Long-term stability of primary rat hepatocytes in micropatterned cocultures.

Primary hepatocytes display functional and structural instability in standard monoculture systems. We have previously developed a model in which primary hepatocytes are organized in domains of empirically optimized dimensions and surrounded by murine embryonic fibroblasts (HepatoPac™). Here, we assess the long-term phenotype of freshly isolated and cryopreserved rat hepatocytes in a 96-well HepatoPac format. The viability, cell polarity (actin microfilaments, bile canaliculi), and functions (albumin, urea, Phase I/II enzymes, transporters) of fresh and cryopreserved rat hepatocytes were retained in HepatoPac at similar levels for at least 4 weeks as opposed to rapidly declining over 5 days in collagen/Matrigel™ sandwich cultures. Pulse or continuous exposure of rat HepatoPac to GW-7647, a selective agonist of PPARα, caused reproducible induction of CYP4A1 and 3-hydroxy-3-methylglutaryl-CoA synthase over 4 weeks. In conclusion, rat HepatoPac in a 96-well format can be used for chronic dosing of highly functional hepatocytes and assessment of perturbed hepatocellular pathways.

Micropatterned primary hepatocyte co-culture (HEPATOPAC) for fatty liver disease modeling and drug screening.

Non-alcoholic fatty liver disease (NAFLD) is a highly prevalent, progressive disorder and growing public health concern. To address this issue considerable research has been undertaken in pursuit of new NAFLD therapeutics. Development of effective, high-throughput in vitro models is an important aspect of drug discovery. Here, a micropatterned hepatocyte co-culture (MPCC) was used to model liver steatosis. The MPCC model (HEPATOPACTM) is comprised of hepatocytes and 3T3-J2 mouse stromal cells plated onto a patterned standard 96-well or 24-well plate, allowing the cultures to be handled and imaged in a standardized multi-well format. These studies employed high content imaging (HCI) analysis to assess lipid content in cultures. HCI analysis of lipid accumulation allows large numbers of samples to be imaged and analyzed in a relatively short period of time compared to manual acquisition and analysis methods. Treatment of MPCC with free fatty acids (FFA), high glucose and fructose (HGF), or a combination of both induces hepatic steatosis. MPCC treatment with ACC1/ACC2 inhibitors, as either a preventative or reversal agent, showed efficacy against FFA induced hepatic steatosis. Drug induced steatosis was also evaluated. Treatment with valproic acid showed steatosis induction in a lean background, which was significantly potentiated in a fatty liver background. Additionally, these media treatments changed expression of fatty liver related genes. Treatment of MPCC with FFA, HGF, or a combination reversibly altered expression of genes involved in fatty acid metabolism, insulin signaling, and lipid transport. Together, these data demonstrate that MPCC is an easy to use, long-term functional in vitro model of NAFLD having utility for compound screening, drug toxicity evaluation, and assessment of gene regulation.