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HepaChip: a promising tool for assessing adverse drug effects

Liver damage is one of the most common adverse drug effects. Since results obtained with animal experiments can only be transferred to the situation in humans to a limited extent, there is a need for cell-based systems that model human organ function as closely as possible. The new HepaChip, developed by researchers at the NMI in Reutlingen on the basis of human liver and endothelial cells is able to do just this.

The HepaChip is the size of a microscopic slide and comprises eight cell chambers arranged in parallel order. © NMI, Reutlingen

Many drugs repeatedly fall short of requirements in late-stage trials or have to be removed from the market. This is often because they cause significant liver damage when they are given to humans. In addition to causing severe health problems, late-stage drug failure or market removal generates high drug development costs, making products more expensive. “Around 25 percent of all drugs that are removed from the market due to toxicity have been implicated in causing liver damage,” said Dr. Martin Stelzle, head of BioMEMS and Sensor Systems at the NMI Natural and Medical Sciences Institute at the University of Tübingen in Reutlingen (NMI Reutlingen). Stelzle’s department focuses on the development of cell-based systems for testing drug toxicity. The newly developed HepaChip has the potential to detect possible liver toxicity very early in the drug development process.

Animal models are only suitable for testing drug toxicity to a limited extent. Julia Schütte, who was involved in developing the HepaChip, explains: “Some drugs are metabolised much more slowly and others much more rapidly in the human organism than in the animal organism.” Moreover, there are also species-specific differences between the human and animal metabolism. “In many cases it is not the drug itself that is toxic, but one or several of its metabolites that are generated by the human metabolism, and sometimes only by the human and not the animal metabolism,” said Simon Werner who developed the HepaChip together with Julia Schütte. 

The special feature of the HepaChip is that it uses human liver cells that are cultivated in a particular way. “Standard culture vials can only be used to test substances for their cellular effect for a period of between several hours and up to a few days. The advantage of our biochip is that the cells remain viable for much longer. Our ultimate goal is to incubate the drugs for several months, which will enable us to test the biotransformation of drugs under even more realistic conditions.” The researchers had to develop a special minimalistic biochip design that was simple, rapid and cheap without compromising reliability and reproducibility.

Organotypical conditions lead to realistic test results

The HepaChip simulates the functional unit of a liver sinusoid. © NMI, Reutlingen
The HepaChip has another particular advantage: “In addition to using human liver cells, the HepaChip also uses endothelial cells. The chip thus mirrors the real metabolic situation in the liver fairly realistically. “The chip does much more than just keeping cells in three-dimensional culture systems and exposing them to drugs. The liver consists of several different cell types, and our HepaChip actually simulates the functional unit of a liver sinusoid,” said Schütte. A liver sinusoid is a sinusoidal blood vessel around 80 micrometres in diameter, about as thick as a human hair. Moreover, the liver cells are surrounded by endothelial cells, which mediate the transport of nutrients and metabolic products between the blood vessels and the liver cells. The HepaChip mirrors the in vivo situation both with regard to the dimension and the number of cells in the sinusoid. The chip is made of a polymer carrier similar in appearance to the slides used for microscopic purposes. The polymer surface is functionalised by irradiating the sites where the cells are subsequently immobilised with UV light. UV-light functionalisation allows collagen proteins to bind to the surface and cells can subsequently bind to the collagen proteins. Functionalised chips like these can be stored for many months. Each chip then only needs to be covered with a collagen protein solution prior to use. The cells are attached to the collagen proteins exploiting the phenomenon of dielectrophoresis. The necessary technology was developed at the NMI. “The effect is based on the phenomenon in which a force is exerted on a particle when it is subjected to an electric field. We can control the high frequency field such that the cells assemble into liver sinusoid structures,” said Schütte. Stelzle added: “The active and defined arrangement of the cells is a unique selling point of our technology.”
Detailed representation of the HepaChip: the cells are site-specifically immobilised on the functionalised gap regions between the microchannels using a dielectrophoresis technology developed at the NMI. © NMI Reutlingen

It took the researchers quite some time before they had a functional biochip on hand. “Human hepatocytes turned out to be the greatest hurdle. Although cryoconserved hepatocytes are commercially available, we still had to optimise the media and thawing processes in order to obtain as many vital cells as possible. Dielectropheresis has the advantage that it only works with living cells, and is the reason why the chip is automatically selective for vital cells,” said Schütte. A HepaChip contains between 3000 and 4000 cells; several hundred such cells form a sinusoid-like structure. Such a low number of cells generate few metabolic products, and this was another challenge for the developers. Werner explains: “It is not easy to measure such a small quantity of metabolites. However, we have since established tests with marker proteins that ensure that the cells on the chip behave like liver cells." 

The researchers are currently working on the parallelisation and automation of the HepaChip system with the aim of enabling the large-scale application of the system. Important development milestones include the development of chip variants that can be aerated and heated and hence kept outside of an incubator. The HepaChip prototype consists of a single-channel system that will later also be transferred to the microtitre plate format with numerous channels. Schütte also told us that the principle of the chip is not only suitable for liver toxicity testing: “We have also initiated a project that focuses on a brain-blood-barrier model based on the same principle as the HepaChip.” In addition, the NMI has plans to further develop the dielectrophoresis technology for use with organotypical cell assemblies used for research purposes. 

Good market opportunities

The HepaChip is not only a convincing research product, but also has high economic potential, as the Science2Start competition jury confirmed in 2011. The concept of a marketable HepaChip system was so convincing that the two developers were awarded third prize. “We were very pleased with the prize, but some of the credit must go to the feedback that all Science2Start participants received, which helped us a lot,” said Schütte adding that the prize and feedback strongly motivated the two researchers. In their efforts to optimise the test system, Schütte and Werner can rely on competent support from the NMI and elsewhere. “Professor Dr. Rolf Gebhardt is a liver specialist at the University of Leipzig; he already served as a kind of ‘indicator’ around five years ago. His enthusiasm motivated us to continue the project and he then also became a partner in the project,” said Schütte.

The first phase of the BMBF-funded project, which started in 2007, focused on developing the scientific basis; the follow-up project, also funded by the BMBF, now focuses on refining the chip and the developers hope that they will soon be able to place the chip on the market. “More and more data are becoming available; the team from Leipzig has been able to show that the cells have a relatively high activity,” said Werner, visibly pleased with their achievements. The team does not exclude the option of establishing a company, and are considering doing so even before BMBF-funding comes to an end. “We have already prepared a 5-year financing plan. Our patent strategy is in place; we have filed the major patents and three more are in the preparation phase,” said Schütte. The new HepaChip company would be the 14th successful NMI start-up. The team fully agrees that the institute has given them all the support they could wish for.

Further information:

NMI Natural and Medical Sciences Institute at the University of Tübingen
Markwiesenstraße 55

72770 Reutlingen

Julia Schütte
Tel.: +49 (0)7121/ 51530 - 28
E-mail: julia.schuette(at)nmi.de

Simon Werner
Tel.: +49 (0)7121/ 51530 - 899
E-mail: simon.werner(at)nmi.de

Website address: https://www.gesundheitsindustrie-bw.de/en/article/news/hepachip-a-promising-tool-for-assessing-adverse-drug-effects