Growth of cartilage explants in long-term: free-swelling culture: biochemical and tensile biomechanical properties

Articular cartilage mechanical properties and biochemical composition evolve during in utero development and in vivo growth, with marked differences between the fetus, newborn, and young adult. The objective of this study was to establish an in vitro system to assess the factors that regulate such growth, in particular by characterizing the growth of fetal and newborn bovine articular cartilage explants during 6 weeks of free-swelling culture in serum-supplemented medium. During this culture period, both fetal and calf cartilage grew markedly in size, increasing in cell and matrix components. While the tensile modulus, strength and stiffness of calf cartilage were initially higher than those of fetal cartilage, the tensile properties of both types of cartilage explants fell, to similarly low levels, during the culture period. The increase in cells and matrix, but diminution rather than increase in tensile properties, suggests that regulatory factors other than serum, may trigger the biomechanical maturation of articular cartilage in vivo.