Early in vitro testing for adverse effects on embryos

May 14, 2019

Medications have to be safe for mothers-to-be and for their unborn children. Before the authorities will approve a new drug, it must be tested in animal trials on pregnant rodents and, as a rule, pregnant rabbits. Scientists in the Department of Biosystems Science and Engineering at ETH Zurich in Basel have now developed a test that allows them to examine a drug's embryotoxicity in cell cultures instead of animals.

The new test does not yet replace the animal trials that are legally required as part of the medication approval process. However, as the new procedure is simple, fast, and inexpensive, researchers will be able to use it in the future to test a large number of drug candidates at an early stage of the development process. Substances that are harmful to embryos will thus be detected early in the drug development process and not only in embryotoxicity studies in animal trials. Because they are so expensive, animal tests are not conducted until much later in the drug development process with only carefully preselected potential drug candidates. As the new test weeds out unsuccessful drug candidates earlier, it may help cutting costs and reducing the number of animal experiments.

Cell culture test with stem cells

The new procedure is an advanced form of the embryonic stem cell test, in which substances are tested in vitro on so-called embryoid bodies. These three-dimensional clumps of cells are formed from embryonic stem cells - in this case, from a mouse - and undergo the first stages of embryonic development over a period of ten days. No viable embryos can be produced from these cells.

Led by ETH Professor Andreas Hierlemann, the research group has now expanded this embryonic stem cell test to include human liver tissue. "There's a whole host of substances that are not toxic in their original form, but can be transformed into adverse substances by the human metabolism - especially by the liver," explains Julia Boos, a doctoral student in Hierlemann's group and lead author of the study, which has been published in the journal Advanced Science. In contrast to the conventional embryonic stem cell test, the newly developed test can detect substances of this nature.

Body on a chip

From beginning to end, the new test takes place in its entirety on a single cell-culture chip, which is equipped with various compartments. The compartments contain microtissue spheres, formed from human liver cells by the ETH spin-off InSphero, and embryoid bodies, grown from mouse stem cells. The liver microtissues and embryoid bodies have a diameter of about half a millimetre and are placed in different compartments, which are connected through microchannels to guarantee a constant liquid exchange between the different groups of cells.

"We're the first to directly combine liver and embryonic cells in a body-on-a-chip approach," Boos says. Just as a pregnant woman's circulatory system links the metabolic processes in her liver with those in her developing embryo, this connected system ensures constant interaction between the liver cells and embryonic cells. "Metabolites created by the liver cells - including metabolites that are stable for just a few minutes - can thus act directly on the embryonic cells," Boos says. She explains that combining the two in a single chip presents an improvement over other existing in vitro tests, which investigate the metabolisation of substances in the liver separately from the effects that these metabolites have on embryonic cells.

Boos goes on to describe another advantage of the new test: "In contrast to tests on living pregnant mice, in our test, the substances are metabolised by human liver cells - in other words, just as they would be in the human body when the medication is administered." She points out that this is relevant, as humans and mice have different metabolisms.

Further development for high-throughput testing

The researchers demonstrated the effectiveness of the new test with the help of cyclophosphamide. This chemotherapeutic drug has virtually no effect in its basic form, but the liver transforms it into a substance that is toxic to cells. Two tests were run with cyclophosphamide: one included the newly developed liver/embryoid body test, and the other involved embryoid bodies alone without liver microtissues. What these tests revealed was that a fourfold lower concentration of cyclophosphamide was enough to have an adverse effect on the development of the embryoid bodies when liver tissue was present in the same environment.

Now, the scientists need to refine the test further before it can be applied in drug development. They are paying particular attention to the materials that are used in the test in addition to how well the procedures can be automated. Automation would be necessary if the pharmaceutical industry or other researchers were to be able to deploy the test on a large scale for high-throughput screening of drug candidates. In addition, the scientists wish to develop a test that uses reprogrammed human stem cells (known as iPS cells) instead of mouse stem cells. Then they would have an in vitro test entirely based on human tissue.

Boos JA, Misun PM, Michlmayr A, Hierlemann A, Frey O: Microfluidic Multitissue Platform for Advanced Embryotoxicity Testing In Vitro, Advanced Science 2019, 1900294, doi: 10.1002/advs.201900294

ETH Zurich

Related Stem Cells Articles from Brightsurf:

SUTD researchers create heart cells from stem cells using 3D printing
SUTD researchers 3D printed a micro-scaled physical device to demonstrate a new level of control in the directed differentiation of stem cells, enhancing the production of cardiomyocytes.

More selective elimination of leukemia stem cells and blood stem cells
Hematopoietic stem cells from a healthy donor can help patients suffering from acute leukemia.

Computer simulations visualize how DNA is recognized to convert cells into stem cells
Researchers of the Hubrecht Institute (KNAW - The Netherlands) and the Max Planck Institute in Münster (Germany) have revealed how an essential protein helps to activate genomic DNA during the conversion of regular adult human cells into stem cells.

First events in stem cells becoming specialized cells needed for organ development
Cell biologists at the University of Toronto shed light on the very first step stem cells go through to turn into the specialized cells that make up organs.

Surprising research result: All immature cells can develop into stem cells
New sensational study conducted at the University of Copenhagen disproves traditional knowledge of stem cell development.

The development of brain stem cells into new nerve cells and why this can lead to cancer
Stem cells are true Jacks-of-all-trades of our bodies, as they can turn into the many different cell types of all organs.

Healthy blood stem cells have as many DNA mutations as leukemic cells
Researchers from the Princess Máxima Center for Pediatric Oncology have shown that the number of mutations in healthy and leukemic blood stem cells does not differ.

New method grows brain cells from stem cells quickly and efficiently
Researchers at Lund University in Sweden have developed a faster method to generate functional brain cells, called astrocytes, from embryonic stem cells.

NUS researchers confine mature cells to turn them into stem cells
Recent research led by Professor G.V. Shivashankar of the Mechanobiology Institute at the National University of Singapore and the FIRC Institute of Molecular Oncology in Italy, has revealed that mature cells can be reprogrammed into re-deployable stem cells without direct genetic modification -- by confining them to a defined geometric space for an extended period of time.

Researchers develop a new method for turning skin cells into pluripotent stem cells
Researchers at the University of Helsinki, Finland, and Karolinska Institutet, Sweden, have for the first time succeeded in converting human skin cells into pluripotent stem cells by activating the cell's own genes.

Read More: Stem Cells News and Stem Cells Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.