AGING AND THE LYMPHATIC SYSTEM
AGING: A WHOLE-BODY EFFECT 
Aging is typically defined as the process of growing old. The vague definition of the process has been further explained as the body’s functional decline over time that results from a multitude of changes that occur in the body that affect:
· Hormone production
· The skin
· Sleep patterns
· Bones, muscles, and joints
· The breasts
· The face
· The reproductive organs
· The heart and blood vessels
· The kidneys
· The lungs
· The nervous system
The body is made up of trillions of cells. Clusters of cells that perform similar functions form tissues and tissues make up organs. As we age our cells can change in size, shape and function. Therefore, our tissues and organs change as well. These can be generally explained by looking at the changes that occur over time in the various tissues of the body and the chemical processes that tell them who they are and what to do. Some of these changes are listed below: [1&2]
a) Cells become less able to divide and multiply or they can multiply too often.
b) Connective tissue becomes stiffer, or its elasticity is lost.
c) The consistency of tissue changes to become more fatty in nature.
d) Cell membranes change which decreases its ability to get oxygen and nutrients and remove waste products.
e) Cells shrink. If enough cells decrease in size, the organ that they make up gets smaller (known as atrophy). It can occur in any tissue that occurs as we age as seen in the decline of muscle mass, bone density, and in some lymph nodes in the body.
f) Cells can also become bigger in size to compensate for a decrease in the number of cells, they can become misshapen or disorganized.
g) Older cells (known as senescent cells) can cause aging in nearby younger cells through channels of communication between them.
h) Changes in a cell’s energy center occur and with a low battery-like condition they cannot do the job they need to do efficiently.
i) Cells that are responsible for replenishing the body’s tissues (stem cells) become less effective (known as stem cell exhaustion).
j) There are less hormones, proteins and chemicals produced that are responsible for recognizing and signaling the removal of old cells, damaged proteins, or infectious agents.
HOW DOES AGING AFFECT THE LYMPHATIC VESSELS AND ITS IMMUNE FUNCTION?
Structural changes that occur with aging
a) Muscles within the lymphatic collector walls [5&6]
The lymphatic system is a one-way system that drains fluid, proteins, wastes, potentially harmful agents and fats from tissues and organs in the body and essentially sterilizes it upon passage through the lymph nodes before it returns the fluid back to the venous system. Unlike the circulatory system, it does not have a heart to pump lymph through its vessels. Looking at how it is formed, the larger lymphatic vessels are like veins in that they have sections that are divided by valves. The valves prevent backflow of lymph fluid. The larger lymphatic vessels have a muscle layer that can contract to move lymph fluid through the system. Muscle cells run lengthwise along the vessels and are also in a circular formation at the valves. The muscle layer is sensitive to many chemicals, nerve impulses and pressure from increased amounts of fluid that induce muscle contractions. Researchers have found that the muscle walls of lymphatic vessels become thinner and the number of muscle cells decreases. Therefore, the contraction strength and rate is affected and the valves are less able to close properly. This can cause slowing of fluid transport and a backflow and congestion of fluid in the lymphatic system. Another important factor to consider is that the nerve fibers, and the amount of chemicals and hormones that stimulate contraction are less available as we age and thus contractions of the muscle walls become less frequent moving fluid through slower.
b) Thinning of lymphatic vessel walls 
The inner lining of the lymphatic vessels normally functions to accept fluid, proteins, wastes, fats and potentially harmful agents and will not allow these substances to escape. It acts as a barrier to keep these substances within and moving through the lymphatic system. However, with age, this barrier layer thins and can allow fluid or other substances to leak back out into the tissue spaces. This can potentially cause fluid build-up, inflammation, or infection in the surrounding spaces if the body is not able to respond effectively.
At rest, these changes can cause a mild edema, but add in a traumatic event, other disease processes such as obesity or diabetes, radiation exposure or chronic inflammation, all of which damage or increase the work of the lymphatic system, the lymphatic system can become overwhelmed to cause lymphedema.
c) Lymph node degeneration (atrophy) 
It has been reported that some lymph nodes in the body will lose their ability to house immune cells which creates an added potential for a loss of the ability to fight infection and disease in aged adults. Changes in the structure of the lymph node include replacement of lymph tissue that houses T and B cells responsible for immune function by fibrous, scar-like tissue and fatty tissue. These changes also interfere with fluid reabsorption from the lymph node and can cause lymph fluid congestion. The study by Hadamitzky et al. (2010) showed fibrous changes starting before the age of thirty with increasing degeneration throughout the lifespan, the most severe changes seen in people over seventy-five.
Chemical and hormonal changes in the body [1-7]
There are thousands of chemicals, hormones and elements that the body produces to keep it in healthy working order. Sodium, calcium and potassium are needed for lymphatic muscle contraction, certain hormones are required for nerve conduction that helps regulates lymph muscle contraction and chemicals that are released to initiate inflammation and healing are all affected by the effects of aging in the body. A decrease in or overproduction of these substances can create increased edema, chronic inflammation and lymphatic vessel damage leading to chronic edema and lymphedema.
CAN WE REVERSE SOME OF THESE CHANGES?
Recent research is pointing to changes that occur to our DNA over time that cause age related changes to the body. Researchers are just at the tip of learning the mechanisms of how these changes occur and what factors are involved in these changes
SOME OF THE FACTORS THAT RESEARCHERS ARE LOOKING INTO THAT MAY INFLUENCE THE AGING PROCESS OF THE CELLS IN OUR BODY.
1) Diet and nutrient signaling pathways in the body
2) Geographical location
3) Exposure to toxins
4) Sun exposure
5) Effects of free radicals
6) Effects of inflammation (called inflammaging)
Changes that occur to the lymphatic system vessels and lymph nodes affect its ability to move fluid through and provide a robust immune response as we age. There are many factors that contribute to the degeneration that occurs with age to affect our lymphatic system, many of which are still to be discovered. Reversal of what has already been started is being research today.
The things we can do to help our lymphatic system based on my research for this blog may include:
1. Keep moving: Exercise is very important for balance, heart and circulatory health as we age, but since lymph fluid movement is also aided by muscle contraction, we need to move our body in order to supplement its flow and counteract the loss of lymphatic vessel muscle function.
2. Eating well: Providing your body with nutrients and vitamins from food will help support cell functions in the body. Studies are ongoing as to the effects of genetically modified food, chemical additives and highly processed foods on the body’s function. Intermittent fasting has been a hot topic lately and researchers are looking at it for its beneficial effects on cellular DNA resetting and how that effects changes associated with aging.  Other research on nutrition is looking into the chronic inflammation associated with lymphatic disruption and lymphedema. Anti-inflammatory diets have been suggested. See Jean LaMantia’s website for more information about diet and lymphedema.
3. Help prevent illnesses: Infection such as cellullitis can be a complication of leaky lymphatic vessel walls. Swelling, Heat, Angry looking Redness and Pain (S.H.A.R.P) are all signs that you need to see your medical professional. If you get a cut or a scratch, clean it well with soap and water and if the skin is open cover it with a bandage. You may also want to apply an anti-bacterial ointment. See my blog on skin infections and lymphedema. Aging also decreases the number of immune fighting cells in our bodies. When out in public, wash your hands or use hand sanitizer, try not to touch your face or mouth, stay away from other people who are coughing, cover your own cough to protect others and in these times of Covid-19, wear a face covering/mask.
4. Safe-guard your skin lymphatics: Over time, exposure to the skin by ultraviolet light from the sun can damage the skin and its underlying lymphatics. Use paraben free sunscreen and clothing that covers your face and skin while in the sun and seek the shade to enjoy your outdoor experience.
5. Other: as your connective tissue in the body becomes stiffer or loses its ability to replace itself with time, it is important to remember that: drinking plenty of water helps to keep our tissues from becoming dehydrated, building of our bones is helped with weight bearing exercise and mental acuity and cognition can be helped by brain stimulating activities (watch for this blog in future).
There is much we do not know about how the world we live in affects our cells or how a variety of complex changes occur as we go through life to cause the effects of aging. Research on aging and the lymphatic system is emerging, but there is still much to learn.
1. Aging changes in organs, tissues, and cells: https://medlineplus.gov/ency/article/004012.htm
2. Lopez-Otin, C., Blasco, M., Partridge, L., Serrano, M., Kroemer, G. (2013). The Hallmarks of Aging. Cell, 153. 1194-1217
3. Wittlinger, H., et al (2011). Dr. Vodder’s Manual Lymph Drainage: a practical guide. Thieme. NY:NY
4. Scallan, J. et al. (2016). Lymphatic pumping: mechanics, mechanisms and malfunction. Journal of Physiology, 594-20. Pp 5749-5768. DOI: 10.1113/JP272088
5. Shang, T., Liang, j., Kapron, C.,M., Liu, J. (2019) Pathophysiology of aged lymphatic vessels. Aging 11(16). 6602-6613. Aging Cell, 14. 582-584. DOI: 10.1111/acel.12330
6. Zolla, V., et al. (2015). Aging-related anatomical and biochemical changes in lymphatic collectors impair lymph transport, fluid homeostatis, and pathogen clearance.
7. Hadamitzky, C., Spohr, H., Debertin, A., Guddat, S., Tsokos, M., Pabst, R. (2010). Age- dependent histoarchitectural changes in human lymph nodes: an underestimated process with clinical relevance? Journal of Anatomy, 216. Pg.556-562. DOI: 10.111/j.1469- 7580.2010.01213.x