Influence of stirring-induced mixing on cell proliferation and extracellular matrix deposition in meniscal cartilage constructs based on polyethylene terephthalate scaffolds

The response of engineered meniscal cartilage constructs to stirring-induced mixing in spinner flasks was investigated. Polyethylene terephthalate scaffolds were seeded with meniscal fibrochondrocytes from 6 month-old sheep and cultured under a variety of stirring regimes for 28 days. Stirring-induced mixing increased up to 7-fold the deposition of glucosaminoglycans and up to 3-fold the deposition of collagen, when compared to static cultures. High and medium intensity stirring induced rapid cell proliferation, with maximal cell densities achieved within the first seven days of cultivation. Under these conditions, collagen and glucosaminoglycan deposition occurred predominantly in association with cell proliferation, the specific deposition rate of these biopolymers decreasing markedly after 7 days of cultivation, when the cell number reached a plateau. Constructs exposed to the highest intensity stirring had the highest levels of collagen and glucosaminoglycans and a more homogeneous cell distribution. As the success of the integration at a repair site in the knee of a meniscal construct is likely to be dependent on the cellular activity of the construct, these studies suggest that cultivation of meniscal cartilage constructs, under these conditions, should not extend for more than 7 days.