Real-Time Monitoring of the Metabolic Fingerprint of ER Stress in a Human Liver-On-Chip Microphysiological Platform

The Endoplasmic Reticulum (ER) is central into a multitude of diverse cellular functions, such as protein folding, calcium and lipid homeostasis. Perturbation of the ER function leads to stress and the Unfolded Protein Response (UPR), a signaling cascade that stands in the crossroad of rebalance or apoptosis upon prolonged stress. Both outcomes of UPR are equally implicated in health and disease, making the capacity to diagnose and monitor ER stress all the more important. Thapsigargin is an anti-cancer drug, which disrupts ER calcium stores through SERCA pump inhibition and induces ER stress. We recently presented our novel liver-on-chip microphysiological platform and attested to its capacity to provide accurate and predictive metabolic fingerprints of drug-induced perturbations in in vitro models of human hepatocytes. By utilizing said platform we were able to use both thapsigargin and tunicamycin, another widely used ER stress/UPR inducer, along with the E6/E7^LOW human hepatocytes (UpCytes), a robust, superior cell model of human hepatocytes, to record the metabolic effects of ER stress in real-time. Moreover, correlating our detailed metabolic and oxygen consumption data with calcium and mitochondria polarization monitoring, as well as UPR reporting we are able to provide an integrative toxicity pathway, tracing in a timely fashion the key cellular structures it propagates through and its telltale effects on the metabolic fluxes.