Neuroscience, the study of the brain and nervous system, is one of the research areas in Switzerland that has relied heavily on the use of animals, as revealed by our analysis of trends in the number of animal uses over the last 27 years.
As scientific methods advance, new possibilities are emerging to replace animal experiments and reduce the number of animals required. Central to this progress is the development of human cell-based models that offer both biological relevance and a more ethical approach to studying complex brain diseases.
Below we are sharing the most recent work and advancements from three research groups. Together, they show how novel in vitro methods are being used to address major public health questions, from evaluating whether environmental chemicals may harm the developing brain, to understanding neurodevelopmental disorders such as ADHD, and finding better ways to study aggressive childhood brain cancer.
DID YOU KNOW?
The human body is made up of trillions of tiny building blocks called cells. Different types of cells have different jobs, from carrying oxygen (blood cells) to transmitting signals (nerve cells).
What does “in vitro” mean?
In vitro (Latin for “in glass”) refers to experiments conducted outside a living organism, typically in a laboratory. These methods allow researchers to study biological processes using cells and tissues in controlled conditions.
Are you familiar with the -oids?
Spheroids, tumoroids, and organoids are tiny three-dimensional clusters of cells grown artificially in the laboratory from human (or non-human) cells. Unlike traditional flat cell cultures, these 3D models better mimic the architecture and cell-to-cell interactions found in living human tissue. They range from simpler, easier-to-produce models (spheroids) that lack spatial differentiation to more complex structures that more closely mimic functional parts of organs (organoids).
- Spheroids are self-assembling clusters of cells that replicate the structure and function of small pieces of tissue, such as part of the brain.
- Tumoroids are grown directly from a patient’s tumour sample, retaining the cellular diversity and characteristics of the original cancer.
- Organoids are simplified versions of functional parts of organs, often grown from stem cells (cells that can develop into many different cell types), allowing scientists to study human development and disease.
By providing new human-relevant technologies that enable researchers to study specific questions about human biology, these models support the Replacement of animal experimentation and the Reduction of animal numbers in biomedical research.
Replacement of Animal Use in Testing of Chemicals on Brain Development
Research conducted by Dr David Pamies, Head of the Stem Cell and Organoid Facility at the University of Lausanne.
There is substantial evidence that chemicals in our environment can harm brain development, particularly during the brain development period from early pregnancy through to around 25 years of age. Yet the vast majority of chemicals in commerce have never been tested for these effects.
Why? Traditional testing for developmental neurotoxicity (harm to the developing brain) requires large numbers of animals and significant resources. This creates a major barrier to routine safety testing for many chemicals.
The challenge
There is a significant push from regulatory bodies, such as the EFSA (European Food Safety Authority), the FDA (the US Food and Drug Administration) and the European Medicines Agency (the authorities responsible for evaluating the safety of medicines and chemicals), to adopt New Alternative Methods (NAMs). These are complementary approaches to the use of animals in research, including methods like organ-on-a-chip (small devices with channels that allow fluids to flow past human cells, simulating aspects of organs), the use of -oids, and computational models.
The 3Rs approach
Dr Pamies and team have developed human brain spheroids; tiny, 3D micro-tissues derived from human stem cells. After eight weeks of development in the laboratory, these spheroids contain three key brain cell types:
- Neurons, which transmit electrical signals
- Astrocytes, which support and protect neurons
- Oligodendrocytes, which produce myelin (the insulating layer that helps signals travel faster along nerve fibres)
The presence of myelin is particularly important. Myelination, the process of forming this insulating layer, is a critical part of brain development. Standard animal and basic cell culture models have various limitations in reproducing myelination, which makes it harder to test in these models whether chemicals interfere with myelination.
In this spheroid model, researchers can expose brain cells to chemicals at defined concentrations and measure effects on cell health, function and myelination under controlled conditions.
3Rs relevance
While regulatory bodies have proposed a set of laboratory tests to assess whether chemicals harm brain development, a reliable way to test effects on myelination is still missing. The spheroid model from Dr Pamies’ team, which produces myelin, helps fill this gap.
Human brain spheroids support Reduction by offering an alternative that allows screening many chemicals with fewer animals. These spheroids are particularly valuable for Replacement approaches in developmental neurotoxicity research, where differences between species in the timing and processes of brain development, such as myelination, can make it challenging to apply findings from animal studies to humans.
Replacement of Animal Use in Children’s Brain Cancer Research
Research conducted by Prof. Javad Nazarian, MD, Professor at the University of Zürich, Head of the DIPG/DMG Research Centre at University Children’s Hospital Zürich.
The challenge
Diffuse Midline Glioma (DMG) is a highly aggressive type of brain tumour mostly affecting children between the ages of 5 and 9. Because the tumour grows in the brainstem (the part of the brain controlling vital functions like breathing and heart rate), surgical removal is not possible.
Traditional approaches rely on analysing a single tumour sample, examining its DNA to find mutations (changes in the DNA) that could be targeted with specific drugs, guiding the treatment. However, these tumours change rapidly. Within months, these mutations can shift dramatically, meaning that treatment decisions based on the initial sample may no longer be effective. Developing laboratory cell lines for drug testing using traditional methods takes 8 to 10 weeks, and promising drugs are then typically tested in animal models by implanting tumour cells into mice (xenografts). This process is often too late to inform clinical decisions for patients who have limited time.
The 3Rs approach
To address this, Dr Nazarian’s group is developing patient-derived tumoroids and organoids grown from small samples taken during surgery. These 3D mini-tumours keep key features of the original cancer, including the mix of cell types and how fast they grow. In 2-4 weeks, researchers can test many drugs or combinations in parallel on the same patient’s cells, and observe how the tumour responds. They are also using microfluidic devices (small platforms that handle tiny amounts of liquid, allowing precise control over cell environments) that grow patient cells as spheroids. These devices allow researchers to visually monitor how cells respond to drugs in real-time. This significantly speeds up the process from taking the tumour sample to treatment recommendation.
3Rs relevance
Patient-derived tumoroids and organoids support Replacement and Reduction by providing a human-based model that can answer early research questions without immediately using animals. Even if experiments in animals may still be needed, tumoroid data using this model can help narrow down the most promising treatment options, so fewer animals are used in follow-up experiments.
Replacement of Animal Use in ADHD Research
Research conducted by Prof. Dr Edna Grünblatt, Professor at the University of Zurich, Head of Translational Molecular Psychiatry at the Department of Child and Adolescent Psychiatry & Psychotherapy, Psychiatric University Hospital Zurich.
The challenge
Attention-Deficit/Hyperactivity Disorder (ADHD) affects approximately 7% of the population and is characterised by delayed brain maturation.
ADHD is often treated with methylphenidate, the most common treatment in Europe. In people without ADHD, methylphenidate can act as a psychostimulant, increasing activity and alertness. In many people with ADHD, it has the opposite effect on behaviour, improving focus and reducing hyperactivity. This apparent contradiction raises questions about how ADHD brains differ at the cellular level and how methylphenidate acts in that context.
To study these questions, researchers need models that reflect human brain development and genetics more closely than is possible in traditional animal experiments alone.
The 3Rs approach
Prof. Grünblatt’s group uses induced pluripotent stem cells (iPSCs) taken from patients and healthy controls, and reprogrammed in the laboratory to an early developmental state, from which they can be grown into specific cell types. From these iPSCs, the team generates patient-specific neural stem cells and cortical neurons (brain cells from the outer layer of the brain).
This approach allows scientists to compare brain cells derived from individual patients with ADHD with those from healthy controls, directly in the laboratory.
The team observed changes in the Wnt signalling pathway in ADHD patient cells. A pathway is a series of molecular events that control cell behaviour. In this case, the Wnt signalling pathway plays a central role in how brain cells grow, divide, specialise and form connections.
Preliminary results showed that methylphenidate influences how neuronal stem cells proliferate (divide) and differentiate (mature into neurons). In ADHD patient cells, methylphenidate increased cell proliferation compared with untreated ADHD cells. In the healthy control cells, they observed no changes. This suggests that the Wnt pathway contributes to how methylphenidate affects ADHD patient cells, although further work is needed to fully clarify the mechanism.
3Rs relevance
By using human, patient-specific cells in a dish, this research embodies the Replacement principle. Because ADHD involves uniquely human characteristics, experiments with animals cannot fully cover the need to study this disorder and identify new treatment approaches.
These research projects illustrate the ongoing shift in how neuroscience research is being carried out. Human-based non-animal methods are no longer just promising ideas: they are being actively developed and applied to answer important questions about brain health and disease. This progress shows that the 3Rs, as guiding principles, are increasingly being implemented in practice. As these approaches continue to mature, they pave the way for a future of neuroscience that is both more effective at understanding the brain and more humane.
This article is based on research presented at the Swiss 3RCC webinar “Replacement in Neuroscience”, held on November 13th, 2025.