But their findings surprised them. "We didn't see that sprouting was faster or better in younger than in adult rats after a partial spinal cord injury," she said. Instead, they saw distinctions in what occurred in cells within the spinal cord at the site of injury. Leung and Wrathall specifically discovered that in the pups, specialized neural stem cells grew vigorously after injury and within one week, many oligodendrocytes, cells whose function is to provide a protective myelin sheath to axons, were produced..
The researchers believe that these activated cells wrap nearby surviving axons with extra myelin sheathing in order to protect them and support their function after injury.
"The ability of axons to transmit their signals is greatly dependent on the insulation provided by their myelin sheaths, and we know that axons near the site of injury eventually can die due to loss of this myelin," Wrathall said. "So we believe these stem cells work to protect healthy axons against toxic factors in the microevironment."
Adult rats do not activate these specialized cells to the same extent as the pups do after injury, for reasons that are not understood, she added.