrecan (and collagen) from OA cartilage, which was sensitive to metalloproteinase inhibition and protease‐activated receptor 2 antagonism. Although engineered human (normal) cartilage discs failed to release aggrecan following matriptase addition, both matrix metalloproteinase– and aggrecanase‐mediated cleavages of aggrecan were detected in human OA cartilage. Additionally, while matriptase did not directly degrade aggrecan, it promoted the accumulation of low‐density lipoprotein receptor–related protein 1 (LRP‐1) in conditioned media of the OA cartilage explants. Matriptase inhibition via neutralizing antibody or small molecule inhibitor significantly reduced cartilage damage scores in murine OA, which was associated with reduced generation of metalloproteinase‐mediated aggrecan cleavage.

Conclusion

Matriptase potently induces the release of metalloproteinase‐generated aggrecan fragments as well as soluble LRP‐1 from OA cartilage. Therapeutic targeting of matriptase proteolytic activity reduces metalloproteinase activity, further suggesting that this serine proteinase may have potential as a disease‐modifying therapy in OA.

Isothiocyanates are detected in human synovial fluid following broccoli consumption and can affect the tissues of the knee joint

Osteoarthritis is a major cause of disability and there is no current pharmaceutical treatment which can prevent the disease or slow its progression. Dietary advice or supplementation is clearly an attractive option since it has low toxicity and ease of implementation on a population level. We have previously demonstrated that sulforaphane, a dietary isothiocyanate derived from its glucosinolate precursor which is found in broccoli, can prevent cartilage destruction in cells, in in vitro and in vivo models of osteoarthritis. As the next phase of this research, we enrolled 40 patients with knee osteoarthritis undergoing total knee replacement into a proof-of-principle trial. Patients were randomised to either a low or high glucosinolate diet for 14 days prior to surgery. We detected ITCs in the synovial fluid of the high glucosinolate group, but not the low glucosinolate group. This was mirrored by an increase in ITCs and specifically sulforaphane in the plasma. Proteomic analysis of synovial fluid showed significantly distinct profiles between groups with 125 differentially expressed proteins. The functional consequence of this diet will now be tested in a clinical trial.

Sulforaphane represses matrix-degrading proteases and protects cartilage from destruction in vitro and in vivo

Objective

Sulforaphane (SFN) has been reported to regulate signaling pathways relevant to chronic diseases. The aim of this study was to investigate the impact of SFN treatment on signaling pathways in chondrocytes and to determine whether sulforaphane could block cartilage destruction in osteoarthritis.

Methods

Gene expression, histone acetylation, and signaling of the transcription factors NF-E2–related factor 2 (Nrf2) and NF-κB were examined in vitro. The bovine nasal cartilage explant model and the destabilization of the medial meniscus (DMM) model of osteoarthritis in the mouse were used to assess chondroprotection at the tissue and whole-animal levels.

Results

SFN inhibited cytokine-induced metalloproteinase expression in primary human articular chondrocytes and in fibroblast-like synovial cells. SFN acted independently of Nrf2 and histone deacetylase activity to regulate metalloproteinase expression in human articular chondrocytes but did mediate prolonged activation of JNK and p38 MAPK. SFN attenuated NF-κB signaling at least through inhibition of DNA binding in human articular chondrocytes, with decreased expression of several NF-κB–dependent genes. Compared with cytokines alone, SFN (10 μM) abrogated cytokine-induced destruction of bovine nasal cartilage at both the proteoglycan and collagen breakdown levels. An SFN-rich diet (3 μmoles/day SFN versus control chow) decreased the arthritis score in the DMM model of osteoarthritis in the mouse, with a concurrent block of early DMM-induced gene expression changes.

Conclusion

SFN inhibits the expression of key metalloproteinases implicated in osteoarthritis, independently of Nrf2, and blocks inflammation at the level of NF-κB to protect against cartilage destruction in vitro and in vivo.

MMP-1 overexpression induced by IL-1β: possible mechanism for inflammation in degenerative lumbar facet joint

BACKGROUND

More and more attention has been focused on the inflammation or degeneration caused by biochemical factors in radiculopathy during lumbar facet joint degeneration. This study was designed to examine the expression and relationship of MMP-1/TIMP-1 and interleukin-1β (IL-1β), and to analyze the possible mechanism in degenerative lumbar facet joint disease.

METHODS

Lumbar facet joint cartilage and synovial tissues in 36 cases of posterior lumbar surgery were harvested to investigate IL-1β and MMP-1/TIMP-1 by immunohistochemistry and Western blot analysis. Double labeling immunofluorescence and real-time PCR, respectively, were used to assess the relationship between IL-1β and MMP-1.

RESULTS

IL-1β and MMP-1 were low in the lumbar disc herniation (LDH) group, and increased markedly in the lumbar spinal canal stenosis (LSCS) group (P < 0.05). However, there is no significant difference of TIMP-1 between LDH group and LSCS group (P > 0.05). Double staining results indicated that IL-1β overlapped with MMP-1 in the LSCS group. Moreover, real-time PCR results showed that MMP-1 mRNA in chondrocytes in vitro was affected in a dose- and time-dependent manner in response to IL-1β stimulation.

CONCLUSIONS

Overexpression of MMP-1, induced by IL-1β, plays an important role in the inflammatory process of lumbar facet joint degeneration.

Combined prescription (OAH19T) of Aralia cordata Thunb and Cimicifuga heracleifolia Komar and its major compounds inhibit matrix proteinases and vascular endothelial growth factor through the regulation of mitogen-activated protein kinase pathway

ETHNOPHARMACOLOGICAL RELEVANCE

OAH19T, a new herbal extract from a mixture of Aralia cordata Thunb and Cimicifuga heracleifolia, is traditionally used for the treatment of arthritis in far East Asia. To investigate the chondroprotective effects of OAH19T on osteoarthritis was examined and compared with its major compounds pimaradienoic acid (PA) and ferulic acid (FA) of human osteoarthritis (OA) chondrocytes.

MATERIALS AND METHODS

Chondrocytes, alone or in the presence of IL-1β, were cultured with or without OAH19T, PA or FA (10, 20, 40 μg/ml). The release of sulfated glycosaminoglycan (GAG) was measured by colorimetric assay using 1,9-dimethylmethylene blue (DMB) reagent from the cultured media. The level of aggrecanases and VEGF was measured by reverse transcription polymerase chain reaction (RT-PCR). The expression of MMP-1 and MMP-3 analyzed by real time RT-PCR and enzyme-linked immunosorbent assay (ELISA). The phosphorylation of mitogen-activated protein kinases was performed by immunoblotting in OA chondrocytes. The proliferation was examined by the BrdU assay.

RESULTS

OAH19T markedly inhibited the release of proteoglycan and the degradation of aggrecan, in a dose-dependent manner in OA chondrocytes. OAH19T also inhibited the level of aggrecanase-1, aggrecanase-2, MMP-1, MMP-3, and VEGF in OA chondrocytes. PA and FA also inhibited the level of aggrecanase-2, MMP-3 and VEGF, while did not significantly affect the levels of aggrecanase-1, MMP-3 in OA chondrocytes. OAH19T exhibited the down-regulation of p38 MAP kinase unlike PA and FA in OA chondrocytes without cytotoxicity. In addition, p38 inhibitor SB203580 abolished the antiproliferative activity and proteoglycan degradation by OAH19T, while had no effect by PA or FA.

CONCLUSION

OAH19T have shown the chondroprotective effect by inhibiting cell proliferation, expression of cartilage-specific matrix proteinases and release of VEGF, but bigger than PA or FA, through down-regulation of p38 MAP kinase in human OA chondocyte. These results provide pharmacological basis for use in treatment of OA.

Development of an in vitro model of feline cartilage degradation

Osteoarthritis is the most common arthropathy of mammalian species including cats. Cartilage degradation is central to the disorder and here we present, for the first time, an in vitro model of feline cartilage degradation which will be useful for further studies in this target species. Feline articular cartilage explant cultures were maintained for 28 days and in the presence of oncostatin M with and without interleukin (IL)-17, tumour necrosis factor (TNF), IL-1alpha, or IL-1beta. Media samples and digested cartilage explants were analysed for glycosaminoglycan (GAG) and collagen content. The combination of IL-1beta and OSM, both at 20 ng/ml, was able to promote GAG release to the greatest extent at 14 days. At 28 days, all groups showed relatively high release of GAG. At 14 days, only IL-1beta and OSM in combination were associated with a statistically significant increase in collagen release over and above control tissue. IL-1beta dose-response studies showed that an IL-1beta dose of 10 ng/ml promotes a statistically significant increase in GAG breakdown when used with OSM, and higher doses of IL-1beta did not result in significantly greater response. The model demonstrated both GAG and collagen degradation and will be of use for further understanding of feline cartilage metabolism and for screening of potential structure-modifying agents to be used in cats.

Protein kinase C isoforms zeta and iota mediate collagenase expression and cartilage destruction via STAT3- and ERK-dependent c-fos induction

The protein kinase C (PKC) signaling pathway is a major regulator of cellular functions and is implicated in pathologies involving extracellular matrix remodeling. Inflammatory joint disease is characterized by excessive extracellular matrix catabolism, and here we assess the role of PKC in the induction of the collagenases, matrix metalloproteinase (MMP)-1 and MMP-13, in human chondrocytes by the potent cytokine stimulus interleukin-1 (IL-1) in combination with oncostatin M (OSM). IL-1 + OSM-stimulated collagenolysis and gelatinase activity were ameliorated by pharmacological PKC inhibition in bovine cartilage, as was collagenase gene induction in human chondrocytes. Small interfering RNA-mediated silencing of PKC gene expression showed that both novel (nPKC delta, nPKC eta) and atypical (aPKC zeta, aPKC iota) isoforms were involved in collagenase induction by IL-1. However, MMP1 and MMP13 induction by IL-1 + OSM was inhibited only by aPKC silencing, suggesting that only atypical isoforms play a significant role in complex inflammatory milieus. Silencing of either aPKC led to diminished IL-1 + OSM-dependent extracellular signal-regulated kinase (ERK) and signal transducer and activator of transcription (STAT) 3 phosphorylation, and c-fos expression. STAT3 gene silencing or ERK pathway inhibition also resulted in loss of IL-1 + OSM-stimulated c-fos and collagenase expression. Silencing of c-fos and c-jun expression was sufficient to abrogate IL-1 + OSM-stimulated collagenase gene induction, and overexpression of both c-fos and c-jun was sufficient to drive transcription from the MMP1 promoter in the absence of a stimulus. Our data identify atypical PKC isozymes as STAT and ERK activators that mediate c-fos and collagenase expression during IL-1 + OSM synergy in human chondrocytes. aPKCs may constitute potential therapeutic targets for inflammatory joint diseases involving increased collagenase expression.

Proteinases involved in matrix turnover during cartilage and bone breakdown

The joint is a discrete unit that consists of cartilage, bone, tendon and ligaments. These tissues are all composed of an extracellular matrix made of collagens, proteoglycans and specialised glycoproteins that are actively synthesised, precisely assembled and subsequently degraded by the resident connective tissue cells. A balance is maintained between matrix synthesis and degradation in healthy adult tissues. Different classes of proteinases play a part in connective tissue turnover in which active proteinases can cleave matrix protein during resorption, although the proteinase that predominates varies between different tissues and diseases. The metalloproteinases are potent enzymes that, once activated, degrade connective tissue and are inhibited by tissue inhibitors of metalloproteinases (TIMPs); the balance between active matrix metalloproteinases and TIMPs determines, in many tissues, the extent of extracellular matrix degradation. The serine proteinases are involved in the initiation of activation cascades and some, such as elastase, can directly degrade the matrix. Cysteine proteinases are responsible for the breakdown of collagen in bone following the removal of the osteoid layer and the attachment of osteoclasts to the exposed bone surface. Various growth factors increase the synthesis of matrix and proteinase inhibitors, whereas cytokines (alone or in combination) can inhibit matrix synthesis and stimulate proteinase production and matrix destruction.

Ligands for retinoic acid receptors are elevated in osteoarthritis and may contribute to pathologic processes in the osteoarthritic joint

OBJECTIVE

Vitamin A derivatives, including all-trans-retinoic acid (ATRA), have a well-established role during skeletal development and limb formation and have been shown to have profound effects on chondrocyte phenotype. The aim of this study was to elucidate the effects of retinoids and components of the retinoid metabolic pathway on chondrocyte phenotype in the tibiofemoral joints of patients with osteoarthritis (OA), to show that the retinoids can have multiple effects relevant to the OA disease process.

METHODS

Human explant tissue and a chondrocyte-like cell line were treated with ATRA, and the responses of 4 key markers of chondrocyte phenotype were analyzed. In addition, the effects of ATRA on a number of novel genes associated with OA were assessed using a low-density microarray containing 80 disease marker genes.

RESULTS

Vitamin A metabolite levels were elevated in synovial fluid, serum, and cartilage from patients with OA. Expression profiling of a retinoic acid receptor alpha coactivator protein, P/CAF, demonstrated elevated expression in patients with OA, suggesting the potential for increased signaling via the retinoid receptors in the disease. ATRA increased the levels of matrix metalloproteinase 13 and aggrecanase activity in human cartilage explants and in a human chondrocyte cell line. Furthermore, ATRA altered the expression of a wide range of relevant genes, including the types I, II, IX, and XI collagen genes, toward a nonchondrogenic and OA-like phenotype.

CONCLUSION

These results suggest that retinoid signaling could have a central role in OA, and that components of the pathway may provide potential disease biomarkers or targets for therapeutic intervention.

Meniscal tissue explants response depends on level of dynamic compressive strain

OBJECTIVE

Following partial meniscectomy, the remaining meniscus is exposed to an altered loading environment. In vitro 20% dynamic compressive strains on meniscal tissue explants has been shown to lead to an increase in release of glycosaminoglycans from the tissue and increased expression of interleukin-1alpha (IL-1alpha). The goal of this study was to determine if compressive loading which induces endogenously expressed IL-1 results in downstream changes in gene expression of anabolic and catabolic molecules in meniscal tissue, such as MMP expression.

METHOD

Relative changes in gene expression of MMP-1, MMP-3, MMP-9, MMP-13, A Disintegrin and Metalloproteinase with ThromboSpondin 4 (ADAMTS4), ADAMTS5, TNFalpha, TGFbeta, COX-2, Type I collagen (COL-1) and aggrecan and subsequent changes in the concentration of prostaglandin E(2) released by meniscal tissue in response to varying levels of dynamic compression (0%, 10%, and 20%) were measured. Porcine meniscal explants were dynamically compressed for 2h at 1Hz.

RESULTS

20% dynamic compressive strains upregulated MMP-1, MMP-3, MMP-13 and ADAMTS4 compared to no dynamic loading. Aggrecan, COX-2, and ADAMTS5 gene expression were upregulated under 10% strain compared to no dynamic loading while COL-1, TIMP-1, and TGFbeta gene expression were not dependent on the magnitude of loading.

CONCLUSION

This data suggests that changes in mechanical loading of the knee joint meniscus from 10% to 20% dynamic strain can increase the catabolic activity of the meniscus.

Synergistic collagenase expression and cartilage collagenolysis are phosphatidylinositol 3-kinase/Akt signaling-dependent

The phosphatidylinositol 3-kinase (PI3K) signaling pathway has emerged as a major regulator of cellular functions and has been implicated in several pathologies involving remodeling of extracellular matrix (ECM). The end stage of inflammatory joint diseases is characterized by excessive ECM catabolism, and in this study we assess the role of PI3K signaling in the induction of collagenolytic matrix metalloproteinases (MMPs) in human chondrocytes. We used the most potent cytokine stimulus reported to promote cartilage ECM catabolism, namely interleukin-1 (IL-1) in combination with oncostatin M (OSM). Both OSM and IL-6 (in the presence of its soluble receptor), but not IL-1 nor leukemia inhibitory factor, induced Akt phosphorylation in human chondrocytes. Inhibition of PI3K signaling using LY294002 blocked IL-1+OSM-mediated Akt phosphorylation, induction of MMP-1 and MMP-13, and cartilage collagenolysis. To further explore the role of downstream substrates within the PI3K pathway, complementary use of small molecule inhibitors and specific small interfering RNAs demonstrated that the PI3K subunit p110alpha and Akt1 were required for MMP-1 mRNA induction. MMP-13 induction was also reduced by loss of function of these molecules and by a lack of p110delta, 3-phosphoinositide-dependent kinase-1 or Akt3. We therefore propose that the activities of specific elements of the PI3K signaling pathway, including Akt, are necessary for the synergistic induction of MMP-1 and MMP-13 and the cartilage breakdown stimulated by IL-1+OSM. Our data provide new insight into the mechanism of synergy between IL-1 and OSM and highlight new therapeutic targets for inflammatory joint diseases that aim to repress the expression of collagenases.

Evc is a positive mediator of Ihh-regulated bone growth that localises at the base of chondrocyte cilia

EVC is a novel protein mutated in the human chondroectodermal dysplasia Ellis-van Creveld syndrome (EvC; OMIM: 225500). We have inactivated Evc in the mouse and show that Evc(-/-) mice develop an EvC-like syndrome, including short ribs, short limbs and dental abnormalities. lacZ driven by the Evc promoter revealed that Evc is expressed in the developing bones and the orofacial region. Antibodies developed against Evc locate the protein at the base of the primary cilium. The growth plate of Evc(-/-) mice shows delayed bone collar formation and advanced maturation of chondrocytes. Indian hedgehog (Ihh) is expressed normally in the growth plates of Evc(-/-) mice, but expression of the Ihh downstream genes Ptch1 and Gli1 was markedly decreased. Recent studies have shown that Smo localises to primary cilia and that Gli3 processing is defective in intraflagellar transport mutants. In vitro studies using Evc(-/-) cells demonstrate that the defect lies downstream of Smo. Chondrocyte cilia are present in Evc(-/-) mice and Gli3 processing appears normal by western blot analysis. We conclude that Evc is an intracellular component of the hedgehog signal transduction pathway that is required for normal transcriptional activation of Ihh target genes.

Matrix metalloproteinase 10 promotion of collagenolysis via procollagenase activation: implications for cartilage degradation in arthritis

OBJECTIVE

We have previously reported the up-regulation of matrix metalloproteinase 10 (MMP-10) following treatment with the procatabolic stimulus of interleukin-1 (IL-1) and oncostatin M (OSM) in chondrocytes. Although MMP-10 is closely related to MMP-3, little is known about the role of MMP-10 in cartilage catabolism. The purpose of this study was to determine whether MMP-10 is expressed in connective tissue cells and to assess how it may contribute to cartilage collagenolysis.

METHODS

MMP gene expression was assessed by real-time polymerase chain reaction using RNA from human articular chondrocytes and synovial fibroblasts stimulated with IL-1 plus OSM or tumor necrosis factor alpha (TNFalpha) plus OSM. Synovial fluid levels of MMP-10 were determined by specific immunoassay. Recombinant procollagenases were used in activation studies. Immunohistochemistry assessed MMP-10 expression in diseased joint tissues.

RESULTS

MMP-10 expression was confirmed in both chondrocytes and synovial fibroblasts following stimulation with either IL-1 plus OSM or TNFalpha plus OSM, and MMP-10 was detected in synovial fluid samples from patients with various arthropathies. Exogenous MMP-10 significantly enhanced collagenolysis from IL-1 plus OSM-stimulated cartilage, and MMP-10 activated proMMP-1, proMMP-8, and proMMP-13. Immunohistochemistry revealed the presence of MMP-10 in the synovium and cartilage of an IL-1 plus OSM-induced model of arthritis as well as in samples of diseased human tissues.

CONCLUSION

We confirm that both synovial fibroblasts and articular chondrocytes express MMP-10 following treatment with procatabolic stimuli. Furthermore, the detectable levels of synovial fluid MMP-10 and the histologic detection of this proteinase in diseased joint tissues strongly implicate MMP-10 in the cartilage degradome during arthritis. The ability of MMP-10 to superactivate procollagenases that are relevant to cartilage degradation suggests that this activation represents an important mechanism by which this MMP contributes to tissue destruction in arthritis.

Understanding the role of tissue degrading enzymes and their inhibitors in development and disease

Cartilage and the underlying bone are destroyed in severe cases of arthritis preventing joints from functioning normally. Cartilage and bone collagen can be specifically cleaved by the collagenases, members of the matrix metalloproteinase family (MMPs), whilst cartilage aggrecan is degraded by members of the ADAMTS (A Disintegrin And Metalloproteinase with ThromboSpondin repeats) family of proteinases. Intracellular cysteine proteinases are involved in bone resorption by osteoclasts and the serine proteinases are involved in activating MMPs. Together, these enzymes act in concert during normal growth and development, especially within the growth plate; however they are also involved in tissue destruction during disease. Synthetic MMP inhibitors have been investigated as a means to block tissue destruction in arthritis but have been unsuccessful, although recent trials with doxycycline suggest this may block joint destruction in osteoarthritis. It is likely that combinations of therapy will be required to ensure that joint destruction is prevented in arthritis patients.

Retinoic acid and oncostatin M combine to promote cartilage degradation via matrix metalloproteinase-13 expression in bovine but not human chondrocytes

OBJECTIVES

Retinoic acid (RetA) and oncostatin M (OSM) have both been shown to mediate potent effects with respect to extracellular matrix integrity. This study assesses the effects of a RetA + OSM combination on cartilage catabolism.

METHODS

Animal and human cartilage samples were used to assess the ability of RetA + OSM to promote the release of collagen and proteoglycan fragments, which was determined by measuring glycosaminoglycan and hydroxyproline, respectively. Total collagenolytic and tissue inhibitor of metalloproteinases (TIMP) inhibitory activities were determined by bioassay, whilst gene expression of matrix metalloproteinases (MMPs) and TIMP-1 were determined by northern blotting. Immunohistochemistry was used to assess the presence of MMP-1 and -13 in resorbing cartilage explants.

RESULTS

Both agents alone induced proteoglycan release from bovine cartilage, whilst RetA-induced collagen release was variable. Reproducible and synergistic collagenolysis was observed with RetA + OSM, which appeared to be due to MMP-13. Similar collagen release was observed from porcine cartilage. Conversely, no collagen release was seen with human articular cartilage. In primary human chondrocytes, RetA + OSM failed to induce MMP-1 or -13 but caused a significant increase in TIMP-1 expression.

CONCLUSIONS

These novel observations show that the combination of RetA + OSM has profound effects on cartilage matrix turnover, but these effects are species-specific. A better understanding of the mechanism by which this combination differentially regulates MMP and TIMP expression in human chondrocytes could provide valuable insight into new therapeutic strategies aimed at the prevention of cartilage destruction.

Interleukin-1 in combination with oncostatin M up-regulates multiple genes in chondrocytes: Implications for cartilage destruction and repair

OBJECTIVE

To identify the genes up-regulated by interleukin-1 (IL-1) in combination with oncostatin M (OSM) in chondrocytes that may be involved in mechanisms of cartilage repair and degradation.

METHODS

Gene microarray and real-time polymerase chain reaction (PCR) experiments were performed using RNA from SW1353 chondrocytes and primary human articular chondrocytes. Sections prepared from murine joints, injected with adenovirus vectors overexpressing IL-1 and/or OSM, were analyzed by immunohistochemistry for selected proteins.

RESULTS

The combination of IL-1 and OSM markedly up-regulated the expression of various genes, including matrix metalloproteinases (MMPs), cytokines, chemokines, extracellular matrix components, and genes involved in signal transduction. Real-time PCR confirmed a synergistic induction of several MMPs, activin A, pentraxin 3 (PTX-3), and IL-8. The in vivo findings further indicated that stimulation with IL-1 plus OSM induced protein expression of activin A, PTX-3, and KC (the murine homolog of IL-8), as compared with the changes induced by individual cytokine treatment and unstimulated controls.

CONCLUSION

The results confirm that the potent proinflammatory cytokine combination of IL-1 plus OSM synergistically and coordinately up-regulates many genes and several MMPs. Moreover, chondrocytes exhibit a potential repair response following this procatabolic stimulus such that the repair mechanisms are ultimately overwhelmed by degradative processes in the cartilage. This gene-profiling study provides insight into the complex processes that mediate joint disease in the inflammatory arthritides through the coordinated expression of multiple genes.

Effect of Betula platyphylla var. japonica on Proteoglycan Release, Type II Collagen Degradation, and Matrix Metalloproteinase Expression in Rabbit Articular Cartilage Explants

Articular cartilage is a potential target for drugs designed to inhibit the activity of matrix metalloproteinases (MMPs) to stop or slow the destruction of proteoglycan and collagen in the cartilage extracellular matrix. The purpose of this study was to investigate the effects of Betula platyphylla var. japonica on inhibiting the release of glycosaminoglycan (GAG), the degradation of collagen, and MMP expression and activity in rabbit articular cartilage explants. Interleukin-1alpha (IL-1alpha) rapidly induced GAG, but collagen was much less readily released from cartilage explants. Betula platyphylla var. japonica significantly inhibited GAG and collagen release in a concentration-dependent manner. Betula platyphylla var. japonica dose-dependently inhibited MMP-3 and MMP-13 expression and activities from IL-1alpha-treated cartilage explant culture when tested at concentrations ranging from 0.02 to 0.2 mg/ml. Betula platyphylla var. japonica had no harmful effect on chondrocyte viability or cartilage morphology in cartilage explants. Histological analysis indicated that Betula platyphylla var. japonica reduced the degradation of the cartilage matrix compared with that of IL-1alpha-treated cartilage explants. These results indicate that Betula platyphylla var. japonica inhibits the degradation of proteoglycan and collagen through the down regulation of MMP-3 and MMP-13 expression and activities without affecting the viability or morphology of IL-1alpha-stimulated rabbit articular cartilage explants.

The role of IL-1 and IL-1Ra in joint inflammation and cartilage degradation

Interleukin (IL)-1 is a cytokine that plays a major role in inflammatory responses in the context of infections and immune-mediated diseases. IL-1 refers to two different cytokines, termed IL-1alpha and IL-1beta, produced from two genes. IL-1alpha and IL-1beta are produced by different cell types following stimulation by bacterial products, cytokines, and immune complexes. Monocytes/macrophages are the primary source of IL-1beta. Both cytokines do not possess leader peptide sequences and do not follow a classical secretory pathway. IL-1alpha is mainly cell associated, whereas IL-1beta can be released from activated cells after cleavage of its amino-terminal region by caspase-1. IL-1 is present in the synovial tissue and fluids of patients with rheumatoid arthritis. Several in vitro studies have shown that IL-1 stimulates the production of mediators such as prostaglandin E(2), nitric oxide, cytokines, chemokines, and adhesion molecules that are involved in articular inflammation. Furthermore, IL-1 stimulates the synthesis and activity of matrix metalloproteinases and other enzymes involved in cartilage destruction in rheumatoid arthritis and osteoarthritis. The effects of IL-1 are inhibited in vitro and in vivo by natural inhibitors such as IL-1 receptor antagonist and soluble receptors. IL-1 receptor antagonist belongs to the IL-1 family of cytokines and binds to IL-1 receptors but does not induce any intracellular response. IL-1 receptor antagonist inhibits the effect of IL-1 by blocking its interaction with cell surface receptors. The use of IL-1 inhibitors in experimental models of inflammatory arthritis and osteoarthritis has provided a strong support for the role of IL-1 in the pathogeny of these diseases. Most importantly, these findings have been confirmed in clinical trials in patients with rheumatic diseases. Additional strategies aimed to block the effect of IL-1 are tested in clinical trials.

Effect of Aralia cordata Extracts on Cartilage Protection and Apoptosis Inhibition

Cartilage loss in osteoarthritis is characterized by cartilage degradation and chondrocyte death. Cartilage degradation is induced by activation of matrix-metalloproteinases (MMPs) activity and degradation of glycosaminoglycan (GAG) and collagen. Also, chondrocyte death is induced by the apoptosis through the activation of MAP kinase and caspases activities. On the basis of this background, our study was designed to examine the cartilage protective and anti-apoptotic effect of Aralia cordata. Cartilage explants and Chondrocytes were cultured from rabbit knee joint cartilage and treated by 5 ng/ml IL-1alpha. Cartilage and chondroprotective effects of Aralia cordata were determined by measuring (1) GAG and collagen expression, (2) GAG and collagen degradation, (3) TIMP and MMPs expression, and (4) TIMP and MMPs activity. Anti-apoptotic effects of Aralia cordata were determined by measuring (1) JNK and p38 MAP kinase expression, (2) apoptotic cells by flow cytometry, and (3) caspase-3 activity. In cartilage explants and chondroctyes treated by IL-1alpha, Aralia cordata showed the decrease of GAG and collagen degradation, decrease of MMPs (MMP-1, -3, -13) activity, and increase of TIMP-1 activity in a dose-dependent manner. Aralia cordata also showed anti-apoptotic effect by inhibition of early and late apoptotic cells, sub-G1 phase cells, and caspase-3 activity through the downregulation of JNK and p38 MAP kinase signaling pathway. Aralia cordata inhibited the cartilage and chondrocyte destruction through the downregulation of MMPs activities and the inhibition of proteoglycan and collagen degradation. Also, Aralia cordata inhibited the chondrocyte apoptosis through the downregulation of JNK and p38 MAP kinase signal, and the inhibition of caspase-3 activity.

The effect of IL-1beta on the expression of matrix metalloproteinases and tissue inhibitors of matrix metalloproteinases in human chondrocytes

Interleukin-1 (IL-1) plays key roles in altering cartilage matrix turnover. This turnover is regulated by matrix metalloproteinases (MMPs) and tissue inhibitors of matrix metalloproteinases (TIMPs). In the present study, we examined the effect of IL-1beta on cell proliferation, alkaline phosphatase (ALPase) activity, and the expression of MMPs, and TIMPs in chondrocytes derived from normal human femoral cartilage. The cells were cultured in Dulbecco's modified Eagle's medium containing 15% fetal bovine serum and 0, 1, 10, or 100 U/ml of IL-1beta for up to 28 days. The level of expression of MMPs and TIMPs was estimated by determining mRNA levels using real-time PCR and by determining protein levels using an enzyme-linked immunosorbent assay. Cell proliferation decreased in the presence of IL-1beta after day 21 of culture. ALPase activity decreased significantly in the presence of IL-1beta after day 10 of culture. The expression of MMP-1, -2, and -3 increased markedly in the presence of IL-1beta after day 21 of culture. MMP-13 expression increased markedly in the presence of IL-1beta on day 1 of culture, but decreased markedly after day 7. The expression of TIMP-1 increased significantly after day 14 of culture. The expression of TIMP-2 decreased significantly on day 1, but increased significantly from day 3 to day 14 of culture. These results suggest that IL-1beta may stimulate cartilage matrix turnover by increasing mainly MMP-13 production by the cells.

Oncostatin M in combination with tumor necrosis factor ? induces cartilage damage and matrix metalloproteinase expression in vitro and in vivo

OBJECTIVE

To determine the effects of the proinflammatory cytokine combination of oncostatin M (OSM) and tumor necrosis factor alpha (TNFalpha) on cartilage destruction in both in vitro and in vivo model systems.

METHODS

The release of collagen and proteoglycan was assessed in bovine cartilage explant cultures, while messenger RNA (mRNA) from bovine chondrocytes was analyzed by Northern blotting. Immunohistochemistry was performed on sections prepared from murine joints following injection of adenovirus vectors encoding murine OSM and/or murine TNFalpha.

RESULTS

The combination of OSM + TNFalpha induced significant collagen release from bovine cartilage, accompanied by high levels of active collagenolytic activity. Northern blot analysis indicated that this cytokine combination synergistically induced matrix metalloproteinase 1 (MMP-1), MMP-3, and MMP-13 mRNA. The in vivo data clearly indicated that OSM + TNFalpha overexpression increased MMP levels and decreased levels of tissue inhibitor of metalloproteinases 1 (TIMP-1). Specifically, OSM + TNFalpha induced marked synovial hyperplasia, inflammation, and cartilage and bone destruction with a concomitant increase in MMP expression in both cartilage and synovium and decreased TIMP-1 expression in the articular cartilage. These effects were markedly greater than those seen with either cytokine alone.

CONCLUSION

This study demonstrates that OSM + TNFalpha represents a potent proinflammatory cytokine combination that markedly induces MMP production in both cartilage and synovium, thus promoting joint destruction.

Adenoviral gene transfer of interleukin-1 in combination with oncostatin M induces significant joint damage in a murine model

Oncostatin M (OSM) is an interleukin (IL)-6 family cytokine that we have previously shown can synergize with a number of proinflammatory cytokines to promote the release of collagen from cartilage in explant culture. However, the effects of this potent cytokine combination in vivo are not known. Using adenoviral gene transfer, we have overexpressed murine IL-1 (AdmIL-1) and murine OSM (AdmOSM) intraarticularly in the knees of C57BL/6 mice. Histological analyses indicated marked synovial hyperplasia and inflammatory cell infiltration for both AdmIL-1 and AdmOSM but not in control joints. This inflammation was even more pronounced for the AdmIL-1+AdmOSM combination with evidence of cartilage and bone destruction. Significant loss of both proteoglycan and collagen was also seen for this combination, and immunohistochemistry revealed an increased expression of matrix metalloproteinases (MMPs) with decreased tissue inhibitor of metalloproteinases (TIMPs) in both articular cartilage and synovium. Similar expression profiles for MMPs/TIMPs were found in IL-1+OSM-stimulated human articular chondrocytes. Taken together, these data confirm that, in vivo, OSM can exacerbate the effects of IL-1 resulting in inflammation and tissue destruction characteristic of that seen in rheumatoid arthritis. We provide further evidence to implicate the up-regulation of MMPs as a key factor in joint pathology.

Local overexpression of adeno-viral IL-4 protects cartilage from metallo proteinase-induced destruction during immune complex-mediated arthritis by preventing activation of pro-MMPs

OBJECTIVE

To determine whether IL-4 protects against metalloproteinase-induced cartilage destruction during immune complex mediated arthritis and to elucidate its mechanism.

METHODS

Experimental immune complex arthritis (ICA) was raised by injecting lysozyme into the knee joints of mice which previously were given anti-lysozyme antibodies. Three days before ICA induction, mice were injected into the right knee joint with either IL-4 expressing or empty control recombinant human type 5 adenovirus. Joint inflammation and cartilage destruction (PG depletion, erosion) was measured by histology of total knee joints. Aggrecan breakdown in cartilage caused by metalloproteinases (MMPs) was studied by immunolocalization using anti-VDIPEN antibodies.

RESULTS

Four days after ICA induction, histological analysis showed comparable exudate and infiltrate in both groups. Depletion of proteoglycans as measured by loss of red staining was also comparable in both groups. IL-4 treatment inhibited MMP-mediated neoepitope expression by 90%. Moreover, cartilage matrix erosion was evident in all animals (10 out of 10 mice) in the control group and significantly diminished (only two out of ten mice) in the IL-4 treated group. Incubation of patellae with APMA, which activates latent MMPs resulted in VDIPEN expression which was not significantly different from control ICA indicating that comparable amounts of latent pro-MMPs are present in IL-4 treated arthritic knee joints.

CONCLUSION

This study indicates that during ICA, IL-4 largely prevents MMP-mediated aggrecan breakdown and severe cartilage erosion. IL-4 does not inhibit production of latent MMPs by the chondrocyte but predominantly interferes with its activation.

Modulation of the expression of matrix metalloproteinase and tissue inhibitors of metalloproteinases by TGF-beta1 and IGF-1 in primary human articular and bovine nasal chondrocytes stimulated with TNF-alpha

Tumour necrosis factor-alpha (TNF-alpha) was able to promote collagen breakdown from bovine cartilage in explant culture. This release was dependent upon matrix metalloproteinases (MMPs) and could be prevented by transforming growth factor-beta1 (TGF-beta1) or insulin-like growth factor-1. Both growth factors reduced the expression and secretion of collagenase enzymes, and TGF-beta1 induced tissue inhibitor of metalloproteinase production. This study shows for the first time that these anabolic growth factors can protect cartilage against TNF-alpha-induced destruction.