Getting On Tract: Stem Cells Regenerate Injured Spinal Cord in Rats

a6353-spinalcordThe spinal cord acts as a highway that transports electrical signals from your brain to the rest of your body through long bundles of nerve fibers. It allows your brain to communicate with the rest of your body to coordinate movement and reflexes and to receive sensory information. When the spinal cord is damaged, the nerve fibers, which are also called axons, are crushed or severed. This important communication highway is disrupted, leaving patients partially or fully paralyzed and severely reducing their quality of life.

Stem cell treatments for spinal cord injury

Scientists are pursuing multiple strategies using stem cells to treat spinal cord injury. Some involve transplanting cells derived from pluripotent stem cells or from stem cells isolated from human tissue. Both types of stem cells can be manipulated to develop into new nerve cells that can replace those that have died or into new support cells that coax damaged nerve cells to regrow their axons. Others are transplanting stem cells at the site of injury to prevent further damage by reducing tissue scarring and inflammation or by releasing protective factors that keep the remaining nerve and support cells healthy.

Repairing a damaged spinal cord is no easy task. Stem cell treatments tested in animal models have only shown partial recovery of motor function, and clinical trials using stem cells to treat spinal cord injury in humans are still in their early stages (read more about clinical trials here).

However, a group from UC San Diego is on “tract” (pardon the pun) to develop a novel treatment that might one day regenerate damaged spinal cords in humans. They published their exciting study in Nature Medicine yesterday suggesting that stem cells can regenerate injured spinal cords – at least in rats.

Getting on tract to regenerate injured spinal cords

The team grafted neural stem cells derived from rat embryonic stem cells into the injured spinal cords of rats. These stem cells developed into functional nerve cells that replaced damaged axons in the corticospinal tract, which is bundle of nerve fibers in the spinal cord that originates in the cerebral cortex of the brain and controls basic motor function. Injured rats that received stem cell grafts showed improvements in their ability to move their forelimbs.

Transplanted neural stem cells (green) shown in the corticospinal tract (red) develop into new neurons (purple). (Nature Medicine)

Transplanted neural stem cells (green) shown in the corticospinal tract (red) develop into new neurons (purple). (Nature Medicine)

The authors also grafted neural stem cells derived from human embryonic stem cells into injured spinal cords of rats and observed evidence of spinal cord regeneration and newly generated corticospinal axons.

The study’s senior author, Dr. Mark Tuszynski, explained in a UC San Diego Health news release that their study is the first to regenerate the corticospinal tract in rats using neural stem cells. While this work is in its early stages, Dr. Tuszynski believes that his group’s work has the potential to be translated into a treatment for human spinal cord injury:

Mark Tuszynski, UCSD

Mark Tuszynski, UCSD

“We humans use corticospinal axons for voluntary movement. In the absence of regeneration of this system in previous studies, I was doubtful that most therapies taken to humans would improve function. Now that we can regenerate the most important motor system for humans, I think that the potential for translation is more promising.”

 

However, when translating any stem cell therapy from animals into humans, safety and efficacy are a top priority. Dr. Tuszynski acknowledged these hurdles and shared his plan for future studies:

“There is more work to do prior to moving to humans. We must establish long-term safety and long-term functional benefit in animals. We must devise methods for transferring this technology to humans in larger animal models. And we must identify the best type of human neural stem cell to bring to the clinic.”

As a side note, CIRM has funded earlier translational research by Dr. Tuszynski. You can read more about his CIRM-funded research project to develop novel stem cell treatments for spinal cord injury here.


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