The transplanted stem cells helped brain’s own neurogenic cells to leave their neurogenic niche and move towards the injured brain tissue.
To date, two different views on how stem cells work in brain damage caused by injury or neurodegenerative disorders. One part of researchers suggest that stem cells implanted into the brain directly replace dead or dying cells. The other view is that transplanted stem cells secrete growth factors that indirectly rescue the injured tissue.
The USF study presents evidence for a third concept of stem-cell mediated brain repair.
The researchers randomly assigned rats with traumatic brain injury and confirmed neurological impairment to one of two groups. One group received transplants of bone marrow-derived stem cells (SB632 cells) into the region of the brain affected by traumatic injury. The other (control group) received a sham procedure in which solution alone was infused into the brain with no implantation of stem cells.
At one and three months post-TBI, the rats receiving stem cell transplants showed significantly better motor and neurological function and reduced brain tissue damage compared to rats receiving no stem cells. These robust improvements were observed even though survival of the transplanted cells was modest and diminished over time.
Also, three months after the brain injury, the brains of rats that were transplanted stem cells showed massive cell proliferation and differentiation of stem cells into neuron-like cells in the area of injury.In contrast, the rats receiving solution alone showed limited proliferation and neural-commitment of stem cells.
The researchers conclude that the transplanted stem cells create a neurovascular matrix that bridges the long-distance gap between the region in the brain where host neural stem cells arise and the site of injury. This pathway, or “biobridge,” ferries the newly emerging host cells to the specific place in the brain in need of repair, helping promote functional recovery from traumatic brain injury.