Microphysiological flux balance platform unravels the dynamics of drug induced steatosis

Abstract

Drug development is currently hampered by the inability of animal experiments to accurately predict human response. While emerging organ on chip technology offers to reduce risk using microfluidic models of human tissues, the technology still mostly relies on end-point assays and biomarker measurements to assess tissue damage resulting in limited mechanistic information and difficulties to detect adverse effects occurring below the threshold of cellular damage. Here we present a sensor-integrated liver on chip array in which oxygen is monitored using two-frequency phase modulation of tissue-embedded microprobes, while glucose, lactate and temperature are measured in real time using microfluidic electrochemical sensors. Our microphysiological platform permits the calculation of dynamic changes in metabolic fluxes around central carbon metabolism, producing a unique metabolic fingerprint of the liver's response to stimuli. Using our platform, we studied the dynamics of human liver response to the epilepsy drug Valproate (Depakine™) and the antiretroviral medication Stavudine (Zerit™). Using E6/E7LOW hepatocytes, we show TC50 of 2.5 and 0.8 mM, respectively, coupled with a significant induction of steatosis in 2D and 3D cultures. Time to onset analysis showed slow progressive damage starting only 15-20 hours post-exposure. However, flux analysis showed a rapid disruption of metabolic homeostasis occurring below the threshold of cellular damage. While Valproate exposure led to a sustained 15% increase in lipogenesis followed by mitochondrial stress, Stavudine exposure showed only a transient increase in lipogenesis suggesting disruption of β-oxidation. Our data demonstrates the importance of tracking metabolic stress as a predictor of clinical outcome.

A Human Liver‐on‐a‐Chip Platform for Modeling Nonalcoholic Fatty Liver Disease

“…Another study by Ehrlich et al developed a sensor‐integrated liver on chip array using human liver organoids composed of albumin‐positive E6/E7LOW hepatocytes and endothelial cells, monitoring oxygen while glucose, lactate, and temperature were measured in real time using microfluidic electrochemical sensors. Although the study showed that lipid accumulation is not a result of increased production but rather suppression of fatty acid oxidation, their platform did not focus on steatosis . An in vitro liver model was engineered by Feaver et al by coculturing PHHs, hepatic stellate cells, and macrophages.…”

Quercetin and hydroxytyrosol as modulators of hepatic steatosis: A NAFLD‐on‐a‐chip study

“…In this regard, the emerging organ‐on‐chip (OoC) technology can be the real game‐changer: these platforms represent dynamic cell culture systems that offer great promise for simulating and studying human diseases (Liu et al, 2019; Rothbauer et al, 2019), including NAFLD, at the tissue and organ level (Bovard et al, 2018; Chang et al, 2017; Li, George, Vernetti, Gough, & Taylor, 2018; Lu et al, 2018). Recently, our group and others (Bulutoglu et al, 2019; Ehrlich et al, 2018; Gori et al, 2016; Lee & Sung, 2018) have proposed alternative and more complex models of hepatic steatosis in a microfluidic chip to overcome the bottlenecks and limitations of the canonical in vitro cell culture models.…”

Liver‐on‐a‐Chip Models of Fatty Liver Disease

“…A liver-on-a-chip with four sensors to measure oxygen, lactate, glucose, and temperature was used to estimate central drug flux to determine the mechanism of injury of valproate and stavudine. (32) Both drugs led to dose-dependent damage attributed to lipid accumulation in this translational demonstration. The lack of a multicellular architecture makes it unclear whether these devices can mimic the mechanism and toxicological endpoints of in vivo responses to drugs.…”

“…A liver‐on‐a‐chip with four sensors to measure oxygen, lactate, glucose, and temperature was used to estimate central drug flux to determine the mechanism of injury of valproate and stavudine . Both drugs led to dose‐dependent damage attributed to lipid accumulation in this translational demonstration.…”