HepaRG

HepaRG cell line is a human hepatic in vitro line used in liver biology research and for assessing liver pathology, hepatotoxicity, and drug-induced injury. The HepaRG model is considered a surrogate for Primary Human Hepatocytes, which are the most pertinent model to reproduce the human liver functioning as they express 99% of the same genes.

In contrast to the historic hepatic line HepG2, HepaRG cells preserved various liver-specific functions, including the expression of CYP enzymes and transporters, the formation of bile canaliculi, and, the ability to be applied in 2D and 3D configuration.

History
In 1999, Dr. Christiane Guguen-Guillouzo and Dr. Christian Trépo collaborated on a medical and scientific project. During the course of their research, a tumor sample from a patient with cholangiocarcinoma and HCV was given to Sylvie Rumin to study hepatitis infection. Rumin observed a group of cells that resembled hepatic cells and gradually lost HCV infection markers. Philippe Gripon later developed these cells, finding that they had the ability to undergo complete hepatocyte differentiation while retaining all liver-specific functions. As a way to honor the contributions of Rumin and Gripon, the cells were named HepaRG, using the first letter of their last names. Since their discovery, many scientists characterized and used the HepaRG model in their studies.

Characterization
HepaRG cells are bipotent progenitors, capable of differentiating into both biliary and hepatocyte lineages. In culture, they are organized in well-delineated trabeculae with many bright canaliculi-like structures under 2D and 3D configurations. They are polarized cells that breathe aerobically, consume lactate, and contain as many mitochondria as the human hepatocytes. The cell line has the potential to express major properties of stem cells including high plasticity & transdifferentiation capacity.

The HepaRG cells have been found to express major nuclear receptors, as well as drug and bile acids transporters, and key hepatic nuclear factors. They also possess functional levels of phase I (CYP (CYP1A1/2, CYP2B6, CYP2Cs, CYP3A4, etc.) and II (UGT1A1, GSTA1, GSTA4, GSTM1) drug metabolizing enzymes. Additionally, the HepaRG cells have functional mitochondria, hepatokine secretion abilities, and a suitable response to insulin.

One unique characteristic of HepaRG cells is that they can survive up to four weeks in culture, making them useful for long-term studies and repeated exposures to drugs and chemicals, unlike primary human hepatocytes. Moreover, the cells can be infected by HBV and HCV and support viral replication. The cells are available as undifferentiated growth-stage cells that can be grown in-house with the possibility of cell manipulation and amplification; or as fully differentiated cells that are ready and easy-to-use cells with high inter-assay reproducibility and proven functionality across multiple applications. They can also be used as spheroids and co-culture.

Use in research
HepaRG cells are considered fit-for-all-purpose cells as they were used in many applications ranging from drug development, drug metabolism and interaction assessment, chemical testing, assay validation, hepatotoxicity assessments, liver Biology, liver disease characterization, and virology studies.

Basic research
HepaRG cells are a versatile tool for modeling various viral and parasitic infections such as hepatitis B virus (HBV), hepatitis C virus (HCV), hepatitis E virus (HEV), and hepatitis delta virus (HDV).

They are also useful for studying the interconnected pathways involved in carbohydrate homeostasis and lipid metabolism. In contrast to many other cell lines, HepaRG cells are capable of regulating glycogenolysis and gluconeogenesis at levels similar to primary human hepatocytes, as well as retaining the response mechanisms associated with lipid-metabolizing enzymes.

Medical applications
HepaRG cells have shown potential in the field of regenerative medicine, specifically in the development of bio-artificial livers and liver-assisting devices due to their ability to be cultured in 3D bioreactors.

A study demonstrated that HepaRG cells can be incorporated into a microfluidic system to form a functional bio-artificial liver capable of detoxifying ammonia and other harmful substances. In another study, a modular extracorporeal liver support system, which combines HepaRG cells with a bioartificial scaffold was created to support liver function. This system was shown to be effective in removing toxins from the blood and supporting liver function in animal models.

Industrial applications
HepaRG is owned by the French National Institute of Health and Medical Research (INSERM) and since 2003, Biopredic International acquired the license of the cells and settled both the master and the working banks for preserving the stability of the line.

In vitro-ADME applications
HepaRG cells have many applications in in-vitro ADME (absorption, distribution, metabolism, and excretion) studies. They were used to study drug metabolism and toxicity, including phase I and phase II enzyme metabolism, induction, and inhibition. Moreover, HepaRG cells have been used to study drug transporters, measure compound clearance, and predict metabolic stability as well as drug-drug interactions. Additionally, HepaRG has been used to evaluate acute and chronic drug toxicity, genotoxicity, and hepatotoxicity.

The high reproducibility of the drug-induced metabolic enzyme levels between batches enables routine high-throughput analysis of compound clearance.

Hepatotoxicity screening and mechanistic testing
HepaRG cells have been utilized for assessing drug-induced liver injury (DILI), including steatosis, cholestasis, and phospholipidosis, as well as for evaluating genotoxicity and carcinogenicity. Additionally, they have been employed for studying drug-induced mitochondrial toxicity, apoptosis, and inflammation. HepaRG cells are advantageous for uptake and biliary secretion studies due to their expression of various uptake and efflux drug transporters, and the formation of tight junctions and bile canaliculi.

For instance, HepaRG cells have been used to evaluate the hepatotoxicity of compounds in drug development, such as acetaminophen, troglitazone, and valproic acid, as well as environmental toxins like aflatoxin B1 and ethanol.