There was a time not that long ago when the regeneration of human body parts including limb regeneration was in the realms of science fiction exclusively. However, as of today, this is very much the part of scientific literature and the question of when not if this is possible.
The great news is great scientific advancements have been made in the understanding of the regeneration of limbs and body parts in the natural world where it is very common.
One such creature in nature is the African Lungfish, which can regrow its fins and tail after being attacked by predators. It can do this as effectively as the salamander does.
Lungfish Tail Regeneration
The amazing regeneration abilities of the lungfish reveal that these characteristics originate from a common vertebrate ancestor based on a recent study.
If scientists could understand the molecular mechanics that crystalize this phenomenon that allowed the regrowth of body parts, it could allow new developments of technologies in human tissue engineering. Indeed, paving the way to cure spinal cord injuries for example.
A study by the evolutionary biologist Igor Schneider with his research team, which was published in the Proceedings of the Royal Society B: Biological Sciences, explores tail regeneration in the African lungfish for the first time. This work reveals that the regenerative abilities in the lungfish share common themes as the regeneration of tails in salamanders.
This research shows that these traits of regeneration are likely to have come from a common ancestor and give new groundbreaking areas of research. Since it will allow better insights into understanding human limb regrowth and we as a species are also vertebrates.
An interesting study shows that the extinct fish called Elpisostege watsoni, actually had finger bones in the pectoral fins and reveals how human digits evolved before vertebrates came out of the water onto the land.
The lungfish is our closest relative in the water today and relate to us in many ways especially how their fins which is the equivalent to the bones of our limbs. They also require air to breath and will drown otherwise and have lungs that operate like ours.
Regrowing a Limb
Limb Regeneration is an extremely complex process. Muscles, bones and the vertebrate and spinal cord requires to be created cell to cell. The cells must migrate to the point of injury where the limb was lost, and need to multiply until the tail has regrown in about three weeks.
There are immune cells called macrophages that will travel to the wounded area which are part of this regeneration process. It is interesting since these cells cover a large area of both the lungfish and salamander regeneration.
In the article above about macrophage cells, the Australian scientists showed than when a drug was used to stop these immune cells it shut down the Axolotl’s ability to regenerate its lost limbs and ended us scarring (Fibrosis) like humans.
It is compelling, to say the least as these immune cells are also present in humans and eliminate pathogens and trigger healing by removing anti-inflammatory and inflammatory signals being sent to the brain.
Regeneration in Humans
There has been a great deal of progress achieved in discovering what occurs when a lost limb is regrown. The bio-electric and biological mechanics behind limb regeneration are being understood.
What is needed to be fully demystified is the question of whether the common genetic ancestry that is shared between humans, with the lungfish and salamanders could also regenerate. To find this out scientists looked phylogenetically for any relatives containing regenerative traits that are similar in nature.
Researchers see the lungfish as unique since they are our closest cousins when it comes to the fish family. So it is prudent with the lungfish’s ability to regrow its tail, to explore if there is any regenerative presence in our common genetic ancestry.
They actually have an ideal regenerative model to research if human body parts can be regrown for a number of reasons. For instance, they do have the right kind of anatomy to study according to Schneider and his team, and is a species that can easily be managed in the laboratory.
In fact, the lungfish are even more closely related to us than other common creatures in nature that I have discussed on this website who possess powerful mechanisms of regeneration.
The fins of lungfish contain a humerus which is like the bone in the upper arm of a human. I also mentioned earlier that they have lungs like ours and will drown if they don’t take in air.
The scientists in this study say that the lungfish has a cocktail of various characteristics that indicates it is even more closely related to humans than the zebrafish that I wrote up about.
Like the Axolotl, the genome of the lungfish is enormous, as much as 40 times bigger than a human. This is because its genome has a large number of transposons (or jumping genes) which are virus-derived DNA elements.
Under the process of regeneration some of these genes are switched on, but it is not known if the reason they get activated is due to being close to other key genes or if they are playing an active role in regeneration.
Are these genes that get activated really essential to regeneration? This is a question that scientists are aiming to answer. The work of Schneider would suggest that perhaps there could be a way to rearrange the human genes allowing powerful human regeneration abilities.
What has been learned?
There are many genes used in regeneration and these also exist in embryonic development. The researchers findings show that the lack of regeneration in humans is not so much in lacking the genes that are necessary, but the inability to activating genes that we have in the correct time and sequence.
What the scientists learned is the West African lungfish not only is able to fully regrow its tail but in addition, the regeneration that occurs is using a similar molecular mechanism to limb regrowth in amphibians like the Axolotl.
A signaling gene exists known as SHH and plays a critical factor in sending instructions to the brain for producing a protein called the Sonic Hedgehog. It plays a key role in the organization and development of the limbs, spinal cord, and brain, and other parts of the body during the embryonic stage.
This shows a hypothesis that this form of regeneration occurred in a common ancestor of these species, and also of us humans. We certainly do not look like a lungfish but its tail and fins possess the same bone, nerve tissue, and muscle that are found in our legs and arms.
While we are the same as in being both vertebrates having a spinal cord, however, the big difference is that the spinal cord of the lungfish will grow back when it regrows its tail. In contrast, humans with a damaged spinal cord is a life-changing event and the injury is permanent.
If we could unlock the secrets of how the lungfish achieves spinal cord regeneration it would create a revolution in healthcare with new innovative treatments of spinal injuries and make paralysis for example an era of the dark ages.
Human Regeneration Insights
Schneider feels by learning how the lungfish achieve their amazing feats of spine and tail regeneration, could mean having a better understanding of why humans are unable to repair spine cord injuries. In the future, we will create new methods to initiate a restorative repair of the tissues in the spinal cord.
Studying the mechanisms of regeneration in multiple species with help in understanding the key genetic signals that will act as a jumping board for human regeneration. Since when discovering the initial signals then it means we can develop techniques to fire-up the signaling pathways in people.
So what does this research say for limb regeneration for humans? Well, deeper clarification of how regrowing limbs in the lungfish and other species like the salamander, can open up a new revolution of treatments for burns, spinal cord regeneration for paralysis and novel new treatments for amputees to get them on a more regenerative pathway.
Scientists are wanting to figure out the ancestral library of regenerative genetic instructions that is being tapped into by these creatures for regrowing of lost body parts.
When researchers understand this regenerative instruction set then they can single out what parts of that genetic library of regeneration that is no longer in humans.
Or the DNA sequences that remain dormant and what can be enabled. This could be a set of instructions that can be genetically inserted.
I really think that nano-technologies can go a long way in the revolution of regeneration based on what scientists are working on here that could help in reproducing that toolkit at the cellular level.
I will certainly be writing up new articles that further explore nanochip technologies that are going to create a revolution for getting the patient on a better path of regeneration and repairing damaged tissues.