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.