Katopodi T, Tew SR, Clegg PD, Hardingham TE (2009). The influence of donor and hypoxic conditions on the assembly of cartilage matrix by osteoarthritic human articular chondrocytes on Hyalograft matrices. Biomaterials, 30(4):535-40.pubmed
Imagine a world where worn out or diseased tissues can be replaced with new fully functioning tissue, which does not provoke an adverse immune response. This is the ultimate goal for tissue engineering - to replace or enhance tissue function, especially that which has been impaired by disease, injury, or age. For tissue regeneration to become a reality, researchers must first decipher the conditions that are necessary to stimulate cells into producing specific tissue types. This remains a major challenge for tissue engineering research.
Whilst some tissues have a relatively high capacity for regeneration, for example the liver, other types have limited or no regenerative capability. The cartilage surrounding bone ends (articular cartilage) is one such tissue. Articular cartilage does not naturally contain blood vessels, and is therefore a hypoxic (low oxygen) environment. This means that in vivo cells are surrounded by low levels of oxygen. This study shows that by growing cartilage cells in hypoxic conditions, and thus reproducing the natural oxygen levels of cartilage tissue, the amount of cartilage-like structures that they produce can be significantly increased compared to cells grown in higher oxygen conditions. This finding is significant because cartilage cells are typically cultured under highly oxygenated conditions.
The authors also demonstrate that cartilage cells collected from different donors have different cartilage-like structure producing capabilities. In fact, the difference in amounts of cartilage structures produced by cells from different donors is so great, that it far exceeds the differences seen between cells exposed to hypoxic and non hypoxic conditions. This shows that the donors used for cartilage cell harvesting have a very significant impact on the amount of cartilage-like tissue that can be produced.
In summary, this paper highlights two important factors that effect cartilage tissue engineering. The first is that cartilage cells produce greater amounts of cartilage-like structures under hypoxic conditions compared to oxygenated conditions. The second is that some donor cells produce more cartilage structures than others. This observation will need further investigation to find out if the differences can be attributed to donor characteristics such as gender, age or race. These findings bring us closer to understanding the mechanisms controlling cartilage tissue regeneration. Determining the optimum conditions for cartilage tissue regeneration will enable researchers to ultimately engineer cartilage for the treatment of diseased or damaged tissue; for example, in the treatment of osteoarthritis, which is a progressively painful condition that affects articular cartilage of joints.