A recent study published in The Lancet points to the importance of endothelial cells in the progression of Covid-19 infections. Healthy endothelial cells are tightly woven together and sometimes look like bricks under a microscope. Endothelial cells are found all over the body including your mouth, nose, lungs, blood vessels, and major organs. Covid-19 can enter endothelial cells. Covid-19 infection of blood vessel cells could explain why individuals with Covid-19 sometimes suffer from heart attacks, strokes, and blood clots.
Covid-19 enters endothelial cells in the mouth or nose and can travel to the lungs where it continues to infect cells. By design, lung tissue is surrounded by small blood vessels to move oxygen to the bloodstream to feed every organ in your body. Once Covid-19 enters your blood vessels, several problems can develop.
1) Damaged endothelial cells signal immune response. The immune system is programmed to bring fighter cells to clean up damaged tissue. With immune cells comes increased circulation, more fluid, and inflammation. Too much of a good thing, your immune response, can increase fluid accumulation in the lungs and damage the structure of the blood vessels.
2) Infection of endothelial cells makes the tight junctions between cells leaky. This allows fluid from the blood to leave the blood vessels and enter the lungs. Fluid in the lungs makes air exchange really difficult.
3) Damaged blood vessels try to repair themselves. In this process, they create “band aids” made of blood clots. Blood clots stimulate a blood clotting cascade. If this cascade is over-stimulated or left unchecked, blood clots can form and/or travel to vessels that feed oxygen to vital organs. This is really bad.
Now for some good news! Understanding this process allows for the trial of treatments that can minimize these severe complications. Scientists are studying an arsenal of treatments that target specific steps in immune activation and blood clotting to improve symptom burden and survival of Covid-19 infection. Treatments to decrease severity of disease are incredibly important, especially in the absence of a current vaccine.