Immortalized stem-like cells could provide a limitless supply of spinal cord and brain replacement parts
Credit: US Centers for Disease Control and Prevention
Nerve regeneration: When damaged, spinal cord neurons such as these could be replaced using immortalized stem-like cells
A method of producing an unlimited supply of human neurons has been developed that could be used to treat brain diseases and spinal cord injury.
Researchers from the University of Rochester Medical Center in New York created the limitless supply by genetically modifying stem-like cells called neural progenitors.
The cells produce neurons through cell division, but only do so for short periods as they are unable to divide indefinitely like stem cells.
To address this shortcoming, the researchers introduced a gene called telomerase into the progenitors, essentially immortalizing them.
Nerve factory
While stem cells get much attention for disease treatment, progenitor cells offer the advantage of having already "decided" what type of cell to become.
This helps in the treatment of diseases that involve one specific cell type. A person with Parkinson's disease, for example, may only need dopamine-producing neurons, while someone with multiple sclerosis might only need cells that produce myelin.
Because progenitor cells divide a limited number of times, however, using them for therapy has been a challenge.
Researcher Steven Goldman and colleagues approached the problem by introducing the telomerase gene into the cells.
This allowed them to continuously divide while still producing only specific types of neurons.
Using their technique, the researchers developed a line of immortal progenitor cells that churned out human spinal neurons indefinitely.
"The progenitor cells are immortalized at a stage when they only give rise to the type of neuron we want, thus becoming an ongoing source of these neurons," says Goldman.
Healed spinal cords
To test the cells, the researchers injected them into rats with a damaged spinal cord and found that they replenished them with new nerve cells.
While worried that the telomerase gene could cause tumors to form, since cancer cells use telomerase to immortalize themselves, the researchers followed the rats closely for six months and found no tumors.
Another encouraging sign was that after about a month the cells stopped proliferating, as neurons in the spinal cord normally do.
Since the spinal cord is made up of several types of neurons, the researchers are now experimenting with other cell types.
"This work is the culmination of six years of work, and it will be many more years before an approach like this can be tried in human patients," says Goldman. "But the promise is extraordinary."
The research is reported in the journal Nature Biotechnology.