Fibrin

What is fibrin?

Fibrin is a protein in your blood that plays a major role in stopping bleeding and aiding wound healing. It forms a mesh that stops blood flow. This sticky mesh allows platelets and other cells to cluster and form a blood clot that covers the wound.

Think of it like patching a hole in a wall. Fibrin is the adhesive mesh you put over the hole. Other cells (like platelets) are the putty you apply to the mesh. The mesh gives the putty something to hold onto, just like fibrin does for cells. Together, they cover the hole in the wall, or the hole in a blood vessel.

Fibrin helps protect you from losing too much blood. But several factors can affect the structure, density and stability of fibrin blood clots. This can impact your health and lead to issues like harmful blood clots (thrombosis).

What does fibrin do?

Fibrin has key roles, including:

• Stopping bleeding (hemostasis): Fibrin forms a mesh to create a stable clot. It seals the tear in a blood vessel to stop bleeding. Once the vessel is fully repaired, the fibrin mesh dissolves.
• Wound healing: Fibrin helps prevent infection by sealing injuries. It also draws in cells that aid the healing process. When your skin bleeds, fibrin (and other cells) eventually turns into a scab to protect the wound.
• Inflammation: Fibrin affects the inflammatory process. It can engage white blood cells and trigger your body to make cytokines. These cells are key parts of your body’s inflammatory and immune response. Sometimes, fibrin can trigger too much inflammation.
• New blood vessel growth (angiogenesis): Fibrin acts as the foundation for new blood vessels to grow. This could happen after an injury or because of inflammation.

Fibrin as a biomaterial

Healthcare providers sometimes use fibrin as a biomaterial. Biomaterials are natural or synthetic substances used for medical purposes. They support or replace damaged tissue.

As a biomaterial, fibrin acts as a natural supportive structure for tissue growth. Providers may use it to regenerate the following types of tissue:

• Bone and cartilage
• Heart and liver tissue
• Nerves
• Tendons and ligaments
• Skin

Where does fibrin come from?

Fibrin comes from fibrinogen, a blood protein. Your liver makes fibrinogen, and it flows in your blood plasma. When bleeding occurs, an enzyme called thrombin triggers fibrinogen to turn into fibrin.

Fibrin then acts to repair the wound. Once the injured blood vessel heals, your body breaks down fibrin. It turns into substances called fibrin degradation products (FDPs). They stay in your blood after a blood clot dissolves. Tests can also measure the level of FDPs in your blood.

What is fibrin made of?

Fibrin is made of long protein chains. Under a microscope, it looks like long strings or threads.

Fibrin is strong, sticky and elastic. These unique features allow it to trap platelets and other cells, forming a stable blood clot. Its flexibility allows the blood clot to stretch rather than break if it’s put under stress.

What conditions are related to fibrin issues?

Problems with fibrin happen because of issues with fibrinogen and/or thrombin levels. Gene changes can affect how these substances work in your body.

These issues can contribute to conditions like:

• Bleeding disorders: A lack of fibrinogen leads to a lack of fibrin. This can cause excessive bleeding.
• Blood clotting disorders: Dysfunctional fibrinogen or too much of it can cause either improper bleeding or clotting problems.

Certain medications, like heparin, can change how your body makes fibrinogen or thrombin, which affects your fibrin levels.