Real-time monitoring of metabolic function in liver-on-chip microdevices tracks the dynamics of mitochondrial dysfunction

TLDR

Microfluidic organ‑on‑chip platforms aim to replace animal toxicity testing, yet they have shown limited advantages, and current assays for mitochondrial dysfunction rely on end‑point measurements that miss kinetic and prognostic information. The study introduces a liver‑on‑chip device that sustains human liver tissue for over a month and uses it to quantify how cells adapt to mitochondrial damage and redistribute ATP production. Mitochondrial respiration is monitored in real time with two‑frequency phase‑modulated phosphorescent microprobes, while a computer‑controlled microfluidic switchboard simultaneously measures glucose and lactate to detect shifts from oxidative phosphorylation to anaerobic glycolysis. The platform shows that troglitazone at previously considered safe concentrations alters metabolic fluxes, providing a possible mechanism for its idiosyncratic toxicity, and it uniquely captures the dynamics of cellular adaptation to mitochondrial damage.

Abstract

Microfluidic organ-on-a-chip technology aims to replace animal toxicity testing, but thus far has demonstrated few advantages over traditional methods. Mitochondrial dysfunction plays a critical role in the development of chemical and pharmaceutical toxicity, as well as pluripotency and disease processes. However, current methods to evaluate mitochondrial activity still rely on end-point assays, resulting in limited kinetic and prognostic information. Here, we present a liver-on-chip device capable of maintaining human tissue for over a month in vitro under physiological conditions. Mitochondrial respiration was monitored in real time using two-frequency phase modulation of tissue-embedded phosphorescent microprobes. A computer-controlled microfluidic switchboard allowed contiguous electrochemical measurements of glucose and lactate, providing real-time analysis of minute shifts from oxidative phosphorylation to anaerobic glycolysis, an early indication of mitochondrial stress. We quantify the dynamics of cellular adaptation to mitochondrial damage and the resulting redistribution of ATP production during rotenone-induced mitochondrial dysfunction and troglitazone (Rezulin)-induced mitochondrial stress. We show troglitazone shifts metabolic fluxes at concentrations previously regarded as safe, suggesting a mechanism for its observed idiosyncratic effect. Our microfluidic platform reveals the dynamics and strategies of cellular adaptation to mitochondrial damage, a unique advantage of organ-on-chip technology.