Taking a Different Approach to Stem Cell Therapy for Stroke
Researchers hope dampening the immune response will limit damage.
Since a stroke overstimulates the immune system, resulting in permanent damage to the brain, can using stem cells to calm the immune system limit the extent of damage caused by a stroke?
Cleveland Clinic researchers participating in multicenter studies of this unusual approach to stem cell therapy are trying to find out. “We are cautiously optimistic,” says neurologist Ken Uchino, MD.
Taking a Different Road
Stem cells are a basic building material of body parts. When prompted, immature stem cells can develop into any type of cell the body needs.
Most stroke research projects have focused on implanting stem cells into the brain, with the hope they will create new brain tissue to replace the tissue damaged by stroke. In theory, this should allow a patient to regain any function lost during a stroke.
But this direct approach has not been successful. “We don’t have the ability to manipulate stem cells to do what we want them to do,” says Dr. Uchino.
This study is taking a different, indirect approach. Instead of implanting stem cells into the brain, 1.2 billion of the cells are infused into the bloodstream, which carries them throughout the body. The goal is not to regrow new tissue, but to prevent the immune system from overreacting.
“We know that a brain injury causes an immune reaction, because the spleen, which filters immune cells, enlarges after a stroke. We can see by changes in spleen size that infusing stem cells does something to the immune system. We are hoping this may reduce harm to the brain,” Dr. Uchino explains.
This hope is based on solid evidence gained from manipulating the immune response in animals. “We were surprised it worked so well,” says Dr. Uchino.
The early phases of this clinical trial have gone smoothly. No safety issues with stem cell infusion were seen in phase 1.
Phase 2 randomized 129 patients to receive an infusion of stem cells or placebo 24 to 48 hours after a stroke. More than half of these patients had been treated with tPA or thrombectomy, yet continued to show evidence of deficits.
Those who were infused earlier seemed to have less disability. This fact has been figured into the phase 3 study, which will start this year. “The goal of this phase is to see whether infusing stem cells within 36 hours will result in even less disability at 90 days,” says Dr. Uchino. The answer will be known three to four years from now.
Dr. Uchino says it is unlikely that using stem cells to alter the immune response will be a cure. Their goal is to reduce damage from stroke, while extending the treatment window.
“If we can get patients 50 percent better, we will be happy,” he says.