Two scientists from my alma mater, UC Irvine, have examined experiments that treated stroke with bone marrow-derived stem cells. Their analysis has shown that infusions of these stem cells trigger repair mechanisms and limit inflammation in the brains of stroke patients.
UC Irvine neurologist Dr. Steven Cramer and biomedical engineer Weian Zhao identified 46 studies that examined the use of a specific type of bone marrow stem cells called mesenchymal stromal cells to treat stroke. Mesenchymal stromal cells are a type of multipotent adult stem cells that are found in many locations in the body. The best-known examples of mesenchymal stem cells are from bone marrow. When purified from whole bone marrow and used to treat stroke in animal models of stroke, Cramer and Zhao found that mesenchymal stromal cells (MSCs) were significantly better than control therapy in 44 of the 46 studies that were examined.
Further data culling of these studies showed that functional recovery from stroke were robust regardless of the MSC dosage or the time when MSCs were administered relative to the onset of the stroke, or the method of administration (whether introduced directly into the brain or injected via a blood vessel).
“Stroke remains a major cause of disability, and we are encouraged that the preclinical evidence shows [MSCs’] efficacy with ischemic stroke,” said Cramer, a professor of neurology and leading stroke expert. “MSCs are of particular interest because they come from bone marrow, which is readily available, and are relatively easy to culture. In addition, they already have demonstrated value when used to treat other human diseases.”
Another theme of these studies is that MSCs do not differentiate into brain-specific. MSCs have the capacity to differentiate into bone, cartilage and fat cells. “But they do their magic as an inducible pharmacy on wheels and as good immune system modulators, not as cells that directly replace lost brain parts,” he said.
In an earlier Cramer and Zhao examined the mechanism by which MSCs promote brain repair after stroke. These cells have the ability to home to the damages areas in the brain and release chemicals that stimulate healing. By releasing their cornucopia of healing-promoting molecules, MSCs orchestrate blood vessel creation to enhance circulation, the protection of moribund cells on the verge of death, and the growth of existing brain cells. Additionally, when MSCs reach the bloodstream, they settle in those parts of the body that control the immune system and they suppress the inflammatory response that can augment tissue damage. In this way, MSCs foster an environment more conducive to brain repair.
“We conclude that MSCs have consistently improved multiple outcome measures, with very large effect sizes, in a high number of animal studies and, therefore, that these findings should be the foundation of further studies on the use of MSCs in the treatment of ischemic stroke in humans,” said Cramer, who is also clinical director of the Sue & Bill Gross Stem Cell Research Center.