Swiss researchers have grown more than 400 different types of human nerve cells, offering a new way to study complex brain diseases in a dish, such as Alzheimer’s, Parkinson’s and depression. 

The human brain is made up of thousands of nerve cell types, which have different structures, functions and locations. Until now, this complexity had not been able to be studied in a dish — researchers were able to grow just a few dozen nerve cell types. 

“If we want to develop cell culture models for diseases and disorders such as Alzheimer’s, Parkinson’s and depression, we need to take the specific type of nerve cell involved into consideration,” said Barbara Treutlein, leader of the study published in Science. 

To overcome this limitation, the researchers at ETH Zurich used human-induced pluripotent stem cells, undifferentiated cells obtained from the blood. They treated the cells with specific combinations of molecules called morphogens, which help determine cell identity and location in embryos during early development, guiding the cells to form the 400 types of nerve cells. 

By comparing the lab-grown nerve cells with databases of human brain cells, the researchers could identify their region of origin and function—for example, they could tell whether the cells are involved in sensing pain, cold or movement — showing that the cells were very similar to the ones in human brain. 

While there is still a long way to go until all types of nerve cells found in a living brain can be grown in a lab, this study greatly increases the number of nerve cell types available for in vitro research. These cells could now be used to build better models to study brain diseases.