EPR oxygen mapping (EPROM) of engineered cartilage grown in a hollow-fiber bioreactor

A novel electron paramagnetic resonance (EPR)-based oxygen mapping procedure (EPROM) is applied to cartilage grown in a single-, hollow-fiber bioreactor (HFBR) system. Chondrocytes harvested from the sterna of 17-day-old chick embryos were inoculated into an HFBR and produced hyaline cartilage over a period of 4 weeks. Tissue oxygen maps were generated according to the EPROM technique (Velan et al., Magn Reson Med 2000;43:804-809) by making use of the line-broadening effects of oxygen on the signal generated from nitroxide spin probes. In addition, the effect on oxygen consumption of the addition of cyanide to the tissue was investigated. Cyanide is a potent inhibitor of oxidative phosphorylation, and accordingly, given the constant provision of oxygen to the tissue, it would be expected to increase oxygen levels within the HFBR. The EPROM measurements showed a significant increase in oxygen concentration in the cartilage after the addition of cyanide. In contrast to other methods for studying oxygen in cartilage, EPROM can provide direct, noninvasive visualization of local concentrations in three dimensions.