Lab-made mini brains grow their own ‘eyes’
Organoids are miniature versions of organs that scientists can grow in the lab from stem cells, or cells that can mature into any type of cell in the body. Previously scientists have developed tiny beating hearts and tear ducts that could cry like a human’s do. Scientists have even grown mini brains that produce brain waves like those of preterm babies. Now a group of scientists have grown mini brains that have something their real counterparts do not: a set of eye-like structures called ‘optic cups’ that give rise to the retina, the tissue that sits in the back of the eye and contains light-sensing cells.
In the human body, the retina sends signals to the brain via the optic nerve, allowing us to see images. “In the mammalian brain, nerve fibres of retinal ganglion cells reach out to connect with their brain targets, an aspect that has never before been shown in an in-vitro system,” said Jay Gopalakrishnan, a researcher at University Hospital Düsseldorf. Previously researchers had grown optic cups individually in labs, but this is
the first study that integrated optic cups into brain organoids.
Gopalakrishnan and his team adapted a technique they developed for turning stem cells into neural tissue. Once the stem cells had developed into mini brains, the organoids formed optic cups. The optic cups appeared as early as 30 days and matured within 50 days, a time frame similar to how the retina develops in a human embryo. In total, the researchers created 314 mini brains, and 72 per cent of them formed optic cups.
The organoids contained different types of retinal cells that formed active neuron networks that responded to light. The organoids also formed lens and corneal tissue. “Our work highlights the remarkable ability of brain organoids to generate primitive sensory structures that are light sensitive and harbour cell types similar to those found in the body,” said Gopalakrishnan. The researchers now hope to figure out how to keep the optic cups viable for a long time and use them to research the mechanisms behind retinal disorders.