Certain kinds of nerve damage have long been considered irreversible. Now, a study from researchers at the University of Cambridge might point toward a way to repair the irreparable.
As we get older, our brains and bodies take longer to heal from injury. This is especially the case with our central nervous system, the lightning rod between the spinal cord and the brain. Axons, the nerve fibers our neurons zip up and down on to carry messages and control muscle, are less likely to be able to recover from damage.
It means an injury to the brain — or spinal cord — has a greater chance of resulting in permanent paralysis.
In the study, researchers grew tiny brains the size of peas from stem cells. Then, they added on to the models, creating miniature versions of the brain-spinal system. Because the parts are separate in the body, scientists kept them apart in the lab, too.
The result? Axons grew from the brain cells to the spinal cord, bridging the gap. It created a working neural circuit that prompted microscopic groups of muscle cells to contract.
The organoids were maintained in the lab for more than 365 days. After the 150th day, however, researchers noticed a difference: the axons were less capable of regrowing. This points to a “biological switch” that flips once neurons begin maturing and creating synapses. When researchers blocked it, the axons went back to regenerating.
Although further research is necessary, scientists note this is a successful instance in which stem cell organoids mimicked real human systems. They may have been miniature, but potential impacts could be larger than life.