Symmetry-breaking Technologies for Cerebral Organoid Engineering

According to the Global Burden of Disease, neurological conditions are the leading cause of disability and the second-leading cause of death worldwide. The debilitating nature of these conditions can have a devastating effect on an individual's quality-of-life and their ability to undertake activities of daily living. This exerts a heavy strain on families, carers, society and healthcare systems, moreover, the medical costs, care costs and loss of productivity arising from disorders of the brain have been estimated to cost the UK economy over £100 billion per year.

In order to design preventative and therapeutic strategies, we need to understand how neurological conditions arise and how they affect the human brain. However, the human brain is relatively inaccessible to study as a living organ, while post-mortem biopsies cannot be used to study the function of brain tissue. Meanwhile, differences in brain anatomy mean that animals are often unsuitable for studying human neurology. Over the last decade, a new approach to studying the human brain has emerged: the use of "brain organoids" generated from 3D clusters of stem cells. These organoids provide an alternative to animal studies and have been used to model human brain development and neurological conditions, such as microcephaly.

A major limitation of brain organoids is the lack of control exerted over their formation and development, which leads to organoids that are geometrically and biologically symmetric. This is a problem because the human brain is a naturally asymmetric structure with different regions formed from an elongated cell structure, known as the neural tube. As a result, symmetric brain organoids cannot be used to study the asymmetric aspects of brain development or the asymmetric processes present in many neurological conditions.

This limitation will be directly addressed in this Fellowship by developing a suite of technologies that can break the symmetry of brain organoids to produce models of the human brain that enable the study of complex neurological conditions. These technologies will be adapted from previous methods that I have developed for growing muscle and cartilage. Ultrasound patterning will be used to remotely assemble stem cells into elongated neural tubes, which will controllably develop different regions of the brain under the influence of chemical gradients slowly released from a biomaterial. Ultrasound will also be used to remotely pick up, move and fuse different brain organoids to assembly complex cerebral structures.

These asymmetric organoids will be used to study asymmetric processes in common neurological conditions: the failure to form different regions of the brain in holoprosencephaly, the dysfunctional migration of neurons in many psychiatric disorders (e.g., schizophrenia, autism) and the spread of toxic proteins in Alzheimer's disease. For each of these processes, the symmetry-broken organoids will be used to assess the contribution of different environmental and genetic risk factors, providing new knowledge that will inform future preventative or therapeutic strategies.

Moreover, these research outputs have a scope that extends far beyond neuroscience, with the capacity to address similar challenges in other organoids (e.g., pancreatic, endometrial). To benefit a wide range of users, the symmetry-breaking technologies will be refined into user-friendly toolkits, while high-throughput manufacturing methods will be developed for the symmetry-broken organoids. Academic collaboration, industry partnerships and product commercialisation will be used to disseminate these toolkits and organoids to academic groups, biotechnology industry and pharmaceutical industry. This will ensure far-reaching impact beyond the immediate goals of this Fellowship by providing researchers from different fields with the tools to grow their own complex organoids for the study of development, disease and drug response.