Figure 6.

An example image demonstrating the methodology of determining the threshold oxygen tension. The thickness of fibrous collagenous band measured by ImageJ image analysis, color intensity profile and the O₂ tension profile of Day-21 cartilaginous pellets were used for the extrapolation of the threshold oxygen tension. In this example (patient M69, initial cell seeding number = 2 × 10⁵), the average measured radius of pellets was 0.0583 cm. The average fibrous band thickness measured by ImageJ was 0.0115 cm. Therefore, the inner edge of collagen-rich fibrous band, that is, boundary between PG- and collagen-rich matrix, intersected at a distance of 0.0583 − 0.0115 = 0.0468 cm from the centre of the pellet. The threshold oxygen tension was then determined by reading the value of oxygen tension (1.10 × 10⁻⁷ mol cm⁻³) from the predicted oxygen tension profile at 0.0468 cm in this particular example. Three measurements were performed for each cell seeding number of each patient.