A new study published in the journal Nature Communications has shed new light on why the injured brain and spinal cord does not fully regenerate.
Scientists have long assumed that one of the reasons why nerve cells in the spinal cord do not re-grow after being severed is due to scar tissue, when healing, becoming harder than surrounding healthy tissue.
According to this theory, regeneration is hampered by hardened scar tissue acting as an impenetrable barrier. However, a team of scientists from UCL and the Universities of Cambridge and Brighton put this theory to the test.
What they found was in fact the opposite. Scar tissue in the brain and spinal cord is much softer than surrounding healthy tissue and this seems to be due to increased numbers of support cells, called glia, at the site of damage.
Lead author Dr Emad Mooendarbary
Lead author on the paper, Dr Emad Moeendarbary from UCL, describes the results as a significant breakthrough in our understanding of how the brain and spinal cord responds to injury: “These results prove that damaged nerve cells do not encounter a hardened roadblock as they try to re-grow. We still don’t fully understand why neurons do not regenerate. However, our study, along with recent findings from other research groups, changes the way we view scar tissue in the brain. It may, in fact, help neuron regeneration as opposed to hinder it.”
It is estimated that some 50,000 people in the UK and Ireland have some form of spinal cord injury with 3 new cases every day. There is currently no cure and new treatments are desperately needed to provide patients with improved quality of life and hope for a future cure. However, progress in spinal cord injury research has been slow, due to the hugely complex nature of the injury.
New research, including the present study, which questions long-held theories about the physical properties of the injury,
Mechanical properties of the intact cortex.
are forcing scientists to re-think how medical treatments for brain and spinal cord damage can be improved. Fortunately, more and more sophisticated tools are being developed to tackle this pressing medical problem.
In this new study, the authors used a technique known as ‘atomic force microscopy’ to measure differences in the stiffness of healthy brain and spinal cord compared to scar tissue. The brain and spinal cord was then cut into very fine slices and fluorescence microscopy was used to visualise different cell types and proteins. A type of glial cell, which expresses a large amount of a protein called Vimentin, seems to be drastically increased in the very soft areas of scar tissue. However further work is needed to understand the full significance of this novel finding.
University of Brighton neuroscientist and co-author on this study, Dr Graham Sheridan, describes options going forward: “The next challenge is to figure out why neurons do not grow beyond soft scar tissue. We know there are chemicals released by glia and damaged tissue that prevent regeneration. However, if we can build a more complete picture of both the biochemical and biomechanical properties of scar tissue, this will help neuroscientists and clinicians to develop more effective therapies for brain and spinal cord injury”.