Paediatrics (RCH) - Research Publications
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ItemJNK-2 Controls Aggrecan Degradation in Murine Articular Cartilage and the Development of Experimental Osteoarthritis(WILEY, 2016-05)OBJECTIVE: The pathogenesis of osteoarthritis (OA) is poorly understood. Loss of the proteoglycan aggrecan from cartilage is an early event. Recently, we identified a role for the JNK pathway, particularly JNK-2, in human articular chondrocytes in vitro in regulating aggrecan degradation. The present study was undertaken to investigate whether JNK-2 has a similar function in vivo and to examine its role in gene expression. METHODS: Aggrecan fragments were analyzed by Western blotting. OA was induced by destabilization of the medial meniscus (DMM) and assessed at 4, 8, and 12 weeks after surgery. Knee sections were stained with Safranin O. Medial compartments were scored by histologic grading for aggrecan loss and cartilage damage. RNA was extracted from JNK-2(-/-) and wild-type mouse knees 6 hours after DMM or after interleukin-1 stimulation of the proximal epiphysis, and expression of 33 DMM-regulated genes was analyzed with quantitative polymerase chain reaction-customized array cards. RESULTS: In vitro, basal and interleukin-1- or tumor necrosis factor-stimulated release of aggrecanase-generated aggrecan fragments was greatly reduced in cartilage from JNK-2(-/-) mice. In the OA model, JNK-2(-/-) mice exhibited significant reduction of aggrecanase-generated fragments and cartilage damage. Of 33 genes investigated, 13 were significantly down-regulated in JNK-2(-/-) mice compared with wild-type mice, following DMM. These included Has1, Adamts4, Tnf, Il6, Il18, Il18rap, Il1a, Inhba, Cd68, Ngf, Ccr2, Wnt16, and Tnfaip6, but not Adamts5. CONCLUSION: Our results demonstrate that JNK-2 regulates aggrecan degradation in cultured murine cartilage and surgically induced OA in vivo following mechanical destabilization of the knee joint. This implicates the JNK signaling pathway in OA and suggests potential novel approaches to therapy.
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ItemMetalloprotease inhibitor TIMP proteins control FGF-2 bioavailability and regulate skeletal growth(ROCKEFELLER UNIV PRESS, 2019-09)Regulated growth plate activity is essential for postnatal bone development and body stature, yet the systems regulating epiphyseal fusion are poorly understood. Here, we show that the tissue inhibitors of metalloprotease (TIMP) gene family is essential for normal bone growth after birth. Whole-body quadruple-knockout mice lacking all four TIMPs have growth plate closure in long bones, precipitating limb shortening, epiphyseal distortion, and widespread chondrodysplasia. We identify TIMP/FGF-2/IHH as a novel nexus underlying bone lengthening where TIMPs negatively regulate the release of FGF-2 from chondrocytes to allow IHH expression. Using a knock-in approach that combines MMP-resistant or ADAMTS-resistant aggrecans with TIMP deficiency, we uncouple growth plate activity in axial and appendicular bones. Thus, natural metalloprotease inhibitors are crucial regulators of chondrocyte maturation program, growth plate integrity, and skeletal proportionality. Furthermore, individual and combinatorial TIMP-deficient mice demonstrate the redundancy of metalloprotease inhibitor function in embryonic and postnatal development.
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ItemMast Cell-Restricted, Tetramer-Forming Tryptases Induce Aggrecanolysis in Articular Cartilage by Activating Matrix Metalloproteinase-3 and-13 Zymogens(AMER ASSOC IMMUNOLOGISTS, 2013-08-01)Mouse mast cell protease (mMCP)-6-null C57BL/6 mice lost less aggrecan proteoglycan from the extracellular matrix of their articular cartilage during inflammatory arthritis than wild-type (WT) C57BL/6 mice, suggesting that this mast cell (MC)-specific mouse tryptase plays prominent roles in articular cartilage catabolism. We used ex vivo mouse femoral head explants to determine how mMCP-6 and its human ortholog hTryptase-β mediate aggrecanolysis. Exposure of the explants to recombinant hTryptase-β, recombinant mMCP-6, or lysates harvested from WT mouse peritoneal MCs (PMCs) significantly increased the levels of enzymatically active matrix metalloproteinases (MMP) in cartilage and significantly induced aggrecan loss into the conditioned media, relative to replicate explants exposed to medium alone or lysates collected from mMCP-6-null PMCs. Treatment of cartilage explants with tetramer-forming tryptases generated aggrecan fragments that contained C-terminal DIPEN and N-terminal FFGVG neoepitopes, consistent with MMP-dependent aggrecanolysis. In support of these data, hTryptase-β was unable to induce aggrecan release from the femoral head explants obtained from Chloe mice that resist MMP cleavage at the DIPEN↓FFGVG site in the interglobular domain of aggrecan. In addition, the abilities of mMCP-6-containing lysates from WT PMCs to induce aggrecanolysis were prevented by inhibitors of MMP-3 and MMP-13. Finally, recombinant hTryptase-β was able to activate latent pro-MMP-3 and pro-MMP-13 in vitro. The accumulated data suggest that human and mouse tetramer-forming tryptases are MMP convertases that mediate cartilage damage and the proteolytic loss of aggrecan proteoglycans in arthritis, in part, by activating the zymogen forms of MMP-3 and MMP-13, which are constitutively present in articular cartilage.
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ItemTransparency Is the Key to Quality(AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC, 2015-12-11)
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ItemHigh-bandwidth AFM-based rheology is a sensitive indicator of early cartilage aggrecan degradation relevant to mouse models of osteoarthritis(ELSEVIER SCI LTD, 2015-01-02)Murine models of osteoarthritis (OA) and post-traumatic OA have been widely used to study the development and progression of these diseases using genetically engineered mouse strains along with surgical or biochemical interventions. However, due to the small size and thickness of murine cartilage, the relationship between mechanical properties, molecular structure and cartilage composition has not been well studied. We adapted a recently developed AFM-based nano-rheology system to probe the dynamic nanomechanical properties of murine cartilage over a wide frequency range of 1 Hz to 10 kHz, and studied the role of glycosaminoglycan (GAG) on the dynamic modulus and poroelastic properties of murine femoral cartilage. We showed that poroelastic properties, highlighting fluid-solid interactions, are more sensitive indicators of loss of mechanical function compared to equilibrium properties in which fluid flow is negligible. These fluid-flow-dependent properties include the hydraulic permeability (an indicator of the resistance of matrix to fluid flow) and the high frequency modulus, obtained at high rates of loading relevant to jumping and impact injury in vivo. Utilizing a fibril-reinforced finite element model, we estimated the poroelastic properties of mouse cartilage over a wide range of loading rates for the first time, and show that the hydraulic permeability increased by a factor ~16 from knormal=7.80×10(-16)±1.3×10(-16) m(4)/N s to kGAG-depleted=1.26×10(-14)±6.73×10(-15) m(4)/N s after GAG depletion. The high-frequency modulus, which is related to fluid pressurization and the fibrillar network, decreased significantly after GAG depletion. In contrast, the equilibrium modulus, which is fluid-flow independent, did not show a statistically significant alteration following GAG depletion.
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ItemNovel Elements of the Chondrocyte Stress Response Identified Using an in Vitro Model of Mouse Cartilage Degradation(AMER CHEMICAL SOC, 2016-03)The destruction of articular cartilage in osteoarthritis involves chondrocyte dysfunction and imbalanced extracellular matrix (ECM) homeostasis. Pro-inflammatory cytokines such as interleukin-1α (IL-1α) contribute to osteoarthritis pathophysiology, but the effects of IL-1α on chondrocytes within their tissue microenvironment have not been fully evaluated. To redress this we used label-free quantitative proteomics to analyze the chondrocyte response to IL-1α within a native cartilage ECM. Mouse femoral heads were cultured with and without IL-1α, and both the tissue proteome and proteins released into the media were analyzed. New elements of the chondrocyte response to IL-1α related to cellular stress included markers for protein misfolding (Armet, Creld2, and Hyou1), enzymes involved in glutathione biosynthesis and regeneration (Gstp1, Gsto1, and Gsr), and oxidative stress proteins (Prdx2, Txn, Atox1, Hmox1, and Vnn1). Other proteins previously not associated with the IL-1α response in cartilage included ECM components (Smoc2, Kera, and Crispld1) and cysteine proteases (cathepsin Z and legumain), while chondroadherin and cartilage-derived C-type lectin (Clec3a) were identified as novel products of IL-1α-induced cartilage degradation. This first proteome-level view of the cartilage IL-1α response identified candidate biomarkers of cartilage destruction and novel targets for therapeutic intervention in osteoarthritis.
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ItemCartilage MicroRNA Dysregulation During the Onset and Progression of Mouse Osteoarthritis Is Independent of Aggrecanolysis and Overlaps With Candidates From End-Stage Human Disease(WILEY, 2018-03)OBJECTIVE: To identify candidate microRNAs (miRNAs) that potentially regulate the initiation and progression of osteoarthritis (OA). METHODS: OA was induced in 10-12-week-old male wild-type C57BL/6 mice and in mice resistant to aggrecanase cleavage (Acan p.374ALGS→374NVYS) by destabilization of the medial meniscus (DMM). Pathologic changes of OA were scored histologically. RNA from cartilage and subchondral bone was harvested in parallel by laser microdissection at 1 week and 6 weeks postsurgery. Global miRNA expression profiling was performed using Agilent microarrays and was validated by quantitative polymerase chain reaction analysis. RESULTS: Wild-type DMM mice had characteristic cartilage degeneration, subchondral bone sclerosis, and osteophyte formation. While no miRNA dysregulation was seen in subchondral bone, 139 miRNAs were differentially expressed in cartilage obtained at 1 and/or 6 weeks after OA initiation from wild-type mice that underwent DMM. To prioritize OA candidates, dysregulated miRNAs with human orthologs were filtered, and paired miRNA/messenger RNA (mRNA) expression analysis was conducted to identify those with corresponding changes in mRNA target transcripts in the DMM mouse cartilage. An important cohort also overlapped with miRNAs identified in human end-stage OA. Comparisons of miRNA dysregulation in DMM mouse cartilage where aggrecan cleavage was genetically ablated demonstrated that all candidates were independent of aggrecan breakdown, earmarking these as important to the critical stages of OA initiation. Furthermore, functional enrichment analysis and data annotation revealed the responses to mechanical stimuli, apoptotic processes, and core extracellular matrix structural and regulatory factors to be potentially influenced by OA-dysregulated miRNA/mRNA networks. CONCLUSION: Our comprehensive analyses identified high-priority miRNA candidates that have potential as biomarkers and therapeutic targets in human OA.
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ItemBioactivity in an Aggrecan 32-mer Fragment Is Mediated via Toll-like Receptor 2(WILEY, 2015-05)OBJECTIVE: To determine whether an aggrecan 32-mer fragment derived from dual ADAMTS and matrix metalloproteinase (MMP) cleavage in the aggrecan interglobular domain was bioactive and, if so, to elucidate its mechanism of action. METHODS: Mouse primary chondrocytes, synovial fibroblasts, or peritoneal macrophages, human primary chondrocytes, and cells or cell lines from myeloid differentiation factor 88 (MyD88)-deficient and Toll-like receptor 2 (TLR-2)-deficient mice were stimulated with synthetic mouse 32-mer peptide, human 32-mer peptide, a 32-mer scrambled peptide, or native, glycosylated 32-mer peptide. Cells stimulated with 32-mer peptide were analyzed for changes in messenger RNA (mRNA) expression by quantitative polymerase chain reaction. Conditioned medium was analyzed for levels of interleukin-6 protein by an AlphaLISA or for levels of MMP-3 and MMP-13 protein by Western blotting. NF-κB activation was measured in a luciferase reporter assay. RESULTS: Treatment of mouse cells or cartilage explants with 32-mer peptide or scrambled peptide revealed that the 32-mer peptide, but not the scrambled peptide, had antianabolic, procatabolic, and proinflammatory bioactivity in vitro. Chondrocytes, synovial fibroblasts, and macrophages from MyD88-deficient mice failed to respond to 32-mer peptide stimulation. A macrophage cell line derived from TLR-2-deficient mice also failed to respond to 32-mer peptide stimulation. Stimulation of human chondrocytes with human 32-mer peptide increased the expression of catabolic markers at the mRNA and protein levels. Mouse and human 32-mer peptide stimulated NF-κB activation in a TLR-2-dependent reporter assay, and the response of chondrocytes from both species to native, glycosylated 32-mer peptide was similar to the response to synthetic peptides. CONCLUSION: The aggrecan 32-mer fragment is a novel endogenous ligand of TLR-2 with the potential to accelerate cartilage destruction in vivo.
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ItemNo Preview AvailableADAMTS-5 takes centre stage in new developments for aggrecanase inhibitors(ELSEVIER SCI LTD, 2015-08)
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ItemNo Preview AvailableCytokine-Induced Increases in ADAMTS-4 Messenger RNA Expression Do Not Lead to Increased Aggrecanase Activity in ADAMTS-5-Deficient Mice(WILEY, 2010-11)OBJECTIVE: To compare the regulation of aggrecanase messenger RNA (mRNA) and enzyme activity by proinflammatory cytokines in primary mouse chondrocytes. METHODS: Primary chondrocytes were isolated from knee epiphyses of 6-8-day-old mice and cultured as monolayers. The cells were incubated with tumor necrosis factor α (TNFα), oncostatin M (OSM), or interleukin-6 (IL-6)/soluble IL-6 receptor, and mRNA levels were measured by quantitative polymerase chain reaction at various time points. To measure aggrecanase activity, the cells were incubated with cytokine in the presence of exogenous aggrecan, and substrate cleavage was measured using antibodies to neoepitopes. RESULTS: Expression of both ADAMTS-4 and ADAMTS-5 mRNA was up-regulated by TNFα and OSM. ADAMTS-5 mRNA expression was also up-regulated by IL-6. Treatment of wild-type mouse chondrocytes with each of the 3 cytokines increased cleavage of aggrecan at Glu(373)↓(374) Ala and Glu(1670)↓(1671) Gly; in chondrocytes lacking ADAMTS-5 activity, there was negligible cleavage at either site despite increased expression of ADAMTS-4 mRNA in the presence of TNFα or OSM. None of the cytokines substantially altered mRNA expression of ADAMTS-1 or ADAMTS-9. CONCLUSION: Despite substantial increases in the expression of ADAMTS-4 mRNA induced by TNFα and OSM, these cytokines induced little if any increase in aggrecanolysis in ADAMTS-5-deficient mouse chondrocytes. Our data show a poor correlation between the level of cytokine-induced ADAMTS-4 mRNA expression and the level of aggrecan-degrading activity in cultured chondrocytes.