Clue Discovered to Nerve Cell Re-Growth
Since the beginning of modern medicine, it has been widely recognized that among the chief obstacles of the healing arts has been repair of the central nervous system. Whereas other types of differentiated cells throughout the body can readily regenerate, and though the peripheral nervous system has demonstrated some capacity toward healing, those of the central nervous system – which is comprised of the brain and spinal cord – do not. It is this inability which has long stymied efforts to address conditions such as paralysis.
However, there may be a promising future ahead for those affected by severe neurological damage. At the Washington University School of Medicine in St. Louis, scientists have uncovered a clue as to why some nervous cells can re-grow and others cannot. It is hoped that it will lead to a possible means of stimulation of genes that will promote the repair of axons (the branches of nerve cells responsible for transmission of electro-chemical signals).
The heart of the solution is HDAC5: apparently the protein most responsible for alerting the cell that regeneration is required. According to Dr. Valeria Cavalli, assistant professor of neurobiology and chief author of the study:”We knew several genes that contribute to the regrowth of these nerve cell branches, which are called axons, but until now we didn’t know what activated the expression of these genes and, hence, the repair process.”
As part of the research Dr. Yongcheol Cho, a postdoctoral research assistant, cultivated peripheral nerve cells in the laboratory. The axons of the cells were then severed and observed. It was found that doing so sent a message via calcium ions to the cells’ nuclei to begin repair of the axons. Part of the process is the release of HDAC5 from the nucleus. From there the protein activates a series of genes which direct the repair mechanisms and produce the materials needed to effect the re-growth.
However, when the researchers suppressed activation of HDAC5 in the experimental phase, the protein remained trapped in the nucleus. The result: no significant repair of the cell was possible. In further experimentation, release of the HDAC5 was allowed to proceed following the introduction of certain drugs.
HDAC5 is found in cells across the entirety of the nervous system, both peripheral and central. However for reasons still not clear, the cells of the central nervous system do not release HDAC5 and thus, repair of the axons is a rarity if not impossible. The researchers believe that if the cells of the nervous system can be encouraged to release HDAC5 in the same way as their peripheral counterparts, that considerable regeneration of what many argue are the most critical cells in the body can be achieved. In the future, it could lead to treatment of paralysis, neuromuscular disorders and even problems with sensory input.