Fibrin is a filamentous protein that helps repair blood vessels and skin tissue in hemorrhagic wounds. It is produced in the blood in the event of injury from another protein: fibrinogen. Explanations.

Fibrin is a filamentous protein, that is to say a long protein in the form of a filament. It is produced from a plasma protein: fibrinogen (itself synthesized by the liver) during the phenomenon of blood coagulation.

As a reminder, coagulation is the process by which a blood clot is formed in the event of damage to the blood vessels. When the permeability of blood vessels is compromised, fibrin acts as a restraining mesh on the clump of red blood cells and blood platelets. It thus consolidates the clot which stops the loss of blood.

In the event of a wound causing bleeding, the fibrin therefore contributes in the first place to stop the latter. After this first phase, the vessels let out by oozing the exudate. This fluid (composed of antibodies and other proteins involved in tissue repair) provides defense against infection and wound cleansing. It contains in particular fibrin which promotes the migration of fibroblasts and endothelial cells to repair the skin lesion during the healing phase.

Fibrin, essential for coagulation

When an injury, a shock or a medical-surgical intervention causes the rupture of a blood vessel, a hemorrhage occurs. Hemostasis includes all the phenomena that allow bleeding to stop.

First of all the primary hemostasis results in the platelet aggregate (the platelets agglutinate at the edge of the wound to form a platelet nail intended to obstruct the breach). This phase is triggered when the blood platelets come into contact with the lesion of the vascular tissue.

Then, plasma coagulation triggers a cascade reaction that activates several enzyme molecules (called “coagulation factors”). Among the latter, the enzyme prothrombin is predominant. The active form of prothrombin is called thrombin. This converts fibrinogen (a soluble protein in the blood) into an insoluble protein: fibrin. The fibrin induces gelation of the blood at the level of the lesion. The fibrin filaments act as a containment sheath on the platelet aggregate. A stable clot forms which both stops the bleeding and restores the lining of the blood vessel.

Finally, fibrinolysis occurs once the bleeding has stopped. It leads to the dissolution of the fibrin clot. It is triggered by the action of new enzymes such as plasmin which degrade fibrin.

Fibrin, protection for the wound

A protective film

Fibrin fibers form a protective film for the blood clot produced by coagulation. The fibrin fibers reorganize their structure into a sheet-like film on the surface where the clot comes in contact with air. According to a 2018 study, this film would have “breathability” properties that allow air to reach the wound through tiny pores. These would act as a protective filter against viruses and bacteria for a few hours. This would give the immune system time to recruit white blood cells to counter the infection.

Optimization of inflammation

In the event of a wound, the repair phase of the blood vessel is accompanied by an inflammatory phase. The increased capillary permeability promotes the passage of blood plasma rich in antibodies, leukocytes and macrophages to the traumatized region. Necrotic tissue, foreign bodies and microbes are eliminated by phagocytosis and proteolysis. Fibrin, thanks to its chemotactic properties, will optimize this process by attracting white blood cells to the inflammatory site.

Action on tissue repair

The exudate is a fluid similar in composition to that of blood plasma, which oozes from the capillaries at the lesion site. It is loaded with cells, antibodies and proteins like fibrin and contributes to the first step in tissue healing: budding.

Budding aims to fill loss of substance by new fabrics. Fibroblasts (connective tissue support cells) produce mucopolysaccharides (which make the wound appear moist and mucous) which will serve as a matrix for building collagen fibers in connective tissue. At this stage, fibrin is used for the migration of fibroblasts and endothelial cells to repair the lesion.

The so-called epithelialization phase marks the end of healing. It results from the formation of new epidermal cells by mitosis (cell division). This process begins at the edges of the wound moving towards the center.

Action on the wound

A wound may present with fibrin. It looks like white or yellowish filaments. Fibrin promotes the process of tissue reconstruction. However, too much fibrin in the wound can delay the healing process.

Debridement (or debridement) care is required in the event of a necrotic or fibrinous wound. It consists in removing the debris (dead tissue, coagulated blood, fibrin, etc.) which clutter the bottom of the wound and prevent healing. It is an essential prerequisite for healing. This care can consist of the mechanical extraction of debris (using an accessory such as a curette), cleaning with water or physiological serum, moistening the wound by applying dressings, etc.

Treat a non-serious wound

When a wound is shallow and / or when there is little bleeding, the coagulation mechanisms take place spontaneously and without difficulty. It is recommended :

• Cleanse the wound with soapy water or physiological serum then apply an antiseptic lotion;
• Remove any contamination with clean tweezers;
• Leave the wound in the open, if it is superficial;
• Apply a bandage, if it is slightly deeper. It is also possible to use adhesive strips. These protections are to be applied within 5 hours after the moment when the lesion is formed;
• Check the status of your tetanus vaccination (in adults, reminders are to be carried out every 20 years). If you are not up to date, see a doctor.

Treat a serious wound

Certain injuries should prompt you to seek urgent medical attention:

• Deep wounds. Do not apply anything other than an antiseptic spray while waiting for help;
• Injuries caused by a thin and / or pointed object (for example: a nail);
• A bite.

If the bleeding is profuse :

• In this case, you can practice manual compression while waiting for help to arrive;
• If the wound is bleeding heavily or heavily, compress the wound with a sterile compress or clean cloth. Lift the squeeze every 10 minutes, while waiting for help to arrive. Do not perform a tourniquet;
• If general signs are associated: fever, pallor, malaise, dizziness, etc.