The skin is an organ that protects us from the outside world. On 1 cm3, there are 3 blood vessels, 12 nerves, 100 glands that allow us to sweat and emit pheromones, 10 hairs with 15 glands associated with them and 3 million cells.
Diagram of skin layers
Over the course of its life, our skin suffers from different types of attacks. Injuries, bacterial attacks, reactions related to drugs, diseases such as psoriasis or a neuropsychological impact ...
In the event of an injury, foreign organisms that are dangerous to our health can enter it (bacteria, viruses). The skin of a healthy individual heals on its own. However, if the wound is large and deep in an adult mammal, like us, it can cause a scar.
Research on technologies allowing better healing, even unmarked healing, is very active. This area is not just for aesthetic purposes, although it does have a definite impact on the psychological state in the long run. Indeed, a visible scar, especially on the face, can lead to social stigma, a drop in self-esteem, a disruption of daily activities, but also anxiety and / or depression. The scar can also be physically painful. The skin is then lifted and stretched in this area, with a different color.
How is a scar formed?
Wound healing is well described and known from the point of view of molecules and cells. It comes in 3 stages: inflammation, proliferation and remodeling.
Diagram of the 3 main stages of healing
At first, a fairly deep wound will cut and create a breach in our skin. In order to prevent the immediate emptying of our blood, our blood vessels will contract to reduce its passage and evacuation from our body. It's vasoconstriction. Platelets, which until now circulated quietly in the middle of our red blood cells, will be called upon with a protein, fibrin, to plug the breach. The platelets act like glue and the fibrin, fiberglass, to consolidate. This stage corresponds to inflammation.
This plug remains fragile all the same. The blood vessels will then "reopen" to allow the delivery of reinforcements and thus make healing possible. It's vasodilation. Coagulation can then begin. This is the stage when the stopper is tight, the bleeding has stopped, thanks to different types of cells and molecules. It is then the turn of cleaning: the debris of the cells, which have been destroyed / or damaged, will be eaten just like the viruses and bacteria which had taken the opportunity to try to enter.
This is followed by the proliferation phase which takes place 2 to 10 days after the incident. New skin begins to form. It is important to distinguish a type of cell that has a key role at this stage, the fibroblasts. They are the ones who will produce a protein called collagen. This protein is widely used, especially in cosmetic products or even in cosmetic surgery. And for good reason, just in our case here, it occupies a prominent place. Collagen makes up 80 to 90% of the composition of a scar (its impact on the body is not limited to that). At this stage, the surface of the skin is very contracted. Over time, the scar becomes thinner and firmer, less red too, this is the reshaping. It can last a few months or over a year.
Healing does not always go as planned
Control of its formation is extremely important for patients with hypertrophy, keloids, the elderly or diabetics, for whom the outcome can be fatal.
Photograph of hypertophic scar (A) and scarring with keloids (B) (Source: doi: 10.1089 / wound.2016.0696)
Hypertrophic scars are scars remaining in the area of injury. They can decrease over time. They are nonetheless large and painful and contain organized collagen. Keloids, on the other hand, are excessive scarring that spreads outside the area of injury. They are large, sore and protruding with disorganized collagen. Concerning the elderly, there is a decrease in the effectiveness of the healing agents, which can cause infections or diseases.
New technologies are emerging
In order to overcome these problems, various solutions are put in place. First, preventive elements with relief of skin tension, hydrating scars, bandages and compression garments.
Regarding future technologies, it has been observed in fetuses (up to 24 weeks) and some animals (fish, frog, salamander, etc.) that scar-free healing is possible. This is due to the difference in the amount of wound healing agents.
Work is underway with stem cells, but also with fish skin. This can be a good alternative to skin grafting in the future. Indeed, a transplant still has a risk of being rejected even 25 years later. Fish skin mitigates this risk. There is little chance of getting an infection or illness. It is also profitable and natural. To be transplanted all its cells must be removed. Fish skin dressings are also possible. Finally, with the advent of 3D printing which is taking more and more place in biology, the printing of organs and skin is booming.
Several tools in development are promising and perhaps one day will no longer have a scar. This is not just an aesthetic whim, for some it can be real physical and / or mental suffering.
1. Afifah, A., Suparno, O., Haditjaroko, L. & Tarman, K. Utilisation of fish skin waste as a collagen wound dressing on burn injuries: a mini review. IOP Conf. Ser.: Earth Environ. Sci. 335, 012031 (2019).
2. Barroux, G. Lorsque Tremblay et Réaumur parlaient de « régénération ». Med Sci (Paris) 19, 761–762 (2003).
3. Boismal, F. et al. Vieillissement cutané - Physiopathologie et thérapies innovantes. Med Sci (Paris) 36, 1163–1172 (2020).
4. Davidson, J. M. Can Scarring Be Turned Off? The American Journal of Pathology 176, 1588–1591 (2010).
5. Dubertret, L. La peau. Med Sci (Paris) 22, 100–101 (2006).
6. Erickson, J. R. & Echeverri, K. Learning from regeneration research organisms: The circuitous road to scar free wound healing. Dev Biol 433, 144–154 (2018).
7. Fiakos, G., Kuang, Z. & Lo, E. Improved skin regeneration with acellular fish skin grafts. Engineered Regeneration 1, 95–101 (2020).
8. Fruleux, A. & Boudaoud, A. Les forces qui maintiennent l’ordre parmi les cellules. Med Sci (Paris) 35, 735–738 (2019).
9. Marshall, C. D. et al. Cutaneous Scarring: Basic Science, Current Treatments, and Future Directions. Adv Wound Care (New Rochelle) 7, 29–45 (2018).
10.Monstrey, S. et al. Updated Scar Management Practical Guidelines: Non-invasive and invasive measures. Journal of Plastic, Reconstructive & Aesthetic Surgery 67, 1017–1025 (2014).
11.Ogawa, R. Recent Advances in Scar Biology. Int J Mol Sci 19, (2018).
12.Su, C. W., Alizadeh, K., Boddie, A. & Lee, R. C. The Problem Scar. Clinics in Plastic Surgery 25, 451–465 (1998).