Scientists in Austria have grown miniature human brains from skin cells for the first time as part of a study into the development of the most complex of all our organs.
The mini-brains are less than 4mm across, but researchers say they are equivalent in development to the brain of a foetus at about nine weeks’ gestation.
Previous attempts at growing brain tissue focused on culturing nerve cells in two dimensions on a flat plate of nutrients, but the new study used a droplet of nutrient as a three-dimensional scaffold on which the growing cells organised themselves into the mini-organ.
The scientists have called the primitive brains “cerebral organoids”, and emphasised that the living structures are still far from being described as true human brains with a potential for self-awareness or consciousness.
“The individual brain areas we find in our organoids are not so far away from the size of the endogenous organs at this stage of development,” said Juergen Knoblich, of the Institute of Molecular Biotechnology in Vienna.
“Growing them bigger is not the issue. At this size, they can hold a lot of complexity. This is a cases where size doesn’t matter.”
The mini-brains were created from human skin cells that were converted into stem cells.
This produced induced pluripotent stem (iPS) cells which were then coaxed by chemical stimulants and nutrients to develop into mature brain cells that self-organised into the rudimentary structures of an embryonic brain.
Dr Knoblich said the organoids have already shed light on a condition called microcephaly, when the brain fails to grow to its correct size in the womb, and also could eventually help research into conditions such as autism and schizophrenia.
“This technique allows us to study the human-specific features of brain development. We can analyse the function of individual genes in a human setting,” he said.
“We have been able to model one disease, microcephaly, but ultimately we’d like to move to the more common disorders.”
The study, published in the journal ‘Nature’, showed it was possible to convert skin cells into a specialised form of embryonic tissue called the neuroectoderm, which produces all the components of the brain and nervous system.
Organoids from a patient with microcephaly failed to grow as fast as other organoids, but this could be corrected by replacing a defected gene.
Andrew Jackson, of the Medical Research Council’s Human Genetic Unit in Edinburgh, said: “Being able to generate tissue with such complexity in cell culture is a significant advance for the study of human diseases.”