Conclusions
The results of this study demonstrate that cartilaginous tissue formation can be upregulated through the control of nutrient metabolism and that the observed response is mediated through resultant changes in HIF-1α signalling. By culturing in elevated volumes of media, glucose uptake by chondrocytes is increased, leading to a change in metabolism from primarily anaerobic to mixed aerobic-anaerobic (inverse Crabtree effect ). When cultured at the transition between metabolic states, a pseudo-hypoxic state is induced resulting in HIF-1α mediated gene transcription and an associated increase in chondrogenesis. These findings represent a novel, paradigm-shifting approach to develop functional engineered cartilage implants that can be produced without sophisticated stimulation methods. The developed methodology is highly transferable and can be applied to any cartilage tissue engineering approach. Such methods are attractive as they have fewer regulatory barriers to aid commercialization efforts, thereby allowing for improved clinical translation. Additionally, these newly identified metabolic pathways could potentially provide insights into the mechanisms of cartilage growth and development. Future avenues of research will include metabolic modelling (e.g. 13C flux analyses) to provide a framework to control chondrogenesis.