The formation of scar tissue is a normal part of healing, but one that is often viewed as an unfortunate side effect. Researchers from Sweden are challenging this view, saying that stem cell scarring following a spinal injury actually helps recovery.

Researchers from the Karolinska Institutet report, in the journal Science, that in spinal injuries, stem cell scarring “blocks” the spread of the damage, stopping the lesion from expanding and helping injured nerve cells recover.

The National Spinal Cord Injury Statistical Center in Birmingham, AL, estimates that in 2013, there are 273,000 Americans with spinal injuries.

They say that it primarily affects young adults, aged between 16 and 30, with young males making up about 80% of this number. Motor vehicle crashes are the most common cause, followed by falls and acts of violence (gunshot wounds).

Spinal cord injuries cause varying degrees of paralysis, depending on where in the spine they occur and the severity of the injury. Paralysis and weakness occur in the regions of the body below the injury, meaning injuries to the neck and cervical spine are the most problematic.

Paralysis is often permanent, particularly when the nerve fibers are cut, as these do not grow back.

The nerves conduct the signals between the brain and the rest of the body. The researchers note previous medical beliefs maintain that the scar tissue itself is the problem and that if treatments prevent it forming, the nerves would regenerate.

But the present study focused on spinal stem cells, which are one of the main sources of scar tissue, and the researchers claim the results turn conventional thinking on its head.

Far from impairing recovery, stem cell scarring contains the damage. Researchers studying mice found that if they prevented stem cells from forming new cells, thereby stopping scar formation, the injury gradually expanded and more nerve cells were cut.

They also found that fewer spinal cord nerve cells died in the mice that were allowed to form normal scar tissue.

Prof. Jonas Frisén, of Karolinska Institutet’s department of cell and molecular biology, explains:

It turned out that scarring from stem cells was necessary for stabilizing the injury and preventing it from spreading. Scar tissue also facilitated the survival of damaged nerve cells. Our results suggest that more, rather than less, stem cell scarring could limit the consequences of a spinal cord injury.”

And while earlier animal studies have suggested recovery may be improved by transplanting stem cells into the injured spine, Frisén’s research claims that simple stimulation of the patient’s own stem cells could be a viable alternative to cell transplantation.