A group of proteins that help to regenerate injured nerves is identified by the scientists at the German Center for Neurodegenerative Diseasepublished in the journal Neuron.
Neurons of the Central Nervous System cease their growth when they reach synapses near their target cells. The research shows that not only the young neurons have the potential to regrow and repair but also old nerve cells are capable of the phenomenon.
The laboratory studies led by the team of Professor Frank Bradke at the German Centre for Neurodegenerative Diseases (DZNE)in collaboration with scientists of the University of Bonn disclosed the fundamental mechanisms for this regeneration.
Bradke said; “Actually, this is quite surprising. It is by no means a matter of course that young and adult nerve cells share the same mechanisms.” “Neurons show vigorous growth during embryonic development. Mature nerve cells, on the other hand, usually do not grow and fail to regenerate. Our study now reveals that although the ability to grow is inhibited in adult cells, the neurons keep the disposition for growth and regeneration.”
Bradke and coworkers discovered that certain proteins are pivotal to initiate growth in young neurons. The neurobiologist said; “These proteins are key regulators of growth competence, irrespective of developmental stage. They act on the cell’s supporting structure and thus trigger dynamic processes, which are a prerequisite for growth and regeneration.”
Embryonic development is the period of great importance as it involves the growth of neurons, forming long projections “axons“. Axons are nerve fibers that typically conduct electrical impulses known as action potentials away from the nerve cell body, thus helps in adjoining and transmitting signals. However, in mature nerves, their ability to grow and repair diminishes.
Only peripheral neurons, e. g. those found in the arms and legs perpetuate their distinct potential for the process of regeneration enabling the restoration of the nervous system. However, paralysis and other dysfunctions are encountered due to the cleaving of axons in the spinal cord, thus shutting down the repairing and regrowth of the damaged tissues resulting in obstruction in the transmission of the nerve impulses.
A lead author and a postdoctoral researcher in Bradke’s lab, Sebastian Dupraz said; “For quite some time, we have been wondering whether it is possible to reactivate the processes which manifest in the early developmental phase. This could be a way to trigger regeneration in adult neurons,” In the current research, various factors that have an impact on the growth of neurons were determined by the Bonn scientists.
The actin-depolymerizing factor (ADF)/cofilin family comprises small actin-binding proteins with crucial roles in development, tissue homeostasis, and disease. During embryonic development, the ADF/cofilin family controls the formation of cell protrusion that ultimately matures into axons. “In our recent study, we found that it is precisely these proteins that drive growth and regeneration, also in adult neurons,” Dupraz said.
The research discloses that the ADF/cofilins are essential proteins responsible for the high turnover rates of actin filaments enabling the growth and regrowth of neurons. The molecular structure of these proteins gives the cell its proper structure and stability, as well as regulates the dynamics of the actin filament.
These turnover filaments play a vital role in the process of regeneration of the worn-out tissues. DZNE scientist Barbara Schaffran, another leading author of the research, said; “An approach for future regenerative interventions could be to target actin.”
In a trial “dorsal root ganglion” of mice and rats were used for experimentation, the results showed the occurrence of these processes in their nerve cells. Dorsal root ganglion is a bundle of neurons conjoining the spinal cord and the peripheral nervous system.
Its cells consist of two axons, a central and a peripheral, the latter plays a role in the process of neuroregeneration. It was also enlightened that the central axon can also regrow, but only if it has previously been lacerated. “Why the sequence is like this is still not exactly known,” Bradke said. “We will be looking into this in the future.”
Further progress is being made to find the treatment of spinal cord injuries, and understand the mechanism behind the neuroregeneration extensively. Bradke said; “We do research in order to set the basis for future therapies. But sadly, you have to be patient until new treatment approaches develop. That’s a long way to go.”