Articular cartilage
Articular cartilage is the smooth, firm tissue that covers the ends of bones where they meet in a joint. It is built from a type II collagen network holding the water-retaining molecule aggrecan.
Also called joint cartilage, hyaline cartilage.
Articular means to do with joints. This cartilage has two main building materials. Collagen, mostly type II, makes up two-thirds of its dry mass (Eyre 2002), and aggrecan gives it resistance to compression (Glasson 2005). A thin calcified layer, which carries collagen X, joins it to the bone underneath (Eyre 2002).
It has a very slow turnover. Radiocarbon dating of knee cartilage found virtually no replacement of the collagen network in adults (Heinemeier 2016), and its collagen half-life has been estimated at 117 years (Verzijl 2000). Turnover may also vary by joint. One study found it highest in the ankle and lowest in the hip (Hsueh 2019). A 2021 review noted that no interventions were available to restore degraded cartilage (Hu 2021).
Oxygen varies through its depth, from about 6% near the surface to about 1% in the deep zone, and cartilage cells behave differently at each level (Jain 2023).
Sources
- Eyre D. Collagen of articular cartilage. Arthritis Res 2002.
- Glasson SS, Askew R, Sheppard B et al. Deletion of active ADAMTS5 prevents cartilage degradation in a murine model of osteoarthritis. Nature 2005.
- Heinemeier KM, Schjerling P, Heinemeier J et al. Radiocarbon dating reveals minimal collagen turnover in both healthy and osteoarthritic human cartilage. Sci Transl Med 2016.
- Verzijl N, DeGroot J, Thorpe SR et al. Effect of collagen turnover on the accumulation of advanced glycation end products. J Biol Chem 2000.
- Hu Q, Ecker M. Overview of MMP-13 as a Promising Target for the Treatment of Osteoarthritis. Int J Mol Sci 2021.
- Jain L, Bolam SM, Monk AP et al. Differential Effects of Hypoxia versus Hyperoxia or Physoxia on Phenotype and Energy Metabolism in Human Chondrocytes from Osteoarthritic Compared to Macroscopically Normal Cartilage. Int J Mol Sci 2023.
- Hsueh MF, Önnerfjord P, Bolognesi MP et al. Analysis of "old" proteins unmasks dynamic gradient of cartilage turnover in human limbs. Sci Adv 2019.
Related terms
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