Effect of nutrient metabolism on cartilaginous tissue formation

A major shortcoming in cartilage tissue engineering is the low biosynthetic response of chondrocytes. While different strategies have been investigated, a novel approach may be to control nutrient metabolism. Although known for their anaerobic metabolism, chondrocytes are more synthetically active under conditions that elicit mixed aerobic–anaerobic metabolism. Here, we postulate this metabolic switch induces HIF‐1α signaling resulting in improved growth. Transition to different metabolic states can result in the pooling of metabolites, several of which can stabilize HIF‐1α by interfering with PHD2. Chondrocytes cultured under increased media availability accelerated tissue deposition with the greatest effect occurring at 2 ml/106 cells. Under higher media availability, metabolism switched from anaerobic to mixed aerobic‐anaerobic. Around this transition, maximal changes in PHD2 activity, HIF‐1α expression, and HIF‐1 target gene expression were observed. Loss‐of‐function studies using YC‐1 confirmed the involvement of HIF‐1. Lastly, targeted metabolomic studies revealed that intracellular lactate and succinate correlated with PHD2 activity. This study demonstrates that cartilaginous tissue formation can be regulated by nutrient metabolism and that this response is mediated through changes in HIF‐1α signaling. By harnessing this newly identified metabolic switch, engineered cartilage implants may be developed without the need for sophisticated methods which could aid translation to the clinic. A novel approach to improve the growth of tissue‐engineered cartilage was developed in this study based on controlling nutrient metabolism. By culturing cartilage cells at the transition between anaerobic and aerobic metabolism, tissue growth was significantly improved, and this effect was induced by HIF‐1α signaling. By harnessing this metabolic switch, there is the potential to develop engineered cartilage implants without the need for sophisticated methods and aid in translation to the clinic.