Doctoral Researcher Tampere University Tampere, Finland
Abstract: Atmospheric oxygen levels differ significantly from tissue-specific physioxia; for example, the liver consists of hepatic lobules exhibiting physiological oxygen gradients that greatly influence cellular functionality. Our study aims to emulate the hepatic microenvironment and enhance the maturation of induced pluripotent stem cell-derived hepatocyte-like cells (iPSC-HLCs) by culturing the cells under varied oxygen concentrations.
To expose the differentiating cells to specific oxygen concentrations within a physiologically relevant range, we culture them in 1-well culture chambers (BioGenium Microsystems), which are connected to a gas supply. The culture chambers are coated with an oxygen-sensing film, allowing quantitative assessment of the oxygen microenvironment during the culture period. Initially, we introduced oxygen stimulation on day 12 of iPSC-HLC differentiation. In subsequent experiments, we progressively adjusted the start of physioxic oxygen exposure, starting with day 8 and later including even earlier time points.
Our analyses indicate enhanced functionality of the iPSC-derived hepatocytes, demonstrated by increased secretion of liver-specific factors such as albumin and urea, alongside upregulated expression of key hepatic genes, even in the absence of media perfusion or 3D culture conditions. The timing of oxygen stimulation initiation appears to have a greater impact on, for example, albumin secretion, compared to the tested range of oxygen concentrations. Additionally, ratiometric oxygen imaging reveals that the oxygen concentration experienced by the cells differs from the set gas level, emphasising the importance of oxygen monitoring during the culture period.
Our research highlights how altering a single physical parameter, such as oxygen levels, can significantly enhance the functionality of iPSC-derived cells. Our simple, yet impactful approach ultimately aims to contribute to a more accurate representation of human liver physiology.
