Scientists Create Mice With Transplanted Human Brain Tissue

Scientists at Stanford University have transplanted lab-grown human brain tissue into bioengineered mice, a development that could accelerate research into complex neurological conditions. The human tissue, developed from stem cells into 3D organoids mimicking the cerebral cortex, successfully integrated into the mice's developing nervous systems.

This breakthrough addresses the ethical limitations of studying living human brain tissue directly. The organoids replicate key features of human brain development, including the formation of functional neural networks. This allows researchers to examine human neural tissue at multiple levels, from genes and individual cell types to circuits and their functional consequences within an animal model.

The research team genetically modified mice to limit the development of their own cerebral cortex cells, creating space for the transplanted human cortical organoids to grow extensively after birth. "In these mice, the human grafts generated a broad diversity of cortical cell types and established functional connections throughout the mouse nervous system," explained senior author Professor Sergiu Pasca.

The resulting mice, termed 'xenocortical,' retain their mouse nervous system but contain a significant volume of human cortical tissue that develops and connects within it. Professor Pasca emphasized that these organoids are not miniature brains but provide an experimental window into human brain development and disease processes that are otherwise difficult to access.

Potential applications of this research include studying the causes and mechanisms of disorders such as autism, epilepsy, cerebral palsy, and schizophrenia. As an initial application, researchers used the xenocortical mice to investigate the effects of oxygen deprivation, a condition that can cause severe neurological damage during pregnancy or birth. The study found that these mice exhibited deficits in fine motor coordination and memory following a period of low oxygen, with substantial injury to the human cortical cells.

Professor Pasca noted that the experiments adhere to ethical guidelines concerning animal welfare and the responsible introduction of human neural tissue into animal nervous systems. He also highlighted the ethical imperative to conduct such research, given that neurological and psychiatric disorders affect a significant portion of the population with limited understanding and treatment options. "We also have to weigh the cost of not doing this work," he stated.