Neuroscientists Develop Mice with Human Brain Cells for Research

Neuroscientists in the United States have successfully adapted mice to incorporate functioning human cells within their brains. The researchers aim to test potential treatments for psychiatric and neurodevelopmental diseases that primarily affect humans on these laboratory rodents. The genetically engineered mice are not capable of human-like thought, according to the scientists. Their work, published in the journal Nature, underwent independent ethical scrutiny. The objective of this development is to enhance understanding of brain disorders that currently lack effective treatments. Certain conditions cannot be studied in mice due to the absence of corresponding brain disorders in rodents. Lead researcher Professor Sergiu Pașca from Stanford University noted that psychiatry has a low success rate for clinical trials, stating, "Even drugs that actually make it to clinical trial - that seem to be working really well in animal models - fail dramatically in clinic." He emphasized the need for more information about human biology. The Stanford team believes that this model could be transformative for complex conditions such as epilepsy, autism, and cerebral palsy. Pașca remarked, "Here we have a new model that allows us to actually capture aspects of human brain function in a way that has not been possible before." The human brain consists of billions of cells interconnected in complex circuits, making it challenging to comprehend its development and the cellular-level issues when disorders occur. Although this is not the first instance of human neurons being implanted in rodents, the current research has advanced this approach. The researchers genetically engineered mice to develop minimal cerebral cortex, which is responsible for higher-level thinking, memory, and sensory processing. They then reprogrammed human skin cells to create brain-like tissue known as organoids. These organoids were implanted into the mouse brains, where they integrated into the existing brain circuitry. The implanted human cells began to resemble and function like the outer layer of the mouse's brain after several months. Behavioral tests conducted six months post-surgery showed that the mice performed similarly to normal mice, with no enhancements noted. Dr. Sarah Chan, a bioethics reader at the University of Edinburgh, commented that the study raises questions about the implications of altering animal cognition. Dr. Ilary Allodi, a neuroscientist from St Andrews University, praised the research, noting the formation of cell types unique to human and primate brains in the implanted mice. The researchers stated that these mice are developed under strict ethical and welfare guidelines and will likely be used in a limited number of laboratories for specific brain disorder studies. Professor James Ainge from St Andrews University acknowledged the technical achievement but highlighted the ethical concerns regarding the implications of raising living human brain tissue in mice.