Research ArticleBone

Radiocarbon dating reveals minimal collagen turnover in both healthy and osteoarthritic human cartilage

Science Translational Medicine  06 Jul 2016:
Vol. 8, Issue 346, pp. 346ra90
DOI: 10.1126/scitranslmed.aad8335

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Cartilage claims a permament home

It has long been debated for many tissues in our bodies whether they are permanent or constantly refreshed as we go through life. Nuclear bomb testing in the 1950s and 1960s released a large amount of the carbon-14 isotope into the atmosphere, giving researchers the ability to determine the age and turnover of human tissues, ranging from the heart to the brain to, now, the cartilage. Heinemeier and colleagues used this so-called “14C bomb pulse” method to date cartilage from 23 individuals ranging from 18 to 76 years of age. They examined cartilage from knee joints, taking samples from both highly and moderately loaded areas, in both healthy individuals and those with osteoarthritis. The authors discovered that the collagen matrix of human cartilage is essentially permanent, with no major replacement even with disease. This finding has important implications for the tissue engineering and regenerative medicine fields, where the structural permanence of collagen will need to be contemplated when designing new cartilage repair strategies.

Abstract

The poor regenerative capacity of articular cartilage presents a major clinical challenge and may relate to a limited turnover of the cartilage collagen matrix. However, the collagen turnover rate during life is not clear, and it is debated whether osteoarthritis (OA) can influence it. Using the carbon-14 (14C) bomb-pulse method, life-long replacement rates of collagen were measured in tibial plateau cartilage from 23 persons born between 1935 and1997 (15 and 8 persons with OA and healthy cartilage, respectively). The 14C levels observed in cartilage collagen showed that, virtually, no replacement of the collagen matrix happened after skeletal maturity and that neither OA nor tissue damage, per se, influenced collagen turnover. Regional differences in 14C content across the joint surface showed that cartilage collagen located centrally on the joint surface is formed several years earlier than collagen located peripherally. The collagen matrix of human articular cartilage is an essentially permanent structure that has no significant turnover in adults, even with the occurrence of disease.

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