No abstract

Objective. Osteoarthritis (OA) is one of the most prevalent and disabling chronic conditions affecting the elderly. Its etiology is largely unknown, but age is the most prominent risk factor. The current study was designed to test whether accumulation of advanced glycation end products (AGEs), which are known to adversely affect cartilage turnover and mechanical properties, provides a molecular mechanism by which aging contributes to the development of OA.Methods. The hypothesis that elevated AGE levels predispose to the development of OA was tested in the canine anterior cruciate ligament transection (ACLT) model of experimental OA. Cartilage AGE levels were enhanced in young dogs by intraarticular injections of ribose. This mimics the accumulation of AGEs without the interference of other age-related changes. The severity of OA was then assessed 7 weeks after ACLT surgery in dogs with normal versus enhanced AGE levels.Results. Intraarticular injections of ribose enhanced cartilage AGE levels ϳ5-fold, which is similar to the normal increase that is observed in old dogs. ACLT surgery resulted in more-pronounced OA in dogs with enhanced AGE levels. This was observed as increased collagen damage and enhanced release of proteoglycans. The attempt to repair the matrix damage was impaired; proteoglycan synthesis and retention were decreased at enhanced AGE levels. Mankin grading of histology sections also revealed more-severe OA in animals with enhanced AGE levels.Conclusion. These findings demonstrate increased severity of OA at higher cartilage AGE levels and provide the first in vivo experimental evidence for a molecular mechanism by which aging may predispose to the development of OA.The population of Western society is aging rapidly. Consequently, age-related diseases will increase greatly over the coming decades and will have a great impact on the quality of life of the elderly. Osteoarthritis (OA) is one of the most prevalent and disabling chronic conditions affecting the elderly and poses a significant public health problem (1). The most prominent feature of OA is the progressive destruction of articular cartilage, resulting in impaired joint motion, severe pain, and, ultimately, disability (2). As yet, the etiology of OA remains largely unknown. The incidence of OA increases with age: Ͼ50% of the population over 60 years of age is affected (3,4). Although age is identified as the main risk factor for the development of OA, the mechanism by which aging is involved remains unclear. Age-related changes in the articular cartilage are expected to play an important role in the susceptibility of cartilage to OA.Articular cartilage derives its mechanical properties from its extracellular matrix. This matrix is composed of type II collagen, which forms a 3-dimensional network that provides the cartilage with resistance to tensile forces (5).

Although tendon tissue directly adjacent to an Achilles tendinosis lesion looks macroscopically healthy, histological and biochemical degenerative changes in adjacent tissue are evident, which may have implications for surgical interventions.

Synovial fluid potentially contains markers for early diagnosis and disease progression in degenerative joint diseases such as osteoarthritis. Here, a method is described for profiling endogenous peptides in human synovial fluid, using ultrafiltration, solid-phase extraction, nanoscale liquid chromatography, and high-resolution mass spectrometry. Synovial fluid is characterized by its high viscosity, caused by the presence of the lubricant hyaluronic acid. The method proved to be capable of eliminating the high concentrations of hyaluronic acid, which appeared to be necessary to obtain satisfactory analytical performance, that is, within-day relative standard deviations of 5-15%, between-day relative standard deviations of 6-16%, a linear response of R2=0.994, a limit of detection in the femtomole range, and reproducible recoveries of 14-67%. With the developed method, in a synovial fluid sample from an osteoarthritis patient and a healthy control, in total, 501 peptides originating from 40 proteins were identified. Peptide cleavage products from six proteins that have been associated with osteoarthritis in earlier studies (collagen II, proteoglcycan 4, serum amyloid A, tubulin, vimentin, and Matrix Gla) could also be identified with our profiling method. The robustness of the method indicates that it can be applied in systems biology approaches for further studies on degenerative joint disease, eventually leading to a better understanding of the disease and its therapy, as well as the development of novel biomarkers to monitor these processes.

Objective. The infrapatellar fat pad (IPFP) in the knee joint is hypothesized to contribute to osteoarthritis (OA) development by the IFPF possibly by influencing inflammatory processes. Oxylipins are essential mediators in the inflammatory process. We undertook this study to investigate secretion by the IFPF of fatty acids and oxylipins derived from those fatty acids.Methods. IPFP explants from 13 OA donors undergoing joint replacement surgery and from 10 normal donors postmortem were cultured for 24 hours, and supernatants (fat-conditioned medium [FCM]) were collected. Liquid chromatography tandem mass spectrometry detected fatty acids and oxylipins in FCM samples. Univariate and multivariate (partial leastsquares discriminant analysis [PLS-DA]) analyses were performed, followed by pathway analysis. To validate these outcomes, a second set of OA FCM samples was measured (n ‫؍‬ 23).Results. Twenty-nine oxylipins and fatty acids could be detected in FCM. Univariate analysis showed no differences between normal donor and OA donor FCM; however, PLS-DA revealed an oxylipin/fatty acid profile consisting of 14 mediators associated with OA (accuracy rate 72%). The most important contributors to the model were lipoxin A 4 (decreased), thromboxane B 2 (increased), and arachidonic acid (increased). The statistical model predicted 64% of the second set of OA FCM samples correctly. Pathway analysis indicated differences in individual mediators rather than in complete pathways. Conclusion. The IPFP secretes multiple and different oxylipins, and a subset of these oxylipins provides a distinctive profile for OA donors. It is likely that the observed changes are regulated by the OA process rather than being a consequence of basal metabolism changes, as an increase in fatty acid levels was not necessarily associated with an increase in oxylipins derived from that fatty acid.

Corticosteroids may weaken specific regions of the injected tendon and leave it more prone to rupture. This weakening effect is manifested in the individual collagen fascicles that constitute the tendon.

Objective-To investigate the role of stromelysin (MMP-3) activity in synovial fluid (SF) at diVerent 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 suVering 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 diVerent 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 diVerentiation 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. (Ann Rheum Dis 2000;59:155-157) Matrix metalloproteinases (MMPs) have an integral role in connective tissue turnover. Collagenases (MMP-1, -8 and 13) cleave interstitial collagen triple helices. Gelatinases (MMP-2, and -9) act mainly on unwound collagen and gelatin. Stromelysins (MMP-3, -10 and -11) can degrade proteoglycans, collagen types IX, XI and type II N-telopeptides, and participate in the activation of proMMP-1, -8, -9 and -13. Membrane-type MMPs are able to activate proMMP-2.1-3 MMPs are present mainly in inactive form (> 95% of total), which is either the latent proform, or an inhibited complex with tissue inhibitor of metalloproteinases (TIMPs) or alpha-2-macroglobulin.

Stromelysin-1 (MMP-3) is an important member of the matrix metalloproteinase family. In joint-degrading diseases like arthritis, elevated levels of MMP-3 protein are detected in synovial fluid using iimnunological methods. However, these methods do not discriminate between active and inactive enzyme. In the present study, a specific stromelysin activity assay was developed using the selective fluorogenic substrate TNO003 (Dabcyl-Gaba-Arg-Pro-Lys-Pro-Val-Glu ♦ Nva-Trp-Arg-Glu-(EDANS)-Ala-Lys-NH 2 , ♦= cleavage site). For its use in biological media, cleavage of TNO003 by enzymes other than stromelysin was effectively blocked by a proteinase inhibitor cocktail. Spiking of MMP-3 to synovial fluid resulted in an MMP-3 concentration-dependent linear increase in activity. The measured MMP-3 activity was not affected by the addition of MMP-13, even in a 5-fold excess over MMP-3. Synovial fluid from rheumatoid arthritis patients demonstrated 100-fold higher levels of active stromelysin than control synovial fluids.