Scientists have transplanted neural cells taken from a monkey’s skin into its brain and found that the cells changed into several types of mature brain cells, according to a new study in the journal Cell Reports.

The scientists revealed that after six months, the cells looked completely normal and were only detectable because they were originally flagged with a fluorescent protein. The experiment is evidence for the concept of personalized medicine – treatments that are made for each individual – because all cells were derived from adult cells in each monkey’s skin.

A common problem with cell transplants is immune rejection, but since the skin cells were from their own body this was not an issue.

Senior author Su-Chun Zhang, a professor of neuroscience at the University of Wisconsin-Madison explained:

“When you look at the brain, you cannot tell that it is a graft, Structurally the host brain looks like a normal brain; the graft can only be seen under the fluorescent microscope.”

Marina Emborg, an associate professor of medical physics at UW-Madison and the lead co-author of the study, says, “This is the first time I saw, in a nonhuman primate, that the transplanted cells were so well integrated, with such a minimal reaction. And after six months, to see no scar, that was the best part.”

The scientists implanted the cells in the monkeys using a new surgical method led by an MRI image. Three rhesus monkeys used in the experiment had a lesion in their brains that produced the movement disorder Parkinson’s disease – a disorder affecting nearly 1 million Americans.

Parkinson’s is the result of a number of dopamine-producing neurons dying.

The implanted cells were derived from pluripotent stem cells (iPS cells) – similar to embryonic stem cells – changing into almost any cell in the body. iPS cells, however, come from adult cells instead of embryos.

The iPS cells were then altered in progenitor cells in the lab. These middle-stage cells specialize into the neurons that transport nerve signals, and glial cells – which conduct nutritional functions and support. The last level of maturation took place inside the monkey.

Zhang was the first person in the world who derived neural cells from embryonic stem cells and then iPS cells and said one crucial factor came into play, “We differentiate the stem cells only into neural cells. It would not work to transplant a cell population contaminated by non-neural cells.”

With stem cell transplants, cancer is always a danger, however no signs of the disease were present. Zhang commented:

“Their appearance is normal, and we also used antibodies that mark cells that are dividing rapidly, as cancer cells are, and we do not see that. And when you look at what the cells have become, they become neurons with long axons [conducting fibers], as we’d expect. They also produce oligodendrocytes that are helping build insulating myelin sheaths for neurons, as they should. That means they have matured correctly, and are not cancerous.”

Zhang led the group on the use of iPS cells at the Waisman Center on the University of Wisconsin-Madison campus. The researchers used the experiment as a proof of principle, however, they did not transplant enough neurons to replace the dopamine-making cells in the brain and the animal’s behavior did not get better.

The new technique is promising, however it is far from being readily used in the clinic. The authors point out that more research needs to be completed to estimate the safety and side effects of the method.

Regardless, the current study is a stepping stone that could potentially benefit humans suffering from many diseases. It is a step towards personalized medicine.

The need for new treatment is endless, the authors note – every year Parkinson’s is diagnosed in 60,000 new patients.

Zhang concludes:

“It’s really the first-ever transplant of iPS cells from a non-human primate back into the same animal, not just in the brain. I have not seen anybody transplanting reprogrammed iPS cells into the blood, the pancreas or anywhere else, into the same primate. This proof-of-principle study in primates presents hopes for personalized regenerative medicine.”

Written by Kelly Fitzgerald