The death of neurons whether in the eye or in the brain can result in a variety of human neurodegenerative diseases that range from blindness to Parkinson’s disease. Treatments currently available for these type of disorders only slow the progression of the illness. This is because once a neuron dies it cannot be replaced.
A study conducted by researchers from the University of Notre Dame, Johns Hopkins University, Ohio State University and the University of Florida have identified networks of genes that regulate the process which is responsible for determining if neurons will regenerate in certain animals such as zebrafish.
The study is proof of principle indicating that it is possible to regenerate neurons in the retina. The team also believes the process for regenerating neurons located in the brain will be similar.
For the research, the team mapped genes of animals that have the ability to regenerate neurons in the retina. One example is found in zebrafish. When their retina is damaged, cells known as Muller glia go through a reprogramming process. During this process, the Muller glia cells change their gene expression and become like progenitor cells or cells that are used during early organism development. These now progenitor cells can become any cell that is necessary to fix the retina that has become damaged.
People also have Muller glia cells. However, when a human retina is damaged, the Muller glia cells respond with gliosis which is a process that will not allow them to reprogram.
After the team determined the different animal processes for retina damage recovery, they had to decipher if the process for gliosis and reprogramming were similar. They wondered if the Muller glia follow the identical path in non-regenerating and regenerating animals or would the paths be totally different. This knowledge would be important so they would be able to use Muller glia cells to regenerate neurons in the retina in humans. Understanding whether it would be a matter of redirecting the current Muller glia path or if an entirely different process would be required.
They found that the regeneration process only needed the organism to turn back on its early processes of development. They were also able to illustrate that during zebrafish regeneration Muller glia also go through gliosis. This means that organisms that have the ability to regenerate retinal neurons do follow a similar path to animals that cannot.
The network of genes in zebrafish are able to move Muller glia cells from gliosis into the reprogrammed state, however the network of genes in mice models blocked the Muller glia from reprogramming. From here, the team was able to modify zebrafish Muller glia cells into a similar state that blocked the reprogramming while also having mice models regenerate some neurons in the retina.
The next step for the researchers is to try and identify the number of gene regulatory networks that are responsible for neuronal regeneration and exactly which genes within the network are the ones responsible for regulating regeneration.
To view the original scientific study click below