| 31. |
- Dudhia, Jayesh, et al.
(författare)
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Aging enhances a mechanically-induced reduction in tendon strength by an active process involving matrix metalloproteinase activity
- 2007
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Ingår i: Aging Cell. - : Wiley. - 1474-9726 .- 1474-9718. ; 6:4, s. 547-556
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Tidskriftsartikel (refereegranskat)abstract
- Age-associated and degenerative loss of functional integrity in soft tissues develops from effects of cumulative and subtle changes in their extracellular matrix (ECM). The highly ordered tendon ECM provides the tissue with its tensile strength during loading. As age and exercise collude in the high incidence of tendinopathies, we hypothesized that aged tendons fail due to cumulative damage resulting from a combination of diminished matrix repair and fragmentation of ECM proteins induced by prolonged cyclical loading, and that this is an active cell-mediated process. We developed an equine tendon explant model to examine the effect of age on the influence of prolonged cyclical loading at physiologically relevant strain rates (5% strain, 1 Hz for 24 h) on tissue mechanical properties, loss of ECM protein and matrix metalloproteinase (MMP) expression. We show significantly diminished mechanical strength of cyclically loaded tissue compared to controls (39.7 +/- 12%, P <= 0.05) this reduction was dependent on the presence of both viable cells and metalloproteinase activity. Furthermore, tendon from older specimens was more susceptible to weakening (11-30 years, 50% P <= 0.05) compared to immature and young mature tissue (1-3 years, 34%; 4-10 years, 35%, respectively). Cyclical load also induced release of degraded cartilage oligomeric matrix protein, an integral ECM protein, an effect that could be mimicked by culture with fibronectin fragments. These findings indicate prolonged cyclical loading of physiological magnitude decreases tendon tensile strength by an active process, and that MMPs may contribute to loss of functional competence, exaggerated by age, via load-induced proteolytic disruption of the ECM.
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| 32. |
- Ekman, S, et al.
(författare)
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Ultrastructural immunolocalisation of bone sialoprotein in the osteocartilagenous interface of the equine third carpal bone
- 2005
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Ingår i: Equine Veterinary Journal. - : Wiley. - 0425-1644 .- 2042-3306. ; 37:1, s. 26-30
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Tidskriftsartikel (refereegranskat)abstract
- Reasons for performing study: One of the most common causes of lameness in racehorses is osteoarthritis (OA). Pathogenesis is not clear and pathological processes of the different joint tissues interact in often progressive events. The interface between cartilage and newly synthesised bone has been shown to be particularly enriched in bone sialoprotein (BSP), a cell-binding matrix protein. Objectives: To establish whether changes in the concentration of BSP may serve as a marker for early biochemical changes of the subchondral bone. Methods: Articular cartilage, cartilage/bone interface and subchondral bone of the proximal third carpal bone from 3 Standardbred trotters were analysed ultrastructurally for the presence of BSP in normal and degenerative areas. Results: A marked increase of BSP in the cartilage/bone interface with degenerative changes of the bone and cartilage compared to the morphologically intact cartilage/bone interface was noted, but levels of the protein were distinctly lower in the distal bone. Conclusions: The results indicate that BSP has the potential to be used as a marker for changes in bone metabolism in the subchondral one. Potential relevance: Tools to monitor early biochemical changes within the connective tissues of the joint in vivo are essential in studies of the pathogenesis of OA. These could be used to monitor and understand such changes in relation to load, exercise, training programmes, inflammation and the development of OA.
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| 33. |
- Feng, Haoyu, et al.
(författare)
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Extracellular matrix in disc degeneration.
- 2006
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Ingår i: Journal of Bone and Joint Surgery. American Volume. - 1535-1386. ; 88:Suppl 2, s. 25-29
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Tidskriftsartikel (refereegranskat)abstract
- The extracellular matrix of the intervertebral disc structures contains many molecules also found in cartilage. The extremely polyanionic proteoglycans play a central role, particularly in the nucleus, by creating an osmotic environment leading to retention of water and ensuing resistance to deformation—important for the resilience of the tissue. Another major structural entity particularly important in the anulus is the network of collagen fibers; fibril-forming collagen 1 is a major constituent. The collagen fibrils in the anulus are largely oriented in sheets around the nucleus. A number of molecules present in the matrix regulate and direct the collagen fibril assembly by interacting with the collagen molecule and also the formed fibril. Several of these molecules bind by one domain to the collagen fiber and present another functional domain to interact either with other fibers or with other matrix constituents. In this manner the collagen fibers are cross-linked into a network that provides tensile strength and distributes load over large parts of the anulus. Diminished function in these cross-bridging molecules will lead to loss of mechanical properties of the collagen network and result in an impaired ability of the anulus to resist forces delivered by compression of the disc and particularly the nucleus. A different network abundant in the disc and in other load-bearing tissues is based on the beaded filaments of collagen 6. The basic building block is a tetramer of two pairs of antiparallel collagen-6 molecules arranged such that two N-terminal ends of collagen 6 are exposed at either end of the unit. Further assembly occurs both by end-to-end and side-to-side associations. This process is catalyzed by both biglycan and decorin, where the combined effect of direct binding of the core protein to the collagen-6 N-terminal globular domain and the presence of the glycosaminoglycan side chain is essential. These ligands are bound at the same site in complexes extracted from the tissue and then also have one bound molecule of matrilin-1, 2, or 3, in turn bound to a collagen fiber, a procollagen molecule, or an aggrecan. Interactions at the cell surface provide signals to the cells with regard to the conditions of the matrix. Such interactions include binding by matrix components to various receptors at the cell surface. Remodeling of the matrix takes place in response to various factors. An early event in disease is degradation of aggrecan by the members of the ADAMTS (a disintegrin-like and metalloprotease with thrombospondin motifs) family and degradation of molecules important in maintaining the collagen network.
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| 34. |
- Franzén, Ahnders, et al.
(författare)
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Altered osteoclast development and function in osteopontin deficient mice.
- 2008
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Ingår i: Journal of Orthopaedic Research. - : Wiley. - 1554-527X .- 0736-0266. ; 26:5, s. 721-728
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Tidskriftsartikel (refereegranskat)abstract
- The role of osteopontin in bone resorption was elucidated by studies of mice with knock out of the osteopontin gene generated by a different approach compared to previous models. Thus, a targeting vector with the promoter region as well as exons 1, 2, and 3 of the osteopontin gene was replaced by a loxP-flanked Neo-TK cassette, and this cassette was eliminated through transient expression of Cre recombinase. The recombined ES cells were used to create mice lacking expression of the osteopontin gene. Tissues from these mice were subjected structural and molecular analyses including morphometry and proteomics. The bone of the null mice contained no osteopontin but showed no significant alterations with regard to other bone proteins. The bone volume was normal in young null animals but in the lower metaphysis, the volume and number of osteoclasts were increased. Notably, the volume and length of the osteoclast ruffled border was several folds lower, indicating a lower resorptive capacity. The null mice did not develop the bone loss characteristic for osteoporosis demonstrated in old wild-type female animals. This quantitative study demonstrates a bone phenotype in the osteopontin null mice of all ages. The data provides further evidence for a role of osteopontin in osteoclast activity. (c) 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.
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| 35. |
- Gawri, Rahul, et al.
(författare)
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Link N is Cleaved by Human Annulus Fibrosus Cells Generating a Fragment With Retained Biological Activity
- 2014
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Ingår i: Journal of Orthopaedic Research. - : Wiley. - 1554-527X .- 0736-0266. ; 32:9, s. 1189-1197
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Tidskriftsartikel (refereegranskat)abstract
- Presently, there are no established treatments to prevent, stop or even retard back pain arising from disc degeneration. Previous studies have shown that Link N can act as a growth factor and stimulate the synthesis of proteoglycans and collagens, in IVD. However, the sequences in Link N involved in modulating cellular activity are not well understood. To determine if disc cells can proteolytically process Link N, human disc cells were exposed to native Link N over a 48 h period and mass spectrometric analysis revealed that a peptide spanning residues 1-8 was generated in the presence of AF cells but not NP cells. Link N 1-8 significantly induced proteoglycan production in the presence of IL-1 beta NP and AF cells, confirming that the biological effect is maintained in the first 8 amino acids of the peptide and indicating that the effect is sustained in an inflammatory environment. Thus Link-N 1-8 could be a promising candidate for biologically induced disc repair, and the identification of such a stable specific peptide may facilitate the design of compounds to promote disc repair and provide alternatives to surgical intervention for early stage disc degeneration. (C) 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.
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| 36. |
- Geborek, Pierre, et al.
(författare)
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Measurement of synovial fluid volume using albumin dilution upon intraarticular saline injection
- 1988
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Ingår i: Journal of Rheumatology. - 0315-162X. ; 15:1, s. 91-94
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Tidskriftsartikel (refereegranskat)abstract
- A simple method for measuring synovial fluid (SF) volume is described. The degree of dilution of SF albumin after intraarticular injection of a defined volume of saline was used to calculate residual SF volume. Good correlation between calculated and aspirated SF volume was found for knee joint exudates. The method is simple, requires no radioactive tracer and should be useful in quantitative studies involving SF pathophysiology. Interestingly, the major portion of the SF could be directly aspirated, since residual volumes were small in comparison.
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| 37. |
- Goodman, SA, et al.
(författare)
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Tenocyte response to cyclical strain and transforming growth factor beta is dependent upon age and site of origin
- 2004
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Ingår i: Biorheology. - 0006-355X. ; 41:5, s. 613-628
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Tidskriftsartikel (refereegranskat)abstract
- The effect of strain and transforming growth factor beta on equine tendon fibroblasts (tenocytes) was assessed in vitro. Tenocytes were isolated from flexor and extensor tendons of horses from foetal to 10 years of age. These cells were cultured until confluent on collagen-coated silicone dishes. Cyclic biaxial strain of 9 +/- 1% was applied at 0.5 Hz for 24 hours with or without added TGFbeta1 or 3 (10 ng/ml). Proliferation and synthetic responses were dependent on the tendon of origin. Neither strain nor TGFbeta caused flexor tenocytes to proliferate significantly, while strain alone did proliferate extensor tenocytes. TGFbeta, with or without strain, increased the incorporation of [H-3]-proline and the production of types I and III collagen and COMP in both cell types, although the effect on COMP production was more marked in flexor tenocytes, perhaps reflecting the higher levels found in this tendon in vivo. Immature flexor tenocytes synthesised more collagen and COMP than those from mature animals. while age had little effect in extensor tenocytes. Our results suggest that tenocytes become differentiated at an early age and present tendon-specific responses.
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| 38. |
- Guo, Yongzhi, 1972-
(författare)
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Plasmin : a potent pro-inflammatory factor
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Plasmin, the central molecule of the plasminogen activator system, is a broad-spectrum serine protease. Plasmin is important for the degradation of fibrin and other components of the extracellular matrix (ECM) during a number of physiological and pathological processes. The aim of this thesis was to elucidate the functional roles of plasmin during pathological inflammation and infection in autoimmune and non-autoimmune diseases. For this purpose, mouse models of rheumatoid arthritis (RA), bacterial arthritis, infection, and sepsis have been used. Previous studies from our laboratory have shown that plasminogen-deficient mice are resistant to the development of collagen type II-induced arthritis (CIA). In contrast, others have shown that plasmin plays a protective role in antigen-induced arthritis (AIA). To investigate the contrasting roles of plasminogen deficiency in models of CIA and AIA, a new animal model of arthritis called local injection-induced arthritis (LIA) was developed. In this model, we replaced methylated bovine serum albumin, which is normally used as an immunogen in the AIA model, with collagen type II (CII) to induce arthritis. When wild-type and plasminogen-deficient mice were injected intra-articularly with CII or 0.9% NaCl following CIA induction, plasminogen-deficient mice developed typical CIA, but the disease was less severe than in wild-type mice and was restricted to the injected joints. When the AIA model was used, plasminogen-deficient mice developed a much more severe arthritis than the wild-type mice. These results indicate that both the antigen and joint trauma caused by the local injection are critical to explaining the contrasting roles of plasminogen deficiency in CIA and AIA. This indicates that CIA and AIA have distinct pathogenic mechanisms and plasmin plays contrasting roles in different types of arthritis models. To study the functional roles of plasmin in the host inflammatory response during infectious arthritis, a Staphylococcus aureus-induced bacterial arthritis model was established. When wild-type mice were injected intra-articularly with 1 × 106 colony-forming units (CFU) of S. aureus per joint, all the bacteria were completely eliminated from the injected joints in 28 days. However, in the plasminogen-deficient mice, the S. aureus counts were 27-fold higher at day 28 than at day 0. When human plasminogen was given to the plasminogen-deficient mice daily for 7 days, the bacterial clearance was greatly improved and the necrotic tissue in the joint cavity was also completely eliminated. Supplementation of plasminogen-deficient mice with plasminogen also restored the expression level of interleukin-6 (IL-6) in the arthritic joints. In summary, plasmin has protective roles during S. aureus-induced arthritis by enhancing cytokine expression, removing necrotic tissue, and mediating bacterial killing and inflammatory cell activation. The functional roles of plasmin during infection and sepsis were also studied in mice. Infection was induced by injecting 1 × 107 CFU of S. aureus intravenously and the sepsis model was induced by injecting 1.6 × 108 CFU of S. aureus. In the infection model, the wild-type mice had a 25-day survival rate of 86.7%, as compared to 50% in the plasminogen-deficient group. However, when sepsis was induced, the average survival for plasminogen-deficient mice was 3 days longer than for wild-type mice. Twenty-four hours after the induction of sepsis, the serum levels of IL-6 and IL-10 as well as the bacterial counts in all organs investigated were significantly higher in wild-type mice than in plasminogen-deficient mice. In wild-type mice, blockade of IL-6 by intravenous injection of anti-IL-6 antibodies significantly prolonged the onset of mortality and improved the survival rate during sepsis. These data indicate that plasmin plays different roles during infection and sepsis. Furthermore, plasmin appears to be involved in the regulation of inflammatory cytokine expression during sepsis. Taken together, our data indicate that plasmin plays multifunctional pro-inflammatory roles in different autoimmune and non-autoimmune diseases. The pro-inflammatory roles of plasmin include activation of inflammatory cells, regulation of cytokine expression, and enhancement of the bacterial killing ability of the host.
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| 39. |
- Haglund, Lisbet, et al.
(författare)
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Identification and Characterization of the Integrin alpha(2)beta(1) Binding Motif in Chondroadherin Mediating Cell Attachment
- 2011
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 286:5, s. 3925-3934
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Tidskriftsartikel (refereegranskat)abstract
- Chondroadherin is a leucine-rich repeat protein known to mediate adhesion of isolated cells via the integrin alpha(2)beta(1) and to interact with collagen. In this work, we show that cell adhesion to chondroadherin leads to activation of MAPKs but does not result in cell spreading and division. This is in contrast to the spreading and dividing of cells grown on collagen, although the binding is mediated via the same alpha(2)beta(1) receptor. We identified a cell binding motif, CQLRGLRRWLEAK(318) by mass spectrometry after protease digestion of chondroadherin. Cells adhering to the synthetic peptide CQLRGLRRWLEAK(318) remained round, as was observed when they bound to the intact protein. The peptide added in solution was able to inhibit cell adhesion to the intact protein in a dose-dependent manner and was also verified to bind to the alpha(2)beta(1) integrin. A cyclic peptide, CQLRGLRRWLEAKASRPDATC(326), mimicking the structural constraints of this sequence in the intact protein, showed similar efficiency in inhibiting binding to chondroadherin. The unique peptide motif responsible for cellular binding is primarily located in the octamer sequence LRRWLEAK(318). Binding of cells to the active peptide or to chondroadherin immobilized on cell culture plates rapidly induces intracellular signaling (i.e. ERK phosphorylation). Thus, chondroadherin interaction with cells may be central for maintaining the adult chondrocyte phenotype and cartilage homeostasis. The peptides, particularly the more stable cyclic peptide, open new opportunities to modulate cell behavior in situations of tissue pathology.
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| 40. |
- Haglund, Lisbet, et al.
(författare)
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The C-terminal Peptide of Chondroadherin Modulates Cellular Activity by Selectively Binding to Heparan Sulfate Chains
- 2013
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 288:2, s. 995-1008
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Tidskriftsartikel (refereegranskat)abstract
- Chondroadherin, a leucine-rich repeat family member, contains a very C-terminal sequence CKFPTKRSKKAGRH(359), now shown to bind to heparin with a K-D of 13 mu M. This observation led us to investigate whether chondroadherin interacts via this C-terminal heparin-binding domain with glycosaminoglycan chains of proteoglycans at the cell surface. Cells were shown to bind this heparin-binding peptide in FACS analysis, and the interaction was shown to be with glycosaminoglycans because it was abolished when sulfation was inhibited by chlorate treatment of the cells. In separate experiments, heparin and heparan sulfate inhibited the peptide interaction in a dose-dependent manner. Using a human chondrosarcoma and a murine osteoblast cell line, heparan sulfate proteoglycans were identified as the cell surface receptors involved in the binding. Different binding syndecans were identified in the two different cell lines, indicating that the same protein core of a proteoglycan may have structural and functional differences in the attached heparan sulfate chains. Upon binding to coated peptide, cells spread, demonstrating engagement of the cytoskeleton, but no focal adhesion complex was formed. The number of cells adhering via their beta(1) integrin receptor to collagen type II or chondroadherin was profoundly and rapidly enhanced by the addition of the heparin-binding peptide. The peptide added to the cells caused ERK phosphorylation, showing that it triggered intracellular signaling. The results show that heparan sulfate chains differ between various members of the proteoglycan families on a given cell, but also differ between the same proteoglycan on different cells with a potential for differential regulation of cellular activities.
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