Red blood cells are largely considered to be free-flowing biconcave discs, unless they are involved in clotting, which is when they turn into many-sided closely-packed structures.
A blood clot is made up of fibrin, platelets and red blood cells. Researchers at the University of Pennsylvania found that during the clotting process, red blood cells change their shape to form a mesh of polyhedral structures.
Another finding, published in the journal Blood, was that contrary to expectations, fibrin and platelets made up the outside of the clot with the blood cells packed in the center.
After a clot is formed, the platelets initiate the contraction, a key step to creating a stiff and robust clot, and pull the red blood cells in to the center of the clot, which is how they form these never before seen shapes.
“We found that contracted blood clots develop a remarkable structure, with a meshwork of fibrin and platelet aggregates on the exterior of the clot and a close-packed, tessellated array of compressed polyhedral erythrocytes within,” said John W. Weisel, professor of cell and development biology at Penn.
This finding could be critical to understanding why clots formed in patients having a heart attack are resistant to being broken up. Agents like tPA are normally used to break up such clots. Understanding their structural landscape could help in targeted prevention of such closely packed clots forming.