In 2021, a total of 1.86 million vertebrates and cephalopods were used for research purposes in Germany, according to information from the Federal Ministry of Food and Agriculture. Although this is two percent less than in the previous year, it is still a very large number. The animals most commonly used in German laboratories are mice, fish and rats. “Currently, many research tasks require the help of such animal experiments to be solved,” Dr. Wiebke Sihver from the HZDR's Radionuclide Diagnostics Department points out. This is why searching for alternative options remains enormously important, she adds. “In addition, animal models often lack important references to the human organism.”
In their work, Wiebke Sihver and her HZDR colleagues are concerned with the development and application of radiolabeled substances for cancer diagnostics and in particular also cancer therapy. These radioligands are labeled with a radioactive nuclide (radionuclide) and bind to a target molecule, in the case of cancer to specific target structures of the tumor. The radiopharmaceutical thus acts directly on the tumor. Surrounding healthy tissue is spared. To date, radiopharmaceuticals developed at the HZDR have to be tested in animal models such as mice and rats after in vitro characterization. Several years ago Wiebke Sihver was already seeking a replacement for the many animal experiments in radiopharmaceutical research. During her search for alternative systems she quickly came across Fraunhofer IWS. There, a team has been researching for several years on microphysiological systems that use cultivated mini-organisms to mimic the functioning of the human organism – thanks to the use of human cells, for example, closer to the human tumor than animal experiments could. It was the starting point for a new idea.
Development with Great Potential
Researchers at Fraunhofer IWS have already been working on the mini-labs for more than ten years. With these microphysiological systems in the format of a tablet box, organ functions or even disease processes can be artificially represented with the help of cell cultures. Valves and channels simulate the vascular system, a small pump the heartbeat. The microphysiological systems are made of plastic films layered on top of each other. Blood vessels and chambers are cut into these by laser. In special modules, users later grow cell cultures that can survive for up to a month in the micro systems. Meanwhile, blood circulates in the mini-lab in the form of a nutrient medium that supplies the cells with oxygen and nutrients. A few years ago, this framework only enabled the representation of two organs. Today, as many as four can be simulated simultaneously on these novel multi-organ chips.
When the HZDR team turned to Fraunhofer IWS, the experts there quickly recognized the potential for a new application. “Multi-organ chips have not yet been used in the development of radiopharmaceuticals, so there is a great need for them,” explains group leader Florian Schmieder, who has been involved in lab-on-chip research at Fraunhofer IWS for many years. Together, the two institutes successfully applied for a grant from the German Federal Ministry of Education and Research on “Alternative Methods to Animal Testing”. This will continue until 2024, and they have achieved the first promising results.