Mini brains 'could transform drug testing'

Miniature brains made out of clusters of human cells could revolutionise high-throughput drug screening, said scientists at the American Association for the Advancement of Science annual meeting in Washington, DC, earlier this month. 

'Ninety-five percent of drugs that look promising when tested in animal models fail once they are tested in humans, at great expense of time and money,' said study leader Dr Thomas Hartung from the Johns Hopkins Bloomberg School of Public Health at a press conference.

Dr Hartung and colleagues created the mini-brains using skin cells from adult volunteers. These cells are reprogrammed back into stem cells, which are then induced to grow into brain cells. Within two months they grew into three-dimensional clusters approximately the size of a housefly's eye.

Despite their tiny size, these mini-brains are surprisingly complex and are able to replicate some primitive brain functions. They include four distinct types of neurons as well as two different supporting cells – including oligodendrocytes, which create the protective myelin sheath surrounding neurons. The mini-brains even show spontaneous electrophysiological activity in response to various drugs similar to what might be seen on an electroencephalogram (EEG). 

Researchers think that mini-organs may better represent how normal human brains react to specific drugs and could therefore provide a viable alternative to animal models.

'While rodent models have been useful, we are not 150-pound rats. And even though we are not balls of cells either, you can often get much better information from these balls of cells than from rodents,' Dr Hartung told Motherboard.

Experiments using mini-brains could also be used for basic research, providing insight into neurodegenerative diseases such as Alzheimer's and Parkinson's disease, stroke and trauma.

'We don't have the first brain model, nor are we claiming to have the best one. But this is the most standardised one. And when testing drugs it is imperative that the cells being studied are as similar as possible to ensure the most comparable and accurate results,' said Dr Hartung.

The method is also scalable, with the possibility of generating hundreds of mini-brains from the same batch of cells.

'Nobody should have an excuse to still use the old animal models,' said Dr Hartung.

Dr Hartung's team is currently creating a spin-off company called Organome, which aims to make mini-brains available for pharmaceutical testing within the next year.