Development of a DsRed-expressing HepaRG cell line for real-time monitoring of hepatocyte-like cell differentiation by fluorescence imaging, with application in screening of novel geometric microstructured cell growth substrates.

The bipotent nature of the HepaRG cell line is a unique property among human hepatoma-derived cells. Cell treatment with specific differentiation inducers results in a mixture of hepatocyte- and biliary-like cells, accompanied by upregulation of liver-specific proteins, drug metabolizing enzymes, transcription regulators, membrane receptors or innate immune response effectors. These features make the HepaRG cells a suitable and handy replacement for primary hepatocytes, to study hepatic functions in vitro. However, cell differentiation is a long, variable process, requiring special culture conditions, while the resulting mixed cell populations is usually a major drawback. This process can potentially be controlled by interface characteristics, such as substrate topography. To screen for such novel substrates, we have first developed a new HepaRG cell line, designated as HepaRGDsRed, expressing the reporter gene DsRed. The fluorescent protein was expressed in hepatocyte- and not biliary-like cells, in a differentiation dependent-manner. We have further used replicated microstructured gradients of polydimethylsiloxane (PDMS) that allow three-dimensional manipulation in vitro, to monitor HepaRGDsRed differentiation in real time. We demonstrate that this approach enables the controlled assembly of viable hepatocyte-like cells for functional studies, which can be maintained in culture without loss of differentiation. The regulated expression of the DsRed reporter proved a valuable tool not only for rapid screening of novel cell growth substrates favoring cell differentiation, but also, to enrich the hepatocyte-like cell population by fluorescence-activated cell sorting to investigate liver-specific processes in vitro.