Researchers recently discovered that humans used to have the ability to regenerate damaged sensory organs like the eyes, similar to fish or reptiles. However, during human evolution, genomes that could help revive parts like the eyes have been “turned off”.
Essentially, eye injury, and more specifically retinal damage, is the leading cause of blindness in humans worldwide. The treatment of eye injuries is not straightforward, as the structure and mechanism of action of this sensory organ are complex, with a series of cones and rods that receive and transmit light data. central nervous system.
This is why humans are unable to regenerate retinal tissue, similar to the way we do it with other damaged tissues, such as skin or bones.
According to experts at Johns Hopkins University (USA), the ability to regenerate damaged organs like the eye is already in human genes, but has been ‘turned off’ during evolution.
Meanwhile, some animals possess an amazing ability to regenerate this type of tissue, such as zebrafish. Even if a zebrafish has heart damage, it will immediately regenerate a new one instead. Specifically, according to some studies, zebrafish can regenerate 20% of heart muscle destroyed in just two months. These are remarkable discoveries, when zebrafish genes are quite similar to human genes, reaching a rate of about 70%.
According to expert Seth Blackshaw at Johns Hopkins University (USA), the ability to regenerate damaged organs is already in the bodies of many animals, including humans. However, this ability has disappeared in humans during evolution.
“Our research shows that regeneration has existed in mammals, including humans, but some evolutionary pressures have made that ability disappear,” says Blackshaw. said.
The trade-offs in human evolution
Basically, when we are still in the womb, the retina forms as an extension of the outward growing brain and the central nervous system reaching behind our eyes. In the retina, Müller glial cells act as a protective film of the eye, cleaning neurotransmitters and various debris in the eye, and activating an immune response when needed.
In some animals, such as fish and reptiles, these Müller cells also regenerate nerve cells that transmit light signals received from the eye to the brain for processing.
Some animals possess an amazing ability to regenerate this tissue, such as the zebrafish, which has the ability to regenerate retinal tissue.
To further examine the ‘regeneration’ mechanism in some animals, researcher Thanh Hoang and colleagues from Johns Hopkins University examined genes found in the cells of zebrafish and chickens. and mice, as well as monitoring how they respond to retinal damage.
As expected, these genes trigger an immune response, helping to clean damaged tissue and fend off impending infection. However, in the cells of some mammals, such as mice, a ‘network’ in the body suppresses the activation of these genes, just before they can begin to change into re-cells. born as in other mammals.
Then, by looking at the mechanisms that govern cells, the researchers were able to stimulate the cells to begin regenerating retinal neurons in adult mice, after they suffered trauma. in the eye.
The genome of the human ancestor may once have possessed the ability to ‘regenerate’, before experiencing some evolutionary pressure that made that ability disappear.
The results of the experiment have led researchers to suspect that the loss of the ability to reproduce by humans could be an evolutionary trade-off.
Accordingly, mammals, including humans, have accepted to lose the ability to regenerate tissue in exchange for better resistance to parasites.
“We know that some viruses, bacteria and even parasites can affect the brain. This would be catastrophic if infected brain cells could grow and spread through the system.” Nervousness, “explains expert Blackshaw.
Although the work of the Johns Hopkins University scientists still requires further research, the study itself opens a glimmer of hope in the treatment of eye damage for the visually impaired around the world.
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