Microphysiological Systems: ethically correct and highly realistic

Nobody wants to miss out on the blessing of modern medicine. But despite all of its advances, there is still one downside: animal testing. It is hotly contested for a variety of reasons. On the one hand, it is ethically questionable, while the transfer of results and application to humans is not always accurate on the other. The microphysiological systems of the Fraunhofer IWS offer an alternative.

In this interview with COMPAMED-tradefair.com, Dr. Udo Klotzbach and Florian Schmieder explain how these systems work, detail their advantages over animal experiments and describe the potential they provide.

Mr. Schmieder, the Fraunhofer IWS develops microphysiological systems as an alternative to animal experiments. What are they exactly?

Florian Schmieder: Microphysiological systems are small, technical reproductions of the basic functions of the human body. The systems cultivate specific cells or tissue of individual organs or organ systems. To ensure cells function the same way they do in the human body, the characteristics as provided by the body are technically implemented. Examples are temperature control, specific pressures or flows as they occur at various locations or blood supply. This gives cells a physiological environment as it occurs in the human body.

Why do we need an alternative to animal testing?

Dr. Udo Klotzbach: For one thing, there are obviously ethical concerns – animal rights – that necessitate alternatives. Another point is that animal experiments conducted in the laboratories of pharmaceutical or medical technology companies do not correspond exactly to human beings. You inevitably encounter limitations and need to find other methods. Microphysiological systems offer a great option in this case.

What are these systems able to replicate?

Schmieder: Essentially, we have quite a broad set of tools. We use them to emulate a variety of functions and recreate the original as closely as possible. Depending on which cells you cultivate in the system, you are technically able to emulate all organs though not in their full complexity. The biologists and health professionals we collaborate with are concerned with very specific issues. And we want to provide them with exactly what they need. Besides, the goal is not always to replicate the entire organ in its full complexity. Oftentimes, a more complex test is also more expensive. What’s more, you are also subsequently not able to realize high parallelism. That is to say, on the one hand, the organs should be copied in as much of a complex manner as possible, while they should be as cost-effective and suited for mass implementation as possible at the same time. This is why it is not always necessary to exactly replicate all physiological characteristics normally exhibited by the human body. The specific issue drives what is important and what must be reproduced.

We are approached with a wide range of questions and issues, for instance as it pertains to substance testing without animal testing. Basic research raises yet other questions. In this case, the objective is to investigate how the different types of cells of the human body interact with each other and how specific signaling cascades work for example.

What are these "artificial mini-organism" made of?

Schmieder: They are made of plastic foils that can be structured with a laser. This gives the foils certain functions. We can realize functional, active elements within the plastic foils, for example, a pump that represents the human heart. There are also other functional elements such as the oxygenator that simulates the function of the lungs for instance.

How does a microphysiological system work?

Schmieder: Pumps or valves are essentially what keeps the chip alive and what we implement as engineers. Our cooperation partners then breathe lives into them – meaning the biologists, physicians, and chemists.

Klotzbach: Our job is to develop the chip design based on the respective issue. For example, if the goal is to study the interaction between a pharmacological substance and the liver, we subsequently contemplate what the corresponding chip should realistically include and how it should be built. You can add liver cells into one of the reservoirs of the chip – several are possible. Using a micropump, blood is pumped through the microfluidic system via small channels – simulating the blood circulation in a human being. Now you can add the substance that needs to be tested to the circulation. Thanks to the active component, the micropump, the substance is diluted with blood and directed through the liver in much the same way it works in the human organism. The advantage is that the entire setup is transparent. That means scientists are able to monitor the cells under the optical microscope for instance.

How far have you come in your research? Are there already concrete applications?

Schmieder: We have one partner in the field of nephrology with whom we have already collaborated for quite some time. Together, we try to replicate the different components of the kidney on one chip. We are able to depict the individual functional units of the kidneys with different chip designs. The kidneys are essentially composed of different biological barriers. We replicate this kidney function on this type of chip. This allows us to specifically answer kidney-related questions in collaboration with our partner.

What future possibilities do you see for microphysiological systems?

Schmieder: For one thing, we believe that this field will expand significantly, also in light of the fact that animal testing is in part subject to legal action or is meant to be reduced. Another advantage of these systems is rooted in the accuracy of the model. We believe that these systems will be extensively applied in both scientific research and pharmaceutical testing in the near future. Needless to say, we also hope that funding will be more strongly promoted especially in Germany, to where we can more specifically realize the human organism in all its complexity in microphysiological systems.