Targeting Aggrecanases for Osteoarthritis Therapy: From Zinc Chelation to Exosite Inhibition

Osteoarthritis (OA) is the most common degenerative joint disease. In 1999, two members of the A Disintegrin and Metalloproteinase with Thrombospondin Motifs (ADAMTS) family of metalloproteinases, ADAMTS4 and ADAMTS5, or aggrecanases, were identified as the enzymes responsible for aggrecan degradation in cartilage. The first aggrecanase inhibitors targeted the active site by chelation of the catalytic zinc ion. Due to the generally disappointing performance of zinc-chelating inhibitors in preclinical and clinical studies, inhibition strategies tried to move away from the active-site zinc in order to improve selectivity. Exosite inhibitors bind to proteoglycan-binding residues present on the aggrecanase ancillary domains (called exosites). While exosite inhibitors are generally more selective than zinc-chelating inhibitors, they are still far from fulfilling their potential, partly due to a lack of structural and functional data on aggrecanase exosites. Filling this gap will inform the design of novel potent, selective aggrecanase inhibitors.

Expression and Preparation of Recombinant Reelin and ADAMTS-3 Proteins

Reelin is a large secreted protein that is essential for the brain development and function. Reelin is negatively regulated by the specific cleavage by a disintegrin and metalloproteinase with thrombospondin type 1 motifs 3 (ADAMTS-3) which is also secreted from neurons. It is likely that there are other proteases that can cleave Reelin. This chapter describes the protocol for expression and handling of recombinant Reelin and ADAMTS-3 proteins to facilitate investigation of these proteins.

SP1-mediated downregulation of ADAMTS3 gene expression in osteosarcoma models

ADAMTS3 is a member of procollagen N-proteinase subfamily of ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs) gene family. It has an important function in the procollagen maturation process. The removal of N-peptidases is required for the accurate processing of fibrillar collagens. Otherwise, several disorders can occur that is related with the collagenous tissues. ADAMTS3 mainly maturates type II collagen molecule which is the main component of the bone and cartilage. There are several expression studies about ADAMTS3 gene however its transcriptional regulation has not been lightened up, yet. Here we first time cloned and functionally analyzed the promoter region of ADAMTS3 gene, approximately 1380 bp upstream of the transcription start site. Transient transfection experiments showed that all truncated promoter constructs are active and 171 bp fragment is sufficient to activate gene expression in both Saos-2 and MG63 cells. In silico analysis showed that ADAMTS3 has a TATA-less promoter and contains several SP1/GC box binding motifs and a CpG island. Therefore we mainly investigated the SP1 dependent regulation of ADAMTS3 promoter. SP1 downregulated ADAMTS3 transcriptional activity. As consistent with the transcriptional activity, mRNA, and protein expression levels were also decreased by SP1. On the other hand, functional binding of the SP1 on multiple regions of ADAMTS3 promoter was confirmed by EMSA studies. As ADAMTS3 is responsible for the collagen maturation and biosynthesis, further we investigated the effect of SP1 on type I-II and III collagen gene expressions. We point out that SP1 increased type II and III collagen expression and in contrast decreased type I collagen expression levels in Saos-2 cells. mRNA expression level was decreased for all collagen types in MG63 model. Decrease in the type II collagen expression was also demonstrated at the protein level by SP1. Collectively these results provide first findings for the SP1-related transcriptional regulation of ADAMTS3 and collagen genes in osteosarcoma cell lines.

Intestinal fibrosis is associated with lack of response to Infliximab therapy in Crohn's disease

INTRODUCTION

Overt fibrostenotic disease is a relative contraindication for anti-TNF therapy in Crohn's disease. We hypothesized that subclinical fibrosis may also contribute to an incomplete response to anti-TNF therapy before the onset of symptomatic stenosis.

METHODS

In a previous trial, patients with ileocecal Crohn's disease were randomized to either immediate ileocecal resection or medical treatment with Infliximab. In case of insufficient response to Infliximab, the latter underwent secondary ileocecal resection. We compared specimens from those patients undergoing immediate resection (Infliximab naïve, n = 20) to those who failed Infliximab therapy (n = 20).

RESULTS

Infliximab naïve and Infliximab failure patients had similar severity of inflammation when assessed by CRP levels (median 14 vs 9 mg/L) and histology (Geboes-D'Haens-score, median 10 vs 11 points). On immunohistochemistry, collagen-III and fibronectin depositions were increased in patients previously exposed to Infliximab compared to patients naïve to Infliximab. On mRNA level, procollagen peptidase showed significantly more mucosal mRNA expression in Crohn's disease patients who failed Infliximab. Infliximab responders showed no increase of this marker after 4 weeks of successful Infliximab treatment.

DISCUSSION

Failure to Infliximab therapy is associated with subclinical fibrosis in Crohn's disease.

Expression of ADAMTS-1, -4, -5 and TIMP-3 in normal and multiple sclerosis CNS white matter

ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs) -1, -4 and -5 proteases have been identified in the CNS at the mRNA level. These glutamyl endopeptidases, inhibited by tissue inhibitor of metalloproteinases (TIMP)-3, are key enzymes in the degradation of the aggregating chondroitin sulphate proteoglycans (CSPGs), and may therefore play a role in CNS extracellular matrix (ECM) changes in multiple sclerosis (MS). We have investigated ADAMTS and TIMP-3 expression in normal and MS CNS white matter by real-time RT-PCR, western blotting and immunohistochemistry. We report for the first time the presence of ADAMTS-1, -4 and -5 in normal and MS white matter. Levels of ADAMTS-1 and -5 mRNA were decreased in MS compared to normal tissue, with no significant change in ADAMTS-4 mRNA levels. Protein levels of ADAMTS-4 were significantly higher in MS tissue compared to normal tissue. Immunohistochemical studies demonstrated that ADAMTS-4 was associated predominantly with astrocytes with increased expression within MS lesions. TIMP-3 mRNA was significantly decreased in MS compared to controls. These studies suggest a role for ADAMTS-4 in the pathogenesis of MS. Further studies on the activity of ADAMTS-4 will enable a better understanding of its role in the turnover of the ECM of white matter in MS.

Proteolytic activation defines distinct lymphangiogenic mechanisms for VEGFC and VEGFD

Lymphangiogenesis is supported by 2 homologous VEGFR3 ligands, VEGFC and VEGFD. VEGFC is required for lymphatic development, while VEGFD is not. VEGFC and VEGFD are proteolytically cleaved after cell secretion in vitro, and recent studies have implicated the protease a disintegrin and metalloproteinase with thrombospondin motifs 3 (ADAMTS3) and the secreted factor collagen and calcium binding EGF domains 1 (CCBE1) in this process. It is not well understood how ligand proteolysis is controlled at the molecular level or how this process regulates lymphangiogenesis, because these complex molecular interactions have been difficult to follow ex vivo and test in vivo. Here, we have developed and used biochemical and cellular tools to demonstrate that an ADAMTS3-CCBE1 complex can form independently of VEGFR3 and is required to convert VEGFC, but not VEGFD, into an active ligand. Consistent with these ex vivo findings, mouse genetic studies revealed that ADAMTS3 is required for lymphatic development in a manner that is identical to the requirement of VEGFC and CCBE1 for lymphatic development. Moreover, CCBE1 was required for in vivo lymphangiogenesis stimulated by VEGFC but not VEGFD. Together, these studies reveal that lymphangiogenesis is regulated by two distinct proteolytic mechanisms of ligand activation: one in which VEGFC activation by ADAMTS3 and CCBE1 spatially and temporally patterns developing lymphatics, and one in which VEGFD activation by a distinct proteolytic mechanism may be stimulated during inflammatory lymphatic growth.

[Preparation of rabbit polyclonal antibody against mouse ADAMTS2]

OBJECTIVE

To obtain recombinant mouse collagenase ADAMTS2 (ADAM metallopeptidase with thrombospondin type 1 motif, 2) C terminal (1109-1213), and prepare the corresponding rabbit anti-ADAMTS2 polyclonal antibodies.

METHODS

The recombinant expression plasmid pGEX-6p-1-ADAMTS2 (1109-1213) was transformed into E.coli. The target protein was induced by IPTG and identified by mass spectrometry following affinity purification. The expressed and purified ADAMTS2 (1109-1213) protein was used to immunize New Zealand rabbits to prepare anti-ADAMTS2 polyclonal antibodies. The antibody titers were detected by ELISA and the antibody specificity by Western blotting.

RESULTS

The protein ADAMTS2 (1109-1213) was expressed in E.coli after IPTG induction, and with the purified protein, we prepared antiserum in the immunized rabbits. The titer of the antiserum reached over 1:160 000. The antiserum showed a good specificity.

CONCLUSION

The high titer and specific rabbit anti-ADAMTS2 antibody has been prepared successfully.

Ephrin-A5 Is Required for Optimal Fertility and a Complete Ovulatory Response to Gonadotropins in the Female Mouse

Follicle growth and ovulation involve the coordinated expression of many genes, driven by FSH and LH. Reports indicate that Eph receptors and ephrins are expressed in the ovary, suggesting roles in follicle growth and/or ovulation. We previously reported FSH-induced expression of ephrin-A5 (EFNA5) and 4 of its cognate Eph receptors in mouse granulosa cells. We now report that female mice lacking EFNA5 are subfertile, exhibit a compromised response to LH, and display abnormal ovarian histology after superovulation. Efna5(-/-) females litters were 40% smaller than controls, although no difference in litter frequency was detected. The ovarian response to superovulation was also compromised in Efna5(-/-) females, with 37% fewer oocytes ovulated than controls. These results corresponded with a reduction in ovarian mRNA levels of several LH-responsive genes, including Pgr, Ptgs2, Tnfaip6, Ereg, Btc, and Adamts4, suggesting that Efna5(-/-) ovaries exhibit a partially attenuated response to LH. Histopathological analysis indicated that superovulated Efna5(-/-) females exhibited numerous ovarian defects, including intraovarian release of cumulus oocyte complexes, increased incidence of oocytes trapped within luteinized follicles, granulosa cell and follicular fluid emboli, fibrin thrombi, and interstitial hemorrhage. In addition, adult Efna5(-/-) ovaries exhibited a 4-fold increase in multioocyte follicles compared with controls, although no difference was detected in 3-week-old mice, suggesting the possibility of follicle merging. Our observations indicate that loss of EFNA5 in female mice results in subfertility and imply that Eph-ephrin signaling may also play a previously unidentified role in the regulation of fertility in women.

MiR-29a and MiR-140 Protect Chondrocytes against the Anti-Proliferation and Cell Matrix Signaling Changes by IL-1β

As a degenerative joint disease, osteoarthritis (OA) constitutes a major cause of disability that seriously affects the quality of life of a large population of people worldwide. However, effective treatment that can successfully reverse OA progression is lacking until now. The present study aimed to determine whether two small non-coding RNAs miR-29a and miR-140, which are significantly down-regulated in OA, can be applied together as potential therapeutic targets for OA treatment. MiRNA synergy score was used to screen the miRNA pairs that potentially synergistically regulate OA. An in vitro model of OA was established by treating murine chondrocytes with IL-1β. Transfection of miR-29a and miR-140 via plasmids was investigated on chondrocyte proliferation and expression of nine genes such as ADAMTS4, ADAMTS5, ACAN, COL2A1, COL10A1, MMP1, MMP3, MMP13 and TIMP metal-lopeptidase inhibitor 1 (TIMP1). Western blotting was used to determine the protein expression level of MMP13 and TIMP1, and ELISA was used to detect the content of type II collagen. Combined use of miR-29a and miR-140 successfully reversed the destructive effect of IL-1β on chondrocyte proliferation, and notably affected the MMP13 and TIMP1 gene expression that regulates extracellular matrix. Although co-transfection of miR-29a and miR-140 did not show a synergistic effect on MMP13 protein expression and type II collagen release, but both of them can significantly suppress the protein abundance of MMP13 and restore the type II collagen release in IL-1β treated chondrocytes. Compared with single miRNA transfection, cotransfection of both miRNAs exceedingly abrogated the suppressed the protein production of TIMP1 caused by IL-1β, thereby suggesting potent synergistic action. These results provided novel insights into the important function of miRNAs' collaboration in OA pathological development. The reduced MMP13, and enhanced TIMP1 protein production and type II collagen release also implies that miR-29a and miR-140 combination treatment may be a possible treatment for OA.

tPA promotes ADAMTS-4-induced CSPG degradation, thereby enhancing neuroplasticity following spinal cord injury

Although tissue plasminogen activator (tPA) is known to promote neuronal remodeling in the CNS, no mechanism of how this plastic function takes place has been reported so far. We provide here in vitro and in vivo demonstrations that this serine protease neutralizes inhibitory chondroitin sulfate proteoglycans (CSPGs) by promoting their degradation via the direct activation of endogenous type 4 disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS-4). Accordingly, in a model of compression-induced spinal cord injury (SCI) in rats, we found that administration of either tPA or its downstream effector ADAMTS-4 restores the tPA-dependent activity lost after the SCI and thereby, reduces content of CSPGs in the spinal cord, a cascade of events leading to an improved axonal regeneration/sprouting and eventually long term functional recovery. This is the first study to reveal a tPA-ADAMTS-4 axis and its function in the CNS. It also raises the prospect of exploiting such cooperation as a therapeutic tool for enhancing recovery after acute CNS injuries.

Biochemical and structural characterization of neocartilage formed by mesenchymal stem cells in alginate hydrogels

A popular approach to make neocartilage in vitro is to immobilize cells with chondrogenic potential in hydrogels. However, functional cartilage cannot be obtained by control of cells only, as function of cartilage is largely dictated by architecture of extracellular matrix (ECM). Therefore, characterization of the cells, coupled with structural and biochemical characterization of ECM, is essential in understanding neocartilage assembly to create functional implants in vitro. We focused on mesenchymal stem cells (MSC) immobilized in alginate hydrogels, and used immunohistochemistry (IHC) and gene expression analysis combined with advanced microscopy techniques to describe properties of cells and distribution and organization of the forming ECM. In particular, we used second harmonic generation (SHG) microscopy and focused ion beam/scanning electron microscopy (FIB/SEM) to study distribution and assembly of collagen. Samples with low cell seeding density (1e7 MSC/ml) showed type II collagen molecules distributed evenly through the hydrogel. However, SHG microscopy clearly indicated only pericellular localization of assembled fibrils. Their distribution was improved in hydrogels seeded with 5e7 MSC/ml. In those samples, FIB/SEM with nm resolution was used to visualize distribution of collagen fibrils in a three dimensional network extending from the pericellular region into the ECM. In addition, distribution of enzymes involved in procollagen processing were investigated in the alginate hydrogel by IHC. It was discovered that, at high cell seeding density, procollagen processing and fibril assembly was also occurring far away from the cell surface, indicating sufficient transport of procollagen and enzymes in the intercellular space. At lower cell seeding density, the concentration of enzymes involved in procollagen processing was presumably too low. FIB/SEM and SHG microscopy combined with IHC localization of specific proteins were shown to provide meaningful insight into ECM assembly of neocartilage, which will lead to better understanding of cartilage formation and development of new tissue engineering strategies.

Current and emerging therapeutic strategies for preventing inflammation and aggrecanase-mediated cartilage destruction in arthritis

Arthritis is a multifactorial disease for which current therapeutic intervention with high efficacy remains challenging. Arthritis predominately affects articular joints, and cartilage deterioration and inflammation are key characteristics. Current therapeutics targeting inflammatory responses often cause severe side effects in patients because of the systemic inhibition of cytokines or other global immunosuppressive activities. Furthermore, a lack of primary response or failure to sustain a response to treatment through acquired drug resistance is an ongoing concern. Nevertheless, treatments such as disease-modifying anti-rheumatic drugs, biological agents, and corticosteroids have revealed promising outcomes by decreasing pain and inflammation in patients and in some cases reducing radiographic progression of the disease. Emerging and anecdotal therapeutics with anti-inflammatory activity, alongside specific inhibitors of the A Disintegrin-like And Metalloproteinase domain with Thrombospondin-1 repeats (ADAMTS) cartilage-degrading aggrecanases, provide promising additions to current arthritis treatment strategies. Thus, it is paramount that treatment strategies be optimized to increase efficacy, reduce debilitating side effects, and improve the quality of life of patients with arthritis. Here, we review the current strategies that attempt to slow or halt the progression of osteoarthritis and rheumatoid arthritis, providing an up-to-date summary of pharmaceutical treatment strategies and side effects. Importantly, we highlight their potential to indirectly regulate ADAMTS aggrecanase activity through their targeting of inflammatory mediators, thus providing insight into a mechanism by which they might inhibit cartilage destruction to slow or halt radiographic progression of the disease. We also contrast these with anecdotal or experimental administration of statins that could equally regulate ADAMTS aggrecanase activity and are available to arthritis sufferers worldwide. Finally, we review the current literature regarding the development of synthetic inhibitors directed toward the aggrecanases ADAMTS4 and ADAMTS5, a strategy that might directly inhibit cartilage destruction and restore joint function in both rheumatoid arthritis and osteoarthritis.

A combinatorial relative mass value evaluation of endogenous bioactive proteins in three-dimensional cultured nucleus pulposus cells of herniated intervertebral discs: identification of potential target proteins for gene therapeutic approaches

Painful degenerative disc diseases have been targeted by different biological treatment approaches. Nucleus pulposus (NP) cells play a central role in intervertebral disc (IVD) maintenance by orchestrating catabolic, anabolic and inflammatory factors that affect the extracellular matrix. IVD degeneration is associated with imbalances of these factors, resulting in a catabolic inflammatory metabolism. Therefore, accurate knowledge about their quantity and quality with regard to matrix synthesis is vital for a rational gene therapeutic approach. NP cells were isolated from 63 patients operated due to lumbar disc herniation (mean age 56 / range 29 - 84 years). Then, three-dimensional culture with low-glucose was completed in a collagen type I scaffold for four weeks. Subsequently cell proliferation evaluation was performed using 3-(4, 5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide and intracellular concentration of 28 endogenously expressed anabolic, catabolic, inflammatory factors and relevant matrix proteins was determined by enzyme-linked immunosorbent assay. Specimen-related grades of degeneration were confirmed by preoperative magnetic resonance imaging. Independent from gender, age and grade of degeneration proliferation rates remained similar in all groups of NP cells. Progressive grades of degeneration, however, showed a significant influence on accumulation of selective groups of factors such as disintegrin and metalloproteinase with thrombospondin motifs 4 and 5, matrix metalloproteinase 3, metalloproteinase inhibitor 1 and 2, interleukin-1β and interleukin-1 receptor. Along with these changes, the key NP matrix proteins aggrecan and collagen II decreased significantly. The concentration of anabolic factors bone morphogenetic proteins 2, 4, 6 and 7, insulin-like growth factor 1, transforming growth factor beta 1 and 3, however, remained below the minimal detectable quantities. These findings indicate that progressive degenerative changes in NP may be problematic with regard to biologic treatment strategies. Hence, gene therapeutic interventions regulating relevant bioactive factors identified in this work might contribute to the development of regenerative treatment approaches for degenerative disc diseases.

[Research progress of a disintegrin and metalloproteinase with thrombospondin motif 4 and 5 in osteoarthritis]

OBJECTIVE

To review the progress of a disintegrin and metalloproteinase with thrombospondin motif 4 (ADAMTS-4) and ADAMTS-5 in osteoarthritis.

METHODS

Recent literature about the ADAMTS-4 and -5 in osteoarthritis was analyzed; the structure, function, inhibitors of the ADAMTS-4 and -5, and the relationship between the proteases and osteoarthritis were analyzed and summarized.

RESULTS

ADAMTS-4 and -5 can reduce chondrocyte and extracellular matrix by degrading aggrecan and cartilage oligomeric matrix protein, which induced the pathogenesis of osteoarthritis.

CONCLUSION

ADAMTS-4 and -5 have been demonstrated to play important roles in osteoarthritis. It can better guide treatment and prevention of osteoarthritis to further study related mechanism of ADAMTS-4 and -5, and to promote the establishment of a clinical drug targets.

Detection of ADAMTS-4 activity using a fluorogenic peptide-conjugated Au nanoparticle probe in human knee synovial fluid

A disintegrin and metalloproteinase with thrombospondin motif-4 (ADAMTS-4) plays a pivotal role in degrading aggrecan, which is an early event in cartilage degrading joint diseases such as osteoarthritis (OA). Detection of ADAMTS-4 activity could provide useful clinical information for early diagnosis of such diseases and disease-modifying therapy. Therefore, we developed a ADAMTS-4 detective fluorescent turn-on AuNP probe (ADAMTS-4-D-Au probe) by conjugating gold nanoparticles with a FITC-modified ADAMTS-4-specific peptide (DVQEFRGVTAVIR). When the ADAMTS-4-D-Au probe was incubated with ADAMTS-4, the fluorescence recovered and fluorescence intensity markedly increased in proportion to concentrations of ADAMTS-4 and the probe. A nearly 3-fold increase in fluorescent intensity in response to only 3.9 pM of ADAMTS-4 was detected, whereas almost no fluorescence recovery was observed when the probe was incubated with matrix metalloproteinase (MMP)-1, -3, and -13. These results indicate a relative high sensitivity and specificity of the probe. Moreover, ADAMTS-4-D-Au probe was used to detect ADAMTS-4 activity in synovial fluid from 11 knee surgery patients. A substantial increase in fluorescent intensity was observed in the acute joint injury group as compared to the chronic joint injury and end-stage OA groups, indicating that this simple and low-cost sensing system might serve as a new detection method for ADAMTS-4 activity in biological samples and in screens for inhibitors for ADAMTS-4-related joint diseases. Additionally, this probe could be a potential biomarker for early diagnosis of cartilage-degrading joint diseases.

The low binding affinity of ADAMTS4 for citrullinated fibronectin may contribute to the destruction of joint cartilage in rheumatoid arthritis

OBJECTIVES

Rapid cartilage degradation in the joints is observed in rheumatoid arthritis (RA). ADAMTS4 (a disintegrin and metalloproteinase with thrombospondin motifs-4) degrades aggrecan, the primary component of cartilage, therefore contributing to joint erosion in RA. The proteolytic activity of ADAMTS4 is inhibited by fibronectin (FN). FN is abundantly expressed in the synovia in RA and is modified by citrullination, the conversion of peptidylarginine to citrulline. This study aims to investigate the binding ability of citrullinated FN (cFN) to ADAMTS4 and the effect of cFN on aggrecanase activity.

METHODS

The full-length recombinant ADAMTS4 was purified from HEK293 cells that were transiently transfected with a full-length cDNA coding for human ADAMTS4. A 40-kDa FN fragment exhibiting heparin binding was citrullinised with rabbit peptidylarginine deaminase. The binding activity of the full-length recombinant ADAMTS4 to cFN was investigated in an in vitro binding assay. The proteolytic activity of ADAMTS4 after incubation with cFN was determined using an aggrecanase activity kit, in which the ARGSVIL peptide is produced by digestion with aggrecanase.

RESULTS

cFN displayed significantly decreased binding activity with ADAMTS4 compared with FN. The full-length ADAMTS4 produced large amounts of the ARGSVIL peptide, but the amount was markedly decreased in the presence of FN. The production of this peptide approached the normal level when the full-length ADAMTS4 was incubated with cFN.

CONCLUSIONS

FN following citrullination is less effective in inhibiting the proteolytic activity of ADAMTS4. It is known that PADI4, an enzyme active in citrullination, is highly expressed in the synovial tissue in RA. Our results suggest that PADI4 in the RA synovium may contribute to cartilage destruction via the citrullination of FN.

Arylsulfonamide inhibitors of aggrecanases as potential therapeutic agents for osteoarthritis: synthesis and biological evaluation

Aggrecanases, in particular aggrecanase-2 (ADAMTS-5), are considered the principal proteases responsible for aggrecan degradation in osteoarthritis. For this reason, considerable effort has been put on the discovery and development of aggrecanase inhibitors able to slow down or halt the progression of osteoarthritis. We report herein the synthesis and biological evaluation of a series of arylsulfonamido-based hydroxamates as aggrecanase inhibitors. Compound 18 was found to have a nanomolar activity for ADAMTS-5, ADAMTS-4 and MMP-13 and high selectivity over MMP-1 and MMP-14. Furthermore, this compound proved to be effective in blocking ex vivo cartilage degradation without having effect on cell cytotoxicity.

Regulated proteolytic processing of Reelin through interplay of tissue plasminogen activator (tPA), ADAMTS-4, ADAMTS-5, and their modulators

The extracellular signaling protein Reelin, indispensable for proper neuronal migration and cortical layering during development, is also expressed in the adult brain where it modulates synaptic functions. It has been shown that proteolytic processing of Reelin decreases its signaling activity and promotes Reelin aggregation in vitro, and that proteolytic processing is affected in various neurological disorders, including Alzheimer's disease (AD). However, neither the pathophysiological significance of dysregulated Reelin cleavage, nor the involved proteases and their modulators are known. Here we identified the serine protease tissue plasminogen activator (tPA) and two matrix metalloproteinases, ADAMTS-4 and ADAMTS-5, as Reelin cleaving enzymes. Moreover, we assessed the influence of several endogenous protease inhibitors, including tissue inhibitors of metalloproteinases (TIMPs), α-2-Macroglobulin, and multiple serpins, as well as matrix metalloproteinase 9 (MMP-9) on Reelin cleavage, and described their complex interplay in the regulation of this process. Finally, we could demonstrate that in the murine hippocampus, the expression levels and localization of Reelin proteases largely overlap with that of Reelin. While this pattern remained stable during normal aging, changes in their protein levels coincided with accelerated Reelin aggregation in a mouse model of AD.

WIN-34B, a new herbal medicine, inhibits the inflammatory response by inactivating IκB-α phosphorylation and mitogen activated protein kinase pathways in fibroblast-like synoviocytes

ETHNOPHARMACOLOGICAL RELEVANCE

The dried flowers of Lonicera japonica Thunb and dried roots of Anemarrhena asphodeloides BUNGE have been used for the treatment of a variety of inflammatory diseases in traditional Korean medicine.

OBJECTIVE

The aim of the study is to evaluate the anti-inflammatory effects of WIN-34B, a new herbal medicine, in fibroblast-like synoviocytes (FLS) obtained from patients with osteoarthritis (OA).

MATERIALS AND METHODS

WIN-34B is isolated from the n-butanol fraction of dried flowers of L. japonica and dried roots of A. asphodeloides. The anti-inflammatory effects of WIN-34B on cell viability, the production and release of inflammatory mediators, matrix metalloproteinases (MMPs), aggrecanases, tissue inhibitor of matrix proteinases (TIMP) is compared with celecoxib in IL-1β-stimulated human OA FLS. Furthermore, the effect of WIN-34B on inhibitory kappa B-α (IκB-α) phosphorylation and mitogen-activated protein kinases (MAPK) in the IL-1β-stimulated OA FLS was also evaluated.

RESULTS

WIN-34B significantly inhibited the IL-1β-induced cell viability in human OA FLS without cytotoxicity. Compared to celecoxib, WIN-34B exhibited similar or better anti-inflammatory effects through significant suppression of inflammatory mediators (IL-1β, TNF-α, PGE2 and NO), MMPs (MMP-1, MMP-3 and MMP-13) and aggrecanases (ADAMTS-4 and ADAMTS-5), and enhancement of TIMPs (TIMP-1 and TIMP-3). Moreover, WIN-34B reduced the phosphorylation of IκB-α, ERK1/2, p38 and JNK1/2 in IL-1β-stimulated OA FLS.

CONCLUSIONS

WIN-34B exhibited similar or better anti-inflammatory properties in IL-1β-stimulated OA FLS compared to celecoxib. The anti-inflammatory effects of WIN-34B are due to inhibition of inflammatory mediators (IL-1β, TNF-α, PGE2 and NO) and regulation of MMPs, ADAMTSs and TIMPs via the inhibition of IκB-α and MAPK phosphorylation in IL-1β-stimulated OA FLS.

MMP-13 regulates growth of wound granulation tissue and modulates gene expression signatures involved in inflammation, proteolysis, and cell viability

Proteinases play a pivotal role in wound healing by regulating cell-matrix interactions and availability of bioactive molecules. The role of matrix metalloproteinase-13 (MMP-13) in granulation tissue growth was studied in subcutaneously implanted viscose cellulose sponge in MMP-13 knockout (Mmp13(-/-)) and wild type (WT) mice. The tissue samples were harvested at time points day 7, 14 and 21 and subjected to histological analysis and gene expression profiling. Granulation tissue growth was significantly reduced (42%) at day 21 in Mmp13(-/-) mice. Granulation tissue in Mmp13(-/-) mice showed delayed organization of myofibroblasts, increased microvascular density at day 14, and virtual absence of large vessels at day 21. Gene expression profiling identified differentially expressed genes in Mmp13(-/-) mouse granulation tissue involved in biological functions including inflammatory response, angiogenesis, cellular movement, cellular growth and proliferation and proteolysis. Among genes linked to angiogenesis, Adamts4 and Npy were significantly upregulated in early granulation tissue in Mmp13(-/-) mice, and a set of genes involved in leukocyte motility including Il6 were systematically downregulated at day 14. The expression of Pdgfd was downregulated in Mmp13(-/-) granulation tissue in all time points. The expression of matrix metalloproteinases Mmp2, Mmp3, Mmp9 was also significantly downregulated in granulation tissue of Mmp13(-/-) mice compared to WT mice. Mmp13(-/-) mouse skin fibroblasts displayed altered cell morphology and impaired ability to contract collagen gel and decreased production of MMP-2. These results provide evidence for an important role for MMP-13 in wound healing by coordinating cellular activities important in the growth and maturation of granulation tissue, including myofibroblast function, inflammation, angiogenesis, and proteolysis.

A disintegrin and metalloproteinase with thrombospondin motifs 4 (ADAMTS-4) cleaves Reelin in an isoform-dependent manner

Reelin is a glycoprotein essential for brain development and functions. Reelin is subject to specific proteolysis at two distinct (N-t and C-t) sites, and these cleavages significantly diminish Reelin activity. The decrease of Reelin activity is detrimental for brain function, but the protease that catalyzes specific cleavage of Reelin remains elusive. Here we found that a disintegrin and metalloproteinase with thrombospondin motifs 4 (ADAMTS-4) cleaves Reelin in an isoform-specific manner. Among ADAMTS-4 isoforms, p50 cleaves the N-t site only, while p75 cleaves both sites. This is the first report identifying a protease that can specifically cleave Reelin.

Matrilin-4 is processed by ADAMTS-5 in late Golgi vesicles present in growth plate chondrocytes of defined differentiation state

The two aggrecanases ADAMTS-4 and ADAMTS-5 have been shown to not only play roles in the breakdown of cartilage extracellular matrix in osteoarthritis, but also mediate processing of matrilins in the secretory pathway. The matrilins are adaptor proteins with a function in connecting fibrillar and network-like components in the cartilage extracellular matrix. Cleavage resulting in processed matrilins with fewer ligand-binding subunits could make these less efficient in providing matrix cohesion. In this study, the processing and degradation of matrilin-4 during cartilage remodeling in the growth plate of the developing mouse long bones were studied in greater detail. We show that ADAMTS-5 and a matrilin-4 neoepitope, revealed upon ADAMTS cleavage, colocalize in prehypertrophic/hypertrophic chondrocytes while they are not detected in proliferating chondrocytes of the growth plate. ADAMTS-5 and the cleaved matrilin-4 are preferentially detected in vesicles derived from the Golgi apparatus. The matrilin-4 neoepitope was not observed in the growth plate of ADAMTS-5 deficient mice. We propose that in the growth plate ADAMTS-5, and not ADAMTS-4, has a physiological function in the intracellular processing of matrilins and potentially of other extracellular matrix proteins.

Effect of Phellodendron amurense in protecting human osteoarthritic cartilage and chondrocytes

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional medicine has been widely using Phellodendron amurense Rupr. (Rutaceae) to treat various inflammatory diseases including arthritis.

AIM OF THE STUDY

This study investigated the effects of Phellodendron amurense in protecting cartilage, including regulating the levels of aggrecanases, matrix metalloproteinases (MMPs)/tissue inhibitor of metalloproteinase (TIMP), proinflammatory cytokines and signaling of the mitogen activated protein kinase (MAPK) pathway in human osteoarticular cartilage and chondrocytes.

MATERIALS AND METHODS

Explants from human osteoarthritis cartilage were cultured alone or in IL-1α for 7 days with or without Phellodendron amurense ethanol extract or celecoxib (40, 100, 200μg/ml). The effect of Phellodendron amurense on matrix degradation induced by IL-1α in human articular cartilage was assessed by staining, and the quantities of sulfated glycosaminoglycan (GAG) and type II collagen were calculated from the culture media. The levels of aggrecanases, MMPs, TIMP, and PGE(2) in the culture media were investigated using an enzyme-linked immunosorbent assay (ELISA). In addition, reverse transcription polymerase chain reaction (RT-PCR) evaluated the mRNA expression of aggrecanases, MMPs and TIMP. Furthermore, Western blot analysis was performed to identify the roles that Phellodendron amurense played in the ERK, JNK and p38 signaling pathways.

RESULTS

Phellodendron amurense showed no evident cytotoxicity on human articular cartilage. Phellodendron amurense significantly inhibited the IL-1α-induced degradation of GAG and type II collagen from human osteoarticular cartilage in a concentration-dependent manner. Celecoxib did not significantly inhibit IL-1α-induced release of GAG and only slightly reduced type II collagen. Phellodendron amurense also dose-dependently decreased the levels of aggrecanase-1 and -2, MMP-1, -3, and -13, whereas it increased TIMP-1 expression in human osteoarticular cartilage. Celecoxib only decreased MMP-1 and MMP-13 levels in human osteoarticular cartilage. In addition, Phellodendron amurense reduced the phosphorylation of extracellular signal regulated kinase (ERK)1/2, Jun NH2-terminal kinase (JNK) and activated phospho-p38 MAPK in a dose-dependent manner in human osteoarthritic chondrocytes.

CONCLUSIONS

Phellodendron amurense inhibited osteoarticular cartilage and chondrocyte destruction by inhibiting proteoglycan release and type II collagen degradation, down-regulating aggrecanases, MMP activities and phospho-ERK1/2, JNK and p38 MAP kinase signaling, and up-regulating TIMP-1 activity. Therefore, our results suggest that Phellodendron amurense is a potential therapeutic agent to protect cartilage against OA progression.

Interleukin-1alpha treatment of meniscal explants stimulates the production and release of aggrecanase-generated, GAG-substituted aggrecan products and also the release of pre-formed, aggrecanase-generated G1 and m-calpain-generated G1-G2

Pro-inflammatory cytokines induce meniscal matrix degradation and inhibition of endogenous repair mechanisms, but the pathogenic mechanisms behind this are mostly unknown. Therefore, we investigated details of interleukin-1 (IL-1alpha)-induced aggrecan turnover in mature meniscal tissue explants. Fibro-cartilagenous disks (3 mm diameter x 1 mm thickness) were isolated from the central, weight-bearing region of menisci from 2-year-old cattle. After 3 or 6 days of IL-1alpha-treatment, GAG loss (DMMB assay), biosynthetic activity ([(35)SO(4)]-sulfate and [(3)H]-proline incorporation), gene expression (quantitative RT-PCR) and the abundance (zymography, Western blot) of matrix-degrading enzymes and specific aggrecan products were determined. Meniscal fibrocartilage had a 4-fold lower GAG content (per wet weight) than adjacent articular cartilage, and expressed MMPs-1, -2, -3 and ADAMTS4 constitutively, whereas ADAMTS5 m-RNA was essentially undetectable. Significant IL-1 effects were a decrease in biosynthetic activity, an increase in GAG release and in the expression/abundance of MMP-2, MMP-3 and ADAMTS4. Fresh tissue contained aggrecan core protein products similar to those previously described for bovine articular cartilage of this age. IL-1 induced the release of aggrecanase-generated CS-substituted products including both high (>250 kDa) and low molecular weight (about 75 kDa) species. TIMP-3 (but not TIMP-1 and -2 or a broad spectrum MMP inhibitor) inhibited IL-1-dependent GAG loss. In addition, IL-1 induced the release of preformed pools of three known G1-bearing products. We conclude that aggrecanases are responsible for IL-1-stimulated GAG release from meniscal explants, and that IL-1 also stimulates release of G1-bearing products, by a process possibly involving hyaluronan fragmentation.

[Aggrecanases and osteoarthritis]

Osteoarthritis is mainly caused by the degenerative changes of cartilage and cartilage extracellular matrix, while Aggrecanases degradate Proteoglycans which are the major components of cartilage. This review includes three aspects: (1) We have concluded the major enzymes(ADAMTS-4 and ADAMTS-5) which regulate the metabolism of cartilage extracellular matrix. Meanwhile, we have summarized the structure of aggrecanases(ADAMTS-4 and ADAMTS-5) and introduced the function of each regional structure; (2) We have concluded the way cytokines and glycosaminoglycans regulate the metabolism of aggrecanases, and discussed the regulation and control principle of cytokines and glycosaminoglycan; (3) We have summarized the majority of inhibitors to the aggrecanases, introduced the endogenic inhibitors, and put our emphasis on the extrinsic inhibitors (chelating agents, polypeptides and so on). Through deeper research on the enzymes, it will help us further understand the pathogenesis of osteoarthritis, and open up new avenues to clinical treatment.

[Effects of RNA interference against aggrecanase 1 gene on extracellular matrix metabolism of cultured chondrocytes in vitro]

OBJECTIVE

To study the effect of RNA interference (RNAi)-mediated aggrecanase-1 gene silencing on extracellular matrix metabolism of cultured rat costochondral chondrocytes.

METHODS

Rat costochondral chondrocyte monolayers were obtained by microdissection and digestion. The growth and morphological changes of the chondrocytes were observed after RNAi of aggrecanase-1 gene. The mRNA expression of aggrecanase-1 was detected by RT-PCR method, and aggrecan content was determined by Western blotting.

RESULTS

The specific inhibition of aggrecanase-1 by RNAi produced no adverse effect on the morphology and growth of the chondrocytes. The mRNA of aggrecanase-1 decreased and aggrecan content increased significantly after transfection of the chondrocytes.

CONCLUSION

Inhibition of aggrecanase-1 decreases aggrecan degradation in cultured rat chondrocytes. RNAi technique can be a useful means for studying extracellular matrix metabolism in the cartilage.

Effects of in vivo static compressive loading on aggrecan and type II and X collagens in the rat growth plate extracellular matrix

Mechanical loads are essential to normal bone growth, but excessive loads can lead to progressive deformities. In addition, growth plate extracellular matrix remodelling is essential to regulate the normal longitudinal bone growth process and to ensure physiological bone mineralization. In order to investigate the effects of static compression on growth plate extracellular matrix using an in vivo animal model, a loading device was used to precisely apply a compressive stress of 0.2 MPa for two weeks on the seventh caudal vertebra (Cd7) of rats during the pubertal growth spurt. Control, sham and loaded groups were studied. Growth modulation was quantified based on calcein labelling, and three matrix components (type II and X collagens, and aggrecan) were assessed using immunohistochemistry/safranin-O staining. As well, extracellular matrix components and enzymes (MMP-3 and -13, ADAMTS-4 and -5) were studied by qRT-PCR. Loading reduced Cd7 growth by 29% (p<0.05) and 15% (p=0.07) when compared to controls and shams respectively. No significant change could be observed in the mRNA expression of collagens and the proteolytic enzyme MMP-13. However, MMP-3 was significantly increased in the loaded group as compared to the control group (p<0.05). No change was observed in aggrecan and ADAMTS-4 and -5 expression. Low immunostaining for type II and X collagens was observed in 83% of the loaded rats as compared to the control rats. This in vivo study shows that, during pubertal growth spurt, two-week static compression reduced caudal vertebrae growth rates; this mechanical growth modulation occurred with decreased type II and X collagen proteins in the growth plate.

Specific inhibition of procollagen C-endopeptidase activity by synthetic peptide with conservative sequence found in chordin

Procollagen C-endopeptidase (BMP-1) and N-endopeptidase (ADAMTS-2) are key enzymes for correct and efficient conversion of fibrillar procollagens to their self assembling monomers. Thus, they have an essential role in building and controlling the quality of extracellular matrices (ECMs). Here, we tested inhibition of activity of the largest variant of BMP-1, a recombinant mammalian tolloid (mTld), in vitro by three synthetic peptides with conservative amino-acid sequences found in chordin using procollagen type I as a substrate. We also verified the specific action of best inhibitory 16 amino-acid peptide in the procollagen type I cleavage assay with the use of ADAMTS-2 (procollagen N-endopeptidase). Subsequently, we determined the critical residues and minimal sequence of six amino acids in the original 16 amino-acid peptide required to maintain the inhibitory potential. Studies on the interactions of 6 and 16 amino acid long peptides with the enzyme revealed their binding to non-catalytic, regulatory domains of mTld; the inhibitory activity was not due to the competition of peptides with the substrate for the enzyme active center, because mTld did not cleave the peptides. However, in the presence of mTld both peptides underwent cyclization by disulfide bond formation. Concluding, we have shown that procollagen C-endopeptidase may be specifically blocked via its non-catalytic domains by synthetic peptide consisting of 6 amino acids in the sequence found in highly conservative region of chordin. Thus, we hypothesize that the 6 amino-acid peptide could be a good candidate for anti-fibrotic drug development.

Molecular dissection of TIMP3 mutation S156C associated with Sorsby fundus dystrophy

Sorsby fundus dystrophy (SFD) is an autosomal dominant macular degeneration of late onset. A key feature of the disease is the thickening of Bruch's membrane, an ECM structure located between the RPE and the choroid. SFD is caused by mutations in the gene encoding the ECM-associated tissue inhibitor of metalloproteases-3 (TIMP3). We have recently generated two Timp3 gene-targeted mouse lines, one deficient for the murine gene (Timp3-/-) and one carrying an SFD-related S156C mutation. Based on extracts and cell cultures derived from tissues of these animals we now evaluated TIMP3 functionality and its contribution to SFD. We show that the activity levels of TIMP3 target proteases including TACE, ADAMTS4/5 and aggrecan-cleaving MMPs are similar in Timp3S156/+ and Timp3S156C/S156C mice when compared to controls. In Timp3-/- mice, a significant enhancement of enzyme activity was observed for TACE but not for ADAMTS4/5 and MMPs indicating a compensatory effect of other inhibitors regulating the latter two groups of proteases. Fibrin bead assays show that angiogenesis in Timp3S156/+ and Timp3S156C/S156C mice is not altered whereas increased formation of capillary tubes was observed in Timp3-/- animals over controls. Rescue experiments using recombinant proteins demonstrate that the inhibitory activities of TIMP3 towards TACE and aggrecan-cleaving MMPs as well as the anti-angiogenic properties of TIMP3 are not impaired by SFD mutation S156C. We finally demonstrate that wild-type and S156C-TIMP3 proteins block the binding of VEGF to its receptor VEGFR2 to a similar extent. Taken together, this study shows that S156C-TIMP3 retains its known functional properties suggesting that causes other than an imbalance in protease or angiogenic activities represent the primary molecular defect underlying SFD.

Spingosine-1-phosphate stimulates proliferation and counteracts interleukin-1 induced nitric oxide formation in articular chondrocytes

OBJECTIVE

Sphingosine-1-phosphate (S1P) is a messenger molecule, with important functions in inflammation and wound healing. The present study was performed to elucidate a possible role of S1P signaling in articular chondrocytes.

METHODS

Human and bovine primary chondrocytes were cultured in monolayer. Reverse transcriptase polymerase chain reaction (RT-PCR) was performed to detect S1P receptor mRNA. Proliferation of S1P stimulated chondrocytes was measured by 3H-thymidine uptake. Supernatants of cultured bovine chondrocytes stimulated with S1P alone or in combination with interleukin-1beta (IL-1beta) were tested for nitric oxide (NO) formation and expression of inducible nitric oxide synthase (iNOS). Matrixmetalloprotease-13 (MMP-13) and aggrecanase-1 (ADAMTS-4) were evaluated using real-time PCR. Glycosaminoglycan (GAG) loss from bovine cartilage explants was evaluated using the dimethylene blue method.

RESULTS

S1P1, S1P2 and S1P3 but not S1P4 and S1P5 receptor mRNA were detected in human and bovine chondrocytes. S1P dose dependently induced proliferation in bovine and human chondrocytes. S1P significantly reduced NO formation and iNOS mRNA and protein expression, both in un-stimulated and IL-1beta stimulated bovine chondrocytes. Furthermore, S1P dose dependently inhibited IL-1beta induced expression of ADAMTS-4 and MMP-13 and diminished IL-1beta mediated GAG depletion from cartilage explants.

CONCLUSION

These results suggest that S1P provides an anti-catabolic signal in articular chondrocytes.

Natural chondroitin sulphates increase aggregation of proteoglycan complexes and decrease adamts-5 expression in interleukin 1 -treated chondrocytes

OBJECTIVE

To assess the effect of natural chondroitin sulphate (CS) on the ability of neosynthesized sulphated proteoglycans (PGs) to aggregate in cultured chondrocytes treated with interleukin (IL)1 beta.

METHODS

Primary cultured rabbit articular chondrocytes were treated or not with IL1 beta alone or with concentrations of CS for 20 h. Neosynthesized PGs were labelled by incorporation of [35SO(4)]-sulphate and analysed by chromatography on Sepharose 2B columns. Gelatinolytic activity was measured by zymography, and matrix metalloproteinase (MMP)1 mRNA level in chondrocytes underwent real-time PCR. Expression of ADAMTS (for "a disintegrin and metalloproteinase with thrombospondin motifs") -4 and -5 was analysed by real-time PCR and western blotting.

RESULTS

The production of [35SO(4)]-labelled PGs was significantly increased with 10 microg/ml CS in the cellular pool rather than in the incubation medium. The addition of CS to IL1 beta-treated cells inhibited in part the disaggregation of sulphated PGs induced by IL1 beta. This inhibitory effect of CS is associated with a significant decrease in ADAMTS-5 expression at the mRNA and protein levels. No effect of CS was observed on IL1 beta-induced gelatinolytic activity, MMP1 mRNA expression or ADAMTS-4 expression.

CONCLUSION

CS increases the production of functional sulphated PGs in the direct environment of chondrocytes in vitro. This beneficial effect of CS in IL1 beta-treated cells is associated with decreased expression of ADAMTS-5.

Age-related changes in expression of tissue inhibitor of metalloproteinases-3 associated with transition from the notochordal nucleus pulposus to the fibrocartilaginous nucleus pulposus in rabbit intervertebral disc

STUDY DESIGN

Experimental study on age-related changes in expression of tissue inhibitor of metalloproteinases-3 (TIMP-3) associated with transition from notochordal nucleus pulposus (NP) to fibrocartilaginous NP in rabbit intervertebral disc (IVD).

OBJECTIVES

To identify roles of notochordal NP in extracellular matrix (ECM) metabolism of IVD.

SUMMARY OF BACKGROUND DATA

One of most interesting properties of TIMP-3 is to inhibit aggrecanases in addition to matrix metalloproteinases. Balance of aggrecanase/TIMP-3 is critical to maintain homeostasis of ECM metabolism.

METHODS

Four-week-old and 160-week-old male Japanese white rabbits were used. Age-related changes in IVDs were evaluated histologically using previously established grading system. Immunohistochemistry of TIMP-3 and semiquantitative reverse transcriptase-polymerase reaction (RT-PCR) of TIMP-3, a disintegrin and metalloproteinases with thrombospondin motifs (ADAMTS) 4, 5, and transforming growth factor-beta1 (TGF-beta1), were conducted.

RESULTS

Semiquantitative assessment of histologic changes indicated that 4-week-old rabbit was equivalent to fetus to 2-year-old human and 160-week-old rabbit was equivalent to 11- to 30-year-old human, particularly 11- to 16-year-old, which corresponds to transition period from notochordal to fibrocartilaginous NP. Immunohistochemistry revealed that TIMP-3 was positive in 4-week-old rabbit only. Semiquantitative RT-PCR revealed that levels of expressions of TGF-beta1 and TIMP-3 mRNAs in 4-week-old were significantly higher than those in 160-week-old rabbits. There was no significant difference in expression of ADAMTS4 mRNA. ADAMTS5 mRNA was not detected or extremely low in both groups. Expression of TIMP-3 mRNA in NP was upregulated by TGF-beta1 but was not affected by IL-1beta. On the contrary, expression of ADAMTS4 mRNA was not upregulated by TGF-beta1 but was upregulated by IL-1beta.

CONCLUSIONS

Levels of expression of TIMP-3 in notochordal NP were significantly lower in 160-week-old rabbits than those in 4-week-old rabbits. Decrease in expression of TIMP-3, possibly mediated in part by TGF-beta1, may cause imbalance of ADAMTS4/TIMP-3 ratio at transition period from notochordal to fibrocartilaginous NP.

Aggrecan degradation in human articular cartilage explants is mediated by both ADAMTS-4 and ADAMTS-5

OBJECTIVE

Recent published studies have shown that cartilage from ADAMTS-5-knockout mice, but not ADAMTS-4- or ADAMTS-1-knockout mice, is significantly protected from degradation. The present study was undertaken to evaluate the respective roles of these enzymes in human cartilage breakdown, using a small interfering RNA (siRNA) approach to assess the effects of inhibition of each enzyme in normal and osteoarthritic (OA) explants.

METHODS

The activities of siRNA specifically targeting ADAMTS-1, -4, and -5 were assessed by transfection into primary human chondrocytes and cultured human cartilage explants. At 24 hours, a cytokine stimulus was applied to normal, but not OA, samples to initiate a catabolic response. At designated times, total RNA was isolated and gene expression was measured by quantitative real-time reverse transcription-polymerase chain reaction. Aggrecan release and aggrecanase-generated neoepitope formation were determined by dye binding analysis and Western blotting, respectively.

RESULTS

Human chondrocytes and explants were efficiently transfected with siRNA that specifically decreased the expression of each targeted gene. Suppression of ADAMTS-4 and ADAMTS-5, individually or in combination, attenuated the degradation of aggrecan in cytokine-stimulated normal cartilage. A reduction in aggrecan degradation was also observed following siRNA-mediated knockdown of either gene in unstimulated OA cartilage. In contrast, knockdown of ADAMTS-1 failed to inhibit aggrecan loss.

CONCLUSION

Despite the apparent dominant role of ADAMTS-5 in genetically modified mice, our data suggest that both ADAMTS-4 and ADAMTS-5 contribute to the structural damage that characterizes human OA.

Adenoviral gene transfer of the endogenous inhibitor IkappaBalpha into human osteoarthritis synovial fibroblasts demonstrates that several matrix metalloproteinases and aggrecanases are nuclear factor-kappaB-dependent

OBJECTIVE

To investigate the role of the transcription factor nuclear factor-kB (NF-kappaB) in promoting inflammatory and destructive responses in human osteoarthritis (OA) synovial fibroblasts, by assessing the effect of NF-kappaB blockade on the production of cytokines and destructive enzymes.

METHODS

Infection with adenoviruses transferring the beta-galactosidase gene was used to ascertain that the OA fibroblasts could be infected (> 95%). Using an adenovirus transferring the inhibitory subunit IkappaBa, effective inhibition of NF-kappaB was achieved. The expression and production of several pro- and antiinflammatory cytokines and mediators, the major matrix metalloproteinases (MMP 1, 3, and 13), their main inhibitor tissue inhibitor of metalloproteinase-1 (TIMP-1), and the aggrecanases (ADAMTS4 and ADAMTS5) were measured by ELISA and/or reverse transcription-polymerase chain reaction, and their dependence on NF-kappaB evaluated.

RESULTS

The production of interleukin 6 (IL-6), monocyte chemoattractant protein-1, and RANTES was potently inhibited by IkBa overexpression, irrespective of stimulus, but IL-8 was unaffected. The p55 soluble tumor necrosis factor (TNF) receptor was unaffected, but the p75 soluble TNF receptor was potently inhibited by IkBa overexpression. MMP-1, MMP-3, and MMP-13 were inhibited by IkappaBa overexpression, at both the mRNA and protein levels, whereas TIMP-1 was unaffected. The mRNA gene expression of ADAMTS4 was also inhibited by IkappaBa overexpression, particularly in IL-1-stimulated cells, but ADAMTS5 was unaffected.

CONCLUSION

In OA synovial fibroblasts, inhibition of NF-kappaB has a beneficial effect on the balance between the expression of proinflammatory cytokines and antiinflammatory mediators. Inhibition of this transcription factor also results in the decreased expression of several destructive metalloproteinases and also the ADAMTS4 aggrecanase.

Identification of an ADAMTS-4 cleavage motif using phage display leads to the development of fluorogenic peptide substrates and reveals matrilin-3 as a novel substrate

ADAMTS-4 and ADAMTS-5 are aggrecanases responsible for the breakdown of cartilage aggrecan in osteoarthritis. Multiple ADAMTS-4 cleavage sites have been described in several matrix proteins including aggrecan, versican, and brevican, but no concise predictive cleavage motif has been identified for this protease. By screening a 13-mer peptide library with a diversity of 10(8), we have identified the ADAMTS-4 cleavage motif E-(AFVLMY)-X(0,1)-(RK)-X(2,3)-(ST)-(VYIFWMLA), with Glu representing P1. Several 13-mer peptides containing this motif, including DVQEFRGVTAVIR and HNEFRQRETYMVF, were shown to be substrates for ADAMTS-4. These peptides were found to be specific substrates for ADAMTS-4 as they were not cleaved by ADAMTS-5. Modification of these peptides with donor (6-FAM) and acceptor (QSY-9) molecules resulted in the development of fluorescence-based substrates with a Km of approximately 35 microM. Furthermore, the role of Glu at P1 and Phe at P1' in binding and catalysis was studied by exploring substitution of these amino acids with the D-isomeric forms. Substitution of P1 with dGlu was tolerable for binding, but not catalysis, whereas substitution of P1' with dPhe precluded both binding and catalysis. Similarly, replacement of Glu with Asp at P1 abolished recognition and cleavage of the peptide. Finally, BLAST results of the ADAMTS-4 cleavage motif identified matrilin-3 as a new substrate for ADAMTS-4. When tested, recombinant ADAMTS-4 effectively cleaved intact matrilin-3 at the predicted motif at Glu435/Ala436 generating two species of 45 and 5 kDa.

In vivo osteoarthritis target validation utilizing genetically-modified mice

Osteoarthritis (OA) is a progressive disease of cartilage degradation that significantly impacts quality of life. There are currently no effective treatments and, while a large number of potential therapeutic targets exist, most have not been validated in vivo. The range of OA models in the mouse has dramatically expanded in the last decade, beyond spontaneous models, to include genetically modified transgenic, knockout (KO) and knock-in (KI) mice that can develop premature cartilage degeneration reminiscent of OA. In addition, instability models of OA, either induced by intra-articular (IA) collagenase or surgery, are providing a set of tools to assist in the identification of disease-modifying OA drug (DMOAD) targets. These models are now vital tools to dissect the pathways essential to the pathogenesis of OA. Two targets, ADAMTS (a disintegrin and metalloproteinase with thrombospondin-like motifs)-5 and IL-1beta (interleukin-1 beta), have been validated in the surgical destabilization of the medial meniscus model (DMM) in KO mice. Other potential targets evaluated in instability models, either showed no disease modification or a worsening of disease, suggesting that those targets have no role, a protective role or that other, more destructive enzymes etc., can overcompensate. Development of small molecule or protein antagonist inhibitors of therapeutic targets require many years to bring to clinical trials and often confront potency and safety issues which impede successful progress. Validation, or confirmation of therapeutic targets in vivo is most clearly and efficiently obtained by using KO studies, than by creating potent and selective DMOADs to multiple potential targets. While the results in the mouse will not always transpose to the human condition, the track record of mouse knockouts corresponding to the human phenotype have been excellent. These results indicate that the evaluation of genetically modified mice will become increasingly important as we unravel the genes contributing to OA.

Substrate Conformation Modulates Aggrecanase (ADAMTS-4) Affinity and Sequence Specificity

Protease-substrate interactions are governed by a variety of structural features. Although the substrate sequence specificities of numerous proteases have been established, "topological specificities," whereby proteases may be classified based on recognition of distinct three-dimensional structural motifs, have not. The aggrecanase members of the ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs) family cleave a variety of proteins but do not seem to possess distinct sequence specificities. In the present study, the topological substrate specificity of ADAMTS-4 (aggrecanase-1) was examined using triple-helical or single-stranded poly(Pro) II helical peptides. Substrate topology modulated the affinity and sequence specificity of ADAMTS-4 with K(m) values indicating a preference for triple-helical structure. In turn, non-catalytic ADAMTS-4 domains were critical for hydrolysis of triple-helical and poly(Pro) II helical substrates. Comparison of ADAMTS-4 with MMP-1 (collagenase 1), MMP-13 (collagenase 3), trypsin, and thermolysin using triple-helical peptide (THP) and single-stranded peptide (SSP) substrates demonstrated that all five proteases possessed efficient "triple-helical peptidase" activity and fell into one of two categories: (k(cat)/K(m))(SSP) > (k(cat)/K(m))(THP) (thermolysin, trypsin, and MMP-13) or (k(cat)/K(m))(THP) > or = (k(cat)/K(m))(SSP) and (K(m))(SSP) > (K(m))(THP) (MMP-1 and ADAMTS-4). Overall these results suggest that topological specificity may be a guiding principle for protease behavior and can be utilized to design specific substrates and inhibitors. The triple-helical and single-stranded poly(Pro) II helical peptides represent the first synthetic substrates successfully designed for aggrecanases.

Signaling pathways implicated in oncostatin M-induced aggrecanase-1 and matrix metalloproteinase-13 expression in human articular chondrocytes

Molecular mechanisms of oncostatin M (OSM)-stimulated cartilage extracellular matrix catabolism and signaling pathways were investigated in human arthritic chondrocytes. OSM, alone or with Interleukin-1 (IL-1beta), increased glycosaminoglycan release and induced ADAMTS-4 and MMP-13 protein expression in human cartilage explants. OSM dose- and time-dependently increased ADAMTS-4 mRNA and MMP-13 protein expression in human femoral head chondrocytes. Extracellular signal-regulated kinases (ERK1/2)-MAPK pathway inhibitor, U0126, down-regulated ADAMTS-4 and MMP-13 induction by OSM. Janus kinase 2 (JAK2) inhibitor, AG490, suppressed OSM-induced ADAMTS-4 mRNA expression but did not affect MMP-13 levels while JAK3 pharmacological inhibitor and siRNA transfection suppressed both. Parthenolide, a signal transducer and activator of transcription (STAT1 and STAT3) phosphorylation inhibitor, reduced OSM-induced ADAMTS-4 and MMP-13 gene expression and prevented STAT1/3 DNA binding activity. Additionally, OSM-enhanced ADAMTS-4 mRNA and MMP-13 expression was down-regulated by phosphatidylinositol 3-kinase (PI3K) and Akt/PKB inhibitors, LY294002 and NL-71-101. Furthermore, JAK3 inhibition time-dependently down-regulated Akt but not ERK1/2 phosphorylation suggesting that Akt is a downstream target of JAK3. These results suggest that OSM-stimulated ADAMTS-4 and MMP-13 expression is mediated by ERK1/2, JAK3/STAT1/3 and PI3K/Akt and by cross talk between these pathways. The inhibitors of these cascades could block OSM-evoked degeneration of cartilage by ADAMTS-4 and MMP-13.

Role of aggrecanase 1 in Lyme arthritis

OBJECTIVE

Arthritis is one of the hallmarks of late-stage Lyme disease. Previous studies have shown that infection with Borrelia burgdorferi, the causative agent of Lyme disease, results in degradation of proteoglycans and collagen in cartilage. B burgdorferi do not appear to produce any exported proteases capable of digesting proteoglycans and collagen, but instead, induce and activate host proteases, such as matrix metalloproteinases (MMPs), which results in cartilage degradation. The role of aggrecanases in Lyme arthritis has not yet been determined. We therefore sought to delineate the contribution of aggrecanases to joint destruction in Lyme arthritis.

METHODS

We examined the expression patterns of aggrecanases 1 and 2 (ADAMTS 4 and 5, respectively) in B burgdorferi-infected primary human chondrocyte cell cultures, in synovial fluid samples from patients with active Lyme arthritis, and in the joints of mice by real-time quantitative reverse transcription-polymerase chain reaction and immunoblotting techniques. Bovine cartilage explants were used to determine the role of aggrecanases in B burgdorferi-induced cartilage degradation.

RESULTS

ADAMTS-4, but not ADAMTS-5, was induced in human chondrocytes infected with B burgdorferi. The active forms of ADAMTS-4 were increased in synovial fluid samples from patients with active Lyme arthritis and were elevated in the joints of mice infected with B burgdorferi. Using cartilage explant models of Lyme arthritis, it appeared that the cleavage of aggrecan was predominantly mediated by "aggrecanases" rather than MMPs.

CONCLUSION

The induction of ADAMTS-4 by B burgdorferi results in the cleavage of aggrecan, which may be an important first step that leads to permanent degradation of cartilage.

The cleavage of biglycan by aggrecanases

OBJECTIVE

Aggrecanase-1 [a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-4] and aggrecanase-2 (ADAMTS-5) have been named for their ability to degrade the proteoglycan aggrecan. While this may be the preferred substrate for these enzymes, they are also able to degrade other proteins. The aim of this work was to determine whether the aggrecanases could degrade biglycan and decorin.

METHODS

Biglycan, decorin and aggrecan were purified from human and bovine cartilage and subjected to degradation by recombinant aggrecanase-1 or aggrecanase-2. In vitro degradation was assessed by sodium dodecyl sulfate/polyacrylamide gel electrophoresis (SDS/PAGE) and immunoblotting, and the cleavage site in biglycan was determined by N-terminal amino acid sequencing. SDS/PAGE and immunoblotting were also used to assess in situ degradation in both normal and arthritic human articular cartilage.

RESULTS

Both aggrecanase-1 and aggrecanase-2 are able to cleave bovine and human biglycan at a site within their central leucine-rich repeat regions. Cleavage occurs at an asparagine-cysteine bond within the fifth leucine-rich repeat. In contrast, the closely related proteoglycan decorin is not a substrate for the aggrecanases. Analysis of human articular cartilage from osteoarthritic (OA) and rheumatoid arthritic (RA) joints showed that a biglycan degradation product of equivalent size is present in the extracellular matrix. No equivalent degradation product was, however, detectable in normal adult human articular cartilage.

CONCLUSION

Biglycan, which is structurally unrelated to aggrecan, can act as a substrate for aggrecanase-1 and aggrecanase-2, and these proteinases may account for at least part of the biglycan degradation that is present in arthritic cartilage.

Expression of aggrecan(ases) during murine preadipocyte differentiation and adipose tissue development

The expression and potential functional role of aggrecan in adipogenesis and adipose tissue development was investigated in murine models of obesity. Aggrecan, as well as the two aggrecanases ADAMTS-4 and ADAMTS-5 (A Disintegrin And Metalloproteinase with Thrombospondin motif) mRNAs, are expressed in subcutaneous (SC) and gonadal (GON) adipose tissues of mice. Their presence was confirmed by western blotting using adipose tissue extracts. In mice with nutritionally induced obesity (high fat diet) as well as in lean controls, aggrecan mRNA expression was downregulated whereas ADAMTS-4 and ADAMTS-5 were upregulated with time. In mice with genetically determined obesity (ob/ob), ADAMTS-5 mRNA was upregulated in both SC and GON adipose tissues, as compared to wild-type (WT) mice (p<0.001). Enhanced aggrecanase expression levels in these tissues were associated with significantly elevated levels of G1-NITEGE, a degradation product of aggrecan. Thus, aggrecan levels were high at the early stages of adipose tissue development in mice, whereas its production decreased and its degradation increased during development of obesity. A functional role of aggrecan in promoting early stages of adipogenesis is supported by the findings that it stimulated the in vitro differentiation of 3T3-F442A preadipocytes and the de novo in vivo accumulation of fat in Matrigel plaques injected into WT mice. Proteoglycans in the extracellular matrix of adipose tissue, such as aggrecan, may contribute to the regulation of lipid uptake and obesity in mice.

Differential regulation of matrix degrading enzymes in a TNFalpha-induced model of nucleus pulposus tissue degeneration

Intervertebral disc degeneration occurs commonly and is linked to persistent back pain and the development of disc herniation. The mechanisms responsible for tissue catabolism have not yet been fully elucidated. Previously we characterized an in vitro model of TNFalpha-induced nucleus pulposus degeneration, which demonstrates decreased expression of matrix macromolecules, increased expression of matrix degrading enzymes, and the activation of aggrecanase-mediated proteoglycan degradation [Seguin, C.A., Pilliar, R.M., Roughley, P.J., and Kandel, R.A. 2005. Tumor necrosis factor-alpha modulates matrix production and catabolism in nucleus pulposus tissue. Spine 30: 1940-1948]. This study explores the intracellular pathways activated during TNFalpha-induced matrix degradation. We demonstrate that in nucleus pulposus cells, the p38 and JNK pathways regulate induction of MMP-1 and -3; p38, JNK, and NF-kappaB regulate the induction of MMP-13; and ERK regulates the up-regulation of MT1-MMP mRNA in response to TNFalpha. Induction of ADAMTS-4 and -5 mRNA occurred downstream of NF-kappaB activation. Depletion of tissue proteoglycans was mediated by ERK and NF-kappaB-dependent "aggrecanase" activity, suggesting MT1-MMP and ADAMTS-4 and -5 as effectors of TNFalpha-induced tissue catabolism.

An alternative spliced transcript of ADAMTS4 is present in human synovium from OA patients

The major proteoglycan of articular cartilage aggrecan is a substrate for ADAMTS4. RT-PCR analysis of human osteoarthritic (OA) synovial co-cultures using oligonucleotide primers designed to amplify across the exon 8/9 junction of human ADAMTS4 resulted in the amplification of two products, the expected product and a smaller product missing 161 bp from the 5' end of exon 9, the result of alternative splicing in which exon 8 joins to a cryptic 3' splice site within exon 9. The protein produced would be identical to human ADAMTS4 up to Arg(696), and would have a new C-terminal domain with no commonality with the ADAMTS4 spacer domain. Changes in the C-terminal domain of ADAMTS4 may alter its substrate specificity.

Development and characterization of a highly specific and sensitive sandwich ELISA for detection of aggrecanase-generated aggrecan fragments

OBJECTIVE

To develop an enzyme linked immunosorbent assay (ELISA) to quantify the levels of specific aggrecan fragments generated by aggrecanase-mediated cleavage at the 373Glu-374 Ala bond within the aggrecan interglobular domain.

METHODS

The ELISA employs a commercially available monoclonal antibody to capture aggrecan fragments containing keratan sulfate (KS). Aggrecan fragments generated by cleavage at the Glu-Ala bond were then detected using a monoclonal neoepitope antibody (mAb OA-1) that specifically recognizes the N-terminal sequence 'ARGSVIL'.

RESULTS

The mAb OA-1 antibody was highly specific for the immunizing neoepitope peptide since neither peptides spanning the cleavage site nor mutated peptides were detected. Aggrecan fragments generated by ADAMTS-4 digested human aggrecan monomers and from IL-1-stimulated human cartilage explants were quantified by the ELISA, and we observed increased sensitivity of the ELISA compared to mAb OA-1 Western analysis. We also observed that the basal, as well as IL-1-stimulated production of ARGS aggrecan fragments from human articular cartilage explants was blocked by a selective aggrecanase inhibitor, consistent with generation of the ARGS neoepitope in human articular cartilage being mediated by aggrecanase. Using purified human aggrecan digested by ADAMTS-4 as standard to quantify ARGS aggrecan fragments in human synovial fluids, we determined that the calculated amount of ARGSVIL-aggrecan fragments by ELISA measurement is in agreement with the published levels of these fragments, supporting its potential utility as a biomarker assay for osteoarthritis.

CONCLUSION

We have developed an assay that detects and quantifies specific aggrecan fragments generated by aggrecanase-mediated cleavage. Because aggrecanase mediates degradation of human articular aggrecan in joint disease, the KS/mAb OA-1 ELISA may serve as a biomarker assay for evaluation of preclinical and clinical samples.

Protein kinase Czeta is up-regulated in osteoarthritic cartilage and is required for activation of NF-kappaB by tumor necrosis factor and interleukin-1 in articular chondrocytes

Protein kinase Czeta (PKCzeta) is an intracellular serine/threonine protein kinase that has been implicated in the signaling pathways for certain inflammatory cytokines, including interleukin-1 (IL-1) and tumor necrosis factor alpha (TNF-alpha), in some cell types. A study of gene expression in articular chondrocytes from osteoarthritis (OA) patients revealed that PKCzeta is transcriptionally up-regulated in human OA articular cartilage clinical samples. This finding led to the hypothesis that PKCzeta may be an important signaling component of cytokine-mediated cartilage matrix destruction in articular chondrocytes, believed to be an underlying factor in the pathophysiology of OA. IL-1 treatment of chondrocytes in culture resulted in rapidly increased phosphorylation of PKCzeta, implicating PKCzeta activation in the signaling pathway. Chondrocyte cell-based assays were used to evaluate the contribution of PKCzeta activity in NF-kappaB activation and extracellular matrix degradation mediated by IL-1, TNF, or sphingomyelinase. In primary chondrocytes, IL-1 and TNF-alpha caused an increase in NF-kappaB activity resulting in induction of aggrecanase-1 and aggrecanase-2 expression, with consequent increased proteoglycan degradation. This effect was blocked by the pan-specific PKC inhibitors RO 31-8220 and bisindolylmaleimide I, partially blocked by Gö 6976, and was unaffected by the PKCzeta-sparing inhibitor calphostin C. A cell-permeable PKCzeta pseudosubstrate peptide inhibitor was capable of blocking TNFand IL-1-mediated NF-kappaB activation and proteoglycan degradation in chondrocyte pellet cultures. In addition, overexpression of a dominant negative PKCzeta protein effectively prevented cytokine-mediated NF-kappaB activation in primary chondrocytes. These data implicate PKCzeta as a necessary component of the IL-1 and TNF signaling pathways in chondrocytes that result in catabolic destruction of extracellular matrix proteins in osteoarthritic cartilage.

Expression of ADAMTS-4 (aggrecanase-1) and possible involvement in regression of lumbar disc herniation

STUDY DESIGN

Examination of ADAMTS-4 expression, and cellular lineages, distribution, and numbers of ADAMTS-4 (aggrecanase-1) expressing cells in herniated lumbar intervertebral discs.

OBJECTIVE

To determine the expression of ADAMTS-4, a metalloproteinase capable of digesting aggrecan, and its role in herniated lumbar intervertebral disc degradation.

SUMMARY OF BACKGROUND DATA

Matrix metalloproteinases degrade extracellular matrix of herniated discs, but the mechanism of aggrecan degradation, the major component of intervertebral discs, is poorly understood.

METHODS

Surgically resected herniated lumbar intervertebral discs from 22 patients were subclassified into protrusion, subligamentous extrusion, transligamentous extrusion, and sequestration types. Reverse transcriptase polymerase chain reaction, Western blot, and immunohistochemistry were used to evaluate ADAMTS-4 messenger ribonucleic acid and protein expression.

RESULTS

Expression of ADAMTS-4 messenger ribonucleic acid and protein was shown in the samples of herniated lumbar intervertebral discs. Immunohistochemical staining showed that ADAMTS-4 was mainly localized in CD68-positive mononuclear cells in granulation and adjacent disc tissues. ADAMTS-4 positive cell counts were significantly higher in transligamentous extrusion and sequestration than protrusion and subligamentous extrusion types. Alcian blue staining showed a decrease of proteoglycan in transligamentous extrusion and sequestration cases.

CONCLUSIONS

Macrophages infiltrating granulation and adjacent disc tissues express ADAMTS-4, suggesting its involvement in herniated disc regression.

Regulation of the human ADAMTS-4 promoter by transcription factors and cytokines

ADAMTS-4 (aggrecanase-1) is a metalloprotease that plays a role in aggrecan degradation in the cartilage extracellular matrix. In order to understand the regulation of ADAMTS-4 gene expression we have cloned and characterized a functional 4.5kb human ADAMTS-4 promoter. Sequence analysis of the promoter revealed the presence of putative binding sites for nuclear factor of activated T cells (NFAT) and Runx family of transcription factors that are known to regulate chondrocyte maturation and differentiation. Using promoter-reporter assays and mRNA analysis we have analyzed the role of chondrocyte-expressed transcription factors NFATp and Runx2 and have shown that ADAMTS-4 is a potential downstream target of these two factors. Our results suggest that inhibition of the expression/function of NFATp and/or Runx2 may enable us to modulate aggrecan degradation in normal physiology and/or in degenerative joint diseases. The ADAMTS-4 promoter would serve as a valuable mechanistic tool to better understand the regulation of ADAMTS-4 expression by signaling pathways that modulate cartilage matrix breakdown.

ADAMTS-1 and -4 are up-regulated following transient middle cerebral artery occlusion in the rat and their expression is modulated by TNF in cultured astrocytes

ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs) enzymes are a recently described group of metalloproteinases. The substrates degraded by ADAMTS-1, -4 and -5 suggest that they play a role in turnover of extracellular matrix in the central nervous system (CNS). ADAMTS-1 is also known to exhibit anti-angiogenic activity. Their main endogenous inhibitor is tissue inhibitor of metalloproteinases (TIMP)-3. The present study was designed to investigate ADAMTS-1, -4 and -5 and TIMP-3 expression after experimental cerebral ischaemia and to examine whether cytokines known to be up-regulated in stroke could alter their expression by astrocytes in vitro. Focal cerebral ischaemia was induced by transient middle cerebral artery occlusion in the rat using the filament method. Our results demonstrate a significant increase in expression of ADAMTS-1 and -4 in the occluded hemisphere but no significant change in TIMP-3. This was accompanied by an increase in mRNA levels for interleukin (IL)-1beta, IL-1 receptor antagonist (IL-1ra) and tumour necrosis factor (TNF). ADAMTS-4 mRNA and protein were up-regulated by TNF in primary human astrocyte cultures. The increased ADAMTS-1 and -4 in experimental stroke, together with no change in TIMP-3, may promote ECM breakdown after stroke, enabling infiltration of inflammatory cells and contributing to brain injury. In vitro studies suggest that the in vivo modulation of ADAMTS-1 and -4 may be controlled in part by TNF.

Regulation of procollagen amino-propeptide processing during mouse embryogenesis by specialization of homologous ADAMTS proteases: insights on collagen biosynthesis and dermatosparaxis

Mutations in ADAMTS2, a procollagen amino-propeptidase, cause severe skin fragility, designated as dermatosparaxis in animals, and a subtype of the Ehlers-Danlos syndrome (dermatosparactic type or VIIC) in humans. Not all collagen-rich tissues are affected to the same degree, which suggests compensation by the ADAMTS2 homologs ADAMTS3 and ADAMTS14. In situ hybridization of Adamts2, Adamts3 and Adamts14, and of the genes encoding the major fibrillar collagens, Col1a1, Col2a1 and Col3a1, during mouse embryogenesis, demonstrated distinct tissue-specific, overlapping expression patterns of the protease and substrate genes. Adamts3, but not Adamts2 or Adamts14, was co-expressed with Col2a1 in cartilage throughout development, and with Col1a1 in bone and musculotendinous tissues. ADAMTS3 induced procollagen I processing in dermatosparactic fibroblasts, suggesting a role in procollagen I processing during musculoskeletal development. Adamts2,but not Adamts3 or Adamts14, was co-expressed with Col3a1 in many tissues including the lungs and aorta, and Adamts2-/- mice showed widespread defects in procollagen III processing. Adamts2-/- mice had abnormal lungs,characterized by a decreased parenchymal density. However, the aorta and collagen fibrils in the aortic wall appeared normal. Although Adamts14 lacked developmental tissue-specific expression, it was co-expressed with Adamts2 in mature dermis, which possibly explains the presence of some processed skin procollagen in dermatosparaxis. The data show how evolutionarily related proteases with similar substrate preferences may have distinct biological roles owing to tissue-specific gene expression,and provide insights into collagen biosynthesis and the pathobiology of dermatosparaxis.

Mammalian expression of full-length bovine aggrecan and link protein: formation of recombinant proteoglycan aggregates and analysis of proteolytic cleavage by ADAMTS-4 and MMP-13

Aggrecan, a large chondroitin sulfate (CS) and keratan sulfate (KS) proteoglycan, has not previously been expressed as a full-length recombinant molecule. To facilitate structure/function analysis, we have characterized recombinant bovine aggrecan (rbAgg) and link protein expressed in COS-7 cells. We demonstrate that C-terminally truncated rbAgg was not secreted. Gel filtration chromatography of rbAgg and isolated glycosaminoglycan (GAG) chains, and their susceptibility to chondroitinase ABC digestion indicate that the GAG chains are predominantly CS, which likely occupy fewer serine residues than native aggrecan. To confirm functionality, we determined that rbAgg bound hyaluronan and recombinant link protein to form proteoglycan aggregates. In addition, cleavage of rbAgg by ADAMTS-4 revealed that the p68 form of ADAMTS-4 preferentially cleaves within the CS-2 domain, whereas the p40 form only effectively cleaves within the interglobular domain (IGD). MMP-13 cleaved rbAgg within the IGD, but cleaved more rapidly at a site within the CS domains, suggesting a role in C-terminal processing of aggrecan. Our results demonstrate that recombinant aggrecan can be used for in vitro analyses of matrix protease-dependent degradation of aggrecan in the IGD and CS domains, and both recombinant aggrecan and link protein can be used to study the assembly of proteoglycan aggregates with hyaluronan.