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).

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.