This might look a bit like a fish net, but what’s actually caught in this image is the structure of the endothelium—the thin layer of cells lining your blood vessels that controls the flow of molecules in and out of the bloodstream. The red lines are the actin filaments that give each endothelial cell its shape, while the purple are proteins called cadherins.
Most of the time, the actin “ropes” and cadherin “glue” act together to form a tight seal between endothelial cells, ensuring that nothing leaks out of blood vessels into surrounding tissue. However, when endothelial cells sense an infection or an injury, the cadherins open gaps that allow various disease-fighting or healing factors or cells present in the blood to breach the barrier and enter infected or injured tissue. After the infection subsides or wound heals, the gaps close and the blood vessel is once again impenetrable.
The creators of this image, which is featured in NIH’s Life:Magnified exhibit, are Christopher Carman and Roberta Martinelli, who are cell biologists at Harvard Medical School in Boston. The duo studies what happens when the endothelial seal weakens and blood vessels begin to get leaky. For example, if vessels leak inappropriately, excessive fluid and immune cells can seep into the tissues, triggering harmful inflammation and swelling. This occurs during septic shock, as well as in cardiovascular disease, diabetes, cancer, arthritis, and many infectious diseases, including the scary disease that has garnered a great deal of attention in the last few weeks: Ebola virus disease.
By studying how the endothelial seal is normally regulated, Carman and his colleagues are helping to build the foundation of knowledge needed to develop therapies that will keep blood vessels from leaking at the wrong times. To date, they have one drug (that is already FDA approved for a different use) that they are testing in animal models for use in septic shock. If successful, they hope to expand these trials to a much broader range of conditions in which leaky vessels occur.
“Life: Magnified” Online (NIH)
NIH support: National Heart, Lung, and Blood Institute; National Institute of General Medical Sciences