Researchers have created mice with human brain tissue, a development intended to aid in understanding and developing treatments for disorders such as schizophrenia, epilepsy, cerebral palsy, intellectual disability, and rare forms of dementia.
The scientists transplanted lab-grown human brain cells into mice that were genetically engineered to be born without a cortex or hippocampus. This procedure created space within the rodents' skulls for the human tissue to grow.
This method allows researchers to take cells from patients with brain disorders, cultivate them into brain tissue in a laboratory, and then grow this tissue in living animals. The animals can then be studied to observe how disorders affect human brain tissue and how potential drugs might treat these conditions.
Sergiu Pașca, a professor of psychiatry at Stanford University who led the research, stated that the goal has been to make aspects of human brain development and function accessible for investigation, particularly given the complexity and inaccessibility of the human brain.
The work has undergone extensive ethical oversight. Emily Jackson, a professor of law at the London School of Economics, highlighted that animal welfare is a significant concern and requires close monitoring of these animals to assess the impact on them.
The human tissue in the mice connected to the mouse's blood supply and filled approximately half of the rodent's brain cavity. Some human neurons formed connections with mouse brain cells and the spinal cord. The human brain tissue was immature, comparable to that found halfway through human pregnancy, and tests indicated the animals were not enhanced by the transplants, though their shaky gait and cognitive problems showed slight improvement.
The researchers demonstrated the potential of these mice by exposing some to low oxygen, revealing the vulnerability of human nerve cells to oxygen deprivation, a cause of cerebral palsy. They also found rare von Economo neurons in the human brain tissue, which are among the first cells to die in frontotemporal dementia.