Oxygen Gradients in Cartilage Explants and Cartilagineous Constructs: Modelled and Measured

Introduction Articular cartilage lacks the ability to sufficiently repair itself. Tissue engineering approaches may initiate functional repair and, therefore, are considered for the treatment of articular cartilage defects. Our method adopts a porous PEGT/PBT scaffold (PolyActive, IsoTis N.V.) with similar mechanical properties to native cartilage, which acts as a 3 dimensional carrier for seeding autologous chondrocytes and subsequent in vitro tissue culture. Previously reported studies have shown the onset of chondrogenesis at the peripheral boundaries of “tissue engineered” (TE) constructs (1). The absence of cartilage specific matrix components within the middle of these constructs at early time points could be due to inhomogeneous seeding or limitations in nutrient supply. We hypothesize that oxygen contributes to one of the rate-limiting steps for chondrogenesis and is, therefore, considered as an important factor during the culture of TE cartilage constructs. The measurement of the oxygen supply to chondrocytes in cartilage is complicated by a number of factors, such as, determination of the gaseous diffusion through the extra cellular matrix (ECM) and the technical challenge of determining the local oxygen tension. We determined the gaseous diffusion through the ECM using a diffusion cell and overcame the physical problem of measuring the local oxygen concentration by using an adapted microelectrode system. We recently showed that oxygen gradients within cartilage explants and TE constructs can be measured with this microelectrode system with high reproducibility and high spatial resolution (2). In order to obtain a greater insight into the relationship between chondrogenesis and oxygen tension, the aim of this study was to describe oxygen gradients within cartilage explants and TE constructs using a mathematical model.