Brain Organoid

What is a Brain Organoid?

A brain organoid is a three-dimensional, self-organizing laboratory model that reproduces selected features of brain tissue. Many are grown from human pluripotent stem cells, which can develop into different types of cells. Depending on the method, an organoid may contain neurons and supporting cells with some of the organization seen in developing brain tissue.

“Mini-brain” is a memorable nickname, but it can give the wrong impression. An organoid is not a complete brain in miniature. Its cell types, structure, size, and maturity depend on how it was grown. The consensus on nervous system organoid terminology makes this distinction central to how these models are named.

Types of Brain Organoids

Cerebral and Cortical Organoids

Cerebral organoids may contain features of multiple cerebral regions. Cortical organoids are designed to model features of the cerebral cortex. Researchers have used cerebral organoids to study aspects of neurodevelopmental disorders such as microcephaly and autism. The cells and layers present in a particular model must be checked; the name alone does not establish them.

Hippocampal Organoids

Hippocampal organoids model selected features of the hippocampus, a region involved in learning, memory, and spatial navigation. They do not automatically contain all of its subregions or working circuits. Their value for a research question depends on whether they reproduce the cellular features that matter for that question.

Midbrain Organoids

Midbrain organoids are designed to reproduce features of the midbrain and can contain dopamine-producing neurons, a cell type affected in Parkinson's disease. A useful disease model needs more than the right regional name: researchers must establish which cells are present and what the measured changes represent.

Brain Organoids for Disease Modeling

Researchers can grow organoids from a patient's induced pluripotent stem cells (iPSCs) to study genetic and cellular features of disease. They can also examine cellular responses to drugs. This makes organoids useful for questions that are difficult to study directly in a living human brain, but a drug response in an organoid does not establish that the treatment works in a patient.