There once was little hope for a treatment to repair brain or spinal cord injuries, until now.
The promising research surrounding the miracle of neural regeneration may just change the outlook for the future.
Your brain is like a central computer that controls almost every aspect of your being, but it’s also one of the most vulnerable organs to permanent damage. Once you damage your noggin or injure any neurons, there is limited capacity for repair … or is there?
Neural Regeneration: What Is It?
Before we dig into the latest research, let’s take a moment to talk about the basics of neural regeneration — and why it may be considered a miracle. First, a few related terms to define:
- Neurogenesis — the new growth and development of nervous tissue
- Neuroplasticity — the ability to rewire the brain
- Neural (or neuron) regeneration — repairing injured or damaged cells
Neurogenesis is the term used to discuss the ability to create new neuron cells. Typically, the bulk of neurogenesis occurs in infancy and childhood, but studies since the 1970s have found that neurogenesis can occur in adulthood as well. However, this remains a debated topic, largely thanks to a recent study at the University of California San Francisco, which led to new skepticism about the existence of human adult neurogenesis.
Researchers are continuing to look into this area of research, including whether medications may stimulate neurogenesis and thereby provide relief of various neural and psychological disorders. There is a current hypothesis that Selective Serotonin Reuptake Inhibitors (SSRIs) provide their benefit to depression not because of the effect on serotonin but due to the ability to promote neurogenesis, according to an article published in the scientific journal Neuropsychopharmacology.
Meanwhile, a review published in the British Journal of Pharmacology discusses several studies demonstrating cannabinoids may play a role in adult mammalian neurogenesis, which could be one reason for CBD oil’s cognitive benefits.
Currently, there is no clear consensus on whether adult brains can develop new neurons, and if they can, at what level, according to The Atlantic. Some of the debate stems from much of the research being carried out in animals rather than humans, with concern about whether the animal models are true representatives.
Neuroplasticity is the term for the brain’s capacity to rewire the different neural pathways to correct for injuries, temporary or permanent loss of function, and other errors or damage that may occur, according to The Conversation, an evidence-based online news publication. It means that our brains are more malleable than we thought. Certain types of learning — and even the way you think — have the potential to change the brain’s structure and function.
In a more severely damaged brain, the full function may not be restored, but the brain is still able to rewire, allowing for some level of recovery and restoration. For example, after a traumatic brain injury or stroke, an individual may be able to regain certain motor skills, such as walking or talking, even if the area of the brain that originally controlled these functions remains damaged, thanks to the brain’s capacity to incorporate new and different circuitry pathways.
According to an article in The Huffington Post, researchers at the University of Alabama at Birmingham created a treatment protocol that incorporates the concept of neuroplasticity. They have successfully helped patients recover speech and certain motor skills even decades after a stroke or traumatic brain injury. This type of treatment may also help treat the loss of function associated with neurodegenerative diseases such as Parkinson’s or cerebral palsy, and they have also helped those who have lost function due to a spinal cord injury.
The Challenges Surrounding the Regeneration of Neurons
Neural (or neuron) regeneration is a term that details the ability of neurons or nerves to regenerate or repair after injury. This is different from neurogenesis in that it does not always involve growing new cells; it is about repairing the existing neurons that have been damaged.
Most tissues have the ability to repair themselves through a combination of regeneration and replacement, according to a 2010 article in the scientific journal Organogenesis. After injury or damage, new cells take the place of damaged cells. Stem cells, for instance, play a central role in repairing many damaged tissues since they have the capacity to self-renew and they can become different cell types, unlike cells that are already differentiated into a particular type of cells (such as a skin cell or a neuron).
Some tissues are harder to regenerate, which makes them harder to heal. The nervous system is one of these, which is why damage to the spinal cord, brain, or other components of the nervous system is often permanent, as the Mayo Clinic’s Center for Regenerative Medicine states. The peripheral nervous system (PNS) has a distinct capacity for regeneration that is better than that of the central nervous system (CNS). The main reason for this is that the PNS has what is known as a Schwann cell. Among the many functions of this type of cell is the ability to protect and regenerate the transmitting part of the neurons.
Although we may not have the same spontaneous regeneration in the nervous system as we do in other areas of the body, innovative treatments may be able to stimulate neural regeneration to fully heal nervous system injuries or neurodegenerative disorders in the future.
The Promise of Stem Cells
Stem cells play a central role in tissue repair and regeneration. According to Medical News Today, these cells are undifferentiated, which means they have yet to become a certain type of cell that only plays a certain role, such as liver cells or heart cells. Instead, they can become any number of cell types when needed.
There are two categories of stem cells: the controversial embryonic stem cells and somatic (or adult) stem cells. The former cells come from donated fertilized embryos, generally from in vitro fertilization clinics. Because they originate in embryos, the use of these type of cells has been controversial. The latter cells continually develop in the adult, allowing a source for stem cell therapy for repair and regeneration. However, they do not have as high of capacity as embryonic stem cells for differentiation, and thus for restoring damaged tissue. They can still be used in the repair of many different systems, including the nervous system.
Due to the promise of stem cells, as well as their location in the brain, much of the research into potential treatments incorporating neural regeneration utilizes stem cells. According to ALS News Today, a recent study utilized human spinal cord neural stem cells (NSC) to regenerate neurons in rats with spinal injuries. This study used human pluripotent stem cells, which are unspecialized. Because they do not already have a specialty, they have the capacity to become any type of cell required. The researchers made them into spinal cord neurons, demonstrating a progression from in vitro work differentiating stem cells into the specific neurons required.
Then, they transplanted the cells into a rat model, which differentiated into additional specialized spinal cord nerve cells and lead to spinal cord regeneration and repair from injury. This is a mouse model, so it is not known whether it can be reproduced in humans, but it is a promising step in terms of neural regeneration.
Although stem cell treatment remains experimental, there have been some individuals who have already benefited from these treatments. Stem cell treatments have helped reverse blindness, treat chronic pain, repair cartilage, and more, according to Dave Asprey, the brain behind Bulletproof and the author of Game Changers.
The research is promising enough that the Mayo Clinic began a Phase 1 Clinical Trial (the first stage for experimental treatments) on stem cells for spinal cord injury, and there are additional studies in the works from other institutions.
Using Genetics for Repairing Neurons
Studies have gone beyond stem cells to assist in finding ways to enhance the miracle of neural regeneration, including using genetics to repair and regenerate existing neurons rather than creating new ones through stem cells.
According to Science Daily, one 2016 study found a way to switch on the repair mode in helper cells to assist in the restoration of injured axons, which are the part of neurons that transmit signals. This change occurred through reprogramming the gene regulation of the cells, allowing for the existing cells to once again regain function to transport signals in the nervous system.
Another study published in 2018 from the University of California, San Diego, discovered a genetic pathway that may hold the key to repairing damaged axons (the part of the nerve cell that transmits impulses from one cell to the next), as long as they are not completely dead. This gene plays a role in inhibiting axon regeneration, which could lead to an understanding of how to generate regrowth and repair of axons after injury. The knowledge of the specific gene could allow for treatment that targets this gene so that the normal repair cycle can be switched back on when neurons are damaged.
With these studies and similar ones, future treatments may be able to focus on turning on or off certain genes to allow for injured or damaged neurons to repair themselves without the need for replacing the neurons with new ones, whether created from stem cells or from other methods of neurogenesis.
The Outlook for Innovative Treatments
Humans have limited capacity for natural neural regeneration, but researchers are on the verge of developing treatments that will allow for neural regeneration, and thus healing brain injuries and neurodegenerative disorders. Much of the research remains in the animal and in vitro stages; however, there are promising studies pointing to the potential to use genetics, stem cells, and other methods to stimulate the nervous system’s own regenerative abilities.
So what does all of this mean outside of the world of neuroscience? Currently, experiencing a traumatic brain injury or a stroke could lead to lifelong paralysis or loss of function. A diagnosis of multiple sclerosis, Parkinson’s, Alzheimer’s, ALS, cerebral palsy, or any of the other neurodegenerative diseases is a life sentence, with doctors able to possibly slow down the progression.
Currently, millions of people around the world suffer from neurodegenerative disorders. According to the Harvard NeuroDiscovery Center, if nothing is done, it is estimated that more than 12 million Americans will have a neurodegenerative disorder in 30 years. These individuals and their families must slowly watch as they lose cognitive function and motor skills. Innovative treatments that can repair or regenerate neurons would mean that brain injuries and neurological disorders no longer need to come with this heartbreaking prognosis. Individuals would be able to live a fuller life, with some or maybe even all of their cognitive abilities and motor skills restored to normal.
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