Cartilage Redox Balance Is Influenced by Substrate Availability

Purpose The mechanobiological response of cartilage redox balance might change in response to altered substrate availability. The purpose of this study is to investigate effects of key metabolic substrates (glucose, glutamine, and oxygen) on the mechanoresponsiveness of cartilage redox balance using a label-free imaging technique that measures autofluorescence from endogenous redox cofactors. Findings Compared with room oxygen tension, low oxygen tension had higher autofluorescence intensity in green (FAD) channel after a single sub-failure tensile load. Cartilage explants cultured in high glucose medium with glutamine supply had higher autofluorescence intensity in both channels (FAD and NADH/NADPH) compared with low glucose with glutamine group or high glucose without glutamine group, while no difference was observed between the latter 2 groups. Conclusions Low oxygen tension or high glucose culture medium with glutamine supply increases the mechanoresponsiveness of cartilage redox balance induced by sub-failure mechanical loading. Glutamine appears to partially serve as a glucose substitute in this process.