Biomedical subjects

J M TeKoppele

Publications and source records attributed to J M TeKoppele.

At least 19 recordsLinked to original sources

PubMed2005

MMP protein and activity levels in synovial fluid from patients with joint injury, inflammatory arthritis, and osteoarthritis.

OBJECTIVE: To determine protein and activity levels of matrix metalloproteinases 1 and 3 (MMP-1 and MMP-3) in synovial fluid of patients with knee joint injury, primary osteoarthritis, and acute pyrophosphate arthritis (pseudogout). METHODS: Measurements were done on knee synovial fluid obtained in a cross sectional study of cases of injury (n = 283), osteoarthritis (n = 105), and pseudogout (n = 65), and in healthy controls (n = 35). Activity of MMP-1 and MMP-3 in alpha(2) macroglobulin complexes was measured using specific low molecular weight fluorogenic substrates. ProMMP-1, proMMP-3, and TIMP-1 (tissue inhibitor of metalloproteinase 1) were quantified by immunoassay. RESULTS: Mean levels of proMMP-1, proMMP-3, and TIMP-1 were increased in injury, osteoarthritis, and pseudogout compared with controls. MMP-1 activity was increased in pseudogout and injury groups over control levels, whereas MMP-3 activity was increased only in the pseudogout group. The increase in MMP-1 activity coincided with a decrease in TIMP-1 levels in the injury group. CONCLUSIONS: Patients with joint injury have a persistent increase in proMMP-1 and proMMP-3 in synovial fluid and an increase in activated MMPs, which are not inhibited by TIMP. The differences in activation and inhibition patterns between the study groups are consistent with disease specific patterns of MMP activation and/or inhibition in joint pathology.

Acute Disease↗

PubMed2004

MMP profile in paired serum and synovial fluid samples of patients with rheumatoid arthritis.

OBJECTIVE: To analyse matrix metalloproteinases (MMPs) and tissue inhibitor-1 of MMPs (TIMP-1) levels in the systemic circulation and synovial fluid (SF) of patients with RA and to compare these levels with inflammatory and collagen degradation markers. METHODS: ProMMP-1, -2, -3, -8, -9, TIMP-1, levels of MMP/alpha(2)-macroglobulin complexes, and collagen degradation products were measured by sandwich ELISA, activity assays, and HPLC in paired SF and serum samples from 15 patients with RA and 13 with OA. RESULTS: MMPs were higher in SF of patients with RA than in OA or controls. MMP levels in SF of patients with OA were higher than in controls. In serum, levels of proMMP-3, -8 and -9 were higher in patients with RA than in OA or controls, whereas only proMMP-8 and -9 were higher in serum of patients with OA than in controls. A strong correlation was seen between serum and SF levels of MMP-8 and -9 in RA. Increased levels of MMP/alpha(2)-macroglobulin complexes indicated an MMP/TIMP imbalance in serum and SF in RA. SF hydroxyproline correlated significantly with SF levels of proMMP-9 in RA. CONCLUSIONS: Systemic MMP-8 and -9 levels represent the situation in the inflamed joint; MMP-9 is likely to be involved in degradation of joint collagen. The hypothesis of MMP/TIMP imbalance in RA is strengthened.

Adult↗

PubMed2003

Matrix metalloproteinases-3, -8, -9 as markers of disease activity and joint damage progression in early rheumatoid arthritis.

OBJECTIVE: To analyse the relation between systemic levels of pro-MMP-3, -8, and -9 matrix metalloproteinase (MMP) activity in alpha(2) macroglobulin (alpha(2)M)/MMP complexes and the progression of joint destruction in patients with recent onset rheumatoid arthritis (RA). METHODS: 109 patients with RA of recent onset were entered into this longitudinal study. Patients were followed up for two years; clinical data, blood samples, and radiographs were obtained at baseline and at 1 and 2 years. Serum levels of MMPs were measured by sandwich ELISA and MMP activity assays. RESULTS: During the two years joint damage progressed from 0 to 10 (median Sharp score, p<0.001). Stable levels of pro-MMP-3 and a significant decrease in the levels of pro-MMP-8 and -9 and alpha(2)M/MMP complexes were seen throughout the two years. Regression analysis showed that serum pro-MMP-3 levels at disease onset were independently associated with the progression of joint damage (B=0.7, 95% CI 0.3 to 1.1, p=0.001). Based on the rate of joint destruction, patients were divided into two subgroups: patients with mild and severe joint damage progression. The pro-MMP-3 levels were significantly higher in the group with severe compared with mild disease at all times. Levels of pro-MMP-8 and -9 were decreased in both groups, whereas alpha(2)M/MMP complex levels decreased in the group with mild disease only. CONCLUSION: Serum levels of the MMPs studied are associated with disease activity, but serum pro-MMP-3 levels at the onset of disease are also predictive of joint damage progression.

Adult↗

PubMed2002

The canine 'groove' model, compared with the ACLT model of osteoarthritis.

OBJECTIVE: The frequently used anterior cruciate ligament transection (ACLT) model of osteoarthritis (OA) in the dog, makes use of a permanent trigger (joint instability) for inducing degenerative changes. The present study evaluates a canine model of degenerative cartilage damage, mimicking OA, which is induced without making use of permanent joint instability. METHODS: The articular cartilage of the weight-bearing areas of the femoral condyles in one knee of ten beagle dogs was damaged by making grooves, without damaging the subchondral bone. Surgery was followed by 10 weeks intensified loading of the affected joint. Subsequently, joint damage and inflammation were evaluated. The effects were compared with those of the ACLT model. RESULTS: Histological analysis showed chondrocyte clusters around cartilage lesions and moderate loss of proteoglycans in the 'groove' model. Synovial inflammation was mild. Biochemical analysis of cartilage showed changes in matrix proteoglycan turnover, proteoglycan content, and collagen damage, all characteristics of OA. Synovial fluid MMP-1, -3 and -13 activity was enhanced. Changes were found in condyles and plateau, were similar for all animals tested, and were similar to the changes observed in the ACLT model. CONCLUSION: The presently described canine 'groove' model shows characteristics identical to those seen in the ACLT model but differs in a way that the changes are induced without joint instability. The latter is expected to make the 'groove' model more sensitive to treatment.

Animals↗

PubMed2002

A comparative analysis of bone and cartilage metabolism in two strains of guinea-pig with varying degrees of naturally occurring osteoarthritis.

OBJECTIVE: To evaluate the interaction of bone and cartilage in knee osteoarthritis (OA) pathogenesis in two guinea-pig strains with appreciable differences in bone metabolism. DESIGN: Two guinea-pig strains were evaluated for their susceptibilities to OA using semi-quantitative histological grading of knee joints and quantification of biomarkers including urinary excretion of hydroxylysyl-pyridinoline (HP) and lysyl-pyridinoline (LP) collagen cross-links, serum osteocalcin (OC), and synovial fluid levels of keratan sulfate (KS). RESULTS: At 12 months of age, Strain 13 guinea-pigs had minimal to mild histological evidence of OA compared to the Hartley strain guinea-pigs. The Hartley strain, with more severe OA, had a higher rate of bone formation (serum osteocalcin) and bone resorption (HP and LP) evident at a young age with persistence of a greater rate of bone formation at 12 months of age. The Strain 13 possessed much thicker subchondral bone at the outset (2 months) compared to the Hartley; however, the Hartley strain showed the greatest increase in subchondral bone thickness coincident with the development of cartilage degeneration. Thus, the process of subchondral bone thickening, in contrast to the absolute initial subchondral bone thickness, was a hallmark of OA in the guinea-pig. Moreover, Strain 13 had lower intraarticular proteoglycan turnover. Levels of synovial fluid keratan sulfate were positively correlated with the severity of histological OA. CONCLUSIONS: This pilot study represents the first evidence of differential susceptibility to OA in guinea-pigs. Comparison of these two strains of guinea-pig has revealed that increased metabolism within the affected tissues, cartilage and bone, is associated with the development and progression of OA. This work demonstrates that the Strain 13 is a viable age-matched control to the Hartley strain and merits a more in depth evaluation of the contribution of bone and bone metabolism to OA.

Amino Acids↗

PubMed2002

Development of biochemical heterogeneity of articular cartilage: influences of age and exercise.

The objective of this study was to document the development of biochemical heterogeneity from birth to maturity in equine articular cartilage, and to test the hypothesis that the amount of exercise during early life may influence this process. Neonatal foals showed no biochemical heterogeneity whatsoever, in contrast to a clear biochemical heterogeneity in mature horses. The process of formation of site differences was almost completed in exercised foals age 5 months, but was delayed in those deprived of exercise. For some collagen-related parameters, this delay was not compensated for after an additional 6 month period of moderate exercise. It is concluded that the functional adaptation of articular cartilage, as reflected in the formation of biochemical heterogeneity in the horse, occurs for the most part during the first 5 months postpartum. A certain level of exercise seems essential for this process and withholding exercise in early life, may result in a delay in the adaptation of the cartilage.

Adaptation, Physiological↗

PubMed2002

Biochemical development of subchondral bone from birth until age eleven months and the influence of physical activity.

Subchondral bone provides structural support to the overlying articular cartilage, and plays an important role in osteochondral diseases. There is growing insight that the mechanical features of bone are related to the biochemistry of the collagen network and the mineral content. In the present study, part of the normal developmental process and the influence of physical activity on biochemical composition of subchondral bone was studied. Water content, calcium content and characteristics of the collagen network (collagen, hydroxylysine, lysylpyridinoline (LP) and hydroxylysylpyridinoline (HP) crosslinking) of subchondral bone were measured in newborn foals, 5-month-old foals (pasture-grown and box-confined) and 11-month-old foals at 2 differently loaded sites of the proximal articular surface of the first phalanx. During the first 5 months postpartum, water and hydroxylysine content decreased significantly while calcium and collagen content and the amount of HP and LP crosslinks increased significantly. The withholding of physical activity during this developmental phase affected the biochemical characteristics of subchondral bone only at the site that is loaded during physical exercise. At this site, calcium content and both HP and LP crosslink levels increased significantly less than in pasture-raised animals. During development from 5-11 months, measured parameters remained essentially constant, except for water content, which decreased further. It is concluded that substantial changes, presumed to be largely exercise-driven, take place during the normal process of development in the biochemical composition of equine subchondral bone. Normal development of subchondral bone is presumably important for the normal functional adaptation of this bone to the loading conditions it is subjected to and therefore essential to resist the future biomechanical challenges the horse will encounter during its athletic career. The findings from this study and the assumed important role of subchondral bone quality in the pathogenesis of osteochondral disease merit more attention to the role of the collagen network in subchondral bone.

Amino Acids↗

PubMed2001

Accumulation of advanced glycation end products decreases collagen turnover by bovine chondrocytes.

The integrity of the collagen network is essential for articular cartilage to fulfill its function in load support and distribution. Damage to the collagen network is one of the first characteristics of osteoarthritis. Since extensive collagen damage is considered irreversible, it is crucial that chondrocytes maintain a functional collagen network. We investigated the effects of advanced glycation end products (AGEs) on the turnover of collagen by articular cartilage chondrocytes. Increased AGE levels (by culturing in the presence of ribose) resulted in decreased collagen synthesis (P < 0.05) and decreased MMP-mediated collagen degradation (P < 0.02). The latter could be attributed to increased resistance of the collagen network to MMPs (P < 0.05) as well as the decreased production of MMPs by chondrocytes (P < 0.02). Turnover of a protein is determined by its synthesis and degradation rates and therefore these data indicate that collagen turnover is decreased at enhanced AGE levels. Since AGE levels in human cartilage increase approximately 50 fold between age 20 and 80, cartilage collagen turnover likely decreases with increasing age. Impaired collagen turnover adversely affects the capacity of chondrocytes to remodel and/or repair its extracellular matrix. Consequently, age-related accumulation of AGE (via decreased collagen turnover) may contribute to the development of cartilage damage in osteoarthritis.

Animals↗

PubMed2001

Age-related decrease in susceptibility of human articular cartilage to matrix metalloproteinase-mediated degradation: the role of advanced glycation end products.

OBJECTIVE: Progressive destruction of articular cartilage is a hallmark of osteoarthritis (OA) and rheumatoid arthritis (RA). Age-related changes in cartilage may influence tissue destruction and thus progression of the disease. Therefore, the effect of age-related accumulation of advanced glycation end products (AGEs) on cartilage susceptibility to proteolytic degradation by matrix metalloproteinases (MMPs) present in synovial fluid (SF) of OA and RA patients was studied. METHODS: Cartilage was incubated with APMA-activated SF obtained from OA or RA patients, and tissue degradation was assessed by colorimetric measurement of glycosaminoglycan (GAG) release. Cartilage degradation was related to the level of AGEs in cartilage from donors of different ages (33-83 years) and in cartilage with in vitro-enhanced AGE levels (by incubation with ribose). MMP activity in SF was measured using a fluorogenic substrate. AGE levels were assessed by high-performance liquid chromatography measurement of the glycation product pentosidine. RESULTS: In cartilage from donors ages 33-83 years, a strong correlation was found between the age-related increase in pentosidine and the decrease in MMP-mediated tissue degradation (r = -0.74, P < 0.0005). Multiple regression analysis showed pentosidine to be the strongest predictor of the decreased GAG release (P < 0.0005); age did not contribute (P > 0.8). In addition, decreased MMP-mediated GAG release was proportional to increased pentosidine levels after in vitro enhancement of glycation (r = -0.27, P < 0.01). This was demonstrated for both OA and RA SF (for control versus glycated, P < 0.002 for all SF samples tested). CONCLUSION: Increased cartilage AGEs resulted in decreased cartilage degradation by MMPs from SF, indicating that aged cartilage is less sensitive than young cartilage to MMP-mediated cartilage degradation, such as occurs in OA and RA. Therefore, the level of cartilage glycation may influence the progression of these diseases.

Adult↗

PubMed2001

The role of collagen in determining bone mechanical properties.

The hypothesis of this study was that collagen denaturation would lead to a significant decrease in the toughness of bone, but has little effect on the stiffness of bone. Using a heating model, effects of collagen denaturation on the biomechanical properties of human cadaveric bone were examined. Prior to testing, bone specimens were heat treated at varied temperatures (37-200 degrees C) to induce different degrees of collagen denaturation. Collagen denaturation and mechanical properties of bone were determined using a selective digestion technique and three-point bending tests, respectively. The densities and weight fractions of the mineral and organic phases in bone also were determined. A repeated measures analysis of variance showed that heating had a significant effect on the biomechanical integrity of bone, corresponding to the degree of collagen denaturation. The results of this study indicate that the toughness and strength of bone decreases significantly with increasing collagen denaturation, whereas the elastic modulus of bone is almost constant irrespective of collagen denaturation. These results suggest that the collagen network plays an important role in the toughness of bone, but has little effect on the stiffness of bone, thereby supporting the hypothesis of this study.

Biomechanical Phenomena↗

PubMed2001

Age-related accumulation of the advanced glycation endproduct pentosidine in human articular cartilage aggrecan: the use of pentosidine levels as a quantitative measure of protein turnover.

During aging, non-enzymatic glycation results in the formation and accumulation of the advanced glycation endproduct pentosidine in long-lived proteins, such as articular cartilage collagen. In the present study, we investigated whether pentosidine accumulation also occurs in cartilage aggrecan. Furthermore, pentosidine levels in aggrecan subfractions of different residence time were used to explore pentosidine levels as a quantitative measure of aggrecan turnover. In order to compare protein turnover rates, protein residence time was measured as racemization of aspartic acid. As has previously been shown for collagen, pentosidine levels increase with age in cartilage aggrecan. Consistent with the faster turnover of aggrecan compared to collagen, the rate of pentosidine accumulation was threefold lower in aggrecan than in collagen. In the subfractions of aggrecan, pentosidine levels increased with protein residence time. These pentosidine levels were used to estimate the half-life of the globular hyaluronan-binding domain of aggrecan to be 19.5 years. This value is in good agreement with the half-life of 23.5 years that was estimated based on aspartic acid racemization. In aggrecan from osteoarthritic (OA) cartilage, decreased pentosidine levels were found compared with normal cartilage, which reflects increased aggrecan turnover during the OA disease process. In conclusion, we showed that pentosidine accumulates with age in aggrecan and that pentosidine levels can be used as a measure of turnover of long-lived proteins, both during normal aging and during disease.

Adolescent↗

PubMed2001

Accumulation of advanced glycation endproducts reduces chondrocyte-mediated extracellular matrix turnover in human articular cartilage.

OBJECTIVE: The prevalence of osteoarthritis (OAs) increases with age and coincides with the accumulation of advanced glycation endproducts (AGEs) in articular cartilage, suggesting that accumulation of glycation products may be involved in the development of OA. This study was designed to examine the effects of accumulation of AGEs on the turnover of the extracellular matrix of human articular cartilage. DESIGN: Chondrocyte mediated cartilage degradation (GAG release, colorimetric) was measured in human articular cartilage of donors aged 19-82 years (N=30, 4-day culture). In addition, to mimic the age-related increase in AGE levels in vitro, cartilage was cultured in the absence or presence of glucose, ribose or threose. Cartilage degradation and proteoglycan synthesis ((35)SO(2)(-4) incorporation) were measured and related to the degree of cartilage AGE levels (fluorescence at 360/460 nm). RESULTS: Chondrocyte-mediated degradation of articular cartilage (i.e. GAG release) decreased with increasing age of the cartilage donor (r=-0.43, P< 0.02). In vitro incubation of cartilage with glucose, ribose or threose resulted in a range of AGE levels that was highly correlated to the chondrocyte-mediated cartilage degradation (r=-0.77, P< 0.001, N=26). In addition, in these in vitro glycated cartilage samples, a decrease in proteoglycan synthesis was observed at increasing AGE levels (r=-0.54, P< 0.005, N=25). CONCLUSIONS: This study shows that an increase in AGE levels negatively affects the proteoglycan synthesis and degradation of articular cartilage. In combination, these two effects reduce the turnover of the cartilage and thereby the maintenance and repair capacity of the tissue. By this mechanism, the age-related increase in cartilage AGE levels may contribute to the development of OA.

Adult↗

PubMed2001

Human granzyme B mediates cartilage proteoglycan degradation and is expressed at the invasive front of the synovium in rheumatoid arthritis.

OBJECTIVE: To investigate the cartilage-degrading capacity of granzyme B and the presence of granzyme B-positive cells at sites of erosion in the rheumatoid synovium. METHODS: Granzyme B was added to [(3)H]proline/[(35)S]sulphate-labelled cartilage matrices and to cartilage explants. Proteoglycan degradation was assessed by the release of (35)S and glycosaminoglycans into the medium and collagen degradation was assessed by the release of (3)H and hydroxyproline and by measuring the fraction of denatured collagen. Granzyme B expression was studied at the invasive front of the synovium by immunohistochemistry. RESULTS: Granzyme B induced loss of both newly synthesized, radiolabelled proteoglycans in cartilage matrices and resident proteoglycans of the cartilage explants. No effect on collagen degradation was found. Granzyme B-positive cells were present throughout the synovium and at the invasive front. CONCLUSION: The presence of granzyme B-positive cells at the invasive front of the synovium together with its ability to degrade articular proteoglycans supports the view that granzyme B may contribute to joint destruction in rheumatoid arthritis.

Animals↗

PubMed2000

Effect of collagen turnover on the accumulation of advanced glycation end products.

Collagen molecules in articular cartilage have an exceptionally long lifetime, which makes them susceptible to the accumulation of advanced glycation end products (AGEs). In fact, in comparison to other collagen-rich tissues, articular cartilage contains relatively high amounts of the AGE pentosidine. To test the hypothesis that this higher AGE accumulation is primarily the result of the slow turnover of cartilage collagen, AGE levels in cartilage and skin collagen were compared with the degree of racemization of aspartic acid (% d-Asp, a measure of the residence time of a protein). AGE (N(epsilon)-(carboxymethyl)lysine, N(epsilon)-(carboxyethyl)lysine, and pentosidine) and % d-Asp concentrations increased linearly with age in both cartilage and skin collagen (p < 0.0001). The rate of increase in AGEs was greater in cartilage collagen than in skin collagen (p < 0.0001). % d-Asp was also higher in cartilage collagen than in skin collagen (p < 0.0001), indicating that cartilage collagen has a longer residence time in the tissue, and thus a slower turnover, than skin collagen. In both types of collagen, AGE concentrations increased linearly with % d-Asp (p < 0.0005). Interestingly, the slopes of the curves of AGEs versus % d-Asp, i.e. the rates of accumulation of AGEs corrected for turnover, were identical for cartilage and skin collagen. The present study thus provides the first experimental evidence that protein turnover is a major determinant in AGE accumulation in different collagen types. From the age-related increases in % d-Asp the half-life of cartilage collagen was calculated to be 117 years and that of skin collagen 15 years, thereby providing the first reasonable estimates of the half-lives of these collagens.

Adolescent↗

PubMed2000

Cartilage degradation and invasion by rheumatoid synovial fibroblasts is inhibited by gene transfer of a cell surface-targeted plasmin inhibitor.

OBJECTIVE: Joint destruction in rheumatoid arthritis (RA) is a result of degradation and invasion of the articular cartilage by the pannus tissue. The present study was undertaken to examine the role of the plasminogen activation system in cartilage degradation and invasion by synovial fibroblasts and investigate a novel gene therapeutic approach using a cell surface-targeted plasmin inhibitor (ATF.BPTI). METHODS: Adenoviral vectors were used for gene transfer. The effects of ATF.BPTI gene transfer on RA synovial fibroblast-dependent cartilage degradation were studied in vitro, and cartilage invasion was studied in vivo in the SCID mouse coimplantation model. RESULTS: The results indicate that cartilage matrix degradation by rheumatoid synovial fibroblasts is plasmin mediated and depends on urokinase-type plasminogen activator for activation. Targeting plasmin inhibition to the cell surface of the fibroblasts by gene transfer of a cell surface-binding plasmin inhibitor resulted in a significant reduction of cartilage matrix degradation in vitro and of cartilage invasion in vivo. Compared with uninfected rheumatoid synovial fibroblasts, the mean +/-SEM cartilage degradation in vitro was reduced to 87.9+/-0.9% after LacZ gene transfer versus a reduction to 24.0+/-1.6% after ATF.BPTI gene transfer (P<0.0001). The mean +/- SEM in vivo cartilage invasion score was 3.1+/-0.4 in the control-transduced fibroblasts and 1.8+/-0.4 in the ATF.BPTI-transduced fibroblasts (P<0.05). CONCLUSION: These results indicate a role of the plasminogen activation system in synovial fibroblast-dependent cartilage degradation and invasion in RA, and demonstrate an effective way to inhibit this by gene transfer of a cell surface-targeted plasmin inhibitor.

Activating Transcription Factors↗

PubMed2000

The increased swelling and instantaneous deformation of osteoarthritic cartilage is highly correlated with collagen degradation.

OBJECTIVE: To provide evidence for the hypothesis that the loss of tensile strength of osteoarthritic (OA) cartilage (resulting in swelling-the hallmark of OA) is due to an impaired collagen network and not to loss or degradation of proteoglycans. METHODS: The amount of degraded collagen molecules, the fixed charge density (FCD) on a dry-weight basis, the degree of swelling in saline, and the instantaneous deformation (ID; a test reflecting the tensile stiffness of the collagen network) were measured in full-depth OA femoral condyle samples. In addition, levels of the crosslink hydroxylysylpyridinoline (HP), the amount of degraded collagen molecules, and the degree of swelling were determined in the 3 zones (surface, middle, and deep) of OA cartilage. We also compared the ID of normal and OA cartilage. RESULTS: In full-depth OA cartilage, a close relationship was found between swelling and ID. Swelling and ID correlated strongly with the amount of degraded collagen molecules, and were not related to FCD. OA cartilage showed the same zonal pattern in HP levels as normal cartilage (i.e., an increase with depth). No relationship was found between collagen crosslinking and swelling of the surface, middle, and deep zones. In all 3 zones, swelling was proportional to the amount of degraded collagen molecules. Compared with that of normal cartilage, the change in ID of OA cartilage was most pronounced at the surface in a direction parallel to the direction of the collagen fibrils. CONCLUSION: The decreased stiffness of the OA collagen network (as measured by swelling and ID) is strongly related to the amount of degraded collagen molecules. The anisotropy in ID parallel and perpendicular to the direction of the fibrils revealed that the impairment of strength resides mainly in, and not between, the fibrils. Proteoglycans play only a minor role in the degeneration of the tensile stiffness of OA cartilage.

Aged↗

PubMed2000

Effect of collagen denaturation on the toughness of bone.

The purpose of this study was to explore the relationship between the integrity of collagen and biomechanical properties of bone. In this study, age (range, 5-26 years old) and gender related changes in cortical bone samples from 33 baboon femurs (15 males and 18 females) were examined. The percentage of denatured collagen was determined using a selective digestion technique. The fracture toughness, elastic modulus, yield and ultimate strength, and energy to fracture of bone were determined in three-point bending configurations. The porosity and weight fractions of the mineral and organic phase also were measured. A two-way analysis of variance showed that age dependent changes were reflected primarily in the amount of denatured collagen, fracture toughness, energy to fracture, and elastic modulus, whereas gender had effects on the fracture toughness, elastic modulus, and porosity of bone. In addition, regression analyses indicated that the percentage of denatured collagen had an inverse correlation with the toughness of bone and a positive correlation with its elastic modulus, whereas mineral content had positive correlation with the strength and elastic modulus of bone. The results of this study suggest collagen influences the toughness of bone, whereas mineral content predominantly contributes to bone stiffness and strength.

Animals↗

PubMed2000

Influence of development and joint pathology on stromelysin enzyme activity in equine synovial fluid.

OBJECTIVE: To investigate the role of stromelysin (MMP-3) activity in synovial fluid (SF) at different stages of development and in common joint disorders in the horse. METHODS: Stromelysin activity was determined with a fluorogenic enzyme activity assay in SF of normal joints of fetal, juvenile and adult horses, and in SF of horses suffering from the developmental orthopaedic disease osteochondrosis (OC) or osteoarthritis (OA). Additionally, MMP-3 activity was expressed as a ratio of previously reported general MMP activity in the same SF samples. RESULTS: The levels of active stromelysin were 30-fold to 80-fold higher in SF from fetal horses than in SF from juvenile and mature animals (p<0.001). Juvenile horses (5 and 11 months of age) showed a twofold to threefold higher stromelysin activity than adult horses ( p<0.05). In OC joints, stromelysin activity was not significantly different from the activity in normal, age matched, control joints. In OA joints the activity was about four times higher than in normal joints (p<0.001). The ratio MMP-3 activity/general MMP activity did not change with age in normal, healthy joints. This ratio was more then twofold increased in OA joints compared with normal joints, indicating selective upregulation of gene expression or activation of proMMP-3, or both, in OA pathology. CONCLUSIONS: The significantly higher stromelysin activity in young individuals parallels the higher metabolic activity occurring at rapid growth and differentiation at early age. In OC, MMP-3 mediated matrix degradation appears to be not different from normal joints. The increased stromelysin activity in OA joints is in agreement with pathological matrix degradation. In these joints MMP-3 activity is selectively increased compared with normal joints.

Aging↗