Study: Transplanted Brain Stem Cells Not Rejected by Immune System

For the first time, researchers have found that brain stem cells are "immune privileged," meaning that they are not rejected by a transplant recipient's immune system.

These results, published in the journal Stem Cells, suggest that using central nervous system stem cells in transplants for diseases of the eye (which is part of the brain), brain, and spinal cord, may eliminate the need for tissue typing before, and immunosuppressive drugs after, transplantation.

Ultimately these findings may improve the success of retinal transplantation to regenerate vision for millions with macular degeneration, retinitis pigmentosa and diabetic retinopathy, and brain transplants to restore functioning for patients with disorders such as Parkinson's disease.

"These findings are very exciting," said Michael Young, an assistant professor at Harvard Medical School. "Though we suspected brain stem cells might be protected in this way, this is the first documented evidence."

In their study, the researchers chose a part of the body that always rejects transplanted tissue without immunosuppressant drugs and without close tissue typing – the kidney capsule, the pouch in which the kidney is located.

They took brain stem cells from green mice (mice in which the gene for green protein found in jellyfish has been inserted) and placed them under the kidney capsule in other normal non-green mice.

After 4 weeks, the team examined the mice and found that the stem cells had not been rejected in any of the mice, and, in fact, had grown into neural tissue.

"Now we know that at least brain stem cells are immune privileged and can be used without the same worry about tissue matching or immunosuppression that is true for other types of tissue," Young said.

"Understanding the immune properties of these stem cells could have an enormous effect on how we perform brain or retinal transplantations in the future. Stem cells already have the advantage of being able to transform or differentiate into various types of cells and can be reproduced endlessly outside the body," he added.

Other Sources: Schepens Eye Research Institute