Abstract
Metabolic (dysfunction)-associated steatotic liver disease is the hepatic consequence of metabolic syndrome affecting 30% of the global population. Dietary fructose has been reported to induce steatosis in animal models, with discordant results in human trials. Liver-on-a-chip technology aims to bridge the gap between traditional in vitro and in vivo models by culturing cells in microchannels under microfluidic flow. This work aimed to determine the effect of fructose on lipid accumulation in Emulate S-1 organ-chips seeded with human HepG2 cells and compare results to traditional 2D culture models. Three independent replicates of each experiment were performed.
Over 72 h, the concentration of fructose in media collected from blank chips did not differ to the concentration added (20 mM), as detected by ultra-high performance liquid chromatography tandem mass spectrometry. HepG2 cells (5x105 cells/mL) were then seeded in the chips and exposed to fructose (20 mM) for 72 h. The concentration of triglycerides and cholesterol released from cells was quantified using commercially available kits. No significant difference was detected between fructose treated and the vehicle treated conditions (9.5±1.6 µg/mL cholesterol, 6.7±1.2 mg/dL triglycerides, P>0.05). The lipid content of these cells was quantified using confocal microscopy and automated image analysis. The number of lipid droplets (4±2.5 droplets/cell), as well as the lipid droplet surface area (28±8 µm2) and fluorescent intensity (344±219 fluorescent units) were unaffected by fructose exposure (P>0.05). Differences between the chip assay and the 2D plate assay included 2.4-fold higher albumin secretion in the chips, and 8.8-fold larger lipid droplets in the plates, however, these differences were not formally compared.
This work demonstrated that in HepG2 cells, fructose was not lipogenic in a complex liver-on-a-chip device. Establishing this technology in New Zealand is an important step. Future experiments utilising primary cells will provide the best platform to model the human liver in vitro.