Cartilage has no blood supply. How are its cells fed?
Articular cartilage has no blood vessels, lymphatics or nerves. Its cells, which make up about 2% of its volume, are fed by the movement of water through the tissue as it is compressed and released, which carries nutrients to them (Sophia Fox 2009). Living without a blood supply also means the cells must make their own protection, including glutathione (Stegen 2020).
A tissue with no pipes
Articular cartilage is the smooth layer on the ends of bones in a joint. It is devoid of blood vessels, lymphatics and nerves, and it has a limited capacity to heal (Sophia Fox 2009). Water makes up about 80% of the tissue near the surface and about 65% in the deep zone, and its flow through the matrix helps carry nutrients to the cells (Sophia Fox 2009).
Few cells, big job
Chondrocytes make up only about 2% of cartilage by volume, and each one maintains the matrix in its immediate surroundings (Sophia Fox 2009). If a cell is lost, the tissue around it loses its keeper.
Why that makes glutathione matter
Without a blood supply, cartilage cells have to manage their own metabolism and defences. In growth-plate cartilage, glutathione made from glutamine kept reactive oxygen species from building up and allowed the cells to survive in that avascular environment (Stegen 2020). In human chondrocytes, the cells' glutathione status tracked how well they survived oxidant stress (Del Carlo 2003).
Other questions people ask
Does that mean cartilage can't repair itself?
Its capacity for intrinsic healing and repair is limited, which is why preserving it matters (Sophia Fox 2009).
Sources
- Sophia Fox AJ, Bedi A, Rodeo SA. The basic science of articular cartilage: structure, composition, and function. Sports Health 2009.
- Stegen S, Rinaldi G, Loopmans S et al. Glutamine Metabolism Controls Chondrocyte Identity and Function. Dev Cell 2020.
- Carlo MD Jr, Loeser RF. Increased oxidative stress with aging reduces chondrocyte survival: correlation with intracellular glutathione levels. Arthritis Rheum 2003.
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