- Bundesministerium für Bildung und Forschung (BMBF)
- Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR)
In the joint project, a microsystem was developed in which liver cells (hepatocytes) and endothelial cells are assembled into a vascular structure (liver sinusoid structure). The cells are positioned using electric fields (dielectrophoresis). The result is three-dimensional cell aggregates that are physiologically and structurally close to the natural tissue. Therefore, drug tests are expected to have a high predictive power with regard to the in vivo situation. The culture can be perfused with medium and tested with substances over several days. Microfluidics also has the advantage that test sequences can be automated.
Many drugs fail in the clinical phase due to serious toxic side effects. Especially in the field of liver toxicity, the animal and in vitro tests performed in the preclinical phase have poor predictive power. The differences in species in animal experiments and the loss of organotypical cell functions in 2D cultures mean that there is currently no reliable model for liver toxicity tests. The rapid dedifferentiation of primary cells in well cultures is often the result of the absence of an in vivo-like environment. Organs are characterized by a well-organized 3D structure with multiple cell-cell and cell-matrix interactions that are not considered in currently used 2D cultures.
In BioMEMS (bio-microelectromechanical systems) it is possible to manipulate individual cells in a targeted manner and thus build up complex organ-like structures. Micro-scale structural dimensions and the possibility of continuous perfusion of the culture come much closer to the in vivo situation than standard 2D well cultures. This leads to an improved viability and functionality of the cells. Microfluidics also offers the advantage that test sequences can be automated, which improves the reproducibility of tests and reduces the amount of work required.
In the HepaChip joint project, a novel substance screening system based on organotypical liver co-cultures was developed. Primary human hepatocytes and endothelial cells are positioned and assembled in micro-chambers by electric fields (dielectrophoresis) in such a way that the resulting cell aggregates reproduce the complexity of the in vivo 3D structures of the liver sinusoid on a micro-scale. A surface coating with extracellular matrix proteins promotes adhesion and growth of the hepatocytes. After assembly of the culture, the cells are perfused with medium via microchannels. It could be shown that the activity of hepatocytes (albumin secretion, urea synthesis, phase I and II enzyme activity) in the HepaChip is increased compared to 2D cultures in the well.
The principle of assembling tissue-typical cell arrangements in microsystems using dielectrophoresis can be applied to a wide variety of cell types and could be used to simulate other organs and tissues in addition to the liver, e.g. intestines, lungs or the blood-brain barrier in a perfusible microchip.
- BSL Bioservice, München, Dr. C. Höppner
- European Screening Port, Hamburg, Dr. P. Röhnert
- Insitut für Biochemie der Medizinischen Fakultät der Universität Leipzig, Prof. Dr. R. Gebhardt