Neural Stem Cells Successfully Transplanted into Mice Brains
We may now be on our way to a real-life brain transplant, as researchers from the University of Luxembourg have neural stem cells transplanted into mice have been successfully integrated into the rest of the brain for the first time.
In this study, the researchers grafted skin cells that had been reprogrammed into induced neuronal stem cells into the brains of mice, specifically into the hippocampus and cortex region. Six months later, the neural cells are fully functionally integrated into the rest of the brain without any sign adverse side effects. They interacted with other neurons normally and even formed synapses. The researchers believe that creating the stem cells from the host's own skin cells drastically improved the compatibility of the cells.
From the paper: "[The stem cells] express all neural lineage markers and show a migratory behavior similar to endogenous NSCs. They also form synaptic connections within the existing network and receive frequent synaptic input. Consequently, iNSCs functionally integrated and interacted within the host tissue."
The most important measure of success in the study, aside from functional integration, was the lack of tumorigenic outgrowth. Older research with stem cells turned them into pluripotent stem cells, which could essentially turn into any kind of cell in the body. This seemed like the holy grail of regenerative medicine at the time, but unfortunately often led to tumor growth in experiments with animals. For this study, the researchers were able to bypass the pluripotent stage and transform the skin cells directly into neuronal stem cells. As a result, there was no tumorigenic potential, or no tumor growth in any of the participants.
The researchers freely acknowledge that they have a long way to go before even attempting this technique on human brains: "Successes in human therapy are still a long way off, but I am sure successful cell replacement therapies will exist in future. Our research results have taken us a step further in this direction," said stem cell researcher Professor Schwamborn. But if this therapy is ever approved for human use, it could be invaluable to the treatment of neurodegenerative disorders such as Parkinson's disease, as doctors would be able to replace neurons that had become damaged by the disease with healthy neurons. According to Schwamborn, they may even be able to cure the thus far intractable disease: "Building upon the current insights, we will now be looking specifically at the type of neurons that die off in the brain of Parkinson's patients — namely the dopamine-producing neurons."