A team of researchers successfully used rabies viruses to help develop a technique for transplanting nerve cells. The viruses were modified to fluoresce and were then used to track how transplanted neural cells connected to different regions of the brain. The findings may lead to treatments for diseases that trigger a loss of nerve cells, such as Parkinson’s disease. The details were just published in the journal Nature Communications.
Some diseases destroy nerve cells or cause them to become dysfunctional. Examples of degenerative nerve diseases include Alzheimer’s disease, Parkinson’s disease, and Huntington’s disease. Scientists are currently able to grow nerve cells from neural stem cells but it’s unclear whether or not transplants are actually possible. While researchers have successfully grafted neurons into mouse brains, there was no easy way to gauge whether or not these cells were being properly incorporated into the neural network.
Scientists from the University of Bonn in Germany used rabies viruses to track how implanted neurons were being integrated into mouse brains. The viruses, which had been rendered completely harmless, were modified to produce green fluorescent protein. This protein caused the viruses to constantly fluoresce, allowing them to be observed as they moved throughout the brain. As the viruses spread, implanted neurons connected to other nerve cells, which would then turn green. By utilizing a separate technique that turns brains transparent, the team used a combination of light sheet fluorescence microscopy and three-dimensional magnetic resonance imaging to create a 3D brain map.
The researchers found that the new neural cells were incorporated into specific regions of the brain depending on where the cells were initially transplanted. Human trials are still far off, however, as researchers need to continue to study the mechanisms behind these types of transplants.
The team’s findings show that transplanted neurons can be grafted into different parts of the brain. The technology is still new but the research team’s rabies virus-based method can be used to better understand what determines where the new cells end up. Eventually, the technique may be used to help treat degenerative nerve diseases.
Doerr et al. Whole-brain 3D mapping of human neural transplant innervation. Nature Communications (2017).