Matrix metalloproteinases 2 and 9 in equine synovial fluids

A Translational Model for Repeated Episodes of Joint Inflammation: Welfare, Clinical and Synovial Fluid Biomarker Assessment

This study investigates repeated low-dose lipopolysaccharide (LPS) injections in equine joints as a model for recurrent joint inflammation and its impact on animal welfare. Joint inflammation was induced in eight horses by injecting 0.25 ng of LPS three times at two-week intervals. Welfare scores and clinical parameters were recorded at baseline and over 168 h post-injection. Serial synoviocentesis was performed for the analysis of a panel of synovial fluid biomarkers of inflammation and cartilage turnover. Clinical parameters and a final synoviocentesis were also performed eight weeks after the last sampling point to assess the recovery of normal joint homeostasis. Statistical methods were used to compare the magnitude of response to each of the 3 LPS inductions and to compare the baseline and final measurements. Each LPS injection produced consistent clinical and biomarker responses, with minimal changes in welfare scores. General matrix metalloproteinase (MMP) activity and joint circumference showed greater response to the second LPS induction, but response to the third was comparable to the first. Gylcosaminoglycans (GAG) levels showed a significantly decreased response with each induction, while collagen-cleavage neoepitope of type II collagen (C2C) and carboxypropetide of type II collagen epitope (CPII) showed quicker responses to the second and third inductions. All parameters were comparable to baseline values at the final timepoint. In conclusion, a consistent, reliable intra-articular inflammatory response can be achieved with repeated injections of 0.25 ng LPS, with minimal impact on animal welfare, suggesting potential as a refined translational model of recurrent joint inflammation.

Lymphocyte immunophenotyping and concentration of MMP-9 in transudates and exudates in horses

This study is the first to provide information on the lymphocyte subpopulations in peritoneal effusions in horses. Peritoneal transudates (n = 12), peritoneal exudates (n = 6) and a pleural exudate (n = 1) were analyzed. The total nucleated cell count (TNCC), total protein (TP) and matrix metalloproteinase-9 (MMP-9) concentration determined by ELISA were measured and routine cytological evaluation was performed. CD3, CD4, CD8 and CD21 positive cells were detected by flow cytometry. A higher percentage of neutrophils (P < 0.05) and higher MMP-9 (P < 0.01) levels were found in exudates. A higher percentage of macrophages (P < 0.05) and lymphocytes (P < 0.01) were found in transudates. CD4 + lymphocytes were the most common lymphocyte subpopulation in all samples. CD21 + lymphocytes were the least common in all samples. A large variability in the percentage of CD21 + lymphocytes was found in exudates. The percentage of CD21 + lymphocytes positively correlated with the level of total protein (r = 0.5704, P < 0.05). The correlation was even stronger in the group of exudates. The percentages of lymphocyte subpopulations did not correlate with the level of MMP-9 or with cytological findings. The level of MMP-9 positively correlated with the percentage of neutrophils (r = 0.4980, P < 0.05), the level of TP (r = 0.7855, P < 0.01) and TNCC (r = 0.6129, P < 0.01). A significantly higher level of MMP-9 was detected in euthanized horses than in horses that survived (P < 0.05). However, it was shown that the level of MMP-9 in the peritoneal fluid can change significantly in a short time. More studies on repeated abdominocentesis could contribute to elucidating the role of MMP-9 as a prognostic indicator.

Alterations of peripheral gene expression in response to lipopolysaccharide-induced synovitis as a model for inflammation in horses

While the use of lipopolysaccharide (LPS) to induce inflammation has been well described in the horse, the object of this study was to evaluate the effect of repeated intra-articular LPS injections and determine whether this method may be of use to assess changes in gene expression related to inflammation. Six mixed breed horses were utilized for this study, with three horses aged 10-17 years (older group) and three horses aged 3 years (younger group). One milliliter of phosphate-buffered saline containing 3 μg of LPS from Escherichia coli O111:B4 was aseptically injected into either the radiocarpal or front fetlock joint a total of four times, with at least two weeks between each injection and a different joint injected each time. Serum for protein concentration quantification and whole blood for expression analysis of 20 different genes were collected before each injection, as well as at multiple times post-injection. Statistical analysis was performed using analysis of variance (one-way and two-way) (P < 0.05). All horses experienced minimal or non-weight bearing lameness at 4-6 hours post-LPS injection, which generally improved by 24 h and resolved by 48 h. Multiple genes exhibited significantly differential expression when compared to both the pre-injection and sham injection time points, including CD14, TLR4, MMP1, MMP9, IL-1β, IL1RN, IL-10, ALOX5AP, IL-8, TNFα, CCL8, IGF1, and PTGS2. Additionally, multiple genes exhibited increased expression in horses where the radiocarpal joint was injected when compared to the fetlock joint, as well as in younger horses compared to older horses. Serum concentrations of serum amyloid A (SAA) were negative prior to injection while all horses demonstrated an increase by 9 h post-injection, which often remained until at least 144 h. Attempts to measure in vivo serum cytokine levels using a multiplex assay were not successful and believed to be due to the lower limits of detection for the assays. The measurement of mRNA expression of pro- and anti-inflammatory genes provide sensitive and rapid information regarding the inflammatory response to an acute, localized stimulus, although care must be taken when selecting target joints or age groups of horses as the transcriptional response may vary based on these choices.

COL2A1 and Caspase-3 as Promising Biomarkers for Osteoarthritis Prognosis in an Equus asinus Model

Osteoarthritis (OA) is one of the most degenerative joint diseases in both human and veterinary medicine. The objective of the present study was the early diagnosis of OA in donkeys using a reliable grading of the disease based on clinical, chemical, and molecular alterations. OA was induced by intra-articular injection of 25 mg monoiodoacetate (MIA) as a single dose into the left radiocarpal joint of nine donkeys. Animals were clinically evaluated through the assessment of lameness score, radiographic, and ultrasonographic findings for seven months. Synovial fluid and cartilage samples were collected from both normal and diseased joints for the assessment of matrix metalloproteinases (MMPs) activity, COL2A1 protein expression level, and histopathological and immunohistochemical analysis of Caspase-3. Animals showed the highest lameness score post-induction after one week then decreased gradually with the progression of radiographical and ultrasonographic changes. MMP activity and COL2A1 and Caspase-3 expression increased, accompanied by articular cartilage degeneration and loss of proteoglycan. OA was successfully graded in Egyptian donkeys, with the promising use of COL2A1and Caspase-3 for prognosis. However, MMPs failed to discriminate between early and late grades of OA.

Gene expression of matrix metalloproteinase 9 (MMP9), matrix metalloproteinase 13 (MMP13), vascular endothelial growth factor (VEGF) and fibroblast growth factor 23 (FGF23) in femur and vertebra tissues of the hypovitaminosis D kyphotic pig model

The hypovitaminosis D kyphotic pig provides a reliable model to study the initiation of bone lesions caused by maternal vitamin D (D) deficiencies. Matrix metalloproteinases (MMP; specifically, MMP9 and MMP13) and vascular endothelial growth factor (VEGF) are important in endochondral ossification and are potentially regulated by D. Fibroblast growth factor 23 (FGF23) is interrelated with D homoeostasis and bone mineralisation. Relative mRNA expression of MMP9, MMP13, VEGF and FGF23 was measured in pig femur and vertebra. Sows (n 37) were fed diets with 0 (-D), 8·125 (+D) or 43·750 (++D) µg D3/kg throughout gestation and lactation. At weaning (3 weeks), pigs were fed diets with 0 (-D) or 7·0 (+D) µg D3/kg, each with 75 and 95 % (LCaP) or 150 and 120 % (HCaP) of the Ca and P requirements. Pigs at birth (n 27), 3 weeks (n 27) and after the nursery period (7 weeks; n 72) were euthanised for analysis. At 3 weeks, femur MMP9 expression of pigs produced by +D or ++D sows was reduced (P<0·05) to 0·5-fold and VEGF expression to 0·4-fold compared with pigs from -D sows. At 7 weeks, MMP9 expression was reduced (P<0·05) to 0·45-fold in femur and 0·58-fold in vertebra from pigs produced by +D or ++D sows compared with pigs from -D sows. Pig femur VEGF expression was reduced to 0·75-fold in pigs produced by ++D sows. MMP9 and VEGF mRNA expression offer potential markers for the initiation of bone lesions in the hypovitaminosis D kyphotic pig model.

Changes in Synovial Fluid Biomarkers after Experimental Equine Osteoarthritis

Introduction

The study aimed to clarify the changes in the concentration of inflammatory mediators, proteases, and cartilage degradation biomarkers in the synovial fluid of joints in an equine osteoarthritis model.

Material and Methods

Osteoarthritis was induced in eight Mongolian horses by a sterile intra-articular injection of amphotericin B, which was injected into the left carpal joint in a dose of 2 mL (25 mg/mL). The control group comprised five horses which were injected with an equal dose of sterile physiological saline into the left carpal joint. Synovial fluid was obtained at baseline and every week after injection. Test methods were based on ELISA.

Results

In the course of the osteoarthritis, the concentration of biomarkers in joint synovial fluid showed an increasing trend. IL-1, IL-6, MMP-9, MMP-13, ADAMTS-5, CS846, GAG, HA, CTX-II, and COMP concentrations sharply increased before the onset of significant symptoms of lameness, whereas TNF-α, MMP-2, and MMP-3 concentrations rose sharply after the occurrence of such symptoms.

Conclusion

The results obtained confirm that the concentrations of IL-1, IL-6, MMP-9, MMP-13, ADAMTS-5, CS846, GAG, HA, CTX-II and COMP increase substantially in equine osteoarthritis, which provides a theoretical basis for the rapid diagnosis of the disease.

Effect of arthroscopic lavage and repeated intra-articular administrations of antibiotic in adult horses and foals with septic arthritis

OBJECTIVE

To evaluate the effect of arthroscopic lavage and repeated intra-articular administration of antibiotic in adult horses and foals with septic arthritis.

STUDY DESIGN

Retrospective clinical study.

ANIMALS

Adult horses and foals with septic arthritis (n = 62).

METHODS

Age, sex, cause of septic synovitis, joint involved, hospitalization time, and outcome were recorded. Arthroscopic lavage was performed at day 0 (D 0). Synovial fluid was collected every 48 hours prior to intra-articular administration of antibiotic, and until hospital discharge. Synovial nucleated cell count, total protein, and percentage of neutrophils were compared across time and between subjects with a favorable or unfavorable outcome.

RESULTS

Synovial nucleated cell counts decreased progressively and were lower at all times compared to D 0. Percentages of neutrophils were lower than baseline at D 8 and 10, only. Total protein contents decreased progressively and were lower than baseline at D 2, 4, 6, 8, 10, and 14. When adult horses and foals with a favorable outcome were compared to those with an unfavorable outcome, the nucleated cell count was lower at D 10, 12, and 14 and the percentage of neutrophils was lower at D 4 only, but total protein content did not differ between groups at any time.

CONCLUSION

Synovial nucleated cell counts and total protein concentrations decreased after arthroscopic lavage and repeated intra-articular administration of antibiotic in horses and foals with septic arthritis. Synovial nucleated cell count is limited as a monitoring tool during treatment of septic arthritis.

Chondroprotective and anti-inflammatory effects of S-methylisothiourea, an inducible nitric oxide synthase inhibitor in cartilage and synovial explants model of osteoarthritis

Objectives

To study the chondroprotective and anti-inflammatory potential of inducible nitric oxide synthase (iNOS) inhibitor S-methylisothiourea (SMT) in in-vitro model.

Methods

Rabbit cartilage explants were stimulated with recombinant human interleukin 1β (rhIL-1β), and the chondroprotective and anti-inflammatory effects of SMT were investigated. Rat synovial explants were stimulated with LPS, and the anti-inflammatory effect of SMT on synovium was studied. To examine the role of SMT in synovial inflammation mediated cartilage damage, LPS stimulated synovial explants were cultured with dead cartilage with or without SMT for 72 h. The culture medium was analysed for sulfated glycosaminoglycans (GAGs) and hydroxyproline as measure of proteoglycans and collagen degradation, respectively.

Key findings

SMT significantly reduced GAGs, hydroxyproline, matrix metalloproteinase (MMP)-13, tumour necrosis factor alpha (TNF-α), prostaglindin E2 (PGE2) and nitrite release in stimulated rabbit cartilage media indicating chondroprotective and anti-inflammatory effects of SMT in osteoarthritis (OA). Stimulated synovial explants caused release of nitrite, PGE2, IL-1β and TNF-α in the medium which were significantly reduced by SMT indicating its anti-inflammatory action. SMT significantly reduced GAGs and hydroxyproline in medium and shown protective effect against synovium-mediated cartilage damage.

Conclusions

SMT inhibited cartilage degradation, synovial inflammation and synovium-mediated cartilage damage, suggesting that SMT may be an agent for pharmacological intervention in OA.

Plasma matrix metalloproteinase activity in horses after intravenous infusion of lipopolysaccharide and treatment with matrix metalloproteinase inhibitors

OBJECTIVE

To establish an in vivo method for matrix metalloproteinase (MMP)-2 and MMP-9 induction in horses via IV administration of lipopolysaccharide (LPS) and to evaluate the ability of doxycycline, oxytetracycline, flunixin meglumine, and pentoxifylline to inhibit equine MMP-2 and MMP-9 production.

ANIMALS

29 adult horses of various ages and breeds and either sex.

PROCEDURES

In part 1, horses received an IV administration of LPS (n = 5) or saline (0.9% NaCl) solution (5). Venous blood samples were collected before and at specified times for 24 hours after infusion. Plasma was harvested and analyzed for MMP-2 and MMP-9 activities via zymography. In part 2, horses received doxycycline (n = 5), oxytetracycline (5), flunixin meglumine (5), or pentoxifylline (4) before and for up to 12 hours after administration of LPS. Plasma was obtained and analyzed, and results were compared with results from the LPS-infused horses of part 1.

RESULTS

Administration of LPS significantly increased MMP-2 and MMP-9 activities in the venous circulation of horses. All MMP inhibitors significantly decreased LPS-induced increases in MMP activities but to differing degrees. Pentoxifylline and oxytetracycline appeared to be the most effective MMP-2 and MMP-9 inhibitors, whereas doxycycline and flunixin meglumine were more effective at inhibiting MMP-2 activity than MMP-9 activity.

CONCLUSIONS AND CLINICAL RELEVANCE

IV administration of LPS to horses caused increased venous plasma activities of MMP-2 and MMP-9. These MMP activities were reduced by pentoxifylline and oxytetracycline, suggesting that further evaluation of these medications for treatment and prevention of MMP-associated diseases in horses is indicated.

The horse as a model of naturally occurring osteoarthritis

Osteoarthritis (OA) is an important cause of pain, disability and economic loss in humans, and is similarly important in the horse. Recent knowledge on post-traumatic OA has suggested opportunities for early intervention, but it is difficult to identify the appropriate time of these interventions. The horse provides two useful mechanisms to answer these questions: 1) extensive experience with clinical OA in horses; and 2) use of a consistently predictable model of OA that can help study early pathobiological events, define targets for therapeutic intervention and then test these putative therapies. This paper summarises the syndromes of clinical OA in horses including pathogenesis, diagnosis and treatment, and details controlled studies of various treatment options using an equine model of clinical OA.

Canine hip dysplasia: reviewing the evidence for nonsurgical management

OBJECTIVE

To systematically review the evidence available for nonsurgical management of hip dysplasia (HD).

STUDY DESIGN

Literature review.

METHODS

Databases (Pubmed, Veterinary Information Network) were searched for clinical studies on nonsurgical management of HD in dogs. The evidence in each study was reviewed and assigned a score (I-IV) based on previously reported levels of evidence.

RESULTS

Fourteen articles were identified that met the inclusion criteria, including 3 Level IV, 4 Level III, and 7 Level II studies. Methods of nonsurgical management reviewed included: activity restrictions, weight management, acupuncture, modulation of joint disease by polysulfated glycosaminoglycans, mesenchymal stem cell therapy, and extra corporeal shock wave therapy.

CONCLUSION

Weight management is an effective and important component of managing dogs with HD and associated osteoarthritis. Techniques that modulate the progression of joint disease may also be beneficial for treating dogs with HD. Further studies are needed to investigate other methods of managing HD such as hydrotherapy and physical rehabilitation.

Hypoxia and a hypoxia mimetic up-regulate matrix metalloproteinase 2 and 9 in equine laminar keratinocytes

The aim of this study was to determine if hypoxia and the hypoxia mimetic cobalt chloride regulate the activity of matrix metalloproteinase (MMP)-2 and -9 in cultures of equine hoof keratinocytes. These effects were assessed in primary cultures of laminar keratinocytes using gelatin zymography. Incubation of keratinocytes with cobalt chloride significantly increased the levels of active MMP-2 compared to untreated controls. Hypoxia significantly increased the expression of active MMP-2 and -9 in keratinocyte cultures. This up-regulation was observed after 6h and peaked at 24h. The study findings provide novel evidence of a potential link between hypoxia within the hoof and up-regulation of MMPs which may in turn result in damage to the lamellar basement membrane.

Age-related differences in prostaglandin E2 synthesis by equine cartilage explants and synoviocytes

Time- and concentration-related actions of lipopolysaccharide (LPS) on the synthesis of prostaglandin E(2) (PGE(2)) were investigated in cartilage explants and synoviocytes harvested from 3 age groups of horses, all with clinically normal joint function: group A <10 years; group B 11-20 years and group C >20 years. Cartilage explants from group A horses were least and those from group C were most sensitive to LPS. Significant increases in PGE(2) concentration (P <or= 0.01) were obtained in group C horses in response to LPS concentrations of 1.0 microg/mL (and higher) after exposure for 24, 36 and 48 h, whereas explants from group A horses failed to respond to LPS at concentrations up to 100 microg/mL after exposure times up to 48 h. In contrast, synoviocytes from group A horses were most and those from group C horses were least sensitive to LPS stimulation. Synoviocytes from group A horses responded to LPS concentrations of 1 microg/mL (and higher) with significantly increased concentrations of PGE(2) at 24 and 36 h. Significant but numerically smaller increases in PGE(2) concentration were induced by LPS in synoviocytes from groups B and C. As the effects of high PGE(2) concentrations are catabolic for cartilage, these observations suggest that both synoviocytes and chondrocytes might exert roles in the degenerative changes which occur in cartilage in horses with osteoarthritis.

Comparative study of the properties of tendinocytes derived from three different sites in the equine superficial digital flexor tendon

This aim of this study was to determine the characteristic differences in tendinocytes derived from three sites of the equine superficial digital flexor tendon (SDFT)-proximally the myotendinous junction (MTJ), mid-metacarpal (mM) and osteotendinous junction (OTJ)-in morphology, proliferation, and ability for synthesis of collagen and matrix metalloproteinases (MMPs). Little difference was observed in cell proliferation. Addition of tumor necrosis factor (TNF) alpha to the culture medium resulted in increased collagen synthesis by tendinocytes from all three sites. The amount of collagen synthesized by tendinocytes derived from the mM and OTJ was much larger than that synthesized by untreated tendinocytes. A collagen zymogram revealed that proMMP-13 synthesis was increased towards the distal site. However, TNFalpha treatment resulted in a significant decrease in the amount of proMMP-13 synthesized by tendinocytes from all three sites. On the other hand, a gelatin zymogram showed that the synthesis level of proMMP-9 tended to decrease towards the distal site, but there was little difference between synthesis levels of proMMP-9 before and after TNFalpha treatment. These results indicated that tendinocytes in the same tendon have different characteristics and that these characterisities would reflect the function of tendinocytes in vivo. Also, the isolated tendinocytes provided much information on the characteristics and properties of tendons for the ECM turnover system and on the responsiveness of tendinocytes to complex inflammatory responses in a tendinopathy condition.

The influence of repeated arthrocentesis and exercise on matrix metalloproteinase and tumour necrosis factor a activities in normal equine joints

REASONS FOR PERFORMING STUDY

Matrix metalloproteinases (MMPs) and tumour necrosis factor alpha (TNF-alpha) may be useful as biomarkers of joint disease or inflammation. However, activity of both MMPs and TNF-alpha in synovial fluid (SF) may be influenced by nonpathological factors such as arthrocentesis or exercise.

OBJECTIVE

To investigate the influence of repeated arthrocentesis and exercise on MMP and TNF-alpha activities in SF from normal equine joints.

METHODS

SF was collected from the left metacarpophalangeal, radiocarpal and tarsocrural joints of 16 horses. Eight of these horses were subsequently subjected to an exercise programme on a treadmill and 8 were box-rested as controls. Arthrocentesis was repeated 14, 145, 17 and 24 days after the start of the exercise programme. General MMP and TNF-alpha activities were determined in SF.

RESULTS

Repeated arthrocentesis caused a gradual increase but the exercise regimen no significant increase in MMP activity. There was a significant increase in TNF-alpha activity in SF collected from horses 2 h after cessation of the exercise programme.

CONCLUSIONS AND POTENTIAL RELEVANCE

When using MMPs as biomarkers for joint disease, at least 14 days should elapse after previous arthrocentesis before subsequent SF collection. Moderate exercise does not increase MMP activity in SF from normal joints and it may be possible to ignore this as a source of error in evaluating MMP activity in diseased joints.

Relationship between synovial fluid levels of glycosaminoglycans, hydroxyproline and general MMP activity and the presence and severity of articular cartilage change on the proximal articular surface of P1

REASONS FOR PERFORMING STUDY

Osteoarthritis (OA) is one of the most prevalent and disabling chronic conditions affecting horses and leads to degeneration of articular cartilage. Diagnosis is based on clinical signs in combination with radiography, which is relatively insensitive and provides only an indication of accumulated damage. Alternative methods, such as molecular markers, are therefore needed that can quantitatively, reliably and sensitively detect osteoarthritic changes in the joints at an early stage of the disease. If such markers are to be used reliably, it is important to know the relationship between marker concentration and cartilage composition.

OBJECTIVES

To study the relationship between cartilage composition, synovial fluid levels of glycosaminoglycans (GAGs), hydroxyproline (Hyp) and general matrix metalloproteinase (MMP) activity, and the presence and severity of articular cartilage damage on the articular surface of P1.

METHODS

Synovial fluid (SF) was collected from the metacarpophalangeal joints of 60 mature horses, and levels of GAGs, Hyp and general MMP activity were determined. Further, GAG and denatured collagen content of the articular cartilage were determined at the dorsal articular margin of P1 (site 1) and central cavity (site 2). The presence and severity of cartilage change was quantified using the cartilage degeneration index (CDI), measured at the same 2 sites. Correlations between SF parameters, cartilage composition and degree of cartilage degeneration were sought using correlation analysis.

RESULTS

There was no correlation between GAG or Hyp content of SF and the amount of GAGs or denatured collagen, respectively, in cartilage. In joints with moderate to severe cartilage damage, the GAG content of site 1 was significantly lower than in joints with no to minimal cartilage change (P = 0.005) and there was a negative correlation between the amount of denatured collagen and GAG content at site 1 in all joints (r = -039, P = 0.002). Further, in joints with moderate to severe cartilage damage, there was a significant positive correlation between MMP activity in SF and Hyp levels in SF (r = 0.72, P < 0.001) and CDI at sites 1 (r = 0.46, P = 0.03) and 2 (r = 0.43, P = 0.04).

CONCLUSIONS

General MMP activity in joints with moderate to severe cartilage damage is related to the severity of those cartilage changes and to Hyp levels in SF. Glycosaminoglycan levels in SF are not directly related to MMP activity, GAG content of articular cartilage or severity of cartilage change.

POTENTIAL RELEVANCE

Glycosaminoglycan levels in SF are not helpful for the early detection of cartilage lesions. In damaged joints, Hyp levels may give an indication of the severity of cartilage change as they are strongly related to MMP activity, but do not qualify as markers for the presence or absence of cartilage lesions.

Collagenase-1 (MMP-1) activity in equine synovial fluid: influence of age, joint pathology, exercise and repeated arthrocentesis

REASONS FOR PERFORMING STUDY

Matrix metalloproteinases (MMPs) are considered candidate biomarkers for both physiological and pathological tissue remodelling because of their key role in articular cartilage homeostasis. As disruption of the collagenous architecture is thought to be pivotal in chronic degenerative diseases such as osteoarthritis (OA), the collagenases form an interesting subset of the MMPs. The significance of any biomarker in synovial fluid (SF) can be assessed properly only when fluctuations in patterns induced by physiological processes such as development and growth, and by external influences and interventions such as exercise and repeated arthrocentesis, are known and taken into account.

OBJECTIVES

To investigate the activity of MMP-1 in equine SF at different stages of development and in joints affected by OA, and the influence of exercise and repeated arthrocentesis thereon.

METHODS

MMP-1 activity was determined in SF of normal joints of fetal, juvenile and mature horses, and in SF of horses suffering from OA, using an internally quenched fluorogenic peptide substrate. MMP-1 activity was also measured in SF from horses subjected to an exercise regimen and those subjected to repeated arthrocentesis.

RESULTS

An age-related decline in the SF levels of active MMP-1 was observed. MMP-1 activity was 15-fold higher in fetal than in juvenile animals, which showed significantly higher MMP-1 activity levels than mature horses. In SF of OA joints, MMP-1 activity was increased. Exercise did not affect MMP-1 activity in SF, but repeated arthrocentesis (within 60 h) increased MMP-1 activity significantly.

CONCLUSIONS

The high MMP-1 activity in SF of young individuals parallels the high metabolic activity occurring during rapid growth and differentiation at early age. The elevated MMP-1 activity in SF of OA joints probably reflects pathological matrix degradation, confirming the potential of MMP-1 to serve as a biochemical marker for early joint disease. Moderate exercise is not likely to influence the outcome of MMP-1 activity measurements in equine SF, but arthrocentesis should be taken into account as a possible confounding factor.

POTENTIAL RELEVANCE

Given the crucial role of the collagen matrix for tissue integrity, MMP-1 activity may be a useful tool in diagnostic, therapeutic or prognostic studies in horses suspected of OA. However, care should be taken to exclude fluctuations in MMP-1 activity induced by physiological processes such as development and growth, and by interventions such as repeated arthrocentesis.

The contribution of the synovium, synovial derived inflammatory cytokines and neuropeptides to the pathogenesis of osteoarthritis

Osteoarthritis (OA) is one of the most common and disabling chronic joint disorders affecting horses, dogs and humans. Synovial inflammation or synovitis is a frequently observed phenomenon in osteoarthritic joints and contributes to the pathogenesis of OA through formation of various catabolic and pro-inflammatory mediators altering the balance of cartilage matrix degradation and repair. Catabolic mediators produced by the inflamed synovium include pro-inflammatory cytokines, nitric oxide, prostaglandin E(2) and several neuropeptides, which further contribute to the pathogenesis of OA by increasing cartilage degradation. Recent studies suggest that substance P, corticotropin-releasing factor, urocortin and vasoactive intestinal peptide may also be involved in OA development, but the precise role of these neuropeptides in the pathogenesis of OA is not known. Since increased production of matrix metalloproteinases by the synovium is stimulated by pro-inflammatory cytokines, future anti-inflammatory therapies should focus on the synovium as a means of controlling subsequent inflammatory damage.

Matrix metalloproteinases in inflammatory pathologies of the horse

The extracellular matrix (ECM) of connective tissue is constantly being remodelled to allow for growth and regeneration. Normal tissue maintenance requires the ECM components to be degraded and re-synthesised in relatively equal proportions. This degradation is facilitated by matrix metalloproteinases (MMPs) and their proteolytic action is controlled primarily by the tissue inhibitors of metalloproteinases (TIMPs). Both MMPs and TIMPs exist in a state of dynamic equilibrium, with a slight excess of one or the other depending on the need for either ECM breakdown or synthesis. Long-term disruption to this balance between MMPs and TIMPs will have pathological consequences. Matrix metalloproteinases are involved in a number of diseases in mammals, including the horse. Excess MMP activity can cause ECM destruction, as seen in the lamellar basement membrane in laminitis and the articular cartilage in osteoarthritis. Matrix metalloproteinase under-activity can potentially impede healing by preventing fibrinolysis in fibrotic conditions and the removal of scar tissue in wounds. Matrix metalloproteinases also degrade non-ECM proteins and regulate cell behaviour via the release of growth factors from the substrates they cleave, increasing the scope of their effects. This review looks at the involvement of MMPs in equine health and pathologies, whilst exploring the potential consequences of therapeutic intervention.

High-intensity exercise induces structural, compositional and metabolic changes in cuboidal bones--findings from an equine athlete model

Fatigue fracture of cuboidal bones occurs in the human foot as well as the equine carpus. The racehorse provides a naturally-occurring model to study the effects of high-intensity exercise on the morphology and metabolism of cuboidal bones. We studied both the mineral and the collagenous matrix of the third (C(3)) and radial (C(r)) carpal bones of raced and non-raced Thoroughbred (TB) horses. We hypothesised that racehorses would show increases in the mineral component of these bones and post-translational modifications of the collagenous matrix alongside changes in markers of collagen remodelling and bone formation. C(3) and C(r) carpal bones were retrieved from raced TB horses (n=14) and non-raced TB horses (n=11). Standardised proximal-distal sections were taken from each bone and these were sliced transversely to study the proximal-distal differences in bone metabolism from the subchondral plate through to trabecular bone. Histomorphometry and bone mineral density measurements were performed in parallel with biochemical analyses including total collagen, collagen synthesis and cross-links, matrix metalloproteinases-2 and 9 and their inhibitors, calcium and phosphate, and bone alkaline phosphatase. The results of this study show that, while there is a net increase in bone formation in the racehorses, there is additionally an increase in bone collagen synthesis and remodelling, particularly within the trabecular regions of the bone. The increase in bone density would lead to greater stiffness, particularly in the cortical bone, and failure of this 'stiffer' cortical bone may result from its lack of support from the rapidly remodelling and structurally weakened underlying trabecular bone.

Determination of MMP-2 and -9 activities in synovial fluid of horses with osteoarthritic and arthritic joint diseases using gelatin zymography and immunocapture activity assays

REASON FOR PERFORMING STUDY

Matrix metalloproteinases (MMPs)-2 and -9 activities have been found elevated in synovial fluid from various joint diseases in man. However, in the horse few data are available.

OBJECTIVES

To explore the clinical significance of MMP-2 and -9 activities in synovial fluid of horses with different forms of joint diseases.

METHODS

Gelatin zymography and MMP-2 and -9 immunocapture activity assays were applied on synovial fluids from control joints and joints with aseptic joint disease (AJD) and septic arthritis (SA). Additionally, MMP-2 and -9 activities were measured in samples from SA to monitor the disease process.

RESULTS

Zymographic analysis revealed that samples from AJD and SA contained significantly increased latent MMP-2 activity compared to controls. Samples from SA showed significantly increased monomeric latent MMP-9 activity compared with all other affected joints and controls. Trace amounts of MMP-9 activity, due to the active and dimer form, were detected in samples from SA; however, these bands were absent in samples from AJD and controls. Using immunocapture activity assays, MMP-2 and -9 activities were found to be significantly elevated in joints from SA compared to controls and AJD samples. MMP-2 activity in samples from AJD was significantly increased compared to controls. Both MMP activities decreased in the joints from SA in the course of successful therapy.

CONCLUSIONS

Data from zymographic analysis confirmed that MMP-2 and -9 were elevated in equine joint diseases. Immunocapture activity assays have been shown to be suitable for the quantitative determination of MMP-2 and -9 activities in synovial fluid of horses. Both MMP-2 and -9 activities seem to be useful to indicate SA, and MMP-2 activity might be a suitable marker for AJD.

POTENTIAL RELEVANCE

These findings encourage the potential use of MMP-2 and -9 as additional aids to clinical investigation. Further work is required to validate the clinical significance of MMP activities in the progress of different joint diseases in horses.

Measurement of equine myeloperoxidase (MPO) activity in synovial fluid by a modified MPO assay and evaluation of joint diseases – An initial case study

The aim of this study was to develop a specific myeloperoxidase (MPO) activity assay in the synovial fluid of horses and investigate whether MPO activity is increased in different forms of joint diseases. Synovial fluid samples were taken from affected joints from horses with osteoarthritis, chronic non-septic arthritis and septic arthritis, and from healthy control horses. MPO activity was measured using a specific modified o-dianisidine-assay containing 4-aminobenzoic acid hydrazide as a potent and specific inhibitor of the MPO. This assay is characterized by high reproducibility. The results reveal only a slight elevation of MPO activity in the synovial fluid of horses with osteoarthritis and chronic non-septic arthritis. However, in the cases of septic arthritis a significant increase in MPO activity was found when compared to the controls. In conclusion the first field study suggests that synovial fluid MPO may be used as a marker for septic arthritis in horses.

MT3-MMP (MMP-16) is downregulated by in vitro cytokine stimulation of cartilage, but unaltered in naturally occurring equine osteoarthritis and osteochondrosis

Matrix degradation by metalloproteinases is considered a key feature in the loss of articular cartilage seen in many joint diseases. Membrane-type matrix metalloproteinase-3 (MT3-MMP) expression is elevated in human cartilage in end-stage osteoarthritis. We investigated whether MT3-MMP is similarly regulated in cartilage in two naturally occurring arthropathies in vivo and whether proinflammatory cytokines regulate its expression in vitro. MT3-MMP expression was evaluated in cartilage from horses with osteoarthritis and osteochondrosis and compared with age- and site-matched normal cartilage. MT3-MMP also was measured in normal cartilage stimulated with proinflammatory cytokines. MT3-MMP expression was not significantly altered in either osteoarthritis or osteochondrosis cartilage. However, gene expression was significantly downregulated by the addition of recombinant human interleukin-1beta, oncostatin M, or tumor necrosis factor-alpha to normal cartilage explants. The results suggest that MT3-MMP may not have a role in matrix destruction in equine cartilage diseases. Further work is required to characterize its regulation and function.

Effects of treatment with polysulfated glycosaminoglycan on serum cartilage oligomeric matrix protein and C-reactive protein concentrations, serum matrix metalloproteinase-2 and -9 activities, and lameness in dogs with osteoarthritis

OBJECTIVE

To investigate the effects of polysulfated glycosaminoglycan (PSGAG) treatment on serum cartilage oligomeric matrix protein (COMP) concentration, matrix metal-loproteinase-2 (MMP-2) and -9 (MMP-9) activities, C-reactive protein (CRP) concentration, and lameness scores in dogs with osteoarthritis.

ANIMALS

16 dogs with osteoarthritis and 5 clinically normal dogs.

PROCEDURES

Dogs with osteoarthritis had a history of chronic lameness, and osteophytes were observed on radiographic evaluation of the affected joint. Polysulfated glycosaminoglycan was administered IM twice a week for a total of 8 treatments to all dogs with osteoarthritis and to clinically normal control dogs.

RESULTS

Lameness scores after PSGAG treatment in osteoarthritic dogs improved in 12 of the 16 dogs. Serum COMP concentrations in osteoarthritic dogs were significantly higher than in control dogs before treatment. Lameness scores in osteoarthritic dogs decreased significantly after treatment, compared with before treatment. Lameness scores of 9 dogs with hind limb lameness improved significantly after treatment; these dogs had corresponding decreases in serum COMP concentrations. After treatment, serum COMP concentrations and lameness scores of 7 dogs with forelimb lameness remained high and were significantly higher than those of dogs with hind limb lameness. Serum MMP-9 activities of dogs with forelimb lameness were significantly higher than in dogs with hind limb lameness after treatment.

CONCLUSIONS AND CLINICAL RELEVANCE

IM administration of PSGAG inhibited COMP degradation in dogs with osteoarthritis. Results indicate that decreases in serum COMP concentrations might be related to improvement in lameness after PSGAG treatment.

Equine osteoarthritis: a brief review of the disease and its causes

Degenerative joint diseases, such as osteoarthritis, adversely impact the health of the equine athlete as well as the economics of the equine industry. Our understanding of the aetiology of osteoarthritis, although not nearly exhaustive, has increased substantially in recent years. Molecules, including cytokines, inflammatory mediators, and metalloproteinases, have been identified and associated with the progression of joint disease. Several factors, including trauma to the joint, immobilization, conformation, shoeing, and ageing, have been linked with osteoarthritis. Our continued efforts into elucidating critical biological mediators and risk factors, coupled with better chondroprotective therapies and diagnostic tools, should facilitate our ability to maintain the skeletal health of the equine athlete

Urine cartilage oligomeric matrix protein (COMP) measurement is useful in discriminating the osteoarthritic Thoroughbreds

OBJECTIVE

To quantify the urinary concentration of cartilage oligomeric matrix protein (COMP), and to evaluate the relationship between urinary COMP concentration and the catabolic activity of synovial fluid (SF) in diseased horses.

METHODS

COMP in horse urine was detected by immunoblotting with a monoclonal antibody (mAb; 14G4) raised against equine COMP from articular cartilage. Urine and serum samples were obtained from 83 Thoroughbred horses with aseptic joint diseases (AJD, 79 horses) or septic joint diseases (SJD, four horses) at the time of anesthesia induction, and samples of SF were obtained during surgery. Control samples of urine (n=111) were collected from normal horses free of any orthopedic diseases after they had been racing. COMP concentration was determined in all samples using inhibition enzyme-linked immunosorbent assay (ELISA) with mAb 14G4. SF samples were also used for the quantification of gelatinase activity.

RESULTS

Positive bands of COMP fragments were determined on the immunoblots with mAb 14G4. The urinary COMP concentrations in AJD and SJD horses (1.02+/-0.75 and 1.55+/-1.17 microg/100mg creatinine, respectively) were significantly higher than normal (0.57+/-0.29 microg/100mg creatinine). In 55 horses with fractures in the AJD group there was a logarithmic relationship (r=-0.45, P<0.001) between the urinary and SF COMP measurements, while the urinary COMP level was positively correlated with matrix metalloproteinase (MMP)-2 and -9 activities (r=0.30, P<0.05 and r=0.51, P<0.001, respectively) in SF.

CONCLUSIONS

The urinary COMP assay with mAb 14G4 is useful for discriminating horses with osteoarthritis. The higher COMP levels in urine from such horses would be indicative of enhanced proteolytic activity, in addition to the increased COMP levels in the diseased joints.

Changes in MMP-2 and -9 activity and MMP-8 reactivity after amphotericin B induced synovitis and treatment with bufexamac

The objective here was to evaluate the acute effects of induced arthritis on synovial fluid (SF) levels of matrix metalloproteinases (MMP) -2, -8 and -9 in horses. To evaluate MMP-2 and -9 activities and the effect of non-steroidal anti-inflammatory drug (NSAID) bufexamac during remission from acute arthritis. Aseptic arthritis was induced in 24 Standardbred horses using 20 mg of amphotericin B as a single intra-articular (IA) injection in the right intercarpal joint. After 1 week and 2 weeks, horses were treated intra-articularly with 10, 20, or 40 mg of bufexamac suspension or with sterile saline solution as control. SF was sampled prior to induction and at weekly intervals for 5 weeks. Fluids were evaluated for MMP-2 and MMP-9 activity by gelatin zymography or for MMP-8 immunoreactivity by Western Blotting. IA injection of amphotericin B consistently resulted in significant increase in the immunoreactivity of MMP-8 and activity of both the latent and the active forms of MMP-2 and -9, among which the active form of MMP-2 increased the most. MMP-9 levels declined to pre-induction levels within 2 weeks, whereas levels of MMP-2 remained still high after 5 weeks. Treatment with bufexamac did not significantly affect levels of gelatinolytic MMP. Results suggest that after acute arthritis of horses, elevated MMP activity is present in the joint, for several weeks, to a degree that could promote cartilage degradation, and treatment with the NSAID bufexamac is not likely to affect that. Furthermore, analysing levels of MMP-9 activity and especially levels of active forms of MMP-2 activity may be valuable to predict the time of occurrence of arthritis in horses.

Clinical significance of gelatinases in septic arthritis of native and replaced knees

We hypothesized that more gelatinases appear in effusions of septic arthritis than aseptic arthritis. This study examined the laboratory variables of inflammation and the levels of gelatinase A and B (matrix metalloproteinases-2 and -9) in 75 effusions from the knees of 37 patients with inflammatory arthritis and compared them with effusions of septic and aseptic arthritis. Gelatin zymography revealed that the levels of the latent matrix metalloproteinase-9 were higher in 24 effusions of septic arthritis than in 51 effusions of aseptic arthritis. The latent matrix metalloproteinase-9 levels of septic arthritis also correlated with the neutrophil counts in effusions. Significantly more activated matrix metalloproteinases-2 and -9 appeared in effusions of septic arthritis in native and replaced knees than in effusions of aseptic arthritis. A high matrix metalloproteinase-9 level and the appearance of activated matrix metalloproteinases-2 and -9 may distinguish septic from aseptic arthritis, even in cases with a low neutrophil count in the replaced knee. Joint aspiration may not only reduce the bacteria counts, endotoxins, and proinflammatory cytokines, but also decrease the amount of matrix metalloproteinases in effusions that attack the extracellular matrix of native and artificial joints.

The clinical significance of gelatinase B in gouty arthritis of the knee

BACKGROUND

Clinically, gouty arthritis is associated with severe inflammation, such as pain, swelling and erythema of the joints. Gelatinase A and B (matrix metalloproteinase-2 and -9, MMP-2 and -9) participate in the degradation of the extracellular matrix (ECM) components in a variety of arthritis, especially in the inflammatory arthritis.

METHODS

We examined the levels of MMP-2 and -9 in 40 synovial fluids (SFs) from the knee joints of 24 patients with gouty arthritis and compared them with the clinical and laboratory variables of inflammation.

RESULTS

Gelatin zymography revealed that not only activated MMP-2 levels but also proMMP-9 levels in SF from the knee joints of gouty arthritis were associated with the local arthritis activity scores (LAS) (p < 0.001) and correlated well with the neutrophil counts in SF as well (p < 0.001). A similar correlation between proMMP-9 levels and LAS was also found within the individual patients before and during treatment with nonsteroidal antiinflammatory drugs (NSAIDs; p < 0.001). ProMMP-2 appeared in all SFs irrespective of LAS and neutrophil counts.

CONCLUSIONS

The analysis of MMP-9 in SF samples can reveal the inflammatory condition of the knee joints with gouty arthritis. Joint aspiration may decrease the amount of MMPs in SF to attack the ECM of joint whether it is normal or not.

Assessment of the effects of age and joint disease on hydroxyproline and glycosaminoglycan concentrations in synovial fluid from the metacarpophalangeal joint of horses

OBJECTIVE

To assess the effects of age and joint disease on hydroxyproline and glycosaminoglycan (GAG) concentrations in synovial fluid from the metacarpophalangeal joint of horses and evaluate the association of those concentrations with severity of osteoarthritis and general matrix metalloproteinase (MMP) activity.

SAMPLE POPULATION

Synovial fluid was collected from the metacarpophalangeal joints of foals at birth (n = 10), 5-month-old foals (10), 11-month-old foals (5), and adult horses (73).

PROCEDURE

Hydroxyproline and GAG concentrations were determined in synovial fluid samples. The severity of osteoarthritis in adult joints was quantified by use of a cartilage degeneration index (CDI) and assessment of general MMP-activity via a fluorogenic assay.

RESULTS

Hydroxyproline and GAG concentrations in synovial fluid were highest in neonates and decreased with age. Concentrations reached a plateau in adults by 4 years and remained constant in healthy joints. In synovial fluid from osteoarthritic joints, hydroxyproline and GAG concentrations were not increased, compared with unaffected joints, but hydroxyproline were significantly correlated with the CDI and general MMP activity. There was no significant correlation between GAG concentration and CDI value or MMP activity.

CONCLUSIONS AND CLINICAL RELEVANCE

Changes in hydroxyproline concentration in synovial fluid appeared to indicate damage to collagen of the articular cartilage. In joints with osteoarthritis, the lack of high GAG concentration in synovial fluid and the absence of a significant correlation between GAG concentration and CDI values or MMP activity may severely limit the usefulness of this marker for monitoring equine joint disease.

Evaluation of serum concentrations of biomarkers of skeletal metabolism and results of radiography as indicators of severity of osteochondrosis in foals

OBJECTIVE

To determine whether serum concentrations of biomarkers of skeletal metabolism can, in conjunction with radiographic evaluation, indicate severity of osteochondrosis in developing horses.

ANIMALS

43 Dutch Warmblood foals with varying severity of osteochondrosis.

PROCEDURE

24 foals were monitored for 5 months and 19 foals were monitored for 11 months. Monthly radiographs of femoropatellar-femorotibial and tibio-tarsal joints were graded for osteochondral abnormalities. Serial blood samples were assayed for 8 cartilage and bone biomarkers. At the end of the monitoring period, foals were examined for macroscopic osteochondrosis lesions.

RESULTS

Temporal relationships were evident between certain serum biomarkers and osteochondrosis severity in foals during their first year. Biomarkers of collagen degradation (collagenase-generated neoepitopes of type-II collagen fragments, type-I and -II collagen fragments [COL2-3/4C(short)], and cross-linked telopeptide fragments of type-I collagen) and bone mineralization (osteocalcin) were positive indicators of osteochondrosis severity at 5 months of age. In foals with lesions at 11 months of age, osteochondrosis severity correlated negatively with COL2-3/4C(short) and osteocalcin and positively with C-propeptide of type-II procollagen (CPII), a collagen synthesis marker. Radiographic grading of osteochondrosis lesions significantly correlated with macroscopic osteochondrosis severity score at both ages and was strongest when combined with osteocalcin at 5 months and CPII at 11 months.

CONCLUSIONS AND CLINICAL RELEVANCE

The ability of serum biomarkers to indicate osteochondrosis severity appears to depend on stage of disease and is strengthened with radiography. In older foals with more permanent lesions, osteochondrosis severity is significantly related to biomarker concentrations of decreased bone formation and increased cartilage synthesis.

Gelatinase activity in synovial fluid and synovium obtained from healthy and osteoarthritic joints of dogs

OBJECTIVE

To determine matrix metalloproteinase (MMP) activity in synovial fluid (SF) obtained from the joints of dogs with degenerative joint disease (DJD) secondary to various underlying conditions.

SAMPLE POPULATION

35 samples of SF obtained from 18 clinically normal (control) dogs and 34 samples of SF obtained from 17 dogs with DJD; dogs with DJD were from 2 populations (client-owned dogs and research dogs that had DJD secondary to the lysosomal storage disease mucopolysaccharidosis VII).

PROCEDURE

MMP activity in samples of SF was semiquantitatively examined by use of gelatin or casein zymography. Western blot analysis was performed by use of antibodies for MMP-2 and MMP-9. In addition, in situ MMP activity was observed in sections of synovial membrane obtained from healthy and osteoarthritic joints.

RESULTS

Samples of SF from osteoarthritic joints had higher MMP-2 activity and dramatically increased MMP-9 activity, compared with values for healthy joints. Substrate-overlay analyses indicated minimal gelatin-degrading activity in synoviocytes obtained from control dogs, whereas greater activity was seen in osteoarthritic synoviocytes, with additional activity in the underlying tissue.

CONCLUSIONS AND CLINICAL RELEVANCE

Higher MMP-2 activity and dramatic increases in MMP-9 activity were associated with the osteoarthritic state, even though MMP-2 activity was detected in healthy joints. This study expands information on MMP production in SF of osteoarthritic joints in other species and documents the similarity of MMP activity patterns regardless of the cause of DJD.

Biochemical characterisation of navicular hyaline cartilage, navicular fibrocartilage and the deep digital flexor tendon in horses with navicular disease

The study hypothesis was that navicular disease is a process analogous to degenerative joint disease, which leads to changes in navicular fibrocartilage and in deep digital flexor tendon (DDFT) matrix composition and that the process extends to the adjacent distal interphalangeal joint. The objectives were to compare the biochemical composition of the navicular articular and palmar cartilages from 18 horses with navicular disease with 49 horses with no history of front limb lameness, and to compare navicular fibrocartilage with medial meniscus of the stifle and collateral cartilage of the hoof. Cartilage oligomeric matrix protein (COMP), deoxyribonucleic acid (DNA), total glycosaminoglycan (GAG), metalloproteinases MMP-2 and MMP-9 and water content in tissues were measured. Hyaline cartilage had the highest content of COMP and COMP content in hyaline cartilage and tendon was higher in lame horses than in sound horses (p<0.05). The concentration of MMP-2 amount in hyaline cartilage was higher in lame horses than in sound horses. The MMP-2 amounts were significantly higher in tendons compared to other tissue types. Overall, 79% of the lame horses with lesions had MMP-9 in their tendons and the amount was higher than in sound horses (p<0.05). In horses with navicular disease there were matrix changes in navicular hyaline and fibrocartilage as well as the DDFT with potential implications for the pathogenesis and management of the condition.

Animal experimentation in snake venom research and in vitro alternatives

Current experimental techniques used in snake venom research (with and without the use of animals) are reviewed. The emphasis is on the reduction of the use of animals in the development of antivenoms for the clinical treatment of snakebite. Diagnostic and research techniques for the major pathologies of envenoming are described and those using animals are contrasted with non-sentient methods where possible. In particular, LD50 and ED50 assays using animals (in vivo) and fertilised eggs (in vivo, non-sentient) are compared as well as in vitro procedures (ELISA and haemolytic test) for ED50 estimations. The social context of antivenom production, supply and demand is outlined together with the consequent tension between the benefits derived and the increase in opposition to experiments on animals. Stringent regulations governing the use of animals, limited research funds and public pressure all focus the need for progress towards non-animal, or non-sentient, research methods. Some achievements are noted but success is hampered by lack of detailed knowledge of the many constituents of venom which have to be assessed as a whole rather than individually. The only way to evaluate the net pathological effect of venom is to use a living system, usually a rodent, and similarly, the efficacy of antivenoms is also measured in vivo. The pre-clinical testing of antivenoms in animals is therefore a legal requirement in many countries and is strictly monitored by government authorities. New technologies applied to the characterisation of individual venom proteins should enable novel in vitro assays to be designed thus reducing the number of animals required. In the meantime, the principles of Reduce, Refine and Replace relating to animals in research are increasingly endorsed by those working in the field and the many agencies regulating ethical and research policy.

Matrix metalloproteinase-2 and -9 involvement in canine tumors

Matrix metalloproteinases (MMPs) are a family of enzymes implicated in the degradation and remodeling of extracellular matrix and in vascularization. They are also involved in pathologic processes such as tumor invasion and metastasis in experimental cancer models and in human malignancies. We used gelatin zymography and immunohistochemistry to determine whether MMP-2 and MMP-9 are present in canine tumors and normal tissues and whether MMP production correlates with clinicopathologic parameters of prognostic importance. High levels of pro-MMP-9, pro-MMP-2, and active MMP-2 were detected in most canine tumors. Significantly higher MMP levels were measured in canine tumors than in nontumors, malignancies had higher MMP levels than benign tumors, and sarcomas had higher active MMP-2 than carcinomas. Cartilaginous tumors produced higher MMP levels than did nonsarcomatous malignancies, benign tumors, and normal tissues, and significantly greater MMP-2 than osteosarcomas and fibrosarcomas. Pro-MMP-9 production correlated with the histologic grade of osteosarcomas. The 62-kd form of active MMP-2 was detected only in high-grade, p53-positive, metastatic malignancies. Zymography proved to be a sensitive and quantitative technique for the assessment of MMP presence but has the limitation of requiring fresh tissue; immunohistochemistry is qualitative and comparatively insensitive but could be of value in archival studies. MMP presence was shown in a range of canine tumors, and their link to tumor type and grade was demonstrated for the first time. This study will allow a substantially improved evaluation of veterinary cancer patients and provides baseline information necessary for the design of clinical trials targeting MMPs.

Gastrin-stimulated gastric epithelial cell invasion: the role and mechanism of increased matrix metalloproteinase 9 expression

The gastric hormone gastrin regulates the organization of the gastric epithelium, but the cellular control mechanisms are yet unknown. Epithelial remodelling typically involves extracellular proteolysis mediated by the matrix metalloproteinases (MMPs). Since a gene-array analysis of the gastric cancer cell line AGS-G(R) suggested that gastrin increased MMP-9 expression, we examined the control of MMP-9 expression by gastrin. Gelatin zymography confirmed gastrin induction of MMP-9 in AGS-G(R) cells, but showed a small inhibition of MMP-2. Immunocytochemical studies showed that MMP-9 was localized to vesicles that appeared to traffic along the processes that were extended in response to gastrin. Gastrin stimulated the invasion of AGS-G(R) cells through artificial basement membrane, which was reduced by an inhibitor of MMP-2/-9. There was also an increase in MMP-9 in the stomach of patients with elevated plasma gastrin and multiple-endocrine neoplasia type 1 (MEN-1) syndrome, suggesting in vivo regulation of MMP-9 expression by gastrin. Finally, we showed that the expression of 1.9 kb of human MMP-9 gene promoter coupled with luciferase (MMP-9-luc) was increased 7.65+/-1.2-fold by gastrin, via a pathway which includes stimulation of protein kinase C, and activation of Raf and the mitogen-activated protein (MAP) kinase pathway. The tumour suppressor menin (which is mutated in MEN-1 syndrome) inhibited the expression of MMP-9-luc by gastrin. These results suggest that gastrin increases MMP-9 expression, which is associated with increased invasion, and this is a putative mechanism regulating remodelling of the gastric epithelium.

Serum level of cartilage oligomeric matrix protein (COMP) in equine osteoarthritis

This study was designed to assay and compare cartilage oligomeric matrix protein (COMP) in horse sera, in samples from normal and joint diseased horses, and to investigate the relationships between COMP in sera and synovial fluids (SF) with keratan sulphate (KS) data. Sera from 38 horses free of any joint pathology (controls) and from horses with aseptic joint disease (AJD horses, n = 40) were assayed for COMP and KS concentrations. Of the 78 horses in the study, 53 were also assayed for COMP and KS concentrations in SF. COMP and KS were measured by inhibition ELISA, using monoclonal antibodies 12C4 and 5D4, respectively. The COMP concentration in sera from AJD horses (mean +/- s.d. 10.7 +/- 7.4 microg/ml) was significantly (P<0.02) lower than in control sera (14.8 +/- 7.8 microg/ml). The joint disease sera also had significantly lower (P<0.01) KS levels (180.5 +/- 61.8 ng/ml) than controls (237.1 +/- 116.1 ng/ml). A significant correlation (r = 0.52, n = 53, P<0.001) was seen between serum and SF in COMP levels; no such relationship was seen in KS levels. It is possible that serum COMP concentration could be a more specific marker of equine joint disease than any other described to date.

Gastrin-stimulated gastric epithelial cell invasion: the role and mechanism of increased matrix metalloproteinase 9 expression

The gastric hormone gastrin regulates the organization of the gastric epithelium, but the cellular control mechanisms are yet unknown. Epithelial remodelling typically involves extracellular proteolysis mediated by the matrix metalloproteinases (MMPs). Since a gene-array analysis of the gastric cancer cell line AGS-G(R) suggested that gastrin increased MMP-9 expression, we examined the control of MMP-9 expression by gastrin. Gelatin zymography confirmed gastrin induction of MMP-9 in AGS-G(R) cells, but showed a small inhibition of MMP-2. Immunocytochemical studies showed that MMP-9 was localized to vesicles that appeared to traffic along the processes that were extended in response to gastrin. Gastrin stimulated the invasion of AGS-G(R) cells through artificial basement membrane, which was reduced by an inhibitor of MMP-2/-9. There was also an increase in MMP-9 in the stomach of patients with elevated plasma gastrin and multiple-endocrine neoplasia type 1 (MEN-1) syndrome, suggesting in vivo regulation of MMP-9 expression by gastrin. Finally, we showed that the expression of 1.9 kb of human MMP-9 gene promoter coupled with luciferase (MMP-9-luc) was increased 7.65+/-1.2-fold by gastrin, via a pathway which includes stimulation of protein kinase C, and activation of Raf and the mitogen-activated protein (MAP) kinase pathway. The tumour suppressor menin (which is mutated in MEN-1 syndrome) inhibited the expression of MMP-9-luc by gastrin. These results suggest that gastrin increases MMP-9 expression, which is associated with increased invasion, and this is a putative mechanism regulating remodelling of the gastric epithelium.

Microscopic localization of active gelatinases in equine osteochondritis dissecans (OCD) cartilage

OBJECTIVE

To investigate the relationship between matrix metalloproteinase (MMP) activity and osteochondritis dissecans (OCD) in the equine joint.

METHODS

Equine articular cartilage was obtained from normal (N = 8) and osteochondrotic (OCD) (N = 6) femoropatellar joints from horses at necropsy. The activity of gelatinase MMPs was determined in sections of cartilage by in situ gelatin zymography.

RESULTS

Gelatinase activity was markedly increased in articular cartilage obtained from OCD samples and was particularly prominent in the deep cartilage zone. Activity was only seen in the pericellular area of chondrocytes. In addition, in OCD cartilage there were vertical lines of activity, starting from the deep zone and radiating towards the articular surface. In contrast, normal cartilage showed only a very small amount of gelatinolytic activity, which was not restricted to specific cartilage zones. Gelatin zymography of culture supernatants from isolated chondrocytes demonstrated increased production of MMP-2 and MMP-9 from OCD chondrocytes.

CONCLUSIONS

Sections of articular cartilage from OCD lesions revealed MMP activity, especially in the deep zone adjacent to the calcified subchondral bone. This MMP activity could account for the loss of cartilage integrity in the deep cartilage zone and the vertical lines of activity could represent areas of mechanical weakness, likely to result in fissures and the release of cartilage fragments into the joint space.

Synovial fluid studies in navicular disease

The purpose of this study was to investigate biochemical changes in synovial fluid in navicular disease, and to establish if synovial fluid from the distal interphalangeal joint (DIP) could be used diagnostically to assess alterations in the synovial fluid of the navicular bursa. Cartilage oligomeric matrix protein (COMP), total glycosaminoglycans (GAG), hyaluronan (HA), metalloproteinases 2 and -9 (MMP-2 and MMP-9) and total protein (TP) levels were determined in synovial fluids obtained from 18 navicular bursae and 35 DIP -joints from animals suffering from navicular disease, and the same synovial structures in 16 joints of horses with no evidence of abnormalities involving the foot. To avoid dilution effects, GAG/COMP, HA/COMP, MMP-2/ COMP and MMP-9/COMP ratios were also calculated for different synovial cavities. There was a good correlation, for COMP, GAG, HA, MMP-2 and TP levels, between synovial fluid from the navicular bursa and fluid from the DIP -joint in healthy animals. However, in animals with navicular disease, only COMP levels showed no difference between the navicular bursal fluid and the DIP-joint fluid concentration. Thus, enabling the use of COMP to standardise other biochemical concentration measurements from the synovial joint fluids. In horses with navicular disease, there was a significantly lower absolute concentration of GAG, and a significantly lower GAG/COMP ratio, in the synovial fluid of the navicular bursa and the DIP-joint compared to synovial fluid from the same joints from healthy horses. In contrast, the absolute HA concentration and HA/ COMP, MMP-2/COMP and MMP-9/COMP ratios were higher in synovial fluid from the DIP-joint of horses with navicular disease, and MMP-2 and MMP-9 relative activity levels and MMP-2/COMP and MMP-9/ COMP ratios were increased in fluid from navicular bursae in horses with navicular disease when compared to a control group.