By Natalie Nielsen
If anyone has healed from an injury causing a swollen limb or body part, then they have witnessed the lymphatic system at work. But what is the lymphatic system, and why do we care about it? The lymphatic system is a vasculature network, similar to blood vessels, found in almost every organ of the body (Image 1). These lymphatic vessels transport fluid and immune cells to draining lymph nodes, highlighting their importance in injury repair.
Even with basic understanding of the lymphatic system, it may come as a surprise that the heart is actually covered by a dense network of lymphatic vessels (Image 2)! Let’s further explore the role of lymphatics in cardiovascular health and disease.
The heart, like other organs of the body, maintains homeostasis by regulating fluid movement in an out of tissues, such that the organ does not become overly dehydrated or conversely develop swelling or edema (Image 3). The lymphatic system maintains a constant drainage of fluid that is leaked from capillaries and returns it back into blood circulation. However, when an injury occurs in an organ, such as when heart tissue becomes damaged during a heart attack, fluid regulation becomes unbalanced and the tissue becomes swollen, or edematous. In fact, in almost every cardiovascular disease or surgery, the heart develops edema. There have even been reports that following cardiac transplantation surgery, the heart becomes so swollen that the doctors must wait for the swelling to subside before closing the patient’s chest! This is where the lymphatics around the heart, called cardiac lymphatics, come into play. Their job is to help drain excess fluid in the heart to return it back to normal.
Only recently have the therapeutic potential for cardiac lymphatics been studied. In animal studies, a drug that promotes the growth and function of cardiac lymphatics significantly improved the function of the heart following a heart attack! Because heart tissue does not regenerate, the selective manipulation of cardiac lymphatics offers an alternative route to improve health outcomes in these patients. With further research into lymphatics, there is no telling what other benefits and therapies may arise!
