Role of Osteoblasts in Abnormal Bone Tissue Metabolism in OA

The hypothesis that OA may be considered a metabolic disease in which systemic or local factors modify the formation and activity of mesenchymal precursor cells in skeletal tissues is an attractive one 5 . Because OA osteoblasts show increased osteocalcin and alkaline phos-phatase levels in vitro 100,101 and in situ 80 , the in vivo alterations are likely due to changes in abnormal cellular metabolism and not to changes in systemic regulation. However, this does not mean that local autocrine...

Dedifferentiation of Chondrocytes in Osteoarthritis

Articular chondrocytes are subject to pheno-typic destabilization during a variety of pathologic conditions 120 . With the onset of OA, chondrocytes undergo metabolic changes that involve newstimuli (proinflammatory cytokines, growth factors) and changes in the composition of the extracellular cartilage matrix (ECM) 155 . As their normal phenotype changes, chondrocytes even express traits of transient growth such as hypertrophy, alkaline phosphatase, type X collagen, and mineralization 151,236...

Bone Tissue Changes in Osteoarthritis

Many studies have explored the structural changes that take place in subchondral bone during the evolution of OA,with symptoms paralleling disease progression. Epidemiologic studies have demonstrated that as subchondral bone becomes sclerotic, the disease worsens 131 . Even though clinical data are largely based on noninvasive technology, such as x-rays, computed tomography (CT) scans, magnetic resonance imaging (MRI), scintigraphy, and biomarkers, Buckland-Wright et al 24-27 have shown with...

Role of Bone Tissue in Osteoarthritis Progression or Initiation

The most important feature of OA is that structural changes in the joint involve the major constituents of articulation including subchondral bone. Whether these changes affect cartilage before reaching subchondral bone or vice versa is still a matter of debate. Resolution of this question is likely to modify knowledge of the disease and potential treatment. There is increasing evidence that crosstalk between cartilage and subchon-dral bone is an integral part of the disease process 70,129,180...

Structure Function Relationship in Articular Cartilage

Water Articular Cartilage

To understand cartilage degradation, one must understand the structure-function relationships of this tissue. Human articular cartilage consists of a hydrated extracellular matrix in which a comparatively small number of chon-drocytes is embedded (< 3 of total tissue volume Fig. 1.4). The extracellular matrix is the functional element of the tissue, and all its components are required for the articular cartilage to act as a shock absorber. However, it is the chondrocytes that are the active...

Implication of Biomechanical Processes in Osteoarthritis

That OA is due to altered biomechanical function has been widely discussed, but may not be a basic cause. An example is obesity, an important risk factor for OA, where the impact causing joint overload is associated with radio-graphically denser bones 67,76,77,123 . It may, however, be the metabolic consequences of obesity that are responsible for disease progression. Joint location and cartilage matrix vulnerability to chemical and mechanical injury are highly correlated with the risk of...